13.11 Nervous system Flashcards
What are the two parts of the nervous system?
Central and peripheral nervous system
What are the two parts of the peripheral nervous syetm?
Autonomic and voluntary
What are neurones?
Specialised cells that are adapted to carry electrical impulses from one part of the body to another
Name the three types of neurons
Sensory
Relay
Motor
what is the purpose of a myelin sheath?
To increase the speed of electrical impulses along the axon
How is a resting potential established?
- There is a higher concentration of sodium outside the neuron and potassium inside the neuron
- The Na+ channels are closed
- Some of the K+ channel proteins are open so K+ ions can diffuse out
- The inside of the neuron is slightly negative compared to the inside so it at resting potential
How are nerve impulses transmitted?
An action potential happens when the membrane reaches threshold and becomes depolarised
- The membrane potential goes from -70mV to +40mV
Explain depolarisation
- The stimulus causes the membrane to become more permeable to Na+ ions
- If the membrane potential reaches threshold then the Na+ channels open
- Na+ ions rapidly diffuse into the cell
There is a higher concentration of Na+ ions inside the cell so the inside is now positive and is depolarised - The K+ channels are mostly closed
Explain repolarisation
- The Na+ channels close and the K+ channels open when the potential difference reaches +40mV
- The K+ ions diffuse out of the cell as there are more K+ ions on the inside of the axon than the inside
Explain hyperpolarisation
- The K+ channels remain open longer than needed to reach resting potential, this makes the inside of the cell even more negative (-90mV)
- the NaK pump restores the resting potential back to -70mV
Refractory period definition
The period of inactivation following the transmission of an impulse, the time taken to restore resting potential
