05 - Action Potentials Flashcards
What is a cell membrane made of?
Phospholipid molecules
What are the two important kinds of protein for electrical changes?
Ion channels and pumps
What is an ion channel?
A transmembrane protein channel that allows a specific ion to diffuse across the membrane
What do ions flow passively through?
Channels
What may this movement of ions be driven by?
Electrical (voltage) or chemical (concentration)
For the following types of ion channels answer what they are and if and when they are open/closed: Ligand Voltage Mechanical Leakage
Ligand - open on ligand binding
Voltage - always open
Mechanical - open when receptor changes shape
Leakage - always open
When does an action potential occur?
When the sodium channels open allowing a massive influx of sodium ions - this is called depolarisation
What is the refactory period?
When the sodium channels close and cannot be reopened until the voltage returns to resting levels of -70mV
What is depolarisation?
A change in a cell’s membrane potential such that the inside of the membrane is made less negative relative to the outside
When does repolarisation occur?
When K+ channels open and the K+- escapes
Where can action potential conduction take place?
Along the length of the axon
Between the neurons - at a synapse
What structures contribute to action potential conduction?
Ion channels
Myelin sheaths
Nodes of Ranvier
Saltory conduction
What is a myelin sheath?
An insulating coat of the cell membranes produced by Schwann cells (CNS) or oligodendrites (CNS)
What is myelination essential for?
Rapid and accurate impulse connection
What are nodes of ranvier
These are gaps in a myelin sheath between shwann cells of certain acorns where an action potential may be generated
Is there any insulation at nodes of ranvier?
No, the axon membrane contacts with the extracellular fluid so the depolarisation and repolarisation can occur whereas it cannot in Schwann cells
What are synapses the point of?
The signal is transferred by chemical exchange instead of electrical signal
What is signal integration?
Where the target cell is another nerve, several impulses may be needed before the post synaptic is excited enough to fire an action potential
What happens in the neuromuscular junction?
The transmitter released (acetylcholine) excites the muscle to give rise to an action potential in the muscle
