CAL 1

Question 1

What does a cell body of a neurone consist of

Answer 1

perikaryon and a nucleus.

Question 2

where in the neurone is the site of protein synthesis

Answer 2

the cell body

Question 3

What does the cell body of the pre-synaptic neurone give rise to

Answer 3

the cell body of the pre-synaptic neurone gives rise to dendrites (apical and basal) and an axon

Question 4

where does the axon arise from

Answer 4

the axon hilliock

Question 5

what is an IPSP

Answer 5

this is an inhibitory post synaptic potential

Question 6

where do inhibitory inputs synapse onto

Answer 6

inhibitory inputs commonly synapse onto the cell body (axosomatic synapses) or the axon (axoaxonic synapses).

Question 7

what does an IPSP do that inhibits the action potential

Answer 7

Activation of an inhibitory input generates a graded hyperpolarization this means that the neurone cannot depolarise to reach the threshold point in order to generate an action potential

Question 8

What is the major role of the apical dendrites

Answer 8

receive excitatory input from other nerve cells

Question 9

what does an EPSP do

Answer 9

this is an excitatory post synaptic potential

- it causes depolarisation and generates an excitatory input

Question 10

what happens at the axon hilliock in order to generate an action potential

Answer 10

• in order to generate an action potential there is summation at the axon hillock which eventually leads to the threshold point being reached

Question 11

what concentrations of ions are high intracellular then extracullularly

Answer 11

intracellularly - potassium, protein negatively charged (anions) are higher

extracellularly - sodium and chloride are higher

Question 12

The resting nerve cell membrane has a high relative permeability to

Answer 12

potassium

Question 13

what is the typical resting potential

Answer 13

-65mv, this approximates to the potassium equilibrium potential

Question 14

what is the resting potential of a neurone due to

Answer 14

potassium leaking out of the non gated potassium channels

Question 15

what is the equilibirum potential for sodium

Answer 15

this is the membrane potential at which there is no net flux of sodium across the membrane
+58mv

Question 16

what are the two groups that central nervous system neurotransmitters are classified as

Answer 16

• peptide

- non peptide

Question 17

name some peptide neurotransmitters

Answer 17

• somatostatin
• substance P
• Cholecytokinin
• enkephalins

Question 18

name some non peptide neurotransmitters

Answer 18

• dopamine
• glutamate
• acetylcholine
• GABA
• noradrenaline
• 5-HT

Question 19

what are the types of non peptide neurotransmitters

Answer 19

• Monoamine
• amino acid
• choline esters

Question 20

name some examples of non peptide neurotransmitters

Answer 20

• Monoamine - dopamine, 5HT, noradrenaline
• amino acid- glutamate, GABA
• choline esters - acetylcholine

Question 21

describe how peptide neurotransmitters are synthesised

Answer 21

• starts with synthesis of peptide neurotransmitters
• this happens via transcription of the genes in the cell body nucleus, then translation in the cytoplasm
• this forms the large precursor molecule
• the precursor molecule undergoes translational maturation and cleavage
• then transported to the pre-synaptic terminal via fast axonal transport

Question 22

describe how non peptide neurotransmitters are synthesised

Answer 22

• these are synthesised in the presynaptic terminal from precursor molecules
• the precursor molecules are taken up by active transport process into the terminal

Question 23

are there more peptide or non peptide molecule

Answer 23

non peptide - these are gene products so are more susceptible to evolutionary change

Question 24

where are both peptide and non peptide molecules stored

Answer 24

they are both stored in vesicles following entry by active transport processes

Question 25

describe what happens at the presynaptic terminal causing it to release neurotransmitters

Answer 25

- action potential causes the membrane to depolarise - this depolarisation opens calcium channels - this causes calcium ions to diffuse down there concentration gradient - the increase in intracellular calcium ions causes vesicles to fuse with the membrane and release neurotransmitters - the neurotransmitters are released - they diffuse across the synapse and have an effect on the post synaptic cells

Question 26

what is co-transmission

Answer 26

this is when both non-peptide and peptide are released at the same time

Question 27

what is an autoreceptor

Answer 27

- this is a receptor on the pre-synaptic membrane that is the same shape as the neurotransmitter and can either increase or decrease release of the neurotransmitter

Question 28

how is non peptide neurotransmitter terminated

Answer 28

- by active reuptake into the pre-synaptic terminal

Question 29

how are the ways that neurotransmitters can be stopped

Answer 29

- either by reuptake into the pre synaptic terminal | - or degradation by enzymes in the synapse

Question 30

what happens to neurotransmitters that have been reuptaken into the presynaptic terminal

Answer 30

- either degraded or taken back up for storage in the vesicles

Question 31

what are retrograde transmitters

Answer 31

these are lipophillic molecules such as nitric oxide that use an uncovenentianal mechanism of transport - they are not stored in vesicles but they are syntehsised on demand - act as retrograde messengers - released from postsynaptic terminals and act on presynaptic terminals

Question 32

What is the typical synaptic delay (i.e. time between depolarization of the pre-synaptic terminal and the onset of the post-synaptic respons

Answer 32

0.5ms

Question 33

What effect will a decrease in extracellular [Ca⁺⁺] have on synaptic transmission?

Answer 33

inhibit

Question 34

Approximately how many vesicles are there in each terminal?

Answer 34

10,000

Question 35

How rapidly are peptide transmitters transported from the nucleus to the nerve terminal?

Answer 35

400mm/day

Question 36

What effect will blockade of the pre-synaptic autoreceptors have on synaptic transmission?

Answer 36

unpredictable effect | - depends on the type of neurotransmitter

Question 37

Approximately how many molecules of transmitter are stored in each vesicle?

Answer 37

300

Question 38

What effect will an inhibitor of transmitter inactivation have on synaptic transmission?

Answer 38

potentiate (increase)

Question 39

In the central nervous system, approximately how many vesicles fuse with the pre-synaptic nerve terminal in response to the influx of Ca⁺⁺ associated with each action potential?

Answer 39

between 1-10

Question 40

What effect will blockade of the post-synaptic receptors have on the excitability of the post-synaptic neurone?

Answer 40

unpredictable

Question 41

what are the two receptors that neurotransmitters bind to

Answer 41

- ligand gated receptor ion channel | - G protein ion channels

Question 42

what are ligand gated ion channels

Answer 42

1) Ligand gated ion channels are heterooligomeric proteins traversing the membrane,

Question 43

How many subunits do ligand gated ion channels consist of

Answer 43

often consisting of four or five subunits.

Question 44

how short is the time taken for the neurotransmitter to bind to the ligand gated ion channel and for it to open

Answer 44

e time taken for the transmitter molecules to bind and the ion channel to open is short (<<0.1 msec).

Question 45

what does the duration of channel opening in the ligand gated ion channels depend on

Answer 45

The duration of channel opening depends, in part, on the rate of dissociation of the transmitter molecules and the kinetics of channel gating. - Amino acids induce fast neurotransmitter action in the CNS, but most monoamine and peptide neurotransmitters do not activate ligand-gated ion channels, and thus act more slowly, as neuromodulators.

Question 46

what does a G protein channel consist o f

Answer 46

The receptor consists of a single polypeptide chain that traverses the membrane 7 times.

Question 47

describe how a G protein channel works

Answer 47

- single transmitter molecule binds to the G protein and it becomes activated by the displacement of GDP by GTP - this causes the dissociation of alpha GTP, beta and gamma subunits - Usually α GTP, but often β and gamma as well, stimulates the effector to bring about the response, - Return of the G protein to its resting state occurs by α GTP hydrolysing its bound GTP to GDP, with subsequent reassociation with the β and gamma complex

Question 48

The Duration of effects is in msecs applies to...

Answer 48

ligand gated ion channels

Question 49

Single polypeptide chain is the typical structure of a:

Answer 49

G protein coupled receptor

Question 50

Heterooligomeric protein is the typical structure of

Answer 50

ligand gated ion channel

Question 51

This receptor type requires 2 molecules of transmitter for activation

Answer 51

ligand gated ion channel

Question 52

2nd messengers can mediate the effects of

Answer 52

G protein coupled receptor

Question 53

This type of receptor consists of a peptide chain that traverses the membrane 7 times

Answer 53

G protein coupled receptor

Question 54

what does the amplitude of the EPSP depend on

Answer 54

the amplitude of the EPSP depends on the amount of transmitter released, which depends on the number or pre-synaptic fibres activated which, in turn, will depend on the intensity of the stimulus.

Question 55

what happens if the amplitude of the EPSP reaches the threshold

Answer 55

- an action potential will be generated

Question 56

what can membrane depolarisations also result from

Answer 56

I) Influx of Ca⁺⁺ II) Closing of K⁺ channels III) Efflux of Cl⁻

Question 57

What does the action potential result from

Answer 57

(i) an unequal distribution of ions across the membrane due to the activity of the Na⁺/K⁺ pump and (ii) the presence of a population of non gated K⁺ channels which allows K⁺ to leave the cell down its electrochemical gradient (outward K⁺ current). .

Question 58

describe the characterstics of EPSPs

Answer 58

- localised - non propagated potentials result from the transmitter released from the afferent fibres activating a population of ligand gated ion channels

Question 59

what voltage is the depolarisation sufficient enough to open voltage gated sodium channels and trigger an action potential

Answer 59

At about -55mV (threshold), the depolarization is sufficient to open voltage gated Na⁺ channel, hence triggering an action potential.

Question 60

what usually causes inhibition of an action potential

Answer 60

Inhibitory transmitters usually combine with post-synaptic receptors to open channels permeable to Cl⁻ causing a hyperpolarization (Inhibitory Post-synaptic Potential, IPSP). The opening of channels permeable to Cl⁻ and K⁺ usually mediates synaptic inhibition.

Question 61

what does the amplitude of the IPSP depend on

Answer 61

the amplitude of the IPSP depends on the amount of transmitter released which depends on the number of pre-synaptic fibres activated which, in turn, will depend on the intensity of the stimulus.

Question 62

what happens if you have excitation and inhibitory inputs

Answer 62

have an EPSP of reduced potential