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Physiology 2 > Exam 1 - Somatic Sensation > Flashcards

Exam 1 - Somatic Sensation Flashcards

1
Q

How does a neuron respond to a sustained stimulus?

A

Decreased firing rate over time

hot tub analogy - feels hot for the first few minutes, then our bodies adapt to the temperature

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2
Q

What is another word to describe slow adaptation?

A

Tonic

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3
Q

What is another word to describe fast adaptation?

A

Phasic

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4
Q

What do tonic receptors detect?

A

continuous (sustained) stimulus strength

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5
Q

What do phasic receptors detect?

A

change in stimulus strength

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6
Q

What is the function of a mechanoreceptor?

A

They detect mechanical compression or stretching of the receptor/tissues adjacent to receptor

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7
Q

Where are type I mechanoreceptors located?

A

Outer layers of joint capsul

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8
Q

Which mechanoreceptors have a low threshold (easily fire)?

A

Type I and Type II

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9
Q

Which mechanoreceptor has tonic effects on lower motor neuron pools?

A

Type I

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10
Q

What is the difference between type I and type II mechanoreceptor adaptation rates?

A

Type I - Dynamic & fire with movement; Slowly adapting

Type II - Rapidly adapting, inactive in immobilized joints

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11
Q

Which mechanoreceptor has phasic effects on lower motor neuron pools?

A

Type II

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12
Q

Which mechanoreceptors are usually myelinated?

A

Types I-III

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13
Q

Which mechanoreceptor is also a nociceptor?

A

Type IV

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14
Q

What do Types III & IV have in common?

A

Very high threshold

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15
Q

What does type III have in common with type I?

A

Slow adaptation

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16
Q

Which mechanoreceptor is a joint version of a Golgi tendon organ?

A

Type III

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17
Q

What are the two rapidly adapting tactile receptors?

A

Meissner’s Corpuscles and Pacinian Corpuscles

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18
Q

Which tactile receptors are slowly adapting?

A

Merkel’s discs and Ruffini’s end-organ

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19
Q

Which tactile receptors have a small (superficial) receptive field?

A

Meissner’s and Merkel’s

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20
Q

Which tactile receptors have a large (deep) receptive field?

A

Pacinian Corpuscle and Ruffini’s end organ

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21
Q

Which tactile receptor is slowly adapting and has a relatively large receptive field?

A

Ruffini ending

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22
Q

At what temperature are thermoreceptors inactive but nociceptors active?

A

Below 0 C, above 50 C

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23
Q

When do thermoreceptors discharge spontaneously?

A

Under normal conditions (wide temp. range)

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24
Q

When do thermoreceptors discharge physically?

A

When skin temp. changes rapidly

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25
Q

How does the gating theory of pain work?

A

It involves inhibitory interneurons in the cord that impact nociceptor projection neurons

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26
Q

What inhibits nociceptors in the gating theory of pain?

A

C fibers (type III) - open the gate and increase nociceptive transmission

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27
Q

What stimulates nociceptors in the gating theory of pain?

A

A alpha and beta fibers (type I and II) - close the gate and decrease nociceptive transmission

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28
Q

What is secreted by C fibers? What order neuron are they?

A

First order neuron - secrete substance P and glutamate

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29
Q

What sensations do we feel when C fibers are activated?

A

Dull burning and aching pain (chemical)

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30
Q

What sensations do we feel when A delta fibers are activated?

A

Sharp, prickling pain (thermal)

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31
Q

What is the difference between the neo and paleo spinothalamic pathways?

A 
Neo = fast (A delta)
Paleo = slow (C fibers)
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32
Q

In type III (A delta) nociceptors, which neurotransmitter is released by first order neurons in the spinal cord?

A

Glutamate

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33
Q

Lateral inhibition in the somatosensory system is associated with which function?

A

enhances edges but DOES NOT improve acuity

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34
Q

T/F: A first order neuron when stimulated will both stimulate some 2nd order neurons as well as inhibit other 2nd neurons simultaneously.

A

True

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35
Q

In a hemisection of the cord, where does a loss of vibration/proprioception occur?

A

On the ipsilateral side

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36
Q

In a hemisection of the cord, where does analgesia occur?

A

Contralateral

p.s. Analgesia = inability to perceive temperature/pain

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37
Q

What is the Epicritic pathway in the somatosensory cortex?

A

Dorsal column-medial lemniscal system (precise objective info)

38
Q

What is the Protopathic pathway for the somatosensory cortex?

A

Anterolateral system (spinothalamic) - primitive feeling -

39
Q

Most vibratory signals are transmitted to the cortex via what pathway?

A

Dorsal column-medial lemniscal

40
Q

The anterolateral system transmits which signals/sensations?

A

Crude touch, nociception, temperature, tickle, itch, sexual sensation

41
Q

In the somatosensory homunculus, which area of the body would normally have the largest cortical representation?

A

hands

42
Q

Where do 1st order neurons synapse in the anterolateral/protopathic pathway?

A

Dorsal horn of the spinal cord

43
Q

Where do 1st order neurons synapse in the Dorsal column-medial lemniscal/epicritic pathway?

A

Brain stem

44
Q

Where do 2nd order neurons of both pathways cross?

A

They cross to the other side and ascend, synapsing in the thalamus

45
Q

Which pathway initiates actions?

A

Protopathic (anterolateral)

46
Q

Which pathway modifies actions?

A

Epicritic (DCML)

47
Q

Which pathway has fast/large fibers?

A

Epicritic (DCML)

48
Q

Which pathway is old phylogenetically?

A

Protopathic

49
Q

Where do 1st order neurons reside for both pathways?

A

Dorsal root ganglia

50
Q

A hemisection of the spinal cord on the right side of T5 that disrupts both ascending and descending projections would create what type of sensory defect below the lesion?

A

Loss of nociception on the left side, loss of vibration on the right side

51
Q

T/F: Most nerve cells in the SSC are responsive to only one modality.

A

True!

E.g. Deep pressure, temperature, nociception, superficial tactile

52
Q

What are the three types of neurons in Brodman areas 1 & 2 that have complex feature detection capabilities?

A
  1. Motion sensitive
  2. Direction sensitive
  3. Orientation sensitive
53
Q

What are direction-sensitive neurons?

A

Neurons which respond better to movement in one direction than in another

54
Q

What are orientation-sensitive neurons?

A

Neurons that respond best to movement along a specific axis

55
Q

What are motion sensitive neurons?

A

Neurons which respond well to movement in all directions but not selectively to movement in any one direction

56
Q

A cortical neuron in Brodman area 2 that fires strongly as a tactile stimulus is drawn across the hand from ulnar to radial but weakly from radial to ulnar is an example of…?

A

Direction sensitive neuron

57
Q

What is the major function of anandamide produced by the brain?

A

Stress induced analgesia

58
Q

What are the two endogenous cannabinoids produced by the brain?

A

Anandamide and 2-AG (2-arachidonoylglycerol)

These levels increase during exercise, contributing to ‘runner’s high’

59
Q

Projections from viscera and projections from the body will share common 2nd order projection neurons in the anterolateral spinothalamic projections. In regards to pain, this is known as…

A

Referred pain

60
Q

How can dysfunction of the cervical spine refer pain to the head?

A

Some C2 projections synapse in the nucleus of CN V (CN V supplies most of head/face, extends down to C2)

61
Q

What part of the brain will you find BM areas 5 and 7?

A

Posterior parietal cortex

62
Q

What type of information does BM area 5 integrate?

A

Tactile information from mechanoreceptors in skin with proprioceptive input from muscles and joints

63
Q

Brodman area 7 integrates stereognostic input with what special sense?

A

Visual

64
Q

Where does BM area 7 project its fibers?

A

Motor areas of the frontal lobe

65
Q

What inputs does BM 7 receive?

A

visual, tactile, proprioceptive

66
Q

How is the somatosensory cortex important in movement?

A

Initiation and guidance

67
Q

Interneurons in the cord that block nociceptive transmission by 2nd order neurons release what neurotransmitter?

A

Enkephalin (opioid)

68
Q

What neurotransmitters are considered an endogenous opioid?

A

Enkephalin and endorphins

69
Q

What are the 5 sensations of pain?

A

Pricking, burning, aching, stinging, soreness

70
Q

Where do C2 afferents synapse?

A

DRG (dorsal horn) & CN V nuclei

71
Q

What is cervical joint dysfunction?

A

Spill over of signals from cervical joints (C2) to nucleus of CN V

72
Q

What are the intracranial origins of headache?

A

Meningitis, Migraine (vasoconstriction/vasodilation), Irritation of Meninges (re: alcohol abuse or constipation)

73
Q

What are the extracranial origins of headache?

A

Muscle spasm, eye disorders, cervical joint dysfunction, irritation of nasal passages/sinuses, traction of dura (CN V)

74
Q

What is spatial summation?

A

Increasing signal strength transmitted by progressively greater # of fibers

75
Q

What is temporal summation?

A

Increasing signal strength by increasing frequency of IPS (impulses/second)

76
Q

When do we use Erlanger’s system?

A

Used in motor nerves and skin afferents

77
Q

When do we use Lloyd’s system?

A

Used for afferents from receptors in muscle and spinal joints

78
Q

What is stereognosis?

A

The ability to perceive form through touch (tests dorsal column-medial lemnicsal system)

79
Q

What are the 4 types of sensory modalities?

A

Pressure receptors
Cold receptors (thermo)
Warm receptors (thermo)
Nociceptors

80
Q

The perception of something wet on your skin is associated with stimulation of which receptors?

A

Pressure & thermo

81
Q

The perception of itching on your skin is associated with stimulation of which receptors?

A

Gentle + nociceptors

82
Q

The perception of ticklishness on your skin is associated with stimulation of which receptors?

A

Gentle + pressure receptors

83
Q

What leads to a continuous intrinsic neuronal discharge?

A

Leaky membrane to Na+/Ca++

84
Q

Most neurons are a site of ______ input and a source of _____ output

A

A. Converging
B. Diverging

Neurons that fire together, wire together

85
Q

What is synaptic afterdischarge?

A

Postsynaptic potential lasts for msec (can continue to excite neuron)

86
Q

What is a reverberatory circuit?

A

Positive feedback within circuit due to collateral fibers which restimulate itself/neighbor in same circuit

87
Q

How do we control over-excitation (e.g. seizures) in the brain?

A
  1. Fatigue of synapses
  2. Inhibitory circuits
  3. Decreasing resting membrane potential
  4. Long-term changes by down regulation of receptors
88
Q

Which mechanoreceptor is concentrated in the fingertips and found only in glabrous (non hairy) skin?

A

Meissner’s corpuscles

89
Q

Where are Pacinian corpuscles located?

A

Subcutaneous tissue

90
Q

Which mechanoreceptor is activated by stretching the skin?

A

Ruffini end organ

91
Q

Which mechanoreceptor can sense the curve of an object?

A

Merkel’s discs

Physiology 2 (2 decks)

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