Exam 2: Ch 10 Sensory Physiology Flashcards
1
Q
Sensory receptors transduce (=change) environmental information into
A
APs – the common language of NS
2
Q
Each type of sensory receptor responds
A
a particular modality (=form of info, e.g. sound, light, pressure)
3
Q
Different modalities are perceived as different because
A
because of CNS pathways they stimulate
4
Q
2 classification schemes for sensory receptors
A
1. Structural
2. Functional
5
Q
1. Structural
A
simple dendritic endings of neurons
• Free (pain, temperature)
• Encapsulated within non-neural structures (pressure) or modified epithelia (taste)
6
Q
2. Functional
A
Functional classification of sensory receptors groups them according to type of stimulus they transduce
7
Q
Functional classification of sensory
A
- chemoreceptors
- photoreceptors
- thermoreceptors
- mechanoreceptors
- nociceptors
- proprioceptors
8
Q
Chemoreceptors
A
sense chemical stimuli (taste buds, olfactory receptors)
9
Q
Photoreceptors
A
transduce light (rods and cones)
10
Q
Thermoreceptors
A
respond to temperature changes (heat and cold)
11
Q
Mechanoreceptors
A
respond to deformation of their cell membrane (touch, pressure, hair cells of inner ear)
12
Q
Nociceptors
A
respond to intense stimuli by signaling pain
13
Q
Proprioceptors
A
signal positional information of body parts (joint receptors, golgi tendons, muscle spindles)
14
Q
Sensory receptors can also be categorized according to location:
A
- Cutaneous receptors
- Special sense receptors
15
Q
Cutaneous receptors
A
are near an epithelial surface (respond to touch, pressure, temperature or pain)
16
Q
Special sense receptors
A
are part of a sensory organ (hearing, sight, equilibrium)
17
Q
Sensory Receptor Responses
A
Tonic receptors
Phasic receptors
18
Q
Tonic receptors
A
respond at constant rate as long as stimulus is applied (e.g. pain)
19
Q
Phasic receptors
A
respond with burst of activity but quickly reduce firing rate to constant stimulation
20
Q
Which sensory receptor is Responsible for sensory adaptation
A
Phasic receptors
- • e.g. smell and touch
21
Q
Generator (receptor) potentials
A
sensory receptor equivalents of EPSPs
22
Q
Generator (receptor) potentials is produced why
A
in response to adequate stimulus
23
Q
Generator (receptor) potentials are proportional to
A
stimulus intensity
• NOTE: After threshold is reached, intensity is coded for by AP frequency
24
Q
In phasic receptors the generator potential
A
adapts to a constant stimulus & quickly diminishes in amplitude
25
In tonic receptors, generator potential
does not adapt to a constant stimulus
26
Cutaneous sensations include the following
- touch
- pressure
- heat
- cold
- pain
- ruffini endings & merkel's discs
27
Cutaneous sensations are mediated by
free & encapsulated nerve endings
28
heat
mediated by free nerve endings; located deeper in dermis
29
heat elicits pain thru
capsaicin receptors; capsaicin is "hot" chemical in chili peppers
30
cold
mediated by free nerve endings; located in upper dermis
31
pain
- mediated by free nerve endings called nociceptors
| • Use glutamate & substance P as NTs; substance P called "pain NT"
32
Ruffini endings & Merkel's discs
are slow-adapting, expanded free nerve endings that mediate touch
33
Encapsulated nerve endings
- mediate touch, pressure
| - adapt quickly and include Meisner's & Pacinian corpuscles
34
Two-point touch threshold
Is minimum distance at which 2 points of touch can be perceived as separate
35
Two-Point Touch Threshold Measure of
of tactile acuity or distance between receptive fields (area of skin whose stimulation results in changes in the firing rate of a neuron)
36
Lateral Inhibition
Is CNS process that sharpens sensation
| Sensory neurons at center of stimulation area inhibit more lateral neurons
37
Lateral Inhibition eg.
- when blunt object touches skin sensory neurons in center are stimulated more than outer ones & inhibit them
- Object perceived as single touch with well-defined borders
38
Taste and smell receptors are
are exteroceptors because respond to chemicals in external environment
39
Interoceptors
respond to chemicals in internal environment
40
Taste/Gustation Detects
sweet, sour, salty, bitter, & amino acids (umami)
41
Taste receptor cells are
modified epithelial cells
42
How many taste receptors in each taste bud?
50-100 are in each taste bud
43
Salty & sour
do not have receptors
| act by passing through channels
44
Sweet & bitter
- have receptors
| - act thru G-proteins
45
Smell (olfaction) receptors
located in olfactory epithelium at top of nasal cavity
46
Olfactory apparatus consists of
receptor cells, supporting cells, & basal cells
47
Receptor cells of olfactory apparatus are
are bipolar neurons that send axons to olfactory bulb
48
Basal cells of olfactory apparatus are
are stem cells that produce new receptor cells every 1-2 months
49
supporting cells of olfactory apparatus
contain detoxifying enzymes
50
Odor molecules bind to
receptors & act through G-proteins
51
Ears & Hearing; Vestibular Apparatus
provides sense of equilibrium orientation to gravity
52
inner ear
Vestibular apparatus & cochlea
53
Vestibular apparatus consists of
otolith organs (utricle & saccule)
| semicircular canals
54
Sensory structures of the vestibular apparatus are located with in
membranous labyrinth
55
membranous labyrinth is filled with
endolymph = fluid similar to intracellular fluid
56
membranous labyrinth is located within
bony labyrinth
57
Utricle and saccule provide
info about linear acceleration
58
linear acceleration
changes in velocity (acceleration and deceleration) when moving horizontally or vertically)
59
Semicircular canals,
- oriented in 3 planes,
| - give sense of angular (rotational) acceleration
60
Vestibular Apparatus
| - Hair cells
- modified epithelial cells
are receptors for hearing and equilibrium
each contains 20-50 hair-like extensions called stereocilia
61
stereocilia
* processes with filaments of protein
| * 1 of these extentions (longer one) = kinocilium (cilia)
62
When stereocilia are bent toward kinocilium,
hair cell depolarizes & releases NT that stimulates CN VIII
63
When stereocilia are bent in the opposite direction
- hair cell hyperpolarizes
In this way, frequency of APs in hair cells carries information about movements that cause the hair cell processes to move
64
Otolith organs
Utricle & Saccule
65
Utricle and saccule
- each have a macula
patch of specialized epithelium containing hair and support cells
Hair cell extensions are embedded in gelatinous otolithic membrane
66
gelatinous otolithic membrane
contains calcium carbonate crystals (=otoliths) that resist change in movement
67
Utricle =
sensitive to horizontal acceleration
| Hairs pushed backward during forward acceleration
68
Saccule
sensitive to vertical acceleration
| Hairs pushed upward when person descends
69
Semicircular canals
= provide information about rotational acceleration
project in 3 different planes
each contains a semicircular duct
70
At base of Semicircular canals
is crista ampullaris where sensory hair cells are located
71
Hair cell processes are embedded in
gelatenous membrane = cupula of crista ampullaris with higher density than endolymph
72
when endolymph moves
cupula moves and sensory processes bend in opposite direction of angular acceleration
73
Vestibular nystagmus
involuntary oscillations of eyes
occurs when spinning person stops
eyes continue to move in direction opposite to spin, then jerk rapidly back to midline
74
Vertigo
is loss of equilibrium
75
Vertigo
| natural response of vestibular apparatus or pathological may be caused by
anything that alters firing rate of CN VIII
| Ex: often caused by viral infection
76
Outer Ear
| Sound waves funneled by
by pinna (auricle) into external auditory meatus
77
External auditory meatus
channels sound waves to tympanic membrane
78
Middle ear
between tympanic membrane & cochlea; holds ossicles
79
Malleus (
hammer) is attached to tympanic membrane; carries vibrations to incus (anvil)
80
Stapes
(stirrup) receives vibrations from incus, transmits to oval window (cochlear membrane)
81
Stapedius muscle
attached to stapes
provides protection from loud noises
• can contract to dampen large vibrations to prevent nerve damage in cochlea
ear membrane)
82
Organ of Corti
where sound is transduced
83
Sensory hair cells located on
the basilar membrane have projections (steriocilia) projecting into cochlear duct
84
1 row of inner cells extend length of basilar membrane & multiple rows of outer hair cells are embedded in
tectorial membrane, which overhangs hair cells with cochlear duct
85
• Pressure waves moving thru cochlear duct create
shearing forces between basilar & tectorial membranes, moving & bending stereocilia
• Causing ion channels to open, depolarizing hair cells
• The greater the displacement, the greater the amount of NT released & APs produced
86
Conduction deafness
occurs when transmission of sound waves to oval window is impaired
helped by hearing aids
87
Sensorineural (perceptive) deafness
is impaired transmission of nerve impulses
often impacts some pitches more than others
• helped by cochlear implants, which stimulate fibers of CN VIII in response to sounds
88
Sclera
(white of eyes) is outermost layer
89
Transparent cornea
continuous with sclera
90
light passes thru
cornea into anterior chamber, then thru pupil which is formed by the pigmented muscle = iris (controls size of pupil), then thru lens & vitreous to retina
91
• Iris
(a pigmented muscle) controls size of pupil
92
• Pupil constricts by
contraction of circular muscles
| • Under parasympathetic control
93
• Pupil dilation is
via contraction of radial muscles
94
Structure of Eye
Photoreceptors are in retina
| Retina absorbs some light, the rest is absorbed by dark choroid layer
95
Axons of retinal neurons gather at
optic disc (blind spot) & exit eye in optic nerve
96
Visual field
part of the external world projected onto retina
97
Cornea and lens focus the
right part of the visual field to the left half of the retina and the left part of the visual field to the right half of the retina
98
Visual acuity
sharpness of vision
99
visual acuity Depends upon
resolving power: ability to distinguish (resolve) 2 closely spaced dots
100
With myopia (nearsightedness) image
focused behind retina because eyeball too short; object will have to be further away to be seen
101
With astigmatism
cornea or lens is not symmetrical; light is bent (refracting) unevenly, causing uneven focus
102
Retina = a multilayered epithelium consisting of
Neurons
pigmented epithelium
photoreceptors (rods & cones)
103
photoreceptors (rods & cones)
• neural layers are extension of brain; light must pass through several neural layers before striking rods & cones
104
Rods & cones face away from
from pupil; send sensory info to bipolar cells
105
Bipolars send electrical activity to
ganglion cells
106
Ganglion cells project axons
thru optic nerve to brain
107
Horizontal cells & amacrine cells are
interneurons involved in visual processing in retina
108
Electrical Activity of Retinal Cells
Ganglion & amacrine cells produce APs
| Rods, cones, bipolar, & horizontal cells produce graded potential changes
109
Visual transduction is
inverse of other sensory systems
110
In dark, photoreceptors release
inhibitory NT that hyperpolarizes bipolars
| • Inhibited bipolars do not release excitatory NT onto ganglion cells
111
Light inhibits photoreceptors from
releasing inhibitory NT, thus stimulating bipolars, which excite ganglionic cells, which transmit AP to brain
112
Rods & cones contain
many Na+ channels that are open in dark
| This depolarizing Na+ influx is the dark current
113
Light hyperpolarizes by
by closing Na+ channels
| • cGMP keeps Na+ channels open; light converts cGMP to GMP & Na+ channels close
