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Head and Neck > Nervous Physiology > Flashcards

Nervous Physiology Flashcards

1
Q

Function of astrocytes

A

Form the blood-brain barrier

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2
Q

Function of microglia

A

Perform a phagocytic role in the CNS

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3
Q

Function of oligodendroglia

A

Produce myelin

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4
Q

Contents of grey matter

A

Neuronal cell bodies

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5
Q

Contents of white matter

A

Axons of the neurons

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6
Q

What proportion of cardiac output does the brain receive

A

10-15%

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7
Q

Describe myogenic autoregulation of cerebral blood flow

A

Cerebral blood vessels constrict or dilate to maintain adequate cerebral perfusion

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8
Q

What is the range of Cerebral perfusion pressure that myogenic autoregulation can compensate for

A

50-150mmHg

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9
Q

What factors inhibit myogenic autoregulation

A
  • Hypoxia
  • Ischaemia
  • Trauma
  • Cerebral haemorrhage
  • Tumour
  • Infection
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10
Q

Describe metabolic autoregulation of cerebral blood flow

A

Areas of the brain with increased activity results in a decrease in PaO2 and increase in PaCO2 and H+. These changes result in vasodilatation.

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11
Q

What change in CO2 causes vasodilatation of the cerebral blood vessels

A

Hypercapnia

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12
Q

What is the total volume of CSF

A

130-150ml

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13
Q

What is the distribution of CSF

A
  • 40ml in the ventricles

- 100ml surrounds the spinal cord

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14
Q

What is the rate of CSF production

A

500ml/day

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15
Q

What is the normal CSF pressure

A

0.5-1kPa (7mmHg)

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16
Q

Where is CSF produced

A

Choroid plexus

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17
Q

Outline how CSF flows from the 4th ventricle to the subarachnoid space

A
  • Laterally via foramen of Luschka

- Midline bia foramen of Magendie

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18
Q

How is CSF absorbed into the venous circulation

A

Via arachnoid villi which drain into the venous sinuses

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19
Q

How does SAH cause hydrocephalus

A

Arachnoid villi become blocked with blood causing rise in pressure

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20
Q

What are the two functions of CSF

A
  • Hydraulic cushion

- Stable ionic environment for cerebral function

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21
Q

What type of molecules are able to travel freely across the BBB

A

Lipid-soluble molecules (CO2, O2, alcohol, anaesthetics, hormones)

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22
Q

Describe the structure of the BBB

A
  • End-feet of astrocytes cover the basement membrane

- Tight cell-to-cell capillaries in the endothelium

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23
Q

Where does the BBB contain fenestrated capillaries

A
  • 3rd and 4th ventricles
  • Posterior lobe of pituitary
  • Hypothalamus
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24
Q

Which part of the brain provides the capacity for consciousness

A

Brainstem

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25
Q

Which part of the brain provides the content of consciousness

A

Cerebral hemispheres

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26
Q

List the preconditions for diagnosis of brainstem death

A
  1. Patient must be in a coma
  2. Must be a known cause for coma
  3. Cause must be irreversible
  4. Ventilator dependent
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27
Q

List the exclusion criteria for diagnosis of brainstem death

A
  1. No residual drug effects
  2. Core body temperature >35
  3. No circulatory, metabolic, or endocrine abnormalities that may contribute to coma
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28
Q

List the seven areas tested to diagnose brainstem death

A
  1. No pupillary response to light
  2. Absent corneal reflex
  3. No motor response in the cranial nerve distribution to stimuli in any somatic area
  4. No gag reflex
  5. No cough reflex
  6. No vestibulo-cochlear reflex
  7. Apnoea test
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29
Q

Which cranial nerves do the cough and gag reflexes test

A
  • Vagus

- Glossopharyngeal

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30
Q

When is the time of brainstem death legally defined

A

The time the FIRST set of tests are completed

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31
Q

Outline the Monroe-Kellie hypothesis

A

ICP will increase if volume of any one component (brain, CSF, blood) increases, and this increase can only be compensated by a reduction in one of the other components

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32
Q

What volume of SOL can reduction in blood and CSF accommodate

A

100-150ml

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33
Q

Describe transtentorial herniation

A
  • Lesion lies within one hemisphere

- Medial part of temporal lobe herniates over the tentorium cerebelli

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34
Q

Describe tonsillar herniation

A
  • Causes by lesion in the posterior fossa
  • Cerebellum pushes down through foramen magnum
  • Compresses the medulla
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35
Q

Describe subfalcial herniation

A
  • Caused by lesion in one hemisphere

- Leads to herniation of the cingulate gyrus under falx cerebri

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36
Q

Describe diencephalic herniation

A
  • Generalised brain swelling
  • Midbrain herniates through tentorium
  • A.K.A. Coning
37
Q

Signs of Cushing’s response

A
  • Reduced respiratory rate
  • Bradycardia
  • Hypertension
38
Q

List the clinical signs of transtentorial herniation

A
  • Oculomotor nerve compression (ipsilateral pupil dilatation)
  • Cerebral peduncles (contralateral hemiparesis)
  • Posterior cerebral artery (cortical blindness)
  • Cerebral aqueduct (hydrocephalus)
39
Q

Which types of herniation cause anterior cerebral artery infarction

A

Subfalcial

40
Q

What are the symptoms of ITU syndrome

A

Pain, fear and sleep deprivation cause visual and auditory hallucinations

41
Q

What two factors dictate the speed of action potential transmission

A
  1. Axon diameter (greater diameter = greater velocity)

2. Myelination

42
Q

Role of C-fibres

A

Slow mechanothermal pain conduction

43
Q

Role of B-fibres

A

Autonomic conduction

44
Q

Role of A-alpha fibres

A

Motor and proprioception conduction

45
Q

Role of A-beta fibres

A

Touch and pressure conduction

46
Q

Role of A-gamma fibres

A

Muscle contraction (muscle spindle fibres)

47
Q

Role of A-delta fibres

A

Sharp mechanothermal pain conduction

48
Q

What are the 4 classes of pain

A
  1. Nociceptive (somatic and visceral)
  2. Referred
  3. Neuropathic
  4. Psychogenic
49
Q

Where do A-delta and C fibres synapse in the spinal cord

A

Lamina 1 and 3 in the dorsal horn

50
Q

Where do the descending inputs that modulate pain originate from

A

Pons and mid-brain

51
Q

Role of the dorsal column-medial lemniscal pathway

A

Carries sensory modalities of fine touch, vibration, and proprioception

52
Q

What 3 groups of neurones make up the DCML

A
  • 1st order
  • 2nd order
  • 3rd order
53
Q

What is the role of DCML 1st order neurones

A

Carry sensory information regarding fine touch, vibration, and proprioception from the peripheral nerves to the medulla oblongata

54
Q

Outline the two different pathways that DCML 1st order neurones take

A
  • Upper limb (T6 and above) travel in the fasciculus cuneatus (lateral part)
  • Lower limb (below T6) travel in the fasciculus gracilis (medial part)
55
Q

What is the role of DCML 2nd order neurones

A
  • Begin in the cuneate neucleus or gracilis of the medulla oblongata
  • Connect these to the third order neurones in the thalamus
56
Q

What is the role of DCML 3rd order neurones

A

Transmit the sensory signals from the thalamus to the ipsilateral primary sensory cortex of the brain (ascend from the ventral posterolateral nucleus and through the internal capsule)

57
Q

Role of the anterior spinothalamic tract

A

Carries the sensory modalities of crude touch and pressure

58
Q

Role of the lateral spinothalamic tract

A

Carries the sensory modalities of pain and temperature

59
Q

What is the role of the anterolateral system’s 1st order neurones

A
  • Arise from the sensory receptors in the periphery
  • Enter spinal cord and ascend 1-2 levels
  • Synapse at the tip of the dorsal horn (=substantia gelatinosa)
60
Q

What is the role of the anterolateral system’s 2nd order neurones

A

Carry sensory information from the substantia gelatinosa to the thalamus via either the anterior or lateral tracts

61
Q

What is the function of the pyramidal tracts

A

Responsible for the voluntary control of the musculature of the body and face

62
Q

What is the function of the corticospinal tracts

A

Supplies the musculature of the body

63
Q

What is the function of the corticobulbar tracts

A

Supplies the musculature of the head and neck

64
Q

Where do the corticospinal tracts synapse with their corresponding LMNs

A

Ventral horns

65
Q

List the 4 stages of pain transmission

A
  1. Transduction
  2. Transmission
  3. Modulation
  4. Perception
66
Q

Give an example of drugs that affect the transduction stage of pain transmission

A

Paracetamol/NSAIDs - inhibit prostaglandins and thus prevent the sensitisation of nociceptive receptors

67
Q

Give and example of drugs that affect the transmission stage of pain transmission

A
  • Local anaesthetics prevent the conduction of action potentials down A-gamma and C fibres
  • TENS
68
Q

Which stage of pain transmission of opioids affect

A

Modulation

69
Q

Where are the preganglionic neurones of the sympathetic nervous system located

A

Lateral horn of the spinal grey matter

70
Q

Where do sympathetic preganglionic neurones leave the spinal cord to join their spinal nerve

A

Ventral root

71
Q

Where are sympathetic postganglionic cell bodies located

A
  • Sympathetic chain OR

- Named plexus along the aorta e.g. Coeliac

72
Q

How are spinal nerves connected to the sympathetic chain

A
  • Lateral white ramus (myelinated)

- Medial grey ramus (unmyelinated)

73
Q

What is the neurotransmitter of the sympathetic nervous system

A

Noradrenaline (except sweat glands which are innervated by cholinergic fibres)

74
Q

Where are the preganglionic neurones of the parasympathetic nervous system located

A
  • Brainstem = cranial nerve nuclei

- Pelvis = S2-4 spinal roots

75
Q

List the 5 ganglia that distribute parasympathetic outputs

A
  1. Ciliary ganglion (oculomotor)
  2. Sphenopalatine ganglion (facial)
  3. Submandibular ganglion (facial)
  4. Otic ganglion (glossopharygneal)
  5. Pelvic ganglion (S2-4 -> pelvic splanchnic nerves)
76
Q

What is the neurotransmitter of the parasympathetic nervous system

A

Acetylcholine

77
Q

Where is the motor cortex located

A

Dorsal part of precentral gyrus

78
Q

Define a reflex

A

Involuntary, stereotyped response as a result of a sensory stimulus

79
Q

What are the components of a reflex pathway

A
  • Afferent neuron that conveys the impulse
    from a sensory receptor
  • Efferent neuron that runs from the brain to the effector organ i.e. muscle
80
Q

What is the sensory organ in a muscle stretch reflex

A

Muscle spindle consisting of intrafusal muscle fibres that lie in parallel with skeletal muscle fibres

81
Q

Biceps reflex root

A

C5-6

82
Q

Brachioradialis reflex root

A

C5-6

83
Q

Triceps reflex root

A

C6-7

84
Q

Quadriceps reflex root

A

L3-4

85
Q

Achilles tendon reflex root

A

S1-2

86
Q

List the 4 descending motor inputs from the brainstem (extrapyramidal tracts)

A
  1. Rubrospinal tract
  2. Tectospinal tract
  3. Vestibulospinal tract
  4. Reticulospinal tract
87
Q

What is the function of the basal ganglia

A

Initiation of movement

88
Q

When does the cranial neuropore close

A

25 days gestation (caudal pore closes 2 days after)

89
Q

What is the approximate intracranial volume

A

1550ml

Head and Neck (7 decks)

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