Neurons and synapses Flashcards
Describe Nerve impulse transmission
Nerve impluse is the action potential propagated across the length of an axon. In the plasma membrane of an axon consist sodium and potassium pumps. Prior to there being a stimulus, both the potassium pump and the sodium pump are turn on, causing sodium ions to be pumped out and potassium ions to be pumped in via active transport. The concentration gradients created by the sodium and potassium ions cause there to be a positive net charge on the outside of the membrane and a negative net charge on the inside of the membrane.
When acted upon by a stimulus, the sodium pump is turned off while the potassium pump is kept on. Sodium channels then open and allow sodium ions to diffuse through the neuron down the concentration gradient, causing there to be a net negative charge on the outside and a net positive charge on the inside.
The process of depolarisation then occurs. In this phase, the postassium pump is turned off whilst the sodium pump also remains off. Potassium channels then open and allow potassium ions to diffuse out of the neuron, causing the net charge on the outside and on the inside to be neutral.
Eventually, repolarisation occurs as both the sodium and potassium pumps are turned on again, restoring by the original concentration gradient by pumping sodium ions back out and potassium in via active transport, ready for the next impulse.
