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BIOL 404 FINAL > Sensory Receptors > Flashcards

Sensory Receptors Flashcards

1
Q

sensory receptors code for ____,_____ and ______

A

intensity (stimulus strength), duration (temporal aspects of stimulus) and location (the spatial distribution of the stimulus)

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2
Q

mechanoreceptors open in response to _____ resulting in _____

A

stretch, depolarization of mechanosensory neurons

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3
Q

pain are mechanosensation are ______

A

separate pathways

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4
Q

pain pathways:

A

cross over in the spinal cord and move upward to the caudal medulla

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5
Q

label this diagram:

A

a: dorsal root ganglion cells
b: mechanosensory afferent fiber
c: pain and temp afferent fiber
d: receptor ending

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6
Q

somatosensory afferents _____ from the ____ to CNS

A

convery info, skin surface, CNS

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7
Q

what transmits sensation from the head to CNS?

A

trigeminal nerve (CN V)

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8
Q

sensory info from the rest of the body is relayed by ____ pairs of afferent and efferent spinal nerves

A

31

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9
Q

the spinal nerves are:

A

Cervical nerves (8)
Thoracic nerves (12)
Lumbar nerves (5)
Sacral nerves (5)
Coccygeal nerves (1)

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10
Q

dermatome:

A

a region innervated by a single pair of spinal or cranial nerves.

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11
Q

sensory nerves project to the _____ and _______ in the parietal lobe

A

primary somatosensory (S1), secondary somatosensory cortex (S2)

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12
Q

secondary sensory order neurons from the _____ integrate in the _____ at the:

A

somatosensory cortex, thalamus, Ventral posterior medial nucleus (VPM) and Ventral posterior lateral nucleus (VPL)

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13
Q

the medial lemniscal pathway deals with…

A

sensation from the dorsal column (upper and lower body)

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14
Q

MPL: lower body:

A

enters spinal cord, then synapses at the gracile nucleus.

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15
Q

MPL: upper body:

A

enters spinal cord, then synapses at the cuneate nucleus.

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16
Q

both the gracile and cuneate nucleus are in the ______; this is where _______

A

caudal medulla, crossing over occurs

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17
Q

Where does the sensory information from the Medial Lemniscal Pathway terminate in the brain?

A

Terminates in the ventral posterior lateral nucleus of the thalamus before projecting to the primary somatosensory cortex.

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18
Q

How is sensory information from the upper and lower body organized in the somatosensory cortex?

A

terminates in different places of the somatosensory cortex, maintaining somatotopic organization

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19
Q

trigeminal lemniscal pathway deals with..

A

sensation from the face

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20
Q

TLP: sensory afferents enter the ____ in the midbrain, and the _____

A

nucleus of the trigeminal complex, crosses over

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21
Q

TLP: on the contralateral side, info rises until it ____ at the _____

A

synapses, ventral posterior medial nucleus of the thalamus

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22
Q

TLP: from here, neurons project to the _____

A

primary somatosensory cortex

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23
Q

T/F: sensory receptors are distrivuted evenly throughout the body

A

false, the amount of receptors present correlates with sensivity

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24
Q

what does lateral inhibition increase?

A

acuity

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25
Q

what does convergence do?

A

decreases acuity but increases sensitivity

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26
Q

the representation of the body is not _____ in the _______.

A

proportional, somatosensory cortex

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27
Q

neurons in the _____ form _______ columns

A

somatosensory cortex, functionally distinct

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28
Q

what streams are present in each column?

A

for rapidly-adapting and slowly-adapting afferents.

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29
Q

what can the proportion of the somatosensory cortex devoted to a body part be increased by?

A

further activity

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30
Q

what can it be decreased by?

A

lack of activity/amputation.

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31
Q

what does chronic two photon imaging reveal?

A

neural connectivity at the level of single synapses is affected by sensory deprivation from stroke

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32
Q

What stimulus features can be encoded by neurons in the Secondary Somatosensory Cortex/Area 2?

A

orientation and direction

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33
Q

when does optimum firing occur in secondary somatosensory cortex neurons?

A

occurs when an object is in a certain orientation and direction

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34
Q

how is optimum firing occuring with a certain direction acheived?

A

as higher-order neurons combine the receptive fields from multiple excitatory and inhibitory neurons.

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35
Q

Under what conditions will a neuron in the secondary somatosensory cortex fire?

A

If excitatory input is preceded by a lot of inhibitory input, or if there is simultaneous inhibitory and excitatory input, the cell won’t fire.**
The cell fires only if the stimulus moves in a certain direction in the receptive field.

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36
Q

types of sensory afferents

A

muscle spindles, golgi tendon organs, touch receptors, myelinated free nerve endings, and unmyelinated free nerve endings

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37
Q

muscle spindles:

A

(1a, A-alpha): for proprioception; large & myelinated (fastest)

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38
Q

golgi tendon organs:

A

(1b, A-alpha): for proprioception; large and myelinated (fastest)

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39
Q

touch receptors

A

(II, A-beta): Merkel, Meissner, Pacinian, and Ruffini cells.

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40
Q

myelinated free nerve endings

A

(III, A-delta): for pain, temperature.

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41
Q

unmyelinated free nerve endings

A

(IV, C): pain, temperature, itch; slowest.

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42
Q

name the encapsulated skin receptors

A

meisnner corpuscle, ruffini corpuscle, pacinian corpuscle

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43
Q

name the non-encapsulated skin receptors

A

merkel cell-neurite complex, free nerve endings

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44
Q

meisnner corpuscle

A

responds to pressure and grip
- Small receptive fields
- Rapidly-adapting
- A-beta afferents

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45
Q

ruffini corpuscle

A

responds to stretching and proprioception
- Large receptive fields
- Slowly-adapting
- A-beta afferents

46
Q

pacinian corpuscle

A

respond to vibration
- Large receptive fields
- Rapidly-adapting
- A-beta afferents

47
Q

merkel cell-neurite complex

A

responds to form and texture.
- Small receptive fields (high spatial acuity)
- Slowly adapting
- A-beta afferents
*semi-neuron; doesn’t fire, only amplifies responses

48
Q

label this diagram:

A

a: free nerve endings
b: meissner
c: merkel cell-neurite complex (touch dome)
d: ruffino corpuscle
e: pacinian corpuscle

49
Q

for each type of stimuli….

A

these receptors code for different aspects

50
Q

stimulus features are encoded by the ___ and ____ of receptor that is activated

A

type and location

51
Q

What is the primary objective of microneurography?

A

measure sensory activity

52
Q

How does microneurography record sensory activity?

A

Implant fine electrodes into the skin towards nerves.
Record action potentials.

53
Q

How does microneurography avoid nerve damage?

A

Use thin electrodes (200 microns in diameter).

54
Q

label this diagram:

A

a: stimulus
b: merkel - SA
c: meissner - RA
d: ruffini - SA
e: pacinian - RA
f- small receptive
g: large receptive fields

55
Q

cre recombinase

A

cuts genes at loxP sites

56
Q

by using a specific promoter to drive Cre expression….

A

you can delete a certain gene to create a tissue-specific knockout.

57
Q

cre/lox system

A

You can also cross it with a strain with a stop-cassette preceded target gene, to get expression of the target gene in only a certain type of cell.

58
Q

proprioception

A

Sensing “oneself” and where parts of our body are in 3-dimensional space

59
Q

what 3 mechanoreceptors are involved in proprioception

A

Muscle spindles
Golgi tendon organs
Ruffini endings (in joints)

60
Q

in proprioception, muscle spindles contain

A

2 types of contracile fibers

61
Q

what are the two types of contractile fibers?

A

extrafusal and intrafusal fibers

62
Q

extrafusal fibers

A

make up the bulk of the muscle.
- Force-generating, innervated by alpha motor neurons

63
Q

intrafusal fibers

A

are involved in detecting changes in muscle length.
- Are arranged in parallel.
- Two kinds: Nuclear “chain” fibers, Nuclear “bags” fibers

64
Q

T/F intrafusal fibers are present in all fibers

A

false, they are not, mostly in smaller muscles where you need fine proprioception

65
Q

most muscle contain ____ and ____

A

2-3 bag and 4-6 chain fibers

66
Q

Nuclear bag fibers (NBFs):

A
  • Type Ia afferents
  • Phasic (code for dynamic information)
  • Form annulospiral synapses.
67
Q

Nuclear chain fibers (NCFs):

A
  • Type II afferents
  • Tonic (code for static information)
  • Form flower-spray synapses
68
Q

Gamma motor fibers (GMFs):

A
  • Code for both dynamic and static information.
  • Work to adjust the tension on the central part of the intrafusal muscle in order to keep Ia afferents near threshold, which helps it effectively encode for dynamic information.
69
Q

muscle spindles drive _____ tendon reflexes

A

knee jerk/patellar

70
Q

what happens when the muscle spindle detects a stretch of the quad?

A

the sensory neuron signals to a alpha motor neuron to extend the antagonistic hamstring muscle.

71
Q

to maintain a load, an ____ helps to ____ antagonisitc muscles to maintain resistance

A

interneuron, inhibit

72
Q

golgi tendon organs detect…

A

muscle tension, but are insensitive to passive stretch that would activate muscle spindles

73
Q

how are golgi tendon organs arranged?

A

in series with extra fusal muscles

74
Q

golgi tendon organs contain _____

A

slowly adapting Ib afferents

75
Q

what is the primary function of golgi tendon organs in muscle regulation?

A

maintain steady muscle tone

76
Q

how do GTOs respond to an expectionally heavy load on muscles?

A

GTOs relax muscle to prevent muscle damage

77
Q

describe the modulation pathway of GTOs in muscle tension

A
  • Ib afferent signals GTO.
  • Ib inhibitory interneurons are activated.
  • Inhibition of alpha motor neurons.
  • Inhibition of muscle contraction.
78
Q

gamma motor fibers get info from ____ about ____

A

GTOs, current muscle load

79
Q

What is the primary function of the dorsal spinocerebellar pathway?

A

Proprioception (sensation of body position and movement).

80
Q

Describe the route of proprioceptive input from the lower body in the dorsal spinocerebellar pathway.

A

Muscle spindles → Clarke’s nucleus → Dorsal spinocerebellar tract → Cerebellum.

81
Q

Describe the route of proprioceptive input from the upper body in the dorsal spinocerebellar pathway.

A

Muscle spindles → Ventral posterior nucleus of the thalamus → Cerebellum.

82
Q

Define nociception.

A

is the process of perceiving and responding to harmful or potentially damaging stimuli.

83
Q

where are nociceptor receptors

A

on free nerve endings that detect painful stimuli

84
Q

types of nociceptors receptors

A

thermal, mechanical, polymodal

85
Q

thermal:

A

respond to stimuli greater than 45 degrees and less than 5 degrees.
- Thinly myelinated A-delta fibers.

86
Q

mechanical

A

respond to intense pressure.
- Thinly myelinated A-delta fibers.

87
Q

polymodal

A

respond to thermal, pressure, and chemical stimuli.
- Unmyelinated C fibers

88
Q

what do transient receptor potential (TRP) channels respond to

A

painful temperatures

89
Q

TRPM8:

A

responds to painful cold stimuli.

90
Q

TRPB1:

A

responds to painful hot stimuli.

91
Q

ASIC

A

harmful pHs (H+).

92
Q

P2X/P2Y

A

detect ATP released from mechanical damage.

93
Q

NaV 1.7:

A

genetic defects can impact someone’s ability to feel pain.

94
Q

mutations w Nav 1.7

A

can cause people to not feel pain (which is harmful as one can’t sense injury), or can cause hypersensitivity to pain.

95
Q

capsaicin

A

a compound in spicy food, has vanilloid groups that activate pain receptor transient receptor potential vanilloid member 1 (TRPV1).

96
Q

TRPV1 and TRPV2

A

painful heat

97
Q

hyperalgesia

A

increased sensitivity to painful stimuli; this is seen at the site of the injury following a painful stimulus.

98
Q

an inflammatory ‘soup’ increases..

A

increases the excitability of peripheral nociceptors referred to as peripheral sensitization.

99
Q

fast pain:

A

sharp pain mediated by A-delta small myelinated fibers

100
Q

a-delta fibers in fast pain

A

make excitatory glutamatergic synapses onto projection neurons in layers 1-5 of the dorsal horn.

101
Q

slow pain

A

dull pain mediated by small, unmyelinated C fibers.

102
Q

c fibers in slow pain

A

These C fibers make excitatory glutamatergic synapses onto projection neurons in layer 1 of the dorsal horn

103
Q

inhibitory interneurons

A

reside in layer 2 (substantia gelatinosa) of the dorsal horn.
- Release enkephalins to modulate pain transmission.

104
Q

wide dynamic range of neurons

A

reside in layer 5 of the dorsal horn. These neurons receive:
- Nociceptive information from the gut via A-delta fibers (referred pain).
- Mechanical touch inputs from the skin via A-beta fibers.

105
Q

gate theory

A

in the spinal cord, pain signals can be sent up to the brain to be processed to accentuate the possible perceived pain, or attenuate it at the spinal cord itself.
-> Basically, spinal nerves decide what pain gets through and what doesn’t.

106
Q

allodynia

A

an increased sensitivity to benign, usually mechanical stimuli.

107
Q

One theory claims that the chloride reversal in these projection neurons is changed, with a

A

downregulation of the KCC2 cotransporter.

108
Q

This means that sometimes…

A

GABAergic and glycinergic input from interneurons will become excitatory and stimuli driven by mechanosensitive channels that once served to stop pain will now enhance the pain.

109
Q

anterolateral spinothalamic pathway

A

is the discriminative pain pathway.

110
Q

Nociceptive information synapses on the ______ of the spinal cord, and then crosses over.

A

ipsilateral side

111
Q

The input moves _______ up the spinal cord until synapsing on the ________of the thalamus.

A

contralaterally, ventral posterior lateral nucleus

112
Q

From here, information projects to the ________ of the cerebrum; information from the upper and lower body synapse at different locations.

A

primary somatosensory cortex

BIOL 404 FINAL (8 decks)

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