NERVE PHYSIOLOGY- Action potential Flashcards
Parts of a neuron
Dendrites
Cell body
Axon
What is a neuron?
Functional unit of nerve tissue
Describe a dendrite
Shorter, numerous processes
Afferent nerve
Part of neuron that contains the nucleus, mitochondria and receive stimuli from dendrites
Cell body
What is an axon
Single long cylindrical extension of the cell
Efferent nerve
Dendrite vs axon
Dendrite - afferent towards
Axon - efferent away
Nerve coverings
Myelin sheath
Neurolemma
Nodes of ranvier
Describe myelin sheath
SERVES AS INSULATOR
Schwann cells wrapped spirally
Prevents movement of ions
Outermost covering of a nerve
Neurolemma
Describe nodes of ranvier
Junc bet 2 succ schwann cells
Small uninsulated area
Contains sphingomyelin
Schwann cells
What is an impulse?
It is an electric current aka as action potential
What is an action potential??
Changes in the membrane potentials will open the membrane channels for exchange of ions
Channels that are present in the membrane
Voltage gated K channels Na channel slow gate/one Na channel fast gate/one K leak channel Na K pump
It is open only if needed, closed during the resting stage.
VOLTAGE GATED K CHANNEL
What is a voltage gated K channel
It is a channel that opens slowly when membrane potential rises from -90MV to zero
It allows increase K diffusion OUTWARD
Na channel that is open at REST
Na channel SLOW GATE
Describe Na channel FAST GATE
It opens during DEpolarization making the membrane permeable to Na ions
What is -90MV?
The nerve fiber is at rest
Or the NEGATIVE RESTING STAGE
Describe K leak channel
It is an open and continuous pathway for small K leakage out of the membrane creating a negative resting membrane
Describe the sodium potassium pump
It is an electrogenic pump that continuously pump 3 Na ions out and 2 K ions into the cell leaving a net deficit of positive ions on the inside
What is depolarization
Positive charged inside the cell membrane
Summary of the sequences of events in the propagation of impulse
Permeability to Na - Na influx - depolarization
Permeability to K - K efflux - repolarization
Na inactivity - stop Na influx - repolarization
NaK pump - 3 Na out/ 2 K in - Negative resting membrane potential
Give the Sequence of events in propagation of impulse
Resting stage
The fast gate of Na channel opens in the presence of stimulus
(Depolarization)
Na channel closes
Rapid diffusion of K ions to the exterior
(repolarization)
Na K pump continuously pump 3 Na ions out and 2 K ions in
Depolarization vs Repolarization
De- positively charged inside
Re- nerve fiber goes back to negative resting membrane potential or stage
What is an action potential
Changes in membrane potential.
There is a certain movt of ions
- reversal in the electrical potential across a membrane when activated by a stimulus
Ways on how to regulate func of other system
Nervous control
Hormonal control
