Neurons 3

Question 1

What is synaptic transmission?

What are the 2 different ways?

Answer 1

The fast process of transferring info BETWEEN neurons or between neurons and muscle fibres

1. Chemical synapses (mostly occurs this way)
2. Electrical synapses (through gap junctions)

Question 2

How does a chemical synapse occur?

Answer 2

1. Depolarisation at the presynaptic terminal causes release of neurotransmitter
2. Neurotransmitter diffuses across synaptic cleft and binds to receptors in postsynaptic membrane
3. This initiates opening of a channel and a current in postsynaptic cell

Question 3

What are the 3 key features of chemical synapses?

Answer 3

1. Specificity: specific neurotransmitters have specific effects on postsynaptic membrane
2. Complexity: type, time, strength, location, etc.
3. Plasticity: changes in synaptic structure and function associated with development, learning, aging etc.

Question 4

What are neurotransmitters? (3)

Answer 4

• Chemical messengers that open/close ion channels
• Leading to de/hyperpolarisation of POSTsynaptic MEMBRANE
• Each neurotransmitter can bind to different types of receptors producing different effects on neuron function

Question 5

What is the postsynaptic membrane?

Answer 5

The membrane that receives the signal (binds neurotransmitter) from presynaptic cell

Question 6

What are excitatory postsynaptic potentials (EPSPs)? (4)

main type of chemical synapses in CNS/PNS

Answer 6

• Evoke DEpolarisation of the postsynaptic membrane
• Main neurotransmitters: glutamate, acetyl choline
• Opens channels for Na, K and sometimes Ca
• Shifts Vm from RMP TOWARDS threshold for AP generation

Question 7

What are inhibitory postsynaptic potentials (IPSPs)? (4)

main type of chemical synapses in CNS/PNS

Answer 7

• Evoke HYPERpolarisation of the postsynaptic membrane
• Main neurotransmitters: GABA, glycine
• Opens K channels
• Shifts RMP AWAY from threshold

Question 8

What is direct gating? (2)

Answer 8

• Transmitter binds to receptor/ion channel complex causing pore to open
  (Fast, short lasting)

Question 9

What is indirect gating? (4)

Answer 9

• Transmitter binds to receptors (eg. GPCR) activating G-protein pathway
• Leads to production of second messengers (eg. cAMP)
• Activates protein kinases, phosphorylating ion channel
  (Slower, longer lasting)

Question 10

What are small molecule (‘classical’) neurotransmitters?

What are the common types? (3)

Answer 10

Usually fast, acting directly on postsynaptic receptors.
Common types:
- Amino acids (glutamate, GABA, glycine)
- ACh
- Biogenic amines (dopamine, norepenephrine, serotonin)

Question 11

What are neuropeptides/neuromodulators?

What are the common types?

Answer 11

• Large molecule chemical messengers - indirect/metabotropic or modulatory action on effects of other neurotransmitters
• Slow, diffuse action
• Enkeophalin, substance P, neuropeptide Y

Question 12

What are the 3 steps in neurotransmitter inactivation/recovery?

Answer 12

1. Diffusion: neurotransmitters removed from synaptic cleft by diffusion
2. Enzymatic degradation: different enzymes degrade different types of neurotransmitters
3. Re-uptake/recycling: different forms of transporters remove + move to storage

Question 13

What is excitotoxicity?

Answer 13

The pathological process by which nerve cells are damaged or killed by excessive stimulation by neurotransmitters such as glutamate

Question 14

What is spatial summation?

Answer 14

Excitatory potentials from MANY NEURONS trigger threshold point

Question 15

What is temporal summation?

Answer 15

Many excitatory potentials from ONE NEURON triggers threshold point