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Flashcards in Neurophysiology Deck (20)
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1

Parts of neuron

Dendrites, axons, soma, synaptic terminal

2

Neuron types: type, examples, describe

Multipolar: motor neurons, interneurons
-1 axon, many dendrites
Bipolar: special senses neurons
-1 axon process, one drenditic process
Pseudounipolar: somatic, visceral sensory neurons
-1 process but brances

3

Graded membrane potentials - where?

-graded in amplitude, proportional to intensity (stronger stimulus fires STRONGER signal)
-in dendrites and body
-sensory neuron: receptor potentials (Stimulus > receptor activated > Na+ influx in sensory neuron > potential that is graded
-synaptic neurons: synaptic potentials

4

Action Potential - where? characteristics?

-fixed amplitude
-in axons
-used for propagation
-frequency proportional to intensity: stronger stimulus fires MORE
-communication over long distance bt neurons
-all or none
-spike initiation zone
-unidirectional (b/c of refractory periods)

5

Axonal transport: anterogrde vs retrograde

-Fast anterograde - soma > synapse. transport NTs, macomolecules in vesicles long KINESIN
-Slow anterograde - diffusion of cytosolic proteins
-Fast retrogrde - nerve terminals > soma. along DYNEIN. surplus materials, endocytocized materials, infections

6

What does dendrites have that axons don't

-multiple branching
-RIBOSOMES!
-graded potentials

7

resting membrane potentil

-70mV due to higher K+ permeability > leaks OUT = inside more negative then outside
-maintain by Na/K/ATPase: pumps K+ in and Na+ out

8

Relationship bt receptor potential and APs

-RPs in large > initiate APs
-

9

Factors for conduction velocity

-increase size (decrease resistance)
-myelination (decrease capacitance)
-distance

10

Myelination

-lipid insulator > faster AP conduction
-PNS: Schwann cells, CNS: oligodendrocytes
-Nodes of Ranvier: AP leap bt nodes = saltatory conduction

11

Demyelination
-diseases?

> Conduction block
-AP can't reach next patch of N channels
ex: MS - demylenation of central axons
Guillin-Barre: peripheral

12

Local anesthetics and pain
-block what?
-ex?

-blocks Na+ chnnels from inside. no Na+ influx > no AP
-targets small-diameter, unmyelinated fibres because can access more Na+ channels to block
ex: cocain, lidocaine

13

Why use NCS and EMG?

1. localize lesion
2. distinguish bt axonal loss vs demylination
3. assess severity and prognosis
4. asses age of lesion
5. nerogenic vs myopathic
**PNS nor CNS test

14

Timelines of nerve lesion: acute, subacute, chronic

Acute 1-2wk
Subacute 4-8 wks
chronic months-yr

15

Describe nerve conduction studies

-motor and sensory
-particularly for myelinated fibres, large d
-axonal loss: lower amplitude (takes few days after injury to happen, mimics conduction block. Test 7-10 days fter injury)
-delymination: slower conduction, lower amplitude only for proximal test

16

What are the electro signs of delymination?

-sign. prolongation of distal latency
-sign. slowing
-conduction block (distal ok, proximal test have lowered amplitude)

17

Recovery timelines for nerve damage?

Demylination: usually complete recovery 1-3 months
Axonal loss: longer, incomplete b/c regeneration is slow

18

What is EMG?

-needle electrode examination
-test at rest and during voluntary movement
-only MOTOR
-Abnormal:
fibrillation potentials at rest = axonal loss
change in motor unit potentials (MUP): long and high indicates re-innervation = chronic lesion
recruitment of motor units
1. reduced: neurogenic
2. early: myogenic

19

What is neurogenic lesion?

-nerve issue: fever motor units available to recruit
-fire faster
-reduced recruitment

20

What is myogenic lesion?

-muscle issue: smaller units
-need to recruit early