Ch 12- Spinal Cord

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the spinal cord is the connection between_

Information highway between brain and body

Where spinal cord is found?

Extends through vertebral canal from foramen magnum to L1 (1st lumbar vertebrae)

each pair of spinal nerves receives_(type of information) and issues_(type of signals) to_(2 locations)

Each pair of spinal nerves receives sensory information and issues motor signals to muscles and glands

Spinal cord is part of what system? spinal nerves is part of what system?

Spinal cord is a component of the Central Nervous System while the spinal nerves are part of the Peripheral Nervous System

the spinal cord is enclosed in_

vertebral column

spinal cord provides_(with respect to brain)

A two-way conduction pathway to and from the brain

the spinal cord is a major_center

major reflex center

how the spinal cord is a major reflex center?

spinal reflexes are initiated and completed at the spinal cord level

the spinal cord is protected by_(3)

bone, meninges, and cerebrospinal fluid

list the 3 meninges of the spinal cord

spinal duramater arachnoid pia mater

explain how the meninges protecting the spinal cord are found around it. include the name of the fluid that fills the spaces (2)

-spinal duramater is not attached to the bony walls of the vertebral column -between the bony vertebrae and spinal dura mater is an epidural space filled with soft padding of fat and a network of veins -Cereobrospinal fluid fills the subarachnoid space between arachnoid and pia mater meninges

list 3 major functions of spinal cord (3)

conduction locomotion reflexes

explain the "conduction" function of the spinal cord

bundles of fibers passing information up and down spinal cord

Explain the "locomotion" function of the spinal cord (2)

-repetitive, coordinated actions of several muscle groups -central pattern generators are pools of neurons providing control of flexors and extensors (walking)

Explain the "reflexes" function of the spinal cord (2, include who involves (3))

-involuntary, stereotyped responses to stimuli (remove hand from hot stove) -involves brain, spinal cord and peripheral nerves

Cylinder of nerve tissue within the _ (thick as a _)

-vertebral canal -finger

why the spinal cord arives up to L1? what is found after this point?

-vertebral column grows faster at fetal development so in an adult the spinal cord only extends to L1 -After L1 you have tracts (spinal nerve roots) that continue the spinal cord chasing their exit points inferiorly through the vertebral canal

_# pairs of spinal nerves arise from _ (4)regions of the cord

-31 -cervical, thoracic, lumbar and sacral

each cord segment gives arise to_(How many _nerves)

each cord segment gives rise to a pair of spinal nerves

within the spinal cord, we have_(2 regions of the spinal cord) enlargements. why and what kind of nerves get out of here? what causes this enlargement?

-Cervical and lumbar enlargements (because of the large amount of nerves) -this the the place where the nerves serving the upper and lower limbs arise -the ventral horns are larges in the limb-innervating cervical and lumbar regions of the cord and are responsible for the cord enlargement seen in those regions

the dural and arachnoid membranes extend to the level_, which is _of the spinal cord (position with respect)

-S2 -well beyond the end of the spinal cord because the spinal cord ends between L1 and L2

lumbar puncture (other name, where happens, what it is, and why done at that spot)

-or tap -happens within in the subarachnoid space within the meningeal sac, inferior to the level S2, -the subarchnoid space within the meningeal sac inferior to that point provides a nearly ideal spot for removing cerebrospinal fluid for testing, which is called lumbar puncture -because the spinal cord is absent there and the delicate nerve roots drift away from the point of needle of insertion, there is little or no danger of damaging the cord (or spinal roots) beyond L3

the spinal cord is part of the _

central nervous system

what part of the neuron conduct impulses?


what is the function of the nerves that go toward the brain? what is the function of the nerves that go away from the nerves?

sensory neurons go up motor neurons go down

what two spots reflexes can arrive?

-Reflexes go to spinal cord level or go to area of brain stem and then come out

_(type of information)goes into the brain. _(type of information) goes out of the brain

Sensory: goes into brain Motor=goes out of brain

what part of the spinal cord is the tapered tip of cord?

Conus medullaris

Conus medullaris (other name, location, and what it is)

-Medullary cone -inferiorly, spine cord terminates in this tapering cone-shaped structure

Cauda equinae (what are them, where found, and what resembles, fibers come out of_(location))

-the collection of nerve roots at the inferior end of the vertebral canal -is L2 to S5 nerve roots resemble horse’s tail -fibers come out of sacral portion of spinal nerves


-mixture of nerves, branchings -A nerve plexus is a plexus (branching network) of intersecting nerves

filum terminale (what it is made of, covered by what, where found, what does)

-terminal filament -a fibrous extension of the conus covered by pia mater, extends inferiorly from the conus medullaris to the coccyx, where it anchors the spinal cord so it is no jostled by body movements

sensory travels _

from body to brain

motor travels _

from brain to body

dorsal root ganglia (type of information it deals with)

sensory goes in, toward brain

the 3 meninges are _(what are made of) layers enclosing_

they are fibrous layers spinal cord

describe dura mater (what made of, surrounded by what and what surrounds)

-tough collagenous membrane surrounded by epidural space filled with fat and blood vessels

what is a use of the epidural space (medical procedure)

place where epidural anesthesia utilized during childbirth

describe arachnoid mater (made of what, what lines, consistency, filled with what?, what this creates, how looks like)

-layer of simple squamous epithelium lining dura mater and loose mesh of fibers filled with Cerebro Spinal Fluid ?(creates subarachnoid space) -looks like spider web

describe pia mater (how thick, attached to what, what anchor the cord (2))

-delicate membrane adherent to spinal cord -filium terminale and denticulate ligaments anchor the cord

what is the most superficial meninge?

dura mater

what is the toughest meninge?

dura mater

what is one function of dura mater?

protects spinal cord

list the order of meninges from most superficial to most deep

dura mater–>arachnoid mater–>pia mater

beside the subarachnoid space, what is other location in which cerebrospinal fluid is found? (within spinal cord)

central canal

what makes the spinal nerves? (2)

ventral nerve roots dorsal nerve roots

dorsal root ganglion is directed toward_ (posterior or anterior side)

the anterior side

denticular ligaments (how look, what meninge contains them, what do)

-saw-toothed shelves of pia mater that secure the spinal cord to the tough dura mater meninx through out its length

spinal nerves connect to the cord by_

paired roots

each nerve exist from the vertebral column by passing _and travels to_

-superior to its corresponding vertebra via the intervertebral foramen -the body region that it serves

how the nerves after the end of the vertebral column are found? include the 2 names of the spinal nerves

-the lumbar and spinal nerve roots angle sharply donward and travel inferiorly through the vertebral canal for some distance before reaching their intervertebral foramina

Spina bifida (how many babies get it out of how many, what it is, what is the most common manifestation and how it looks on the body, and how results, and involves what region)

-Congenital defect in 1 baby out of 1000 -Failure of vertebral arch to close covering spinal cord. -lamina and spinal process do not form, there is nothing holding meninges, and you end up having an expansion of meninges where you should have the arch -spina bifida cystica shows a saclike cyst that protrudes dorsally from the child’s spine. The cyst may contain meninges and cerebrospinal fluid or even portions of the spinal cord or spinal nerve roots -results from incomplete formation of the vertebral arches and typically involves the lumbosacral region

how can you try to avoid having spina bifida in your baby? (what reduces risk)

Folic acid (B vitamin) as part of a healthy diet for all women of childbearing age reduces risk

In Spinal Cord, central area of _ matter shaped like a _ and surrounded by _matter in _

-gray -butterfly -white -3 columns

gray matter (conformed of)

neuron cell bodies with little myelin

white matter is conformed of_

myelinated axons

all informaiton will travel through_matter

white matter

what is the function of gray commissure?

-connects right to left side of the gray matter

one function of cerebrospinal fluid is_

bring nutrients to the brain and spinal cord

gray matter is conformed of_(2) in spinal cord

-pair of dorsal or posterior horns -pair of ventral or anterior horns

Pair of dorsal or posterior horns

dorsal root of spinal nerve is totally sensory fibers

Pair of ventral or anterior horns

ventral root of spinal nerve is totally motor fibers

right and left side of gray matter is connected by_, which has in the middle_and is continuous with_ventricle

-Connected by gray commissure punctured by a central canal continuous above with 4th ventricle

ascending tracts are_. Descending tracts are_ (motor vs sensory)

-ascending tracts are sensory -descending tracts are motor

ganglia (conformed by, found in which system, have lots of_)

-lots of cell bodies–>"gang of cell bodies" -only found in peripheral nervous system -have lots of inner connection

other name of sensory nerves?


ventral root carries_ and other name is_

-motor information -efferent

gray matter will be divided into 3 areas which are_

ventral horn: anterior side posterior horn: posterior side lateral horn: middle

how many horns will send motor information within gray matter?

2 horns: Lateral horn and anterior ventral horn

Gray matter organization:
Dorsal half – _(2)
Ventral half – _(1)

-sensory roots and ganglia -motor roots

dorsal and ventral roots fuse_to form_

Dorsal and ventral roots fuse laterally to form spinal nerves

Four zones are evident within the gray matter – (include abbreviations)

-somatic sensory (SS) -visceral sensory (VS) -visceral motor (VM) -somatic motor (SM)

two grooves that mark the spinal cord surface are_. what they do?

-ventral (anterior) median fissure -and the shallower dorsal (posteior) median sulcus -these grooves run the length of the cord and partially divide it into right and left halves

lateral horns (who has them (2 spinal segments) and what are them)

-the thoracic and superior lumbar segments of the cord have an additional pair of gray matter columns beside the dorsal horns and ventral horns

all neurons whose cell bodies are in the spinal cord gray matter are_(structural type of neuron)


the somatic motor neurons of the ventral horns send their axons out to the _(location in body) via the_ that fuse together to become_

skeletal muscles (their effector orgnas) via the ventral rootlets that fuse together to become the ventral roots of the spinal cord

lateral horns consists mostly of the _( neurons)

cell bodies of autonomic (sympathetic division) motor neurons that serve visceral organs

afferent fibers carrying impulses _(from what part and from what root type)

-from peripheral sensory receptors from the dorsal roots of spinal cord

dorsal root ganglion (other name and definition (what contains))

-spinal ganglion -the cell bodies of the associated sensory neurons are found in this enlarged region of the dorsal root

after entering the cord, what are the routes that the axons can take? (2)

-after entering the cord, the axons of these neurons may take a number of routes -some enter the dorsal white matter of the cord directly and travel to synapse at higher cord or brain levels -Other synapse with interneurons in the dorsal horns of the spinal cord gray matter at their entry level

Describe the following about somatic sensory )SS=
1. location
2. Neuron
3. Information and from-to where

1. Posterior part of the dorsal horn 2. Somatic Sensory neuron 3. Interneurons receiving input form somatic sensory neurons of skin, joints, and muscles

Describe the following about visceral sensory
1. location
2. Neuron
3. Information and from-to where

1. Anterior part of the dorsal horn 2. Visceral sensory neuron 3. Interneurons receiving input form visceral sensory neuron, which is information coming from the organs of the body

Describe the following about visceral motor
1. location
2. Neuron
3. Information and from-to where
4. other name

1. originate in the lateral horn 2. Visceral motor neurons 3. Visceral motor (autonomic) neurons, in which information goes to organs 4. Visceral autonomic motor

Describe the following about Somatic motor
1. location
2. Neuron
3. Information and from-to where

1. originate in the anterior or ventral horn 2. Somatic motor neuron 3. Information goes to the skeletal muscles

dorsal roots deals with_information and the neurons that form it are_(2)

-sensory information -somatic sensory neuron and the visceral sensory neuron

ventral root deals with_information and its neurons are_(2)

-motor information -visceral motor neuron and somatic motor neuron

white matter is composed of _in spinal cord

white columns or furnicles

white columns

bundles of myelinated axons that carry signals up and down to and from brainstem

the 3 pairs of columns or furnicles are_

dorsal, lateral, and anterior columns

Each column is filled with _(include their function)

Each column is filled with named tracts or fasciculi (fibers with a similar origin, destination and function)

the whtie matter of spinal cord is composed of_

-myelinated and nonmyelinated nerve fibers that allow communication between different parts of the spinal cord and between the cord and brain

the white matter fibers run in_(3 direction and include the name of those that make up most of the white matter)

-ascending: up to higher centers (sensory inputs) -descending: down to the cord from the brain or within the cord to lower levels (motor outputs) -transverse:across form one side of the cord to the other (commissural fibers) -Ascending and descending tracts make up most of the white matter

how can you determine the orientation of the tracts within white matter?

-with a few exceptions, the names of the spinal tracts reveal both their origin and destination -name of tract will tell you whether is sensory or motor

what are tracts in the spinal cord?

tracts are bundle of neurons (called nerves in CNS) within PNS

ascending tracts will have which kind of information? what about descending?

-Ascending tracts: sensory -Descending tract: motor

_ tract head up or down while _ means that the fibers cross sides

-Ascending and descending -decussation

how contralateral is different to ipsilateral regarding their position of the destination and origin?

Contralateral means origin and destination are on opposite sides while ipsilateral means on same side

state whether is ascending or descending tract:
1. Fasiculus gracisilis
2. Lateral reticulospinal tract
3. dorsal spinocerebellar tract
4. Ventral spinocerebellar tract
5. lateral corticospinal tract

1. ascending tract 2. descending tract 3. ascending tract 4. ascending tract 5. descending tract

explain how spinocerebellar tract works? (type of tract and why)

-ascending tract -start in spine and ends in cerebellum -sensory

give an example of a contralateral cranial nerve?

optic nerve

Cell bodies of the sensory neurons of the spinal nerves are located in ________.

the dorsal root ganglia of the spinal cord

An individual accidentally transected the spinal cord between T1 and L1. This would result in ________.


Second-order neurons of both the specific and nonspecific ascending pathways terminate in the ________.


True or False: The adult spinal cord ends between L1 and L2.


True or false: Cell bodies of the somatic motor neurons of the spinal nerves are located in the ventral horn of the spinal cord.


explain how do you know if tracts is ascending vs descending? (include if it is motor vs sensory)

-If starts with spinal and ends with other stuff is ascending= sensory -If starts with some other stuff and ends with spine is descending= motor

what is the collection of axons in CNS? PNS?

Nerves in PNS is as Tracts in CNS

all major spinal tracts are part of _that connect_

-multineuron pathways -the brain to the body periphery

list the 4 generalizations about the multineuron pathways

1. decussation 2. relay 3. somatotopy 4. symmetry

what is meant by decussation?

-most pathways cross form one side of the CNS to the other (decussate) at some point along their journey

what is meant by relay?

-most pathways consist of a chain of two or three neurons (a relay) that contribute to successive tracts of the pathway


-most pathways exhibit somatotopy, a precise spatial relationship among the tract fibers that reflects the orderly mapping of the body

what is meant by symmetry?

-all pathways and tracts are paired symmetrically (right and left), with a member of the pair present on each side of the spinal cord or brain

Dorsal Column Ascending Pathway (what is in charge of) (4) (what type of information)

-sensory information -Deep touch, ?visceral pain, vibration, and proprioception

3 part of the Dorsal Column Ascending Pathway

-Fasciculus gracilis and cuneatus (both part of the dorsal white column) carry signals from arm and leg (axon will be triggered by receptors, pass cell body, continues on into spinal cord (dorsal white column)) -Decussation of 2nd ?order neuron in medulla -3rd order neuron in thalamus carries signal to cerebral cortex (to decide what to do at the somatosensory cortex of the cerebrum)

what type of neuron is used in Dorsal Column Ascending Pathway? (first neuron)

unipolar neuron

the ascending pathways conduct _impulses _(direction), typically through _to various areas of_(location)

-sensory -upward -chains of three successive neurons (first-, second-, and third-order neurons) -brain

what are both the second- and third-order neurons? (structural type)


the sensory information of the right arm or leg is controlled by_(what side of brain and what part of it)

the left side of the brain at the cerebral cortex

corticospinal tract is what kind? (ascending vs descending)

descending tract (motor)

Corticospinal Tract (1 things that is in charge of)

Precise, coordinated limb movements

describe the corticospinal tract pathway

Two neuron pathway: -upper motor neuron in cerebral cortex -lower motor neuron in spinal cord (then goes out to ventral roots) -Decussation in medulla ?(some will cross and some will not)

descending tracts and pathways have how many neurons?

-Motor ones have 2 neurons: -upper motor neuron and lower motor neuron

The Dorsal Column Ascending Pathways transmitsinpulses via the_ to the_for _(what do with info)

-thalamus to sensory cortex for conscious interpretation

the descending pathways that deliver _impulses from the_to_are divided into two groups:_

-efferent -brain to the spinal cord -1. the direct pathways, equivalent to the pyramidal tracts, and 2. the indirect pathways, essentially all others

what are the two neurons that are involved in motor pathways? (describe what includes)

-upper motor neurons: pyramidal cells of the motor cortex and the neurons of subcortical motor neuclei -lower motor neurons: ventral horn motor neurons, which directly innervate the skeletal muscles

what spinal cord tracts are part of the dorsal white columns? (2) this are part of what pathway?

-fasciculus cuneatus and fasciculus gracilis -Dorsal Column Ascending Pathway

what is another name of corticospinal tract (pathway)?

-direct pyramidal pathway

direct pyramidal pathway (corticospinal) originates where? where they send their impulses? why the direct pathway is called in this way? Once at spinal cord they connect to? (2)

-originate mainly with the pyramidal neurons located in the precentral gyri -These neurons send impulses through the brain stem via the large pyramidal (corticospinal ) tracts -the direct pathways are so called because their axons descend without synapsing from the pyramidal neurosn to the spinal cord -they synapse either with interneurons or with ventral horn motor neurons

the direct (pyramidal) pathway is in charge of_(type of movements)

-fast and fine (or skilled) movements

what is the explanation for the cervical and lumbar enlargements of the spinal cord?

The nerves serving the limbs arise in the cervical and lumbar enlargements of the spinal cord

what is a cuase of spina bifida?

-caused by inadequate amounts of the B vitamin folic acid in the maternal diet

the nerve is what? (structure)

A nerve is a bundle of nerve fibers (axons) (some myelinated and some are not) enclosed by successive wrappings of connective tissue

what are the connective tissue membranes around the nerve? (3 and describe what each of them surround)

Epineurium covers nerves, perineurium surrounds a fascicle and endoneurium separates individual nerve fibers

what penetrates the perineurium?

Blood vessels penetrate only to the perineurium

the bigger the nerve, the_(relate with muscles)

The bigger the nerve the more muscles it stimulates

describe the two types of axons depending where they are going/coming and their respective names (3)

-some axons are sensory (dorsal root) some axons are motor (ventral root) -Some nerves can be only motor or sensory or both

nerve (what it is and it is part of what system)

cordlike organ that is part of the peripheral nervous system


-each axon is surrounded by it


-connective tissue wrapping that binds groups of fibers into bundles called fascicles


-connective tissue that encloses all the fascicles to form the nerve

nerves are classified according to_

the direction in which they transmit impulses

list and describe the 3 classifications of nerves

-mixed nerves: contain both sensory and motor fibers and transmit impulses both to and from the central nervous system -sensory (afferent) nerves: carry impulses only toward the CNS -motor (efferent) nerves: carry impulses only away from the CNS

most nerves are what kind of classification?

mixed nerves pure somatic or motor nerves are rare

the peripheral nerves are classified as_(2) depending on whether_

-cranial or spinal -they arise from the brain or spinal cord

ganglia (what it is and what includes)

collections of neuron cell bodies associated with nerves in the PNS

what are the ganglia within the CNS called?



-collection of neuron cell bodies in the CNS

what are 2 types of ganglia?

-dorsal root ganglia -ventral root ganglia

dorsal root ganglia

-ganglia associated with afferent nerve fibers contain cell bodies of sensory neurons

ganglia associated with efferent nerve fibers mostly contain _

-cell bodies of autonomic motor neurons


Cluster of neuron cell bodies in nerve in PNS

describe dorsal root ganglion (what kind of cell bodies contains, how fibers pass through) (synapse or no synapse)

-Dorsal root ganglion is sensory cell bodies -fibers pass through without synapsing

sensory vs motor:
a. dorsal
b. ventral

a. dorsal=sensory b. ventral=motor

How many pairs of spinal nerves?

31 pairs of spinal nerves

where first cervical spinal nerve is located? (include name) where is the last one of cervical spinal nerves located located?

-1st cervical above C1 (atlas) -last one would be below C7

what kind of nerves exist? what part of spinal vertebra?

mixed nerves exiting at intervertebral foramen

spinal nerves (what are them and what each contain)

-the 31 nerve pairs that arise form the spinal cord -each contain thousands of nerve fibers

spinal nerves are what nerve classification?

all are mixed nerves

spinal nerves are named according to_

where they issue from the spinal cord

what are the 2 types of branches that divide spinal neves?

-proximal branches -distal branches

proximal branches (what is the sensory input, what is the motor output, what roots include and be specific with the numbers) (3)

-dorsal root is sensory input to spinal cord -ventral root is motor output of spinal cord -cauda equina is roots from L2 to C0 of the cord

distal branches (3) (where supply (2), what they branch to)

-dorsal ramus supplies dorsal body muscle and skin -ventral ramus to ventral skin and muscles and limbs -meningeal branch to meninges, vertebrae and ligaments

name the spinal nerve pairs (5) and their respective numbers and their number of pairs (in order from most proximal to distal)

– 8 pairs of cervial spinal nerves (C₁-C₈) -12 pairs of thoracic nerves (T₁-T₁₂) -5 pairs of lumbar nerves (L₁-L₅) -5 pairs of sacral nerves (S₁-S₅) -1 pair of tiny coccygeal nerves (Co₁)

why there are 8 pairs of cervical nerves but only 7 cervical vertbrare?

-The first seven pairs exit the vertebral canal superior to the vertebrae for which they are named for, but C₈ emerges inferior to the seventh cervical vertebra (between C₇ and T₁)

below the cervical level, each spinal nerve leaves_

-the vertebral column inferior to the same-numbered vertebrae

each branch of spinal nerve contains_ (think about two distal branches)

Each has dorsal and ventral ramus.

each spinal nerve connects to the spinal cord by_

a dorsal root and a ventral root

ventral root (contain what kind of fibers, where they arise from, where they extend to)

-contain motor (efferent) fibers that arise from ventral horn motor neurons and extend to and innervate the skeletal muscles

dorsal root (type of fibers where arise, where conduct impulses)

-contain sensory (afferent) fibers that arise from sensory neurons in the dorsal root ganglia and conduct impulses from peripheral receptors to the spinal cord

the spinal roots pass laterally from the cord and _(what do) to form a_before emerging from _via their respective_. because _(2)fibers mingle in a spinal nerve, it contains_

-unite just distal to the dorsal root ganglion -a spinal nerve -vertebral column -intervertebral foramina -motor and sensory -efferent and afferent fibers

ventral rami form_(name and include 4 types)

nerve pleuxes (cervical, brachial, lumbar, and sacral)

the ventral root leads to what? the dorsal root leads to what? (include to waht areas each go)

-Ventral root->ventral ramus->goes to nerves in arm, leg, abdomen -Dorsal root->dorsal ramus->goes to muscles of back

ventral root are _(motor or sensitive) and they will form_

-motor -they will form plexuses in some areas

how the length of cervical region compares with the lumbar and sacral region? (include what forms at the end)

-the spinal roots become progressively longer form the superior to the inferior aspect of the cord -In the cervical region, the roots are short and run horizontally, but the roots of the lumbar and sacral nerves extend inferiorly for some distance through the lower vertebral column canal as the cauda equina before exiting the vertebral column

state in order how spinal nerve transforms as exists spine

-dorsal and ventral rootlets of spinal nerve-> dorsal and ventral root->dorsal root ganglion (dorsal and ventral roots come together within it)->spinal nerve->dorsal ramus/ventral ramus/meningeal branch

almost immediately after the spinal nerve emerges from its foramen, it divides into_(3; the third where goes)

-dorsal ramus -ventral ramus -meningeal branch (that reenters the vertebral canal to innervate the meninges and blood vessels within it)

the spinal nerve rami and their main branches supply the entire_region of the body from the neck down. the dorsal rami supply_and the ventral rami supply_

-somatic region (skeletal muscles and skin) -dorsal rami: supply teh posterior body trunk -ventral rami: supply the rest of the trunk and the limbs

what is the difference between roots and rami? (where located with respect to spinal nerve and motor vs sensory)

-roots lie medial to and form the spinal nerves. Each root is strictly sensory or motor -rami lie distal to and are lateral branches of the spinal nerves. Like spinal nerves, rami carry both sensory and motor fibers

ventral rami of the spinal nerves form_

nerve plexuses

except for_, all ventral rami _(what do) forming complicated _called nerve plexuses

-T₂-T₁₂ -join one another lateral to the vertebral column -interlacing nerve networks called nerve plexuses

nerve plexuses (what are them, what 4 regions are form, and primarily serve_)

-interlacing nerve networks that occur in the cervical, brachial, lumbar, and sacral regions -some of the neurons in one nerve will join neuron of other nerve -primarily serve limbs

how ventral rami form nerve plexuses? how many?

Ventral rami branch and anastomose repeatedly to form 5 nerve plexuses

list the 5 nerve plexuses (where located and what rami numbers include)

1. cervical in the neck, C1 to C5 2. brachial in the armpit, C5 to T1 3. lumbar in the low back, L1 to L4 4. sacral in the pelvis, L4, L5 and S1 to S4 5. coccygeal, S4, S5 and C0

cervical (where in body found, number of ventral rami that include, and were suplies in body (2))

-cervical in the neck, C1 to C5 -supplies neck (skin and muscles) and phrenic nerve to the diaphragm

brachial (where in body found, number of ventral rami that include, and were suplies in body)

-brachial in the armpit, C5 to T1 (C5-C8 to T1) -supplies upper limb and some of shoulder and neck

Lumbar (where in body found, number of ventral rami that include, and were suplies in body)

-lumbar in the low back, L1 to L4 -supplies abdominal wall, anterior thigh and genitalia

Sacral (where in body found, number of ventral rami that include, and were suplies in body)

-sacral in the pelvis, L4, L5 and S1 to S4 -supplies remainder of lower trunk and lower limb

Coccygeal (where in body found, number of ventral rami that include)

coccygeal, S4, S5 and Co1

ventral root contains sensory or motor? this will form_

-motor -plexuses

within plexus, fibers from_(from where and what do)

-fibers from various ventral rami crisscross one another and become redistributed

why plexus is formed? (2) what is the ultimate result of this?

1. each resulting branch of the plexus contain fibers from several spinal nerves 2. fibers form each ventral ramus travel to the body periphery via several routes -as a result, each muscle in a limb receives its nerve supply from more than one spinal never

Due to plexus, each muscle in a limb receives its nerve supply from more than one spinal never , what is an advantage to this?

-an advantage of this fiber regrouping is that damage to one spinal segment or root cannot completely paralyze any limb muscle

phrenic nerve (part of what plexus, which fibers receives, it supplies what)

-part of cervical plexus -which receives fibers from C3, C4, and C5 -it supplies both motor and sensory fibers to diaphragm, which is the chief muscle causing breathing movements

what happens if the phrenic nerve is damaged?

If damage phrenic nerve, cannot have deep breathing because goes to diaphragm

what are the 4 major groups of branches from medial to lateral of brachial plexus? what is the phrase that you can use to memorize them?

(1) ventral rami, called roots, which form (2) trunks, which form (3) divisions, which form (4) cords -"Really Tired? Drink Coffee"

list the main nerves that arise from the brachial plexus (5) and state which one runs right in the center of arm (2)

-axillary nerve -musculocutaneous nerve -median nerve (nerve runs right in the center of arm, anterior to the anterior forearm) -ulnar nerve (branches off the medial cord of the plexus, it descends along the medial aspect aspect of the arm toward the elbow) -radial nerve

cranial nerves can be_(3 kinds of info that can carry)

-motor -sensory -both

when you strike the funny bone, which makes the little finger tingle, what nerve is responsible for this?

ulnar nerve

what two plexuses overlap substantially? through what their fibers to the other plexus? how they are called together?

-the sacral and lumbar plexuses overlap substantially -because many fibers of the lumbar plexus contribute to the sacral plexus via lumbosacral trunk, the two plexuses are often referred to as the lumbosacral plexus

the femoral nerve is part of which plexus? sciatic nerve?

-femoral nerve=lumbar plexus -sciatic nerve= sacral plexus (largest sacral plexus nerve)

each spinal nerve receives _input from specific area of skin called_

-sensory input -dermatome

by what percent dermatomes overlap? what is the consequence of this?

-Overlap at edges by 50% -a total loss of sensation requires anesthesia of 3 successive spinal nerves


the area of skin innervated by the cutaneous branches of a single spinal nerve

how ventral ramis are located in the thorax area? how is this termed?

-only in the thorax are the ventral rami arranged in a simple segmented pattern corresponding to that of the dorsal rami -the ventral rami of T1-T12 mostly course anteriorly, deep to each rib, as the intercostal nerves -these nerves supply the intercostal muscles, the muscle and skin of the anterolateral thorax, and give off cutaneous branches to the skin

how the dorsal rami are located in the back?

-the dorsal rami innervate the posterior body trunk in a neat, segmented pattern -via its several branches, each dorsal ramus innervated the narrow strip of muscle (and skin) in line with where it emerges form the spinal column

every spinal nerve except_innervates dermatomes


how dermatomes can be used for diagnosis?

-in patients with spinal cord injuries, you can pinpoint the damaged nerves and the injured region of the spinal cord by determining which dermatomes are affected -Check for sensation and motor at those levels of the skin

how dermatomes are found in the body trunk?

-adjacent dermatomes on the body trunk are fairly uniform in width, almost horizontal, and in direct line with thier spinal nerves

How dermatome arrangement is in limbs?

-the dermatome arrangement in limbs is less obvious (it is also more variable) -the skin of the upper limbs is supplied by ventral rami of C5-T1 (or T2) -The lumbar nerves supply most of the anterior surfaces of the thighs and legs, and the sacral nerves serve most of the posterior surfaces of the lower limbs

does thoracic nerves will have plexus? if not, how spread?

-Thoracic does not create a plexus -some parts will join ganglia and there is the place where you will have synapses that will help you to spread

what illnes shows within the dermatome area?


dermatomes are also considered_. why?

-spinal levels -it is associated to where the skin connects to the spinal cord (nerve numbers)

what kind of processing is spinal reflexes? (serial or parallel) and explain it

-serial processing -the whole system works in a predictable all-or-nothing manner -one neuron stimulates the next, which stimulates the next, and so on, eventually causing a specific, anticipated response


-rapid, automatic responses to stimuli, in which a particular stimulus always causes the same response

reflexes activity, which produces_behavior,is_(2 characteristics of behavior)

-the simplest -stereotyped and dependable

reflexes occur over neural pathways called_that have 5 essential components

-reflex arcs -five components: receptor, sensory neuron, CNS, integration center, motor neuron, and effector

what pattern of neural processing occurs when your finger accidentally touches a hot grill? what is this response called?

-the pattern of neural processing is serial processing -the response is a reflex arc

somatic reflex (2)

-Quick, involuntary, stereotyped reactions of glands or muscle to sensory stimulation -automatic responses to sensory input that occur without our intent or often even our awareness

Functions by means of a somatic reflex arc (5 steps of pathway)

-stimulation of somatic receptors -afferent fibers carry signal to dorsal horn of spinal cord -one or more interneurons integrate the information -efferent fibers carry impulses to skeletal muscles -skeletal muscles respond

spinal nerves have both dorsal roots and dorsal rami. how are these different from each other in location and composition?

-roots lie medially to spinal nerves, whereas rami lie lateral to spinal nerves -dorsal roots are purely sensory, whereas rami carry both motor and sensory fibers

after this horse-riding accident, the actor Christopher Reeve was unable to breathe on his own. Which spinal nerve roots, spinal nerve, and spinal nerve plexus were involved?

-the spinal nerve roots were C3-C5, the spinal nerve was the phrenic nerve, the plexus was the cervical plexus -the phrenic nerve is the sole motor nerve supply to the diaphragm, the primary muscle for respiration

how does integration at the motor system compare with integration in sensory system? (_endings serving_, type of circuits, behavior)

-in the motor system, we have motor endings serving effectors (muscle fibers) instead of sensory receptors, descending efferent circuits instead of ascending afferent circuits, and motor behavior instead of perception

list the levels of motor control (highest level, 2 at top of motor control hierarchy, and low level)

-the cerebral cortex is at the highest level of our conscious motor pathways -cerebellum and basal nuceli (ganglia) play its role and are therefore at the top of the motor control hierarchy -motor control exerted by lower levels is mediated by reflex arcs

sensory information in a reflex goes to where to be analyzed?

-goes toward the spinal cord

what is a function of reflexes?

-theallow you to respond quickly

the stabilization of _are part of reflexes

stabilization of joints

what is the lowest level of motor hierarchy?

-segmental level

segmental level (level and consists of_(2))

-lowest level of motor hierarchy -it consists of reflexes and spinal cord circuits that control automatic movements

a segmental circuit activates a _, causing them to_

network of ventral horn neurons in a group of cord segments, causing them to stimulate specific groups of muscles

central pattern generators (CPGs) (what do, consists of, these set a_)

-circuits that control locomotion and other specific and often repeated motor activities -it consists of networks of oscillating inhibitory and excitatory neurons, which set crude rhythms and alternating patterns of movements

Nerves that only carry impulses away from the central nervous system (CNS) are called __________.

motor (efferent) nerves

__________ are collections of neuron cell bodies associated with nerves in the peripheral nervous system (PNS). what is the same thing but in the CNS?

-Ganglia -whereas nuclei are collections of neuron cell bodies in the CNS.

The majority of the cranial nerves attach to the __________. [specify how many]
A. cerebellum.
B. brain stem.
C. forebrain
D. spinal cord

B. brain stem. 10 of the 12 pairs of cranial nerves attach to the brainstem.

Which of the following cranial nerves carries only sensory information?
A. olfactory
B. abducens
C. trigeminal
D. oculomotor

A. olfactory

what kind of nerve is olfactory? what kind of impulses it carries and what is their role?

A purely sensory nerve, the olfactory nerve carries afferent impulses for the sense of smell.

Spinal nerves are all classified as __________.
mixed nerves
sensory nerves
afferent nerves
motor nerves

mixed nerves

how many pairs of spinal nerves are mixed nerves? what kind of impulses they can carry?

All 31 pairs of spinal nerves are mixed nerves; they carry both afferent (sensory) impulses toward the CNS and efferent (motor) impulses away from the CNS.

The phrenic nerve serves the __________.


The phrenic nerve, which arises from the _ plexus, supplies_ fibers to the _(organ and role in body). Irritation of the phrenic nerve causes _. If both phrenic nerves are severed, the _(what is damaged and what happens)

The phrenic nerve, which arises from the cervical plexus, supplies both motor and sensory fibers to the diaphragm, the main breathing muscle. Irritation of the phrenic nerve causes spasms of the diaphragm, or hiccups. If both phrenic nerves are severed, the diaphragm is paralyzed and respiratory arrest occurs.

The knee-jerk reflex is an example of a __________.
flexor reflex
tendon reflex
stretch reflex
superficial reflex

stretch reflex

what is the overall goal of stretch reflex?

The overall goal of a stretch reflex is to maintain a muscle’s length, and in turn maintain body position.

why the knee-jerk happens?

the knee-jerk reflex, during which the knee extensors contract in response to being stretched

Which reflex is triggered when a stranger suddenly grasps your arm? [explain how]
crossed-extensor reflex
stretch reflex
plantar reflex
tendon reflex

-crossed-extensor reflex -The grasped arm is withdrawn (via the flexor reflex) as the opposite arm pushes you away from the attacker (via crossed-extensor reflex). As in this scenario, the crossed-extensor reflex often accompanies the flexor reflex.

True or False: The peripheral nervous system (PNS) includes the brain and spinal cord.

False Actually, the PNS includes all neural structures outside of the brain and spinal cord.

the outflow of ANS is characterized by_spanning from_to_. An arrangement consisting of _(2)

The outflow of the ANS is characterized by a two neuron chain spanning from CNS to effector organ. An arrangement consisting of both pre- and postganglionic neurons.

Which of the following is the site of the release of the neurotransmitter norepinephrine?
A. terminus of a sympathetic postganglionic neuron
B. terminus of a parasympathetic postganglionic neuron
C. within the ganglia of the parasympathetic division
D. terminus of a somatic motor neuron
E. within the ganglia of the sympathetic division

A. terminus of a sympathetic postganglionic neuron

the release of norepinephrine at synapses within _is characteristic of_(sympathetic or parasympathetic) division

Release of norepinephrine at synapses within effector organs is characteristic of the sympathetic division (B).

A monosynaptic reflex arc includes a synapse between _

A monosynaptic reflex arc includes a synapse between sensory and motor neurons without the involvement of an interneuron.

what is the function of muscle spindle? (2) (include it works are what kind of receptor)

-determination of muscle length -The muscle spindle indicated is functions as a proprioceptor that is responsive to changes in the length of the surrounding muscle.

how increased muscle length is detected by CNS? what is the response of CNS to this? (2)

Increased muscle length is conveyed to the CNS via afferent neuron. Efferent motor pathways lead to the contraction of the stretched muscle and the relaxation of the antagonistic muscle.

the key center for online sensorimotor integration and control is_


the cerebellum lacks direct connectiosn to_

spinal cord

what basal nuceli do? (receive information from_, send information to_(2) via_)

-receive inputs from all cortical areas and sent their output back mainly to premotor or prefrontal cortical areas via the thalamus

what are varicosities and where would you find them?

-varcosities are the series of knoblike swelling that are the axon endings of autonomic motor neurons -you would find them on axon endings serving smooth muscle or glands

what are the two types of reflexes?

-inborn (intrinsic) reflex -learned (acquired) reflex

inborn reflex (other name and definition)

-intrinsic reflex -a rapid, predictable motor response to a stimulus -it is unlearned, unpremeditated, and involuntary, and is built into our neural anatomy

reflexes prevent us from_

-having to think about all the little details of staying upright, intact, and alive

reflexes control _(3)

-maintain posture -avoid pain -control visceral activities

reflexes do not need help of_(what organ)


what parts of the brain control visceral reflexes? (2)

-brain stem -spinal cord

learned reflexes (other name and definition)

-acquired reflexes -result from practice and repetition

the withdrawal reflex (response to burn yourself with a hot pot) is a _(serial or parallel) processing mediated by_(part of CNS)

-serial -spinal cord

reflexes occur over highly specific neural paths called_

-reflex arcs

what are the 5 basic components of all reflex arcs? the reflex arc passes through what part of CNS?

1. receptor 2. sensory neuron 3. integration center 4. motor neuron 5. effector -spinal cord

explain the component of the reflex arc: receptor

site of stimulus action

explain the component of the reflex arc: sensory neuron

-transmits afferent impulses to the CNS

explain the component of the reflex arc: integration center (2 types and explain each)

-in simple reflex arcs, the integration center may be a single synapse between a sensory neuron and a motor neuron (monosynaptic reflex) -more complex reflex arcs involve multiple synapses with chains of interneurons (polysnaptic reflex)

explain the component of the reflex arc: motor neuron

-conducts efferent impulses form the integration center to the effector organ

explain the component of the reflex arc: effector

-muscle fiber or gland cell that responds to the efferent impulses (by contracting or secreting)

depending on what they activate, what are the 2 classifications of reflexes? (describe each)

-somatic reflexes: if they activate skeletal muscles -autonomic (visceral) reflexes: if they activate visceral effectors (smooth or cardiac muscle or glands)

spinal reflexes

-somatic reflexes that are mediated by the spinal cord

the brain is advised of_(what extent)spinal reflex activity and can_(3), depending on the circumstances.moreover continuous _from _are required for normal spinal reflex activty

-most -facilitate, inhibit, or adapt it -facilitating signals -brain

spinal shock (when occurs and result of it)

-occurs when the spinal cord is transected, immediately depressing all functions controlled by cord

what is the function of testing somatic reflexes?

they are important clinically to assess the condition of the nervous system

muscle spindle

Sense organ (proprioceptor) that monitors length of muscle and how fast muscles change in length

muscle spindle is composed of_(3)

Composed of intrafusal muscle fibers (noncontractile), afferent fibers and gamma motorneurons

what information does your nervous system need to smoothly coordinate activity of your skeletal muscles? (include what structure achieves these)

-the nervous system needs to know the length of the muscle (muscle spindle) -it needs to know the amount of tension in the muscle and its associated tendons (tendon organ)

tendon organs and muscle spindles are_(kind of receptors)


what is meant by "intrafusal" characteristic of muscle spindles? how this applies to muscles

-Normal muscle cell=extrafusal muscle cell that contract and relax -Intrafusal muscle fibers=muscle spindle ->they do not contract or relax

muscle spindles monitor muscle to prevent it to_

over stretch

what fibers innervate the ends of intrafusal muscle fibers of muscle spindles, which these areas are contractile? (what are their roles)

-gamma efferent fibers (γ):maintain spindle sensibility -alpha efferent fibers of the large alpha motor neurons (α): stimulate the extrafusal muscle fibers to contract

the muscle spindle is stretched (and excited) in one of the two ways:

1. by applying an external force that lengthens the entire muscle, such as when we carry heavy weight or antagonistic muscles contract (external stretch) 2. By activating the γ motor neuron that stimulate the distal ends of the intrafusal fibers to contract, thereby stretching the middle of the spindle (internal stretch)

whenever the muscle spindle is stretched, what happens? (think about who it communicates with)

-its associated sensory neurons transmit impulses at higher frequency to the spinal cord

during voluntary skeletal muscle contraction, the muscle shortens, how muscle spindles react to this?

-if the intrafusal muscle fibers did not contract along with the extrafusal fibers, the muscle spindle would go slack and cease generating action potentials. At this point it would be unable to signal further changes in muscle length so it would be useless. Fortunately, α-γ coactivation prevents this form happening. Descending fibers of motor pathways synapse with both α and γ motor neurons, and motor impulses are simultaneously sent to the large extrafusal fibers and to muscle spindle intrafusal fibers. -stimulating the intrafusal fibers maintains the spindle’s tension (and sensitivity) during muscle contraction, s that the brain continues to be notified of changes in the muscle length

what signals extrafusal muscle fibers to contract? (think about muscle spindle)

alpha α motor neurons

another name for the stretch reflex?

Myotatic Reflex

what is the stretch reflex?

When a muscle is stretched, it contracts and maintains increased tonus (stretch reflex)

what are the two functions of stretch reflex?

-helps maintain equilibrium and posture -stabilize joints by balancing tension in extensors and flexors smoothing muscle actions

when your head starts to tip forward as you fall asleep, muscles contract to raise the head. what is responsible for this?

stretch reflex is responsible for it

Very sudden muscle stretch causes _

Very sudden muscle stretch causes tendon reflex

what is an example of tendon reflex? what kind of reflex it is? (polysinaptic or monosynaptic reflex)

knee-jerk (patellar) reflex is monosynaptic reflex

testing somatic reflexes helps_

testing somatic reflexes helps diagnose many diseases

what is reciprocal inhibition function?

Reciprocal inhibition prevents muscles from working against each other

the stretch reflex makes sure that _

the muscle stays at the length that was set by brain

patellar or knee-jerk reflex is a stretch reflex that helps keep your_ explain how

-knees from buckling when you are standing upright -as your knees being to buckle and the quadriceps lengthens, the stretch reflex causes the quadriceps to contract without having to think about it

The Patellar Tendon Reflex Arc (8 basic steps)

1. extensor muscle stretched 2. muscle spindle stimulated 3. primary afferent neuron excited 4. primary afferent neuron stimulates alpha motor neuron to extensor muscle 5. alpha motor neuron stimulates extensor muscle to contract 6. primary afferent neuron stimulates inhibitory interneuron 7. interneuron inhibits alpha motor neuron to flexor muscle 8. flexor muscle (antagonist) relaxes

the more in detail steps of patellar reflex (4)

1. tapping the patellar ligament stretches the quadriceps and excites its muscle spindles 2. afferent impulses travel to the spinal cord, where synapses occur with motor neurons and interneurons 3a. the motor neurons send activating impulses to the quadriceps causing it to contract, extending the knee 3b. the interneurons make inhibitory synapses with ventral horn neurons that prevent the antagonist muscles (hamstrings) from resting the contraction of the quadriceps

stretch reflex (4 steps)

initial stimulus= muscle stretch 1. when stretch activates muscle spindles, the associated sensory neurons transmit afferent impulses at higher frequency to the spinal cord 2. the sensory neurons synapse directly with alpha motor neurons, which excited extrafusal fibers of the stretched muscle. sensory fibers also synapse with interneurons that inhibit motor neurons controlling antagonist muscles (reciprocal inhibiition) 3a. efferent impulses of alpha motor neurons cause the stretched muscle to contract, which resists or reverses the stretch 3b. efferent impulses of alpha motor neurons to antagonist muscles are reduced (reciprocal inhibition)

when a knee-jerk happens, which muscle contracts and which relaxes?

the one stretched, will contract and the antagonist will relax to let the other contract

stretched muscle spindles initiate a _, causing contraction of_and inhibition of_

-stretch reflex -stretched muscle -its antagonist

what is the function of reciprocal inhibition in stretch reflex?

-the resulting inhibition effect caused by the branches of the afferent fibers when they synapse with interneurons -the stretch stimulus causes the antagonists to relax so that they cannot resist shortening of the "stretched" muscles caused by the main reflex arc

all stretch reflexes are_(2 characterisitcs, how many synapses and where located)

-monosynaptic (single synapse) -ipsilateral (motor activity on the same side of the body)

a positive knee jerk (positive result for stretch reflex test) provides two important pieces of information: (2)

1. it provides that the sensory and motor connections between that muscle and the spinal cord are intact 2. the vigor of the response indicates the degree of excitability of the spinal cord

stretch reflexes cause muscle contraction in response is this different for tendon reflexes?

-increased muscle length (stretch) -tendon reflexes produces exactly the opposite effect: muscles relax and lengthen in response to tension

tendon reflexes (4 steps)

1. quadriceps strongly contracts. tendon organs are activated 2. afferent fibers synapse with interneurons in the spinal cord 3a. effferent impulses to muscle with stretched tendon are damped. muscle relaxes, reducing tension 3b. efferent impulses to antagonist muscle cause it to contract

when muscle tension increases substantially during contraction or passive stretching, high threshold _may be activated

tendon organs

afferent impulses, in tendon reflex, are transmitted to _, and then to_, where the information is used to adjust muscle tension

-spinal cord -cerebellum

reciprocal activation (what it is and applies to what)

-when motor neurons in spinal cord circuits supplying the contracting muscles are inhibited and antagonist muscles are activated, -applies to tendon reflex -as a result, the contracting muscle relaxes and its antagonists is activated

tendon organs help to prevent_

muscles and tendons from tearing when they are subjected to possibly damaging stretching force

when does flexor withdrawal reflex happens?

-painful stimulus -Occurs during withdrawal of foot from pain

kind of reflex arc that happens in flexor withdrawal reflex?

Polysynaptic reflex arc

what controls sequence and duration of muscle contractions in flexor withdrawal reflex?

Neural circuitry in spinal cord controls sequence and duration of muscle contractions

flexor withdrawal reflex (4 steps)

1. stepping on glass stimulates pain receptors in right foot 2. sensory neuron activates multiple interneurons 3. ipsilateral motor neurons to flexors excited 4. ipsilateral flexor contracts

withdrawal reflex (other name and definition)

-flexor reflex -reflex initiated by a painful stimulus (actual or perceived); causes automatic withdrawal of the threatened body part from the stimulus

flexor reflexes are_(2 characteristics regarding number of synapses and side of action)

-ipsilateral and polysynaptic

what crossed-extensor reflex does?

Maintains balance by extending other leg

what kind of reflex is crossed-extensor reflex? how it extends and where?

Intersegmental reflex extends up and down the spinal cord

what kind of reflex arcs are found in crossed-extensor reflex? explain how apply if you hurt your foot

Contralateral reflex arcs explained by pain at one foot causes muscle contraction in other leg

steps of crossed-extensor reflex (2 steps and when it starts to act)

-it starts after the flexor (withdrawal) reflex acts 1. contralateral motor neurons to extensor excited 2. contralateral extensor acts

Put both flexor (withdrawal) reflex and crossed-extensor reflex steps

1. stepping on glass stimulates pain receptors in right foot 2. sensory neuron activates multiple interneurons 3. ipsilaterla motor neurons to flexor excited 4. ipsilateral flexor contracts 5. contralaterla motor nuerons to extensor excited 6. contrlateral extensor contracts

crossed-extensor reflex (accompanies what process and important for what)

-often accompanies the flexor reflex in weight-bearing limbs and is particularly important in maintaining balance

what happens if a noxious stimulus is on your arm? (lets say someone grabbed your arm)

-crossed-extensor reflex -a noxious stimulus causes a flexor reflex on the same side, withdrawing that limb (the one that was grasped by the stranger) -site of reciprocal activation (other limb): at the same time, the extensor muscles on the opposite sides are activated

the crossed-extensor reflex is a complex spinal reflex consisting of _(2 reflexes and explain each)

-ipsilateral withdrawal reflex (incoming afferent fibers synapse with interneurons that control the flexor withdrawal response on the same side of the body) -contralateral extensor reflex (with the other interneurons that control the extensor muscles on the opposite site)

explain in simple terms how the crossed-extensor reflex works if you step on glass (mainly what you would do with your body)

-the ipsilateral response causes you to quickly lift your cut foot, while the contralateral response activates the extensor muscles of your opposite leg and to support the weight suddenly shifter to it

what are the two things that the crossed-extensor reflex controls?

-balance -extends the leg that the weight was shifted to (in the case that you step on glass)

while flexor reflex will_,crossed-extensor reflex will_ (regarding muscle action)

-flex -extend

can reflexes be overwritten? how?

-descending signals from teh brain can override reflexes -you can do it with training (like martial arts, baseball)

when a reflex is happening, does any information get to the brain? where does the information and action about the reflex happens/goes?

The pain information will go to brain but the reflex of motion will go to spine

how drugs can affect reflexes?

– interfere with reflexes and make them slow

why when you get drunk you loose balance?

Loose some of the crossed-extensor reflexes when have are drunk. as a consequence, you loose balance.

what is the role of stretch reflex? flexor reflex?

-the stretch reflex is important for maintaining muscle tone and adjusting it reflexively by causing muscle contraction in response to increased muscle length (stretch). it maintains posture -the flexor or withdrawal reflex is initiated by a painful stimulus and causes autonomic withdrawal of the painful body part from the stimulus. it is protective

what is the function of propioreceptors?

-respond to internal stimuli -they constantly advise the brain of our body movements by monitoring how the organs containing these receptors are stretched

describe golgi tendon reflex:
-type of receptor
-where found
-how long

-Proprioceptors in a tendon near its junction with a muscle — 1mm long, encapsulated nerve bundle -Receptor found in tendon that connects muscle to bone

when golgi tendon reflex works? (2) what does?

-Excessive tension on tendon inhibits motor neuron -Also functions when muscle contracts unevenly -muscle contraction decreased

what is the function of golgi tendon reflex?

-if muscle contract too strong, the tendon will stretch too much, will tell muscle to don’t over contract -prevent break of tendons -These reflexes helps keep muscles to over stretch or over contract

what is the major cause of spinal cord trauma?

car accidents

_ people/ year are paralyzed. what percentage occur in car accidents?

-10-12,000 -55% occur in traffic accidents

the spinal cord trauma damage imposes risk to_

This damage poses risk of respiratory failure

early symptoms of spinal trauma are called_

Early symptoms are called spinal shock

what happens to tissue damaged in spinal cord trauma after the time of injury?

Tissue damage at time of injury is followed by post-traumatic infarction

spinal cord, even though it is elastic, ti is sensitive to _

direct pressure

any loacalized damage to the spinal cord or its roots leads to _

some functional loos, either paralysis or paresthesias


loss of motor function (ability to move)


-abnormal sensations

2 types of paralysis

-flaccid paralysis -spastic paralysis

what is damaged in flaccid paralysis? (2)

severe damage to the ventral root or anterior horn cells

why flaccid paralysis happens? what is the consequence of this?

-Lower motor neurons are damaged and impulses do not reach muscles -There is no voluntary or involuntary control of muscles -it has no tonus anymore (muscles atrophy)

what parts are damaged in spastic paralysis?

only upper motor neurons of the primary motor cortex are damaged

why spastic paralysis happens? what is the consequence of this?

-Spinal motor neurons remain intact and muscles are stimulated irregularly -spinal motor neurons remain intact and spinal reflex activity continue sot stimulate the muscles irregularly -There is no voluntary control of muscles

which kind of paralysis you can still have reflexes?

-spastic paralysis

what results from transection of the spinal cord?

Cross sectioning of the spinal cord at any level results in total motor and sensory loss in regions inferior to the cut

what are the two types of transection of the spinal cord?

-paraplegia -quadriplegia

paraplegia (where transection happens)

transection between T1 and L1

quadriplegia (where transection happens)

transection in the cervical region (below C7)

in paraplegia, what parts of the body are affected?

both limbs are affected

in quadriplegia, what parts of the body are affected?

four limbs are affected

anyone with spinal cord transection must be watched for symptoms of_

-spinal schock

spinal shock (what it is and what it does)

-a transient period of functional loss that follows the injury -spinal shock immediately depresses all reflexes activity caudal (below) to the lesion site

can you still have reflexes in quadriplegia? why?

-They can still have spasm in quadriplegia because part of spinal cord controls them, but you cannot control them voluntarily because the brain is not connected anymore (some reflexes will still be present)

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