2.2 Synaptic Transmission, Neurotransmitters and Pharmacology of Synaptic Transmission

Question 1

What’s a synapse?

Answer 1

a point of specialised contact between two neurons
- usually a process from one neuron contacts a receiving area from another neuron

Question 2

What are purkinjie cells?

Answer 2

• neuron unique to cerebellum, with huge dendritic treds

Question 3

What are the three aspects of a synapses structure?

Answer 3

1. presynaptic element (terminal bouton)
2. synaptic cleft (physical gap)
3. postsynaptic element

Question 4

What is a presynaptic element?

Answer 4

• end of an axon
• contains vesicles (lipid bilayer)
• contains neurotransmitters

Question 5

What is the synaptic cleft?

Answer 5

small physical gap (20-4-nm)

Question 6

What can a post synaptic element be?

Answer 6

1. a dendrite
2. a cell body
3. a terminal bouton

Question 7

How do synapses work (brief explanation)?

Answer 7

• neurotransmitter is synthesised and stored in a vesicle
• they are released by pre-synaptic activation
• binds to receptors on post synaptic membrane
• then is inactivated: either taken back up/drifts back from synapse/tear apart

Question 8

What happens when an action potential reaches the presynaptic element?

Answer 8

calcium channels in active zones open and calcium floods into the cell

Question 9

How quickly is action potential to secretion?
How quickly is diffusion across the synapse?

Answer 9

1. under 200 .s
2. 1-2 ms

Question 10

What is synaptotagmin?

Answer 10

vesicle membrane protein which may act as a calcium sensor
- may be involved in docking

Question 11

What is syntaxin?

Answer 11

plasma membrane protein involved in fusion

Question 12

What is SNAP-25?

Answer 12

plasma membrane protein involved in fusion

Question 13

What are receptors and neurotransmitters often likened to?
How is this analogy extended?

Answer 13

lock and key
- once unlocked, the neurotransmitter allows a door (channel) to be opened to inside of the cell

Question 14

What are the two types of receptor?

Answer 14

1. ionotropic
2. metabotropic

Question 15

What is an ionotropic receptor?

Answer 15

• directly associated with an ion channel (ion channels activate them)
• made of subunits (usually 5)

Question 16

What is a metabotropic receptor?

Answer 16

• indirectly associated with an ion channel
• instead, associated with signal proteins and G proteins
• a ‘biochemical cascade’ links the receptor to an ion channel
• do not consist of subunits

Question 17

Why does a cell have a membrane resting potential?

Answer 17

certain ions e.g sodium are unevenly distributed on the two sides of the membrane

Question 18

What makes a cell more likely to fire an action potential?

Answer 18

excitatory neurotransmitter

Question 19

What makes a cell less likely to fire an action potential?

Answer 19

inhibitory neurotransmitter

Question 20

What is inactivation?

Answer 20

• resets synapse
• neurotransmitter removed from the synaptic cleft either by active transport or reuptake
• can also be by diffusion, glial cells or enzymes

Question 21

What are the ways in which drugs interfere with transmission?

Answer 21

1. cause a release of neurotransmitter
2. mimicking the action
3. blocking the action
4. blocking reuptake