Action Potentials Flashcards
What is ‘Hyperpolarisation?’
-Membrane Potential becomes more negative
(inside)
-Returns cell to Resting Membrane Potential
What is ‘Depolarisation?’
- Membrane Potential becomes more positive
- (less negative inside)
How does Depolarisation occur?
- Entry of Sodium ions (influx) into cell
- Positive ions
What type of Channels are Sodium Channels?
-Ligand Gated Channels
What does it mean by ‘Sodium Channels’ require a Driving Force?
- net electromotive force that acts on the ion
- (Vm-ENa)
- Membrane Potential-Sodium Equilibrium Potential
Name X3 ways an ion channel is stimulated
- Physical Stimuli
- Membrane Voltage
- Chemicals
What type of channel is responsible for downstream depolarisation of a neuron?
- Voltage Gated Sodium Channels
- Voltage Gated Potassium Channels
Which channels are responsible for Hyperpolarisation/Reploraisation?
-Voltage Gated Potassium Channels
What is a Threshold Value?
-Minimum value membrane potential must be for an Action Potential to be fired triggering depolarisation
Is Resting Membrane Potential below Threshold value?
YES
Explain the five stages of Action Potential Firing
1) Threshold Value is met
2) -Action Potential is Fired
3) -Depolarisation Occurs (Upstroke)
4) Repolarisation (Downstream) – Return to Resting Potential
5) Return to Resting Membrane Potential (Hyperpolarisation-more negative)
What is Upstroke more commonly known as?
Depolarisation
What is Upstroke more commonly known as?
Repolarisation
What is Upstroke more commonly known as?
Depolarisation
What is the difference between Hyperpolarisation and Reploraisation?
-Repolarisation comes before Hyperpolarisation
Repolarisation-Entry Potassium Ions and inactivation of sodium channels
Hyperpolarisation- CLOSURE of potassium channels
When do Sodium Channels become inactivated?
- During repolarisation become inactivated
- Voltage Gated Potassium Channels open
What is the Refractory Period?
- Amount of time cell not producing an Action Potential before ready for next one to be fired
- Ensures Action Potential is successful when occurs
What is Absolute Refractory Period?
- NO Stimulus
- ALL Channels are inactivated
What is Relative Refractory period?
- Very STRONG stimulus
- Can cause Second Action Potential as mixed-some activated and some inactivated channels-still partially capable
What is order of movement through a neuron?
1) Dendrites
2) Axon Hillock (trigger period)
3) Axon (Conducting part)
4) Axon Terminal (Output)
What is Contagious Conduction?
-Process-Spreading Action Potentials from one area to the next
What is Salatory Conduction?
-Action potential jumps from one node to another
What is Myelin Sheath?
- iInsulating Layer
- Speeds up transmission of electrical impulses
