Neurons Flashcards
What are the parts of a neuron?
cell body (soma), axon, dendrites, axon terminal (boutons), axon hillock
What is the resting membrane potential of a neuron?
The resting membrane potential of a neuron is about -70 mV (mV=millivolt) - this means that the inside of the neuron is 70 mV less than the outside.
Where is positive and where is negative?
the inside of the cell is negative and the outside is positive
What are the values of the Na/K pump?
3Na+ out and 2K+ in
What is depolarisation?
when membrane potential becomes less negative
What is hyper-polarisation?
when membrane potential becomes more negative
At what value is the action potential triggered?
-55mV
At what value do K+ channels open?
+35mV
Why does hyper-polarisation occur and what disease is this mechanism altered?
it stops another signal being sent too quickly and allows for a refractory period
in epilepsy, signals can be sent one after the other
Describe the process of an action potential
1 - stimulus applied
2 - neurotransmitter attaches and opens Na+ channels, Na+ flows in
3- at -55mV depolarisation occurs, voltage gated Na+ channels open causing an influx of Na+
4- at 30mV, K+ voltage gated channels open and hyperpolarisation occurs
5- Na/K+ pump resets membrane potential
How does local anaesthetic work?
stops nerve conduction by blocking Na channels which stops an AP being transmitted therefore no impulses are transmitted
What is the period of in-excitability after an action potential when the neuron cannot respond at any stimulus called?
refractory period
Why do giant axons not exist in humans?
too slow
What counteracts slowness in transmission?
myelin sheets are wrapped around the axon, they provide insulation and better conduction increasing the speed
What is along the axon?
nodes of ravier that help a AP jump from node to node helping ion flow
