What does the central nervous system consist of?
- Brain.
- Spinal cord.
What does the peripheral nervous system consist of?
All neurones other than the brain and spinal cord.
What is the somatic nervous system?
Conscious control.
What is the autonomic nervous system?
Unconscious control.
What does the parasympathetic nervous system do?
Slows things down.
What does the sympathetic nervous system do?
Speeds things up.
What do receptors do?
- They are specific so will only detect one type of stimulus.
- They transform stimulus into an electrical impulse.
What is the sensory neurone consist of?
- Single long dendron.
- Single short axon.
What does the relay neurone consist of?
- Many short dendrites..
- Many short axons.
What does the motor neurone consist of?
- Many short dendrites.
- Single long axon.
- Ends with neuromuscular junction.
What can the effector be?
- Muscle.
- Gland.
What are the sodium potassium pumps doing during resting potential?
- Active transport (using ATP).
- 3 Sodium out.
- 2 potassium in.
What are voltage gated sodium ion channels doing during resting potential?
- Closed.
- Membrane is not permeable to Na+.
What are the potassium ion channels doing during resting potential?
- Open.
- Some K+ diffuses out down the electrochemical gradient.
- Doesn’t reach equilibrium because of the positive charge outside.
What are the stages of an action potential?
1 - resting potential. 2 - generator potential. 3 - threshold. 4 - depolarisation. 5 - repolarisation. 6 - hyperpolarisation.
What happens is a generator potential does not reach threshold?
- Weak stimulus.
- Some Na+ channels open.
- Some Na+ diffuses in.
- Does not reach threshold.
- Sodium-potassium pump restores resting potential.
What happens if the generator potential reaches threshold?
- Many voltage gated Na+ channels open.
- Na+ diffuses into axon.
What happens during depolarisation?
- Na+ channels open.
- Na+ diffuses in.
What happens during repolaristiaon?
- K+ channels open (voltage gated).
- K+ diffuses in.
- Voltage gated Na+ close.
What happens during hyperpolarisation?
- When membrane potential is more negative than resting potential.
- K+ channels are slow to close.
Why is a refractory period essential?
- Another action potential cannot be started.
- Makes action potentials discrete (don’t overlap) and unidirectional (one-way).
