Chapter 3: Electrochemical Actions of Neurons Flashcards
Electrochemical action:
Neurons communicate through electrical and chemical signals between them and it happens in 2 stages:
Electrochemical action: Conduction:
Communication of information between neurons by the movement of an electric signal within a neuron, from the dendrites, to the cell body, then through the axon.
Information processing in the neuron itself.
Electrochemical action: Transmission:
Communication of information between neurons from chemical signalling across the synapse.
Resting Potential:
A neuron’s natural electric charge.
Due to the differences of the amount of potassium (K+) inside and outside the neuron’s cell membrane, resulting from open channels that allow K+ to flow outside the membrane, while channels for sodium ions (NA+) are closed. The difference between the electric charges inside and outside of a neuron’s cell membrane. K+ and NA+ ions want to create an equilibrium (to have the same amount of concentration inside and outside the cell), during the resting potential, their doors are closed which keeps an electrical charge in the neuron to build up to -70 millivolts. This is energy that can be released very very quickly if the doors open.
Action Potential:
An electric signal that is conducted along the length of a neuron’s axon to a synapse.
Occurs when K+ channels in the axon close, and NA+ channels open and NA+ flow in. Happens when an electrical signal reaches a threshold which initiate the “all-or-none” signal that moves down the axon. It goes down the axon, jumping across the nodes of Ranvier to the synapse.
When the action potential arrives at the terminal, calcium is released, and the vesicles with the neurotransmitters hate calcium so they go to the gaps, and then release their neurotransmitters into the synaptic gap.
After the neurotransmitters enter the receptor sites of the postsynaptic neuron, it causes an action potential.
Refractory period:
The time following an action potential during which a new action potential cannot happen.
- NA+ channels close.
- The K channels open up, and K+ exits the cell and it closes as the cellular membrane becomes negative since the K+ exited.
After the action potential has reached its maximum, a chemical pump returns the neuron to resting potential by reversing the imbalances of neurons. Action potential can’t be initiated again in the axon until the neuron goes back to resting potential.
Extra neurotransmitters are cleared by: Reuptake
Neurotransmitters are brought back into the sending neuron by a transporter protein to be reused later.
Extra neurotransmitters are cleared by: Enzyme deactivation:
Enzymes destroy the neurotransmitters in the synapse.
Extra neurotransmitters are cleared by: Diffusion
Neurotransmitters drift out away from the synapse and thus can’t be reached by the postsynaptic’s receptors.
Stopping the release of neurotransmitters: Autoreceptors
Autoreceptors detect how much neurotransmitters have been released in the synapse and stop the release of more.
Saltatory conduction:
The action potential jumping from nodes of Ranvier to nodes of Ranvier.
Psychopharmacology:
Chemical transmission across the synapse.
