3-2 Neurophysiology BSC - Heck Flashcards Preview

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Flashcards in 3-2 Neurophysiology BSC - Heck Deck (34):
1

What are the 4 parts of a neuron?

Dendrite
Soma
Axon
Axon terminal/synaptic ending

2

What is the description, major organelles, and major function of the dendrite?

Description: tapered extension of cell body

Major organelles: cytoskeleton, mitochondria

Primary fxn: collect info from other neurons

3

What is the description, major organelles, and major function of the soma?

Description: may have 1+ processes, typically 1 axon with many dendrites

Organelles: nucleus, golgi appartus, nissl substance, cytoskeleton, mitochondria

Primary function: synthesize macromolecules, integrate electrical signals

4

What is the description, major organelles, and major function of the axon?

Description: single, cylindrical, may be many centimeters long, may be myelinated or unmyelinated

Organelles: cytoskeleton, mitochondria, transport vesicles

Function: conduct info to other neurons

5

What is the description, major organelles, and major function of the axon terminal?

description: vesicle-filled appositions to part of another neuron, most are axodendritic or axosomatic, but other configurations occur

Organlles: synaptic vesicles and mitochondria

Function: transmit onfo ot other neurons

6

What are the symptoms of peripheral neuropathy?

Symptoms
Positive:
Pain and dysesthesia

Negative:
Loss of sensation or reflex; weakness

Irritative:
Fasciculations and paresthesia

7

What is mononeuropathy?

Involving isolated nerves
Radiculopathy is damaged nerve roots
Due to trauma or pressure

8

What is polyneuropathy?

Polyneuropathy
Due to metabolites, toxins, demyelinating diseases and chronic infections
Can affect the axon, myelin or synapse
Become more sensitive to mononeuropathy

9

What is the trigger for diabetic neurppathy?

Hyperglycemia serves as trigger
Inflammatory, metabolic and ischemic

Pro-oxidative and pro-inflammatory
Variably affects cell types
Variable presentation of disease

10

What cells are more susceptible to diabetic neuropathy?

PNS cells more susceptible
Predominantly axonal
Variable degrees of demyelination present

11

What is the resting membrane potential?

Resting membrane potential -65 mv
Extracellular fluid is 0 mv

12

What is the synaptic potential characterized?

Synaptic potential
Slow, graded and local

13

How is the action potential characterized?

Action potential
Brief, actively propagated and traveling

14

What determines resting membrane potential?

Resting Membrane Potential (-65 mv)
Inward Na+ current
Outward K+ current
Closer to K+ equilibrium potential because of greater K+ permeability
Maintained by Na/K-ATPase

15

What is the capacitor in the cell?

Capacitor
The lipid bilayer
Stores charges on opposite sides

16

What is the resistor in the cell?

Resistor
Ion channels
Allow an amount of current flow across the membrane

17

What is the conductance in the cell?

The flow of an ion across the membrane

18

What is the resistance in the cell?

Opposite of conductance

19

What is depolarization in an AP?

Depolarization
Decreased internal negativity
Due to inward Na+ current

20

What is hyperpolarization in an AP?

Hyperpolarization
Increasing internal negativity
Due to outward K+ current

21

How are VG Na+ channels open, inactivated, or resting?

Voltage-gated Na+ Channels

Open
In response to membrane depolarization

Inactivated
Closed and will not reopen in response to depolarization

Deinactivated or resting
After the membrane is repolarized, return to a confirmation that allows them to be opened in response to depolarization

22

How are VG K+ channels open or resting?

Voltage-gated K+ Channels

Open
Slowly, in response to depolarization
Do not inactivate
Remain open as long as membrane is depolarized

Resting
After membrane is repolarized

23

What is the resting state of the AP?

Activation gates on the Na+ and K+ channels are closed, and the membrane's resting potential is maintained

24

What is the depolarization state of the AP?

Stimulus opens the activations gates on some Na+ channels. Na+ influx through those channels depolarizes the membrane. If the depolarization reaches the threshold, it triggers an AP.

25

What is the rising phase of the action potential?

Depolarization opens the activation gates on most Na+ channels, while the K+ channels activation gates remain closed. Na+ influx makes the inside of the membrane positive with respect to the outside.

26

What is the falling phase of the AP?

The inactivation gates on most Na+ channels close, blocking Na+ influx. The activation gates on most K+ channels open, permitting K+ efflux which makes inside of the cell negative.

27

What is the undershoot phase of the AP?

Both gates of the Na+ channels are closed, but the activation gates on some K+ channels are still open. As these gates close on most K+ channels, and the inactivation gates open on most Na+ channels, the membrane returns to its resting state.

28

What is the time constant for summation? How is affected by number of channels? How is this related to resistance?

Time Constant
How long to reach final voltage
Usually 10 msec or less

Dependent on number of channels
Many open channels lead to lower time constant
High conductance, low resistance
Few open channels lead to higher time constant
Low conductance, high resistance

29

What is temporal summation?

Temporal Summation
Based on time constant
Brief conductance changes may only partially charge the membrane
Multiple signals spread over time may reinforce each other

30

What is the length constant?

The distance required for the current to decline
A few hundred micrometers

31

What is spatial summation?

Inputs that are physically close may reinforce each other

32

Is a motor axon myelinated at terminus? How many branches? What NT does it release?

Unmyelinated at terminus
Multiple terminal branches
Protected by Schwann cells
Contain vesicles filled with neurotransmitter (acetylcholine)

33

What does a muscle fiber in a neuromuscular junction contain?

ligand-gated ion channels

34

What axons are affected first in peripheral neuropathy?

longest axons first
“Stocking and glove” defects in sensation and strength