CH 10 - sensory physiology Flashcards
1
Q
What are sensory receptors?
A
Sensory receptors transduce (change) different forms of energy in the “real world” into nerve impulses.
2
Q
What is taste also known as?
A
gustation
3
Q
What are taste buds?
A
Receptors are called taste buds – consist of 50 to 100 specialized epithelial cells with long microvilli that extend out through the pore in the taste bud to the environment of the mouth, where they are bathed in saliva.
Epithelial cells are not neurons but become depolarized when stimulated, produce action potentials, and release neurotransmitters to stimulate the sensory neurons – called neuroepithelial cells
4
Q
What are taste buds also known as?
A
Papillae
5
Q
What chemoreceptors are used for taste and smell?
A
Taste responds to chemicals dissolved in food and drink.
Smell responds to chemical molecules from the air.
Olfaction greatly influences gustation
6
Q
What are the 5 categories for taste?
A
Five categories of taste:
~salty
~sour
~sweet
~bitter
~umami (meaty)
Each taste bud has taste cells for the five categories
Taste is influenced by the temperature and texture of the substance, the concentration of the chemical, and the stimulation of olfactory receptors
7
Q
What is olfactory apparatus, where is it located, and what does it consist of?
A
Olfactory receptors are located in the olfactory epithelium of the nasal cavity.
Olfactory apparatus consists of bipolar olfactory sensory neurons, supporting (sustentacular) cells, and basal stem cells
8
Q
What do sustentacular cells do?
A
Sustentacular cells oxidize hydrophobic volatile odors.
9
Q
What do basal stem cells do?
A
Basal stem cells replace receptors damaged by the environment.
10
Q
What are Olfactory receptors?
A
Olfactory receptors are bipolar neurons with one dendrite projecting into the nasal cavity that ends in a ciliated knob
Proteins in the cilia bind to odorant molecules
~380 genes code for ~380 different olfactory receptors.
One odorant molecule stimulates one protein in one sensory neuron
11
Q
How does smell work?
A
G-protein coupled
Odor binding activates adenylate cyclase to make cAMP and PPi (pyrophosphate)
cAMP opens Na+ and Ca2+ channels
Produces a graded depolarization which stimulates the action potential
Up to 50 G-proteins may be associated with 1 receptor protein – gives great sensitivity through amplification
12
Q
How do G-protein coupled receptors help smell?
A
DIFFERENT FROM THE ONES IN NERVES
Up to 50 G-proteins may be associated with 1 receptor protein – gives great sensitivity through amplification
The GP bind to hair and receptors???
13
Q
What is the vestibular apparatus?
A
Provides a sense of equilibrium
Located in the inner ear
Consists of:
~Otolith organs
Utricle and saccule – linear acceleration
~Semicircular canals – rotational acceleration
14
Q
What has the function of rotational acceleration?
A
Semicircular canals
15
Q
What are the two otolith organs?
A
Utricle & Saccule
16
Q
Where is the inner ear/what does it consist of?
A
Consists of a bony labyrinth surrounding a membranous labyrinth
Between the two is fluid called perilymph.
Within the membranous labyrinth is fluid called endolymph.
17
Q
What are sensory hair cells?
A
Modified epithelial cells called vestibular hairs cells with 20 to 50 hairlike extensions called stereocilia (not true cilia) and one kinocilium (true cilium)
18
Q
What is stereocilia?
A
(ear hair)
Stereocilia are modified microvilli and are arranged in rows of increasing height
Touching the stereocilia of the highest row is an even taller cilium called the kinocilium
19
Q
How does ear hairs help sense direction?
A
- When stereocilia bend toward the kinocilium, the hair cell is depolarized.
- The hair cells release a neurotransmitter that depolarizes sensory dendrites in the vestibulocochlear nerve.
- Bending away from the kinocilium hyperpolarizes the hair cell which releases less neurotransmitter.
- The frequency of action potentials in the sensory neurons that innervate the hair cells carries information about the direction of movements.
20
Q
What is the special cilia in your ear?
A
Kinocilium
21
Q
What fluid is between the bony labyrinth and the membrane labyrinth?
A
Perilymph
22
Q
What fluid is only in the membrane labyrinth?
A
Endolymph
23
Q
What are the 2 parts of the otolith organ?
A
Utricle & Saccule
24
Q
What are the ear gel stones in the otolith organs called?
A
Ololiths
25
Which otolith organ detects vertical movement?
Saccule
26
Which otolith organ detects horizontal movement?
Utricle
27
What fluid tells you if you’re spinning?
Endolymph
28
figure out a question for this
*Specialized epithelium called the macula houses hair cells.
*Stereocilia are embedded in a gelatinous otolithic membrane.
*The gel also contains crystals of calcium carbonate called otoliths (ear stones)
29
What is the name of the ducts that hold the endolymph?
Ampulla
30
How are hairs in semicircular canals?
* Hair cells are embedded in the crista ampullaris, with stereocilia stuck into a gelatinous cupula.
* Rotation makes the endolymph circulate, pushing the cupula and bending the hair cells.
31
What are sound waves characterized by?
Frequency, in hertz
32
What does the outer ear do?
Sound waves are funneled by the pinna (or auricle) into the external auditory meatus, which channels them to the tympanic membrane (eardrum).
33
What are the 3 middle ear bones?
Malleus (connected to the tympanic membrane) → incus → stapes
34
What are the two windows called?
Oval window & round window
35
What dampens the stapes if the sound is too extreme? (stapes is connected to oval window & cochlea)
Stapedius muscle dampens the stapes if the sound is too intense
36
Out of the oval and round windows, which is top and bottom?
Oval window is top
Round window is bottom
37
What are the 3 cochlear chambers?
The upper chamber is a portion of the bony labyrinth called the scala vestibuli.
There is also a lower bony chamber called the scala tympani.
The middle is called scala media or cochlear duct
38
Small canal that connects the scala vestibuli to the scala tympani
Helicotrema
39
How does sound travel through the cochlea?
Vibrations from the oval window of the middle ear displace perilymph in the scala vestibuli.
Vibrations pass through the vestibular membrane into the cochlear duct through the endolymph.
Next, vibrations pass through the basilar membrane into the perilymph of the scala tympani.
Vibrations leave the inner ear via the round window.
40
Where do the frequencies travel in the cochlea? (high and low are different)
Sound waves are transmitted through the cochlear duct at locations that depend on the frequency of the sound.
Low-frequency sounds travel further down the spiral of the cochlea to the apex
High-frequency sounds are closer the base
41
Talk about inner and outer hair cells
Mechanosensory hair cells (stereocilia) are located on the basilar membrane, projecting into the endolymph of the cochlear duct
Inner hair cells: 3500 that form one row that runs the length of the basilar membrane. Each is innervated by 6 to 20 sensory neurons of cranial nerve VIII and relay sound.
Outer hair cells: 11,500 arranged in rows with 3 rows per turn. They are innervated by motor neurons that make them shorten when depolarized and elongate when hyperpolarized
42
What is the spiral organ (organ of corti) made up of?
Spiral organ is made up of the basilar membrane, inner hair cells with sensory fibers, and the tectorial membrane.
Stereocilia are embedded in a gelatinous tectorial membrane
43
On a molecular level, how does hearing work?
When sound waves enter the scala media, the tectorial membrane vibrates, bending stereocilia.
Opens K+ channels that are facing the endolymph
K+ rushes in, depolarizing the cell
Releases glutamate onto sensory neurons
K+ returns passively to perilymph at the base of the stereocilia
44
How does light pass though the eye?
Light passes through the cornea and into the anterior chamber of the eye.
Next, it passes through the pupil, which can change shape (due to the pigmented iris muscle) to allow more or less light in.
Then it passes through the lens, which can change shape to focus the image.
Then passes through the posterior chamber and the vitreous body
Finally, it hits the retina, where photoreceptors are found and then absorbed by the pigmented choroid layer.
45
What does the iris do to the pupil?
Constriction: contraction of *circular muscles* via parasympathetic stimulation (Oculomotor nerve)
Dilation: contraction of *radial muscles* (dilator papillae muscle) via sympathetic stimulation
46
How does the iris have color?
Pigmented epithelium
47
What is the lens made of
Composed of layers of living cells that are normally completely clear
Avascular
Cell metabolism is very low and anaerobic
Attached to muscles called ciliary bodies
Suspensory ligaments support the lens by way of zonular fibers
48
What is aqueous humor? (eye)
Fills anterior and posterior chambers between the cornea and lens
A clear, watery liquid secreted by ciliary bodies to provide nourishment to lens and cornea
Drains into scleral venous sinus (Canal of Schlemm) back into the venous blood
Inadequate drainage leads to glaucoma
49
What is the clear outside of the eye called?
Cornea
50
What is the opaque cover below the cornea called?
Sclera (white part)
51
How does the lens adjust to focus on something?
Accommodation is the ability of the lens to keep an object focused on the retina as the distance between the eye and the object moves.
Contraction of the ciliary muscle allows the suspensory ligaments to relax and the lens to thicken and roundup; this is good for close vision.
Relaxation of the ciliary muscle pulls on the suspensory ligaments, causing the lens to thin and flatten; this is good for distant vision
52
What is nearsightedness called?
Myopia
53
How do you correct myopia?
Distant images are brought to a point of focus in front of the retina.
Often due to an elongated eyeball
Corrected by concave lenses in eyeglasses
54
How does vision sharpness work?
Sharpness of vision that depends upon resolving power – the ability to distinguish between two closely spaced objects
55
What is farsightedness called?
Hyperopia
56
How do you correct hyperopia
Distant images are brought to a point of focus behind the retina.
Often due to a short eyeball
Corrected by lenses that are convex
57
How do you correct an astigmatism?
Asymmetry of the cornea and/or lens curvatures
Get several points of focus on the retina
Corrected by cylindrical lenses
58
What dent in the retina helps clear vision? (?)
Fovea Centralis
59
What is normal eyesight called?
Emmetropia
60
What is the "blind spot" and why is it a blind spot?
Optic disc. No photo receptors
61
What does the sympathetic nervous system do to pupils?
It dilates them
62
What does the parasympathetic nervous system do to pupils?
It contracts them
63
What muscle does the sympathetic nervous system control?
Radial muscle
64
What muscle does the parasympathetic nervous system control?
Circular muscle
65
Where is the retina/what are some parts?
The retina is a forward extension of the brain, so the neural layers face outward toward the incoming light
Neuron axons in the retina are gathered at a point called the optic disc (blind spot) and exit as the optic nerve
Blood vessels also enter and leave here.
66
What are the layers of the retina?
Photoreceptors (rods and cones) are in the inner layer (toward the vitreous body)
These synapse on a middle layer of bipolar cells, which synapse on the outer layer of retinal ganglion cells.
There are also horizontal cells and amacrine cells within the layers
67
What do rods and cones consist of?
Outer segment; full of flattened discs with photopigment molecules
Inner segment that contains the cell organelles
68
How does light affect our rods?
Rods allow black-and-white vision in low light
Contain the purple pigment rhodopsin, which absorbs green light best (~500nm)
a. Absorption causes rhodopsin to dissociate into retinaldehyde and opsin.
b. Retinaldehyde (also called retinal or retinene) is derived from vitamin A.
c. Called the bleaching reaction
69
What is the visual cycle of the retinal?
Visual Cycle of Retinal
a. In rhodopsin, retinal exists in an 11-cis form.
b. After bleaching, the retinal is in an all-trans form and separates from opsin
c. The separation changes the ionic permeability of the rod and results in production of the nerve impulse
d. To be reincorporated into retinal, it must be converted back into 11-cis.
e. This occurs in the pigment epithelial cells.
70
What is dark current and how does it work?
Dark Current
In the dark, photoreceptors inhibit (hyperpolarize) bipolar cells.
Na+ channels in rods and cones are always open, depolarizing the photoreceptor; called the dark current
This allows the photoreceptor to release inhibiting neurotransmitter in the dark.
Light inhibits the photoreceptors from releasing their inhibitory neurotransmitter and therefore stimulates the bipolar cells.
71
What happens when lights hit photoreceptors?
When Light Hits Photoreceptors
a. Dissociation of rhodopsin activates a G-protein/2nd messenger system, which closes Na+ channels.
G-proteins are called transducins.
Alpha transducin activates the enzyme phosphodiesterase that converts cGMP to GMP.
This closes cGMP-gated Na+ channels and inhibits the dark current
b. Photoreceptors are hyperpolarized, and inhibition on bipolar cells is lifted.
c. Bipolar cells activate ganglion cells that transmit action potentials to the brain
72
What is the relationship between cones and color?
Cones are less sensitive to light, but allow color vision and greater visual acuity.
Trichromatic vision involves three types of cones.
a. S: short wavelengths, blue
b. M: medium wavelengths, green
c. L: long wavelengths, red
Instead of opsins, photopigments have photopsins with retinene
Photopsins vary in each type of cone.
Cone response depends on wavelength and the intensity of the light
73
How does visual acuity work?
Vision is best at one point in the retina, called the fovea centralis within the macula lutea
a. Here, other layers of the retina are pushed aside, so light falls directly on a group of cones.
b. Each cone has a 1:1 relationship with a ganglion cell (usually it is 105:1), which allows great visual acuity.
c. Only works in good light.
Convergence of lots of rods onto a single ganglion cell increases light sensitivity.
Saccadic eye movements continually shift parts of the visual field onto the fovea
74
What does failure to drain aqueous humor lead to?
Glaucoma
75
What does contraction do? (eye)
Contraction of the ciliary muscle allows the suspensory ligaments to relax and the lens to thicken and roundup; this is good for close vision.
76
What does relaxation do? (eye)
Relaxation of the ciliary muscle pulls on the suspensory ligaments, causing the lens to thin and flatten; this is good for distant vision
77
Is contraction or relaxation good for close vision?
Contraction
78
Is contraction or relaxation good for distant vision?
Relaxation
79
What does vision sharpness depend on?
the ability to distinguish between two closely spaced objects
80
Does contraction make the lens thicker or flatter?
Thicker
81
Does relaxation make the lens thicker or flatter?
Flatter
82
Is close vision thicker or flatter (lens)?
Thicker
83
Is distant vision thicker or flatter (lens)?
Flatter
84
What is myopia? How do you correct it (glasses)?
Nearsightedness
Concave lenses
85
What is hyperopia? How do you correct it (glasses)?
Farsightedness
Convex lenses
86
What is astigmatism? How do you correct it (glasses)?
Asymmetrical lenses
Use an uneven lens
87
What is emmetropia? How do you correct it (glasses)?
Normal
No fix needed
88
What is the optic disc?
Blind spot :)
89
Why do you shine a bright light in your eye?
Because its dark in there but you could see in. It shows whatever issue you have.
90
What is the other spot (not optic disc) that Dr. Seo asked us to memorize?
Fovea Centralis: very clear vision
91
What layer is photoreceptors?
Inner layer (technically the outside)
92
What layer is bipolar cell?
Middle layer
93
What layer is ganglion cell?
Outer layer (technically the inside)
94
What are the parts of a photoreceptor?
Rods and cones
95
Which layer of eyes is connected to the optic nerve?
Ganglion cell
96
What are the parts of the bleaching reaction?
Retinaldehyde & opsin
97
What is retinaldehyde also known as?
Retinal or retinene
98
Is light cis or trans?
Cis
99
Is darkness cis or trans?
Trans
100
After bleaching is the retinal cis or trans?
Trans
101
What splits into retinaldehyde and opsin?
Rhodopsin
102
The dark _____?
Current
103
Why is it called dark current?
Cis/photoreceptor generates a current in the dark
104
What becomes inactive during the dark current?
Phosphodiesterase
105
What polarization does dark current have?
Depolarization
106
What cell allows the brain to see?
Ganglion cells
107
How does darkness work?
The photoreceptor secretes inhibitory neurotransmitters to the bipolar cell. This means the BPC can't activate the ganglion cell, so the brain can't see anything
108
Explain the opposite of darkness
The photoreceptor does NOT secrete inhibitory neurotransmitters. The bipolar cell secretes neurotransmitters into the ganglion cell which gives the brain something to look at
109
Create a Q for this
phosphodiesterase
110
Which cell can only see in black and white?
Rods
111
What cell has trichromatic division?
Cones
112
What part of the eye gives the best vision?
Fovea centralis
113
Why is the fovea centralis the best vision?
105:1 ganglion cell to photoreceptor usually, but FC has 1:1
114
Is convergence or non-convergence better for the dark?
Convergence
115
Is convergence or non-convergence better for the light?
No convergence
116
What holds the hair in the ampulla?
Christa ampulla
117
What is the little bump in the semicircular canal?
ampulla
118
What are the soundwave chambers?
Scala vestibuli (inside cochlea) (top)
Scala media (cochlea duct) (middle)
Scala tympani (bottom)
119
What liquid is between the bone and ear structure?
perilymph
120
What liquid is inside the scala media?
endolymph
121
Which wavelength travels further?
The more stretched out one
122
What are the windows inside the ear
Top: oval window - scala vestibuli
Bottom: round window - scala tympani
123
What section of the ear has bones?
Middle ear
124
What is the spiral organ/ organ of corti? How many hair cells are there?
Hair cells connected to the brain to give you the pitch. as well as if you're spinning
3.5k
125
where are all the scala's located?
In the cochlea
126
What is the spiral organ composed of?
Sensory fibers, inner hair cells (hearing), outer hair cells (motor neuron), tecteral membrane (on top of the hair cells), and basilar membrane (holds inner hair cells?)
127
Where is the spiral organ located?
Cochlea
128
What fluid is inside the scala tympani?
perilymph
129
What fluid is inside the semicircular canal and scala media?
endolymph
130
How to distinguish between low and high frequency?
Low frequency travels all through the cochlea
High frequency barely goes through the cochlea
Hair cells help with this
131
Where does the light path travel?
cornea > pupil > lens > retina
132
What are the iris muscles?
Circular (inside) and radial (outside) muscle
133
What receptors does olfactory use?
G-protein coupled
134
What does taste and smell use?
Chemoreceptors
135
What is the sympathetic division also known as?
Fight or flight
136
What is the parasympathetic division also known as?
Rest and digest
137
What is some info on circular muscles?
Inside of the iris
Constrict pupil
Parasympathetic
138
What is some info on radial muscles?
Outside part of the iris
Dilate pupil
Sympathetic
139
What is lens accommodation?
flattening or thickening the lens to see far away or close up, respectively
140
!!! important eye table !!!
Lens: Thick / thin
Ciliary muscle: contracted / relaxed
Zonular fiber: relaxed / tight
Vision: close / far
141
If your lens in thick you will see _____
close
142
If you see close your ciliary muscle is _________
relaxed/loose
143
If your ciliary muscle is contracted, your zonular fiber is ____
relaxed
144
If your zonular fiber is relaxed, your lens will be ____
thick
145
If your lens is thin you will see ____
far
146
If you see far your zonular fiber is ____
tight
147
If your zonular fiber is tight, your ciliary muscle will be ____
relaxed
148
If your ciliary muscles are relaxed, your lens will be ___
thin
149
What is presbyopia?
Hard to see close due to age
150
What is:
Normal vision
Old vision
nearsightedness
Farsightedness
Multiple visions
it is:
Emmetropia
Presbyopia
Myopia
hyperopia
astigmatism
151
How do you fix presbyopia (glasses)?
Bifocals
152
What are the layers in the retina?
photoreceptor, bipolar cell, and ganglion cell (connected to brain)
153
How do you activate photoreceptors?
dark time (dark current)
154
What does a depolarized photoreceptor do?
Secretes inhibitory neurotransmitters
155
What inactivates the photoreceptor so we can see light?
Retinol
