Propagation of the Action Potential and the Chemical Synapse Flashcards Preview

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Flashcards in Propagation of the Action Potential and the Chemical Synapse Deck (16):

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

1. Diameter of the axon
-larger diameter=faster conduction
2. 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



What are the 5 steps in synapse to pass information from one neuron to the other

1. Depolarizing stimulus arrives at the axon terminals
2. Depolarization triggers Ca+ voltage gated channels to open, allowing Ca+ to enter the axon terminal
3. Ca+ in the axon terminal signals the docking of the vesicles to the membrane of the post synaptic cell
4. Neurotransmitters are released and bind to receptors on the post synaptic cell
5. 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?

1. Neurotransmitters are returned to axon terminals (recycled because they are expensive to make)
2. Enzymes in synapse inactivate neurotransmitters
3. 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


What is IPSP and what does it do

Inhibitory post synaptic potential
-if the cation potential results in hyper polarization of the post synaptic cell