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3MB Neurology > Peters Physiology > Flashcards

Peters Physiology Flashcards

1
Q

List the main components of neuronal structure

A

Dendrites
Soma (cell body)
Axon hillock + initial segment
Axon
Synapse

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2
Q

What is the main function of dendrites?

A

Receive neuronal inputs and convey graded signals towards the soma

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3
Q

The soma of the neurone is the metabolic centre. List the structures it contains

A

Nucleus
Ribosomes
Mitochondria
Endoplasmic reticulum
Nissl substance

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4
Q

What is Nissl substance?

A

Rough endoplasmic reticulum (ER with ribosomes)

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5
Q

Which part of the neurone is the site of initiation of an action potential?

A

Axon hillock + initial segment

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6
Q

What is the main function of an axon?

A

Conducts action potentials to other neurones or cells

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7
Q

Electrical info/material can travel from the soma to presynaptic terminal (anterograde) and vice versa (retrograde). True/False?

A

True
Retrograde travel can welcome infection (e.g. polio)

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8
Q

What is a synapse?

A

Point of chemical communication between 2 neurones

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9
Q

List the 4 main types of neurone

A

Unipolar
Pseudounipolar
Bipolar
Multipolar

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10
Q

Describe a unipolar neurone and give an example of where it may be found

A

No dendrite; soma only gives off axon
e.g. peripheral autonomic neurone

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11
Q

Describe a pseudounipolar neurone and give an example of where it may be found

A

Short axon bifurcates into soma and central axon
e.g. dorsal root ganglion neurone

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12
Q

Describe a bipolar neurone and give an example of where it may be found

A

Dendrite + soma + axon
e.g. retinal bipolar neurone

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13
Q

Describe a multipolar neurone and give an example of where it may be found

A

3 or more neurites attached to soma
e.g. lower motor neurone

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14
Q

What is the difference between Golgi type I and type II axons?

A

Golgi type I = long axon
Golgi type II = short axon

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15
Q

Which channels open in neurones when membrane polarity reaches threshold (-60mV) to cause the upstroke of the action potential?

A

Na channels

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16
Q

Which 2 factors determine the distance over which electrical current spreads in a neurone?

A

Membrane resistance
Axoplasm resistance

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17
Q

Increasing membrane/axoplasm resistance increases the distance travelled by electrical current

A

Increasing membrane resistance increases the distance travelled by electrical current
(less current leaks out)

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18
Q

A narrow axon provides high/low resistance to conduction velocity

A

A narrow axon provides high resistance to conduction velocity

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19
Q

Which insulating material can help increase conduction velocity in neurones by reducing current leak?

A

Myelin

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20
Q

Which cells produce myelin for neurones?

A

Schwann cells in PNS
Oligodendrocytes in CNS

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21
Q

Many schwann cells and oligodendrocytes surround axons. True/False?

A

False
Many schwann cells surround one axon but usually only one oligodendrocyte surrounds many axons

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22
Q

Which region does the action potential “jump” from to get between neurones in myelinated axons?

A

Nodes of Ranvier

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23
Q

What are the 3 main morphological classifications of a synapse?

A

Axodendritic (most common)
Axosomatic
Axoaxonic (least common)

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24
Q

Synapses can be excitatory or inhibitory. Respectfully, what are the main transmitters involved for each?

A

Glutamate for excitatory CNS
GABA or glycine for inhibitory CNS

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25
Q

The excitatory postsynaptic potential (epsp) is depolarizing and the inhibitory postsynaptic potential (ipsp) is hyperpolarizing. True/False?

A

True

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26
Q

If an epsp is too weak to cause synapse, how can excitation be achieved?

A

Converge multiple epsp’s to cause net excitation (synaptic summation)

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27
Q

List the sensory modalities that come under the somatosensory system

A

Touch
Proprioception
Temperature
Pain
Itch

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28
Q

What happens to the energy generated by a stimulus at a sensory nerve cell terminal?

A

Transduced into electrical activity which creates depolarizing (generator) potential which, if strong enough, can trigger action potential

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29
Q

Which receptors aid with proprioception?

A

Joint and muscle mechnoreceptors

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30
Q

Adaptation determines the firing rate of sensory neurones in response to changing stimuli. Describe the slow-adapting response

A

Continuous information whilst nerve being stimulated
Gives info about position, stretch, force

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31
Q

Adaptation determines the firing rate of sensory neurones in response to changing stimuli. Describe the rapid-adapting response

A

Detects change in stimulus strength and rate of movement

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32
Q

Adaptation determines the firing rate of sensory neurones in response to changing stimuli. Describe the very-rapid-adapting response

A

Responds only to very fast movement (vibration)

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33
Q

Primary sensory afferent fibres are grouped I-IV or Aα, Aβ, Aδ, C. Order the groups from thickest-least thickest myelination, i.e. from fastest conduction velocity to slow

A

Group I, group II, group III, group IV
AKA
Aα, Aβ, Aδ, C

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34
Q

What is meant by the receptive field of a sensory neurone?

A

The region which, when stimulated, produces a response in that neurone

35
Q

Which type of sensory receptor do Aα primary sensory afferents conduct?

A

Proprioceptors

36
Q

Which type of sensory receptor do Aβ primary sensory afferents conduct?

A

Mechanoreceptors of skin

37
Q

Which type of sensory receptor do Aδ primary sensory afferents conduct?

A

Nociceptors
Thermoreceptors

38
Q

Which type of sensory receptor do C primary sensory afferents conduct?

A

Nociceptors
Thermoreceptors
Itch receptors

39
Q

What do free nerve endings in skin help sense?

A

Pain
Temperature

40
Q

What do Meissner’s corpuscles in skin help sense?

A

Touch/vibration

41
Q

What do Merkel’s discs in skin help sense?

A

Touch

42
Q

What do Ruffini endings in skin help sense?

A

Pressure

43
Q

What do Pacinian corpuscles in skin help sense?

A

Pressure

44
Q

Two point discrimination is being able to distinguish 2 stimuli separately without overlap. Which corpuscles have higher 2 point discrimination - Pacinian or Meissner’s?

A

Meissner’s corpuscles
(less overlap of receptive fields)

45
Q

Meissner’s corpuscles, Ruffini endings, Merkel discs, Pacinian corpuscles and long hair are all supplied by which sensory fibre type?

A

Aβ

46
Q

Short hair is supplied by which sensory fibre type?

A

Aδ

47
Q

What is a dermatome?

A

Area of skin innervated by left and right dorsal roots of a spinal nerve

48
Q

The spinal cord consists of grey and white matter. Ascending the cord, the proportion of which matter increases?

A

Proportion of white matter increases as you ascend the spinal cord

49
Q

Nociceptors (fibre class ___) terminate at laminae _ and _

A

Nociceptors (fibre class Aδ/C) terminate at laminae I and II

50
Q

Low-threshold mechanoreceptors (fibre class ___) terminate between laminae _ and _

A

Low-threshold mechanoreceptors (fibre class Aβ) terminate between laminae III and VI

51
Q

Proprioceptors (fibre class ___) terminate between laminae _ and _

A

Proprioceptors (fibre class Aα) terminate between laminae VII and IX

52
Q

What are the 2 main tracts of the somatic sensory pathway?

A

Dorsal column medial leminscal pathway
Spinothalamic tract

53
Q

The dorsal column of the somatosensory pathway conveys Aα/Aβ sensory fibre info (proprioception, touch). Where does the 1’ neurone synapse in the spinal cord?

A

All fibres synapse in brainstem and crossover to opposite side onto 2’ neurone

54
Q

The spinothalamic tract of the somatosensory pathway conveys Aδ/C sensory fibre info (pain, temperature). Where does the 1’ neurone synapse in the spinal cord?

A

Synapses shortly after entry into spinal cord; fibres crossover to opposite side at different points along the cord in 2’ neurone

55
Q

Where do the 2’ neurones in the somatosensory tracts synapse?

A

Thalamus

56
Q

Dorsal columns of the somatosensory pathway consist of which 2 tracts?

A

Fasciculus gracilis
Fasciculus cuneatus

57
Q

Sensory input from which spinal regions travels in fasciculus gracilis?

A

From T6 and below (legs and lower trunk)

58
Q

Sensory input from which spinal regions travel in fasciculus cuneatus?

A

From T6 and above (arms and upper trunk)

59
Q

What is meant by contrast enhancement in the sensory pathway?

A

As information is conveyed between neurones, differences in activity between adjacent neurones are amplified

60
Q

Which part of the brain receives the sensory information from the somatosensory pathway (dorsal column medial lemniscus pathway + spinothalamic tract)?

A

Post-central gyrus (primary somatosensory cortex) via the thalamus

61
Q

What is stereognosis?

A

Ability to recognise an object by feeling it

62
Q

Which cranial nerve provides sensory innervation to the face?

A

Trigeminal nerve
(trigeminothalamic pathway)

63
Q

Outline (roughly) the sensory facial areas innervated by divisions of the trigeminal nerve

A

Ophthalmic: nose upwards
Maxillary: ala, cheeks, lateral forehead, upper lip
Mandibulary: lower lip, jaw, earline

64
Q

Once central terminals of the trigeminal synapse, in what do they travel to the thalamus?

A

Trigeminal lemniscus (runs parallel to dorsal column median lemniscus)

65
Q

Where is the somatosensory cortex located?

A

In the post central gyrus of the parietal cortex, posterior to central sulcus

66
Q

What is the name of the areas contained within the somatosensory cortex?

A

Broadmann areas (1, 2, 3a, 3b)

67
Q

The somatosensory cortex receives input from the ventral posterolateral thalamus. What proportion of input goes to each Broadmann area?

A

70% to Broadmann 3a + 3b
30% to Broadmann 1 + 2

68
Q

What is the name of the somatotropic map of the body surface present on the somatosensory cortex? What does it represent?

A

Sensory homunculus
Reveals relative sensory cortical power devoted to each body part

69
Q

There are 6 cell layers (I-VI) to the somatosensory cortex - upon which layer do thalamic inputs usually terminate?

A

Layer IV neurones

70
Q

Give an explanation for phantom pain experienced following amputation

A

Cortical remapping involves the area formerly represented by the amputated body part being stimulated by adjacent body part as per the somatotropic map (homunculus)

71
Q

What is a ‘motor neurone pool’?

A

Collection of alpha-motor neurones that innervate a single muscle

72
Q

What is the myotatic reflex?

A

When a skeletal muscle is pulled, a reverse (protective) force in the muscle spindle pulls it back

73
Q

What is contained within a muscle spindle?

A

Intrafusal muscle fibre
Ia sensory afferents
Gamma-motor neurone efferents

74
Q

What is the benefit of stimulating intrafusal and extrafusal fibres (alpha and gamma -motor neurones) at the same time?

A

Prevents the muscle spindle from going slack

75
Q

What is the function of Golgi tendon organs?

A

Monitor changes in muscle tension to protect from overload

76
Q

Where are Golgi tendon organs located?

A

At the junction between tendon and muscle

77
Q

Group Ib afferents innervate Golgi tendon organs and synapse with alpha-motor neurones via inhibitory interneurons of the contracted muscle. What is the ultimate reflex that occurs?

A

Reverse myotatic reflex that maintains muscle tension within safe limits

78
Q

Inhibitory interneurons mediate which reflexes in flexion/extension of muscle?

A

Reverse myotatic response
Reciprocal inhibition

79
Q

The myotatic reflex and reciprocal inhibition occur to produce desired movement. Outline the process using quadriceps + hamstring muscle

A

Quadriceps contraction requires hamstring relaxation - Ia fibre supplying the alpha-motor neurone of the quadriceps inhibits the alpha-motor neurone of the hamstring VIA an inhibitory interneuron

80
Q

Excitatory interneurons mediate which reflexes in flexion/extension of muscle?

A

Stretch reflex
Crossed extensor reflex

81
Q

What is the main lateral pathway for descending spinal tracts?

A

Corticospinal tract

82
Q

Nociceptors are primary afferent neurones comprising __ fibres and __ fibres

A

Nociceptors are primary afferent neurones comprising Aδ fibres and C fibres

83
Q

Which fibres - Aδ or C - mediate first/fast pain?

A

Aδ fibres

84
Q

Which fibres - Aδ or C - mediate second/slow pain?

A

C fibres

3MB Neurology (17 decks)

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