Nuerones

Question 1

Describe spatial summation (6)

Answer 1

• several pre synaptic neurones synapse w the same post synaptic neurone
• together they can release enough neurotransmitters to open enough ligand gated sodium ion channels for long enough
• so enough sodium ions can enter the post synaptic neurone by FD
• so that threshold reached and exceeded
• so VG Na+ channels open
• so more Na+ enter and the post synaptic neurone is depolarised so action potential can occur

Question 2

Describe temporal summation: (6)

Answer 2

• high frequency of action potentials released by a single presynaptic neurone
• meaning it releases neurotransmitter many times over for a short period
• causes enough sodium ion ligand gated channels to be open for long enough
• so enough sodium ions can enter the post synaptic neurone by FD
• so that threshold reached and exceeded
• so VG Na+ channels open
• so more Na+ enter and the post synaptic neurone is depolarised so action potential can occur