neuromuscular junctions

Question 1

define neuromuscular junction

Answer 1

synapse between a neurone
& a skeletal muscle fibre.

Question 2

what 5 steps are involved in synaptic transmission at the neuromuscular junction

Answer 2

1) synthesis of neurotransmitter ( e.g. acetyl choline)
2) storage - protect then package neurotransmitter in vesicles
3) release into the synaptic cleft
4) Activation
5) inactivation ( via inactivating enzymes)

Question 3

what role does calcium ions play in synaptic transmission

Answer 3

Ca2+ binds to microtubules which causes movement, pushing vesicles towards membrane for release

Question 4

what enzyme breaks down acetyl choline

Answer 4

acetyl choline esterase

Question 5

how can drugs enhance synaptic transmission ?

Answer 5

1) Direct stimulation of post synaptic receptors by either the natural transmitter or analogues
2) indirect action by increased transmitter release or inhibition of transmitter removal

Question 6

how do drugs inhibit synaptic transmission?

Answer 6

1) blocking synthesis, storage or release from pre- synaptic neurone
2) blocking post synaptic receptor

Question 7

define agonist

Answer 7

drugs, hormones, or transmitters which bind to specific receptors and initiate a conformational change in the receptor resulting in a biological response.

Question 8

what are the two key properties of agonists

Answer 8

affinity and efficacy

Question 9

define affinity

Answer 9

ability of agonists to bind to receptors

Question 10

define efficacy

Answer 10

the ability of an agonist to initiate a biological response, once bound to a receptor

Question 11

the higher the affinity…

Answer 11

the lower the concentration of ligand required for an agonist receptor complex to form

Question 12

what do antagonists do

Answer 12

block receptor activation by agonists

Question 13

define competitive antagonist

Answer 13

competes with agonist for binding site on receptor blocking response

Question 14

Generally how is the effects of antagonists reversed

Answer 14

increased ligand concentration

Question 15

what is the general term for the receptors for which acetylcholine acts upon

Answer 15

cholinoceptors

Question 16

what are the two classes of cholinoceptors

Answer 16

1) Nicotinic cholinoceptors
2) Muscarinic cholinoceptors

Question 17

characteristics of Nicotinic cholinoceptors

Answer 17

• Activated by ACh or nicotine
• ligand gated
• conduct cations
• rapid - milliseconds

Question 18

characteristics of muscarinic cholinoceptors

Answer 18

• Activated by ACh or muscarine
• G protein coupled
• usually found in smooth muscle

Question 19

what technique is used to measure single ACh nicotinic receptors

Answer 19

patch-clamp technique which allows us to measure the ion conductance

Question 20

define motor end plate

Answer 20

the portion of the muscle-cell membrane that lies opposite the terminal of a nerve fibre at the neuromuscular junction.

Question 21

define end plate potential ( epp )

Answer 21

depolarization of motor end plate that leads to an action potential

Question 22

miniature end plate potential (mepp)

Answer 22

slight depolarization of motor end plate caused by a discrete vesicular release of neurotransmitter, too small to produce an action potential alone. summate to produce an end plate potential