Excitatory & Inhibitory Neurotransmissions in the CNS

Question 1

What is the axon hillock responsible for?

Answer 1

Decides whether an action potential should be created - ‘All or nothing’ mechanism

Question 2

Do all neurons generate action potentials?

Answer 2

NO

Question 3

What causes upstroke of action potential?

Answer 3

Influx of sodium through voltage gated Na+ channels

Question 4

What causes the downstroke in an action potential?

Answer 4

The exit of K+ from the cell through voltage activated K+ channels

Question 5

How is ion selectivity relevant to an action potential?

Answer 5

When Na+ is entering, K+ cannot leave and visa versa

Question 6

Why is the cell membrane considered ‘leaky’?

Answer 6

Along the cell membrane there are pores, this means that the current can leak out

Question 7

How does a leaky membrane mean passive signals do not travel far?

Answer 7

This is due to current leaking out and therefore the amplitude reducing the further away from the origin it gets.

Question 8

How can current leakage be reduced?

Answer 8

Decreasing ri (possibly by increasing axon diameter), Increase rm (possibly by adding an insulating material I.e. myelin sheath)

Question 9

How does a myelin sheath effect conduction?

Answer 9

Conduction in a myelinated axon is much faster than in a non-myelinated axon of the same diameter

Question 10

What is rm?

Answer 10

Membrane resistance

Question 11

What is ri?

Answer 11

Axoplasmic resistance

Question 12

What does saltatory conduction mean?

Answer 12

Only occurs in myelinated axons, it is when the AP jumps from one node of ranvier to the other
(voltage activated Na+ channels cluster at nodes)

Question 13

What are the two types of neurotransmitter receptor?

Answer 13

Inotropic and metabotropic

Question 14

Which neurotransmitter receptor is responsible for direct gating?

Answer 14

Inotropic

Question 15

Which neurotransmitter receptor is responsible for indirect gating?

Answer 15

Metabotropic

Question 16

What is the mechanism on indirect gating?

Answer 16

G-protein coupled receptor triggers an associated channel within the membrane.

Question 17

Do inotropic receptors usually take an excitatory or inhibitory effect?

Answer 17

Excitatory

Question 18

Which of inotropic or metabotropic receptors have faster action?

Answer 18

Inotropic

Question 19

What are the two classifications of inotropic glutamate receptors?

Answer 19

NMDA (slow)
Non-NMDA (fast)

Question 20

NMDA controls channels permeable to what?

Answer 20

Na, Ca, K

Question 21

Non-NMDA controls channels permeable to?

Answer 21

Na, K

Question 22

Are GABA neurotransmitters inhibitory or excitatory?

Answer 22

Inhibitory

Question 23

Is GABAa Inotropic or metabotropic?

Answer 23

Inotropic
- Operates Cl- channel

Question 24

Is GABAb inotropic or metabotropic?

Answer 24

Metabotropic
- Often activates K+ channels

Question 25

What drugs enhance the effects of GABAa?

Answer 25

Benzodiazepines, Barbituates

Question 26

What drugs enhance the effects of GABAb?

Answer 26

Baclofen

Question 27

Are glycine neurotransmitters excitatory or inhibitory?

Answer 27

Inhibitory

Question 28

Do glutamate neurotransmitters have an excitatory or inhibitory effect?

Answer 28

Excitatory

Question 29

What is a Quanta?

Answer 29

Quanta are discrete packages that neurotransmitters are released in?

Question 30

How does calcium effect synaptic vesicles?

Answer 30

The larger the calcium influx into the cell, the more synaptic vesicles will be present.