Neurochemistry

Question 1

What is the role of astrocytes?

Answer 1

Modify synapses
Control potassium ions
Control BBB
Neurotransmitter reuptake

Question 2

What is the role of oligodendrocytes?

Answer 2

They form the myelin sheath of multiple neurons

Question 3

What is the role of microglia?

Answer 3

Resident immune cells of the CNS
Engage in phagocytosis

Question 4

What is the role of ependymal cells?

Answer 4

Ependymal cells line the ventricles
Produce monitor and circulate CSF

Question 5

What is the role of vascular epithelial cells?

Answer 5

Line blood vessels and form part of the BBB

Question 6

Where are axons located?

Answer 6

Distal to the cell body

Question 7

Where are dendrites thpically located?

Answer 7

At the cell body

Question 8

What are the three main divisions of neurons (polarity)?

Answer 8

Bipolar (olfactory, retinal)
Multipolar (purkinje, pyramidal)
Unipolar (dorsal root ganglion)

Question 9

What kind of circuits exist in the CNS?

Answer 9

Divergence
Same pathway
Multiple pathways

Convergence
Multiple sources
Single source (multiple synapses between same two neurons)

Reverberating circuit (feedback system)

Parallel after discharge circuit

Question 10

Where are vesicles stored?

Answer 10

Presynaptic terminal

Question 11

Where are neurotransmitters made?

Answer 11

Cell body

Question 12

What are the two forms of axonal transport?

Answer 12

Slow (1-5mm/day)
Fast (200-400mm/day) - neurotransmitters, growth factors, toxins, viruses

Question 13

What are the three types of synapse?

Answer 13

Axodendritic - axon to dendrite
Axosomatic - axon to cell body
Axoaxonic- axon to axon

Question 14

What are the two types of receptor?

Answer 14

Ionotropic - ligand-gated ion channels

Metabotropic - GPCRs

Question 15

How do ligand gated ion channels function?

Answer 15

The binding of a ligand (eg neurotransmitter) changes the shape of the receptor, opening a channel for ions to flow through

Fast effects

Examples: NMDA, AMPA

Question 16

How do metabotropic receptors function?

Answer 16

Agonist activates receptor
G protein is activated and produces effector
Effector stimulates 2nd messenger synthesis
2nd messenger activates intercellular process

Indirect, slower effect

Question 17

What is the canonical 2nd messenger?

Answer 17

Cyclic AMP

Question 18

On what level does a neurotransmitter work?

Answer 18

Single neuron/receptor level

Excitatory - depolarised the membrane and increases the probability of an action potential on that neuron

Inhibitory - hyperpolarises the membrane and decreases the probability of an action potential on that neuron

Question 19

What would be the effect of serotonin acting on Gi coupled receptor?

Answer 19

Inhibitory

Question 20

How might excitatory dopamine have an inhibitory effect in a circuit?

Answer 20

Activation of the D1 receptor on a GABA-ergic neuron would increase GABA release at the synapse

GABA would inhibit a downstream glutamatergic neuron

Question 21

What are the different forms of control of neurotransmitter release?

Answer 21

Activity dependent - neuronal firing rate alters NT concentration at cell body, auto receptors modulate firing rate in turn

Concentration dependent - presynaptic auto receptors can modulate excitability and NT release

Other transmitters - NTs from other terminals activate pre synaptic heteroreceptors (serotonin receptor stimulation at noradrenergic terminals can trigger noradrenaline release)

Question 22

How might neurotransmitter activity be terminated?

Answer 22

Dissociation from receptor

Receptor internalisation

Synaptic neurotransmitter concentration drops
-diffusion
-reuptake
-catabolism (AChE, MAO)

Question 23

What type of neurotransmitters are there?

Answer 23

Amino acids - glutamate, GABA, glycine

Gasotransmitters - NO, CO

Monoamines - serotonin, dopamine, noradrenaline, histamine

Trace amines

Peptides - opioids

Purines - ATP, adenosine

Cannabinoids - anandamine, CBD, THC

Acetylcholine

Question 24

What ion channels are GABA associated with?

Answer 24

Chloride
Potassium

Question 25

What ion channels are glutamate associated with?

Answer 25

Cations - sodium, potassium, calcium

Question 26

How do benzodiazepines affect GABA activity?

Answer 26

Modulate GABA receptors to increase the efficacy of GABA

Question 27

How is glutamate implicated in neurodegeneration?

Answer 27

Excitotoxicity from increased glutamate release causing cell damage and death

Question 28

What is the function of nicotinic acetylcholine receptors?

Answer 28

Excitatory (ionotropic)

Question 29

Cell bodies in which areas are dopaminergic?

Answer 29

Substantial nigra Ventral tegmental area

Question 30

What receptors does dopamine associate with?

Answer 30

GPCRs

Question 31

Which dopamine receptor is excitatory?

Answer 31

D1 only The most widespread

Question 32

How do amphetamines, cocaine, and methylphenidate (ADHD medication) act?

Answer 32

Inhibit dopamine transporters Increase synaptic dopamine

Question 33

What enzyme breaks down extracellular dopamine? (Clue: which inhibitor is used to make L-DOPA more effective?)

Answer 33

COMT

Question 34

Why is L-DOPA used as treatment instead of dopamine?

Answer 34

Dopamine can’t cross BBB (Also has effects on heart rate)

Question 35

Where are the noradrenergic neurons located?

Answer 35

Locus coeruleus

Question 36

In what ways are noradrenaline and dopamine related?

Answer 36

Structurally similar NAT transporters are inhibited by same antagonists as DAT transporters Both broken down intracellularly by MAO Both broken down extracellularly by COMT

Question 37

Where are serotonergic neurons located?

Answer 37

Raphe nuclei

Question 38

What drugs block Serotonin reuptake transporters (SERTs)?

Answer 38

MDMA Amphetamine Cocaine TCAs SSRIs

Question 39

Where are histaminergic neurons located?

Answer 39

Tuberomammillary nuclei in the posterior hypothalamus

Question 40

What does histamine regulate? (Think about where the neurons are located)

Answer 40

Sleep, appetite, body temperature

Question 41

What neuropsychiatric disorder is histamine implicated in

Answer 41

Schizophrenia

Question 42

How does caffeine act on dopamine?

Answer 42

Caffeine blocks adenosine receptors Adenosine unable to block D2 receptors Increased effect of dopamine

Question 43

What receptors do heroin and other opiates work on?

Answer 43

Mu opioid receptors

Question 44

What is the endogenous counterpart of THC?

Answer 44

Anandamide

Question 45

What is the endogenous counterpart of CBD?

Answer 45

2AG

Question 46

What do cannabinoids regulate?

Answer 46

Motivation Pleasure Feeding behaviour

Question 47

Where do new experiences effect change in the CNS?

Answer 47

At the synapses

Question 48

What is the Hebbian theory maxim?

Answer 48

Neurons that fire together wire together

Question 49

What is the role of NMDA in synaptic plasticity (long term potentiation?)

Answer 49

At resting membrane potential ion flow at NMDA is blocked by Mg2+ Depolarisation of the post synaptic membrane displaces Mg2+ Ca2+ influx activates 2nd massagers Patterns of this influx influence synaptic plasticity

Question 50

How are SPECT and PET imaging used in neurochemistry?

Answer 50

Radioactive tagging (Carbon-11) of a ligand that will bind to a particular receptor Effectively radiotagging each receptor Allows for quantification if receptors