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Neurology > Physiology > Flashcards

Physiology Flashcards

1
Q

what is the function of the axon hillock in a neuron

A

site of action potentials

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2
Q

what is the function of a dendrite in a neuron

A

receives input from other regions and conveys electrical signals to soma

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3
Q

what is the function of an axon

A

conducts output signals as action potentials to presynaptic terminals

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4
Q

what are the 4 types of neuron present

A

unipolar
bipolar
multipolar
pseudounipolar

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5
Q

what is resting membrane potential value

A

-70

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6
Q

conductance in myelinated/non-myelinated neurons is faster

A

myelinated neurons is faster

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7
Q

action potentials jump between what structures

A

nodes of ranvier

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8
Q

outline the steps in synaptic transmission

A

uptake of precursor - synthesis of transmitter - depolarisation by action potentials - Ca influx - Ca induced release of neurotransmitter - receptor activation - enzyme mediated inactivation of transmitter - reuptake of transmitter

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9
Q

what is the main excitatory neurotransmitter in the CNS

A

glutamine

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10
Q

what is the action of glutamine in the CNS

A

activated post synaptic, cation selective inotropic glutamine receptors causing graded excitatory depolarising response, Na moves in to get more positive

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11
Q

what is the main inhibitory neurotransmitter in the CNS

A

GABA or glycine

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12
Q

what is the action of GABA in the CNS

A

generates a local inhibitory, hyperpolarising response, Cl moves into the cell and it becomes more -ve

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13
Q

fast excitatory post synaptic potentials is due to activation of nicotinic ACh or muscarinic G protein

A

nicotinic ACh

muscarinic G protein produces a slow excitatory response

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14
Q

what are the 5 different receptors for different sensory modalities in the body

A 
fine touch - pressure, vibration 
proprioception
pain - nociception 
itch - pruriception 
temperature
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15
Q

what is proprioception

A

body’s awareness of its own space, controlled by posture and movement

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16
Q

describe a first order neuron

A

within PNS
primary sensory afferent
usually in dorsal root ganglia

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17
Q

describe a second order neuron

A

within CNS

located in dorsal horn of spinal cord or brainstem nuclei

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18
Q

describe a third order neuron

A

within CNS

in thalamic nuclei

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19
Q

outline the receptors/sensory unit that pick up each sensory modality

A

skin mechanoreceptors - touch and pressure
joint/muscle mechanoreceptors - proprioception
thermoreceptors - temperature
nociceptors - pain
itch receptors - itch

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20
Q

what is the threshold a stimulus must reach

A

the intensity required to excite a sensory unit
low threshold for fine touch
high threshold for pain and high temperature

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21
Q

primary sensory afferent fibres differ in axon diameter, extent of myelination, conduction velocity and associated sensory receptor, state which one is group I-IV

A

I - A alpha
II - A beta
III - A delta
IV - C

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22
Q

outline the order of sensory fibres from bigger diameter to smallest diameter

A

I, II, III, IV

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23
Q

describe A alpha fibres

A

biggest diameter
thick myelination
very fast conduction
receptor for proprioception of muscles

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24
Q

describe A beta fibres

A

moderate diameter
moderate myelination
fast conduction
receptor for mechanoreceptors of skin

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25
Q

describe A delta fibres

A

small diameter
thin myelination
moderate conduction
receptor for pain and temperature

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26
Q

describe C fibres

A

smallest diameter
no myelination
slow conduction
receptor for pain, temperature and itch

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27
Q

what is a receptive field

A

target territory from which a sensory unit can be excited

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28
Q

what is sensory acuity

A

fineness of discrimination

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29
Q

sensory acuity is proportional or inversely proportional to receptive field

A

inversely proportional

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30
Q

what do Meissners and Merkels endings sense

A

vibration

merkels disc has same distribution as meissners but also on hairy skin

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31
Q

what do Ruffini endings and pacinian corpuscles sense

A

pressure
ruffini is in joint capsules and dermis
pacinian is in fascia and dermis

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32
Q

in the spinal cord, what is within grey matter

A

cell bodies and sensory afferent terminals

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33
Q

in the spinal cord what is within white matter

A

fibre tracts

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34
Q

the grey matter in the spinal cord is divided into dorsal and ventral horns with how many laminae of Rexed

A

10

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35
Q

nociceptors are __ fibre class and terminate at __ laminae

A

A delta and C

I and II laminae

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36
Q

low threshold mechanoreceptors are __ fibre class and terminate at __ laminae

A

A beta

III and IV

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37
Q

proprioceptors are __ fibre class and terminate at __ laminae

A

A alpha

VII to IX

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38
Q

what are the 2 tracts that convey sensory information back to the brain

A

dorsal column medial lemniscus

spinothalamic tract

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39
Q

what tract conveys fine touch and proprioception to the brain

A

DCML

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40
Q

what tract conveys pain, itch and thermosensation to the brain

A

spinothalamic

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41
Q

outline what the 1st, 2nd and 3rd order neuron do in the DCML

A

1st - fibres from feeling of touch to the dorsal horn of spinal cord
2nd - decussation in the medulla to the thalamus
3rd - thalamus to the primary somatosensory cortex in post central gyrus

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42
Q

outline what the 1st, 2nd and 3rd order neuron do in the spinothalamic tract

A

1st - immediately decussate at the level of the spinal cord
2nd - travel up contralateral side to the medulla
3rd - synapse in thalamus and travel to post central gyrus

43
Q

where is the primary somatosensory cortex located

A

post central gyrus in the parietal lobe

44
Q

what is the clinical relevance of spinothalamic fibres crossing but DCML not crossing

A

in spinal injury Brown-Sequard can develop where both tracts are affected from opposite sides

45
Q

what are the 2 areas of the DCML tract and where do they supply

A 
fasciculus cuneatus (more laterally) - above T6 
fasciculus gracilis (medially) - T6 and below
46
Q

what is lateral inhibition

A

when one neuron is active, it inhibits the activity of its neighbours via inhibitory neurons to strengthen the stimulus perception

47
Q

in the trigeminal system what does the chief sensory nucleus sense

A

general tactile stimuli

48
Q

in the trigeminal system, what does the spinal nucleus sense

A

pain and temperature

49
Q

describe the 2nd order neuron in the trigeminal system

A

once in chief or sensory nucleus, the fibres decussate and project via trigeminal lemniscus to ventroposteriomedial nucleus of the thalamus

50
Q

what is Brodmanns area

A

where the somatosensory system is located, receive input from the VP nucleus
divided into 1, 2, 3a and 3b

51
Q

outline what sensory information goes to which area of Brodmanns areas

A

3a - proprioceptors
3b - cutaneous slow and fast receptors
1 - cutaneous fast mechanoreceptors
2 - joint afferents

52
Q

what is the function of the posterior parietal cortex

A

receives and integrates information from somatosensory cortex and other areas to decifer the deeper meaning of it
damage can cause bizarre neurological disorders

53
Q

what are the 2 components of the somatic motor system

A

skeletal muscles and the elements of the nervous system that control them

54
Q

what are the 2 types of motor neuron in the body

A

upper motor neuron and lower motor neuron

55
Q

where are UMNs and LMNs found

A

UMNs - within the brain

LMNs - soma of the brainstem or ventral horn of the spinal cord

56
Q

what is the function of UMNs and LMNs

A

UMNs supply input to LMNs

LMNs modulate their activity and command muscle contraction

57
Q

what is the function of alpha motor neurons

A

LMN that innervates the bulk of fibres within a muscle

58
Q

what is the function of gamma motor neurons

A

LMN that innervates a sensory organ within a muscle called spindle fibre

59
Q

what is the function of axial muscles

A

control posture, muscles around the trunk

60
Q

what is the function of proximal muscles

A

control locomotion, muscles around the pelvic girdle

61
Q

what is the function of distal muscles

A

control fine movement of the hands

62
Q

axons of the LMNs exit the spinal cord though what structures

A

ventral rootlets then ventral root - form a spinal nerve with sensory fibres

63
Q

why is there a greater distribution of motor neurons in the cervical and lumbar enlargements of the spinal cord

A

more motor neurons are required to innervate the distal and proximal musculature

64
Q

what is a motor unit

A

functional unit of motor system

an alpha MN and all the skeletal muscle fibres it innervates

65
Q

what is a motor pool

A

an alpha motor neuron and all the fibres required to innervate a single muscle

66
Q

what 2 mechanisms are the force of muscle contraction graded by

A

frequency of action potential discharge of alpha MN

the recruitment of additional synergistic motor units

67
Q

the LMNs innervating axial muscles in the ventral horn are more medial/lateral compared to LMNs innervating distal muscles

A

more medial

68
Q

the LMNs innervating flexors are more dorsal/ventral in the ventral horn compared to LMNs innervating extensors

A

dorsal

69
Q

what muscle in the body has very few muscle fibres per LMN

A

extra-ocular muscles

very fine movements

70
Q

what muscle in the body has hundreds of muscle fibres per LMN

A

quadriceps muscles

anti-gravity requirements

71
Q

what are the 3 types of muscle fibres and describe the difference between them

A

slow (type I) - slow contraction and relaxation, fatigue resistant, ATP from phosphorylation, red meat due to myoglobin levels
fast (type IIa) - fast contraction and fatigue resistant, ATP from phosphorylation, red meat
fast (type IIb) - fast contraction but can fatigue, ATP from glycolysis, white meat - not found in humans

72
Q

outline the order of recruitment of LMNs during an activity

A

recruited in order of the physical task, the slow type is always activated before the fast type etc as the exercise builds

73
Q

what is the myotatic reflex

A

when skeletal muscle is pulled, it is pulled backwards to regulate the length of the muscle preventing damage

74
Q

what organ senses the change in length of muscle during the myotatic reflex

A

muscle spindle

75
Q

what is the function of the muscle spindle

A

proprioceptors of intrafusal muscle fibres that sense a change in muscle length and stretch to help the change

76
Q

state 4 things that are present in spindle fibres

A

fibrous capsule
intrafusal muscle fibres
sensory afferents
gamma motor neuron efferents

77
Q

state the deep tendon reflexes and the nerves they test

A 
biceps C5-6
supinator C5-6
triceps C7
quads L3-4
gastrocnemius S1
78
Q

where are golgi tendons located

A

between muscle and tendons

79
Q

what is the function of golgi tendons

A

regulate muscle tension and protect muscles from overload

80
Q

what is reciprocal inhibition

A

when an extensor eg quad contracts in the knee jerk the hamstring relaxes to prevent damage

81
Q

where do descending spinal tracts arise from

A

cerebral cortex or brainstem

82
Q

what are the two divisions of the descending pathway and explain the difference between them

A

lateral pathway - control from cerebral cortex, controls distal musculature such as skilled hand movements
ventromedial pathway - control from brainstem, function is controlling posture and locomotion

83
Q

the lateral pathway is divided into which 2 tracts

A

corticospinal/pyramidal tract

rubrospinal tract

84
Q

outline the course of the corticospinal tract

A

axons course to the base of the medulla, most of the fibres cross at the pyramidal decussation (lateral corticospinal tract) and the rest decussate more caudally, known as the ventral corticospinal tract

85
Q

what does the corticospinal tract control

A

distal musculature particularly flexors

86
Q

where do cell bodies of the rubrospinal tract originate

A

red nucleus

87
Q

where do fibres decussate in the rubrospinal tract

A

ventral tegmental decussation

rubrospinal tract descends ventrolaterally to the corticospinal tract

88
Q

what is the function of the rubrospinal tract

A

exerts control over limb flexor muscles

89
Q

how would a lesion of the lateral pathway present

A

loss of fractionated movements, joints cannot move independently
slowing and impairment of accuracy of movements

90
Q

what is the function of the vestibulospinal tract

A

hold body upright and maintain posture

controls extensor MNs

91
Q

do fibres of the vestibulospinal tract decussate

A

no

92
Q

where does the tectospinal tract begin

A

superior colliculus, receives input from the retina and visual cortex

93
Q

where do the fibres of the tectospinal tract decussate

A

dorsal tegmental decussation at the midbrain

94
Q

what is the function of the tectospinal tract

A

controls muscles of the neck, upper trunk and shoulders based on eye movements

95
Q

what is reticular formation

A

diffuse mesh of neurons that are located along the length and core of the brainstem

96
Q

where does the reticulospinal tract originate from

A

reticular formation

97
Q

describe the difference between the pontine/medial reticulospinal tract and the medullary/lateral reticulospinal tract

A

pontine/medial - contracts flexors of lower limb

medullary/lateral - opposes the action of medial tract

98
Q

innocuous signals are transmitted by which fibres

A

A beta fibres

99
Q

nociceptive signals are transmitted by which fibres

A

C and A delta fibres

100
Q

what are the three types of pain signals

A

nociceptive
inflammatory
pathological

101
Q

what are the two types of nociceptors in the body

A

A gamma fibres - mechanical and thermal only, mediate first fast pain
C fibres - all types of noxious stimuli, mediate second or slow pain such as throbbing or cramping

102
Q

what is the gate control theory

A

the gate either blocks pain signals or allows them through depending on the stronger signal that is felt

103
Q

if A beta fibres firing exceeds C and A gamma fibres is nociception perceived

A

no as more innocuous signals are being perceived than nociceptive signals

Neurology (19 decks)

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