Please enter something

Biochemistry, Chapter 41.2 – neurochemistry

question

myelin of the CNS
answer

oligodendrocytes – wrap around 20 axons and stops cross-talk between neurons
question

myelin of PNS
answer

schwann cells – wrap around a single axon
question

demyelination of CNS
answer

multiple sclerosis
question

demyelination of PNS
answer

Guillain-Barre syndrome
question

Six sources of CSF
answer

blood-brain barrier, blood-CSF barrier, dorsal root ganglia, brain parenchyma of CNS, CSF circulating cells, and meninges
question

blood brain barrier
answer

interstitial fluid source of CSF – 1/3
question

blood CSF barrier
answer

bulk of CSF from here – choroidal fluid b/c it is provided mostly from choroid plexus
question

dorsal root ganglia (blood-dorsal root barrier)
answer

capillaries with higher degree of permeability
question

brain parenchyma of CNS
answer

produce brain-specific proteins (prostoglandin synthase, and trasnthyretin)
question

CSF circulating cells
answer

lymphocytes in CNS that synthesize local antibodies
question

meninges
answer

source of CSF under pathologic conditions – can dramatically increase CSF protein concentration
question

asialotransferrin
answer

transferrin lacking sialic acid – a useful marker protein in the CSF – it is present in high concentrations
question

how is asialotransferrin removed from circulation
answer

by reticuloendothelial cells to be recycled due to lack of sialic acid
question

where can asialotransferrin be found
answer

CSF, aqueous humor of eye, perilymph of semicircular canals of inner ear
question

how can you distinguish CSF rhinorrhea from local nasal secretions
answer

test fluid for asialotransferrin
question

after acute diarrheal illness, patient presents with ascending weakness of limbs followed by respiratory muscle weakness required ventilation. what is a possible diagnosis and what bacteria is the patient infected with>
answer

Guillain-Barre syndrome – infected with Campylobacter jejuni
question

molecular mimicry
answer

similarities between foreign and self peptides that allow foreign molecules to become active – Campylobacter jejuni is an example
question

lady with dizziness, dry mouth, intermittent diarrhea, numbness in both feet, decreased blood pressure, lytic lesion in sternum, Bence Jones protein in urine, increased plasma cells
answer

amyloidosis
question

what is amyloidosis
answer

free light-chain component of myeloma globulin produced by tumor of plasma cells in the bone marrow accumulates in peripheral nerves. the ligh chains conform to B-pleated sheets and the copies intercalate and resist normal proteolysis – so it builds up in the tissue
question

what helps distinguish amyloidosis from neurosarcoidosis
answer

amyloidosis exhibits oligoclonal bands in CSF –> an intrathecal immune response
question

three major cells in the nervous system
answer

astrocytes, oligodendrocytes, and microglia
question

what are oligodendrocytes composed of
answer

mostly fat – serve to insulate axons
question

ependymal cells
answer

minor constituents of nervous system – ciliated cells secreting brain-specific proteins such as prostoglandin synthase
question

what is unique about brain endothelial cells compared to other tissue capillaries
answer

have tight junctions
question

significant features of neurons
answer

length, interconnections, and they do NOT divide postpartum
question

anterograde transport
answer

from nucleus toward synapse
question

retrograde transport
answer

from synapse to nucleus
question

what motile proteins (molecular motors) are used in anterograde and retrograde transport
answer

A- kinesin; R- dynein
question

what protein in the neuron indicates brain death
answer

neuron-specific enolase
question

what protein in the astrocyte indicates a plaque (or scar) as seen in multiple sclerosis
answer

GFAP – glial firbrillary scidic protein
question

what protein in oligodendrocytes indicates de/remyelination
answer

myelin basic protein
question

what protein in microglia indicates a stroke
answer

ferritin
question

what protein in choroid plexi indicate CSF leak (rhinorrhea)
answer

asialotransferrin
question

what is primarily the energy substrate for the brain
answer

glucose
question

under certain conditions, the brain may utilize ___ or ___ from circulation
answer

B-hydroxybutyrate or lactate
question

what % of brain energy is produced and utilized by neurons
answer

70%
question

what CSF cell releases lactate
answer

astrocytes
question

gray matter astrocyte
answer

functional role – filter materials from blood and being fed substances extracted from blood for passage to neurons
question

white matter astrocytes
answer

structural role – if injured, synthesizes GFAP (scar tissue)
question

are astrocytes present in the PNS?
answer

NO
question

what happens at the synapse
answer

neurotransmitter released from axon –> into synaptic cleft –> dendrite of second neuron
question

what does a second messenger usually stimulate
answer

protein phosphorylation
question

what is the job of a G-protein
answer

spans the cell membrane to couple the first messenger (like norepi) to a second messenger (like cAMP)
question

what happens to neurotransmitters ones they have acted on the target cell
answer

become inactivated by hydrolysis
question

what breaks down the second messenger (cAMP)
answer

phosphodiesterase
question

what inhibits phosphodiesterase
answer

caffeine and other methylxanthines (mimic effects of adrenergic neurotransmission)
question

what role does clathrin play in synaptic transmission
answer

coats the vesicles containing neurotransmitters to be released
question

what happens to excess membrane
answer

transported back toward nucleus to be digested in lysosomes
question

what causes a drug to have addictive effects
answer

long-term and short term effects
question

what is the best studied neurotransmitter
answer

acetylcholine
question

where and how is acetylcholine synthesized
answer

in the cytoplasmic compartment of cholinergic nervev terminals from acetyl-CoA and choline by choline acetyltransferase
question

how is acetyl-coA synthesized
answer

pyruvate
question

where is pyruvate synthesized
answer

glycolysis
question

where does choline come from
answer

extracellular compartnemt through a high-affinity choline uptake system
question

nicotinic transmission
answer

exerted by motor neurons located in the brainstem and anterior horns of the medulla oblongata
question

antagonist of muscarinic effect
answer

atropine
question

nicotinic receptor blocker
answer

poisonous snake venom (a-bungarotoxin)
question

what causes impairment of cholinergic neurons in Alzheimer’s disease that leads to loss of cognitive function and eventually dementia
answer

amyloid-B (1-42) in combination with other neurotoxic factors
question

in myasthenia gravis, autoantibodies are formed against __________ receptor
answer

nicotinic
question

what effect does edrophonium have
answer

inhibits acetylcholinesterase – which helps increase ACh
question

where are peripheral cholinergic neurons located and what tissue do they innervate
answer

parasympathetic ganglia; innervate visceral tissue
question

what actions do the peripheral cholinergic neurons take
answer

dilate blood vessels of GI, enhance salivation and peristalsis, constrict airways, control heart function, constrict pupils, and stimulate sexual arousal/genital erection
question

what amino acid are catecholamines synthesized from
answer

L-tyrosine
question

what is a precursor of norepi and epi
answer

dopamine
question

main area that dopamine is located
answer

substantia nigra
question

what does dopamine do
answer

reward, regulation of mood, attention, learning
question

what diseases are disturbances of dopamine associated with
answer

Parkinson’s disease, schizophrenia, restless leg syndrome
question

what is the treatment for dopamine disturbances
answer

L-DOPA b/c is easily crosses the blood-brain barrier
question

when can straight dopamine be delivered to patients
answer

shock and heart failure – to elevate cardiac output and increasae blood pressure and renal filtration
question

what drugs increase dopamine levels at the synaptic cleft
answer

amphetamines, cocaine, nicotine
question

effects of norepinephrine and epinephrine synthesized in the brain
answer

regulatory functions in decision-making
question

norepinephrine and epinephrine effects in the peripheral sympathetic ganglia
answer

increase blood pressure, bronchial and pupil dilation, inhibit peristalsis, increase sweating and renin secretion, and promote ejaculation
question

what mediates the actions of epinephrine and norepinephrine
answer

a-adrenergic and B-adrenergic receptors
question

what blocks a-adrenergic receptors
answer

phentolamine
question

what blocks B-adrenergic receptors
answer

propranolol
question

how is the action of catecholamines terminated
answer

reuptake and degradagtion to aldehydes by mitochondrial monoamine axidases and methylation by catechol-O-methyltransferase –> homovanillic or vanillylmandelic acids which are secreted in the urine
question

excess of what compounds in the urine could indicate adrenal medullar tumor (pheochromocytoma)
answer

homovanillic or vanillylmandelic acids
question

what % of the brain is glutamatergic
answer

50-80%
question

how is L-glutamate synthesized
answer

from a-ketoglutarate by glutamate dehydrogenase and aminotransferases OR from glutamine by phosphate-activated glutaminase
question

what happens when glutamate binds to NMDA
answer

causes depolarization/activation of postsynaptic recipient neurons
question

long-term potentiation
answer

synaptic plasticity – takes place in the hippocampus and different regions of the brain cortex – involved in learning, memory, and other cognitive functions
question

what receptor stimulation plays an important role in long-term potentiation
answer

glutamatergic
question

what is the result of excessive release or impaired uptake of glutamate
answer

accumulation in extracellular space –> prolonged depolarization –> excitotixic injury
question

what causes epilepsy
answer

excessive glutamate release or deficiency of inhibitory GABAergic transmission
question

what converts glutamate to glutamine
answer

glutamine synthetase
question

what is the chief inhibitory neurotransmitter in the brain
answer

GABA
question

what is the ligand for gated chloride channels
answer

GABA
question

what happens when GABA opens chloride channels
answer

Cl- ions flow into neuron –> hyperpolarization and inhibition of transmitter function
question

how is GABA synthesized
answer

by L-glutamate decarboxylase
question

what is the fate of GABA upon termination
answer

reloaded into vesicles or metabolized to succinate (TCA cycle intermediate)
question

what are the most common groups of GABA inhibitors used as sedatives, tranquilizers, or anxiolytic drubs
answer

barbiturates, benzodiazepines, chloral hydrate and valproate
question

what acts as a GABA receptor agonist
answer

ethanol
question

what is happening to Na and K in a resting neuron
answer

Na pumping out; K pumping in
question

what change occurs during an action potential
answer

reversal of Na and K pump -Na in, K out –> repolarizes the resting membrane
question

what causes hyperkalemic periodic paralysis
answer

mutations of Na channels
question

myotonia
answer

inability to relax muscles at will
question

Lambert-Eaton syndrome
answer

disease of the CNS that affects P/Q subtype of calcium channels (molecular mimicry)
question

difference between Lambert-Eaton syndrome and myasthenia gravis
answer

LES – neurotransmitter blocked at presynaptic site; MG – neurotransmitter blocked at postsynaptic site
question

what toxin can be used to relieve contractures in spastic cases of torticollis
answer

botulinum toxin (works on the presynaptic site)
question

steps of synaptic transmission in the mechanism of vision
answer

Cis-retinal converted to trans-retinal –> rhodopsin activated –> cGMP decreases –> Na entry blocked –> rod cell hyperpolarizes –> release of glutamate –> action potential depolarizes bipolar cecll –> depolarization of ganglion neuron to send action potential out of the eye
question

which receptor protein is coupled to the g-protein in vision
answer

rhodopsin
question

what are the two specialized methods of moving cells within the brain
answer

CSF and axonal transport