Synapses

Question 1

What are synapses

Answer 1

Gaps between nerve cells.

Action potentials cannot pass between nerve cells across synapse, so transmitter substances are used

Question 2

Structure of a synapse

Answer 2

The presynaptic membrane (before the gap) allows release of chemicals (neurotransmitters) when impulses are arriving to stimulate impulses in cell after gap (postsynaptic cell)

Question 3

Synapses Step 1

Answer 3

The action potential arrives at the synapse

Question 4

Synapses Step 2

Answer 4

Calcium channels open in presynaptic membrane.

Calcium ions diffuse into neuron membrane across a concentration gradient

Question 5

Synapses Step 3

Answer 5

As calcium concentration increases, synaptic vesicles containing neurotransmitters such as dopamine and acetylcholine move towards presynaptic membrane

Question 6

Synapses Step 4

Answer 6

Vesicles fuse with membrane and release chemicals into synaptic cleft

Question 7

Synapses Step 5

Answer 7

Neurotransmitters diffuse across synaptic membrane. Known as a synaptic delay because it is slower than an electrical signal travels

Question 8

Synapses Step 6

Answer 8

Neurotransmitter binds to postsynaptic cell membrane’s receptor sites on sodium channels

Question 9

Synapses Step 7

Answer 9

Neurotransmitters open sodium channels in membrane causing sodium ions to pass in. Depolarises post synaptic membrane. When charge is big enough, an action potential is generated in second cell.

Question 10

Synapses Step 8

Answer 10

Any neurotransmitter left over is broken down by enzymes such as acetylcholine esterase and reabsorbed into the presynaptic membrane.

Question 11

Acetylcholine

Answer 11

Largely made in brain

Stimulation of muscles