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Year 3 Revision > Neurophysiology > Flashcards

Neurophysiology Flashcards

1
Q

Give an example of a unipolar cell

A

Peripheral autonomic neurone

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2
Q

Give an example of a bipolar neurone

A

Retinal

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3
Q

Where are passive signals found in the neurone?

A

In the dendrites and body (NOT the axon)

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4
Q

Describe spatial summation

A

Lot of inputs into neurone

Signals converge to determine output

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5
Q

Describe temporal summation

A

Single input

Modulates output by variation in action potential FREQUENCY

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6
Q

Give an example of an ionotropic and metabotropic receptor.

A

Ionotropic - nicotinic receptor

Metabotropic - muscarinic receptor

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7
Q

What are the main 2 differences between non-NMDA and NMDA receptors

A

NMDA is slow and transmits calcium as well as potassium and sodium.

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8
Q

Are NMDA and non-NMDA receptors ionotropic or metabotropic?

A

Both ionotropic

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9
Q

Where are the cell bodies of second order neurones in the somatosensory system?

A

Dorsal horn of spinal cord
OR
CN nuclei

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10
Q

Where are the cell bodies of third order neurones in the somatosensory system?

A

Thalamus

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11
Q

What is another name for high threshold units?

A

Nociceptors

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12
Q

Describe slow adapting neurones and give an example

A

Continously fire while stimulus detected

Stretch receptors

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13
Q

Describe fast adapting neurones and give an example

A

Detects change in stimulus strength
Number of impulses proportional to rate of change
E.g. muscle spindle, hair follicle afferents

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14
Q

Describe very fast adapting neurones and give an example

A

Responds only to V fast movement such as rapid vibration

Pacinian corpuscle

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15
Q

Give an example of Aalpha fibres

A

Proprioceptors

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16
Q

Give an example of Abeta fibres

A

Mechanoreceptors in skin

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17
Q

Give examples of Adelta fibres

A

Pain

Temp

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18
Q

Give examples of C fibres

A

Temp
Pain
Itch

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19
Q

What is a type 1 and type 2 receptive field?

A

Type 1 - small receptive field

Type 2 - large receptive field

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20
Q

What are the laminae of Rexed?

A

10 areas of the grey matter of the spinal cord

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21
Q

What laminae of Rexed do nociceptors go to?

A

I and II

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22
Q

What laminae of Rexed do low threshold mechanoreceptors (Abeta) fibres go to?

A

III to VI

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23
Q

What laminae of Rexed do proprioceptors go to?

A

VII to IX

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24
Q

Which of the fasciculus gracilis and fasciculus cuneatus are lateral and medial?

A

Medial - fasciculus gracilis

Lateral - fasciculus cuneatus

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25
Q

From lateral to medial, what spinal levels are the white matter in the dorsal columns of the spinal cord?

A

Cervical -> sacral

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26
Q

Where in the thalamus do the neurones from the dorsal columns synapse?

A

The ventral posterior lateral (VPL) nucleus of the thalamus

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27
Q

What is stereognosis?

A

Ability to recognise an object by feeling it.

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28
Q

What is contrast enhancement?

A

As info goes up the sensory pathway, the differences in activity of adjacent neurones are amplified e.g. through lateral inhibition.

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29
Q

Describe lateral inhibition.

A

When one neurone is activated, it inhibits the activity of its neighbours via inhibitory interneurones.

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30
Q

Where in the thalamus do neurones from the trigeminal system go to?

A

Ventroposteriomedial (VPM) nucleus

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31
Q

What Brodmann areas make up the somatosensory cortex?

A

1, 2, 3a and 3b

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32
Q

What layer of the somatosensory cortex receives inputs from the thalamus and is this superficial or deep?

A

Layer IV

Deep (goes from I-VI with I being the most superficial)

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33
Q

What is the function of the posterior parietal cortex?

A

Deciphers deeper meaning of the info from the somatosensory cortex.

34
Q

Where in the spinal cord are more LMNs found?

A

The cervical and lumbar enlargements.

35
Q

What 3 inputs can there be to an alpha motor neurone?

A

DRG cells innervating muscle spindle
UMNs
Spinal interneurones

36
Q

Describe the alpha motor neurones innervating fast type muscle in comparison to slow type.

A

Fast type - larger with faster conducting axons.

37
Q

Describe type I, IIa and IIb/x muscle fibres.

A

I - ATP from oxidative phosphorylation, red (high myoglobin), slow contraction, fatigue resistant
IIa - ATP from oxidative phosphorylation, red, fast contraction, fatigue resistant
IIb/x - ATP from glycolysis, white, fast contraction, not fatigue resistant

38
Q

Are smaller or larger alpha-motor neurones activated more easily?

A

Smaller

39
Q

In what order are muscle fibres activated with increasing tension?

A

Type I -> type IIa -> type IIx

40
Q

What is the myotatic reflex?

A

When a skeletal muscle is pulled, it pulls back (stretch reflex)

41
Q

What do muscle spindles consist of?

A

Fibrous capsule
Intrafusal muscle fibres
Sensory afferents (myelinated fast conduction)
Gamme motor neurone

42
Q

How many synapses are involved in the myotatic (stretch) reflex?

A

One (monosynaptic)

43
Q

In what muscles is the myotatic reflex most prominent in?

A

Extensors

44
Q

What part of intrafusal fibres are contractile?

A

The polar ends.

45
Q

What are the 3 types of muscle spindle fibres, what type of afferent and efferent fibres innervate them and what are they sensitive to?

A

Nuclear bag 1 fibres - Ia afferents, dynamic gamma motor neurones, rate of change of muscle length.
Nuclear bag 2 and chain fibres, Ia and II afferents, static gamma motor neurones, absolute muscle length.

46
Q

What are the 2 types of afferent fibres of the muscle spindle and what do they do?

A

Ia - wrap around centre of all intrafusal fibres, sense rate of change.
II - wrap around bag 2 and chain fibres, more sensitive to absolute length.

47
Q

When are static gamma MNs active and when are dynamic ones active?

A

Static - when muscle length changes slowly and predictably.

Dynamic - when muscle length changes rapidly and unpredictably.

48
Q

What type of sensory afferent innervates golgi tendon organs?

A

Ib

49
Q

What reflex involves golgi tendon organs?

A

The reverse myotatic reflex.

50
Q

Describe the reverse myotatic reflex.

A

Golgi organ stimulated -> Ib afferent stimulated -> inhibitory interneurone in spinal cord -> alpha motor neurone inhibited.

51
Q

How do interneurones affect the myotatic reflex?

A

The afferent neurone from the spindle will synapse both with the alpha motor neurone of the extensor and an inhibitory interneurone.
This interneurone will then inhibit the alpha motor neurone of the flexor muscle.

52
Q

Why is the myotatic reflex of a flexor not activated when an extensor contracts?

A

Descending control from the motor cortex to inhibitory interneurones inhibits the alpha motor neurones of antagonistic muscle

53
Q

Describe the flexor and crossed extensor reflex.

A 
Noxious stimuli causes activation of neurones causing ipsilateral limb to flex.
Also causes (through excitatory interneurones) the contralateral limb to extend.

Enhances postural support.

54
Q

What controls the lateral and ventromedial descending spinal tracts?

A

Lateral - cerebral cortex

Ventromedial - brainstem

55
Q

Where does the rubrospinal tract start and what is it’s main function?

A

The red nucleus in the midbrain

Limb flexion

56
Q

What is the function of the lateral vestibulospinal tract?

A

Extension of antigravity muscles

57
Q

What is the function of the medial vestibulospinal tract?

A

Activate cervical spinal circuits that control neck and back muscles guiding head movements.

58
Q

Where does the tectospinal tract start and what is its function?

A

The superior colliculus of the midbrain (optic tectum)

Influences muscles of neck, upper trunk and shoulders to orientate head and eyes to new visual stimuli

59
Q

What is the function of the pontine (medial) reticulospinal tract?

A

Maintains posture by contracting extensor muscles of lower limbs

60
Q

What is the function of the medullary (lateral) resticulospinal tract?

A

Opposes medial tract action

Releases antigravity muscles from reflex control

61
Q

What is the pathway for signal transmission in the retina?

A

Photoreceptors -> bipolar cells -> ganglion cells

62
Q

What are the cells that connect laterally in the retina?

A

Horizontal cells

Amacrine cells

63
Q

What do horizontal cells receive input from?

A

Photoreceptors

64
Q

What do amacrine cells receive input from?

A

Bipolar cells

65
Q

Do photoreceptors depolarise or hyperpolarise when light is shone on them?

A

Hyperpolarise

66
Q

What does retinal in rhodopsin convert from and into when it absorbs light?

A

From 11-cis-retinal to all-trans-retinal

67
Q

What does convergence mean in the retina?

A

How many photoreceptors transmit to one ganglion cell.

E.g. high convergence in rods as lots of rods converge on one ganglion cell

68
Q

Which of the OFF or ON pathway has ionotropic or metabotropic glutamate receptors in the ganglion cells?

A

OFF - ionotropic

ON - metabotropic

69
Q

What is the function of amacrine cells?

A

Lateral inhibition

70
Q

What is the function of horizontal cells?

A

Lateral inhibition

Releases GABA when excited allowing centre-surround organisation to work.

71
Q

Which of A-delta and C fibres are polymodal?

A

C-fibres

72
Q

What is the family name for thermoreceptors?

A

Transient receptor potential (TRP)

73
Q

Which thermoreceptor is greatly sensitised in inflammation to become active at body temperature?

A

TRPV1

74
Q

Give some examples of chemical stimuli for nociceptors and what receptors are activated by them.

A

H+ - acid sensing ion channels (ASICs)
ATP - P2X and P2Y
Bradykinin - B2 receptors

75
Q

What type of nociceptors have both afferent and efferent function?

A

Peptidergic polymodal nociceptors (subset of C fibres)

76
Q

What is released by the nociceptors which contributes to neurogenic inflammation?

A

Pro-inflammatory mediators (calcitonin, CGRP, substance P)

77
Q

What is the long term effect of noxious stimulation on the spine?

A

Increases spinal excitability

Contributes to hyperalgesia and allodynia

78
Q

What types of neurone receive signals from nociceptors and proprioceptors?

A

Wide dynamic range neurones

79
Q

What is viscerosomatic pain?

A

Sharp well localised pain when inflammatory exudate from a diseased organ contacts a body wall structure e.g. appendicitis.

80
Q

Describe the gate control theory in terms of nociceptors and proprioceptors.

A

When proprioceptors are more active than nociceptors, pain is less perceived and vice versa.

81
Q

What tract largely transmits slow C-fibre pain and what is its function?

A

Spinoreticular tract

Autonomic and emotional response to pain

Year 3 Revision (70 decks)

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