Biochemistry, Chapter 41.2 – neurochemistry – Flashcards
Unlock all answers in this set
Unlock answersquestion
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
