Action potiential Flashcards
What causes a change in membrane potiential
A change in voltage gated channel activity
How does an action potiential work
It is triggered when a cell reaches threshold
What happens in milk fever cows?
Calcium concentration decreases in the extracellular fluid, this will elevate the resting membrane potiential of the cell in a calcium deficient cow. If resting membrane potiential is increased enough it will exceed threshold which means action potientials will be triggered which causes excitability and unpredictable movement.
Movement of action potientials is facilitated by
Positive charge on outside of cell membrane and negative charge on inside of cell membrane
What happens when an action potiential moves through the membrane
Current loops are repeated on other areas of the membrane and flips back to initial point of depolarisation then it hits a point in the membrane which is sitting in its absolute refractory period so you cant stimulate another action potiential.
What part of a neuron has high conc of sodium and potassium channels
Axon hillock
What part of the cell is most likely to fire an AP
Axon hillock.
What do u need in order to form a current loop
Separation of charge in the membrane
What is myelination
When a neuron is insulated around the axon, cant form a current loop
What are the gaps between insulated layers called
Nodes of ranvier
What are nodes of ranvier
Breaks in the myelination and the separation of charge across the cell membrane so can form a current loop
What is saltorary conduction?
When an action potiential is formed at gaps, it will depolarise that node of ranvier and then jump to the next one and depolarise that and this happens in both directions which means it is bidirectional
What is the advantage of saltatory conduction
Faster transmission and preserves energy
Divergent pathway
One neuron passes information to multiple neurons
Convergent pathway
When multiple neurons pass info to one neuron
What are gap junctions
Electrical synapses when there is direct passage of charge between 2 cells
What are excitable cells
Nerve and muscle
How does an action potiential through a neuron start
- Take an AP and then need to convert electrical signal to chemical then back to electrical
- In terminal of [presynaptic cells, there is synaptic vesicles which contain a neurotransmitter. On post synaptic cells there is receptors
Pathway if action potiential through a neuron
1.Move from axon hillock down to terminal, a terminal there is a large amount of voltage gated CALCIUM channels, this changes membrane potiential
2. Calcium voltage gated channels open
3. There is calcium sitting in the ECF at a higher concentration than ICF.
4. Calcium moves into the cell
5. Due to calcium increase in the cell, vesicles containing neurotransmitters move to specific docking sites on the cell membrane
6. Neurotransmitter is released and diffuses across the synaptic cleft
7. The NT then binds to receptors on the post synaptic cell. These receptors can either be iron channels or linked to iron channels.
8.when NT binds to receptor this causes a change in membrane permeability which allows ions to be transported across the membrane.
9. Sodium channels open and this causes depolarisation to occur
How are neurotransmitters removed from a synapse
Diffusion
Reuptake
Enzyme degradation
Inhibitory post synaptic potiential
When NT can close sodium channels and cause hypopolarisation which brings cell away from threshold
How many excitatory signals are needed to form an action potiential
20
Size of graded potiential depends on
Number of neurotransmitter
Number of receptors
Temporal summation is
One place on the membrane over time
