Resting and activation potentials Flashcards
How is resting potential maintained?
-Via Potassium Sodium Pump
-2K+ IN and 3NA+ OUT, 2K diffuses back in via potassium pump, NA+ pump is less permeable because requires a higher voltage to open.
What is the mV for resting potential?
-70
What is depolarization?
-As a result of a stimuli, enough energy so that can cause voltage gated sodium ions to open
-The axon becomes more permeable (positive voltage), as sodium ions are now moving in as potassium ion moves out.
What is the peak of depolarization?
+40mV
Repolarization
-At the peak, voltage gated sodium ion channels begin to close, and more potassium ions will open at this voltage, this means that the active potential will decrease again and becomes more negative.
Hyperpolarizon
Overshoot beyond resting potential, temporary state, at -80mV
Mexican Wave
-Once an action potential is generated it will move along the Nodes Ranvier of the axon like a mexican wave
Threshold potential
-55mV,
-If stimulus is not strong enough, not enough energy to go above -55,
-If you do reach -55, an active potential is always reached, all peak at same voltage, the bigger stimuli, just means higher frequency of AP.
- This is called the all or nothing principle
Why is Threshold potential important to humans?
-To make sure animals only respond to large enough stimuli,
-not be overstimulated by every little change in environment
-this would hinder survival not help it
Refractory Period
-The membrane cannot be stimulated
-sodium ions are recovering and cannot be opened
-
Why is the Refractory period important?
-To ensure discrete impulses are produced, i.e. impulses cannot overlap, each AP is separate from each other, in order for the information of the stimulus to be fully processed
-Ensures APs travel in one direction, if was not spreading of potassium and sodium ions in two directions which would prevent a response.
-Limits number of impulse transmission over reactions, prevents being over reactant to a stimulus
Factors which affect Action Potential speed
-Temperature
-Diameter of the axon
-The myelination and saltatory conduction
Myelination and saltatory Conduction
-Schwann cells wrap around the axon, creating the myelin sheath, these cells are lipid and this means they insulate the axon and do not allow to charged molecules to pass.
-This means that the action potential has to jump along the Node Ranvier, as this is where charged molecules can pass through
-Speeds up reaction does not have to generate AP across the full length of axon
Diameter of the Axon
-A wide diameter means that less ions leak out of the Axon and that means that the threshold potential of -55 can be reached more easily
Temperature
-Facilitated diffusion increases as the ions move faster at higher temperatures
-K/NA pump requires ATP. More ATP is produced off of respiration at higher temperatures (enzymes involved in respiration)
