Excitatory & Inhibitory Neurotransmissions in the CNS Flashcards
What is the axon hillock responsible for?
Decides whether an action potential should be created - ‘All or nothing’ mechanism
Do all neurons generate action potentials?
NO
What causes upstroke of action potential?
Influx of sodium through voltage gated Na+ channels
What causes the downstroke in an action potential?
The exit of K+ from the cell through voltage activated K+ channels
How is ion selectivity relevant to an action potential?
When Na+ is entering, K+ cannot leave and visa versa
Why is the cell membrane considered ‘leaky’?
Along the cell membrane there are pores, this means that the current can leak out
How does a leaky membrane mean passive signals do not travel far?
This is due to current leaking out and therefore the amplitude reducing the further away from the origin it gets.
How can current leakage be reduced?
Decreasing ri (possibly by increasing axon diameter), Increase rm (possibly by adding an insulating material I.e. myelin sheath)
How does a myelin sheath effect conduction?
Conduction in a myelinated axon is much faster than in a non-myelinated axon of the same diameter
What is rm?
Membrane resistance
What is ri?
Axoplasmic resistance
What does saltatory conduction mean?
Only occurs in myelinated axons, it is when the AP jumps from one node of ranvier to the other
(voltage activated Na+ channels cluster at nodes)
What are the two types of neurotransmitter receptor?
Inotropic and metabotropic
Which neurotransmitter receptor is responsible for direct gating?
Inotropic
Which neurotransmitter receptor is responsible for indirect gating?
Metabotropic
