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NS Rounds by Dorka > 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

Areas of brain without a blood-brain barrier:
Pituitary gland.
Median eminence.
Area postrema.
Preoptic recess.
Paraphysis.
Pineal gland.
Endothelium of choroid plexus.

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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)

Hypsarrhythmia is a classical multifocal electroencephalographic finding in patients of infantile spasm and related epileptic syndromes of early childhood including West syndrome and Otahara syndrome. It usually presents in early infancy and persists up to the age of two years, after which it usually resolves

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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?

A

The lips

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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?

A

Tip

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?

A

Decreases

72
Q

Effect of ketamine on cerebral blood flow?

A

Increases

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?

A

6 months

102
Q

When in sleep cycle do K-complexes appear?

A

Stage 2 of NREM

103
Q

Where are no BBB?

A

circumventricular organs
Thus, the circumventricular organs have no blood-brain barrier. Some of these organs (the OVLT, the subfornical organ, and the area postrema) have associated neurons that project to the hypothalamic and other visceral structures.

NS Rounds by Dorka (10 decks)

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