SYNAPSE

Question 1

Synapse

Answer 1

synapse is a junction between two neurones or between a neurone and an effector cell.

Question 2

function or mechanism of synapse

Answer 2

1. action potential arrives at the synaptic knob which causes depolarisation leading to calcium ion channels to open, so more calcium ion diffuse into the synaptic knob.
2. vesicles containing neurotransmitter moves on and fuses with the pre synaptic membrane releasing the neurotransmitgters into the synaptic cleft.
3. neurotransmitters diffuses down their conc gradient across the synaptic cleft to the post synaptic neurone where they bind with complemntary receptors.
4. sodium ion channels in the post synaptic membrane opens and sodium ion diffuses in, if enough neurotransmitter diffuses more sodium ion diffuses above threshold which makes the post synaptic neurone depolarised.
5. neurotransmitters are removed from the cleft so the reaction doesnt keep happening or they are broken down by enzymes.
6. sodium ion channels close and the neurone can re establish resting potential.

Question 3

cholinergic synapse

Answer 3

synapses that uses acetyl choline are called choinergic synapse.

Question 4

mechanism of cholinergic synapse

Answer 4

1. action potential arrives at the synaptic knob - stimulates voltage gated calcium ion channels to open - calcium ions diffuses into the synaptic knob.
2. influx of calcium ion causes vesicles to move forward and fuse with the pre synaptic membrane to release the neurotransmitter acetyl choline into the synaptic cleft. this process is called exocytosis.
3. ACh diffuses across the synaptic cleft and binds to cholinergic receptors on the post synaptic neuron - causing sodium ion channels to open – influx of sodium ions leading to depolarisation– an action potential generated if the threshold is reached -
4. ACh is removed from the synaptic cleft - broken down by an enzyme acetylcholinesterase (AChe) and products are reabsorbed in the pre synaptic neuron.

Question 5

excitatory neurotransmitters

Answer 5

excitatory neurotransmitters depolarises the post synaptic membrane making it fire an action potential if the threshold is reached.
ACh is an excitatory neurotransmitter in the cholinergic synapse - binds to cholinergic receptors to cause an action potential.

Question 6

inihibitory neurotransmitter

Answer 6

inhibitory neurotransmitter hyper polarises the post synaptic membrane ( making the potential diff more negative) preventing it from firing an action potential.
ACh is an inhibitory neurotransmitter in heart during a cholinergic synapse, whennit binds to receptors it causes potassium ion channel to open hyperpolarising it.

Question 7

summation

Answer 7

summation is the rapid build up of neurotransmitters in the synapse to help generate an action potential.

Question 8

types of summation

Answer 8

spatial and temporal summation

Question 9

spatial summation

Answer 9

many neurones connect to one neuron - small amt of neurotransmitter released by each neuron can be enough altogether to reach threshold in post synaptic neuron and generate an action potential

Question 10

temporal summation

Answer 10

two or more nerve impulses arrive in quick succession from the same pre synaptic neuron - more neurotransmitters are released - action potential likely to happen.