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CNS > Peripheral Somatosensory Mechanisms > Flashcards

Peripheral Somatosensory Mechanisms Flashcards

1
Q

What are the classifications of SS sensations?

A
  1. Exteroceptive division
  2. Interoceptive division
  3. Proprioceptive division
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2
Q

Receptors of Exteroceptive SS sensations

A
  1. Mechanoreceptors [cutaneous touch]
  2. Thermoreceptors [maintain homeostasis]
  3. Nocioreceptors [respond to harm]
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3
Q

Receptors of Interoceptive SS sensations

A
  1. Mechanorecptors [responds to distension]
  2. Nocioceptors
  3. Chemoreceptors
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4
Q

Receptors of Proprioceptive SS sensations

A
  1. Proprioceptor
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5
Q

What are the two major functions of the sensory neurons?

A
  1. Transduction [encodes stimuli into electrical signals]
    1. Transmission [propogates electrical signal to CNS]
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6
Q

Describe the charactersitic of sensory receptors

A

Each receptor is more specific for a single stimuli and has a low threshold for that stimule [adequate stimuli] and a higher or no threshold for other stimuli [inaduaqate stimuli]

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7
Q

What receptor is responsible for light flutters?

A

Meissner’s corpuscle

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8
Q

What receptor is responsible for sustained touch?

A

Merkel cell

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9
Q

What receptor is responsible for vibration?

A

Pacinian corpuscle

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10
Q

What receptor is responsible for skin stretch and sustained pressure?

A

Ruffini corpuscle

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11
Q

What receptor is responsible for pain, itch, tickle and temperature?

A

Free nerve endings

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12
Q

How are stimulis transduced into electrical signals?

A

The stimule changes receptor membrane permeability, allowing some ions to diffuse through channels. This change is called receptor [generator potential]. If the stimuli is strong then the receptor potential reaches AP thresholf and AP is generated

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13
Q

Characteristics of Receptor Potential

A

Graded

  1. stronger stimuli→ larger amplitude of receptor potential
    • increased amplitude →increased frequcency of AP
  2. longer stimuli→ longer duration of receptor potential
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14
Q

What is sensory adaption?

A
  • Phasic receptors adapt to constant stimuli [why we can stop paying attention to constant stimuli and only notice when it changes]
  • Rapid adaptation is done by phasic receptors [Pacininan’s and Meissener’s corpuscle]
    • detects change
  • Slow adaption is done by Tonic receptos [Proprioceptors, Nocioceptors, Merkel cells]
    • gives continous info about the stimuli
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15
Q

What is the effect of a mutation in Piezo2 gene?

A

severe deficits in repsonse to touch

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16
Q

What is Piezo2 channel?

A

non-specific cation permeable channel

17
Q

Explain the process of sensory transduction in slow adapting mechanoreceptors

A

Skin deformation [pressure on skin] activates Piezo2 channels in Merkel cell, depolarizing it and allowing voltage-gated CaV channels in the Merkel cell to open and release neurotransmitter continuously.

Binding of the neurotransmitter further depolarizes the neurite, producing sustained firing in the axon.

18
Q

What are the slow adapting touch and pressure receptors?

A
  1. Merkel cell
  2. Ruffini ending
19
Q

What are the fast adapting touch and pressure receptors?

A
  1. Meissner Corpuscle
  2. Pacinian Corpuscle
  3. Hair follicule
20
Q

What receptor is responsible for flutter and light touch?

A

Hair follicle

21
Q

What chemoreceptor signals for thirst?

A

Osmoreceptors

22
Q

What chemoreceptors trigger for hunger?

A

Hypothalamuc chemoreceptors

23
Q

What neurotransmitter is implicated in itching?

A

Histamine

24
Q

What are the different thermorecptors and to which degrees do they respond to?

A
25
Q

What is TRPM8?

A

[thermorecptor]

nonselective cation channel expressed in small diameter trigeminal and dorsal root ganglion neurons in which cooling and menthol evoke inward depolarizing currents and intracellular calcium rises.

26
Q

Describe the structure of thermal nocioceptors

A

In peripheral endings of small diameter, thinly myelinated axons

27
Q

Describe the structure of mechanical nocioceptors

A

In endings of thinly myelinated axons. (stabbing, squeezing, pinching of the skin)

28
Q

describe the structure of polymodal nocioceptors

A

At ends of small-diameter, unmyelinated C axons that conduct more slowly (dull, burning pain, diffusely localised, poorly tolerated).

29
Q

What are some examples of Polymodal nociceptors?

A
30
Q

What two factors determine the conduction velocity of the nerve fibers?

A
  1. diameter
  2. degree of demyelination
31
Q
A

CNS (10 decks)

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