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Neurology final DCOM

Terms

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Tactile Receptor
Corpuscles of Touch
Meissner corpuscles
Capsule surrounds mass of dendrites in dermal papillae of hairless skin

Fine touch, pressure, and slow vibrations
Tactile Receptors
Hair root plexuses
Free nerve endings wrapped around hair follicles in skin

Touch
Tactile Receptors

Type I cutaneous mechanoreceptors
(Tactile or Merkel disc)
Saucer-shaped free nerve endings make contact with Merkel cells in epidermis

Touch and pressure
Tactile Receptors

Type II cutaneous mechanoreceptors
(Ruffini corpuscles)
Elongated capsule surrounds dendrites deep in dermis and in ligaments and tendons

Stretching of skin
Tactile Receptors

Itch and tickle receptors
Free nerve endings and lamellated corpuscles in skin and mucous membranes

Itching and tickling
Thermoreceptors

Warm receptors and cold receptors
Free nerve endings in skin and mucous membranes of mouth, vagina, and anus

Warmth or cold
Pain Receptors

Nociceptors
Free nerve endings in every tissue of the body except the brain

Pain
Proprioceptors

Muscle spindles
Sensory nerve endings wrap around central area of encapsulated intrafusal muscle fibers within most skeletal muscles.

Muscle length
Proprioceptors

Tendon organs
Capsule encloses collagen fibers and sensory nerve endings at junction of tendon and muscle

Muscle tension
Proprioceptors

Joint kinesthetic receptors
Lamellated corpuscles, Ruffini corpuscles, tendon organs, and free nerve endings

Joint position and movement
Microscopic features of sensory receptors

Free nerve endings
Bare dendrites associated with pain, thermal, tickle, itch, and some touch sensations
Microscopic features of sensory receptors

Encapsulated nerve endings
Dendrites enclosed in a connective tissue capsule, such as a corpuscle of touch
Microscopic features of sensory receptors

Separate cells
Receptor cell synapses with first-order neurons; located in the retina of the eye (photoreceptors), inner ear (hair cells) and taste buds of the tongue (gustatory receptor cells)
Receptor Location and Activating Stimuli

Exteroceptors
Located at or near body surface; sensitive to stimuli originating outside body; provide information about external environment; convey visual, smell, taste, touch, pressure, vibration, thermal, and pain sensations
Receptor Location and Activating Stimuli

Interoceptors
Located in blood vessels, visceral organs, and nervous system;provide information about internal environment; impulses produced usually are not consciously perceived by occasionally may be felt as pain or pressure
Receptor Location and Activating Stimuli

Proprioceptors
Located in muscles, tendons, joints, and inner ear; provide information about body position, muscle length and tension, position and motion of joints, and equilibrium (balance)
Type of stimulus detected

Mechanoreceptors
Detect mechanical pressure;provide sensations of touch, pressure, vibrations, proprioception, and hearing and equilibrium; also monitor stretching of blood vessels and internal organs
Type of stimulus detected

Thermoreceptors
Detect changes in temperature
Type of stimulus detected

Nociceptors
Respond to stimuli resulting from physical or chemical damage to tissue
Type of stimulus detected

Photoreceptors
Detect light that strikes the retina of the eye
Type of stimulus detected

Chemoreceptors
Detect chemicals in mouth (taste), nose (smell), and body fluids
Type of stimulus detected

Osmoreceptors
Sense the osmotic pressure of body fluids
Process of sensation
1. stimulation of sensory receptor
2. transduction of the stimulus
3. generation of impulse
4. integration of sensory input
Somatic sensory pathways

1. first order neurons
conduct impulses from the somatic receptors into the brain stem or spinal cord. From the face, mouth, teeth, and eyes, somatic sensory impulses propagate along cranial nerves into the brain stem. From the neck, body, and posterior aspect of the head, somatic sensory impulses propogate along spinal nerves into the spinal cord
Somatic Sensory pathways

2. Second-order neurons
conduct impulses from the brain stem and spinal cord to the thalamus. Axons decussate in the brain stem or spinal cord before ascending to the ventral posterior nucleus of the thalamus. Thus, all somatic sensory information from one side of the body reaches the thalamus on the opposite side.
Somatic sensory pathways

3. Third-order neurons
conduct impulses from the thalamus to the primary somatosensory area of the cortex on the same side.
stereognosis
ability to recognize the size, shape, and texture of an object by feeling it

(reading Braille, identifying a paperclip by feeling it)
Proprioception
awareness of the precise position of body parts, and kinesthesia is the awareness of directions of movement. Proprioceptors also allow weight descrimination, the ability to assess the weight of an object.
Vibratory sensations
arise when rapidly fluctuating touch stimuli are present
circadian rhythm
a cycle of active and nonactive periods in organisms determined by internal mechanisms and repeating about every 24 hours
Reticular activating system (RAS)
a portion o the reticular formation that has many ascending connections with the cerebral cortex; when this area of the bran stem is active, nerve impulses pass to the thalamus and widespread areas of the cerebral cortex, resulting in generalized alertness or arousal from sleep
arousal
awakening from sleep, a response due to stimulation of the reticular activating system (RAS)
consciousness
a state of wakefulness in which an individual is fully alert, aware, and oriented, partly a s a result of feedback between the cerebral cortex and reticular activating system
Stage 1 sleep
transition stage between wakefulness and sleep that normally lasts 1-7 minutes
Stage 2 sleep
light sleep
the first stage of true sleep
fragments of dreams,
eyes may slowly roll from side to side,
sleep spindles
Stage 3 sleep
moderately deep sleep
body temp and BP decrease
sleep spindles and larger, lower frequency waves
Stage 4 sleep
slow-wave sleep, deepest level of sleep
REM sleep
rapid eye movement
stage of sleep in which dreaming occurs, lasting for 5--10 minutes during the sleep cycle
vestibular branch of the vestibulocochlear nerve (cranial nerve VIII)
ampullary, utricular, and saccular nerves
vestibular ganglia
where cell bodies of the sensory neurons are located
cochlear duct
the membranous cochlea consisting of a spirally arranged tube enclosed in the bony cochlea and lying along its outer wall
also called the scala media
spiral organ or organ or Corti
the organ of hearing, consisting of supporting cells and hair cells that rest on the basilar membrane and extend into the endolymph of the cochlear duct
semicircular ducts
the portions of the membranous labyrinth that lie inside the bony semicircular canals, communicate with the utricle of vestibule
ampulla
the dilated portion of each semicircular duct
crista
a small elevation in the ampulla
contains a group of hair cells and supporting cells covered by a mass of gelatinous material called tha cupula
gustation
sense of taste
name the five primary taste sensations
sour, sweet, bitter, salty, and umami (meaty or savory)
olfaction
sense of smell
three types of epitheleal cells of the taste bud
1. supporting cells

2. gustatory receptor cells

3. basal cells
vallate papillae
for an inverted V-shaped row at the back of the tongue
fungiform papillae
mushroom shaped elevations scattered over the entire surface of the tongue that contain about five taste buds each
Foliate papillae
located in small trenches on the lateral margins of the tongue but most of their taste buds degenerate in early childhood
filiform papillae
over the entire surface of the tongue

pointed, threadlike structures contain tactile receptors but no taste buds
tastants
chemicals that stimulate gustatory receptor cells
sites of taste transduction
plasma membrane of gustatory hair cells
hyposmia
reduced ability to smell
external ear
consists of auricle, external aurditory canal, and eardrum
auricle
Pinna
flap of elastic cartilage shaped like the flared end of a trumpet and covered by skin
lobule
inferior portion of the auricle
helix
rim of the auricle
external auditory canal
a curved tube about 2.5 cm long that lies in the temporal bone and leads from the auricle to the eardrum.
tympanic membrane
eardrum
a thin, semitransparent partition between the external auditory canal and middle ear
ceruminous glands
excrete ear wax
cerumen
ear wax
middle ear
auditory ossicles (malleus, incus, stapes)
oval window, round window, secondary tympanic membrane, Eustachean tube
auditory ossicles
extend across middle ear and attached to it by ligaments
three smallest bones in the body
incus, malleus, stapes
oval window
base of footplate of the stapes
round window
below the oval window, enclosed by a membrane called the secondary tympanic membrane
secondary tympanic membrane
membrane which encloses the round window
Eustachean tube
(auditory tube)
connects the middle ear with the nasopharynx.
Internal ear
(labyrinth)
bony labyrinth, membranous labyrinth, perilymph, endolymph, vestibule,
utricle, semicircular canals, semicircular ducts
bony labyrinth
series of cavities in the temporal bone divided into three areas

1) semicircular canals, 2) the vestibule, and 3) the cochlea
perilymph
fluid which is chemically similar to cerebrospinal fluid and surrounds the membranous labyrinth
membranous labyrinth
a series of sacs and tubes inside the bony labyrinth and having the same general form
endolymph
extracellular fluid lining the membranous labyrinth
vestibule
oval central portion of the bony labyrinth which contains the utricle and saccule
semicircular canals
three bony canals projecting superiorly and posteriorly from the vestibule
acoustic
pertaining to sound or to the sense of hearing
audiology
a branch of science dealing with hearing, especially the therapy of individuals having impaired hearing
conjunctiva
mucous membrane which lines eyelids and coats the front portion of the eyeball
equilibrium
state of balance or rest; condition in which contending forces are equal
hyperopia
light rays come to a focus behind the retina
farsightedness
labyrinth
intrcate communicating passages of the internal ear
myopia
light rays come to a focus in front of the retina

nearsightedness
ophthalmologist
a physician who specializes in the medical and surgical treatment of disorders of the eye
Ophthalmology
the science dealing with the eye and its diseases
Optician
a person skilled in grinding lenses and fitting glasses
Optometrist
a person specially trained and licensed to examine the eyes for vision problems and to prescribe and adapt lenses to correct vision problems
Otology
the science dealing with the ear, its function, and its diseases
Otorhinolaryngology
the science dealing with the ear, nose, and larynx and their funcitons and diseases
otolaryngology
referred pain
pain seeming to arise in an area other than its origin
sense
the general faculty by which conditions inside or outside the body are perceived
somatic pain
pain pertaining to structures of the body wall
tactile
perceptible to the touch
turbinate
one of three scroll-like bones which projects medially from the lateral wall of the nasal cavity; also called a nasal concha
receptor
specialized nerve ending which receives a stimulus
sensory nerve
the pathway which carries impulses from the receptor to the brain
sensory center
area of the brain which interprets the impulses as senses
sclera
outer layer of the eyeball
tough white fibrous protective layer
anterior portion is known as the cornea
cornea
anterior portion of the sclera
lies over the colored part (iris) of the eye
is transparent
contains no blood vessels
choroid coat
middle layer of the eye
contains blood vessels that supply the eye
anterior portion--Iris, ciliary body, suspensory ligament
Iris
the colored part of the eye, donut-shaped sphincter muscle, which attaches to the ciliary body
regulates the size of the pupil and therefore the amount of light entering the eye
Ciliary body
a flattened muscular ring that alters the shape of the iris
changes the focus of the lens and adjusts the eye for distant and close up vision
suspensory ligament
the structure that hold the lens in place
Retina
the camera of the eye
innermost, incomplete coat of the eyeball
specialized nerve tissue for the reception of light
contains tin receptors-rod and cones-for vision
aqueous humor
watery, transparent liquid that circulates through the anterior cavity of the eye
vitreous humor
clear jelly-like fluid in the posterior cavity of the eye which fills the vitreous body
extrinsic eye muscles
those that attach to the outside of the eyeball and to the bones of the orbit
voluntary
straight-superior rectus, inferior rectus, medial rectus, lateral rectus
oblique-superior oblique, inferior oblique
intrinsic eye muscles
inside the eyeball itself
involuntary
iris and ciliary body
eyebrows and eyelashes
give protection against foreign objects entering the eye;
small glands at the base of the eyelashes also secrete a lubricating fluid
Eyelids
(palpebrae)
blink as a result of sensory stimuli to keep out foreign objects
volutary musche and skin
lined with conjuntiva
openings between called papebral fissure
angles known as the canthus
lacrimal glands and ducts
secrete tears which keeep the anterior surface of the eye moist and free; the size of small almonds and located in the upper, outer portion of each orbit; masolacrimal ducts are small tubees extending from the lacrimal sacs into the nose to drain tears from the ey into the nose
Olfactory receptors are what type?
first order, bi-polar neuron
Where are the hearing receptors found?
internal ear; cochlea
what is the range of human hearing?
20-20,000 Hz
List in correct order the parts through which light passes as it enters the eye
cornea, pupil, lens, retina
vascular tunic of the eye
choroid, ciliary body, and iris
Rod cells contain what pigment
rhodopsin
The auditory nerve pathways carry impulses to the auditory cortices in the ?
temporal lobes
Where are the auditory ossicle located?
middle ear
Olfactory receptors are best described as ?
columnar epithelial cells
meninges on the surface of the brain
example of pain receptors
the lens of the eye thickens when the ?
suspensory ligament pulls on the lens capsule
Blowing the nose improperly may cause an infection within the auditory tube to spread into where?
internal ear
What does the disorder gluacoma do to the eye?
Increases intracellular pressure; results in blindness
What is anosmia?
lack of smell
What would cause of form of conductive deafness?
damage to auditory tubes
Interference with vision and the feeling of numbness in the limbs experienced by a person with a migraine is probably caused by ?
vasodialation of cerebral vessels
Treatment for a cataract usually involves removal of the ?
lens
Where is the highest density of somatic receptors?
tip of tongue, lips, and fingertips
sensation
the conscious or subconscious awareness of external or internal stimuli
perception
the conscious awareness and the interpretation of meaning to sensations

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