BIO 137 (Study Guide Test #7, Chs 13-15)

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Which of the following cranial nerves carries only sensory information?
a. olfactory
b. oculomotor
c. trigeminal
d. abducens

A. Olfactory

There are ____ pairs of cranial nerves.
a. 10
b. 14
c. 12
d. 8
e. 6

C. 12

Which cranial nerve transmits information about our sense of equilibrium?
a. vagus
b. optic
c. abducens
d. vestibulocochlear

D. Vestibulocochlear

Nerves that only carry impulses away from the central nervous system (CNS) are called:
a. motor nerves.
b. afferent nerves.
c. mixed nerves.
d. sensory nerves.

A. Motor Nerves

Sympathetic division stimulation causes ________.
a. increased blood glucose, decreased GI peristalsis, and increased heart rate and blood pressure
b. increased blood glucose, increased GI peristalsis, and decreased heart rate and blood pressure
c. decreased blood glucose, increased GI peristalsis, and decreased heart rate and blood pressure
d. decreased blood glucose, increased GI peristalsis, and increased heart rate and blood pressure

A. Increased blood glucose, decreased GI peristalsis, and increased heart rate and blood pressure

For which of the following activities is the parasympathetic nervous system generally responsible?
a. Fight-or-flight responses
b. Running and walking
c. Heartbeat and breathing
d. Resting and digesting

D. Resting and Digesting

Which connective tissue layer directly surrounds each axon in a nerve?
a. myoneurium
b. endoneurium
c. perineurium
d. epineurium

B. Endoneurium

Which of the following is a role of the vitreous humor?
a. It supplies oxygen to the cornea.
b. It supplies nutrients to the lens of the eye.
c. It supports the posterior surface of the lens.
d. It carries away metabolic waste of retinal cells.

C. It supports the posterior surface of the lens.

Where are equilibrium receptors located?
a. Only in the semicircular canals of the ear.
b. In the semicircular canals, in the spiral organ of Corti, and in the vestibule of the ear.
c. In the semicircular canals and in the vestibule of the ear.
d. Only in the vestibule of the ear.

C. In the semicircular canals and in the vestibule of the ear.

The boundary between the external and middle ear is the:
a. tympanic membrane.
b. mastoid antrum.
c. external acoustic meatus.
d. vestibule.

A. Tympanic Membrane

What part of the eye constitutes the blind spot?
a. macula lutea
b. optic disc
c. ora serrata
d. fovea centralis

B. Optic Disc

Eye color is determined by the level of brown pigment present. TRUE OR FALSE.


Which of the following is a characteristic of the lens?
a. The lens of the human eye has a concave shape.
b. The lens is vascularized.
c. The lens focuses light on the retina.
d. In a healthy eye, the lens will be opaque.

C. The lens focuses light on the retina.

Potentially damaging stimuli that result in pain are selectively detected by ________.
a. interoceptors
b. photoreceptors
c. proprioceptors
d. nociceptors

D. Nociceptors

The patellar "knee jerk" reflex is an example of a(n) ________.
a. crossed-extensor reflex
b. stretch reflex
c. extensor thrust reflex
d. stress reflex

B. Stretch Reflex

Pressure, pain, and temperature receptors in the skin are ________.
a. proprioceptors
b. mechanoreceptors
c. interoceptors
d. exteroceptors

D. Exteroceptors

Problems in balance may follow trauma to which nerve?
a. vestibulocochlear
b. accessory
c. trigeminal
d. abducens

A. Vestibulocochlear

The perineurium defines the boundary of a ____.


A fall or an improperly delivered gluteal injection could result in ____.
a. paresthesia
b. neurofibromatosis
c. postpoliomyelitis muscular atrophy
d. sciatica

D. Sciatica

Mixed cranial nerves containing both motor and sensory fibers include all except which of the following?
a. oculomotor
b. facial
c. trigeminal
d. olfactory

D. Olfactory

The only cranial nerves to extend beyond the head and neck region are the vagus nerves. TRUE OR FALSE?


The glossopharyngeal nerve is the only cranial nerve that contains sensory fibers. TRUE OR FALSE?


A patient who received a blow to the side of the skull exhibits the following signs and symptoms on that side of the face: he is unable to close his eye, and the corner of his mouth droops. Which cranial nerve has been damaged?
a. facial
b. glossopharyngeal
c. accessory
d. hypoglossal

A. Facial

In a crossed-extensor reflex, if the right arm was grabbed it would flex and the left arm would ________.
a. extend
b. also flex
c. abduct
d. adduct

A. Extend

The second cranial nerve forms a chiasma at the base of the brain for partial crossover of neural fibers. TRUE OR FALSE?


A reflex that causes muscle relaxation and lengthening in response to muscle tension is called a ________.
a. Golgi tendon reflex
b. crossed-extensor reflex
c. flexor reflex
d. plantar reflex

A. Golgi Tendon Reflex

Which of the following is not an aspect of sensory perception?
a. pattern recognition
b. quality estimation
c. feature abstraction
d. spatial discrimination
e. magnitude estimation

B. Quality Estimation

The cranial nerves that have neural connections with the tongue include all except the ________.
a. facial
b. trigeminal
c. trochlear
d. glossopharyngeal

C. Trochlear

Ventral spinal cord roots contain ___ fibers, while the dorsal roots contain ___ fibers.

Motor, Sensory

The abducens nerve ________.
a. relays sensory information from taste buds on the tongue
b. supplies innervation to the lateral rectus muscle of the eye
c. if paralyzed, exhibits Bell’s palsy
d. exits from the medulla

B. Supplies innervation to the lateral rectus muscle of the eye

There are 41 paris of spinal nerves. TRUE OR FALSE?

False – there are 31 pairs.

The dorsal ramus consists only of motor fibers bringing information to the spinal cord. TRUE OR FALSE


Complex motor behavior such as walking depends on ___ patterns.


Which of the following is not a result of parasympathetic stimulation?
a. dilation of the pupils
b. salivation
c. increased peristalsis of the digestive viscera
d. elimination of urine

A. Dilation of the Pupils

Nerves that carry impulses toward the CNS only are ________.
a. motor nerves
b. afferent nerves
c. efferent nerves
d. mixed nerves

B. Afferent Nerves

If the ventral root of a spinal nerve were cut, what would be the result in the tissue or region that nerve supplies?
a. a complete loss of voluntary movement
b. complete loss of sensation
c. loss of neither sensation nor movement but only of autonomic control
d. a complete loss of sensation and movement

A. A complete loss of voluntary movement.

The sympathetic division is often casually referred to as the ___ system.

Fight or Flight

The vagus nerve does not innervate the ________.
a. kidneys
b. gallbladder
c. pancreas
d. parotid gland

D. Parotid Gland

The ANS stimulates smooth and skeletal muscles and glands, whereas the somatic nervous system innervates cardiac muscles only. TRUE OR FALSE?


The possibility of some control over autonomic responses is demonstrated by ________.
a. biofeedback
b. split brain studies
c. stress-induced hypertension
d. nightmares

A. Biofeedback

The two divisions of the ANS normally have what relationship?
a. disruptive
b. mutualistic
c. antagonistic
d. synergistic

C. Antagonistic

Which is a uniquely sympathetic function?
a. regulation of body temperature
b. regulation of pupil size
c. regulation of respiratory rate
d. regulation of cardiac rate

A. Regulation of Body Temperature

Erection of the penis or clitoris _____.
a. is the result of coordinated activation by both sympathetic and parasympathetic input
b. depends very little on autonomic activation
c. is primarily under parasympathetic control
d. is primarily under sympathetic control

C. Is primarily under parasympathetic control.

Preparing the body for the "fight-or-flight" response is the role of the ________.
a. sympathetic nervous system
b. parasympathetic nervous system
c. somatic nervous system
d. cerebrum

A. Sympathetic Nervous System

The "resting and digesting" division of the autonomic nervous system is the ________.
a. sympathetic division
b. parasympathetic division
c. somatic division
d. peripheral nervous system

B. Parasympathetic Division

Parasympathetic functions include ________.
a. a stimulation of heart rate and force of contraction
b. allowing the body to cope with an external threat
c. lens accommodation for close vision
d. mobilizing storage energy sources

C. Lens accommodation for close vision

Control of temperature, endocrine activity, and thirst are functions associated with the ________.
a. cerebellum
b. thalamus
c. hypothalamus
d. medulla

C. Hypothalamus

Autonomic reflex centers occur in the spinal cord, medulla, and midbrain. TRUE OR FALSE?


Autonomic ganglia are motor ganglia only. TRUE OR FALSE?


Sympathetic division stimulation causes ________.
a. decreased blood glucose, increased GI peristalsis, and increased heart rate and blood pressure
b. increased blood glucose, increased GI peristalsis, and decreased heart rate and blood pressure
c. decreased blood glucose, increased GI peristalsis, and decreased heart rate and blood pressure
d. increased blood glucose, decreased GI peristalsis, and increased heart rate and blood pressure

D. Increased blood glucose, decreased GI peristalsis, and increased heart rate and blood pressure

The craniosacral division is another name for the parasympathetic division. TRUE OR FALSE?


Most body organs are innervated by only the sympathetic division of the nervous system. TRUE OR FALSE?


Sympathetic nerves may leave the spinal cord at which vertebra?
a. first coccyx
b. first thoracic
c. third lumbar
d. second cervical

B. First Thoracic

Cardiovascular effects of the sympathetic division include all except ________.
a. increase of heart rate and force
b. dilation of the vessels serving the skeletal muscles
c. dilation of the blood vessels serving the skin and digestive viscera
d. constriction of most blood vessels

C. Dilation of the blood vessels serving the skin and digestive viscera

The adrenal medulla is considered a "misplaced" sympathetic ganglion by some. TRUE OR FALSE?


The parasympathetic division uses only ________ as a neurotransmitter in the ganglionic neurons.


The chain ganglion, like the dorsal root ganglion, contains soma from sensory neurons. TRUE OR FALSE


Which of these effectors is not directly controlled by the autonomic nervous system?
a. cardiac muscle
b. most glands
c. smooth muscle
d. skeletal muscle

D. Skeletal Muscle

Which ear ossicle connects to the inner ear?
a. incus
b. anvil
c. stapes
d. malleus

C. Stapes

he sensors for dynamic equilibrium are located in what structures?
a. Eustachian tubes
b. semicircular canals
c. ossicles
d. saccule and utricle

B. Semicircular Canals

There are three layers of neurons in the retina. The axons of which of these neuron layers form the optic nerves?
a. rod cells
b. bipolar cells
c. cone cells
d. ganglion cells

D. Ganglion Cells

The major function of the conjunctiva is to:
a. produce tears to lubricate the eyes.
b. produce mucus to prevent the eyes from drying out.
c. lubricate the eyelids so they do not stick together.
d. produce sweat to cool the eyelids.

B. Produce mucus to prevent the eyes from drying out.

The receptor organ for hearing is the _____
a. crista ampullaris.
b. spiral organ of Corti.
c. modiolus.
d. oval window.

B. Spiral Organ of Corti

Ringing in the ears is called:
a. otitis externa.
b. Meniere’s syndrome.
c. tinnitus.
d. otosclerosis.

C. Tinnitus

The retina of the eye extends anteriorly only to a wavy line called the;
a. fovea centralis
b. conjunctiva
c. uvea
d. ora serrata

D. Ora Serrata

The outer portion of the ear composed of the helix and the lobule is the;
a. pinna
b. vestibule
c. external auditory canal
d. palpebrae

A. Pinna

The type of neurons found in the olfactory bulb that process sensory input for smell are the;
a. gustatory cells
b. Eustachian cells
c. ganglion cells
d. mitral cells

D. Mitral Cells

The calcium carbonate (CaCO3) stones located on the maculae are called;
a. ampullae
b. stereocilia
c. ossicles
d. ottoliths

D. Ottoliths

Farsightedness is more properly called ________.
a. hyperopia
b. hypopia
c. myopia
d. presbyopia

A. Hyperopia

Which type of hearing loss occurs when something hampers transfer of sound waves to the inner ear?
a. conduction deafness
b. nerve deafness
c. Meniere’s syndrome
d. tinnitus

A. Conduction Deafness

Which of the following best describes the uvea of the eye?
a. It is the middle layer of the eyeball and is composed of the choroid layer, the ciliary body and the iris. It also provides blood flow to all the layers of the eye and is known as the vascular layer.
b. It is the outer layer of the eye. It includes the sclera and the cornea. The sclera is the white of the eye which protects the eye and allows attachment of the extrinsic eye muscles. The cornea is the clear portion that covers the anterior portion of the eye to admit light and cover the iris and pupil.
c. It is the wavy line in the inside of the eye where the retina ends.
d. It consists of the retina which has a pigmented layer to absorb light and a sensory layer of photoreceptors, ganglia cells and bipolar cells.

a. It is the middle layer of the eyeball and is composed of the choroid layer, the ciliary body and the iris. It also provides blood flow to all the layers of the eye and is known as the vascular layer.

Ling, a 75-year-old grandmother, complained that her vision was becoming obscured. Upon examination by an ophthalmologist she was told she had cataracts. What are cataracts, how do they occur, and how are they treated?
a. A cataract is a clouding of the lens. Some cataracts are congenital, but most are due to age-related hardening and thickening of the lens, diabetes mellitus, or exposure to UV rays over time. The lens can be removed and replaced with an artificial lens.
b. A cataract is a clouding of the cornea. Some cataracts are congenital, but most are due to age-related hardening and thickening of the lens, diabetes mellitus, or exposure to UV rays over time. A corneal transplant can be performed to replace the damaged cornea.
c. A cataract is increased intraocular pressure. This occurs when drainage of the aqueous humor is blocked. They are treated with eyedrops that increase the rate of aqueous humor drainage or decrease its production.
d. A cataract occurs when there are unequal curvatures in different parts of the cornea or lens. This is a congenital condition. Specially ground lenses or laser surgical procedures are used to correct this problem.

A. A cataract is a clouding of the lens. Some cataracts are congenital, but most are due to age-related hardening and thickening of the lens, diabetes mellitus, or exposure to UV rays over time. The lens can be removed and replaced with an artificial lens.

Which of the following structures is not part of the external ear?
a. external acoustic meatus
b. tympanic membrane
c. Eustacian tube
d. pinna

C. Eustacian Tube

The anatomical name for the eyelids is the;
a. lacrimal puncta
b. palpebrae
c. sclera
d. canthi

B. Palpebrae

What is the mechanism by which tears are removed from the eye?
a. Tears drain through the canal of Schlemm into the anterior chamber of the eyeball.
b. Tears drain through the lacrimal puncta in the lateral canthus and into the maxillary sinuses.
c. Tears exit at the medial canthus through the lacrimal puncta and into the lacrimal tubes to drain into the nasal passages.
d. Tears are removed from the eye by evaporation except when crying. Tears then overflow down the face.

C. Tears exit at the medial canthus through the lacrimal puncta and into the lacrimal tubes to drain into the nasal passages.

The clear anterior portion of the fibrous tunic is called the;
a. lens
b. cornea
c. retina
d. conjunctiva

B. Cornea

The blind spot of the eye is where ________.
a. more rods than cones are found
b. the macula lutea is located
c. the optic nerve leaves the eye
d. only cones occur

C. The optic nerve leaves the eye

The anatomical name for the eardrum is the ______________.
a. saccule
b. tympanic membrane
c. olfactory epithelium
d. organ of Corti

B. Tympanic Membrane

The visible colored portion of the eye is the:
a. cornea.
b. pupil.
c. sclera.
d. iris.

D. Iris

Which accessory eye structures function to produce the tears that cleanse and protect the eye?
a. lacrimal glands
b. conjunctiva
c. Meibomian glands
d. medial canthi

A. Lacrimal Glands

The sensors for static equilibrium are located in the saccule and utricle within the vestibule and are called;
a. gustatory cells
b. olfactory epithelia
c. maculae
d. crista ampularis

C. Maculae

What structure regulates the amount of light passing to the visual receptors of the eye?
a. iris
b. cornea
c. lens
d. aqueous humor

A. Iris

There are ____ auditory ossicles in the ear.
a. four
b. two
c. three
d. five

C. Three

Light passes through the following structures in which order?
a. vitreous humor, lens, aqueous humor, cornea
b. cornea, aqueous humor, lens, vitreous humor
c. cornea, vitreous humor, lens, aqueous humor
d. aqueous humor, cornea, lens, vitreous humor

B. Cornea, Aqueous Humor, Lens, Vitreous Humor


All neural structures outside the brain and spinal cord and includes: * Sensory receptors * Peripheral nerves * Ganglia * Motor endings (effectors)


* Respond to stimuli


* Mechanoreceptors – touch * Thermoreceptors – temperature * Photoreceptors – light * Chemoreceptors – chemicals (e.g. smell, taste, changes in blood chemistry) * Nociceptors – pain


* Exteroceptors – arising outside the body * Interoceptors – arising inside the body * Proprioceptors – degree of stretch of the organs they occupy. Constantly "advise" the brain of one’s movements.


* Simple – encapsulated dendritic endings * Complex – special sense organs


3 main levels of neural integration: * Receptor – adaptation (pain receptors and proprioceptors do not exhibit adaptation) * Circuit – reflexes and stereotyped sequential actions * Perceptual – cerebral cortex (very complex) Main aspects of sensory perception (perceptual detection, magnitude estimation, spatial discrimination, feature abstraction, quality discrimination, pattern recog)


* Endoneurium – loose connective tissue that surrounds individual nerve fibers * Perineurium – coarse connective tissue that bundles fibers into fascicles * Epineurium – tough fibrous sheath around a nerve


Sensory and motor divisions: * Sensory (afferent) carry impulse to the CNS * Motor (efferent) – carry impulses from CNS * Mixed – sensory and motor fibers carry impulses to and from CNS; most common type of nerve


Regeneration involves coordinated activity among: * Macrophages – remove debris * Schwann cells – regenerate and secrete growth factors * Axons – regenerate damaged part


* Cranial nerves – 12 numbered and names * Spinal nerves – 31 numbered pairs


* 12 pairs of nerves arise from the brain * They have sensory, motor, or both sensory and motor functions * Each nerve is identified by a number (I through XII) and a name


* Sensory nerve * Sense of smell


* Sensory nerve * Vision


* Motor nerve * Functions in raising the eyelid, directing the eyeball, and also constricting the iris, and controlling lens shape. Controls 4 of the 6 extrinsic eye muscles


* Motor nerve * Innervate the superior oblique muscle (the 5th extrinsic eye muscle)


* Mixed nerve * Conveys ‘sensory’ impulses from various areas of the face, and supplies ‘motor’ fibers for mastication


* Motor nerve (primarily) * Innervating the lateral rectus muscle (the 6th extrinsic eye muscle)


* Mixed nerve (5 major branches) * Motor functions – facial expression, and innervation of lacrimal and salivary glands * Sensory function – taste from the anterior two-thirds of the tongue


* Sensory nerve * Balance (equilibrium) and hearing


* Mixed nerve * Motor – innervates part of the tongue and pharynx, and the parotid salivary gland * Sensory – taste and general sensory impulses from the tongue and pharynx


* Mixed nerve * Motor – heart, lungs, and visceral organs * Sensory – taste


* Motor nerve * Larynx, pharynx, and saft palate * Innervates the trapezius and sternocleidomastoid


* Motor nerve * Innervates both extrinsic and intrinsic muscles of the tongue (swallowing and speech)


31 pairs of mixed nerves (named according to their point of issue) * 8 cervical (C1-C8) * 12 thoracic (T1-T12) * 5 Lumbar (L1-L5) * 5 Sacral (S1-S5) * 1 Coccygeal (C0)


* Ventral roots arise from the anterior horn and contain motor (efferent) fibers * Dorsal roots arise from sensory neurons in the dorsal root ganglion and contain sensory (afferent) fibers


The spinal nerves branch into three rami immediately upon exiting the spinal cord * Small dorsal ramus – serves the body posterior to the spinal cord * Larger ventral ramus – innervates the anterior trunk (Largest of the branches) * Tiny meningeal branch – serves the meninges


A dermatome is the area of skin innervated by the cutaneous branches of a single spinal nerve (all except C1)


Hilton’s law: any nerve serving a muscle that produces movement at a joint also innervates the joint itself and the skin over the joint


* Simpler than neuromuscular junctions * Branches form varicosities at diffuse junctions (acetylcholine and norepinephrine are neurotransmitters)


* Lowest level of motor heirarchy * Consists of segmental circuits called central pattern generators (e.g. walking is a specific sequence of movement)


Rapid, predictable motor response to a stimulus


* Stretch reflexes are initiated by muscle spindles maintain healthy muscle tone * Stretching the muscle activates the muscle spindle and initiates reflex arc (e.g. patellar reflex)


* Opposite of stretch reflex * As a result, the muscle relaxes and the antagonist contracts


* Flexor – initiated by pain, automatic withdrawal of threatened body part * Crossed extensor – stim side is withdrawn, opp side is extended (e.g. stepping on glass)


* Plantar reflex – downward flexion of toes * Babinski’s sign – abnormal plantar reflex indicating corticospinal damage * Spinal reflexes are used in medicine to assess the CNS


* Consists of motor neurons that innervate smooth and cardiac muscle and glands (operate via subconscious control) ANS vs. SOMATIC NERVOUS SYSTEM (SNS) * Effectors – SNS: innervates skeletal muscles via neuromuscular junctions – ANS: innervates cardiac muscle, smooth muscle, and glands via diffuse junctions * Neurotransmitters – SNS: motor neurons release ACh which has an excitatory effect – ANS: Preganglionic – ACh, Postganglionic (norepinephrine or ACh). Effect is either excitatory or inhibitory * Motor (efferent) pathways – SNS: a motor pathway has a single motor neuron – ANS: all motor pathways have two neurons (1-preganglionic (first) neuron synapses in the ganglion, 2-postganglionic (second) neuron extends to an effector organ)


ANS divisions: sympathetic and parasympathetic FUNCTIONS: * Sympathetic (thoracolumbar) – "fight or flight" (mobilizes the body during extreme situations) E activities – "exercise, emergency, ambarrassment" (NE/E released into blood, long-lasting, diffuse effects that come on almost instantly [S81]) – Pathways: paravertebral chain ganglia, abdominal aortic plexus, adrenal medulla (misplaced ganglia) * Parasympathetic (craniosacral-in the visceral effector organs) – "resting and digesting" (performs maintenance activities and conserves body energy) D activities – "digestion, defecation, diuresis". (short-lives, highly localized control that is slow to achieve) – Pathways: preganglionic neurons synapse in terminal ganglia located near the organ innervated * The two divisions counterbalance each other


* One or the other is usually dominant. This causes two interactive effects: – Antagonistic interactions (most common-best seen in fight or flight reaction) – SYMP: HR increases, breathing rapid and deep. PARASYMP: reverse. – Cooperative interactions (best seen in control of the external genitalia) – PARA: arousal/erection of penis and clitoris. SYMP: climax/ejaculation (men), reflex peristalsis (women) * Only the Sympathetic division has unique solo roles in control: – Thermoregulatory responses to heat – Release of renin (endocrine hormone) from the kidneys – Metabolic effects


* The hypothalamus – Main integration center of ANS activity * Centers of hypothalamic control: – Heart activity and blood pressure – Body temperature, water balance, and endocrine activity – Emotional stages (rage, pleasure) and biological drives (hunger, thirst, sex) – Reactions to fear and the "fight-or-flight" system OTHER LEVELS: * Spinal cord – Micturation and defecation (under conscious inhibition) * Brain Stem – Medulla – heart rate, vasomotor, gastrointestinal – Pons – respiratory – Midbrain – size of pupils * Cerebral cortex – Demonstrated by Meditation and Biofeedback


* During youth, ANS impairments are usually due to injury * In old age, ANS efficiency decreases, resulting in constipation, dry eyes, and orthostatic hypotension – Orthostatic hypotension is a form of low blood pressure that occurs when sympathetic vasoconstriction centers respond slowly to positional changes (you faint when you stand up).

* Eyebrows
* Palpebrae (eyelids)
* Conjuctiva
* Lacrimal Apparatus
* Extrinsic Eye Muscles

* The eye is the organ of sight. * Eyebrows – functions: shades the eye and prevents sweat from reaching the eye * Palpebrae (eyelids) – Protects the eye anteriorly. * Conjunctiva – transparent mucus membrane that: lines the eyelids and whites of the eyes, lubricates and protects the eye. * Lacrimal apparatus – Lacrimal gland and associated ducts – secrete tears. *Extrinsic eye muscles – 6 strap-like muscles (4 rectus, 2 oblique)

* 3 tunics/layers – fibrous, vascular, sensory

* Fibrous – forms the outermost cost, composed of: sclera (opaque, white, posterior portion of fib tun), cornea (lets light enter the eye) * Uvea (vascular tunic) – 3 regions: choroid, ciliary body, and iris – Chroroid-dark brown membrane, supplies blood to all eye tunics – Ciliary body-thickened ring of tissue surrounding the lens, anchors the suspensory ligaments that hold lens in place – Iris-colored part of the eye * Sensory (retina) – delicate 2-layer membrane


* Optic disc – site where optic nerve leaves the eye * lacks photoreceptors (the blind spot)

* Rods
* Cones

* Rods: dim light, peripheral vision…RDP * Cones: bright light, color vision, concentrated near fovea centralis (highest concentration of rods and cones, point o most acute vision)


* Separates internal eye into anterior and posterior segs. * Posterior segment-filled with vitreous humor (maintains shape, holds retina in place) * Anterior segment-filled with aqueous humor, drains via the Schlemm (supports, nourishes, and removes wastes)


* A biconvex, transparent, flexible, avascular structure * Lens fibers – cells filled with the transparent protein crystallin * With age, the lens becomes more compact and dense and loses its elasticity


* Electromagnetic radiation – all energy waves from short gamma rays to long radio waves – Our eyes respond to a small portion of this spectrum called the visible spectrum (we don’t see UV)


* When light passes from one transparent medium to another its speed changes and it refracts (bends) * Light is refracted: – At the cornea – Entering the lens – Leaving the lens * FOCUSING FOR CLOSE VISION: – Accommodation – changing the lens shape by ciliary muscles to increase refractory power * PROBLEMS OF REFRACTION: – Myopic eye (nearsighted) – eyeball is too long, corrected with concave lens – Hyperopic eye (farsighted) – eyeball is too short, corrected with convex lens


* Rods and cones contain visual pigments that change shape as they absorb light. * Rods – sensitive to dim light, best suited for night vision, absorbs all wavelengths of visible light (they see in black and white) – Excitation of rods-visual pigments is rhodopsin * Cones – needs bright light for activation, colored view, vision is detailed and high resolution – Excitation of cones-visual pigments (retinal+opsins), 3 types of cones: red, green, blue CHEMISTRY OF VISUAL PIGMENTS * Retinal – light absorbing molecule that combines with proteins called opsins to form visual pigments


* Achieved by both eyes viewing the same image from slightly different angles

* Gustation (taste)
* Olfaction (smell)

SENSE OF SMELL * The organ of smell is the olfactory epithelium, which covers the superior nasal concha * Olfactory receptors respond to several different odor-causing chemicals * Receptor cells synapse with mitral cells-which process odor signals TASTE BUDS * Organ of taste * Most of the 10,000 or so taste buds are found on the tongue * Found in paplillae of tongue mucosa * 3 types: filiform, fungiform, and circumvallate * Fungiform and circumvallate papillae contain taste buds * Structure: Gustatory cells – taste cells * Sensations – five basic taste sensations: sweet, salt, sour, bitter, umami (savory-amino acid glutamate, recently discovered) * TASTE IS 80% SMELL


* 3 parts of the ear: inner (hearing and equillibrium), outer (hearing), and middle (hearing). * Outer: auricle (pinna), external auditory canal * Tympanic membrane (eardrum)-boundary between outer and middle * Middle: eustachian tube-connects middle ear to nasopharynx. Contains 3 small bones (ossicles): malleus, incus, and staples which amplifies sound 20x. * Inner: vestibule, cochlea, semicircular canals, filled with perilymph – Vestibule [static equillibrium]-central egg-shaped cavity of the bony labyrinth, saccule and utricle sacs-house equillibrium receptors (maculae-sensory receps for static equil) and respond to gravity and changes of position of the head. Maculae has stereocilia and kinocilium embeded in the otolithic membrane (CaCO3 stones called otoliths) – Semicircular canals [dynamic equillibrium]-3 canals that each define 2/3 of a circle and lie in the 3 planes of space. Ampulla (swollen end) of each canal houses equ receps in a region called crista ampullaris and respond to angular movements of head. Each crista has hair cells that extend into a gel-like mass called the cupula. Rotational movement. – Cochlea-organ of Corti (hearing receptor that has stereocilia hairs and protude into the endolymph). Divided into 3 chambers (scala vestibuli,, s.tympani). The bending of cilia opens mechanically gated ion channels causing a graded potential and release of neurotrans.

* Conduction Deafness
* Nerve Deafness

* Conduction – something hampers sound conduction to the fluids of the inner ear (e.g. impacted earwax) * Nerve – damage to the neural structures * Tinnitus – ringing of clicking sound * Meniere’s syndrome – labyrinth disorder causing vertigo, nausea, and vomiting


* Otolithic movement in one direction: – Depolarizes vestibular nerve fibers, Increases the number of action potentials generated * Movement in the opposite direction: – Hyperpolarizes vestibular nerve fibers, and reduces the rate of impulse propagation * From this information, the brain is informed of the changing position of the head


* Babies are hyperopic, see only gray tones, and eye movements are uncoordinated. * Depth perception and color and emmetropic eyes are developed by age 6. * With age, lens loses clarity, dilator muscles become less efficient, and visual acuity is drastically decreased by age 70.

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