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Neurology Year 3 > Physiology > Flashcards

Physiology Flashcards

1
Q

Where on the neurone decides whether to initiate an all or nothing action potential?

A

Axon Hillock

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2
Q

Unipolar neurones occur where?

A

Peripheral autonomic

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3
Q

Pseudounipolar neurones occur where?

A

Dorsal root ganglion

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4
Q

Bipolar neurones occur where?

A

Retinal bipolar neurone

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5
Q

Multipolar neurones occur where?

A

Lower motor neurones

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6
Q

What triggers the upstroke within a neuronal AP?

A

Na + influx

Voltage gated Na+ channels

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7
Q

What triggers the downstroke within a neuronal AP?

A

K+ efflux

Voltage gated K+ channels

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8
Q

Why if signalling was passive would the AP diminish as it travels along the neurone?

A

The membrane is leaky allowing ions to exit the axon and reducing the concentration gradient reducing speed of transmission.

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9
Q

Saltatory Conduction is enabled by what?

A

The nodes of Ranvier formed between myelin sheath.

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10
Q

Why does myelination increase the speed of conduction?

A

As it insulates the axons preventing leakage of ions and maintaining the concentration gradient.
Ion channels only located at nodes thus conduction jumps from one node to the next.

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11
Q

How would you increase the passive conduction speed of a neurone?

A

Decrease Ri - Increase axon diameter

Increase Rm - Add insulating material

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12
Q

Influx of what ion causes the exocytosis of vesicles containing the neurotransmitter?

A

Ca 2+

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13
Q

What types of synapse are there?

A

Axodendritic
Axosomatic
Axoaxonic

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14
Q

Axodendritic

A

Synapse between axon and dendrite

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15
Q

Axosomatic

A

Synapse between axon and Soma ( cell body )

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16
Q

Axoaxonic

A

Synapse between axon and axon

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17
Q

What is the main excitatory neurotransmitter?

A

Glutamate

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18
Q

How does Glutamate cause an increased +ve AP?

A

Activates postsynaptic Cation selective channels

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19
Q

What is the main inhibitory neurotransmitter?

A

GABA

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20
Q

How does GABA cause an increased -ve AP?

A

Activates postsynaptic anion selective channels

Influx of Cl- ion

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21
Q

What are the two main forms of synaptic summation?

A

Spatial and Temporal Summation

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22
Q

What is the purpose behind summation?

A

Calculation of excitatory and inhibitory AP that responds too many stimuli from the surroundings allowing a proportionate response.

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23
Q

Spatial Summation

A

Convergence of many inputs upon a neurone to determine its output.
Determined by the axon hillock whether the sum of the AP input is enough to surpass the threshold to trigger an all or nothing response.

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24
Q

Temporal Summation

A

If a single input fires frequently enough it can trigger an all or nothing response.

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25
Q

Direct postsynaptic membrane potential is activated by…

A

Ionotropic receptors

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26
Q

Why do inotropic receptors result in rapid opening of the ion channels?

A

Ionotropic receptors are integral to the ion gates

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27
Q

Indirect postsynaptic membrane potential is mediated by

A

Metabotropic receptors

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28
Q

Metabotropic receptors result in rapid opening of ion channels? T/F

A

False - Activation results in slow opening of ion channels

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29
Q

Why does metabotropic receptors cause a slow opening of ion channels?

A

G - protein coupled receptor

Receptor is separate to the ion channel

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30
Q

Muscarinic receptors are usually

A

Metabotropic

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31
Q

Nicotinic receptors are usually

A

Ionotropic

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32
Q

How are ionotropic receptors classified?

A

Via lab induced responce to foreign agonist

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33
Q

What are the two types of Ionotropic receptor

A

non NMDA

NMDA

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34
Q

Non-NMDA channels

A

Ionotropic
Permeable to Na+ and K+
Fast brief AP

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35
Q

What do Non-NMDA channels react to?

A

AMPA and Kianic acid

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36
Q

NMDA channels

A

Ionotropic
Permeable to Na+ Ca 2+ K+
Slow long AP

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37
Q

What do NMDA channels react to?

A

NMDA

38
Q

What is a motor unit?

A

An alpha MN and all the skeletal muscle fibres it innervates.

39
Q

What is a motor neurone pool?

A

The collection of alpha MN that supply a whole muscle.

40
Q

What determines the force of contraction?

A

Frequency of AP discharge

Recruitment of additional synergistic motor units

41
Q

What three things regulate alpha motor neurones

A

Central terminals of dorsal root ganglion
UMN
Spinal Interneurones

42
Q

Why do twitches occur?

A

A isolated Alpha MN neurone firing

43
Q

What is the difference between a twitch and a contraction?

A

A twitch is an isolated alpha motor neurone firing, a contraction is the summation of many alpha MN firing.

44
Q

The motor units that control fine movements are large. T/F

A

False small motor units allow refined smaller muscle movements

45
Q

What differentiates skeletal muscle fibres?

A

How quickly myosin ATPase splits ATP to provide energy.

Different myosin heavy chains

46
Q

ATP - Type 1 muscle fibres

A

Slow Oxidative

ATP mostly from oxidative phosphorylation

47
Q

Describe Type 1 Slow Oxidative fibres

A

Slow Contraction and relaxation
Fatigue resistant
Red fibres due to high myoglobin

48
Q

ATP - Type 2a muscle fibres

A

ATP from oxidative phosphorylation

49
Q

Describe Type 2a muscle fibres

A

Fast contraction and relaxation
Fatigue resistance
Red and reasonably well vascularised

50
Q

ATP - Type 2b and 2x muscle fibres

A

ATP from glycolysis

51
Q

Describe Type 2b and 2x muscle fibres

A

Fastest contraction but not fatigue resistant

Pale in colour and poorly vascularised

52
Q

Type 2B muscle fibres are present in all mammals.

T/F

A

False only present in small mammals it is not found in humans.

53
Q

What are the three types of motor unit?

A

Fast Contraction + Fatiguing + Very high tension
Fatigue resistant + High tension

Slow Contraction + Fatigue Resistant + Low tension

54
Q

Fast Contracting, Fatiguing, Very High Tension

Describe

A

Large alpha MN
Type 2x
Burst power

55
Q

Fatigue resistant + High tension

Describe

A

Intermediate alpha MN
Type 2a
Sustained Locomotion

56
Q

Slow Contraction + Fatigue Resistant + Low tension

Describe

A

Small alphaMN
Type 1 fibres
Antigravity muscle

57
Q

Why do smaller alpha MN have a lower activation threshold?

A

Allows fine control of muscle force as they activate prior to the larger stronger motor units.
Appropriate force for the task

58
Q

What is the Myotatic (myotonic) reflex?

A

Muscle spindle within the muscle registers and reacts to a change in the length of the muscle.

59
Q

What forms a spindle fibre?

A

Fibrous capsule
Intrafusal muscle
Sensory afferents
Gamma Motor neurone

60
Q

What class is the sensory afferent found in the spindle fibre?

A

Type 1a

Myelinated and very fast conduction

61
Q

What does the sensory afferent innervate in the spindle?

A

The intrafusal muscle which reports on the tension within the muscle.

62
Q

What motor neurone innervates the intrafusal muscle fibre?

A

Gamma MN

63
Q

What neurotransmitter regulates the myotatic reflex?

A

Glutamate

64
Q

What is the function of the Gamma MN?

A

To accurately record an inform on the tension within the whole muscle the intrafusal muscle fibre must be kept at the same tension as the whole muscle.
This achieved by the gamma MN

65
Q

What kind of reflex is the myotatic ?

A

Monosynpatic

66
Q

What are intrafusal nuclear bags?

A

Sensory muscle fibres that lie in the middle of the Spindle fibres.

67
Q

What are the two types of Nuclear Bag?

A

Bag 1 - Gama MN

Bag 2- Static Gamma MN

68
Q

Static Gamma MN

A

Sensitive to the absolute length of the muscle

69
Q

Bag 1 Gamma MN

A

Very sensitive to the rate of change

70
Q

How many afferent fibre innervate the intrafusal bag?

A

Two
1a = A alpha - wraps around all the fibres
2 = A Beta - Slower conducting wraps all fibres except dynamic Bag 1.

71
Q

From the two afferent fibres which innervate the intrafusal bag which is more sensitive to rate?

A

1a

72
Q

In slow and predictable muscle movement which MN are active?

A

Static Gamma MNs

73
Q

In rapid and unpredictable muscle movement which MNs are active?

A

Dynamic Gamma MNs

74
Q

Where are Golgi tendons organs located?

A

At the junction between the tendon and the muscle.

75
Q

What is the purpose of the Golgi tendon organs?

A

To monitor changes in the extrafusal muscle tension to prevent muscle overload and regulate tension to an optimal range.

76
Q

What innervates the Golgi tendon organs?

A

Type 1b sensory

77
Q

Describe 1b sensory neurones

A

Myelinated slower than 1a

78
Q

If type 1b neurones detect too much tension within the Golgi tendon organ what happens?

A

Synapse onto a inhibitory interneurone

Interneurone synapses onto an alpa MN of homogenous muscle, leading to a reduction in tension.

79
Q

What two key things help in proprioception?

A

Threshold

Adaption

80
Q

What is threshold?

A

The strength of the stimuli required to initiate an action potential.

81
Q

What is adaptability?

A

Slow adapting - AP produced so long as stimuli is present

Fast adapting - AP produced only at the moment stimuli is applied

82
Q

Describe free nerve endings

A

High Threshold
Slow Adapting
Nociceptive (Pain)

83
Q

Describe Golgi type

A

High Threshold
Slow Adapting
Protective

84
Q

Describe Paciniform

A

Low threshold
Fast Adapting
Found within periosteum - detects acceleration
light touch in dermis and fascia etc

85
Q

Describe Ruffini

A

Low Threshold
Slow Adapting
Static position and location of the joint
Found in joint capsule

86
Q

Where do spinal interneurones get input from?

A

Primary sensory axons
Descending axons
Collaterals
Other interneurones

87
Q

What is the role of spinal inter neurones?

A

Intergate incoming information to generate an output, much quicker as no conscious input.

88
Q

What is the main role of inhibitory interneurones?

A

Mediate Reciprocal inhibition

Generally for a joint to move the antagonistic muscle needs to be relaxed.

89
Q

What are two reflexes that the excitatory interneurones control?

A

Flexor reflex

Crossed extensor reflex

90
Q

What is the flexor reflex?

A

Contraction of the flexor

Relaxation of the extensor via excitatory and inhibitory

91
Q

What is the crossed extensor reflex?

A

Painful stimuli on one side
Opposite limb contraction of extensor
relaxation of flexor
Enhances postural support during withdrawal of limb from painful stimuli.

Neurology Year 3 (29 decks)

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