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MRCS > Neuro Physiology > Flashcards

Neuro Physiology Flashcards

1
Q

Autoregulation of CBF

A

Myogenic
Local
Neural

Constant between CPP of 60-160 mmHg

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2
Q

Hyperbaric oxygen and cerebral blood flow

A

Although PaO2 has a far lesser effect on CBF vs PCO2

Hyperbaric oxygen can reduce cerebral blood flow by ~20%

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3
Q

Total volume CSF

A

130-150 ml

100ml spinal cord
40ml in ventricles

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4
Q

Normal CSF pressure

A

0.5-1 kPa

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5
Q

Production of CSF

A

Choroid plexus in lateral, third and fourth ventricles

L, 3rd and 4th

~500ml / day

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6
Q

Foramin of Luschka

A

Lateral

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7
Q

Foramin of Magendie

A

Medial

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8
Q

Areas in which blood-brain barrier is permeable - fenestrated endothelium

A

Third and fourth ventricles

  • Chemoreceptor trigger zone at floor of fourth ventricle
  • Angiotensin II passes to the vasomotor centre in this region to increase sympathetic outflow and causes vasoconstriction of peripheral vessels

Posterior pituitary
-Allows production of ADH and oxytocin into circulation

Hypothalamus
-this allows the release of releasing or inhibitory hormones into the portal–hypophyseal tract (to anterior pituitary)

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9
Q

Consequences of rising ICP

A

Hydrocephalus
-Seen in posterior fossa lesions due to compression of aqueduct

Ischaemia
-Rising ICP reduces CPP and therefore CBF

Herniation
-Compression of brain via herniation

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10
Q

Pupillary dilatation and raised ICP

A

–> oculomotor nerve compression

= Transtentorial herniation

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11
Q

Cortical blindness and raised ICP

A

= Transtentorial herniation

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12
Q

Resting membrane potential of axon

A

negative 70mV

-70mV

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13
Q

Depolarisation

A

Axon membrane potential goes from -70 –> +50mV

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14
Q

Absolute and relative refraction

A

During action potential = absolute refraction

During repolarisation = relative refraction, larger stimulus can cause another action potential

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15
Q

Mechanism of depolarisation and repolarisation

A

The Na+ channel activates much faster than the K+
channel.

This explains the rapid influx of Na+; the
channel also closes much faster; the K+ channel
remains open over a longer period than the Na+
channel and is responsible for repolarisation as K+
is released and the membrane potential falls back
to its negative value

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16
Q

Nodes of Ranvier

A

Gaps in between myelinated axons

Points of depolarisation

Increases speed of transmission as between nodes the axon depolarises quickly and entirely

= saltatory conduction

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17
Q

Aα axons

A

Motor

Propioception

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18
Q

Aβ axons

A

Touch

Pressure

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19
Q

Aγ axons

A

Muscle spindles

20
Q

Aδ axons

A

Pain

myelinated version of pain fibres

21
Q

C-fibres axons

A

Unmyelinated pain neurons

22
Q

B axons

A

Autonomic

23
Q

Breakdown of amine neurotransmitters

A

Monoamine oxidase: breaks down neurotransmitter taken up at PRE-synaptic neuron

Catechol-O-methyl transferase breaks down catecholamine in post-synaptic neuron

24
Q

Glutamate + Aspartate

A

Excitatory

25
Q

Glycerol

A

Inhibitory

26
Q

Substance P

A

Pain transmission

27
Q

Kehr’s sign

A

Referred pain

Left-sided diaphragmatic irritation and left shoulder tip pain

28
Q

Gate control theory

Modulation of pain

A

Descending
Periaqueductal grey matter and raphe magnus –> releasing serotonin

Locus coeruleus –> noradrenaline

Local
Naturally occurring enkephalins and endorphins at point of transmission synapse in spinal cord

29
Q

Proteins on actin filament

A

Actin: double strand helix

Tropomyosin: lies in groove between double-stranded helix of actin

Troponin: regular arrangement along actin filament

  • Attached to both actin and tropomysin
  • Has binding sites for Ca2+ and is involved in the regulation of contraction.
  • Troponin and tropomyosin block the myosin-binding site on actin.

Rise in calcium allows removal and binding of myosin

30
Q

Proteins on myosin

A

Head section has binding site for ATP
–> allows release of head from actin filament

Structure: head + long tail

31
Q

Troponin

A
  • Attached to both actin and tropomysin
  • Has binding sites for Ca2+ and is involved in the regulation of contraction.
  • Troponin and tropomyosin block the myosin-binding site on actin.

Rise in calcium allows removal and binding of myosin

32
Q

Tropomyosin

A

Tropomyosin: lies in groove between double-stranded helix of actin

Rise in calcium allows removal and binding of myosin

33
Q

Type I muscle fibre

A

Slow / postural

34
Q

Type IIa muscle fibre

A

Type IIa or fast oxidative fibres

e.g. calf muscles

They rely on aerobic metabolism and contain myoglobin; they have moderate resistance to fatigue

35
Q

Type IIb muscle fibre

A

Type IIb or fast glycolytic fibres

e.g. extraocular muscle

Do not contain myoglobin and thus appear white

They contain a large amount of glycogen and rely on anaerobic metabolism.

36
Q

Intrafusal muscle fibres

A

Respond to stretch

“stretch sensory” receptor for stretch-contraction reflex arc

37
Q

Precentral gyrus

A

Motor cortex

Frontal lobe immediately anterior to central sulcus

38
Q

Corticobulbar tracts

A

Motor supply to cranial nerve

39
Q

Corticospinal tracts

A

Supply spinal motor neurons

–> voluntary movement

40
Q

Four descending motor inputs from brainstem

A

Rubrospinal tract: red nucleus

Tectospinal tract: superior colliculus of midbrain

Vestibulospinal tract: vestibular nuclei

Reticulospinal tracts: pons and medulla

41
Q

Rubrospinal tract

A

Descending motor input from the brainstem

  • Red nucleus
  • Primarily innervates distal limb muscles
42
Q

Tectospinal tract

A

Descending motor input from brainstem

  • Superior colliculus of midbrain
  • Receives inputs from the visual cortex
  • Controls reflex activity in response to visual stimuli
43
Q

Vestibulospinal tract

A

Descending motor input from brainstem

  • Vestibular nuclei
  • Supplies muscles of the ipsilateral side of the body.
  • Innervates muscles concerned with balance and posture in response to inputs from the vestibular apparatus
44
Q

Reticulospinal tract

A

Descending motor input from brainstem

  • Arises from pons and medulla
  • Supply muscles on the ipsilateral side of the body and are important in maintaining posture and muscle tone
45
Q

Cerebellum

A

No descending tracts

Modulation of motor coordination directly into motor cortex in precentral gyrus

Receives information from:

  • Vestibular apparatus
  • Visual system
  • Corticospinal tracts
  • Peripheral proprioceptors

MRCS (24 decks)

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