MT - Neuronal Function (Part 2) Flashcards
What does “signal transduction” actually mean?
It describes the way a neurotransmitter receptor changes a chemical signal to an electrical signal.
What is actually changing during signal transduction?
The ion permeability of the membrane.
Of the ligand-gated ion channels, which cause depolarization and which cause hyperpolarization?
Depol.: Glutamate receptors, nicotinic ACh receptors, 5-HT3, P2X
Hyperpol.: GABAₐ receptors, glycine receptors
Of the voltage-gated ion channels, which cause depolarization and which cause hyperpolarization?
Depol.: Na+ and Ca 2+
Hyperpol.: K+
How far do graded potentials travel?
Short distances.
What is a graded potential?
A temporary change in the membrane voltage which depends on the size of the stimulus.
What 3 factors cause graded potentials to decrement with distance?
- Ion leakage across membrane
- Resistance of cytoplasm
- Resistance of membrane
How far do action potentials travel?
Long distances.
How is an action potential triggered? Where in the neuron?
Triggered by net graded potentials at the axon hillock.
What are the 3 phases of an action potential in order?
- Depolarization
- Repolarization
- Hyperpolarization
What differentiates the absolute refractory period of an axon from the relative refractory period?
Absolute: cell can’t generate an AP
Relative: AP generation is possible but very hard
What ion channels open during the depolarization phase of an action potential?
NA+ channels.
What ion channels open during the repolarization phase of an action potential?
K+ channels.
How does the closing of Na+ channels differ from that of K+ channels following an action potential?
Na+ channels: inactivated
K+ channels: close slowly
What model organism was used for the earliest action potential experiments? Why?
Squid, because they have GIANT axons up to 1mm diameter.
