Excitatory and Inhibitory Neurotransmission

Question 1

What does an entry of +ve ions or an exit of -ve ions result in?

Answer 1

A positive change

Question 2

What does an exit of +ve ions or entry of -ve ions result in?

Answer 2

A negative change

Question 3

What do neurons regulate regarding transmitter discharge?

Answer 3

The timing and location by invoking the mechanisms of excitation and inhibition

Question 4

What occurs in the opening of Na channels?

Answer 4

Inward flow - depolarisation, excitatory

Question 5

What occurs in the opening of Ca channels?

Answer 5

Inward flow - depolarisation, excitatory

Question 6

What occurs in the opening of Cl channels?

Answer 6

Inward flow- hyperpolarisation, inhibitory

Question 7

What occurs in the opening of K channels?

Answer 7

Outward flow- hyperpolarisation, inhibitory

Question 8

Does a Na channel agonist cause excitation or inhibition?

Answer 8

Excitation

Question 9

Does a Na channel antagonist cause excitation or inhibition?

Answer 9

Inhibition

Question 10

Does a K channel agonist cause excitation or inhibition?

Answer 10

Inhibition

Question 11

Does a K channel antagonist cause excitation or inhibition?

Answer 11

Excitation

Question 12

What can inactivate neurotransmitters?

Answer 12

Enzymes

Question 13

What happens when neurotransmitters are returned to axon terminals?

Answer 13

Reuse, transported into glial cells

Question 14

How can neurotransmitters leave the synaptic cleft?

Answer 14

Diffusion

Question 15

In what two ways may neurotransmitters act on ion channels?

Answer 15

Directly or indirectly

Question 16

What is direct gating carried out by?

Answer 16

Ionotropic receptors

Question 17

What is indirect gating mediated by?

Answer 17

Activation of metabotropic receptors

Question 18

What is a key feature of an ionotropic receptor?

Answer 18

Receptor is an integral component of the molecule that forms the channel it controls

Question 19

What is significant about metabotropic receptors and the channel it controls?

Answer 19

They are distinct

Question 20

Which ligand-gated channels are pentamers?

Answer 20

GABAa, Glycine and ACh (nicotinic) channels

Question 21

Which ligand-gated channels are tetramers?

Answer 21

Glutamate channels

Question 22

How can ionotropic glutamate receptors be classified?

Answer 22

Via their response to non-endogenous agonists that mimic glutamate

Question 23

What do non-NMDA receptors do?

Answer 23

Bind the agonists kainate or AMPA controlling a channel permable to Na+ and K+. Mediate fast excitatory transmission

Question 24

What do NMDA receptors do?

Answer 24

Control a channel permeable to Na+, Ca2+ and K+. Contribute a slow component to the excitatory synaptic potential

Question 25

Why are NMDA receptors thought to promote neurotoxicity?

Answer 25

High permeability to Ca2+

Question 26

What 2 receptors does GABA act on?

Answer 26

Ionotropic GABAa receptor (Cl- channel) and metabotropic GABAb receptor (K+ channel)

Question 27

What is benxodiazepines moa?

Answer 27

Positive allosteric modulator of the GABAa receptor so enhance Cl entry, decrease rmp, and enhance inhibition in presence of GABA

Question 28

What are barbiturates moa?

Answer 28

Similar to benzos and potentiates the effect of GABA at the GABAa receptor

Question 29

What is Baclofen's moa?

Answer 29

Agonist of the GABAb receptor so enhances the K current (and increase inhibition)

Question 30

What is glycine released by in the spinal cord?

Answer 30

Interneurones to inhibit antagonist muscles motoneurones

Question 31

What do ionotropic channels function as?

Answer 31

On-off switches

Question 32

Which receptor gating of ion channels if faster?

Answer 32

Ionotropic (ms), metabotropic is slower (tens of ms)

Question 33

What kind of action do metabotropic receptors have?

Answer 33

Modulatory synaptic actions

Question 34

What are some modulatory actions of metabotropic receptors?

Answer 34

Acting on channels in presynaptic terminal to modulate transmitter release, modulating transmitter-gated channels to regulate the size of the post synaptic potential, modulate resting and voltage-gated ion channels in the neuronal soma to alter resting Em and AP firing pattern

Question 35

What is a fast EPSP due to?

Answer 35

Activation of nicotinic (ionotropic) ACh receptors. Channels conduct Na+ and K+

Question 36

What does a slow EPSP follow?

Answer 36

Activation of muscarinic (GPCR) ACh receptors. ACh closes a K+ channel (M-type)

Question 37

What is the EPSP?

Answer 37

A depolarizing change in rmp caused by the actions of excitatory neurotransmission. Multiple EPSPs or very large EPSPs can cause rmp to cross threshold and result in an Action Potential (AP)

Question 38

What is the IPSP?

Answer 38

Negative change in rmp caused by release of an inhibitory neurotransmitter. Inhibits crossing of the threshold and inhibits AP.

Question 39

What is the graded potential?

Answer 39

A change in the rmp caused by an EPSP or IPSP, such a change is caused by (inhibitory or excitatory) neurotransmitter release and is not of a magnitude large enough to cross threshold and result in an AP

Question 40

What increases the amplitude of the graded potential, and what does this mean?

Answer 40

Sodium entry, the higher the amplitude the further the spread of signal

Question 41

What is an interneurone?

Answer 41

A locally-acting neurone, typically releases GABA and so brings about an IPSP and inhibition, function is local processing of information

Question 42

What are neurotransmitters released in?

Answer 42

Discrete packages called quanta

Question 43

What are some strategies to increase quantal release?

Answer 43

Extensive innervation, mega humongous presynapse