6.5 Nerves, Hormones, and Homeostasis

Terms in this set (12)

The nerve at rest
We have an imbalance of ions inside and outside of the plasma membranes.
The important ions are K+ and Na+.
K+ is more concentrated inside the cell (30X more) and therefore tends to diffuse out of the cell.
Na+ is more concentrated outside (10X more) of the cell and thus tends to diffuse into the cell, but at a lower rate.
Na+-K+ pumps embedded in the plasma membrane work against both ions' diffusion gradients in order to preserve the gradients and the membrane potential.
The inside of the cell is - charged due to Cl- and some proteins while the outside is + charged due to Na+.
The plasma membrane is said to be polarised (+ and - poles)
The resting potential is -70 mV.

When a nerve is stimulated the properties of the plasma membrane will change and Na+ - K+ channels will open.
Na+ will come inside the cell.
The inside of the cell will become more + and more or depolarised.
The outside of the cell will become -.
This is called the reverse polarisation.
At a certain point, you will have too many + charges inside the cell.
The K+ will begin to leave the cell.
This highly + charges inside the cell will start to decrease.
The plasma membrane potential goes back to his original level but the Na+ and K+ are not at the right place.
High concentration of Na+ inside the cell.
High concentration of K+ outside the cell.
To get the original setting, the Na+ - K+ pumps start working.
This restore the distribution of ions.
That period is called the refractory period or recovery period.
It means that a neuron is unable to respond to another stimulus.
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