Term
| modality- classification of receptors |
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Definition
chemoreceptors, thermoreceptors, nociceptors,
mechanoreceptors and photoreceptors |
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Term
| classification of receptors by origin of stimuli |
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Definition
interoceptors = detect internal stimuli
– proprioceptors = sense position & movements of body
– exteroceptors = sense stimuli external to body |
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Term
| classification of receptors by distribution |
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Definition
– general (somesthetic) sense --- widely distributed
– special senses --- limited to head |
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Term
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Definition
Receptors make us conscious of tissue injuries
• Found in all tissues except the brain |
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Term
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Definition
travels in myelinated fibers at 30 m/sec
– sharp, localized, stabbing pain perceived with injury |
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Term
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Definition
travels unmyelinated fibers at 2 m/sec
– longer-lasting, dull, diffuse feeling |
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Term
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Definition
| arises from skin, muscles, joints |
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Term
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Definition
from stretch, chemical irritants or
ischemia of viscera (poorly localized) |
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Term
| bradykinin, histamine, prostaglandin |
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Definition
Injured tissues release chemicals – stimulate
pain fibers |
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Term
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Definition
Misinterpreted pain
– brain “assumes” visceral pain is coming from skin
– ie. heart pain felt in shoulder or arm because both send
pain input to spinal cord segments T1 to T5 |
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Term
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Definition
Intensity of pain is affected by state of mind
• Receptor sites for opium, morphine & heroin were
investigated & endogenous opioids discovered |
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Term
| Spinal gating stops pain signals at dorsal horn |
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Definition
– descending analgesic fibers (midbrain central gray area)
• secrete inhibitory enkephalins onto dorsal horn pain fibers
– dorsal horn fibers inhibited by input from touch fibers |
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Term
| The Chemical Sense -- Taste |
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Definition
Gustation is the sensation of taste resulting from
the action of chemicals on the taste buds |
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Term
| Lingual papillae – tongue bumbs |
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Definition
circumvallate
• at rear of tongue
• contains 1/2 of taste buds
• largest
– fungiform
• scattered throughout
tongue surface |
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Term
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Definition
• To be tasted, molecules must dissolve in saliva
• 5 primary sensations: salty, sweet, sour, biter, and
umami (taste of amino acids such as MSG)
• Taste is also influenced by food texture, aroma,
temperature, and appearance. |
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Term
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Definition
• Sweet tastes concentrated on tip of tongue, salty & sour on
lateral margins of tongue & bitter at rear
• Sugars & umami flavors bind to receptors & activate 2nd
messenger systems; sodium & acids penetrate cells &
depolarize them |
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Term
| The Chemical Sense -- Smell |
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Definition
Receptor cells for olfaction
form olfactory mucosa
– smell is highly sensitive
• more so in women than men
– distinguish as many as
10,000 odors |
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Term
| Olfactory Epithelial Cells |
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Definition
neurons with 20 cilia
called olfactory hairs
• binding sites for odor
molecules in thin layer
of mucus
– axons pass through
cribriform plate
– survive 60 days |
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Term
|
Definition
Odor molecules must be volatile
– bind to a receptor on an olfactory hair triggering the
production of a second messenger
– opens the ion channels & creates a receptor potential
• Receptors adapt quickly due to synaptic
inhibition in the olfactory bulbs |
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Term
| Bulb cells form the axons of the olfactory tracts |
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Definition
– lead to temporal lobe, amygdala, hypothalamus
• emotional responses to odors
• cough, salivate, sneeze or vomit in response to odors
– cerebral cortex sends feedback to bulb cells
• changing quality & significance of odors when hungry |
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Term
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Definition
• Sound is any audible vibration of molecules
• Vibrating object pushes air molecules into zones
of compression separated by zones of rarefaction |
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Term
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Definition
The frequency at which parts of the ear vibrate give us
sense of pitch (high or low pitched sounds)
– hearing range is 20 - 20,000 Hz (cycles/sec) |
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Term
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Definition
Loudness is perception of intensity of sound energy
– how much the air molecules are compressed in decibels |
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Term
| Ear ossicles span tympanic cavity |
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Definition
malleus attached to eardrum, incus, stapes attached to
membranous oval window of inner ear
– spapedius & tensor tympani muscles attach to ossicles |
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Term
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Definition
• Air-filled cavity in temporal bone separated from air
outside the head by tympanic membrane
– 1 cm in diameter, slightly concave, vibrates freely
• Tympanic cavity continuous with mastoid air cells
• Tympanic cavity filled with air by auditory tube
(eustachian tube) connected to nasopharynx |
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Term
| Physiology of Hearing -- Middle Ear |
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Definition
Eardrum vibrates quite easily
Protection of cochlea by muscle contraction in
response to loud noises |
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Term
| Stimulation of Cochlear Hair Cells |
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Definition
Sound is produced by vibration of ossicles and
then vibration of basilar membrane under hair cells
• Can happen as often as 20,000 time per second |
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Term
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Definition
Loudness produces more vigorous vibrations &
excites more hair cells over a larger area
Determination of pitch depends on which part of
basilar membrane is vibrated at peak amplitude of
standing wave |
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Term
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Definition
• Control of coordination and balance
• Receptors in vestibular apparatus |
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Term
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Definition
is perception of moving
forward |
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Term
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Definition
is per ception of head
orientation
– perceived by macula |
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Term
|
Definition
containing macula
– patch of hair cells with their stereocilia & one
kinocilium buried in a gelatinous otolithic membrane
weighted with granules called otoliths |
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Term
|
Definition
consists of hair cells buried in a mound
of gelatinous membrane (one in each duct)
• Orientation of ducts causes different ducts to be stimulated
by rotation in different planes |
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Term
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Definition
block foreign objects, help with sleep,
blink to moisten
– meet at corners (commissures)
– consist of orbicularis oculi muscle &
tarsal plate covered with skin outside
& conjunctiva inside
– tarsal glands secrete oil that reduces
tear evaporation
– eyelashes help keep debris from the eye |
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Term
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Definition
provide facial expression, protection
from glare & perspiration |
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Term
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Definition
• Tunica fibrosa = sclera and cornea (blue)
• Tunica vasculosa = choroid, ciliary body, & iris
(pink)
• Tunica interna = retina (yellow) |
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Term
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Definition
Series of transparent structures that bend or
refract light rays to focus them on the retina |
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Term
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Definition
Serous fluid produced by ciliary body that flows
from posterior chamber through pupil to anterior
chamber -- reabsorbed into canal of Schlemm |
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Term
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Definition
Neural apparatus includes the retina & optic
nerve
• Retina forms as an outgrowth of the brain
– attached only at optic disk where optic nerve begins
and at ora serrata (its anterior margin)
– pressed against rear of eyeball by vitreous body
• Detached retina
– blow to head or lack of sufficient vitreous body
– blurry areas in field of vision
– leads to blindness due to disruption of blood supply |
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Term
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Definition
is farsighted (eyeball too short)
– correct with convex lenses |
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Term
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Definition
is nearsighted (eyeball too long)
– correct with concave lenses |
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Term
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Definition
cells are next layer
– derived from stem cells that produced
ependymal cells |
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Term
|
Definition
outer segment is stack of coinlike
membranous discs studded with rhodopsin
pigment molecules |
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Term
| Cone cells (color vision in bright light) |
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Definition
| outer segment tapers to a point |
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