Week 2 Lectures (Neuron form and function) Flashcards
What part of neurons conduct electrical signals?
The cell membrane
What is the resting membrane potential difference?
Around 70Mv
What is the direction of flow in a neuron?
Dendrites - Cell body - Axon - Axon terminal
Why is there a negative resting potential in a neuron?
Because sodium (Na+) is being pumped out faster than K+ is being pumped in
This means there is a build up of more positive Na+ ions outside the cell than there is K+ ions inside the cell
How much of the brains energy is consumed by maintaining the resting potential?
Around 60%
What happens in the dendrites in response to a stimulus?
- There is a stimulus
- This causes a graded potential change in the dendrites as more positive ions are pumped into the cell, driving the potential back towards 0
- This causes a ripple of depolarisation across the dendrites
- These can add up to a larger ripple when they converge on the cell body
Over how many mm does the neural signal in the dentrites decay?
1-2mm
What kind of channel is there in the axon initial segment?
A voltage-gated sodium channel
What happens when a certain potential is reached at the voltage gated sodium channel?
Sodium ions flood in
What happens when the voltage gated sodium channels are opened?
- There is a big depolarising spike of potential change which goes up into positive level
- Homeostatic mechanisms kick in and the resting potential is bought back down
- It overshoots (hyperpolarisation) before settling back to -70Mv
What are two characteristics of the action potential?
It is an all or nothing stimulus
It only passes in one direction
Where are passive potentials located and where are action potentials located?
Passive potentials are located in the dendrites
Action potentials are located in the axon
What is an axodendritic synapse?
Between axon and dendrite
What is an axoaxonic synapse
axon to axon
What is an axosomatic synapse?
Axon to soma
