Lecture 3: Modulation of Membrane Potential

Question 1

What are the two different types of synapses?

Answer 1

chemical and electrical

Question 2

How do ligand-gated ion channels work?

Answer 2

neurotransmitter binds -> channel opens -> ions flow across membrane

Question 3

How do GPCRs work?

Answer 3

neurotransmitter binds -> G-protein is activated -> G-protein subunits or intracellular messengers modulate ion channels -> ion channel opens -> ions flow across membrane

Question 4

Are ionotropic receptors fast or slow?

Answer 4

fast

Question 5

Are metabotropic receptors fast or slow?

Answer 5

slow

Question 6

What are the different types of neurotransmitter?

Answer 6

acetylcholine, amino acids, purines, catecholamines, indoleamines, imidazoleamines and peptides

Question 7

What are the three main classes of ionotropic receptors and what is their division based upon?

Answer 7

AMPA, NMDA and kainate

divided into families based on their pharmacology

Question 8

What is the subunit of a receptor determined by?

Answer 8

genes

Question 9

What are the features of a receptor subunit?

Answer 9

amino terminus and carboxy terminus

transmembrane spanning domain

Question 10

What do multiple receptor subunits form?

Answer 10

a pore / channel

Question 11

How can different receptors be made?

Answer 11

different combinations of receptor subunits

Question 12

What is the nature of AMPA channels? Will more sodium or potassium initially pass through these channels?

Answer 12

non-selective cation channels which allow equal passage of sodium and potassium -> initially larger proportion of sodium moving through the channel

Question 13

What is the nature of NMDA channels?

Answer 13

glutamate binding to NMDA receptor opens a channel that transmits Ca2+, Na+ and K+

Question 14

What are glutamate ion channels made up of?

Answer 14

subunits which have three membrane-spanning domains and a re-entrant loop
most models predict four subunits making up an ion channel

Question 15

How is glutamate removed from the synaptic cleft?

Answer 15

EATTs present on astrocytes transport glutamate into the cell to that it can be converted to glutamine and inactivated -> glutamine is then taken up by EATTs present on the presynaptic terminal and converted back to glutamate

Question 16

Are acetylcholine receptors ionotropic or metabotropic?

Answer 16

both
nicotinic receptor = ionotropic
muscarinic receptor = metabotropic

Question 17

What are nicotinic receptors important for?

Answer 17

somatic movement

Question 18

How is acetylcholine inactivated?

Answer 18

acetylcholinesterase breaks down ACh to acetate and choline

Question 19

What are nicotinic receptors and what are they made up of?

Answer 19

non-selective cation channels

they are made of pentamers of four transmembrane spanning domains

Question 20

What are gap junctions composed of and what do they enable?

Answer 20

molecules such as connexins

electrical synapses

Question 21

How do electrical synapses work?

Answer 21

enable direct passage of ions between neurons -> this ionic movement alters the postsynaptic membrane potential

Question 22

Is there such thing as mixed synapses?

Answer 22

yes

Question 23

What are ionotropic receptors made of?

Answer 23

collections of protein subunits that interact to form a pore

Question 24

What is the effect of opening a non-selective ion channel dependent on?

Answer 24

the membrane potential and the transmembrane ion concentrations