Lecture 11: Sensory Physiology Flashcards

1
Q

What 2 things can be used to classify a peripheral nerve?

A

Contribution to an action potential. (Letter)

Fiber diameter, myelin thickness. (Number)

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2
Q

Aalpha nerve
Classification:
Fiber diameter:
Conduction velocity:

A

Classification: Ia, Ib
Fiber diameter: large
Conduction velocity: fast

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3
Q

C nerve
Classification:
Fiber diameter:
Conduction velocity:

A

Classification: IV
Fiber diameter: small
Conduction velocity: slow

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4
Q

What is a generator potential?

A

A stimulus, when large enough, can trigger an AP to be carried over a distance into the CNS.

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5
Q

Receptor adaptation

A

When a stimulus persists for awhile, the neural response diminishes and sensation is lost.

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6
Q

Slowly adapting receptors

A

Receptors that respond to prolonged and constant stimulation

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7
Q

Rapidly adapting receptors

A

Receptors that respond only at beginning or end of stimulus when the intensity of stimulus increases or decreases.

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8
Q

Meissner’s corpuscle
Adaptation rate:
Sensation produced:
Receptive field size:

A

Receptor Adaptation rate: RA
Sensation produced: tap, flutter
Receptive field size: small

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9
Q

Hair follicle receptors
Adaptation rate:
Sensation produced:
Receptive field size:

A

Receptor Adaptation rate: RA or SA
Sensation produced: motion, direction
Receptive field size: N/A

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10
Q

Pacinian corpuscle
Adaptation rate:
Sensation produced:
Receptive field size:

A

Receptor Adaptation rate: RA
Sensation produced: vibration
Receptive field size: large

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11
Q

Merkel disk
Receptor Adaptation rate:
Sensation produced:
Receptive field size:

A

Receptor Adaptation rate: SA
Sensation produced: touch, pressure
Receptive field size: small

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12
Q

Ruffini corpuscle
Receptor Adaptation rate:
Sensation produced:
Receptive field size:

A

Receptor Adaptation rate: SA
Sensation produced: skin stretch
Receptive field size: large

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13
Q

Where is tactile acuity highest?

A

Small receptor fields (fingertips, lips, etc).

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14
Q

Where is tactile acuity lowest?

A

Large receptor fields (calf, thigh, back, etc)

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15
Q

Pre-synaptic inhibition

A

Diminishes excitatory signal.

  1. GABA –> influx of Cl-.
  2. Hyperpolarization
  3. Less Ca++
  4. Less NT release
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16
Q

What is the use for pre-synaptic inhibition? How?

A

It helps the brain localize the signal.

The activated neuron can send collateral branches to inhibit nearby neurons, which would enlarge the sensory area.

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17
Q

3 roles of cortical processing

A

Initial processing of signal.
Integration of the initial processing into larger schemes.
Emotional response to the processing.

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18
Q

What is interesting about the somatotopic maps?

A

They can be changed (i.e. magnified (OMM) or diminished (amputation, severed nerve)).

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19
Q

What layers of the cortex are enlarged in the primary sensory cortex?

A

III and IV

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20
Q

What layers of the cortex are the main site of termination of axons from the thalamus?

A

III and IV

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21
Q

Each column within the cortex deals with what?

A

One sensory modality in one part of the body (Meissner’s of arm, free nerve endings leg, etc).

22
Q

How does sensory info arrive at its column in layer IV?

A

Via the thalamus

23
Q

What is S1 involved in?

A

Integration of the info for position sense, and size and shape discrimination.

24
Q

What is S2 involved in?

A

Comparisons between objects, sensations, etc. and whether or not something becomes a memory.

25
Q

PTO

A

High level interpretation of sensory inputs from many areas.

Analyzes spatial coordinates of self in environment. Names objects.

26
Q

Once it receives sensory, what does the primary sensory cortex send projections to?

A

Mostly back to thalamus, but also to other parts of cortex.

27
Q

What do the thalamic projections from the primary sensory cortex do?

A

Permits focusing activities

28
Q

What is the function of cortico-cortical projections?

A

It allows for linking of primary and association areas of sensory cortex.
Allows for simultaneous processing multiple sensations.

29
Q

What is the corticofugal signal?

A

Transmits back from cortex to thalamus, medulla or SC.

Typically inhibitory and suppresses sensory input.

30
Q

Pain vs nociception

A

Pain: both the sensory and emotional unpleasantness from a harm.
Nociception: Neural process of encoding noxious stimuli.

31
Q

Fast pain is done by:

A

A-delta fibers

32
Q

Slow pain is done by:

A

C-fibers

33
Q

3 types of pain

A

Thermal
Mechanical
Chemical

34
Q

Silent nociception

A

Nociceptors that are not generally activated

35
Q

Phenotype switching

A

Induction of nociceptive receptors where they otherwise are not.

36
Q

Free nerve endings have which kind of fibers? (2)

A

C fibers

A-delta fibers

37
Q

Peptidergic free nerve endings
Peptides expressed:
Responsive to:
What kind of pain?

A

Peptides expressed: SP, CGRP.
Responsive to: NGF (nerve growth factor)
What kind of pain? Chronic inflammation and visceral pain.

38
Q

Non-peptidergic free nerve endings
Peptides expressed:
Responsive to:
What kind of pain?

A

Peptides expressed: no neuropeptides
Responsive to: GDNF
What kind of pain? Diabetic neuropathy

39
Q

TRP receptors are permeable to? (3)

A

Ca++
Na+
K+

40
Q

TRPV1

A

Capsaicin, and heat

41
Q

TRPA1

A

Menthol

42
Q

TRPM8

A

Allyl isothiocyanate and coldness.

43
Q

Other receptors sensing pain (3)

A

Na 1.7 channel: Mechanosensitive sodium channel.
P2X: ATP activated.
ASIC: activated by H+.

44
Q

Gate theory of pain

A

Rubbing the spot that hurts.
No pain is sensed because the inhibitory interneuron is blocking the nociceptive signal (activates the A-beta fiber which activates an interneuron which is inhibitory).

45
Q

Descending inhibition

A

NE and serotonin activates inhibitory interneurons which release opiods on presynaptic C-fibers which leads to reduced nociception/ALS.

46
Q

What mediates chronic pain, or subthreshold pain?

A

Bradykinin

47
Q

Role of insular cortex

A

Interpretation of pain.

Integrates all signals referred to pain.

48
Q

Asymbolia

A

No emotional attachment to pain

49
Q

Where does visceral input travel?

A

With ANS to hypothalamus and medulla.

50
Q
Types of pain associated with:
Skin:
Joints:
Muscle:
Viscera:
A

Skin: thermal and chemical
Joints: mechanical and chemical
Muscle: mechanical and chemical
Viscera: mechanical and chemical

51
Q

How does referred pain occur?

A

Many afferents converge in the dorsal horn. If they synapse on the same 2nd neurons, then the pain is perceived in many places.