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bio 201 test 4
special senses
44
Biology
Undergraduate 2
05/04/2010

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Term
modality- classification of receptors
Definition
chemoreceptors, thermoreceptors, nociceptors,
mechanoreceptors and photoreceptors
Term
classification of receptors by origin of stimuli
Definition
interoceptors = detect internal stimuli
– proprioceptors = sense position & movements of body
– exteroceptors = sense stimuli external to body
Term
classification of receptors by distribution
Definition
– general (somesthetic) sense --- widely distributed
– special senses --- limited to head
Term
Pain
Definition
Receptors make us conscious of tissue injuries
• Found in all tissues except the brain
Term
fast pain
Definition
travels in myelinated fibers at 30 m/sec
– sharp, localized, stabbing pain perceived with injury
Term
slow pain
Definition
travels unmyelinated fibers at 2 m/sec
– longer-lasting, dull, diffuse feeling
Term
Somatic pain
Definition
arises from skin, muscles, joints
Term
Visceral pain
Definition
from stretch, chemical irritants or
ischemia of viscera (poorly localized)
Term
bradykinin, histamine, prostaglandin
Definition
Injured tissues release chemicals – stimulate
pain fibers
Term
Referred Pain
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
Term
CNS Modulation of Pain
Definition
Intensity of pain is affected by state of mind
• Receptor sites for opium, morphine & heroin were
investigated & endogenous opioids discovered
Term
Spinal gating stops pain signals at dorsal horn
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
Term
The Chemical Sense -- Taste
Definition
Gustation is the sensation of taste resulting from
the action of chemicals on the taste buds
Term
Lingual papillae – tongue bumbs
Definition
circumvallate
• at rear of tongue
• contains 1/2 of taste buds
• largest
– fungiform
• scattered throughout
tongue surface
Term
Physiology of Taste
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.
Term
flavors on tounge
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
Term
The Chemical Sense -- Smell
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
Term
Olfactory Epithelial Cells
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
Term
Physiology of smell
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
Term
Bulb cells form the axons of the olfactory tracts
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
Term
The Nature of Sound
Definition
• Sound is any audible vibration of molecules
• Vibrating object pushes air molecules into zones
of compression separated by zones of rarefaction
Term
pitch
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)
Term
loudness
Definition
Loudness is perception of intensity of sound energy
– how much the air molecules are compressed in decibels
Term
Ear ossicles span tympanic cavity
Definition
malleus attached to eardrum, incus, stapes attached to
membranous oval window of inner ear
– spapedius & tensor tympani muscles attach to ossicles
Term
Middle Ear
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
Term
Physiology of Hearing -- Middle Ear
Definition
Eardrum vibrates quite easily
Protection of cochlea by muscle contraction in
response to loud noises
Term
Stimulation of Cochlear Hair Cells
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
Term
Sensory Coding
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
Term
Equilibrium
Definition
• Control of coordination and balance
• Receptors in vestibular apparatus
Term
• Dynamic equilibrium
Definition
is perception of moving
forward
Term
Static equilibrium
Definition
is per ception of head
orientation
– perceived by macula
Term
The Saccule and Utricle
Definition
containing macula
– patch of hair cells with their stereocilia & one
kinocilium buried in a gelatinous otolithic membrane
weighted with granules called otoliths
Term
Crista ampullaris
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
Term
Eyelids (palpebrae)
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
Term
Eyebrows
Definition
provide facial expression, protection
from glare & perspiration
Term
tunics
Definition
• Tunica fibrosa = sclera and cornea (blue)
• Tunica vasculosa = choroid, ciliary body, & iris
(pink)
• Tunica interna = retina (yellow)
Term
The Optical Apparatus
Definition
Series of transparent structures that bend or
refract light rays to focus them on the retina
Term
Aqueous Humor
Definition
Serous fluid produced by ciliary body that flows
from posterior chamber through pupil to anterior
chamber -- reabsorbed into canal of Schlemm
Term
The Neural Apparatus
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
Term
Hyperopia
Definition
is farsighted (eyeball too short)
– correct with convex lenses
Term
Myopia
Definition
is nearsighted (eyeball too long)
– correct with concave lenses
Term
Photoreceptors
Definition
cells are next layer
– derived from stem cells that produced
ependymal cells
Term
Rod cells (night vision)
Definition
outer segment is stack of coinlike
membranous discs studded with rhodopsin
pigment molecules
Term
Cone cells (color vision in bright light)
Definition
outer segment tapers to a point
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