Exam 4 Flashcards
1
Q
In what structure does vision begin?
A
The retina
2
Q
What structure contains the photoreceptors?
A
The retina
3
Q
In humans visual information is first processed at low levels in the _______and the at higher levels in the ________.
A
Retina
Cortex
4
Q
In humans approximately ______ of the cortex is dedicated to some sort of visual processing.
A
Half
5
Q
What is the primary function of the visual system?
A
To recognize objects and guide movements
6
Q
True / false: recognition of objects and guiding movements are both functions that are carried out by parallel but interacting pathways.
A
True
7
Q
The pupil forms a ______ that enables the entry of light into the visual system.
A
Diaphragm
8
Q
The _______ and ______provide the small refractive optics that project a small image of the outside world onto the light sensitive ________.
A
Cornea
Lens
Retina
9
Q
The retina is a thin sheet of neurons composed of________ major cell types:
3 cellular layers separated by 2 _______ layers
A
Five
Synaptic
10
Q
What do photoreceptors do?
A
Absorb light and convert it to a signal in a process called phototransduction
11
Q
Photo receptor cells connect to ________ cells
A
Bipolar
12
Q
Bipolar cells connect to the ___________ cells
A
Retinal ganglion cells
13
Q
The ________cells form the optic nerve connecting the retina to the brain.
A
Retinal ganglion
14
Q
Which nerve connects the retina to the brain
A
The optic nerve
15
Q
What are the 3 cellular layers of the retina?
A
- Photoreceptors
- Bipolar cells
- Retinal ganglion cells
16
Q
What are the two synaptic layers of the retina?
A
- Outer layer
- Inner layer
17
Q
What is the outer synaptic layer of the retina?
A
The layer that contains the synapses formed between the photoreceptors and the bipolar cells.
18
Q
What is the inner synaptic layer of the retina?
A
The layer containing the synapses formed between the bipolar cells and the retinal ganglion cells.
19
Q
The retinal circuit also includes many lateral connections provided by ______ and ______ cells
A
Horizontal cells (outer synaptic layer)
Amacrine cells (inner synaptic layer)
20
Q
In low level visual processing (the initial stage) the retina extracts _____ and ______ features of the outside world and conveys this information to ________ visual centers
A
Spatial
Temporal
Higher
21
Q
Phototransduction takes place in the _______ where _______cells absorb light and convert it into a _______
A
Retina
Photoreceptor
Neuronal Signal
22
Q
In phototransduction the neuronal signal is passed to ________ cells, and then to ______cells
A
Bipolar cells
Ganglion cells (retinal)
23
Q
Image quality is highest at the ______
A
Optical axis
24
Q
In the optical axis image quality approaches the limit imposed by the diffraction index of the _______
A
Pupil
25
Away from the optical axis, image quality is degraded owing to aberrations in the _____ and ______
Cornea and lens
26
Vision is the sharpest in what structure?
The fovea
27
The density of photoreceptors, bipolar cells and ganglion cells is the highest at the ______
Fovea
28
What is the fovea?
Area of retina near the optical axis.
29
What is the foveola?
Center of the fovea
30
True/false: in the foveola, the other cell layers are pushed aside to reduce additional blur and light scattering.
True
31
What is a black pigment epithelium?
Lining in the back of the eye that absorbs light and keeps it from scattering back into the eye.
32
What is the optic disc?
The Region of the Retina where the axons of the retinal ganglion cells converge and extend through the retina to emerge from the back of the eye as the optic nerve.
33
True/false: the optic disc contains the highest number of photoreceptors.
False.
The optic disc is devoid of photoreceptors
34
The _______ corresponds to the blind spot of the visual field each eye has because it is ________.
Optic disc
Devoid of photoreceptors
35
What are the two types of photoreceptors?
1. Rods
2. Cones
36
All photoreceptors have a common structure with 4 functional regions. What are they?
1. Outer segment
2. Inner segment
3. Cell body
4. Synaptic terminal
37
Which type of photoreceptor has a structure consisting of a cylindrical outer segment that has of free floating discs separated from the cell membrane
Rods
38
Which type of photoreceptor has a shorter, tapered outer segment with discs that are continuous with the cell membrane
Cones
39
True/false: rods and cones have different functions and different sensitivity to light.
True
40
Which type of photoreceptor can signal the absorption of a single photon and are responsible for vision under dim illumination?
Rods
41
Which type of photoreceptor is less sensitive to light?
Cones.
42
______ are responsible for vision in day light
Cones
43
Which photoreceptor has faster responses: rods or cones
Cones
44
Which photoreceptor has responses that can saturate as light level increases.
Rods
45
Which photo receptor is more sensitive to light?
Rods
46
Which photoreceptor is not sensitive to color?
Rods
47
In Night Vision only _____ are active, so all functional photoreceptors have the same absorption spectrum and the brain cannot distinguish colors.
Rods
48
Primates have ____ type of rod and ___ types of cones.
1
3
49
What are the three types of cones found in primates?
1. S cones (short)
2. M cones (medium)
3. L cones (long)
50
The three types of cones in primates each detect different wave lengths, what are they?
1. Short-wave (S cones)
2. Medium-wave (M cones
3. Long-wave (L cones)
51
The human retina contains about _____ million rods and ______ million cones.
100
6
52
In what structure of the retina are cones mostly found?
The fovea
53
______ are found mostly in the rest of the retina outside the fovea.
Rods
54
At night the central fovea is blind due to the absence of ____
Rods.
55
______ is the visual pigment in rod cells.
Rhodopsin
56
Rhodopsin has two components. What are they?
1. Opsin
2. Retinal
57
What is opsin and where is it found?
It is the protein portion of rhodopsin.
It is embedded in the disc membrane
58
______ does not by itself absorb light.
Opsin
59
What is retinal and where is it located?
The light absorbing moiety in rhodopsin.
It is a small molecule whose cis 11 isomer is covalently linked to a residue in the opsin protein
60
The absorption of a photon by _____ causes it to flip from the 11-cis configuration to the all-trans configuration
Retinal
61
In phototransduction, in the dark _____ ions flow into the photoreceptor through _______ cation channels that are activated by the ________ cyclic guanosine 3’ - 5’ monophosphate (cGMP).
Na+
Non-selective
Second messenger
62
In phototransduction, the shape transition of the ______molecule causes a conformational change in the ______which triggers the second step of phototransduction.
1. Retinal
2. Opsin.
63
The retinal triggered conformational state change in opsin (the activated state) is called_____
Meta rhodopsin II
64
Is the meta rhodopsin II state stable or unstable?
Unstable
65
The ________state splits within minutes, yielding ______ and all-trans ______
Meta rhodopsin II
Opsin
All-trans retinal
66
In phototransduction, the all-trans______ is transported to pigment epithelial cells where it is reduced to all-trans ______.
Retinal
Retinol (vitamin A)
67
Retinol is a precursor of _______ which is eventually transported back to the rods in phototransduction
11-cis retinal
68
How does phototransduction occur?
1. In the dark Na+ ions flow through non-selective cation channels (activated by cGMP). In the light a photon is absorbed by retinal.
2. When a photon hits The retinal molecule changes configuration from 11-cis to all-trans.
3. The configuration change in retinal causes a conformational in opsin to the activated meta rhodopsin state.
The meta rhodopsin state is unstable and splits into opsin and all-trans retinal
4. All-trans retinal is transported to pigment epithelial cells, where it is reduced to all-trans retinol.
5. 11-cis retinal is subsequently transported back to the rods.
69
In phototransduction, in the absence of light, _______is inactive because it is bound to a molecule of ______(GDP)
Transducin
Guanosine diphosphate
70
In phototransduction when light is present, activated rhodopsin in the form of ________diffuses within the disc membrane where it encounters _______
Meta rhodopsin
Transducin
71
In phototransduction the exchange of GDP for GTP occurs when _________
This leads to the dissociation of the Transducin _______
Meta rhodopsin II diffuses into the disc and encounters Transducin
Alpha subunit
72
What is Transducin?
Transducin is a G protein naturally expressed in vertebrate retina rods and cones and it is very important in vertebrate phototransduction.
73
Meta rhodopsin II can activate hundreds of additional Transducin molecules by _____the response of a cell to light
Amplifying
74
In phototransduction, amplification is increased when the active Transducin ______subunit forms a complex with a cyclic phosphodiesterase, which increases the hydrozylation of _______into GMP, increasing the degree of amplification.
Alpha subunit
cGMP
75
In phototransduction, the concentration of ________ultimately controls the opening of the cGMP gated channels:
At low levels of ______ the channel is _____
At high levels of ______the channel is ______
cGMP
cGMP, closed
cGMP, open
76
In phototransduction, Meta rhodopsin II is inactivated when is is phosphorylated by a _________
Rhodopsin kinase
77
In phototransduction, larger responses are terminated quicker:
In the light, the internal concentration of _____ drops and accelerates the phosphorylation and inactivation of _______
Ca2+
Rhodopsin
78
In darkness, the concentration of cGMP in the cytoplasm is _______, the cGMP gated channels are open and the photoreceptor is __________
High
Depolarized
79
In light, the concentration of cGMP is ______, the cGMP gated-channels are closed and the photoreceptor is ______
Low
Hyper polarized
80
All-trans retinal is a crucial compound in the visual system. It’s precursor, ______ cannot be synthesized and so must be a regular part of the diet
Vitamin A (retinol)
81
In color vision, each type of cone in the human retina produces a variant of the _____ protein
Opsin
82
In color vision, the various cone opsins differ in their ________. Efficient light absorption depends on the ______ of light.
Absorption spectrum
Wavelength
83
Red light (longer wavelengths) excites _____ cones more than M cones
Whereas, green light excites _____cones more then L cones
L cones
M cones
84
True/false: The relative degree of excitation in the various cone types contains information about the spectrum of light, independent from the intensity of light.
True
85
The ability of the brain to compare signals from different _______ is the basis of color vision.
Cone types.
86
In the synaptic outer layer, bipolar _______cells have broadly absorbing dendrites that spread laterally in the outer plexiform layer where they contact photoreceptors.
Horizontal
87
Horizontal cells are excited by _______released by photoreceptors. Horizontal cells are electrically coupled
Glutamate
88
What is the function of horizontal cells?
To measure the average excitation of the photoreceptor population. This signal is then fed back onto the photoreceptors.
89
Photoreceptors are under 2 opposing influences. What are they?
The opposing influences create an ________: that is only the photoreceptors that are strongly activated can hyper polarize.
Enables edge detection and contrast enhancement in the visual cortex.
1. Light falling on a photoreceptor at the center of the receptive field hyper polarizes them.
2. But light falling on the surrounding photoreceptors depolarizes them
Antagonistic receptive field.
90
The photoreceptor layer produces a relatively simple neuronal representation of the visual scene:
Neurons in bright regions are _______whereas neurons in dark regions are ________\
This neuronal representation is relayed and transformed by the ________ layer
Hyper polarized
Depolarized
Bipolar layer
91
Photoreceptors form synapses with different ______cells
Bipolar
92
In the dark, photoreceptors are depolarized and release _______ continuously.
Glutamate
93
In the light, photoreceptors are hyper polarized and do not release ____
Glutamate
94
What are the two type of bipolar cells that help carry out vision?
1. On cells
2. Off cells
95
On bipolar cells are activated by _____
Light
96
Off bipolar cells are activated by ______
Darkness
97
Off bipolar cells express an _______ glutamate receptor.
When glutamate is released by the photoreceptors in ________, the off cells _______
Ionotropic
Darkness
Depolarize
98
The on bipolar cells express a _______glutamate receptor, and when activated by ______this receptor closes a cation channel.
When glutamate is released by the photoreceptors in darkness, the on bipolar cells______
Metabotropic
Light
Hyper polarize
99
In darkness, off bipolar cells are ______ and on bipolar cells are ___
Depolarized
Hyper polarized
100
In daylight, off bipolar cells ______ because glutamate is no longer released by photoreceptors.
Inactivate. (Hyper polarize)
101
On bipolar cells ______ when glutamate is no longer released by photoreceptors in daylight
Activate (depolarize)
102
In daylight, off bipolar cells are _____ and on bipolar cells are _______
Inactivated
Depolarizes
103
True false: on and off bipolar cells have different morphologies.
True
104
How do does the morphology of on and off cells differ?
They differ in where the axon terminal ends.
The axons in on cells terminate in the proximal (lower half) of the inner layer.
The axons of off cells terminate in the upper half (distal) layer of the inner layer.
105
What type of neuron are amacrine cells?
A type of interneuron.
106
In each layer bipolar cells connect to _______cells and to ______cells
Retinal ganglion cells
Amacrine cells.
107
On bipolar cells connect to ____ retinal ganglia cells and off bipolar cells connect to ______ganglia cells.
On
Off
108
_________cells have broadly arborizing dendrites that spread laterally into the inner plexiform layer where they contact the retinal ganglion cells
Amacrine
109
____released by bipolar cells excite Amacrine cells, which are electrically coupled
Glutamate
110
What is the function of Amacrine cells?
They measure the average excitation of bipolar cell population and this signal is fed back to the bipolar cells through inhibitory synapses.
111
The ________ layer produces a relatively simple neuronal representation of the visual scene that is relayed first to the bipolar cell layer then to the _____cell layer.
Photoreceptor layer
Retinal ganglion
112
What is the function of retinal ganglion cells?
To take info from the retina to the brain (the collect info from bipolar cells)
113
Most retinal ganglion cells fire action potentials ____even in complete darkness or constant illumination.
Spontaneously
114
What are the two major types of retinal ganglion cells?
1. On
2. Off
115
When light intensity increases _____retinal ganglion cells fire mor rapidly and the _____ retinal ganglion cells fire more slowly
On
Off
116
When light intensity decreases ____retinal ganglion cells fire more rapidly and the _____ retinal ganglion cells fire more slowly
Off
On
117
A moving object elicits strong firing in a retinal ganglion cell near the edges of the object because the edges are the regions where _______
Thus, the outline of an object is particularly useful for inferring its shape and identity especially when an object is moving.
Light intensity changes rapidly over time.
118
Several types of ganglion cells have been identified on the basis of their shapes and light responses
Retinal ganglion ____ and _____ cells are found in all vetebrates.
On
Off
119
Each separate population of _____cells sends a distinct neuronal representation of the visual field to the ______, where the firing of one _______cell represents one pixel in the representation.
These neuronal representations are relayed to the various visual centers including the ____.
Retinal ganglion cells
Brain
Thalamus
120
What is the thalamus?
Your thalamus is your body's information relay station. All information from your body's senses (except smell) must be processed through your thalamus before being sent to your brain's cerebral cortex for interpretation.
121
In the geniculostrite pathway, Axons of retinal ganglion cells extend to a midline crossing point called the ______
Optical chiasm
122
In the genicilostriate pathway, beyond the optical chiasm, Axons from the ______ hemiretinas proceed to the ipsilateral hemisphere. Axons from the ______hemiretinas cross back to the controlateral hemisphere
Temporal
Nasal
123
In the geniculostrite pathway, the temporal hemiretina of one eye sees the same half of the visual field (hemifield) as the ______retina of the other eye, the partial decussation of axons at the chiasm ensures that all the information about each hemifield is processed in the _____ of the controlateral side.
Nasal
Visual cortex
124
In the geniculostrite pathway ____layers receive information from each eye.
6
125
In the geniculostrite pathway, beyond the optical chiasm, the axons from the _____ and _____ hemiretinas carrying input from hemifield join in the optic tract, which extends to the lateral geniculate nucleus of the _____
Nasal
Temporal
Thalamus
126
The lateral geniculate nucleus in primates consists of _____layers, each of which receives input from either the ipsilateral or controlateral eye.
6
127
Each layer of the _______ contains a map on the controlateral hemifield, thus _____ concordant maps are stacked on top one another.
Lateral geniculate nucleus
6
128
The thalmic neurons relay retinal information to the _____
Primary visual cortex.
129
How Many visual Cortices are there and what are they?
3
1. Primary visual cortex (V1)
2. Secondary visual cortex (V2)
3. Tertiary visual cortex (V3)
130
The ____ visual cortex constitutes the first level of cortical processing of visual information.
Primary
131
From the primary visual cortex, information is transmitted over two major _____ pathways. What are these pathways.
Parallel
Dorsal and ventral pathways
132
What is the ventral pathway?
It projects to the temporal lobe ( the region of the brain involved in object recognition).
133
What is the dorsal pathway? (In vision)
It projects to the parietal lobe (region of the brain involved in spatial reasoning)
134
The _____ and ______ parallel pathways are interconnected and share information in vision
Ventral and dorsal
135
True/false: the number of functionally discrete areas of visual cortex is the same between species.
False. It varies between species
136
Have all visual areas been identified in humans?
No
137
_____ is a tool that has made it possible to establish what type of information these discrete areas of the visual cortex are processing.
fMRI.
138
Phototransduction begins in the ___ when a rhodopsin molecule absorbs a _____
Thus sets an ___ signaling cascade in motion which ultimately hyper polarizes the _________ decreasing _____ release in the other synaptic layer.
___ are sensitive to light and serve nocturnal vision. _____ are less sensitive to light and serve day vision
Photoreceptor
Photon
Amplifying
Photoreceptor
Glutamate
Rods
Cones
139
The retina transforms light patterns projected onto ____ into neuronal signals that are conveyed to different visual centers in the brain by the ______neurons.
This is called ____
Photoreceptors
Retinal ganglion neurons
Phototransduction
140
True/false: In producing its output the retina discards much of the stimulus information available at the receptor level and extracts features of the visual scene;
E.g., light intensity gradients, edges, motion, color
True.
141
The somatosensory system serves 3 functions. What are they?
1. Proprioception
2. Exteroception
3. Interoception
142
What is proprioception?
The detection of self
143
What is exteroception?
Detection of the outside world
144
What is interception?
Detection of the internal organs
145
All the somatic senses are carried out by two types of sensory neurons. What are they?
1. Dorsal root ganglion neurons
2. Trigeminal neurons
146
Trigeminal neurons primarily innervate the ______
Face
147
Dorsal root ganglia primarily innervate the ____
Trunk and limbs
148
The Trigeminal neurons and dorsal root ganglia are the _______ of the somatosensory system.
Primary receptor cells.
149
Trigeminal ganglia and dorsal root ganglia innervate what structures (4 of them)
1. Skin
2. Muscle
3. Joint capsules
4. Viscera
150
The dorsal root ganglia snd Trigeminal ganglion neurons transform _______ into electrical signals and transmit these signals to the ____\
Somatosensory stimuli
Brain
151
The cell bodies of the dorsal root ganglion neurons are located in the ____ of the spinal cord.
Dorsal horn
152
What type of neurons are dorsal root ganglion neurons?
Pseudo- unipolar
153
What are pseudo unipolar neurons?
The initially develop as bipolar neurons but the two cell processes fuse into a single continuous structure that emerges from a single point in the cell body.
154
Dorsal root ganglia project two axons: one to the ______ and one to the _______
Periphery
Brain
155
The peripheral axonal terminals of dorsal root ganglion neurons contain specialized ______. The central branches terminate in the spinal cord or the _______ of the brain stem.
Receptors
Thalamus
156
The axon of each dorsal root ganglion cell serves as a single transmission line between each receptor terminal and the central nervous system. This axon us often referred to as the _______
Primary afferent fiber.
157
In dorsal root ganglia, individual primary afferent fibers innervating a particular region of the body ,eg the thumb, are grouped together into bundles of axons forming a ________.
Peripheral nerve.
158
The different modalities of somatic sensation are mediated by different types of primary afferent fiber. Each type varies in _____ and _______.
Diameter
Conduction velocity
(Myelin sheath)
159
True/false: all sensory neurons are myelinated.
False.
160
Peripheral nerve fibers innervate the skin. These are called sensory or ___ nerves. The can also innervate muscle; these nerves are called ______neurons
Cutaneous
Motor
161
Each type of nerve can be further divided into subgroups based on properties related to its axon. What are these properties (3 of them)?
1. Diameter
2. Myelination
3. Conduction velocity
162
Sensory neurons are divided into the ___,____,____, and ____fibers
Whereas motor neurons are divided into the ___,____, ____, and ____ fibers
A(alpha), A(Beta), A(delta), and C
I, II, III, and IV
163
Which type of cutaneous nerve has the largest diameter)?
Which type of motor neuron has the largest diameter)?
A(alpha) at 12-20 micro meters.
I
Fastest conductance velocity
164
Which type of cutaneous nerve has the smallest diameter for a myelinated nerve?
Which type of myelinated motor neuron has the smallest diameter?
A(delta) at 1-6 micro meters
III
165
Which type of cutaneous nerve is unmylinated?
Which type of motor neuron is unmylinated?
C.
IV
Smallest diameter (0.2 to 1.5 um) slowest conduction velocity
166
The axons of A(alpha) and A(beta) cutaneous neurons have a large Diameter and are ______. These neurons innervate the cutaneous ____organs
Myelinated
Mechanosensing
167
The axons is A(delta) neurons have small diameter and are myelinated. These neurons innervate the _____ and respond to ____ and ______ stimuli.
Skin
Thermal
Noxious
168
The axons of C neurons have a small diameter and are unmyelinated. These neurons innervate the skin and sense ____ and ___ stimuli
(thermal and noxious
Anything that can cause pain
169
Group I motor neurons innervate muscle-spindle receptors and the _______organ. These neurons signal______ and _______
Golgi tendon
Muscle strength
Contractile force
170
Group II motor neurons innervate the receptors in ______. These neurons signal ________
Joint capsules
Proprioception
171
Group III and Group IV motor neurons innervate the ____ and _____and signal ______
Muscles and joints
Harsh movement
172
Large diameter neurons with myelinated axons conduct action potentials rapidly. They mediate ______ and _______ functions.
In these fibers internal resistance is low. These include the A(alpha) and A(beta fibers)
Touch and Proprioception
173
Small diameter, unmylinated or lightly myelinated neurons conduct action potentials slowly. These mediate _____ and _____
The internal resistance is higher. These fibers include the A(delta) and C fibers.
Thermosensation and pain.
174
Difference in velocity which neurons conducted action potentials affects how we perceive touch and pain.
There are usually ___ principle components to pain , but only ____ to touch
During pain sensation there is an ______ of the stimulus and a ______
2
1
Early mild perception
Later painful/pungent perception
175
_______ is a tool that can be used to record responses of an entire nerve. Recordings are made I. Response to electric shocks. The signal measured is the sum of all the action potentials generated in the nerve fibers. This is called the _____ action potential and is proportional to the number of active fibers.
Electromyography
Compound
176
In electromyography, different _______give different responses.
Weak stimuli activate only the ____axons which have the lowest electrical resistance. This is called the ____wave.
Medium stimuli activate A(alpha and beta) axons. This is the _____ wave
Strong stimuli activate the A(alpha, beta, delta) axons. This is the _____wave
Very strong stimuli activate all axons including the ones with the highest resistance (C). This is the _____ wave.
[# peaks of wave correspond to axons activated]
Electric intensities
Largest , A(alpha)
A(beta)
A(delta)
C wave (delta wave + single flattish C peak)
177
In electomyography the sensation evoked by the different waves goes from barely perceptible to burning pain. ____ is usually perceived last.
Burning pain.
178
Somatosensory neurons detect physical deformations of the ____. All stimuli are transformed into electrical signals by specialized ______
Skin
Receptors.
179
The sense of touch is mediated by ___types of mechanoreceptors
8
180
The sense of touch on the hand is mediated by 4 types of mechanoreceptor. What are they?
1. Meissner corpuscle
2. Merkel disk receptor
3. Pacinian corpuscle
4. Ruffini ending
181
A given mechanoreceptor is either connected to a slowly adapting fiber which _____in response to steady pressure on the skin or to a rapidly adapting fiber which responds to _____but not to steady pressure
Continuously fires
Motion.
182
In mechanoreceptors, mechanical distension (physical deformations) are transduced into electrical signals by the physical action of the stimulus on the _____ channels in the membrane.
Cation
183
There are specialized non-neuronal end organs that surround the nerve terminals of a mechanosensing nerve.
These organs detect different types of somatosensory stimuli and can be divided into four major classes: ______, _______, _____, and ____
Information gathered through touch results from the COMBINED action of all 4 receptors.
Meissner corpuscle
Merkel cells
Pacinian corpuscles
Ruffini endings
184
The 4 major classes of receptor organs can be subdivided into two subtypes depending on their size and location in the skin.
Type 1 organs consist of _____ and _____. They terminate in the superficial layers of the skin, between the dermis and the epidermis
Type 2 organs consist of _____ and ____ and terminate i. The deeper layers of the epidermis
Meissner corpuscles and Merkel cells
Pacinian corpuscles and Ruffini endings
185
________ are the most abundant receptor organ in the hand. They are globular, fluid filled structures.
Meissner corpuscles
186
Meissner corpuscles detect the _____ contact of the hand with surfaces and low frequency vibrations.
Initial.
187
Meissner corpuscles are innervated by ______ adapting fibers.
Rapidly (RA1)
188
________ are mechanoreceptors found mostly on the fingertips. They are semi-ridged structures that detect compressive strain to the nerve ending.
They signal the ______applied to the skin and are especially sensitive to edges, corners and points.
Merkel cells
Amount of pressure
189
Merkel cells are innervated by ______adapting fibers
Slowly (SA1)
190
_______ are large onion like structures in which successive layers of connective tissue are separated by fluid filled spaces.
These mechanoreceptors can amplify high frequency vibrations generated when using a tool held by the hand
Pacinian Corpuscles
191
Pacinian corpuscles are innervated by _____ adapting fibers.
Rapidly (RA2)
192
____ are elongated fusiform structures that enclose collagen fibrils extending from the subcutaneous tissues to folds in the skin.
They respond to ____ and are especially sensitive to joint movements
Ruffini endings
Stretch
193
Ruffini endings are associated with _____adapting fibers
Slowly (SA2)
194
The 4 major types of mechanoreceptors have distinct morphologies.
They also differ in the _____ as well as in their responses to ____
Size of their receptive fields
Touch stimuli
195
Stimulation of the mechanoreceptor organs deforms stretch sensitive ion channels expressed the the associated fiber.
The opening of these channels increases the conductance of _____ across the membrane leading to the ______of the associated neurons.
Cations (Na+, Ca2+)
196
Piezo receptors have ____ trans membrane domains
38
[these receptors are ion channels invoked in touch]
197
Done somatosensory receptors also express pain receptors (nociceptors).
These nocieptive neurons can be divided into two categories. What are they?
1. Short latency pain receptors (A(delta) fibers that mediate sharp pricking pain)
2. Long latency pain receptors (C fibers that mediate dull burning pain)
198
Somatosensory neurons express pain _____that detect different temperatures.
Thermoreceptors
199
Humans recognize four types of thermal sensation: cold, cool, warm and hot.
Thermal sensation results from the COMBINED activity of four different types of receptors. What are they?
Warm receptors
Cool receptors
Hot receptors
Cold receptors
200
A(delta) fibers are low threshold _____sensing fibers and some C fibers are high threshold ______ sensing fibers
Cool
Cold
201
____ fibers respond to rapid drops in temperature
_____ fibers respond to extremely cold temperatures
A(delta)
C
202
When grabbing an ice cube the ____ fibers of the hand are first activated, leading to a cooling effect. The _____ fibers are activated as the effect becomes pain.
A(delta)
C
203
Some A(delta) and C fibers are heat sensing fibers and act as simple thermometers. Their firing rates __ as temperature rises
Increase
204
The receptor genes transforming temperatures into electrical signals belong to the _______ (TRP) gene family
Transient potential receptor ion channel
205
Are TRP channels selective or non selective?
Non selective
206
The cool sensing receptor ____ responds to temperatures of <25 degrees C
And the cold sensin receptor _____ responds to temperatures <17 degrees C
TRPM8
TRPA1
207
_____ and _____ are warm sensing receptors
TRPV3 and 4
208
_____ and _____ are heat sensing receptors
TRPV1 and 2
209
There are several known agonists of the TRP channels.
Eg ____ is an agonist of TRPV1 and causes a burning effect
Eg _____ is an agonist of the TRPM8 channel and causes a cooling effect
Capsaicin
Menthol
210
Somatosensory information reaches the central nervous system through ____ spinal nerves and ___ cranial nerves
31
12
211
The skin of the tissue innervated by the afferent fibers that belong to a single nerve is called a _____
Dermatome
212
The muscle innervated by the efferent fibers that belong to the same nerve is called a ______
Myotome
213
How many dermatomes are there along the human body?
43
214
Fibers that convey the somatosensory information collected from a dermatome are bundled together as they enter the _____
Dorsal root ganglia
215
Large and small diameter fibers separate into _____ divisions
Medial snd lateral
216
The medial division contains the _____ fibers that transmit proprioceptive info from a dermatome
A(alpha and beta)
217
The lateral division contains the ____ and _____ fibers that transmit noxious and thermal info from a dermatome
A(delta) and C
218
All somatosensory fibers connect to the ______
But A(alpha and beta) fibers also connect to the _____ of the brain stem
Thalamus
Medulla
219
Inputs into the thalamus are arranged _____. The overall map of the body is preserved in The way neurons are connected.
This map us also called the ______
Topographically
Homunculus (Latin for little man)
220
Dorsal column medial lemniscal system relays tactile and Proprioceptive information from the ____ and the ____ fibers first to the medulla and then to the ___
A(alpha and beta)
221
The anterateral system relays noxious and thermal information from the ___ and ___ fibers directly to the thalamus
A(delta) and C
222
The thalamus connects to the somatosensory cortex. The dorsal column medial lemniscal system and the anterolateral system form two ______pathways
Parallel
223
Neurons of the medulla cross to the contralateral side and relay information directly to the _____
Thalamus
224
True/false: In the dorsal column medial lemniscal system, thalamical neurons connect to cortical neurons such that the topographical relationships between neurons is preserved.
True
225
In the anterolateral pathway, sensor neurons connect to spinal cord ______. These neurons form a spinoreticular tract wich mediates automatic response to pain.
These responses are not processed by the brain and are therefore quicker than responses to touch
These neurons also form a spinomesencephalic tract in the ____
Interneurons
Brainstem
226
Touch and pain pathways are ___
Pain has an emotional component to it.
Parallel
227
Tru/false: Within the dorsal column medial lemniscal system, inputs from skin or deep tissue are organized into columns of neurons that run to from the surface of the brain to the white matter.
True
228
In the primary somatosensory cortex there are five areas that each contain a somatotopic map of the body called the_____
Homunculus
The size of the body region is not reflective of the size that region occupies in the map. Lips and hands very sensitive to touch
229
Somatosensory information is relayed in ______ from the four regions in the primary somatosensory cortex to higher centers including the secondary somatosensory cortex, the parietal cortex and primary motor cortex
Parallel
230
Somatosensatin results from _____actions of multiple systems.
Parallel
231
True/false: sending is learning.
True.
232
What is the nasal cavity?
A large air filled space located behind the nose where it contacts the olfactory epithelium
233
Volute molecules enter through the _____
Nasal cavity
234
The olfactory epithelium consists of both ______ and ______\
Olfactory sensory neurons
Glial cells
235
True/false: olfactory sensory neurons are short lived but are continuously regenerates through neurogenesis.
True. They can regenerate on a monthly basis
236
Olfactory sensory neurons extend their dendrites in the _______
Nasal cavity
237
Olfactory sensory neurons project their axons to one of the 2,000 glomeruli in the brain into the ______
Olfactory bulb
238
What type of neuron are olfactory sensory neurons?
Bipolar neurons
239
Each olfactory neuron extends a single dendrite that gives rise to numerous thin ______ protruding into the olfactory epithelium which is covered with mucus.
The mucus helps facilitate the binding of odorant molecules to the cell surface of the _____
Celia
Celia
240
Who discovered olfactory receptors?
Buck and axel
241
What were the 3 assumptions made by buck and axel when they were lookin for olfactory receptors?
1. They must be G protein coupled receptors
2. They must be diverse (hence part of a multi Gene family)
3. They must be expressed in the olfactory epithelium.
242
Vertebrae olfactory receptors belong to a large multi Gene family of ______ which is evolutionarily conserved and found in all vertebrae species
GPCRs
243
Detailed studies of olfactory receptors suggests that oders bind to a _____ located in the trans membrane region of the GPCR. (Amino acid sequences are highly variable in the ____region
Pocket
Pocket
244
When an oder molecule combines to a GPCR, the ______ dissociates fro the Gs protein complex and activates an _____cyclase
alpha-s subunit
Adenylyl
245
______ binds to cGMP gated cation channels causing depolarization in the olfactory sensory neuron
cGMP
246
The human nose has ____ olfactory receptors while the mouse has ______ olfactory receptors.
This number is highly variable across species
400
1000
247
True/false: each olfactory sensory neuron expresses many types of olfactory receptors
False. Each sensory neuron expressed only ONE type of olfactory receptor
[one to one rule]
248
The olfactory epithelium is divided into several coarse zones and each zone contains neurons expressing a subset of the olfactory receptors.
True/false: the olfactory sensory neurons expressing a given receptor are interspersed in a zone.
True
249
Many animals have evolved a chemical language to communicate with conspecifics or other species. These chemicals are called _____
Pheromones
250
In mammals, pheromones are detected through a structure called the ____. It is a tubular structure in the nasal septum that is connected to the nasal cavity by a duct.
Vomeronasal epithelium
251
Olfactory sensory neurons in the vomeronasal organ express different types of _____: the V1R and the V2R
GPCRs
252
True/false: vomeronasal receptors are expressed similarly to the main olfactory receptors and follow the one to one rule.
True
253
True/false: a similar vomeronasal gerne family does not exist in mist apes.
True
254
True/false: humans have a vestigial vomeronasal organ
True. But is does not express receptors.
255
What’s the closest molecule humans have to a pheromone?
Androstenone
256
The OR7D4 receptor is largely selective for two chemicals: ______ and androstenedione. No othe chemicals can activate the receptor.
Detection if these molecules varies across people reflecting _____ in the OR7D4 receptor
Androstenone
Polymorphisms
257
I. Olfaction, the mitral and tufted cells extend their dendrites into individual glomeruli project to _____ higher brain centers.
These are the
5
1. Anterior olfactory nucleus
2. Olfactory tubercle
3. Piriform cortex [not called olfactory Cortex for whatever reason]
4. Amygdala
5. Entorhinal cortex
258
True/false: mitral and tufted cell in the Piriform vortex appear to be largely disorganized?
True.
259
In the Piriform cortex, oders activate sparse ensembles of neurons distributed across the entire ___\__
Piriform cortex
260
True / false: the same neurons can respond to many dissimilar orders.
True.
261
While the olfactory map us organized at the level of the ______, the Oder seems to be discarded in the ______ and the connections seem to be random.
Olfactory bulb
Piriform cortex
[olfactory epithelium—> bulb—> Piriform cortex]
