Anatomy Exam 4

sensation

the awareness of changes in the internal and external environment

perception

the conscious interpretation of stimuli

somatosensory system

part of sensory system serving body wall and limbs, receives inputs from exteroreceptors, proprioceptors, and interoceptors

sensory receptors

specialized to respond to changes in environment, activation results in graded potentials that trigger nerve impulses

mechanoreceptor

respond to touch, pressure, vibration, and stretch

thermoreceptor

sensitive to changes in temperature

photoreceptor

respond to light energy

chemoreceptor

respond to chemicals dissolved in solution

nociceptor

sensitive to pain causing stimuli

exteroreceptor

respond to stimuli arising outside the body, receptors in skin for touch, pain, and temperature, most special sense organs

interoceptor

respond to stimuli arising in internal viscera and blood vessels, sensitive to chemical changes, tissue stretch, and temperature changes, sometimes cause discomfort but usually unaware of their workings

proprioceptor

respond to stretch in skeletal muscles, tendons, joints, ligaments, and connective tissue coverings of bones and muscles, inform brain of one’s movements

simple receptors - general senses

tactile sensations, temperature, pain, and muscle sense, modified dentritic endings of sensory neurons

special sense receptors

vision, hearing, equilibrium, smell, and taste

nonencapsulated (free) nerve endings

abundant in epithelia and connective tissues, most are nonmyelinated, respond mostly to temperature and pain

cold receptors

10-40 C, in superficial dermis

heat receptors

32-48 C, in deeper dermis

all encapsulated nerve endings:

are mechanoreceptors

tactile corpuscles (encapsulated)

discriminative touch

lamellar corpuscles (encapsulated)

deep pressure and vibration

bulbous corpuscles (encapsulated)

deep continuous pressure

muscle spindles (encapsulated)

muscle stretch

tendon organs (encapsulated)

stretch in tendons

joint kinesthetic receptors (encapsulated)

joint position and motion

olfactory nerve I

sensory nerves of smell, run from nasal mucosa to olfactory bulbs, pass through cribiform plate of ethmoid bone, purely sensory function

optic nerve II

arise from retinas, pass through optic canals, converge and partially cross over at optic chiasma, optic tracts continue to thalamus where they synapse, purely sensory function

occulomotor nerve III

fibers extend from ventral midbrain through superior orbital fissures to four of six extrinsic eye muscles, function in raising eyelid, directing eyeball, constricting iris, and controlling lens shape

trochlear nerve IV

fibers from dorsal midbrain enter orbits via superior orbital fissures to innervate superior oblique muscle, primarily motor nerve that directs eyeball

trigeminal nerve V

largest cranial nerves, fibers extend from pons to face, three divisions (ophthalmic, maxillary, mandibular), convey sensory impulses from various areas of face, supply motor fibers for mastication

ophthalmic V1

passes through superior orbital fissure

maxillary V2

passes through foramen rotundum

mandibular V3

passes through the foramen ovale

trigeminal nerve test

running cotton ball (dry or wet) along the three divisions in order to see if it is felt in those areas and to detect temperature change, and putting pressure against the jaw to innervate the chewing muscles

abducens nerve VI

fibers from inferior pons enter orbits via superior orbital fissures, primarily a motor nerve, innervating lateral rectus muscle

facial nerve VII

chief motor nerves of face with 5 major branches, motor functions include facial expressions, parasympathetic impulses to lacrimal and salivary glands, sensory function from anterior two-thirds of tongue

facial nerve test

have test subject make weird faces like lifting eyebrows, puffing out cheeks, smiling, etc to look for symmetry

vestibulocochlear nerve VIII

afferent fibers from hearing receptors and equilibrium receptors pass from inner ear and enter brain stem at pons-medulla border, mostly sensory function, small motor component for adjustment of sensitivity of receptors

vestibulocochlear test

moving a ticking clock around someone to see if they can tell where it is, or tuning fork tests and balance tests like standing on one foot

glossopharyngeal nerve IX

fibers from medulla leave skull via jugular foramen and run to throat, motor functions: innervate part of tongue and pharynx for swallowing, provide parasympathetic fibers to parotid salivary glands, sensory functions: fibers conduct taste and general sensory impulses from pharynx and posterior tongue, and impulses from carotid chemoreceptors and baroreceptors

vagus nerve X

only cranial nerves that extend beyond head and neck region, fibers from medulla exit skull via jugular foramen, most motor fibers are parasympathetic fibers that help regulate activities of heart, lungs, and abdominal viscera, sensory fibers carry impulses from thoracic and abdominal viscera, baroreceptors, chemoreceptors, and taste buds of posterior tongue and pharynx

accessory nerve XI

formed from ventral rootlets from C1-C5 region of spinal cord, rootlets pass into cranium via each foramen magnum, exit skull via jugular foramina to innervate trapezius and sternocleidomastoid muscles

accessory nerve test

can be tested by applying pressure to someone’s shoulders to see if they can resist that, and seeing if they can resist your hand on their neck by rotating their head

hypoglossal nerve XII

fibers from medulla exit skull via hypoglossal canal, innervate extrinsic and intrinsic muscles of the tongue that contribute to swallowing and speech

hypoglossal nerve test

have someone stick their tongue out and see if it curves, see if they have trouble speaking and swallowing

somatic reflexes

activate skeletal muscle

autonomic (visceral) reflexes

activate visceral effectors (smooth or cardiac muscle or glands)

the stretch reflex

maintains muscle tone in large postural muscles, and adjusts it reflexively, causes muscle contraction in response to increased muscle length

the flexor reflex

initiated by painful stimulus, causes automatic withdrawal of threatened body part, ipsilateral and polysynaptic, brain can override

crossed extensor relfex

occurs in weight bearing limbs to maintain balance, consists of ipsilateral withdrawal reflex and contralateral extensor reflex, stimulated side withdrawn - contralateral side extended

superficial reflexes

elicited by gentle cutaneous stimulation, depend on upper motor pathways and cord-level reflex arcs, ex: plantar reflex and abdominal reflex

plantar reflex

test integrity of cord from L4 through S2, stroke lateral aspect of sole of foot, response is downward flexion of toes, abnormal response = Babinski’s sign

abdominal reflexes

test integrity of cord from T8 through T12, cause contraction of abdominal muscles and movement of umbilicus in response to stroking of skin, absent when corticospinal tract lesions present

fibrous layer of eye

outermost layer, dense avascular connective tissue, has two regions: sclera and cornea

sclera

protects and shapes eyeball, anchors extrinsic eye muscles, continuous with dura mater of brain posteriorly

cornea

bends light as it enters eye, sodium pumps of corneal endothelium on inner face help maintain clarity, numerous pain receptors contribute to blinking and tearing reflexes

vascular layer of eye (uvea)

middle pigmented layer, has three regions: choroid, ciliary body, and iris

choroid

posterior portion of uvea, supplies blood to all layers of eyeball, brown pigment absorbs light to prevent light scattering and visual confusion

ciliary body

ring of tissue surrounding lens, smooth muscle bundles control lens shape, capillaries of processes secrete fluids, zonule holds lens in position

iris

colored part of the eye

pupil

central opening that regulates amount of light entering the eye

inner layer of eye (retina)

originates as out pocketing of brain, delicate two-layered membrane

outer pigmented layer of retina

singe cell thick lining, absorbs light and prevents scattering, stores vitamin A

inner neural layer of retina

transparent, composed of photoreceptors, bipolar cells, and ganglion cells

optic disc (blind spot)

site where optic nerve leaves the eye, lacks photoreceptors

types of photoreceptors

rods and cones

rods

dim light, peripheral vision receptors, more numerous, more sensitive to light, no color vision or sharp images

cones

vision receptors for bright light, high-resolution color vision, macula lutea exactly at posterior pole

posterior segment of eye

contains vitreous humor that transmits light, supports posterior surface of lens, holds neural layer of retina firmly against pigmented layer

anterior segment of eye

contains aqueous humor, supplies nutrients and oxygen mainly to lens and cornea but also to retina and removes wastes

glaucoma

blocked drainage of aqueous humor increases pressure and causes compression of retina and optic nerve, leads to blindness

lens

biconvex, transparent, flexible, and avascular, changes shape to precisely focus light on retina, has two regions: epithelium and fibers

cataracts (clouding of lens)

consequence of aging, diabetes, mellitus, heavy smoking, frequent exposure to intense sunlight

focusing for close vision

accommodation/changing of lens shape, constriction of pupils, convergence of eyeballs

presbyopia

loss of accommodation over age 50

myopia

nearsightedness, eyeball too long, corrected with concave lens

hyperopia

farsightedness, eyeball too short, corrected with convex lens

astigmatism

unequal curvatures in different parts of cornea or lens, corrected with cylindrically ground lenses or laser procedures

sweet taste sensation

sugars, saccharin, alcohol, some amino acids, some lead salts

sour taste sensation

hydrogen ions in solution

salty taste sensation

metal ions (inorganic salts)

bitter taste sensation

alkaloids such as quinine and nicotine, aspirin

umami taste sensation

amino acids glutamate and aspartate

to be tasted, chemicals must:

be dissolved in saliva, diffuse into taste pore, contact gustatory hairs

external (outer) ear and middle ear (tympanic cavity)

hearing only

internal (middle) ear

hearing and equilibrium

auricle (pinna)

composed of helix and earlobe, funnels sound waves into auditory canal

external acoustic meatus (auditory canal)

short, curved tube lined with skin bearing hairs, sebaceous glands, and ceruminous glands, transmits sound waves to eardrum

tympanic membrane (eardrum)

boundary between external and middle ears, connective tissue membrane that vibrates in response to sound, transfers sound energy to bones of middle ear

middle ear (tympanic cavity)

small, air filled, mucosa-lined cavity in temporal bone, flanked laterally by eardrum, flanked medially by bony wall

ear ossicles

three small bones in tympanic cavity: malleus, incus, and stapes, suspended by ligaments and joined by synovial joints, transmit vibratory motion of eardrum to oval window

maculae

sensory receptors for static equilibrium, monitor the position of head in space, necessary for control of posture, contain supporting cells and hair cells

crista ampullares

sensory receptor for rotational acceleration, has supporting cells and hair cells that extend into gel-like mass called ampullary cupula

vestibular nystagmus

strange eye movements during and immediately after rotation, eyes continue in direction of spin then jerk rapidly in the opposite direction as rotation ends