205 NS - Biochemistry

Question 1

What does bloody CSF indicate?

Answer 1

Traumatic lumbar puncture

Subarachnoid haemorrhage

Question 2

What does turbid/milky CSF indicate?

Answer 2

Presence of cells
Presence of microbes
Increased protein level
Presence of lipids (milky)

Question 3

Where should lumbar puncture be done?

Answer 3

L3/L4 space or L4/L5 space

• because spinal cord ends at L2, avoid puncturing it

Question 4

What can CSF analysis indicate?

Answer 4

CNS infections
Demyelinating diseases
CNS malignancy
Hemorrhage in CNS
Autoimmune disorders

Question 5

How long should CSF analysis be done within?

Answer 5

Within 1 hour after sample collected

Question 6

What does [glucose] in CSF depend on?

Answer 6

[glucose] in blood
rate of glucose transport into the CSF (efficiency of GLUT)
Metabolic rate of CNS

Question 7

What is the glucose gradient along the neuraxis?

Answer 7

[Glucose] decreases from ventricular to lumbar fluid

Question 8

What’s the function of CSF?

Answer 8

Protection
Buoyancy
Excretion of waste products
Regulation of cranial content volume

Question 9

Excitatory neurotransmitters

Answer 9

Leads to depolarization

Glutamate
Aspartate
Serotonin
ATP

Question 10

Inhibitory neurotransmitter

Answer 10

Leads to hyperpolarization

Glycine
GABA

Question 11

Synthesis of acetylcholine

Answer 11

Choline + acetyl-CoA

Question 12

Metabolism of acetylcholine

Answer 12

After released into synaptic cleft by exocytosis, hydrolyzed by acetylcholinesterase (AChE)

Question 13

2 major constellations of cholinergic neurons

Answer 13

Basal forebrain constellation (sleep & wakefulness)

Dorsolateral pontine tegmental constellation (memory & learning)

Question 14

What receptors mediate sympathetic effects?

Answer 14

Adrenergic

Exception: sweat gland (muscarinic)

Question 15

What receptors mediate parasympathetic effects?

Answer 15

Muscarinic

Question 16

Myasthenia Gravis

Answer 16

Autoimmune disorder

Leads to skeletal muscle weakness due to the development of autoantibody against AChR at NMJ

Question 17

Synthesis of glutamate

Answer 17

Glutamine is synthesized to glutamate by glutamine synthetase (GS)

Question 18

Metabolism of glutamate

Answer 18

Glutamate is broken down to glutamine by glutaminase (GA)

Question 19

Excitotoxicity

Answer 19

Prolonged stimulation of neurons by excitatory a.p. results in neuronal death or injury

Question 20

Synthesis of GABA (γ-aminobutyric acid)

Answer 20

Glutamate is synthesized to GABA by glutamic acid decarboxylase (GAD)

Question 21

Metabolism of GABA (γ-aminobutyric acid)

Answer 21

After release, GABA is taken up into presynaptic terminal & glia
GABA is converted to glutamate by mitochondrial GABA transaminase (GABA-T)

Question 22

What leads to epilepsy?

Answer 22

Lack of GABA in certain parts of brain

Question 23

Which vitamin does glutamic acid decarboxylase (GAD) require?

Answer 23

Vitamin B6

Question 24

Synthesis of catecholamines

Answer 24

Tyrosine → L-DOPA → dopamine
dopamine → norepinephrine
norepinephrine → epinephrine

Question 25

Synthesis of dopamine

Answer 25

1. Tyrosine enters neuron by active transport 2. Tyrosine converted into DOPA by tyrosine hydroxylase 3. DOPA converted to dopamine by DOPA decarboxylase

Question 26

Metabolism of dopamine

Answer 26

Reuptake | Destroyed by COMT (catechol-O-methyltransferase) & MAO (monoamine oxidase)

Question 27

What is used as index of function of dopaminergic neurons?

Answer 27

Homovanillic acid (HVA) - because it's a major metabolite that is produced by action of MAO and COMT on dopamine

Question 28

Where are dopaminergic neurons located in the brain? (3)

Answer 28

Substantia nigra - coordination of movement, degeneration associated w Parkinson's Ventral tegmental area - pleasure & reward; motivation & emotion Hypothalamic arcuate nucleus - regulate secretion of prolactin & maternal behavior

Question 29

What causes schizophrenia?

Answer 29

Too much dopamine

Question 30

What causes Parkinson's disease?

Answer 30

Too little dopamine

Question 31

Schizophrenia vs Parkinson's disease

Answer 31

Schizophrenia - too much dopamine | Parkinson's - too little dopamine

Question 32

Cocaine drug addiction

Answer 32

The ventral tegmental area to limbic structures involve emotional reinforcement & motivation Cocaine binds to dopamine transporter & blocks reuptake of dopamine → increased extracellular level of dopamine

Question 33

Synthesis of norepinephrine

Answer 33

Dopamine β-hydroxylase (DBH) converts dopamine → norepinephrine

Question 34

Synthesis of epinephrine

Answer 34

Phenylethanolamine N-Methyltransferase (PNMT) converts norepinephrine → epinephrine

Question 35

Metabolism of norepinephrine & epinephrine

Answer 35

Same as dopamine: Reuptake Destroyed by COMT (catechol-O-methyltransferase) & MAO (monoamine oxidase)

Question 36

Norepinephrine is involved in?

Answer 36

Sleep & wakefulness, attention, feeding behaviour

Question 37

Mania

Answer 37

Too much norepinephrine

Question 38

Depression

Answer 38

Too little norepinephrine

Question 39

Norepinephrine & epinephrine are neurotransmitters of ______ system.

Answer 39

sympathetic

Question 40

Synthesis of serotonin

Answer 40

1. Tryptophan enters brain by active uptake 2. Hydroxylated by tryptophan hydroxylase → 5-hydroxytryptophan 3. Decarboxylated by aromatic a.a. decarboxylase → serotonin

Question 41

Metabolism of serotonin

Answer 41

After release, serotonin reuptake by serotonin transporter or MAO

Question 42

Serotonergic neurons

Answer 42

Raphe nuclei of medulla, pons, upper brainstem - regulation of pain, mood, sleep

Question 43

How does endorphin act as analgesic?

Answer 43

Endorphins are released by pituitary gland & hypothalamus to block pain perception It binds to opiate receptors located on presynaptic membrane & block release of substance P - neurotransmitter involved in pain responses

Question 44

Subarachnoid haemorrhage

Answer 44

Characterized by bleeding & pooling of blood between the innermost 2 membranes (arachnoid membrane & the pia mater) Occur when bridging blood vessels/dural sinuses rupture

Question 45

Most common cause of subarachnoid haemorrhage

Answer 45

Aneurysm | - when walls of blood vessels are weakened & dilates

Question 46

What does fibrin clot in CSF sample indicate?

Answer 46

Protein level very high

Question 47

How to differentiate bloody CSF sample of traumatic lumbar function of subarachnoid hemorrhage?

Answer 47

After centrifugation, observe supernatant Clear → blood contamination Yellowish → subarachnoid haemorrhage