Propagation of the Action Potential and the Chemical Synapse Flashcards
What happens to the charge of a section of axons when it depolarizes?
The positive charges move by local current flow into adjacent sections of cytoplasm
What happens when voltage gated Na+ channels open at -55mV with respect to the “all or nothing” principle
If the threshold is reached an action potential will occur
What stops Na+ from entering during the absolute refractory period with respect to “unidirectional” principal
Na+ inactivation gate
What are the 2 things that affect the speed of action potential conduction down an axon
- Diameter of the axon
- larger diameter=faster conduction - The resistance of the axon membrane to ion leakage
- increased ion leakage = slower action potential
How do we prevent ion leakage
Myelin Sheath
What is myelin
Multiple layers of cell membrane that wrap around and insulate axons to prevent ion leakage
Why can axon have smaller diameters and still generate fast action potentials
Conduction is faster with myelin, since its insulated to protect leakage, it can be smaller in diameter
What is saltatory conduction
the “leap-frogging” of the action potential down myelinated axons
Does saltatory conduction involve membrane permeability changes
Yes, at the the nodes of ranvier
What is the synapse made of
The pre synaptic cell’s axon terminal and the plasma membrane of the post synaptic cell
What triggers the release of neurotransmitters from vesicles
Depolarization
What are the 5 steps in synapse to pass information from one neuron to the other
- Depolarizing stimulus arrives at the axon terminals
- Depolarization triggers Ca+ voltage gated channels to open, allowing Ca+ to enter the axon terminal
- Ca+ in the axon terminal signals the docking of the vesicles to the membrane of the post synaptic cell
- Neurotransmitters are released and bind to receptors on the post synaptic cell
- Ion channels open or close depending on what the signal is
Neurotransmitters are rapidly removed from the post synaptic cleft. What are the 3 main ways neurotransmitters are removed?
- Neurotransmitters are returned to axon terminals (recycled because they are expensive to make)
- Enzymes in synapse inactivate neurotransmitters
- Neurotransmitters diffuse out of the synaptic cleft
What do neurotransmitters need to do to induce a rapid response
Do this by opening ion channels
What is EPSP and what does it do
Excitatory post synaptic potential
-if the action potential from pre synaptic cell results in depolarization of the post synaptic cell
