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Ultimate Neurosurgery > 2. Neurophysiology > Flashcards

2. Neurophysiology Flashcards

1
Q

How does Mg prevent excitotoxicity in brain?

A

Blocks Ca and NMDA channels

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2
Q

Most abundant excitatory neurotransmitter in the brain?

A

Glutamate

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3
Q

Cellular elements of BBB

A

Endothelial cells
Astrocyte endfeet
Pericyte

Capillary endotheilal cells connected by tight junctions

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4
Q

Platelet function after SAH?

A

Enhanced leading to increased platelet aggregation in cerebral microcirculation

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5
Q

Cerebral blood flow immediately after SAH?

A

Decreases

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6
Q

What is GPIIb/IIIa?

A

Platelet surface integrin - mediator of platelet aggregation

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7
Q

Dense granules of platelets?

A

5HT, ATP, PDGF

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8
Q

Disturbed balance of which peptide contributes to vasospasm?

A

Endothelin 1 (vasoconstriction) and nitric oxide (vasodilation)

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9
Q

Superoxide and hydrogen peroxide generates highly reactive hydroxyl radical - name?

A

Haber-Weiss reaction

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10
Q

Mechanism of steroid treatment in blunt spinal cord injury?

A

Local blood flow, inhibition of immunologic injury, and free radical-mediated lipid peroxidation and neuronal damage

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11
Q

What is S100B?

A

Calcium binding protein abundant in astrocytes - may be neuroprotective/neurotrophic

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12
Q

What is Windkessel phenomenon?

A

Cerebral vasculature expand and ability of CSF/venous blood to translocate to accomodate arterial pulsations and provide smooth capillary flow in the brain

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13
Q

Ischemic penumbra?

A

Region where cerebral blood flow reduction has passed threshold that leads to failure of electrical but not membrane function - structurally intact, but functionally disturbed

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14
Q

Role of infiltration with local anesthetic at beginning of a case?

A

Prevents activation of nociceptors during surgery and lessens need for analgesics

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15
Q

Structural unit of gap junction

A

Connexon allows direct electrical communication between cells

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16
Q

Functions of TGF beta?

A

Development/progression of brain tumors

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17
Q

What enzyme is inhibited by acetazolamide?

A

Carbonic anhydrase

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18
Q

Difference between bioactive Guglielmi detachable coil (GDC) and platinum GDC?

A

Bioactive coil accelerates clot and promotes development of mature connective tissue

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19
Q

Mutation in Crouzon syndrome

A

Fibroblast growth factor receptor 2 - absence of ligand binding - premature fusion of cranial sutures leading to abnormal cranium shape, restricted growth and increased ICP

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20
Q

Baclofen mechanism?

A

GABA agonist

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21
Q

Hyparrhythmia

A

Chaotic, high amplitude EEG (Infantile spasm)

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22
Q

Subsidence?

A

Loss of vertebral column heigh with aging

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23
Q

Genetic defect in Gorlin syndrome?

A

autosomal dominant

Mutation of PTCH gene that predisposes to neoplasias and widespread congenital malformations

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24
Q

Water channel proteins of the brain?

A

Aquaporins

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25
Q

Most common agent for pharmacologic dilatation of vasospastic cerebral vessels?

A

Papaverine hydrochloride - endothelium-independent smooth muscle relaxant

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26
Q

How do intervertebral disks receive nutrition?

A

Passive diffusion from capillary beds in subchondral endplate region of vertebral body

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27
Q

Composition of PEEK cage

A

Polyetheretherketone (PEEK) spacers - strong polymer that withstand compressive load of vertebral column

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28
Q

Common areas of leptomeningeal dissemination for tumors

A

Basilar cisterns, sylvian fissure, cauda equina (gravity and slower rate of CSF)

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29
Q

Resting membrane potential in myelinated pheripheral nerves? in soma?

A

~ 90 mV and ~ 65 mV

Determined by K+ (100x more permeable than Na+)

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30
Q

Botulinum toxin mechanism

A

Inhibit release of ACh from presynaptic terminal

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31
Q

Where do AP in neurons start?

A 
Axon hillock
(7x more voltage-gated Na channels there) - depolarize much easier than soma
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32
Q

Factors that determine velocity of propagation of AP

A

Inverse of internal resistance
Inverse of membrane capacitance
Proportionate by transmembrane resistance
Myelin increases resistance/decreases capacitance

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33
Q

Conduction velocity of small unmyelinated and large myelinated nerves?

A

0.5 m/s

120 m/s

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34
Q

How does hypocalcemia lead to tetany?

A

Less Ca2+ in interstitial fluid, Na+ open sooner - lower threshold of membrane depolarization

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35
Q

How does hyperventilation lead to seizure?

A

Respiratory alkalosis (increase pH) -> increase membrane excitability and induce seizure

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36
Q

How big is a synaptic cleft

A

20-30nm

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37
Q

What is unique about synthesis of neurotransmitter NE?

A

Synthesized within vesicle by dopamine alpha-hydroxylase (dopamine to NE)

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38
Q

2 types of ACh receptors

A
  1. Nicotinic (NMJ, preganglionic endings of both sym and parasym fibers)
  2. Muscarinic - postgan parasympathetic and postganglionic sympathetic of sweat glands
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39
Q

2 main inhibitory neurotransmitters of CNS

A

GABA and glycine

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40
Q

GABA receptor mechanism

A

5 subunit with central Cl- channel - causes hyperpolarization

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41
Q

Which body part has largest area of representation in primary somatosensory area?

42
Q

What is hyperalgia

A

Increased sensitivity to pain

increased sensitivity of receptors, facilitation in spinal cord or thalamic lesion

43
Q

Thalamic pain syndrome?

A

Dejerine-Roussy syndrome

Posteroventral thalamic stroke and abnl facilitation of medial thalamic nucleus.

44
Q

Hangover pain?

A

Chemical irritation to meninges

45
Q

What causes night blindness?

A

Severe deficiency in vitamin A - decrease amount of photosensitive pigment to detect decreased light.
Tx: IV infusion of vitamin A

46
Q

Where in retina has only cones?

A

Fovea (center of macula)

47
Q

What is scotoma?

A

Area of decreased vision surrounded by preserved vision in visual field

48
Q

Where on tongue is salty taste detected?

49
Q

1st order neuron of olfactory pathway located

A

Olfactory cells in olfactory epithelium.

These bipolar cells send axons through cribiform plate to olfactory bulb.

50
Q

Which protein is involved in retrograde and fast anterograde transport?

A

Kinesis and dynein

51
Q

What does muscle spindle detect?

A

Length and velocity of change in length of muscle, stimulated by stretching.
Increases firing with muscle stretch and decreases firing with muscle contraction.

52
Q

What carries info from muscle spindles and golgi tendon organ

A

Dorsal spinocerebellar tracts

53
Q

What cause decerebrate rigidity

A

Lesion between pons and midbrain - blocks input to medullary reticular formation from red nucleus/BG/cortex - unopposed antigravity muscle tone that is stimulated by lateral vestibular nucleus and pontine reticular nucleus.

54
Q

In vestibular system, what is sensory orga of utricle and saccule?

A

Macula that contains hair cells that have cilia embedded in gelatinous layer containing calcium carbonate otoliths.

55
Q

What is the sensory organ of semicircular canals?

A

Crista ampullaris - which has hair cells with cilia that project into cupula (gel cup)

56
Q

In the vestibular system, the utricle has its macula in which plane?

A

Utricle has macula on horizontal plane (sense acceleration direction when upright).
Saccule has macula in vertical plane (acceleration in horizontal or supine).

57
Q

Mechanism of action of nitrosoureas

A

Alkylating agents for malignant brain tumors - cause crosslinks of DNA and breakage

58
Q

Mechanism of temozolomide

A

Attach methyl group to DNA base guainine - prevents proper DNA replication

59
Q

What is MGMT (O6-methylguanine-DNA methyltransferase)?

A

DNA repair enzyme that remove methyl group placed by temozolomide (low levels respond better to temozolomide)

60
Q

EEG during REM sleep?

A

Beta waves (same as awake)

61
Q

Effect of sleep deprivation on autonomic system

A

Increase sympathetic and decrease parasympathetic

62
Q

Hering-Breuer inflation reflex

A

Over distension of lungs - stretch receptors in bronchi/bronchioles through vagus nerve inhibits dorsal resp nucleus in dorsal medulla to stop inspiration

63
Q

Atonic bladder

A

Flaccid bladder - fails to empty properly, causing overflow incontinence - overaccumulation cause micturition reflex.

64
Q

What causes vasogenic edema?

A

Increased BBB permeability (extracellular) - caused by vessel damage and inflammation.

65
Q

What causes cytotoxic edema?

A

Impaired Na/K pump in ischemia. Water/electrolytes accumulate in cells (intracellular type edema)

66
Q

Ischemic optic neuropathy - visual fields?

A

Painless monocular blindness by occlusion of central retinal artery - altitudinal field deficit.

67
Q

Mechanism of clopidogrel (plavix)?

A

Selective inhibitor of platelet aggregation - irreversibly to ADP receptor on platelet cell membranes - block glycoprotein 2b/3a pathway.
Stop at least 1 week before surgery.

68
Q

Antidote for arsenic poisoning

A

Dimercaprol (BAL) - British Anti-Lewisite)

69
Q

What medications increase levels of dilantin?

A

Cimetidine, coumadin, INH, sulfa drugs

70
Q

Red man’s syndrome

A

Rapid infusion of vancomycin - histamine release producing facial flushing, pruritis, hypotension

71
Q

Effect of fentanyl on cerebral blood flow?

72
Q

Effect of ketamine on cerebral blood flow?

73
Q

Causes of hypercortisolism (Cushing syndrome)

A

Iatrogenic, ACTH-secreting pituitary adenoma, adrenal tumor, ectopic ACTH (pulmonary oat cell tumor or carcinoid)

74
Q

Cause of febrile nonhemolytic transfusion reactions

A

Antibodies to donor WBC (treat with acetaminophen)

75
Q

Acute hemolytic transfusion reaction

A

Within minutes - fever, dyspnea, chest pain, hypotension. Can have DIC and multiple organ failure.

76
Q

1 unit of platelets increases platelet count by how much?

A

5000-10,000 and lasts for 1 week

77
Q

Malignant hyperthermia tx

A

Dantrolene

78
Q

Ideomotor apraxia

A

Cannot perform complex motor task but aware of task

Lesion of supramarginal gyrus of dominant parietal lobe

79
Q

Factors causing O2 right shift

A

Decrease O2 affinity

Increase H+, CO2, temp, 2-3 DPG

80
Q

Types of sensory axons

A 
Group 1 (A alpha)
Group 2 (A beta, A gamma)
Group 3 (A delta)
81
Q

Group 1 sensory axons

A

A alpha - largest, fastest conducting

Afferents of muscle spindles, 1b fibers - afferents from Golgi tendon organs

82
Q

Group 2 sensory axons

A

A beta and gamma - slower

Muscle spindles and cutaneous touch/pressure

83
Q

Group 3 sensory axons

A

A delta - smaller and slower; carry temp, light touch, sharp pain

84
Q

Group 4 sensory axons

A

C fibers - slowest fibers and mediate temp and burning pain.

85
Q

Basic types of striated muscle fibers

A

3 Basic

  1. Type I
  2. Type IIa
  3. Type IIb
86
Q

Type I muscle fibers

A

slow-twitch or red fibers; lots of mitochondria. Prolonged contraction without fatigue

87
Q

Type IIA muscle fibers

A

fast fatigue-resistant - can maintain for several minutes

88
Q

Type IIB muscle fibers

A

fast fatigable fibers - lots of glycogen and anaerobic metabolism. Cannot sustain contraction forces from rapid accumulation of lactic acid

89
Q

Mechanism of TCA

A

Block reuptake of 5HT and NE

90
Q

Mechanism of cholera and pertusis toxin

A

stimulate cAMP inside cell
Cholera stimulates Gs
Pertusis inactivates Gi

91
Q

NO generated from which amino acid?

A

Arginine (from nitric oxide synthase)

92
Q

Sarcomere - which region gets shorter during contraction

A

H zone and I band

93
Q

Receptive fields of bipolar cells vs neurons of primary visual cortex

A

Bipolar cells - circular receptive field

Neurons - rectangular receptive fields

94
Q

Which stage of sleep do night terrors occur?

A

Stage 3-4 (deep sleep)

95
Q

Too rapid correction of hyponatremia

A

Central ponteine myelinolysis (no more than 0.5mEq/L/h)

Dissolution of myelin sheaths of fibers within central aspect of basis pontis - spastic quadriparesis, pseudobulbar palsy, acute MS changes

96
Q

What should be prescribed for patient with coagulopathy associated with coumadin?

A

Vitamin K and FFP

97
Q

What is Apo E gene?

A

Apo E made in astrocytes for lipid transport in brain

E4 assoc. with age-related cognitive impairment.

98
Q

How is achondroplasia inherited?

A

Autosomal dominant, but may be sporadic.

Mutation in transmembrane region of FGFR3 (neg control of bone formation)

99
Q

What is CRP?

A

Acute phase reactant in response to injury or infection, made in liver or adipocytes.

Highest POD2 and subsides at POD5

100
Q

What does STIR stands for in MRI?

A

Short tau inversion recovery

101
Q

What age do K-complexes begin to appear in sleep cycle?

102
Q

When in sleep cycle do K-complexes appear?

A

Stage 2 of NREM

Ultimate Neurosurgery (16 decks)

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