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Clin Med - Neuro > Neurophys Review Part 1 > Flashcards

Neurophys Review Part 1 Flashcards

1
Q

What are the main differences between electrical and chemical synapses?

A
  • Electrical synapses propagate a signal using gap junctions (connexon) as opposed to NTs.
  • Electrical are comparatively rare
  • electrical are dendro-dendritic (mostly)
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2
Q

What passes through gap junctions?

A

All ions

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3
Q

What is the function of the pre-synaptic process (axon)?

A

Provides neurotransmitter

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4
Q

What is the function of the post-synpatic process

A

To translate the neurotransmiatter into a useful signal (depolarization)

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5
Q

What is the role of astrocytes?

A

Astrocytes are a type of glia that provide metabolic support to neurons and may modulate synaptic function

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6
Q

What are the proteins that form the SNARE complex?

A
  1. synaptobrevin
  2. syntaxin
  3. synaptotagmin
  4. SNAP-25
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7
Q

Give the sequence of events of the vesicle docking

and synaptic transmission.

A
  1. vesicle docks
  2. entering Ca++ binds to synaptotagmin
  3. SNARE complexes form to pull PS membrane to vesicle membrane
  4. Ca++ bound to synaptotagamin catalyzes membrane fusion by binding to SNARES/plasma membrane
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8
Q

What chemical is used clinically and interferes with SNARE formation?

A

Botulinim toxin (Botox)

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9
Q

Each neuron releases how many neurotransmitters?

A

ONE

*but some also release a peptide in addition to the primary NT

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10
Q

What are the amino acid NTs?

A

glutamate

aspartate

GABA

glycine

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11
Q

What are the catecholamine neurotransmitters?

A

dopamine

norepinephrine

epinephrine

*part of larger biogenic amine class

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12
Q

What channel is defective in inherited Long QT Syndrome?

A

K+ Channel

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13
Q

What channel type is defective in cystic fibrosis?

A

Cl-

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14
Q

What effect does GABA have on the post-synaptic cell?

A

hyperpolarizes it

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15
Q

How do GABAb receptors modulate Ca++?

A

They are located on the pre-synaptic terminals and when activated by NT, cause reduced Ca++ influx, thereby reducing the amount of NT released.

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16
Q

What receptor type will additionally allow Ca++ into the cell under the right conditions?

A

NMDA

17
Q

Memantine is a drug used for _______ patients and acts by antagonizing ________receptors.

A

Alzheimer’s; NMDA

*reduces glu/Ca2+ in cell

**works in about 1/3 of patients

18
Q

What are the 3 major factors responsible for the uneven distribution of ions across the neuronal membrane?

A
  1. selective permeability
  2. large organic anions within the cytoplasm
  3. ion pumps (Na+/K+ ATPase)
19
Q

What is the ratio of the Na+/K+ ATPase?

A

3:2

*net outward current causes small hyperpolarization

20
Q

What is the reversal potential for K+?

A

about -85 mV

21
Q

What is the reversal potential for Na+

A

about +57 mV

22
Q

What channels are mutated in Epilepsy ?

A

K+ and nicotinic

23
Q

What channels are mutated in Hyperekplexia?

A

Glycine

24
Q

What is the mechanism of action of lidocaine?

A

Blocks Na+ channels and has some specificity for inhibitory neurons (blocks pain neurons)

25
Q

What channels open first in the action potential?

A

voltage-gated Na+

26
Q

What is the “information code” transmitted from neuron to neuron?

A

the pattern of action potentials

27
Q

What are the spaces between myelin cells on a neuron called?

A

Nodes of ranvier

28
Q

Conduction along a myelinated axon differs from an unmyelinated axon in what respect?

A

It is saltatory - it “jumps” from node to node

29
Q

If an injected current does not reach threshold for a neuron, what happens?

A

Nothing

(In other words, an EPSP must reach threshold to get an action potential)

30
Q

What is hyperkalemia?

A

elevated serum K+ usually caused by kidney dysfunction

*leads to depolarization of membrane

31
Q

What happens during hyperkalemia that causes irregular cardiac rhythms and skeletal muscle weakness?

A

The membrane of neurons depolarize slowly (seconds) or have sustained depolarization, leading to so many Na+ channels being deactivated, no AP can occur

32
Q

What gate opens first on Na+ voltage-gated channels?

A

M gate

depolarizing phase

33
Q

What gate closes to de-activate Na+ voltage channels and when?

A

H gate

at the top of the depolarizing phase

34
Q

When does the K+ voltage-gated channel open?

A

at the top of the depolarizing phase (n gate)

Clin Med - Neuro (17 decks)

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