Case 2 - introduction to neurotransmission

Question 1

what are neurones made up of

Answer 1

• cell body
• axon terminals
• dendrites
• axon

Question 2

what is the cell body made up of

Answer 2

nucleus, stores DNA and rough ER which builds protein and mitochondria

Question 3

what are the dendrite region

Answer 3

the input region; receives input from other neurones

Question 4

what are the axon terminals

Answer 4

the output region; release of neurotransmitter

Question 5

what is the axon region

Answer 5

main conduction unit. carries information in the form of electrical signal known as the action potential

Question 6

what starts and initiates all transmission

Answer 6

the dendrites

Question 7

what can electrical signals not transfer through

Answer 7

the synaptic gap

Question 8

what two things can synaptic transmission be

Answer 8

electrical or chemical

Question 9

what are the pre and post synaptic elements int he chemical synapse separated by

Answer 9

the synaptic cleft

Question 10

what are majority of signals carried in

Answer 10

chemical format

Question 11

what two clusters of cell bodies, dendrites and axons project to different parts of the brain

Answer 11

the substantial nigra and the ventral tegmental

Question 12

when does an action potential occur

Answer 12

when a neurone sends information down an axon

Question 13

how do neurones act as a signalling mechanism

Answer 13

by altering their resting membrane potential

Question 14

what happens at the presynpatic terminal

Answer 14

the action potential opens Ca2+ channels and initiates neurotransmitter release

Question 15

what does the myelin sheath do

Answer 15

speeds up conduction and are an insulator for the axon

Question 16

what happens when you reach threshold

Answer 16

you get the opening of the sodium channels.

Question 17

what gradients does sodium have

Answer 17

electrical and chemical

Question 18

what is the benefit of sodium having two gradients

Answer 18

cause more sodium channels to open and therefore get a huge depolrisation and get a very fast influx of sodium ions

Question 19

what happens once inside the cell is positive

Answer 19

the sodium channel closes and get repolarisation

Question 20

what is repolarisation due to

Answer 20

potassium channels

Question 21

how does potassium move

Answer 21

we know that there is more potassium ibnsde the cell, and at this point It is positive inside the cell swell. therefore potassium leaves the cell and this is repolarisation.

Question 22

what is hyoerpolarisation due to

Answer 22

potassium channels being a little slower to close

Question 23

what is the neurotransmitter released into the synapse by

Answer 23

exocytosis

Question 24

where are neurotransmitters stored

Answer 24

the synaptic vesicle

Question 25

what is exocytosis

Answer 25

where the presynaptic vesicles bind to the presynaptic membrane, then the neurotransmitter is pushed out into the synaptic cleft

Question 26

why is there no excess excitation

Answer 26

enzymes break down the transmitter in the cleft

Question 27

what determines wether it is an excitatory or inhibitory signal

Answer 27

the receptor

Question 28

what is an ionotropic receptor

Answer 28

receptor that is part of ligand gated ion channel protein and activation results in ion conductance changes.

Question 29

what are inotropic receptors opened by

Answer 29

the transmitter to allow the passage of Na+ (excitatory) or K+/Cl- (inhibitory) and are involved in fast transmission - milli seconds

Question 30

what are examples of inotropic receptors

Answer 30

acetylcholine, glutamate and GABA

Question 31

what are metabotropic receptors

Answer 31

receptor protein in membrane that is coupled to effector mechanism via G proteins. in this signalling mechanism, agonist molecule combines with receptor proteins in the membrane

Question 32

what does this result in

Answer 32

conformational change causes activation of a membrane associated enzyme via G protein

Question 33

an example of a metabotropic receptor

Answer 33

dopamine receptor - they are a lot slower

Question 34

receptors summary

Answer 34

Question 35

what is the rate determining step in dopamine synthesis

Answer 35

tyrosine hydroxylase as it is normally saturated by substrate

Question 36

what is dopa decarboxylase

Answer 36

high activity and nonselective

Question 37

diagram showing synthesis of dopamine

Answer 37

Question 38

how is dopamine stored

Answer 38

in the synaptic vesicles in the axonal terminal

Question 39

where is dopamine released

Answer 39

into the synaptic cell upon the arrival of an action potential and influx of Ca2+

Question 40

what 2 postsynaptic receptors does dopamine bind to

Answer 40

D1 family: D1&D5 - excitatory D2 family: D2,3,4 - inhibitory

Question 41

what enzymes metabolise dopamine

Answer 41

COMT and MAO

Question 42

what is the reuptake process

Answer 42

catecholamines have a highly specific active transport mechanism to remove the transmitter from the synapse into presynaptic terminal

Question 43

what is the dopamine transporter

Answer 43

DAT

Question 44

what pathway is drug overuse focused on

Answer 44

the mesolimbic pathway

Question 45

description of the mesolimbic pathway

Answer 45

- ventral tegmental area in the midbrain to limbic regions associated with reward, motivation, affect and memory. - include ventral striatum (Nucleus accumbens), amygdala, hippocampus and medial prefrontal cortex

Question 46

which pathway does Parkinson's affect

Answer 46

the nigrostriatal pathway

Question 47

what would you give to someone with Parkinsons

Answer 47

L-dopa because if you give L tyrosine it doesn't matter how much you have because the tyrosine hydroxyls is the limiting factor as it is saturated. or an agonist at D1 receptors

Question 48

what is the major excitatory neurotransmitter in the CNS

Answer 48

glutamate

Question 49

summary of dopamine pathways

Answer 49

Question 50

order of signalling pathway in brain

Answer 50

1. spinal cord 2. medulla 3. thalamus 4. cortex

Question 51

what are the 5 regions of the basal ganglia

Answer 51

- caudate nucleus - putamen - globus pallidus - sub thalamic nucleus - substantia nigra

Question 52

the direct pathway

Answer 52

Question 53

what is the major inhibitory neurotransmitter

Answer 53

GABA

Question 54

where is acetylcholine released

Answer 54

at the neuromuscular junction