2 - Intro to Neurotransmission

Question 1

what is the input region of a neuron?

Answer 1

dendrites

Question 2

what is the main conduction unit of a neuron?

Answer 2

axon

Question 3

what is the output region of the neuron?

Answer 3

axon terminal

Question 4

what type of synapses are very rare in the adult brain?

Answer 4

electrical synapses

Question 5

what is the gap in a chemical synapse called?

Answer 5

synaptic cleft

Question 6

what initiates neurotransmitter release from the presynaptic terminal?

Answer 6

action potential opening Ca2+ channels

Question 7

what are the 4 main stages of neurotransmitter activity across the synapse?

Answer 7

• synthesis
• storage
• release
• inactivation/reuptake

Question 8

exocytosis

Answer 8

process of presynaptic vesicles binding to presynaptic membranes and releasing neurotransmitters directly into the synapse

Question 9

agonist

Answer 9

substance which stimulates the receptors and mimics the natural ligand

Question 10

antagonist

Answer 10

subtances that block the receptor and prevents the effects of the natural ligand

Question 11

partial agonist

Answer 11

agonist that is unable to induce maximal activation of a receptor population, regardless of the amount of drug applied

Question 12

which class of receptors are most important in neurotransmission due to their rapid conduction?

Answer 12

ionotropic receptors

Question 13

receptors for what hormones are ionotropic receptors?

Answer 13

ACh
Glutamate
GABA

Question 14

what is the mechanism of inotropic receptors?

Answer 14

• neurotransmitter binds to receptors that is part of ligand-gated ion channel proteins
• activation causes conformational change
• allows passage of Na+ (excitatory) or K+/Cl- ions (inhibitory)
• makes membrane potential more +ve or -ve which moves it closer or further from threshhold

Question 15

how are metabotropic receptors coupled to effector mechanism?

Answer 15

via G-proteins

Question 16

what is the mechanism of metabotropic receptors?

Answer 16

• agonist molecule combines the receptor proteins in membrane
• associated G proteins cause conformational change
• ions move in or out of cell

Question 17

list these receptors in order of speed (fastest to slowest):
* kinase-linked receptors
* ionotropic receptors
* intracellular receptors
* metabotropc receptors

Answer 17

• ionotropic -msecs-secs
• metabotropic - secs-mins-hours
• kinase-linked - mins-hours
• intracellular - hours-days

Question 18

where are ionotropic receptors used?

Answer 18

fast neurotransmission (nerve to nerve, somatic nerve to skeletal muscle)

Question 19

where are metabotropic receptors used?

Answer 19

slower neurotransmission processes such as hormone action or growth factor action

Question 20

agonist efficacy in iontropic receptors relates to what?

Answer 20

mean channel open time

Question 21

agonist efficacy in metabotropic receptors relates to what?

Answer 21

ability to activate G-proteins

Question 22

where are kinase-linked receptors used?

Answer 22

regulation of growth
differentiation and responses to metabolic signals

Question 23

where are intracellular receptors used

Answer 23

used by lipid-solube steroid hormones, affecting DNA transcription processed

Question 24

how is dopamine synthesised?

Answer 24

• L-Tyrosine converted to L-Dopa by tyrosine hydroxylase
• L-Dopa converted to dopamine by dopa decarboxylase (DDC)

Question 25

what converts L-tyrosine to L-dopa

Answer 25

tyrosine hydroxylase

Question 26

what converts L-dopa to dopamine?

Answer 26

dopa decarboxylase

Question 27

what is the rate-determining step in dopamine synthesis?

Answer 27

tyrosine hydroxylase, as it becomes saturated by the substrate

Question 28

what postsynaptic receptors can dopamine bind to?

Answer 28

* D1 family (D1 & D5) - excitatory * D2 family (D2/3/4) - inhibitory

Question 28

how is dopamine inactivated/reuptaken?

Answer 28

* metabolised by enzymes - COMT or MAO * reuptake process - dopamine transported (DAT)

Question 29

what are the 4 major dopamine pathways?

Answer 29

1. nigrostriatal pathway 2. mesolimbic pathway 3. mesocortical pathway 3. tuberoinfundibular pathway

Question 30

which dopamine pathway is associated with parkinson's disease?

Answer 30

nigrostriatal

Question 31

which dopamine pathway is associated with +ve symptoms of SZ

Answer 31

nigrostriatal

Question 32

which dopamine pathway is associated with drug abuse?

Answer 32

mesolimbic

Question 33

which dopamine pathway is associated with -ve symptoms of SZ?

Answer 33

mesocortical

Question 34

which dopamine pathway is associated with the side effects of drugs/medication?

Answer 34

tuberoinfundibular

Question 35

what is parkinsons diseas?

Answer 35

* loss of dopamine neurons in the motor circuit * when 60-70% of neurones are lost = symptoms

Question 36

thinking about the synapes involved in parkinsons, what are two potential targets of drug treament?

Answer 36

* give patient L-dopa * give pt agonist that could activate D1 receptors

Question 37

what does the basal ganglia consist of?

Answer 37

5 large subcortical nuclei that participate in the control of movement

Question 38

what are 4 important neurotransmitters in the basal ganglia?

Answer 38

GABA Dopamine glutamte ACh

Question 39

nodes of ranvier?

Answer 39

gaps on unmyelinated neurones between sections of myelin sheath

Question 40

where do pain pathways cross the midline?

Answer 40

spinal cord

Question 41

where do proprioceptive pathways cross the midline?

Answer 41

medulla

Question 42

Label the AP

Answer 42

Question 43

Label the neuronal body

Answer 43

Question 44

Label the dopamine pathways

Answer 44

Question 45

Draw a diagram illustrating the dopamine and motor circuit in the basal ganglia

Answer 45

Question 46

What are the intracellular and extracellular levels of : Na K A Cl

Answer 46

Question 47

Draw a diagram showing what happens when there is increased dopamine in the motor circuit of the basal ganglia

Answer 47