Synapses and neurotransmitters

Question 1

What is a synapse?

Answer 1

A junction between 2 neurons that allows signals to pass from one to the other

Question 2

What is synaptic transmission?

Answer 2

The process of signalling via synpases

Question 3

What allows specialisation and flexibility in the brain?

Answer 3

Synapses

Question 4

What are electrical synapses formed of?

Answer 4

Gap junctions that allow ions and small molecules to pass through

Question 5

What is a gap junction formed from?

Answer 5

Connexins form a connexon
- Connexons fit together to open a hole in the middle

Question 6

What are electrical synapses good for?

Answer 6

Synchronising neurons
Fast communication

Question 7

What happens in an active zone?

Answer 7

Vesicles fuse membrane and release content

Question 8

What is the post synaptic cell for a motor neuron?

Answer 8

Skeletal muscle

Question 9

What is the post synaptic cell for an autonomic neuron?

Answer 9

Hormonal gland
Smooth muscle
Heart

Question 10

What are the steps for chemical synaptic transmission?

Answer 10

1. Neurotransmitters are packaged into vesicles in the presynaptic cleft
2. The action potential causes voltage gated Ca2+ channels to open
3. An influx of Ca2+ enters the cleft -> The vesicles fuse with the presynaptic membrane and the neurotransmitters are released
4. Neurotransmitters diffuse and bind onto receptors on the postsynaptic cleft
5. Remaining neurotransmitters are cleared from the cleft

Question 11

What are the 2 types of synaptic vesicle?

Answer 11

Secretory granules
Synaptic vesicles

Question 12

What is the difference between secretory granules and synaptic vesicles?

Answer 12

SV are smaller and appear clear on electron microscope. Can be recycled.
SG are filled with peptides at the Golgi and have to be transported to the presynaptic vesicle.

Question 13

How does a vesicle fuse with plasma membranes?

Answer 13

Ca2+ channels release Ca2+ ->
Ca2+ binds to Synaptotagmin causing a conformational change ->
V and T snares “zipper together” ->
This forces lipid bilayer to fuse with the lipid bilayer of the plasma membrane

Question 14

How are neurotransmitters removed from the cleft?

Answer 14

1. Diffusion
2. Actively taken up into presynaptic neuron or glia by transporters for recycling
3. They are destroyed in the synaptic cleft by enzymes

Question 15

Which direction do electrical signals pass in?

Answer 15

Both directions

Question 16

Which direction can chemical signals pass in?

Answer 16

One direction

Question 17

What is the fastest synaptic signal?

Answer 17

Electrical

Question 18

What synapses are “plastic”?

Answer 18

Chemical and electric

Question 19

Function of a neuromuscular junction

Answer 19

Fast and reliable neurotransmission

Question 20

What do motor neuron action potentials always cause?

Answer 20

Muscle cell action potentials

Question 21

What neurotransmitter is associated with a neuromuscular junction?

Answer 21

Acetylcholine

Question 22

What is a neuromuscular junction?

Answer 22

A synaptic connection between the terminal end of a motor neuron and a muscle cell

Question 23

What is the specialisation of the presynaptic neuromuscular junction?

Answer 23

Large number of active zones

Question 24

What is the specialisation of the postsynaptic neuromuscular junction?

Answer 24

Contains junctional folds which are densely filled with neurotransmitter receptors

Question 25

What is precisely aligned in the neuromuscular junction?

Answer 25

Active zones and junctional folds

Question 26

What are the 5 different types of CNS synapses?

Answer 26

Dendrosomatic
Dendrodentritic
Axosomatic
Axodendritic
Axonaxonic