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Neurology Year 3 > Physiology > Flashcards

Physiology Flashcards

(91 cards)

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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
Direct postsynaptic membrane potential is activated by...
Ionotropic receptors
26
Why do inotropic receptors result in rapid opening of the ion channels?
Ionotropic receptors are integral to the ion gates
27
Indirect postsynaptic membrane potential is mediated by
Metabotropic receptors
28
Metabotropic receptors result in rapid opening of ion channels? T/F
False - Activation results in slow opening of ion channels
29
Why does metabotropic receptors cause a slow opening of ion channels?
G - protein coupled receptor | Receptor is separate to the ion channel
30
Muscarinic receptors are usually
Metabotropic
31
Nicotinic receptors are usually
Ionotropic
32
How are ionotropic receptors classified?
Via lab induced responce to foreign agonist
33
What are the two types of Ionotropic receptor
non NMDA | NMDA
34
Non-NMDA channels
Ionotropic Permeable to Na+ and K+ Fast brief AP
35
What do Non-NMDA channels react to?
AMPA and Kianic acid
36
NMDA channels
Ionotropic Permeable to Na+ Ca 2+ K+ Slow long AP
37
What do NMDA channels react to?
NMDA
38
What is a motor unit?
An alpha MN and all the skeletal muscle fibres it innervates.
39
What is a motor neurone pool?
The collection of alpha MN that supply a whole muscle.
40
What determines the force of contraction?
Frequency of AP discharge | Recruitment of additional synergistic motor units
41
What three things regulate alpha motor neurones
Central terminals of dorsal root ganglion UMN Spinal Interneurones
42
Why do twitches occur?
A isolated Alpha MN neurone firing
43
What is the difference between a twitch and a contraction?
A twitch is an isolated alpha motor neurone firing, a contraction is the summation of many alpha MN firing.
44
The motor units that control fine movements are large. T/F
False small motor units allow refined smaller muscle movements
45
What differentiates skeletal muscle fibres?
How quickly myosin ATPase splits ATP to provide energy. | Different myosin heavy chains
46
ATP - Type 1 muscle fibres
Slow Oxidative | ATP mostly from oxidative phosphorylation
47
Describe Type 1 Slow Oxidative fibres
Slow Contraction and relaxation Fatigue resistant Red fibres due to high myoglobin
48
ATP - Type 2a muscle fibres
ATP from oxidative phosphorylation
49
Describe Type 2a muscle fibres
Fast contraction and relaxation Fatigue resistance Red and reasonably well vascularised
50
ATP - Type 2b and 2x muscle fibres
ATP from glycolysis
51
Describe Type 2b and 2x muscle fibres
Fastest contraction but not fatigue resistant | Pale in colour and poorly vascularised
52
Type 2B muscle fibres are present in all mammals. | T/F
False only present in small mammals it is not found in humans.
53
What are the three types of motor unit?
Fast Contraction + Fatiguing + Very high tension Fatigue resistant + High tension Slow Contraction + Fatigue Resistant + Low tension
54
Fast Contracting, Fatiguing, Very High Tension | Describe
Large alpha MN Type 2x Burst power
55
Fatigue resistant + High tension | Describe
Intermediate alpha MN Type 2a Sustained Locomotion
56
Slow Contraction + Fatigue Resistant + Low tension | Describe
Small alphaMN Type 1 fibres Antigravity muscle
57
Why do smaller alpha MN have a lower activation threshold?
Allows fine control of muscle force as they activate prior to the larger stronger motor units. Appropriate force for the task
58
What is the Myotatic (myotonic) reflex?
Muscle spindle within the muscle registers and reacts to a change in the length of the muscle.
59
What forms a spindle fibre?
Fibrous capsule Intrafusal muscle Sensory afferents Gamma Motor neurone
60
What class is the sensory afferent found in the spindle fibre?
Type 1a | Myelinated and very fast conduction
61
What does the sensory afferent innervate in the spindle?
The intrafusal muscle which reports on the tension within the muscle.
62
What motor neurone innervates the intrafusal muscle fibre?
Gamma MN
63
What neurotransmitter regulates the myotatic reflex?
Glutamate
64
What is the function of the Gamma MN?
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
What kind of reflex is the myotatic ?
Monosynpatic
66
What are intrafusal nuclear bags?
Sensory muscle fibres that lie in the middle of the Spindle fibres.
67
What are the two types of Nuclear Bag?
Bag 1 - Gama MN | Bag 2- Static Gamma MN
68
Static Gamma MN
Sensitive to the absolute length of the muscle
69
Bag 1 Gamma MN
Very sensitive to the rate of change
70
How many afferent fibre innervate the intrafusal bag?
Two 1a = A alpha - wraps around all the fibres 2 = A Beta - Slower conducting wraps all fibres except dynamic Bag 1.
71
From the two afferent fibres which innervate the intrafusal bag which is more sensitive to rate?
1a
72
In slow and predictable muscle movement which MN are active?
Static Gamma MNs
73
In rapid and unpredictable muscle movement which MNs are active?
Dynamic Gamma MNs
74
Where are Golgi tendons organs located?
At the junction between the tendon and the muscle.
75
What is the purpose of the Golgi tendon organs?
To monitor changes in the extrafusal muscle tension to prevent muscle overload and regulate tension to an optimal range.
76
What innervates the Golgi tendon organs?
Type 1b sensory
77
Describe 1b sensory neurones
Myelinated slower than 1a
78
If type 1b neurones detect too much tension within the Golgi tendon organ what happens?
Synapse onto a inhibitory interneurone | Interneurone synapses onto an alpa MN of homogenous muscle, leading to a reduction in tension.
79
What two key things help in proprioception?
Threshold | Adaption
80
What is threshold?
The strength of the stimuli required to initiate an action potential.
81
What is adaptability?
Slow adapting - AP produced so long as stimuli is present | Fast adapting - AP produced only at the moment stimuli is applied
82
Describe free nerve endings
High Threshold Slow Adapting Nociceptive (Pain)
83
Describe Golgi type
High Threshold Slow Adapting Protective
84
Describe Paciniform
Low threshold Fast Adapting Found within periosteum - detects acceleration light touch in dermis and fascia etc
85
Describe Ruffini
Low Threshold Slow Adapting Static position and location of the joint Found in joint capsule
86
Where do spinal interneurones get input from?
Primary sensory axons Descending axons Collaterals Other interneurones
87
What is the role of spinal inter neurones?
Intergate incoming information to generate an output, much quicker as no conscious input.
88
What is the main role of inhibitory interneurones?
Mediate Reciprocal inhibition | Generally for a joint to move the antagonistic muscle needs to be relaxed.
89
What are two reflexes that the excitatory interneurones control?
Flexor reflex | Crossed extensor reflex
90
What is the flexor reflex?
Contraction of the flexor | Relaxation of the extensor via excitatory and inhibitory
91
What is the crossed extensor reflex?
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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