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Neurology > Physiology > Flashcards

Physiology Flashcards

1
Q 
Function of dendrites
Soma (perikaryon)
Axon hillock and initial segment 
Axon 
Synapse
A

Received input from other neurones and conveys graded electrical signals passively to the soma

Integrated incoming signal that are then conducted passively to the axon hillock

site of initiation of the all or none AP

Conducts output signal as action potentials to other neurones. between soma and presynaptic terminal (anterograde direction) vice versa is retrograde direction

Point of chemical communication between neurones or other cells

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2
Q

What do viruses take advantage of in axons

A

retrograde direction is used to infect neurones - herpes, polio, rabies

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3
Q

Give examples of unipolar neurones
pseudo unipolar neurone
bipolar
multipolar

A

peripheral autonomic neurone
dorsal root ganglion
retinal bipolar neurone
LMN

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4
Q

Input
Integrative
Conductive
Output

A

dendrites
soma
axon
leading to secretion of neurotransmitter

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5
Q

Golgi type 1

Type 2

A

long axon

short axon

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6
Q

how does an action potential work

A

sodium channels open for sodium influx for the upstroke

potassium channels open up for a potassium outflow for the downstroke

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7
Q

normal resting membrane potential
threshold
peak
undershoot

A

-70mV

-60mV
+40mV
-80mV

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8
Q

Why does an undershoot take place in AP

A

Some potassium channels remain open for a small period of time

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9
Q

What is the problem with passive conduction

A

leaky membrane - passive signals do not spread far from their site of origin due to current loss across the membrane

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10
Q

How can passive conduction be improved

A

decreasing axial resistance of the axoplasm by increasing axon dm
increasing membrane resistance by adding an insulating material

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11
Q

How does an AP move forward

A

at the peak of the AP outside is negative and the inside is positive - cyclic current which generates an AP -> AP moves forward

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12
Q

The difference between larger dm axon and smaller dm axon

A

larger has low resistance so more APs can be produced and vice versa

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13
Q

What are the insulating materials in CNS

PNS

A

Oligodendrocytes - one surrounds many axons

Schwann cells - many surround one axon

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14
Q

What is saltatory conduction

A

AP jump from one nice of ranvier to the next rather than flowing constantly

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15
Q

Give three types of synapses in order of frequency

A

axodendritic - very common
axosomatic - common
axoaxonic - uncommon

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16
Q

Describe an excitatory synapse

A

glutamate activates postsynaptic cation selective inotropic glutamate receptors generating a local graded excitatory depolarising response - excitatory postsynaptic potential

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17
Q

describe an inhibitory synapse

A

GABA or glycine activates postsynaptic anion selective inotropic GABA or glycine receptors generating a local graded inhibitory hyperpolarizing - inhibitory postsynaptic potential

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18
Q

what are the three major amino acid neurotransmitters in the CNS

A

glutamate
GABA
glycine

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19
Q

What separates pre and post synaptic membranes

A

synaptic cleft

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20
Q

what stores NT within the presynaptic terminal

A

vesicles

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21
Q

difference between pre synaptic membrane and post

A

pre - active zones around which vesicles cluster

post- NT receptors

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22
Q

what holds the post and pre synaptic membranes together

A

a matrix of fibrous extracellular protein within the cleft

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23
Q

What are amino acids and amines released from

What are peptides released from

A

synaptic vesicles

secretary vesicles

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24
Q

Give examples of amino acids

A

Glutamate, GABA, glycine

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25
Q

gives examples of amines

A

Each, DA, NA, 5-HT

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26
Q

give examples of peptides

A

CCK, Enk, Neuropeptide Y, somatostatin, TRH, VIP

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27
Q

What ion channels fores glutamate, GABA, glycine, ACh and 5-HT activate

A

inotropic which mediate fast neurotransmission

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28
Q

what do all except glycine activate

A

metabrotropic G protein coupled receptors

mediate slow neurotransmission

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29
Q

exteroceptive sensations
proprioeceptive sensations
visceral sensations
deep sensations

A

from the surface of the body
concerning posture and movement
from the internal organs
from fascia, muscles and bone

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30
Q

the higher the amplitude of the stimulus and the longer the duration means what

A

more APs fired and more neurotransmitter released

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31
Q 
list the stimulus and physiological receptor for the following 
touch, pressure, vibration 
proprioception 
pain
itch
A

mechanical forces on skin. skin mechanoreceptors
mechanical forces on joins and muscles. joint and muscle mechanoreceptors
heat. thermoreceptors
strong mechanical force on skin, viscera, heat. mechanical, thermal and polydymas nociceptors
irritant. itch receptors

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32
Q

list the two types of low threshold units

A

low threshold mechanoreceptors - mediate touch, vibration, pressure
low threshold thermoreceptors - medical cold, cool, indifferent, warm, hot

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33
Q

list the 4 kinds of high threshold units (nociceptors)

A

high threshold mechanireceptors- high intensity mechanical stimuli
thermal nociceptors - extreme degrees of heat >45 or <10
chemical - substances in tissues
polymodal - respond to at least two of the above

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34
Q

Slowly adapting neurones
rapidly adapting
very rapidly adapting

A

carry on firing APs - stretch receptors
number of impulse proportional to rate of change of stimulus - some muscle spindles, hair follicle afferents
only 1 - vibration - responds to very fast movement

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35
Q

A alpha
A beta
A weird one
C

A

thick myelinated - proprioceptors of skeletal muscle
moderately myelinated - mechanoreceptors of skin
think - pain, temp
none - temp, pain, itch

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36
Q

what is receptive field

A

region that when stimulated with an adequate stimulus causes a response in that neurone

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37
Q

list what the skin is innervated with

A

free nerve endings
meissners corpuscles - esp where 2 point disc is, not in hair skin
merkels - same as meis, but only in hairy skin
hair end organs
krause end bulbs
pacinial corpuscles

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38
Q 
Meissners
merkel
pacinial 
ruffini
hair G - guard(long)
hair d - down (short)
c mechanoreceptor
A 
Ab - stroking, fluttering RA
Ab - pressure, texture SA
Ab - vibration , VRA
Ab - skin stretch - SA
Ab - stroking, fluttering
A weird one - light stroking 
C - stroking, social and erotic touch
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39
Q

What is grey matter divided into

A

dorsal and ventral horn and 10 laminae of rexed

40
Q

where are these afferent terminals in the dorsal horn
nociceptors A weird one/C
LTMs Ab
Proprioceptros Aa

A

laminae 1-2
laminae 3-6
laminae 6-9

41
Q

dorsal column first order neurone carries what

spinothalmic tract carries what

A

touch, pressure, vibration, conscious proprioception

pain, thermosensation, crude touch, itch, tickle

42
Q

what is the dorsal column divided into and then further divided into

A

medial fasciculus gracilis (lumbar and sacral)

lateral fasciculus cuneatus (cervical and thoracic)

43
Q

what are the capabilities of the dorsal column (5)

A 
stereogenesis 
fine touch
conscious proprioception 
vibration detection 
weight discrimination
44
Q

where is the somatosensory cortex located

A

in the post central gyrus of the parietal cortex immediately posterior to the central sulcus and adjacent to the posterior parietal cortex

45
Q

list the inputs for brodmans area 1
2
3a
3b

A

1-cutaneous mechanoreceptors, BA 3b [texture discrimination]joint afferents, golgi tendon organs, deep tissues, BA 3a and 3b [object perception]
2-joint afferents, golgi tendon organs, deep tissues, BA 3a and 3b [object perception]
3a-proprioreceptors [body position]
3b - cutaneous SA and RA, BA 3a [touch]

46
Q

list the layers from the surface to white matter of the somatosensory cortex

A 
molecular 
external granular 
external pyramidal 
internal granular 
internal pyramidal 
multiform 
-white matter -
47
Q

loss of a receptive field - finger is cut off (e.g. D3)

A

area formerly representing D3 will respond to stimulation of the adjacent digits - their cortical representation expands into what was D3

48
Q

Na channels open
Ca channels
Cl channels
K channels

A 
flows inwards (depolarization, excitatory)
flows inwards (depolarisation, excitatory)
flows inwards (hyperpolariazation, inhibitory)
flows outwards (hyper, inhibitory)
49
Q

where does the AP depolarise?
what channels does the depolarisation open?
entry of the substance then triggers what?
where does the NT diffuse and bind?
what does the binding do?

A

axon terminal
Ca channels
calcium entry triggers exocytosis
synaptic cleft and receptors on the post synaptic cell
initiates a response in the post synaptic cell

50
Q

what are the three ways of inactivating neurotransmitters

A

NT can be returned to axon terminals for reuse or transported into glial cells
enzymes inactivate them
Nt can diffuse out of the synaptic cleft

51
Q

what are the two modes of action by NT on ion channels

A

direct by inotropic receptors

indirect by activation of metabrotropic receptors

52
Q

what are the two major families of ligand gated channels and the difference between the two

A

GABA, glycine and Ash - pentamers

Glutamate receptors channels are tetramers

53
Q

what packages are NT released in and how can this affect the outcome of neurotransmission

A

quanta’s - varying quanta may be released

54
Q

difference between spatial summation and temporal

A

spatially distributed by times together

EPSPs occur in temporal sequence such that threshold is triggered

55
Q

nociceptive pain
inflammatory pain
pathological pain

A

acute pain
prolonged
neurogenic (IBS, fibromyalgia)

56
Q

what order neurones are nociceptors

A

first order neurones

57
Q

two fires in nociceptors

A

A delta - mechanical/thermal, thinly myelinated, mediate first or fast pain
C fibres - unmyelinated, polymodal, mediate second or slow pain

58
Q

describe the two types of A delta fibres

A

Type 1 - HTM - strong mechanical stimuli, activated by noxious heat >53, show sensitisation to prolonged stimuli, mediated first pain to mechanical stimuli
Type 2 - mechanical, heat 43-47, sensative to capsaicin. shows adaption. mediated first pain to heat

59
Q

describe the 4 types of C fibres

A

C-MH - mechanical stimuli and heat 39-51, capsaicin, shows sensitisation to repeated stimuli
C-M - mechanical just
C-H - heat, sensative to capsaicin
C-MiHi-normally insensitive to both but acquires sensitivity following sensitisation by inflammatory mediators. sensitive to capsaicin and other algesic or pro algesic substances

60
Q

difference between central terminal and peripheral in bidirectional nociceptors

A

central - not responsive to environmental stimuli. Ca dependant transmitter release. targeted by endogenous molecules that regulate activity

peripheral - responsive to environmental stimuli, site of release of molecules that influence local tissue environment. targeted by endogenous molecules that regulate sensitivity

61
Q

where do nociceptive A delta and C fibres terminate

A

superficially in lamina I and II and also V for A delta

62
Q

what cells receive input form only A beta fibres

A

proprioceptive

63
Q

peripheral sensitisation

central

A

mediated by nociceptors at site of injury
causes primary hyperalgesia
major role in heat and lesser of a role in mechanical sensitivity

reflects an increase in CNS neurones activity and properties
causes secondary hyperalgesia and allodynia
plays a major role in mechanical sensitivity

64
Q

physiological controlling of the gate

medical

A

open - C/a delta
closed - A beta fibres active

open - extent of injury, insufficient medication
closed - sufficient medication

65
Q

thermosensation at the skin

is it uniform over the body

A

no - hot and cold spots

66
Q

what kind of potential has been implicated in thermosensation

A

transient receptor potential (TRP)

67
Q

input of LMNs

A

UPMs

proprioceptors and internuroens

68
Q

what do LMNs compromise of

A

alpha MNs - innervate bulk of fibres within muscle that generate force
Gamma MNs - inneverate sensory organ within muscle known as a muscle spindle

69
Q

biceps brachii and brachialis work together how

what group of muscles are these antagonists to

A

synergists

triceps brachii and anconeus

70
Q

where do axons of the LMNs exit

A

spinal cord in ventral roots or via CNs

71
Q

where are the nerves that innervate distal and proximal musculature
and where are the ones that innervate the axial musculature

A

mainly in the cervical and lumbar sacral segments of the spinal cord

all levels

72
Q

what does alpha MN and all of the muscle fibres it innervates called

A

motor unit

73
Q

what is a collection of alpha MNs that all supply a single muscle called

A

motor neurone pool

74
Q

how is force of muscle contraction graded by alpha MNs

A

frequency of AP discharge of alpha MN

recruitment of additional, synergistic, motor units

75
Q

LMNs innervating axial muscles are what to those innervating distal muscle
LMNs innervating flexors are what to those supplying extensors

A

medial

dorsal

76
Q

sources of input to alpha MNs

A

central terminals of dorsal root ganglion cells whose axons innervate the muscle spindles
UMNs in the motor cortex and brain stem
spinal interneurones

77
Q

what does muscle strength depend on

A

firing of LMNs
number of LMNs that innverate the muscle
co ordination of the movement

fibre size
fibre phenotype

78
Q

what are small motor units innervated by

A

small alpha MNs and vice versa

79
Q

what if the force of contraction of each motor unit dependant on

A

the size

80
Q

where is the motor axon innervating a muscle fibre

A

at endplate (neuromuscular junction) which is usually at the centre of the fibre

81
Q

slow fibres

fast fibres

A

slow - aerobic, red, slow contraction, fatigue resistant
fast - type 2A fast contraction, aerobic, fatigue resistant
type 2B - anaerobic, fast contraction but not fatigue resistant, white

82
Q

the three types of motor units

A

slow - most numerous - lowest threshold
fatigue resistant
fast fatiguing - large and have a high threshold

83
Q

what is the myotonic reflex

A

when a skeletal muscle is pulled it pulls back

84
Q

how does a myotonic reflex occur

A

change in length and rate of change is registered by a sensory organ within the muscle - contributes to non conscious proprioception

85
Q

what do muscle spindles consist of

A

fibrous capture intramural muscle fibres
sensory afferents - innervate intrafusal fibres
gamma MNs - efferents - innervate intrafusal fibres

86
Q

stretch of muscle spindle - what happens next

A

activation of la afferent - activation alpha MN - contraction of muscle

87
Q 
supinator - wrist 
biceps 
triceps
quadriceps
ankle
A 
C5-C6
C5-C6
C7
L3-L4
S1
88
Q

what consists of intrafusal fibres

stimulation from what causes the spindle to contract

A

non contractile region - innervated by la
contractile - receive efferents from alpha MNs

gamma MNs

89
Q

what happens during voluntary movement in intrafusal fibres

A

alpha and gamma MNs co activated so intrafusal fibres contract in parallel with the extra fusal fibres

90
Q

where are golgi tendon organs
what do they monitor
what are they innervated by
how do they act to regulate muscle tension

A

junction of muscle and tendon
changes in muscle tension - in series with extrafusal fibres
lb
protect muscle from over load and regulate muscle tension to an optimal range

91
Q

where do lb enter and synapse under what and where and what do they lead to

A

spinal cord
synapse under inhibitory interneurone which then synapse on alpha MNs of the homonymous muscle forming the basis of the reverse myotonic reflex

92
Q

what is the polysynaptic pathway

A

in which an inhibitory internueone is interposed between the lb afferent and alpha MN

93
Q

where are proprioceptive axons
what do they respond to

free nerve endings
golgi type endings
paciniform
ruffini

A

CT of joints
angle, directions nd velocity of movement in a joint

HT SA, nociceptive function
HT SA protective role
LT SA acceleration detectors
LT SA static position and speed of movements

94
Q

where does proprioceptive information arise form

A

muscle spindles
golgi tendon organs
joint receptors

95
Q

what do inhibitory interneurones mediate

A

inverse myotonic response

reciprocal inhibition between extensor and flexor muscles

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