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Neurology Y3 JC > Basic Science > Flashcards

Basic Science Flashcards

1
Q

Influx of what ion into a neurone causes depolarisation of the membrane

A

sodium

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2
Q

Efflux of what ion causes hyperpolarisation of a cell membrane

A

Potassium

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3
Q

What part of the axon is responsible for integrating information recieved from the dendrites?

A

The axon hilock

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4
Q

In order to allow conduction of signals along a long axon. What conditions need to be met

A

High membrane resistance (no leakiness)
And cytoplasm needs to have a low resistance

This is known as the length constant

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5
Q

What cells mylenate the PNS

A

Schwann cells

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6
Q

What cells myelante the CNS

A

Oligodendricytes

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7
Q

What is the demyelinating disorder that occurs in the CNS and the PNS

A

CNS; Multiple sclerosis

PNS; guillian barre syndrome

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8
Q

What is the neurotransmitter that commonly is involved in excitatory pathways?

A

Glutamate that then acts on ionotropic glutamate receptors

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9
Q

What is the neurotransmitter that commonly is involved in inhibitory pathways?

A

GABA and glycine

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10
Q

What ion entry does glutamate acting on its receptors cause?

A

Glutamate is the excitatory pathway so causes cation entry such as sodium

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11
Q

What ion entry does GABA and glycine acting on its receptors cause?

A

It is involved in the inhibitory pathway so chloride influx

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12
Q

What is a axodendritic synapse?

A

One where the synapse is between a recieving dendrite and the axon

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13
Q

What is a axosomatic synapse?

A

One where the synapse is between the recieving cell body and the axon

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14
Q

What is an axoaxonic synpase?

A

One where the synapse is between the axon transmitting and an axon to influence the transmitting axon

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15
Q

Define spatial summation?

A

Where many inputs to a neurone converge to determine its output

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16
Q

Define temporal summation

A

Where there are many stimuli from the SAME neuronal synapse that then summate to generate an AP

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17
Q

What is a metabotropic receptor?

A

Where a receptor causes the channel to become more or less gated e.g turn off or on. They produce a slow response

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18
Q

What is an ionotropic receptor

A

They are direct channels without gates. Producing a rapid response

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19
Q

What are the three subcategories for the somatosensory system

A

Exteroceptive division
Proprioceptive division
Enteroceptive division

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20
Q

What components comprise the sensory unit

A

Terminal sensory receptors, cell bodies and axons

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21
Q

Describe the pathway of sensory neurones from the dorsal root ganglia to the brain

A

First order neurones to synapse in the dorsal horn of spinal cord
Second order; from dorsal horn to thalamus (projection neurones)
Third order; thalamus to somatosensory cortex (postcentral gyrus)

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22
Q

What is action potential frequency correlated to in a neurone

A

Stimulus strength. As stimulus strength increases the number of sensory neurones activated increases hence frequency increases

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23
Q

Why does the white matter in the spinal cord increase with ascension from lumbar to sacral?

A

Due to the increasing of information that comes up to the brain e.g more axons

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24
Q

Different segments of the sensory receptors synapse in different segments of the dorsal horn known as laminae of rexed. Where do the nociceptors synapse in the spinal cord?

A

Nociceptors are pain fibres that synpase in laminae I-II

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25
Q

Different segments of the sensory receptors synapse in different segments of the dorsal horn known as laminae of rexed. Where do the LTMs synapse in the spinal cord?

A

LTMs are touch fibres and synapse in laminae III to VI

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26
Q

Different segments of the sensory receptors synapse in different segments of the dorsal horn known as laminae of rexed. Where do the proprioceptors synapse in the spinal cord?

A

Proprioceptors are the sensory that let you know where your limbs are in space. ,they synapse in laminae VII to IX. Which is also in the ventral horn due to them being involved in the reflex arc so they synapse with the motor neurones.

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27
Q

What is sterognosis? Which tract facilitates it?

A

The ability to recognise an object by feeling it as delivered by the dorsal column/ medial lemniscal pathway

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28
Q

What is lateral inhibition?

A

Where an inhibitory interneurone beween two other firing neurones will dampen ones signal in order to hear the other. Allows the neurone with most stimulus to get through.

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29
Q

Where are the soma of the sensory neurones from the trigeminothalamic pathways located?

A

The trigeminal sensory ganglion

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30
Q

Where is the synapse for general tactile stimuli coming from the trigeminothalamic pathway?

A

Cheif sensory nucleus where the axon then goes to the ventroposeriomedial nucleus of the thalamus

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31
Q

Where is the synapse for pain and temperature stimuli coming from the trigeminothalamic pathway?

A

Spinal nucleus where the axon then goes to ventroposteriomedial nucleus of the thalamus

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32
Q

What are the sensory modalities subserved by the dorsal column/ medial lemniscus system?

A

Involved with touch and conscious proprioception. Used to locate exact places of light touch

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33
Q

In the somatosensory cortex what cells and their modality reside in broadman’s area 3a?

A

Proprioceptors (muscle spindles) that are involved in body position

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34
Q

In the somatosensory cortex what cells and their modality reside in broadman’s area 3b?

A

Cutaneous cells like merkel cells, meissners corpuscles. Involved with touch (texture, sjhape, stimulus size)

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35
Q

In the somatosensory cortex what cells and their modality reside in broadman’s area 1?

A

Cutaneous cells (FA mechanoreceptors) and the same cells as in 3b like merkel and meissner corpuscles. These are involved with texture discrimination

36
Q

In the somatosensory cortex what cells and their modality reside in broadman’s area 2?

A

Joint afferents, golgi tendon organs, deep tissues and things in 3a/b.
This feels pressure and joint position and object perception (stereognosis)

37
Q

How is information in the somatosensory cortex organised?

A

Its layered and columnar and parts of the cortex beside eachother map the same parts of the body and are organised in parallel

38
Q

What is the primary function of the posterior parietal cortex?

A

To make sense of the information coming from the sensory cortex. Like when you feel a key that you know its a key

39
Q

What can occur from damage to the posterior parietal cortex?

A

Agnosia (inability to interpret sensations), asterognosia (inability to identify object by touch alone), hemispatial neglect syndrome (patient ignores everything in left visual field

40
Q

What is a Ia sensory afferent’s function in the muscle spindle?

A

Monitor the rate of contraction (dynamic response) and absolute length (static response) of a muscle

41
Q

Define a motor unit

A

All the muscle fibres innervated by a single alpha motor neurone

42
Q

Define a motor neurone pool

A

All the alpha motor neurones that then combine to innervate a single muscle

43
Q

Why does the frequency of AP acting on a muscle determine its contractile force?

A

As frequency incerases, contraction force increases due to summation of the AP causing sustained contractions

44
Q

What are the different muscle fibre types?

A

Slow twitch
Fast twitch IIa
Fast twitch IIx

45
Q

Which muscle fibre type is used most when long distance running

A

Type IIa

46
Q

Which muscle fibre type is used most when sitting?

A

Type I

47
Q

Which muscle fibre type is used most when weight lifting?

A

Type IIx

48
Q

The alpha motor neurones that innervate fast twitch muscle fibres are (larger/smaller) and (faster/slower) conducting than slow twitch muscle

A

The alpha motor neurones that innervate fast twitch muscle fibres are LARGER and FASTER conducting than slow twitch muscles

49
Q

The (smaller/larger) an alpha neurone the more likely it is to discharge an AP

A

The SMALLER an alpha neurone the more likely it is to discharge an AP

50
Q

Fine muscle movements have few/many fibres involved?

A

Few fibres- think delicate things you want less people working on it

51
Q

Why are lower motor neurones recruited in order of type I, IIa, IIx fibres in order to carry out a task?

A

Allows for fine control of muscle as it increases to the max force it can exert

52
Q

α-MNs cause contraction of (extrafusal/ intrafusal) muscle fibres

A

α-MNs that cause contraction of EXTRAfusal muscle fibres

53
Q

γ-NMs cause contraction of (intrafusal/extrafusal) fibres within muscle spindles

A

γ-NMs that cause contraction of INTRAfusal fibres within muscle spindles

54
Q

What is the function of the golgi tendon?

A

reverse myotatic reflex. This polysynaptic reflex involves, in sequence: activation of Ib afferents from the tendon organ → excitation of an inhibitory spinal interneurone → inhibition of the α-MN supplying the homonymous muscle → relaxation

Essentially to inhibit muscle activation

55
Q

What is the flexor reflex

A

When potentially dangerous stimuli then is contraction of the flexor muscles

56
Q

What are the motor tracts that are subdivisions of the lateral pathways?

A

Lateral corticospinal tract (pyramidal tract)

Rubrospinal tract

57
Q

Where are the cell bodies located in the rubrospinal tract?

A

In the red nucleus

58
Q

Where are the cell bodies of the medial and lateral vestibulospinal tract?

A

Medial vestibular nuclei within medulla

Lateral vestibular nuclei within pons

59
Q

What is the main function of the vestibulospinal tract? Is it sensory or motor?

A

Motor
The lateral tract does balance and posture for extensors of antigravity muscles

The medial tract does neck and back muscles for head movement

60
Q

What is the function of the tectospinal tract?

A

Control neck, upper trunk and shoulder in order to orientate the head and eyes to visual stimulus

61
Q

Where are the cell bodies located for the tectospinal tract?

A

In the midbrain with cell bodies in the superior colliculus

62
Q

Describe some of the features of nociceptive pain

A

It is an adaptive respone that is short lived and immediate

63
Q

Describe some of the features of inflammatory pain

A

Adaptive response that aids healing. It is long acting

64
Q

What is the effects of noxious stimuli long term?

A

Increased spinal excitability leading to hyperalgesia (increased pain sensitivity) and allodynia (things become painful that werent before)

65
Q

What types of stimuli do nociceptive A(delta) fibres pick up?

A

Mechanical and thermal

66
Q

What is the sensation felt by stimuli through a(delta) nociceptive fibres?

A

Lancinating, stabbing, pricking sensation.

67
Q

Give the pathway of cells a photon of light would transmit through before getting a signal to the brain

A

Photoreceptors (rods or cones in the retina)
Bipolar cells
Ganglion cells that then become the optic nerve

68
Q

Which of the photorecptor cells percieve colour vs light in darkness

A

Cones for colour

Rods for dim light conditions

69
Q

Describe the process of phototransduction

A

Light activates rhodopsin that then becomes oxidised to 11-cis-retinal. This activates phosphodiesterase that hydrolyses C-GMP become reduced C-GMP. This C-GMP is responsible for opening sodium gated channels that would usually depolarise the cell and cause glutamate release.
Hence darkness= +glutatmate

70
Q

What type of glutamate receptors are present in the bipolar cells in the OFF pathway? Produce more/less glutatmate in light?

A

Ionotropic gluatamate receptors

Less glutatmate in light

71
Q

What type of glutamate receptors are present in the bipolar cells in the ON pathway? Produce more/less glutatmate in light?

A

Metabotropic glutamate receptors

MORE glutamate in light

72
Q

What is the purpose of the center surround organisation of the cones in the retina?

A

To create contrast in the system to see boundaries between object

73
Q

What structure do sound waves pass through to enter the inner ear

A

Oval window

74
Q

What structural feature of the cochlea allows pitch to be descriminatory.

A

The basilar membrane that the organ of corti sits on is stiffer at the oval window end than the tip so it takes more energy to make the haircells at the oval window move that further up. Hence allowing pitch discrimination

75
Q

What is excitotoxicity and what can cause it?

A

When loss of energy provision, like in hypoxia, depolarisation of the neurone releases glutamate at the same time there is a reduction in the reuptake of glutamate causing over stimulation of the post synpatic neuron known as a glutatmate storm. This causes ca2+ accumulation in post N, leading to oxidative stress, mitochondria dysfunction and neuronal death

76
Q

Define ionic oedema

A

Where accumulation of na+ and cl- in interstitum from extravasation and it moving thorgh the BBB. Causing water to follow down the ion gradient leading to oedema

77
Q

Define vasogenic oedema

A

Break in BBB causing protein leak into the parenchymal space

78
Q

Is pneumococcus gram positive or negative

A

Gram positive

79
Q

Is neisseria meningitis gram positive or negative

A

Negative diplococci

80
Q

Is streptococcus pneumoniae gram positive or negative

A

Gram positive

81
Q

By what action do opioids cause analgesia?

A

Reducing nociceptive (pain) transmission to the dorsal horn of the spinal cord

By inhibiting opening of voltage activated calcium channels
Opening of K+ channels (cant depolarise)
Inhibiting adenylate cyclase

82
Q

What is the function of the periaqueductal grey (PAG), locus ceruleus and nucleus raphe magnus (NRM)

A

They produce NT that oppose nociceptive transmission e.g analgesia

Periaqueductal grey neurones stimulate the nucleus raphe magnus to signal other neurones to produce serotonin and endogenous opioids to suppress dorsal horn of spinal cord (pain receptor)

The locus ceruleus produces noradrenaline

83
Q

What type of receptor do opioids act on?

A

G-protein coupled opioid receptors

Receptor types mu, delta and kappa

84
Q

What group of people must you be careful prescribing opiods to?

A

Asthmatics

Can casue mast cell degranulation causing bronchospam

85
Q

What is the mechanism of action of NSAIDS?

A

Inhibit synthesis and accumulation of prostaglandins by COX-1 and COX-2

86
Q

What is kernigs sign? What condition might it indicate?

A

Positive when thigh and knee flexed at 90º and opposite straight leg becomes painful

May indicate subarachnoid haemorrhage or meningitis

87
Q

What is brudzinskis sign? What condition may it indicate

A

When patients neck flexed causes their hips and knees to also flex

Meningitis

Neurology Y3 JC (8 decks)

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