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Cellular Neurobiology > Exam 4 > Flashcards

Exam 4 Flashcards

1
Q

In what structure does vision begin?

A

The retina

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2
Q

What structure contains the photoreceptors?

A

The retina

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3
Q

In humans visual information is first processed at low levels in the _______and the at higher levels in the ________.

A

Retina

Cortex

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4
Q

In humans approximately ______ of the cortex is dedicated to some sort of visual processing.

A

Half

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5
Q

What is the primary function of the visual system?

A

To recognize objects and guide movements

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6
Q

True / false: recognition of objects and guiding movements are both functions that are carried out by parallel but interacting pathways.

A

True

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7
Q

The pupil forms a ______ that enables the entry of light into the visual system.

A

Diaphragm

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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

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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

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10
Q

What do photoreceptors do?

A

Absorb light and convert it to a signal in a process called phototransduction

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11
Q

Photo receptor cells connect to ________ cells

A

Bipolar

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12
Q

Bipolar cells connect to the ___________ cells

A

Retinal ganglion cells

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13
Q

The ________cells form the optic nerve connecting the retina to the brain.

A

Retinal ganglion

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14
Q

Which nerve connects the retina to the brain

A

The optic nerve

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15
Q

What are the 3 cellular layers of the retina?

A
  1. Photoreceptors
  2. Bipolar cells
  3. Retinal ganglion cells
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16
Q

What are the two synaptic layers of the retina?

A
  1. Outer layer
  2. Inner layer
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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.

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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.

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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)

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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

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21
Q

Phototransduction takes place in the _______ where _______cells absorb light and convert it into a _______

A

Retina

Photoreceptor

Neuronal Signal

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22
Q

In phototransduction the neuronal signal is passed to ________ cells, and then to ______cells

A

Bipolar cells

Ganglion cells (retinal)

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23
Q

Image quality is highest at the ______

A

Optical axis

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24
Q

In the optical axis image quality approaches the limit imposed by the diffraction index of the _______

A

Pupil

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25
Q

Away from the optical axis, image quality is degraded owing to aberrations in the _____ and ______

A

Cornea and lens

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26
Q

Vision is the sharpest in what structure?

A

The fovea

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27
Q

The density of photoreceptors, bipolar cells and ganglion cells is the highest at the ______

A

Fovea

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28
Q

What is the fovea?

A

Area of retina near the optical axis.

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29
Q

What is the foveola?

A

Center of the fovea

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30
Q

True/false: in the foveola, the other cell layers are pushed aside to reduce additional blur and light scattering.

A

True

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31
Q

What is a black pigment epithelium?

A

Lining in the back of the eye that absorbs light and keeps it from scattering back into the eye.

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32
Q

What is the optic disc?

A

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.

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33
Q

True/false: the optic disc contains the highest number of photoreceptors.

A

False.

The optic disc is devoid of photoreceptors

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34
Q

The _______ corresponds to the blind spot of the visual field each eye has because it is ________.

A

Optic disc

Devoid of photoreceptors

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35
Q

What are the two types of photoreceptors?

A
  1. Rods
  2. Cones
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36
Q

All photoreceptors have a common structure with 4 functional regions. What are they?

A
  1. Outer segment
  2. Inner segment
  3. Cell body
  4. Synaptic terminal
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37
Q

Which type of photoreceptor has a structure consisting of a cylindrical outer segment that has of free floating discs separated from the cell membrane

A

Rods

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38
Q

Which type of photoreceptor has a shorter, tapered outer segment with discs that are continuous with the cell membrane

A

Cones

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39
Q

True/false: rods and cones have different functions and different sensitivity to light.

A

True

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40
Q

Which type of photoreceptor can signal the absorption of a single photon and are responsible for vision under dim illumination?

A

Rods

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41
Q

Which type of photoreceptor is less sensitive to light?

A

Cones.

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42
Q

______ are responsible for vision in day light

A

Cones

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43
Q

Which photoreceptor has faster responses: rods or cones

A

Cones

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44
Q

Which photoreceptor has responses that can saturate as light level increases.

A

Rods

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45
Q

Which photo receptor is more sensitive to light?

A

Rods

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46
Q

Which photoreceptor is not sensitive to color?

A

Rods

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47
Q

In Night Vision only _____ are active, so all functional photoreceptors have the same absorption spectrum and the brain cannot distinguish colors.

A

Rods

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48
Q

Primates have ____ type of rod and ___ types of cones.

A

1

3

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49
Q

What are the three types of cones found in primates?

A
  1. S cones (short)
  2. M cones (medium)
  3. L cones (long)
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50
Q

The three types of cones in primates each detect different wave lengths, what are they?

A
  1. Short-wave (S cones)
  2. Medium-wave (M cones
  3. Long-wave (L cones)
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51
Q

The human retina contains about _____ million rods and ______ million cones.

A

100

6

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52
Q

In what structure of the retina are cones mostly found?

A

The fovea

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53
Q

______ are found mostly in the rest of the retina outside the fovea.

A

Rods

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54
Q

At night the central fovea is blind due to the absence of ____

A

Rods.

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55
Q

______ is the visual pigment in rod cells.

A

Rhodopsin

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56
Q

Rhodopsin has two components. What are they?

A
  1. Opsin
  2. Retinal
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57
Q

What is opsin and where is it found?

A

It is the protein portion of rhodopsin.

It is embedded in the disc membrane

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58
Q

______ does not by itself absorb light.

A

Opsin

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59
Q

What is retinal and where is it located?

A

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

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60
Q

The absorption of a photon by _____ causes it to flip from the 11-cis configuration to the all-trans configuration

A

Retinal

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61
Q

In phototransduction, in the dark _____ ions flow into the photoreceptor through _______ cation channels that are activated by the ________ cyclic guanosine 3’ - 5’ monophosphate (cGMP).

A

Na+

Non-selective

Second messenger

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62
Q

In phototransduction, the shape transition of the ______molecule causes a conformational change in the ______which triggers the second step of phototransduction.

A
  1. Retinal
  2. Opsin.
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63
Q

The retinal triggered conformational state change in opsin (the activated state) is called_____

A

Meta rhodopsin II

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64
Q

Is the meta rhodopsin II state stable or unstable?

A

Unstable

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65
Q

The ________state splits within minutes, yielding ______ and all-trans ______

A

Meta rhodopsin II

Opsin

All-trans retinal

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66
Q

In phototransduction, the all-trans______ is transported to pigment epithelial cells where it is reduced to all-trans ______.

A

Retinal

Retinol (vitamin A)

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67
Q

Retinol is a precursor of _______ which is eventually transported back to the rods in phototransduction

A

11-cis retinal

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68
Q

How does phototransduction occur?

A
  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

  1. All-trans retinal is transported to pigment epithelial cells, where it is reduced to all-trans retinol.
  2. 11-cis retinal is subsequently transported back to the rods.
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69
Q

In phototransduction, in the absence of light, _______is inactive because it is bound to a molecule of ______(GDP)

A

Transducin

Guanosine diphosphate

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70
Q

In phototransduction when light is present, activated rhodopsin in the form of ________diffuses within the disc membrane where it encounters _______

A

Meta rhodopsin

Transducin

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71
Q

In phototransduction the exchange of GDP for GTP occurs when _________

This leads to the dissociation of the Transducin _______

A

Meta rhodopsin II diffuses into the disc and encounters Transducin

Alpha subunit

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72
Q

What is Transducin?

A

Transducin is a G protein naturally expressed in vertebrate retina rods and cones and it is very important in vertebrate phototransduction.

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73
Q

Meta rhodopsin II can activate hundreds of additional Transducin molecules by _____the response of a cell to light

A

Amplifying

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74
Q

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.

A

Alpha subunit

cGMP

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75
Q

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 ______

A

cGMP

cGMP, closed

cGMP, open

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76
Q

In phototransduction, Meta rhodopsin II is inactivated when is is phosphorylated by a _________

A

Rhodopsin kinase

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77
Q

In phototransduction, larger responses are terminated quicker:

In the light, the internal concentration of _____ drops and accelerates the phosphorylation and inactivation of _______

A

Ca2+

Rhodopsin

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78
Q

In darkness, the concentration of cGMP in the cytoplasm is _______, the cGMP gated channels are open and the photoreceptor is __________

A

High

Depolarized

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79
Q

In light, the concentration of cGMP is ______, the cGMP gated-channels are closed and the photoreceptor is ______

A

Low

Hyper polarized

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80
Q

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

A

Vitamin A (retinol)

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81
Q

In color vision, each type of cone in the human retina produces a variant of the _____ protein

A

Opsin

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82
Q

In color vision, the various cone opsins differ in their ________. Efficient light absorption depends on the ______ of light.

A

Absorption spectrum

Wavelength

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83
Q

Red light (longer wavelengths) excites _____ cones more than M cones

Whereas, green light excites _____cones more then L cones

A

L cones

M cones

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84
Q

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.

A

True

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85
Q

The ability of the brain to compare signals from different _______ is the basis of color vision.

A

Cone types.

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86
Q

In the synaptic outer layer, bipolar _______cells have broadly absorbing dendrites that spread laterally in the outer plexiform layer where they contact photoreceptors.

A

Horizontal

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87
Q

Horizontal cells are excited by _______released by photoreceptors. Horizontal cells are electrically coupled

A

Glutamate

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88
Q

What is the function of horizontal cells?

A

To measure the average excitation of the photoreceptor population. This signal is then fed back onto the photoreceptors.

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89
Q

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.

A
  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.

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90
Q

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

A

Hyper polarized

Depolarized

Bipolar layer

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91
Q

Photoreceptors form synapses with different ______cells

A

Bipolar

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92
Q

In the dark, photoreceptors are depolarized and release _______ continuously.

A

Glutamate

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93
Q

In the light, photoreceptors are hyper polarized and do not release ____

A

Glutamate

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94
Q

What are the two type of bipolar cells that help carry out vision?

A
  1. On cells
  2. Off cells
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95
Q

On bipolar cells are activated by _____

A

Light

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96
Q

Off bipolar cells are activated by ______

A

Darkness

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97
Q

Off bipolar cells express an _______ glutamate receptor.

When glutamate is released by the photoreceptors in ________, the off cells _______

A

Ionotropic

Darkness

Depolarize

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98
Q

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______

A

Metabotropic

Light

Hyper polarize

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99
Q

In darkness, off bipolar cells are ______ and on bipolar cells are ___

A

Depolarized

Hyper polarized

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100
Q

In daylight, off bipolar cells ______ because glutamate is no longer released by photoreceptors.

A

Inactivate. (Hyper polarize)

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101
Q

On bipolar cells ______ when glutamate is no longer released by photoreceptors in daylight

A

Activate (depolarize)

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102
Q

In daylight, off bipolar cells are _____ and on bipolar cells are _______

A

Inactivated

Depolarizes

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103
Q

True false: on and off bipolar cells have different morphologies.

A

True

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104
Q

How do does the morphology of on and off cells differ?

A

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.

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105
Q

What type of neuron are amacrine cells?

A

A type of interneuron.

106
Q

In each layer bipolar cells connect to _______cells and to ______cells

A

Retinal ganglion cells

Amacrine cells.

107
Q

On bipolar cells connect to ____ retinal ganglia cells and off bipolar cells connect to ______ganglia cells.

A

On

Off

108
Q

_________cells have broadly arborizing dendrites that spread laterally into the inner plexiform layer where they contact the retinal ganglion cells

A

Amacrine

109
Q

____released by bipolar cells excite Amacrine cells, which are electrically coupled

A

Glutamate

110
Q

What is the function of Amacrine cells?

A

They measure the average excitation of bipolar cell population and this signal is fed back to the bipolar cells through inhibitory synapses.

111
Q

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.

A

Photoreceptor layer

Retinal ganglion

112
Q

What is the function of retinal ganglion cells?

A

To take info from the retina to the brain (the collect info from bipolar cells)

113
Q

Most retinal ganglion cells fire action potentials ____even in complete darkness or constant illumination.

A

Spontaneously

114
Q

What are the two major types of retinal ganglion cells?

A
  1. On
  2. Off
115
Q

When light intensity increases _____retinal ganglion cells fire mor rapidly and the _____ retinal ganglion cells fire more slowly

A

On

Off

116
Q

When light intensity decreases ____retinal ganglion cells fire more rapidly and the _____ retinal ganglion cells fire more slowly

A

Off

On

117
Q

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.

A

Light intensity changes rapidly over time.

118
Q

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.

A

On

Off

119
Q

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 ____.

A

Retinal ganglion cells

Brain

Thalamus

120
Q

What is the thalamus?

A

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
Q

In the geniculostrite pathway, Axons of retinal ganglion cells extend to a midline crossing point called the ______

A

Optical chiasm

122
Q

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

A

Temporal

Nasal

123
Q

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.

A

Nasal

Visual cortex

124
Q

In the geniculostrite pathway ____layers receive information from each eye.

A

6

125
Q

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 _____

A

Nasal

Temporal

Thalamus

126
Q

The lateral geniculate nucleus in primates consists of _____layers, each of which receives input from either the ipsilateral or controlateral eye.

A

6

127
Q

Each layer of the _______ contains a map on the controlateral hemifield, thus _____ concordant maps are stacked on top one another.

A

Lateral geniculate nucleus

6

128
Q

The thalmic neurons relay retinal information to the _____

A

Primary visual cortex.

129
Q

How Many visual Cortices are there and what are they?

A

3

  1. Primary visual cortex (V1)
  2. Secondary visual cortex (V2)
  3. Tertiary visual cortex (V3)
130
Q

The ____ visual cortex constitutes the first level of cortical processing of visual information.

A

Primary

131
Q

From the primary visual cortex, information is transmitted over two major _____ pathways. What are these pathways.

A

Parallel

Dorsal and ventral pathways

132
Q

What is the ventral pathway?

A

It projects to the temporal lobe ( the region of the brain involved in object recognition).

133
Q

What is the dorsal pathway? (In vision)

A

It projects to the parietal lobe (region of the brain involved in spatial reasoning)

134
Q

The _____ and ______ parallel pathways are interconnected and share information in vision

A

Ventral and dorsal

135
Q

True/false: the number of functionally discrete areas of visual cortex is the same between species.

A

False. It varies between species

136
Q

Have all visual areas been identified in humans?

A

No

137
Q

_____ is a tool that has made it possible to establish what type of information these discrete areas of the visual cortex are processing.

A

fMRI.

138
Q

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

A

Photoreceptor

Photon

Amplifying

Photoreceptor

Glutamate

Rods

Cones

139
Q

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 ____

A

Photoreceptors

Retinal ganglion neurons

Phototransduction

140
Q

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

A

True.

141
Q

The somatosensory system serves 3 functions. What are they?

A
  1. Proprioception
  2. Exteroception
  3. Interoception
142
Q

What is proprioception?

A

The detection of self

143
Q

What is exteroception?

A

Detection of the outside world

144
Q

What is interception?

A

Detection of the internal organs

145
Q

All the somatic senses are carried out by two types of sensory neurons. What are they?

A
  1. Dorsal root ganglion neurons
  2. Trigeminal neurons
146
Q

Trigeminal neurons primarily innervate the ______

A

Face

147
Q

Dorsal root ganglia primarily innervate the ____

A

Trunk and limbs

148
Q

The Trigeminal neurons and dorsal root ganglia are the _______ of the somatosensory system.

A

Primary receptor cells.

149
Q

Trigeminal ganglia and dorsal root ganglia innervate what structures (4 of them)

A
  1. Skin
  2. Muscle
  3. Joint capsules
  4. Viscera
150
Q

The dorsal root ganglia snd Trigeminal ganglion neurons transform _______ into electrical signals and transmit these signals to the ____\

A

Somatosensory stimuli

Brain

151
Q

The cell bodies of the dorsal root ganglion neurons are located in the ____ of the spinal cord.

A

Dorsal horn

152
Q

What type of neurons are dorsal root ganglion neurons?

A

Pseudo- unipolar

153
Q

What are pseudo unipolar neurons?

A

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
Q

Dorsal root ganglia project two axons: one to the ______ and one to the _______

A

Periphery

Brain

155
Q

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.

A

Receptors

Thalamus

156
Q

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 _______

A

Primary afferent fiber.

157
Q

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 ________.

A

Peripheral nerve.

158
Q

The different modalities of somatic sensation are mediated by different types of primary afferent fiber. Each type varies in _____ and _______.

A

Diameter

Conduction velocity

(Myelin sheath)

159
Q

True/false: all sensory neurons are myelinated.

A

False.

160
Q

Peripheral nerve fibers innervate the skin. These are called sensory or ___ nerves. The can also innervate muscle; these nerves are called ______neurons

A

Cutaneous

Motor

161
Q

Each type of nerve can be further divided into subgroups based on properties related to its axon. What are these properties (3 of them)?

A
  1. Diameter
  2. Myelination
  3. Conduction velocity
162
Q

Sensory neurons are divided into the ___,____,____, and ____fibers

Whereas motor neurons are divided into the ___,____, ____, and ____ fibers

A

A(alpha), A(Beta), A(delta), and C

I, II, III, and IV

163
Q

Which type of cutaneous nerve has the largest diameter)?

Which type of motor neuron has the largest diameter)?

A

A(alpha) at 12-20 micro meters.

I

Fastest conductance velocity

164
Q

Which type of cutaneous nerve has the smallest diameter for a myelinated nerve?

Which type of myelinated motor neuron has the smallest diameter?

A

A(delta) at 1-6 micro meters

III

165
Q

Which type of cutaneous nerve is unmylinated?

Which type of motor neuron is unmylinated?

A

C.

IV

Smallest diameter (0.2 to 1.5 um) slowest conduction velocity

166
Q

The axons of A(alpha) and A(beta) cutaneous neurons have a large Diameter and are ______. These neurons innervate the cutaneous ____organs

A

Myelinated

Mechanosensing

167
Q

The axons is A(delta) neurons have small diameter and are myelinated. These neurons innervate the _____ and respond to ____ and ______ stimuli.

A

Skin

Thermal
Noxious

168
Q

The axons of C neurons have a small diameter and are unmyelinated. These neurons innervate the skin and sense ____ and ___ stimuli

A

(thermal and noxious

Anything that can cause pain

169
Q

Group I motor neurons innervate muscle-spindle receptors and the _______organ. These neurons signal______ and _______

A

Golgi tendon

Muscle strength

Contractile force

170
Q

Group II motor neurons innervate the receptors in ______. These neurons signal ________

A

Joint capsules

Proprioception

171
Q

Group III and Group IV motor neurons innervate the ____ and _____and signal ______

A

Muscles and joints

Harsh movement

172
Q

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)

A

Touch and Proprioception

173
Q

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.

A

Thermosensation and pain.

174
Q

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 ______

A

2

1

Early mild perception

Later painful/pungent perception

175
Q

_______ 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.

A

Electromyography

Compound

176
Q

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]

A

Electric intensities

Largest , A(alpha)

A(beta)

A(delta)

C wave (delta wave + single flattish C peak)

177
Q

In electomyography the sensation evoked by the different waves goes from barely perceptible to burning pain. ____ is usually perceived last.

A

Burning pain.

178
Q

Somatosensory neurons detect physical deformations of the ____. All stimuli are transformed into electrical signals by specialized ______

A

Skin

Receptors.

179
Q

The sense of touch is mediated by ___types of mechanoreceptors

A

8

180
Q

The sense of touch on the hand is mediated by 4 types of mechanoreceptor. What are they?

A
  1. Meissner corpuscle
  2. Merkel disk receptor
  3. Pacinian corpuscle
  4. Ruffini ending
181
Q

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

A

Continuously fires

Motion.

182
Q

In mechanoreceptors, mechanical distension (physical deformations) are transduced into electrical signals by the physical action of the stimulus on the _____ channels in the membrane.

A

Cation

183
Q

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.

A

Meissner corpuscle

Merkel cells

Pacinian corpuscles

Ruffini endings

184
Q

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

A

Meissner corpuscles and Merkel cells

Pacinian corpuscles and Ruffini endings

185
Q

________ are the most abundant receptor organ in the hand. They are globular, fluid filled structures.

A

Meissner corpuscles

186
Q

Meissner corpuscles detect the _____ contact of the hand with surfaces and low frequency vibrations.

A

Initial.

187
Q

Meissner corpuscles are innervated by ______ adapting fibers.

A

Rapidly (RA1)

188
Q

________ 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.

A

Merkel cells

Amount of pressure

189
Q

Merkel cells are innervated by ______adapting fibers

A

Slowly (SA1)

190
Q

_______ 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

A

Pacinian Corpuscles

191
Q

Pacinian corpuscles are innervated by _____ adapting fibers.

A

Rapidly (RA2)

192
Q

____ 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

A

Ruffini endings

Stretch

193
Q

Ruffini endings are associated with _____adapting fibers

A

Slowly (SA2)

194
Q

The 4 major types of mechanoreceptors have distinct morphologies.

They also differ in the _____ as well as in their responses to ____

A

Size of their receptive fields

Touch stimuli

195
Q

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.

A

Cations (Na+, Ca2+)

196
Q

Piezo receptors have ____ trans membrane domains

A

38

[these receptors are ion channels invoked in touch]

197
Q

Done somatosensory receptors also express pain receptors (nociceptors).

These nocieptive neurons can be divided into two categories. What are they?

A
  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
Q

Somatosensory neurons express pain _____that detect different temperatures.

A

Thermoreceptors

199
Q

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?

A

Warm receptors
Cool receptors
Hot receptors
Cold receptors

200
Q

A(delta) fibers are low threshold _____sensing fibers and some C fibers are high threshold ______ sensing fibers

A

Cool

Cold

201
Q

____ fibers respond to rapid drops in temperature

_____ fibers respond to extremely cold temperatures

A

A(delta)

C

202
Q

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

A(delta)

C

203
Q

Some A(delta) and C fibers are heat sensing fibers and act as simple thermometers. Their firing rates __ as temperature rises

A

Increase

204
Q

The receptor genes transforming temperatures into electrical signals belong to the _______ (TRP) gene family

A

Transient potential receptor ion channel

205
Q

Are TRP channels selective or non selective?

A

Non selective

206
Q

The cool sensing receptor ____ responds to temperatures of <25 degrees C

And the cold sensin receptor _____ responds to temperatures <17 degrees C

A

TRPM8

TRPA1

207
Q

_____ and _____ are warm sensing receptors

A

TRPV3 and 4

208
Q

_____ and _____ are heat sensing receptors

A

TRPV1 and 2

209
Q

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

A

Capsaicin

Menthol

210
Q

Somatosensory information reaches the central nervous system through ____ spinal nerves and ___ cranial nerves

A

31

12

211
Q

The skin of the tissue innervated by the afferent fibers that belong to a single nerve is called a _____

A

Dermatome

212
Q

The muscle innervated by the efferent fibers that belong to the same nerve is called a ______

A

Myotome

213
Q

How many dermatomes are there along the human body?

A

43

214
Q

Fibers that convey the somatosensory information collected from a dermatome are bundled together as they enter the _____

A

Dorsal root ganglia

215
Q

Large and small diameter fibers separate into _____ divisions

A

Medial snd lateral

216
Q

The medial division contains the _____ fibers that transmit proprioceptive info from a dermatome

A

A(alpha and beta)

217
Q

The lateral division contains the ____ and _____ fibers that transmit noxious and thermal info from a dermatome

A

A(delta) and C

218
Q

All somatosensory fibers connect to the ______

But A(alpha and beta) fibers also connect to the _____ of the brain stem

A

Thalamus

Medulla

219
Q

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 ______

A

Topographically

Homunculus (Latin for little man)

220
Q

Dorsal column medial lemniscal system relays tactile and Proprioceptive information from the ____ and the ____ fibers first to the medulla and then to the ___

A

A(alpha and beta)

221
Q

The anterateral system relays noxious and thermal information from the ___ and ___ fibers directly to the thalamus

A

A(delta) and C

222
Q

The thalamus connects to the somatosensory cortex. The dorsal column medial lemniscal system and the anterolateral system form two ______pathways

A

Parallel

223
Q

Neurons of the medulla cross to the contralateral side and relay information directly to the _____

A

Thalamus

224
Q

True/false: In the dorsal column medial lemniscal system, thalamical neurons connect to cortical neurons such that the topographical relationships between neurons is preserved.

A

True

225
Q

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 ____

A

Interneurons

Brainstem

226
Q

Touch and pain pathways are ___

Pain has an emotional component to it.

A

Parallel

227
Q

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.

A

True

228
Q

In the primary somatosensory cortex there are five areas that each contain a somatotopic map of the body called the_____

A

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
Q

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

A

Parallel

230
Q

Somatosensatin results from _____actions of multiple systems.

A

Parallel

231
Q

True/false: sending is learning.

A

True.

232
Q

What is the nasal cavity?

A

A large air filled space located behind the nose where it contacts the olfactory epithelium

233
Q

Volute molecules enter through the _____

A

Nasal cavity

234
Q

The olfactory epithelium consists of both ______ and ______\

A

Olfactory sensory neurons

Glial cells

235
Q

True/false: olfactory sensory neurons are short lived but are continuously regenerates through neurogenesis.

A

True. They can regenerate on a monthly basis

236
Q

Olfactory sensory neurons extend their dendrites in the _______

A

Nasal cavity

237
Q

Olfactory sensory neurons project their axons to one of the 2,000 glomeruli in the brain into the ______

A

Olfactory bulb

238
Q

What type of neuron are olfactory sensory neurons?

A

Bipolar neurons

239
Q

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 _____

A

Celia

Celia

240
Q

Who discovered olfactory receptors?

A

Buck and axel

241
Q

What were the 3 assumptions made by buck and axel when they were lookin for olfactory receptors?

A
  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
Q

Vertebrae olfactory receptors belong to a large multi Gene family of ______ which is evolutionarily conserved and found in all vertebrae species

A

GPCRs

243
Q

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

A

Pocket

Pocket

244
Q

When an oder molecule combines to a GPCR, the ______ dissociates fro the Gs protein complex and activates an _____cyclase

A

alpha-s subunit

Adenylyl

245
Q

______ binds to cGMP gated cation channels causing depolarization in the olfactory sensory neuron

A

cGMP

246
Q

The human nose has ____ olfactory receptors while the mouse has ______ olfactory receptors.

This number is highly variable across species

A

400

1000

247
Q

True/false: each olfactory sensory neuron expresses many types of olfactory receptors

A

False. Each sensory neuron expressed only ONE type of olfactory receptor

[one to one rule]

248
Q

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.

A

True

249
Q

Many animals have evolved a chemical language to communicate with conspecifics or other species. These chemicals are called _____

A

Pheromones

250
Q

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.

A

Vomeronasal epithelium

251
Q

Olfactory sensory neurons in the vomeronasal organ express different types of _____: the V1R and the V2R

A

GPCRs

252
Q

True/false: vomeronasal receptors are expressed similarly to the main olfactory receptors and follow the one to one rule.

A

True

253
Q

True/false: a similar vomeronasal gerne family does not exist in mist apes.

A

True

254
Q

True/false: humans have a vestigial vomeronasal organ

A

True. But is does not express receptors.

255
Q

What’s the closest molecule humans have to a pheromone?

A

Androstenone

256
Q

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

A

Androstenone

Polymorphisms

257
Q

I. Olfaction, the mitral and tufted cells extend their dendrites into individual glomeruli project to _____ higher brain centers.

These are the

A

5

  1. Anterior olfactory nucleus
  2. Olfactory tubercle
  3. Piriform cortex [not called olfactory Cortex for whatever reason]
  4. Amygdala
  5. Entorhinal cortex
258
Q

True/false: mitral and tufted cell in the Piriform vortex appear to be largely disorganized?

A

True.

259
Q

In the Piriform cortex, oders activate sparse ensembles of neurons distributed across the entire ___\__

A

Piriform cortex

260
Q

True / false: the same neurons can respond to many dissimilar orders.

A

True.

261
Q

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.

A

Olfactory bulb

Piriform cortex

[olfactory epithelium—> bulb—> Piriform cortex]

Cellular Neurobiology (5 decks)

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