synaptic transmission

Question 1

what happens when an action potential reaches the end of the neurone

Answer 1

When an action potential arrives at the e n d o f a neurone, the information has to be passed on to the next cell
— this could be another neurone, a muscle cell or a gland cell

Question 2

what is a synapse

Answer 2

A synapse is the junction between a neurone and another neurone,
or between a neurone and an effector cell, e.g. a muscle or gland cell.

Question 3

what is a synaptic cleft

Answer 3

The tiny gap between the cells at a synapse is called the synaptic cleft.

Question 4

what is a presynaptic neurone

Answer 4

a neurone before the synapse

Question 5

what do presynaptic neurones contains

Answer 5

s a swelling
called a synaptic knob. This contains synaptic vesicles filled with
chemicals called neurotransmitters.

Question 6

what happens when an action potential reaches the end of a neurone

Answer 6

it
causes neurotransmitters to be released into the synaptic cleft.
They diffuse across to the postsynaptic membrane (the one
after the synapse) and bind to specific receptors.

Question 7

what happens when neurotransmitters bind to receptors

Answer 7

When neurotransmitters bind to receptors they might trigger an
action potential (in a neurone), cause muscle contraction
(in a muscle cell), or cause a hormone to be secreted (from a gland cell)

Question 8

why does the impulse only travel in one direction (undirectional)

Answer 8

Because the receptors are only on the postsynaptic membranes, synapses make
sure impulses are unidirectional — the impulse can only travel in one direction.

Question 9

why are neurotransmitters removed from the cleft

Answer 9

Neurotransmitters are removed from the cleft so the response doesn’t keep happening ,e.g. they’re taken back
into the presynaptic neurone or they’re broken down by enzymes (and the products are taken into the neurone).

Question 10

what ends with “ine”

Answer 10

neuro transmitters

Question 11

what are examples of some neurotransmitters

Answer 11

) There are many different neurotransmitters, e.g. acetylcholine (ACh) and noradrenaline.

Question 12

what are cholinergic synapses

Answer 12

Synapses that use

acetylcholine are called cholinergic synapses.

Question 13

what are all the constituents of a synapse

Answer 13

synaptic knob, post synaptic membrane, presynaptic membrane, synaptic cleft, receptors, vesicle filled with neurotransmitters

Question 14

what does ACh transmit

Answer 14

ACh Transmits the Nerve Impulse Across a Cholinergic Synapse

Question 15

what is step 1 of a nerve impulse transmitting across a cholinergic synapse

Answer 15

An action potential arrives

at the synaptic knob of the presynaptic neurone

Question 16

what is step 2 of a nerve impulse transmitting across a cholinergic synapse

Answer 16

The action potential stimulates voltage-gated calcium

ion channels in the presynaptic neurone to open.

Question 17

what is step 3 of a nerve impulse transmitting across a cholinergic synapse

Answer 17

Calcium ions diffuse into the synaptic knob.

They’re pumped out afterwards by active transport.

Question 18

what is step 4 of a nerve impulse transmitting across a cholinergic synapse

Answer 18

The influx of calcium ions into the synaptic
knob causes the synaptic vesicles to move
to the presynaptic membrane. They then
fuse with the presynaptic membrane.

Question 19

what is step 5 of a nerve impulse transmitting across a cholinergic synapse

Answer 19

The vesicles release the neurotransmitter
acetylcholine (ACh) into the synaptic cleft
— this is called exocytosis

Question 20

what is step 6 of a nerve impulse transmitting across a cholinergic synapse

Answer 20

ACh diffuses across the synaptic cleft and binds to specific

cholinergic receptors on the postsynaptic membrane.

Question 21

what is step 7 of a nerve impulse transmitting across a cholinergic synapse

Answer 21

This causes sodium ion channels in the

postsynaptic neurone to open.

Question 22

what is step 8 of a nerve impulse transmitting across a cholinergic synapse

Answer 22

The influx of sodium ions into the postsynaptic membrane
causes depolarisation. An action potential on the postsynaptic
membrane is generated if the threshold is reached.

Question 23

what is step 9 of a nerve impulse transmitting across a cholinergic synapse

Answer 23

ACh is removed from the synaptic cleft so the response doesn't
keep happening. It's broken down by an enzyme called
acetylcholinest erase (AChE) and the products are re-absorbed
by the presynaptic neurone and used to make more ACh