Excitatory and inhibitory neurotransmission in the CNS

Question 1

Na+ channels.

Answer 1

Flow inwards.

• Depolarisation.
• Excitatory.

Question 2

Ca2+ channels.

Answer 2

Flow inwards.

• Depolarisation.
• Excitatory.

Question 3

Cl- channels.

Answer 3

Flow inwards.

• Hyperpolarisation.
• Inhibitory.

Question 4

K+ channels.

Answer 4

Flow outwards.

• Hyperpolarisation.
• Inhibitory.

Question 5

Na+ channel agonists act to cause?

Answer 5

Excitation.

Question 6

Na+ channel antagonists act to cause?

Answer 6

Inhibition.

Question 7

Give an example of a Na+ channel antagonist.

Answer 7

Local anaesthetics e.g. Lidocaine.

Question 8

K+ channel agonists act to cause?

Answer 8

Inhibition.

Question 9

K+ channel antagonists act to cause?

Answer 9

Excitation.

Question 10

Neuron structure can be divided into four morphological regions, which are?

Answer 10

• soma
• dendrites
• axon
• synapse

Question 11

What part of the neuron receives incoming signals?

Answer 11

Dendrites.

Question 12

What part of the neuron carries outgoing information?

Answer 12

Axons.

Question 13

What are the two major families of ligand-gated channels?

Answer 13

• Nicotinic, GABAa, Glycine receptors.

- Glutamate receptors.

Question 14

Glutamate is the major excitatory neurotransmitter but may also have inhibitory effects via its response at which receptors?

Answer 14

Metabotropic Glutamate receptors.

Question 15

How may Ionotropic glutamate receptors be classified?

Answer 15

Via their response to non-endogenous agonists mimicing glutamate.

• non-NMDA.
• NMDA

Question 16

Non-NMDA receptors bind what to control what?

Answer 16

Agonists Kainate or AMPA to control a channel permeable to Na+ and K+.

Question 17

NMDA receptors control what?

Answer 17

A channel permeable to Na+, Ca2+ and K+.

Question 18

Non-NMDA ionotropic receptors mediate what?

Answer 18

Fast excitatory synaptic transmission in the CNS.

Question 19

NMDA receptors contribute what to the excitatory synaptic potential?

Answer 19

The slow component.

Question 20

NMDA have a high permeability to what?

Answer 20

Ca2+.

Question 21

NMDA’s high Ca2+ permeability is thought to promote what?

Answer 21

Neurotoxicity.

Question 22

Ketamine and psychomimetric agents e.g. phencyclidine are selective blockers of what channels?

Answer 22

NMDA-operated channels.

Question 23

How do metabotropic glutamate receptors exert their effect as they do not have an integral ion channel?

Answer 23

Activation of a second messenger cascade.

Question 24

What is the role of metabotropic glutamate receptors?

Answer 24

Modulation of neurotransmission.

Question 25

Give an example of how metabotropic glutamate receptors modulate neurotransmission?

Answer 25

Presynaptic inhibtion e.g. inhibition of Ca2+ channels.

Question 26

What is the main inhibitory neurotransmitter in the CNS?

Answer 26

GABA.

Question 27

Which 2 types of receptors does GABA act on?

Answer 27

- Ionotropic GABAa receptor. | - Metabotropic GABAb receptor.

Question 28

An Ionotropic GABAa receptor operates what type of channel?

Answer 28

Cl- channel

Question 29

A Metabotropic GABAb receptor often activates what type of channel?

Answer 29

K+ channel.

Question 30

Benzodiazepines are what to GABAa receptors?

Answer 30

Positive allosteric modulators.

Question 31

Benzodiazepines act on GABAa receptors to do what?

Answer 31

- Enhance Cl- entry. - Decrease rmp. - Enhance inhibition in the presence of GABA.

Question 32

Barbituates have what effect at the GABAa receptor?

Answer 32

Potentiate the effect of GABA.

Question 33

Baclofen acts on the GABAb receptor as what?

Answer 33

An agonist to enhance the K+ current and thus increase inhibition.

Question 34

Glycine is an inhibitory neurotransmitter that acts on what receptor?

Answer 34

Glycine ionotropic receptor that gates a Cl- channel.

Question 35

What releases glycine?

Answer 35

Interneurones in the spinal cord to inhibit antagonist muscle motoneurones.

Question 36

Describe the speed of ionotropic receptor gating of ion channels?

Answer 36

Rapid

Question 37

Describe the speed of metabotropic receptor gating of ion channels?

Answer 37

Slow (-er than ionotropic).

Question 38

What action do metabotropic receptors typically have?

Answer 38

Modulatory synaptic actions.

Question 39

Metabotropic and ionotropic receptors act on channels in the presynaptic terminal to modulate what?

Answer 39

Transmitter release.

Question 40

Metabotropic and ionotropic receptors modulate transmitter-gated channels to regulate what?

Answer 40

The size of the post-synaptic potential.

Question 41

Metabotropic and ionotropic receptors modulate the resting and voltage-gated ion channels in the neuronal soma to alter what?

Answer 41

Resting Em and AP firing pattern.

Question 42

Cholinergic synaptic transmission in the autonomic ganglia display both what actions?

Answer 42

Direct and indirect.

Question 43

Fast EPSP is due to activation of what?

Answer 43

Nicotinic (ionotropic) ACh receptors - channels that conduct Na+ and K+.

Question 44

Slow EPSP follows activation of what?

Answer 44

Muscarinic receptros.

Question 45

What does EPSP stand for?

Answer 45

excitatory post synaptic potential

Question 46

What is EPSP?

Answer 46

Depolarising change in rmp due to excitatory neurotransmission.

Question 47

Multiple/very large EPSP may cause what?

Answer 47

RMP to cross threshold and result in an action potential.

Question 48

What is an inhibitory post synaptic potential (IPSP)?

Answer 48

Negative change in rmp due to inhibitory neurotransmitter release.

Question 49

What does IPSP inhibit?

Answer 49

rmp crossing threshold thus inhibiting an action potential.

Question 50

what is graded potential?

Answer 50

Change in rmp due to EPSP or IPSP.

Question 51

Changes in rmp due to EPSP/IPSP are caused by what?

Answer 51

Release of excitatory/inhibitory neurotransmitters.

Question 52

What receives the stimulus in a graded potential?

Answer 52

Cell body.

Question 53

The strength of a graded potential is determined by what?

Answer 53

How much charge enters the cell.

Question 54

Why does the strength of a graded potential diminish over distance?

Answer 54

Due to current leak and cytoplasmic resistance.

Question 55

What causes increase in amplitude of a graded potential?

Answer 55

Sodium entering.

Question 56

As amplitude of a graded potential increases, what happens to the spread of signal?

Answer 56

It goes further.

Question 57

What is the result of a graded potential that does not go beyond threshold at the trigger zone?

Answer 57

No action potential will be generated.

Question 58

What is glutamate?

Answer 58

The major excitatory neurotransmitter.

Question 59

What does glutamate act on?

Answer 59

Ionotropic receptrs to allow Na+ and Ca2+ in, and K+ out of the cell.

Question 60

What is the net result of Glutamate's action?

Answer 60

- EPSP. - Depolarisation. Excitation.

Question 61

What is GABA?

Answer 61

The major inhibitory neurotransmitter.

Question 62

What does GABA act on?

Answer 62

Ionotropic receptors to allow Cl- into the cell.

Question 63

What is the net result of GABA's action?

Answer 63

- IPSP. - Hyperpolarisation. - Inhibition.

Question 64

What is an interneurone?

Answer 64

A locally acting neurone that typically releases GABA.

Question 65

What is the function of an interneurone?

Answer 65

- GABA release brings about an IPSP and inhibition. | - Function is local processing of information.

Question 66

What is a projection neuron?

Answer 66

A neuron responsible for conveying signals to other parts of the brain.

Question 67

A projection neurone typically release what?

Answer 67

Glutamate to bring about an EPSP.

Question 68

Excitatory neurones release what?

Answer 68

A depolarising neurotransmitter e.g. glutamate.

Question 69

Glutamate is an example of what kind of neurotransmitter?

Answer 69

Depolarising/excitatory.

Question 70

GABA is an example of what kind of neurotransmitter?

Answer 70

Hyperpolarising/inhibitory.

Question 71

The influence of a synapse depends on what?

Answer 71

The distance the current has to travel to the neurones trigger zone.

Question 72

Neurotransmitter is released in discrete packages called what?

Answer 72

Quanta.

Question 73

A quanta refers to what/

Answer 73

The release of a neurotransmitter from a single vesicle.

Question 74

The number of quanta released varies with what?

Answer 74

The stimulus.

Question 75

Name a strategy to increase quantal release.

Answer 75

- Extensive innervation. | - Megahumongous presynapse.

Question 76

Give an example of extensive innervation to increase quantal release.

Answer 76

- Purkinje cell - Inferior Olivary Neuron Synapse. | - The inhibitory basket cell (common in cerebellum, hippocampus and cortex).

Question 77

Give an example of a megahumungous presynapse.

Answer 77

- Calyx of Held synapse.

Question 78

Describe the relationship between purkinje cells and parallel fibres.

Answer 78

A single Purkinje cell is contacted by approx. 400 parallel fibres. These fibres contact multiple Purkinje cells.

Question 79

Purkinje cells are innervated by parallel fibres and what else?

Answer 79

Climbing fibre.

Question 80

Activation of an excitatory input produces what?

Answer 80

A large EPSP at the trigger zone- initial segment. Cation selective channels Na+ and K+.

Question 81

Activation of an inhibitory input produces what?

Answer 81

A large IPSP at the initial segment (opens Cl- channels).

Question 82

Simultaneous activation of excitatory and inhibitory input results in what?

Answer 82

Reduced EPSP as the inhibitory input shunts the excitatory current.

Question 83

In the absence of inhibitory input, what happens to a spontaneously active neurone?

Answer 83

It discharges rhythmically.

Question 84

In the presence of inhibitory input, what happens to a spontaneously active neurone?

Answer 84

A distinct pattern of discharge.

Question 85

Summation of postsynaptic membrane potentials allows what?

Answer 85

Multiple synaptic inputs to be integrated.

Question 86

Describe spatial summation.

Answer 86

EPSPs and IPSPs are spatially distributed but timed together.

Question 87

Describe temporal summation.

Answer 87

EPSPs occur in temporal sequence to trigger threshold.