CH.7 A&P

The __________ nervous system consists of motor neurons that regulate skeletal muscle contractions.

somatic

The membranes of neurons at rest are very permeable to _____ but only slightly permeable to _____.

K+;Na+

During depolarization, which gradient(s) move(s) Na+ into the cell?

both the electrical and chemical gradients

What is the value for the resting membrane potential for most neurons?

-70 mV

The Na+-K+ pump actively transports both sodium and potassium ions across the membrane to compensate for their constant leakage. In which direction is each ion pumped?

Na+ is pumped out of the cell and K+ is pumped into the cell.

The concentrations of which two ions are highest outside the cell.N

Na+ and Cl

Where do most action potentials originate?

initial segment

What opens first in response to a threshold stimulus?

Voltage-gated Na+ channels

What characterizes depolarization, the first phase of the action potential?

The membrane potential changes from a negative value to a positive value.

What characterizes repolarization, the second phase of the action potential?

Once the membrane depolarizes to a peak value of +30 mV, it repolarizes to its negative resting value of -70 mV.

What event triggers the generation of an action potential?

The membrane potential must depolarize from the resting voltage of -70 mV to a threshold value of -55 mV.

What is the first change to occur in response to a threshold stimulus?

Voltage-gated Na+ channels change shape, and their activation gates open.

If we apply an electrical stimulus to a muscle cell to cause it to contract, the magnitude of that stimulus must be strong enough to reach a critical value that is essential to initiate contraction. This critical value is known as __________.

threshold

Whether a membrane is depolarized to threshold or above, the amplitude of the resulting action potential is the same; in other words, once threshold is reached, the action potential will take place. This concept is known as __________.

the "all-or-none principle"

A large, rapid change in membrane potential produced by depolarization of an excitable cell’s plasma membrane to threshold is known as __________.

an action potential

What type of conduction takes place in unmyelinated axons?

Continuous conduction

An action potential is self-regenerating because __________.

depolarizing currents established by the influx of Na+‎ flow down the axon and trigger an action potential at the next segment

Why does regeneration of the action potential occur in one direction, rather than in two directions?

The inactivation gates of voltage-gated Na+‎ channels close in the node, or segment, that has just fired an action potential.

What is the function of the myelin sheath?

The myelin sheath increases the speed of action potential conduction from the initial segment to the axon terminals.

What changes occur to voltage-gated Na+ and K+ channels at the peak of depolarization?

Inactivation gates of voltage-gated Na+‎ channels close, while activation gates of voltage-gated K+‎ channels open.

In which type of axon will velocity of action potential conduction be the fastest?

Myelinated axons with the largest diameter

Which of the following glial cells is responsible for forming myelin around axons in the peripheral nervous system?

Schwann cells

What is the molecular basis of the absolute refractory period?

voltage-gated sodium channel structural changes

Electrical signals that neurons use to transmit information over long distances are __________ potentials.

action

When a neuron is at rest ______ leaks out of the cell, while _____ leaks into the cell.

potassium; sodium

Action potentials are initiated at the __________.

axon hillock

Saltatory conduction occurs in __________.

myelinated axons

An action potential begins with an increased permeability to ___________, resulting in a __________ phase.

sodium; depolarization

In the peripheral nervous system, __________ neurons carry sensory and visceral information to the central nervous system, and __________ neurons leave the central nervous system and innervate organs, which are usually muscles or glands.

afferent : efferent

The central nervous system, which is composed of the brain and spinal cord, receives and processes information from both the external environment, known as __________ information and, the internal environment, which refers to __________ information.

sensory : visceral

Which of the following accurately describes afferent neurons?

They transmit information from the periphery to the CNS.

What two divisions of the autonomic nervous system have opposite effects on the organs they innervate?

parasympathetic and sympathetic

What portion of the efferent branch of the nervous system communicates to glands and cardiac muscle?

autonomic nervous system

What portion of the peripheral nervous system transmits information from sensory receptors to the central nervous system?

afferent nervous system

What portion of the efferent nervous system communicates with skeletal muscle?

somatic nervous system

Information gathered about our internal environment (i.e., fullness of the stomach, blood pressure, etc.) is called ________ information.

visceral

Effector organs act as receptors that detect information about the external environment and transmit that information to the central nervous system.

FALSE

Which part of a neuron would be most impacted by novocaine?

axon

What is the functional unit of the nervous system?

neurons

An action potential originates at the ________ and travels along the axon until it reaches the ________.

axon hillock : axon terminal

What type of ion channels in the membrane of neurons allows ions to move across the membrane at rest and thereby contribute to resting membrane potential?

leak channels

What type of ion channels in the membrane of neurons open or close in response to a neurotransmitter binding to its receptor?

ligand-gated channels

In a neuron, where is the greatest concentration of voltage-gated sodium and voltage-gated potassium channels?

axon hillock

A group of nerve cell bodies in the peripheral nervous system are referred to as

ganglia

What type of cell enhances the velocity of electrical transmission of an action potential along an axon in the central nervous system?

oligodendrocyte

In the peripheral nervous system, myelin is formed by ________. In the central nervous system, myelin is formed by ________.

Schwann cells : oligodendrocytes

At rest, the plasma membrane is more permeable to which of the following ions?

potassium (K+)

The resting membrane potential is close to the equilibrium potential of which of the following ions?

potassium (K+)

Ions are unequally distributed across the plasma membrane of all cells. This ion distribution creates an electrical potential difference across the membrane. What is the name given to this potential difference?

Resting membrane potential (RMP)

Sodium and potassium ions can diffuse across the plasma membranes of all cells because of the presence of what type of channel?

Leak channels

On average, the resting membrane potential is -70 mV. What does the sign and magnitude of this value tell you?

The inside surface of the plasma membrane is much more negatively charged than the outside surface.

The plasma membrane is much more permeable to K+ than to Na+. Why?

There are many more K+ leak channels than Na+ leak channels in the plasma membrane.

The resting membrane potential depends on two factors that influence the magnitude and direction of Na+ and K+ diffusion across the plasma membrane. Identify these two factors.

The presence of concentration gradients and leak channels

What prevents the Na+ and K+ gradients from dissipating?

Na+-K+ ATPase

Most neurons have a resting membrane potential of

-70 mV.

At the resting membrane potential, the membrane is most permeable to ________, which moves ________ the cell due to its electrochemical gradient.

potassium : out of

The ________ maintains the resting membrane potential.

Na+/K+ pump

Where in the neuron is an action potential initially generated?

axon hillock

The depolarization phase of an action potential results from the opening of which channels?

voltage-gated Na+ channels

The repolarization phase of an action potential results from __________.

the opening of voltage-gated K+ channels

Hyperpolarization results from __________.

slow closing of voltage-gated K+ channels

What is the magnitude (amplitude) of an action potential?

100 mV

Which of the following functions does NOT increase during the fight-or-flight response?

blood flow to gastrointestinal organs

All EXCEPT which of the following organs receives its innervation from fibers that synapse with preganglionic neurons in collateral ganglia?

the heart

Which general aspect of the autonomic nervous system increases cardiac output?

sympathetic

Which branch of the peripheral nervous system is most active during rest?

parasympathetic

The two branches of the autonomic nervous system are the __________ and __________.

sympathetic; parasympathetic

Parasympathetic preganglionic cell bodies are located in the brainstem and _____ region of the spinal cord.

sacral

Sympathetic preganglionic cell bodies are located in the __________ and __________ regions of the spinal cord.

thoracic; lumbar

The neurotransmitter used between preganglionic and postganglionic cells in the autonomic nervous system is __________.

acetylcholine

The receptors on effectors for parasympathetic postganglinic axons are categorized as __________, while the receptors on effectors for sympathetic postganglionic axons are __________.

cholinergic; adrenergic

Which of the following neurotransmitters is released at the neuromuscular junction by motor neurons?

acetylcholine

Which area of the CNS regulates the autonomic output (sympathetic or parasympathetic) that controls blood pressure?

medulla oblongata

What does the somatic nervous system innervate?

muscle

…

…

What are the effects of beta blockers?

Reduce sympathetic stimulation and reduce heart rate and blood pressure.

Where do preganglionic neurons of the sympathetic nervous system originate?

lateral horn or intermediolateral cell column of the spinal cord

Which of the following physiological responses is associated with elevated sympathetic nervous system activity?

increased contractile force of the heart

Which of the following physiological responses is associated with an elevation in parasympathetic nervous system activity?

enhanced absorption of nutrients

At rest, what is the relative contribution of the sympathetic and parasympathetic nervous systems to the regulation of homeostasis?

Both systems are active but the parasympathetic predominates.

Sympathetic ganglia that are linked together and run in parallel on either side of the spinal column are called

sympathetic chains or trunks.

What is meant by dual innervation in the autonomic nervous system?

Both branches of the autonomic nervous system innervate most organs with opposite functions: one to maintain rest and the other to increase activity.

Which of the following endocrine glands is innervated by sympathetic preganglionic neurons?

adrenal medulla

Parasympathetic postganglionic neurons release the neurotransmitter ________; sympathetic postganglionic neurons release the neurotransmitter ________.

acetylcholine : norepinephrine

Binding of acetylcholine to ________ receptors causes a ________ by opening channels that primarily permit sodium to permeate the membrane.

nicotinic : depolarization

What types of neurons detect changes in our internal and external environment?

sensory

A stronger stimulus will result in action potentials that are __________.

more frequent

Receptors that detect changes in pressure would be categorized as __________.

mechanoreceptors

__________ are receptors that respond to tissue damage, sending signals that our brain interprets as pain.

Nociceptors

Specific neural pathways carrying specific sensory modalities are called __________.

labeled lines

What is another name for a receptor potential produced at sensory receptors?

generator potential

Where is the visual cortex found?

occipital lobe

Where is the auditory cortex found?

temporal lobe

What is the location of the gustatory nucleus?

brainstem

What is the location of the gustatory cortex?

parietal lobe

What is the location of the medial geniculate body?

thalamus

Where is the termination of second-order neurons found?

thalamus

What is the location of the dorsal columns?

spinal cord

As people age, presbyopia develops. This results in hyperopia and results in what complication?

The light reflected from the object is focused behind the light-sensing retina.

How is the amount of light allowed into the eye regulated?

contraction of the radial and circular muscles of the eye

Ciliary muscle is innervated by what branch of the nervous system?

parasympathetic

When the ciliary muscles are relaxed, the lens is relatively ________, allowing the eye to focus on objects that are ________.

flat : distant

Light waves refract as they pass through what structures of the eye?

cornea and lens only

The cornea and lens are ________ surfaces that cause light to converge on a ________.

convex : focal point

What nourishes the lens and cornea?

aqueous humor

In order to focus light coming from a near source onto the retina, the lens adjusts its refractive power through what process?

accommodation

What is a condition where light, originating from a distance, is focused in front of the retina?

myopia

What is a condition where light, originating from a close-up source, is focused behind the retina?

hyperopia

Which of the following describes irregularities in the structure of the cornea or lens?

astigmatism

Which of the following occurs during accommodation for near vision?

Ciliary muscles contract, causing zonular fibers to become slack, and the lens becomes rounder.

Which of the following is not a cell type found in the retina?

macular cells

The first neurons capable of generating action potentials in the transmission pathway for visual information detected by rods and cones are the ________ cells.

ganglion

The ganglion cells of the retina synapse with neurons in the ________ that ascend to the ________.

lateral geniculate body : primary visual cortex

What is the first refractive structure through which light waves must pass as they enter the eye?

cornea

What structure is comprised of neural tissue that includes bipolar cells?

retina

What is the hole through which light can enter the eye called?

pupil

What category of structures includes the rods and cones?

photoreceptors

What is the pigmented structure that absorbs light waves?

retinal pigmented epithelium

What muscle is under parasympathetic control to regulate the refractive power of the lens?

ciliary muscles

What is the site of highest visual acuity?

fovea

The optic nerve exits the eye at what point?

optic disk

Light striking what region of the retina is not detected by photoreceptors?

optic disk

Where is retinal found?

both rods and cones

Which of the following is the most abundant in the retina?

rods

Which of the following is associated with high visual acuity?

cones

Which of the following is most sensitive to light?

rods

In the figure, what are the structures, in order from 1 to 5?

ciliary body, iris, fovea, retina, sclera

An increase in pressure within the eye due to expansion of the aqueous humor that can eventually compromise blood flow to the eye is called

glaucoma

During near vision, the ciliary muscle contractsdue to activation of the (sympathetic / parasympathetic) nervous system. As a result, the zonular fibers to go slack, which causes the refractive power of the lens to increase and the lens become rounder

parasympathetic

Sound waves traveling through the air initiate a vibration of the ________. The sound waves are then transmitted along the ________ to the cochlea.

tympanic membrane : ossicles

The amplitude of a sound wave is determined by the difference in the

air molecule density in the compressed versus rarified regions of the sound wave.

The organ of Corti is located on what membrane?

basilar membrane

The ________, projecting from the end of hair cells, are attached to the ________, which causes them to bend when sound waves enter the cochlea.

stereocilia : basilar membrane

Bending of the stereocilia on the hair cell can induce either a closure or an opening of a potassium channel based upon the

direction that the stereocilia move.

Frequency of sound is coded for by the

location of the hair cell stimulated.

What transmits sound energy from the outer ear to the middle ear?

tympanic membrane

What structure includes the scala media, scala tympani, and the scala vestibule?

cochlea

What structure detects linear acceleration?

utricle

Which of the following connects the middle ear to the pharynx?

Eustachian tube

What structure detects rotational acceleration of the head?

semicircular canals

The anterior portion of the semicircular canal detects acceleration in which direction?

moving the head up and down as in saying "yes"

The saccule detects what type of motion?

linear acceleration up or down

Which sensation has a receptor type that is a chemoreceptor?

both olfaction and taste

Molecules must be dissolved in fluid to interact with the receptor for which of the following?

both olfaction and taste

The somatic nervous system is often referred to as the ________ system.

voluntary

What is the neurotransmitter released from motor neurons?

acetylcholine

The opening of a cation channel that allows both Na+ and K+ to move through will cause the membrane to ________ because of the ________.

depolarize : greater Na+ electrochemical gradient as compared with K+