Neurophysiology Flashcards Preview

BRB Midterm > Neurophysiology > Flashcards

Flashcards in Neurophysiology Deck (20)
Loading flashcards...

Parts of neuron

Dendrites, axons, soma, synaptic terminal


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


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


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)


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


What does dendrites have that axons don't

-multiple branching
-graded potentials


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


Relationship bt receptor potential and APs

-RPs in large > initiate APs


Factors for conduction velocity

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



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



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


Local anesthetics and pain
-block what?

-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


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


Timelines of nerve lesion: acute, subacute, chronic

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


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


What are the electro signs of delymination?

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


Recovery timelines for nerve damage?

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


What is EMG?

-needle electrode examination
-test at rest and during voluntary movement
-only MOTOR
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


What is neurogenic lesion?

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


What is myogenic lesion?

-muscle issue: smaller units
-need to recruit early