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Neurology > Physiology > Flashcards

Physiology Flashcards

1
Q

What are dendrites?

A

Terminals that receive electrical impulses and convey these to the soma.

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2
Q

What is the metabolic centre of a neuron also known as?

A

The soma.

It is the cell body.

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3
Q

What occurs at the axon hillock?

A

Action potential initiation.

Where information received is assimilated.

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4
Q

Once the APs have left the soma, where do they head?

A

Presynaptic cleft

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5
Q

An AP heading from the soma to the presynaptic cleft is said to be what?

A

Anterograde

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6
Q

An AP heading from the presynaptic cleft to the soma is said to be what?

A

Retrograde

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7
Q

What occurs at the synapse?

A

Chemical communication.

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8
Q

Give examples of viruses that exploit retrograde transport.

A

Herpes
Polio
Rabies

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9
Q

What are the 4 main functional regions of a neuron?

A

Input
Integrative
Conductive
Output

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10
Q

What are the 4 different types of neuron?

A

Unipolar
Pseudounipolar
Bipolar
Multipolar

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11
Q

In AP generation, does Na+ influx precede K+ efflux?

A

Yes

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12
Q

What is the length constant?

A

The distance a current can spread before it diminishes to 0.

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13
Q

Is conduction faster in myelinated or non-myelinated axons?

A

Myelinated axons.

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14
Q

In myelinated axons, what are the areas that APs jump between referred to as?

A

Nodes of Ranvier

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15
Q

What occurs at the Nodes of Ranvier?

A

Na+ influx.

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16
Q

Give 2 examples of demyelinating conditions?

A

Guillain-Barre syndrome

Multiple sclerosis

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17
Q

What effect does demyelination have on AP conduction?

A

Slows it down.

Can lead to compete cessation in severe disease.

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18
Q

What ion is responsible for the release of the neurotransmitters into the synaptic cleft following AP conduction?

A

Ca2+

Enters the presynaptic cleft via the voltage-gated channels.

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19
Q

What is found in the presynaptic cleft area?

A

Vesicles

These contain inactive neurotransmitters, awaiting release.

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20
Q

What is found in the postsynaptic cleft area?

A

Many receptors to bind the neurotransmitters upon their release.

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21
Q

What neurotransmitter most commonly activates excitatory synapses?

A

Glutamate

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22
Q

What are the 2 main roles a synapse can play?

A

Excitatory

Inhibitory

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23
Q

What neurotransmitters are inhibitory in the CNS?

A

GABA

Glycine

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24
Q

What is temporal summation?

A

When a single pre-synaptic neuron fires many times, resulting in a postsynaptic neuron reaching its threshold.

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25
Q

What is the role of the somatosensory system?

A

Detecting stimuli from across the body.

May be of internal or external origin.

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26
Q

What do low threshold receptors respond to?

A

Non-harmful stimuli.

These include fine discriminatory touch.

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27
Q

What do high threshold receptors respond to?

A

Noxious stimulation.

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28
Q

How many neurons are typically involved in a somatosensory pathway?

A

3 neurons.

1st order is in the PNS.

2nd and 3rd order is in the CNS.

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29
Q

Where does all sensory information collected travel to?

A

The primary somatosensory cortex.

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30
Q

What is meant by adaptation rate?

A

The intensity of stimulation needed to excitate the receptor.

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31
Q

Receptors with a high threshold are responsible for what?

A

Pain or other noxious stimuli.

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32
Q

What is the function of slow adapting sensory units?

A

Provide continuous information to the CNS.

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33
Q

What is adaptation?

A

A feature of sensory units that determines whether the rate of AP discharge changes, or remains constant, due to a stimulus.

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34
Q

What do fast adapting sensory units do?

A

Rapid movements.

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35
Q

The area supplied by peripheral nerve endings is called what?

A

The receptor field.

This varies in size dependent on where it is located on the body.

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36
Q

What is the relationship between sensory acuity and the size of the receptor field?

A

As receptor field decreases, sensory acuity increases (converse also applies).

37
Q

What is the benefit of having many receptors close together?

A

Allows for a greater degree of discrimination between receptor fields - higher sensitivity.

38
Q

Where is the area of highest innervation density?

A

The fingers.

39
Q

What is the name of the mechanoreceptor responsible for fine touch and pressure?

A

Meissner’s corpuscle

40
Q

Where is the cell body of a spinal nerve located?

A

Dorsal root ganglion

41
Q

What is found within a dorsal root?

A

Sensory neurons that innervate a single dermatome.

42
Q

What test is used to test somatosensory function?

A

Two-point discrimination

43
Q

How many pairs of spinal nerves are there?

A

31 sets.

44
Q

What is the virus responsible for shingles and chickenpox?

A

Varicella zoster

45
Q

Once infected with varicella zoster, where does it live?

A

The dorsal root ganglion.

46
Q

What does grey matter contain?

A

Neuronal cell bodies

Afferent terminals

47
Q

What does white matter contain?

A

Fibre tracts

48
Q

Where does crossover of the DCML tract fibres occur?

A

The brainstem.

49
Q

The process of nerve fibres crossing to their contralateral side is called what?

A

Decussation

50
Q

What is the DCML pathway responsible for?

A

Fine touch
Pressure
Vibration
Proprioception

51
Q

Where does decussation of the spinothalamic tract occur?

A

Within the spinal column, prior to reaching the thalamus.

52
Q

Where does information from the DCML and spinothalamic tract head to?

A

Primary somatosensory cortex

53
Q

In the spinothalamic tract, does decussation occur at every spinal level?

A

Yes

54
Q

The medial tract of the DCML is called the gracile. What information is carried here?

A

Sensory afferents of the legs and lower trunk.

55
Q

Input from T6 and above is carried in the DCML via the lateral tract. What is it called?

A

Cuneate tract.

56
Q

Where do the gracile tracts of the DCML synapse?

A

Gracile nucleus of the brainstem.

57
Q

Where do the cuneate tracts of the DCML synapse?

A

Cuneate nucleus of the brainstem.

58
Q

Name 5 abilities conveyed by the DCML.

A 
Stereognosis
Fine touch
Conscious proprioception
Vibration detection
Weight discrimination
59
Q

What is contrast enhancement?

A

The process by which one neuron in a sensory pathway, when activated, can amplify the difference in activity in the surrounding neurons.

This allows the exact neuron triggered to be ascertained.

60
Q

What is lateral inhibition?

A

When one neuron is active, it inhibits the surrounding neurons.

This sharpens perception of stimulus, allowing localisation of the sensation.

61
Q

Where is the somatosensory cortex located?

A

Post central gyrus.

62
Q

What are the subdivisions of the PSC called?

A

Brodmann bands

There are 4 of these - 1, 2, 3a, and 3b.

63
Q

What are Brodmann bands 3a and 3b responsible for?

A

Proprioception and other touch information.

64
Q

What areas have the greatest representation within the PSC?

A

The hands and face due to high levels of receptors in these areas (high sensitivity).

65
Q

What is the role of the posterior parietal cortex in somatosensation?

A

Receive and integrate information from the PSC, allowing the deeper meaning of the information to be deciphered.

66
Q

What is the role of cerebral pattern generators?

A

To allow simple activities to be carried out without thought.

An example is walking.

67
Q

Where are UMNs found?

A

Within the brain.

68
Q

Where are LMNs found?

A

Within the brainstem or the ventral horn of the spinal cord.

69
Q

What are LMNs made of?

A

Alpha-MNs

Gamma-MNs

70
Q

What sources supply information to LMNs?

A

UMNs
Proprioception
Interneurons

71
Q

What is the role of alpha-MNs?

A

To innervate the bulk of muscle fibres in order to generate a force.

72
Q

What is the role of gamma-MNs?

A

To innervate a sensory organ within the muscle.

The sensory organ is a muscle spindle.

73
Q

What is the name given to a group of muscles that work together in order to carry out a function?

A

Synergists

74
Q

What are antagonistic muscles?

A

Those that work to oppose each other.

75
Q

What do axial muscles do?

A

Maintain posture.

76
Q

What do proximal muscles do?

A

Mediate locomotion.

77
Q

Where do the axons of LMNs exit the spinal cord?

A

The ventral roots.

78
Q

Anterior/Ventral roots consist of which fibres?

A

Motor fibres

79
Q

Posterior/Dorsal roots consist of which fibres?

A

Sensory fibres

80
Q

At which points is there a greater distribution of motor neurons?

A

Cervical enlargement

Lumbar enlargement

81
Q

Between which vertebrae levels is the cervical enlargement found?

A

C5-T1

82
Q

Between which vertebrae levels is the lumbar enlargement found?

A

L1-S3

83
Q

What comprises a motor unit?

A

Alpha-MN

All of the skeletal muscle it innervates

84
Q

What is a motor pool?

A

The collection of motor neurons that innervate a single muscle.

85
Q

What 2 factors influence the strength of a muscle contraction?

A

The frequency of AP discharge

The recruitment of additional motor units

86
Q

What differs between slow-twitch and fast-twitch fibres?

A

The rate at which ATP is hydrolysed.

87
Q

Which type of muscle fibres are fatigue-resistant?

A

Type 1 fibres

88
Q

Can a muscle contract if only alpha-MNs are activated?

A

No, they will be inhibited by gamma-MNs.

Co-activation is key to contraction.

Neurology (22 decks)

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