L6 Excitable Cells Pt 3 X Flashcards
What is space constant in neuroscience?
The space constant, also known as the length constant, is a measure of how far a sub-threshold electrical potential will spread along a nerve axon
How can you increase the conduction velocity without incraesing the diameter of the axon?
This can be done by insulating the axon which is done by the myelin sheath.
What are the factors influencing the spread of depolarization down the axon?
- Physical properties of axon
- Diameter
- Leaky(Permeability) membrane
What does Cv stand for?
Conduction velocity
What is conducting velocity?
Conducting velocity refers to the speed at which an electrical impulse travels along a nerve fiber
What’s the difference between conducting velocity and space constant?
Conducting velocity - The speed at which an electrical impulse (action potential) travels along a nerve fiber.
Space constant - A measure of how far a subthreshold electrical potential (graded potential) will spread along a nerve fiber before it decays.
What is Rm?
Membrane resistance
What is the definition of membrane resistance?
The resistance of the membrane to the flow of ions across it.
Higher Rm means less leakage of current
What is Ri?
Axial Resistance
What is the definition of axial resistance?
The resistance to current flow along the length of the axon’s cytoplasm.
Lower Ri allows current to flow more easily
Can action potentials be excitatory or inhibitory?
No
Can graded potentials be excitatory or inhibitory?
Yes
What causes graded potential?
They are caused by:
1. Opening of neurotransmitter-gated ion channels.
2. Opening/closing of pottasium channels.
What is temporal summation?
Summation of graded potentials from the same synapse over time
What is spatial summation?
Summation of graded potentials from different synapses at the same time.
What is myelin made up of ?
Mylin is made up by wrapping the plasma membrane of glia support cells round the axon
Schwann cells in peripheral nervous system, oligodendrocites in cns
There are breaks in the myelin sheeth where ion channels involved in generation of action potentials are concentrated, and where action potentials will therefore be generated…Node of Ranvier
What does the frequency of the action potential depend on?
The FREQUENCY of the action potentials is dependent on the size of the depolarizing stimulus…the stronger the stimulus (ie. The more positive) … the higher the frequency,this provides a way to encode stimulation intensity in the nervous system.
What is EPSP?
Excitatory Postsynaptic Potential.
