Flashcards in 3-2 Neurophysiology BSC - Heck Deck (34):
What are the 4 parts of a neuron?
Axon terminal/synaptic ending
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
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
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
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
What are the symptoms of peripheral neuropathy?
Pain and dysesthesia
Loss of sensation or reflex; weakness
Fasciculations and paresthesia
What is mononeuropathy?
Involving isolated nerves
Radiculopathy is damaged nerve roots
Due to trauma or pressure
What is polyneuropathy?
Due to metabolites, toxins, demyelinating diseases and chronic infections
Can affect the axon, myelin or synapse
Become more sensitive to mononeuropathy
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
What cells are more susceptible to diabetic neuropathy?
PNS cells more susceptible
Variable degrees of demyelination present
What is the resting membrane potential?
Resting membrane potential -65 mv
Extracellular fluid is 0 mv
What is the synaptic potential characterized?
Slow, graded and local
How is the action potential characterized?
Brief, actively propagated and traveling
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
What is the capacitor in the cell?
The lipid bilayer
Stores charges on opposite sides
What is the resistor in the cell?
Allow an amount of current flow across the membrane
What is the conductance in the cell?
The flow of an ion across the membrane
What is the resistance in the cell?
Opposite of conductance
What is depolarization in an AP?
Decreased internal negativity
Due to inward Na+ current
What is hyperpolarization in an AP?
Increasing internal negativity
Due to outward K+ current
How are VG Na+ channels open, inactivated, or resting?
Voltage-gated Na+ Channels
In response to membrane depolarization
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
How are VG K+ channels open or resting?
Voltage-gated K+ Channels
Slowly, in response to depolarization
Do not inactivate
Remain open as long as membrane is depolarized
After membrane is repolarized
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
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.
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.
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.
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.
What is the time constant for summation? How is affected by number of channels? How is this related to resistance?
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
What is temporal summation?
Based on time constant
Brief conductance changes may only partially charge the membrane
Multiple signals spread over time may reinforce each other
What is the length constant?
The distance required for the current to decline
A few hundred micrometers
What is spatial summation?
Inputs that are physically close may reinforce each other
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)
What does a muscle fiber in a neuromuscular junction contain?
ligand-gated ion channels