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Physiology Flashcards

(103 cards)

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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
describe A delta fibres
small diameter thin myelination moderate conduction receptor for pain and temperature
26
describe C fibres
smallest diameter no myelination slow conduction receptor for pain, temperature and itch
27
what is a receptive field
target territory from which a sensory unit can be excited
28
what is sensory acuity
fineness of discrimination
29
sensory acuity is proportional or inversely proportional to receptive field
inversely proportional
30
what do Meissners and Merkels endings sense
vibration | merkels disc has same distribution as meissners but also on hairy skin
31
what do Ruffini endings and pacinian corpuscles sense
pressure ruffini is in joint capsules and dermis pacinian is in fascia and dermis
32
in the spinal cord, what is within grey matter
cell bodies and sensory afferent terminals
33
in the spinal cord what is within white matter
fibre tracts
34
the grey matter in the spinal cord is divided into dorsal and ventral horns with how many laminae of Rexed
10
35
nociceptors are __ fibre class and terminate at __ laminae
A delta and C | I and II laminae
36
low threshold mechanoreceptors are __ fibre class and terminate at __ laminae
A beta | III and IV
37
proprioceptors are __ fibre class and terminate at __ laminae
A alpha | VII to IX
38
what are the 2 tracts that convey sensory information back to the brain
dorsal column medial lemniscus | spinothalamic tract
39
what tract conveys fine touch and proprioception to the brain
DCML
40
what tract conveys pain, itch and thermosensation to the brain
spinothalamic
41
outline what the 1st, 2nd and 3rd order neuron do in the DCML
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
42
outline what the 1st, 2nd and 3rd order neuron do in the spinothalamic tract
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
where is the primary somatosensory cortex located
post central gyrus in the parietal lobe
44
what is the clinical relevance of spinothalamic fibres crossing but DCML not crossing
in spinal injury Brown-Sequard can develop where both tracts are affected from opposite sides
45
what are the 2 areas of the DCML tract and where do they supply
``` fasciculus cuneatus (more laterally) - above T6 fasciculus gracilis (medially) - T6 and below ```
46
what is lateral inhibition
when one neuron is active, it inhibits the activity of its neighbours via inhibitory neurons to strengthen the stimulus perception
47
in the trigeminal system what does the chief sensory nucleus sense
general tactile stimuli
48
in the trigeminal system, what does the spinal nucleus sense
pain and temperature
49
describe the 2nd order neuron in the trigeminal system
once in chief or sensory nucleus, the fibres decussate and project via trigeminal lemniscus to ventroposteriomedial nucleus of the thalamus
50
what is Brodmanns area
where the somatosensory system is located, receive input from the VP nucleus divided into 1, 2, 3a and 3b
51
outline what sensory information goes to which area of Brodmanns areas
3a - proprioceptors 3b - cutaneous slow and fast receptors 1 - cutaneous fast mechanoreceptors 2 - joint afferents
52
what is the function of the posterior parietal cortex
receives and integrates information from somatosensory cortex and other areas to decifer the deeper meaning of it damage can cause bizarre neurological disorders
53
what are the 2 components of the somatic motor system
skeletal muscles and the elements of the nervous system that control them
54
what are the 2 types of motor neuron in the body
upper motor neuron and lower motor neuron
55
where are UMNs and LMNs found
UMNs - within the brain | LMNs - soma of the brainstem or ventral horn of the spinal cord
56
what is the function of UMNs and LMNs
UMNs supply input to LMNs | LMNs modulate their activity and command muscle contraction
57
what is the function of alpha motor neurons
LMN that innervates the bulk of fibres within a muscle
58
what is the function of gamma motor neurons
LMN that innervates a sensory organ within a muscle called spindle fibre
59
what is the function of axial muscles
control posture, muscles around the trunk
60
what is the function of proximal muscles
control locomotion, muscles around the pelvic girdle
61
what is the function of distal muscles
control fine movement of the hands
62
axons of the LMNs exit the spinal cord though what structures
ventral rootlets then ventral root - form a spinal nerve with sensory fibres
63
why is there a greater distribution of motor neurons in the cervical and lumbar enlargements of the spinal cord
more motor neurons are required to innervate the distal and proximal musculature
64
what is a motor unit
functional unit of motor system | an alpha MN and all the skeletal muscle fibres it innervates
65
what is a motor pool
an alpha motor neuron and all the fibres required to innervate a single muscle
66
what 2 mechanisms are the force of muscle contraction graded by
frequency of action potential discharge of alpha MN | the recruitment of additional synergistic motor units
67
the LMNs innervating axial muscles in the ventral horn are more medial/lateral compared to LMNs innervating distal muscles
more medial
68
the LMNs innervating flexors are more dorsal/ventral in the ventral horn compared to LMNs innervating extensors
dorsal
69
what muscle in the body has very few muscle fibres per LMN
extra-ocular muscles | very fine movements
70
what muscle in the body has hundreds of muscle fibres per LMN
quadriceps muscles | anti-gravity requirements
71
what are the 3 types of muscle fibres and describe the difference between them
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
outline the order of recruitment of LMNs during an activity
recruited in order of the physical task, the slow type is always activated before the fast type etc as the exercise builds
73
what is the myotatic reflex
when skeletal muscle is pulled, it is pulled backwards to regulate the length of the muscle preventing damage
74
what organ senses the change in length of muscle during the myotatic reflex
muscle spindle
75
what is the function of the muscle spindle
proprioceptors of intrafusal muscle fibres that sense a change in muscle length and stretch to help the change
76
state 4 things that are present in spindle fibres
fibrous capsule intrafusal muscle fibres sensory afferents gamma motor neuron efferents
77
state the deep tendon reflexes and the nerves they test
``` biceps C5-6 supinator C5-6 triceps C7 quads L3-4 gastrocnemius S1 ```
78
where are golgi tendons located
between muscle and tendons
79
what is the function of golgi tendons
regulate muscle tension and protect muscles from overload
80
what is reciprocal inhibition
when an extensor eg quad contracts in the knee jerk the hamstring relaxes to prevent damage
81
where do descending spinal tracts arise from
cerebral cortex or brainstem
82
what are the two divisions of the descending pathway and explain the difference between them
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
the lateral pathway is divided into which 2 tracts
corticospinal/pyramidal tract | rubrospinal tract
84
outline the course of the corticospinal tract
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
what does the corticospinal tract control
distal musculature particularly flexors
86
where do cell bodies of the rubrospinal tract originate
red nucleus
87
where do fibres decussate in the rubrospinal tract
ventral tegmental decussation | rubrospinal tract descends ventrolaterally to the corticospinal tract
88
what is the function of the rubrospinal tract
exerts control over limb flexor muscles
89
how would a lesion of the lateral pathway present
loss of fractionated movements, joints cannot move independently slowing and impairment of accuracy of movements
90
what is the function of the vestibulospinal tract
hold body upright and maintain posture | controls extensor MNs
91
do fibres of the vestibulospinal tract decussate
no
92
where does the tectospinal tract begin
superior colliculus, receives input from the retina and visual cortex
93
where do the fibres of the tectospinal tract decussate
dorsal tegmental decussation at the midbrain
94
what is the function of the tectospinal tract
controls muscles of the neck, upper trunk and shoulders based on eye movements
95
what is reticular formation
diffuse mesh of neurons that are located along the length and core of the brainstem
96
where does the reticulospinal tract originate from
reticular formation
97
describe the difference between the pontine/medial reticulospinal tract and the medullary/lateral reticulospinal tract
pontine/medial - contracts flexors of lower limb | medullary/lateral - opposes the action of medial tract
98
innocuous signals are transmitted by which fibres
A beta fibres
99
nociceptive signals are transmitted by which fibres
C and A delta fibres
100
what are the three types of pain signals
nociceptive inflammatory pathological
101
what are the two types of nociceptors in the body
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
what is the gate control theory
the gate either blocks pain signals or allows them through depending on the stronger signal that is felt
103
if A beta fibres firing exceeds C and A gamma fibres is nociception perceived
no as more innocuous signals are being perceived than nociceptive signals

Neurology (19 decks)

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