What is the voltage across the membrane at resting potential?
How is resting potential maintained?
Sodium potassium pumps transports 3 sodium ions out of the neurone for every 2 potassium ions that are transported in. The membrane is impermeable to sodium and permeable to potassium.
What happen in response to the stimulus to make the inside of the neurone less negative?
Sodium channels open. Sodium diffuses into the neurone down the electrochemical gradient.
What happens if the threshold (around -55mV) is reached?
Depolarisation occurs. More sodium channels open, sodium diffuses rapidly into the neurone.
At what potential difference do sodium channels close?
After depolarisation, how does the neurone return to resting potential?
Sodium channels close and potassium channels open. Potassium diffuses out of the neurone.
Why does hyperpolarisation occur?
The potassium ion channels are slow to close so there's a slight overshoot where too many potassium ions diffuse out of the neurone.
What is the refractory period?
The period of time after an action potential when the neurone can't be excited.
How does the nuerone respond to a bigger stimulus?
Action potentials will occur more frequently.
During an action potential, the membrane potential rises to +40 mV and then falls. Use information from the graph to explain the fall in membrane potential.
Potassium channels open;
Sodium channels close;
Sodium and potassium ions can only cross the axon membrane through proteins.
can not pass through phospholipid bilayer;
because water soluble / not lipid soluble / charged / hydrophilic /
Explain the importance of reflex actions.
1. automatic (adjustments to changes in environment) / involuntary;
2. reducing / avoiding damage to tissues / prevents injury / named injury
3. role in homeostasis / example;
4. posture / balance;
5. finding / obtaining food / mate / suitable conditions;
6. escape from predators;
Give two differences between a cholinergic synapse and a neuromuscular junction.
neurone to neurone and neurone to muscle;
action potential in neurone and no action potential in muscle /
no summation in muscle;
muscle response always excitatory (never inhibitory);
some neuromuscular junctions have different neurotransmitters;