Physiology 3: Excitatory and Inhibitory Neurotransmission in the CNS

Question 1

normal resting mP of a neuron?

Answer 1

-70mV

Question 2

depolarisation or excitation will cause what effect on the resting mP of a neuron?

Answer 2

will increase

Question 3

normal resting mP of a depolarised neuron (more + ions)?

Answer 3

-40mV

Question 4

hyperpolarisation will have what effect on the neuron’s restign mP?

Answer 4

will decrease

Question 5

what would cause hyperpolarisation?

Answer 5

exit of + ions

entry of - ions

Question 6

which is the only main ion in which its external conc is lower than its intracellular conc? as a result of this, what effect will it have on a neuron’s mP?

Answer 6

K+
will cause hyperpolarisation as the high intracellular conc will flow outwards out of the cell rather than the low extracellular conc moving in

Question 7

what effect will a Cl- influx have on the cell/

Answer 7

will cause hyperpolarisation as you are adding a negative ion

Question 8

what effect does a K agonist have?

Answer 8

opens K channel to let K+ OUT causing inhibition

Question 9

what effect will a K+ antagonist have?

Answer 9

closes K channel to retain K+ in the cell, increasing cell mP

Question 10

a synapse is made up of what 3 components?

Answer 10

presynaptic axon terminal
synaptic cleft
postsynaptic dendrite

Question 11

what happens at a neuron’s axon terminal?

Answer 11

an AP depolarises

Question 12

what happens after a neuron depolarises?

Answer 12

1. voltage gated Ca channels open and Ca enters the cell

2. triggers exocytosis of synaptic vesicle contents

Question 13

once neurotransmitter is released from the synaptic vesicle where does it go?

Answer 13

diffuses across the synaptic cleft and binds to receptors on the postsynaptic dendrite causing a response

Question 14

name 4 ways in which neurotransmitters can be switched off

Answer 14

1. by enzymes
2. returned to axon terminals for reuse
3. transported into glial cells
4. by diffusing out of synaptic cleft

Question 15

direct gating is done by which receptors?

Answer 15

ionotropic

Question 16

indirect gating is mediated by activation of which receptors?

Answer 16

metabotropic

Question 17

give examples of receptors that are ligand gated

Answer 17

GABAa
glycine
ACh
glutamate

Question 18

glutamate receptor channels are __mers

Answer 18

tetra

Question 19

GABAa, glycine and Ach channels are __mers

Answer 19

penta

Question 20

name the major excitatory neurotransmitter

Answer 20

glutamate

Question 21

name the 2 kinds of ionotropic glutamate receptors

Answer 21

non-NMDA

NMDA

Question 22

which ionotropic glutamate receptor mediates fast excitatory synaptic transmission in the CNS?

Answer 22

non-NMDA

Question 23

which ionotropic glutamate receptor mediates the slow component of the excitator AP

Answer 23

NMDA

Question 24

what kind of glutamate receptor is particularly permeable to Ca? why is this problematic?

Answer 24

NMDA receptors

promotes neurotoxicity

Question 25

how do metabotropic glutamate receptors work?

Answer 25

activate a secondary messenger cascade

Question 26

main inhibitory neurotransmitter in the CNS?

Answer 26

GABA

Question 27

ionotropic GABA receptors operate what channel?

Answer 27

Cl

Question 28

GABAb activates a _ channel

Answer 28

K+

Question 29

what drugs enhance inhibition of neurotransmitters by allosterically binding to GABAa

Answer 29

benzodiazepines | barbiturates

Question 30

are ionotropic or metabotropic receptors faster?

Answer 30

ionotropic

Question 31

____ receptors can close as well as open ion channels

Answer 31

metabotropic

Question 32

how do metabotropic receptors trigger an AP if they're too slow to do so?

Answer 32

have modulatory synaptic actions that can trigger it

Question 33

nicotinic Ach receptors follow the metabotropic pathway T or F

Answer 33

F, follow the ionotropic pathway so are fast

Question 34

muscarinic (aka g-protein coupled) Ach receptors follow the metabotropic pathway T or F

Answer 34

T

Question 35

what branch of receptors follow the metabotropic pathway as a rule

Answer 35

G protein coupled receptors

Question 36

afferent input to a neurons can also be called the...

Answer 36

EPSP (excitatory postsynaptic potential)

Question 37

define the EPSP

Answer 37

a depolarising (+) change in the rmp caused by the actions of excitatory neurotransmission

Question 38

excitatory should make you think...

Answer 38

positive

Question 39

inhibitory should make you think...

Answer 39

negative

Question 40

define the IPSP

Answer 40

negative change in the rmp cause by the release of an inhibitory neurotransmitter -> inhibits the AP

Question 41

what is the graded potential?

Answer 41

a change in the rmp of a neuron caused by either an EPSP or an IPSP which is too small to reach threshold

Question 42

amplitude of a graded potential increases as more __ enters

Answer 42

Na

Question 43

what is an interneurone?

Answer 43

a locally acting neurone that releases GABA and thus causes inhibition

Question 44

what is a projection neuron? does it bring about an EPSP or IPSP?

Answer 44

a neuron responsible for conveying signals to other parts of the brain EPSP as releases glutamate

Question 45

the influence of a synapse depends on..

Answer 45

the DISTANCE the current has to travel to the neuron's trigger zone

Question 46

what is a quanta?

Answer 46

a secretory vesicle filled with neurotransmitter

Question 47

is there a pattern to which a neurone discharges its charge?

Answer 47

yes, it does so rhythmically unless it is under the influence of an IPSP