Neurotranmission

Question 1

What is dendritic aborization and why is it important for neuronal function?

Answer 1

Dendritic aborization is the branching out of dendrites. It is important as it allows for dendrites to make new synaptic connects.

Question 2

What is the Neuromuscular Junction?

Answer 2

It is a specialised synapse between an α-motor neuron and a muscle fibre at the motor end plate.

Question 3

What is muscle atrophy and how does it come about?

Answer 3

It is the decrease in the mass of the muscle (as seen in motoneuron diseases) and is cause by denervation.

Question 4

What are Excitatory Post-Synaptic potentials (EPSPs)?

Answer 4

They are potentials that cause the depolarisation of the post-synaptic membrane.

Question 5

What are Inhibitory Post-Synaptic Potentials (IPSPs)?

Answer 5

They are potentials that hyperpolarize the post-synaptic membrane.

Question 6

What causes the generation of EPSPs and IPSPs?

Answer 6

EPSPs = An increase in Na+ or Ca2+ permeability.

IPSPs = An increase in Cl- or K+ permeability.

Question 7

What determines the final post-synaptic cellular response of the EPSPs and IPSPs?

Answer 7

Synaptic integration and Summation.

Question 8

What are the 4 criteria that a molecule needs to meet in order to be considered a neurotransmitter?

Answer 8

1) It should be synthesised in the neuron.
2) It should be present in the presynaptic terminal.
3) There should be a specific mechanisms for removing it the synaptic cleft.
4) When applied exogenously it should mimic exactly the action of the endogenously released transmitter.

Question 9

Which 3 amino acids act as neurotransmitters?

Answer 9

Glutamate, GABA (gamma-aminobutyric acid) and glycine.

Question 10

What other molecules aside from biogenic amines and amino acids can act as neurotransmitters?

Answer 10

ATP and adenosine, and nitric oxide (NO-)

Question 11

Which 6 biogenic amines act as neurotransmitters?

Answer 11

Acetylcholine, Noradrenaline, Adrenaline, Dopamine, Serotonin (5-HT), Histamine.

Question 12

What is acetylcholine synthesised from and Where?

Answer 12

It is synthesized from Choline and acetyl CoA in the pre-synaptic terminal.

Question 13

Which two receptor types for Acetylcholine act on?

Answer 13

It acts on Nicotinic (ligand-gated ion channels) and Muscarinic (G-protein coupled) receptors.

Question 14

What is noradrenaline synthesised from and where?

Answer 14

It is synthesised from tyrosine in the post-synaptic membrane.

Question 15

What are the two receptor types that Noradrenaline acts on?

Answer 15

α-adrenergic receptors and β-adrenergic receptors.

Question 16

What are α-adrenergic receptors and what does the activation of the two subtypes result in?

Answer 16

They are G-protein coupled receptors.

α1 activation results in Ca2+ release.
α2 activation results in inhibition of adenylate cyclase.

Question 17

What are β-adrenergic receptors and what their activation result in?

Answer 17

They are G-protein coupled receptors.

They activation results in activation of adenyl cyclase, and thus an increase in cAMP

Question 18

How does the drug Amphetamine work in Noradrenergic synpases?

Answer 18

it works by blocking the re-uptake of Noradrenaline from the synaptic cleft so that the effect of NA is prolonged.

Question 19

What are the effects of Muscarine and Atropine on the heart?

Answer 19

Muscarine slows the heart rate.

Atropine blocks the actions of muscarine and the vagus nerve, preventing the lowering of the heart rate.

Question 20

What are the effects of Nicotine and Curare on the skeletal muscles?

Answer 20

Nicotine stimulates contraction of skeletal muscle.

Curare blocks the action of nicotine at the NMJ and prevents the contraction of the skeletal muscle.

Question 21

How does stimulation of the vagus nerve cause the heart rate to slow down?

Answer 21

Stimulation of the vagus nerve causes the release of the substance Vagusstoff, which slows the heart rate down.

Question 22

What is the effect of a bacterial infection that leads to the release of the Tetanus toxin on the muscle?

Answer 22

It causes an increase in muscle contraction as it works on inhibitory neurons to prevent the fusion of vesicles with the pre-synaptic membrane.

Question 23

What is the effect of the nerve gas ‘Sarin’ on the muscle?

Answer 23

It causes uncontrolled muscle contraction by inhibiting the action of acetylcholinesterase.

Question 24

What is the effect of the Toxin ‘Tetrodotoxin’ on the muscle?

Answer 24

It prevents muscle contraction by binding to sodium-channels. , which thus prevents the formation of action potentials.

Question 25

Where are the 5 muscarinic receptors sub-types primarily found?

Answer 25

M1 = found in Neural cells.
M2 = found in Cardiac cells.
M3 = found in Glandular/smooth muscle cells.
M4 and M5 = found in the CNS.

Question 26

What are drugs that stimulate and inhibit muscarinic receptors called?

Answer 26

Drugs that stimulate muscarine receptors are called parasympathomimetics.

Drugs that inhibit these receptors are called parasympatholytics.