Neurobiology Flashcards
What do astrocytes do?
Balance K+ to help neurons remain responsive, stimulate endothelial cells to form tight junctions. Supportive cells that stain c GFAP
What are Bergman Cells?
Astrocytes that support Purkinje cells of cerebellum
What are Muller cells of the retina?
Specialized astrocytes of retina
Where are unipolar neurons found
Autonomic nervous system
What are bipolar neurons associated with?
The senses
Where are pseudounipolar neurons found?
Sensory ganglia of cranial and spinal nerves (DRG)
What are the most common types of neurons?
Multipolar
What type of cell makes up the choroid plexus BBB?
Epithelial
Kinesin
Binds organelle resulting in stepwise transport from axon
Vinblastine and Colchicine
Disrupt fast anterograde axonal transport
What makes up slow anterograde axonal transport?
Component A (Dynamin-GTP) and Component B(Actin/myosin)
Retrograde axonal transport
(Dynein+ATP) facilitates passage of endosome to soma (delivers GF and rabies/tetanus toxin)
What are connexins?
Transmembrane channels for electrical synapses
Where are small molecule neurotransmitters synthesized?
Cytosol of the neuron. Includes: Ach, ATP, Dop, NE, Epi, 5HT, HIstamine, Glycine, Glu, GABA
What enzyme makes acetylcholine?
Cholin + Acetyl COA, Enzyme = choline acetyltransferase
What neurotransmitter is found in the Nucleus Basalis of Meynert?
Ach
What three neurotransmitters are synthesized from L-tyrosine?
Dopamine, NE, Epi
What is the rate limiting step of Dopamine synthesis
L-tyrosine –> L-dopa (enzyme tyrosine hydroxylase)
Where is dopamine synthesized?
Substantia nigra and arcuate nucleus of hypothalamus
Reserpine
Prevents uptake of DA into synaptic vesicle
What does Dopamine Beta-hydroxylase do?
DA –> NE (NE is only neurotransmitter syn in vesicle)
Norepinephrine exerts negative feedback on _____?
Tyrosine hydroxylase
Where is NE found?
Postganglionic sympathetic neurons and locus ceruleus (Pons-lateral floor of 4th ventricle)
Cocaine
Inhibits NE reuptake
COMT and MAO
metabolize NE
Tropolone and Selegiline
inhibit COMT and MAO-B
Epinephrine is synthesized from ____ by _____ in the ________?
Norepinephrine, phenylethanolamine N-methyl transferase, adrenal medulla
How is serotonin made?
Tryptophan –> 5HT (by trypthophan hydroxylase) –> Serotonin (5HT decarboxylase)
Where are serotonergic neurons found?
Raphe nuclei of brainstem reticular formation
Reserpine and tetrabenazine
Inhibit the transport protein for amine neurotransmitters
Amphetamine
abolish proton gradient of amine vesicles and leads to increased synaptic Dopamine/NE. Will eventually deplete neurotransmitter
What are 2 peptide neurotransmitters and where are they made?
Substance P and enkephaline. Made in the E.R..
POMC –>
B-endorphine, melanocyte stimulating hormone, ACTH, corticotropin like
Release of neurotransmitters involves?
Voltage gated Ca Channels
vesicle SNARE
protein in vesicle wall that binds target-SNARE (syntaxin) in the axon terminal membrane. Results in vesicle fusion and release
Tetanus toxin
Cleaves synaptobrevin and inhibits glycine release
Botulinum toxin
Cleaves t-SNARE and v-SNARE
Synaptotagmin
facilitates fusion of vesicle by inserting into presynaptic membrane (also facilitates endosome formation)
Ionic receptors
Directly gate ion channels
Metabotrophic receptors
influence ion channels via second messengers
What are the two types of metabotrophic receptors?
G-protein and Tyrosine kinase
Cholera toxin
selectively activates Gs (stimulatory G protein). Stimulates bowel movements
Pertussis toxin
inactivates Gi (inhibitory G protein) (can’t stop coughing)
Lithium
inhibits phosphatases which degrade IP3
Phospholipase C
Generates DAG and IP3 –> opens Ca channels and activates PKC
What are the two types of Acetylcholine channels/receptors?
NIcotinic and Muscarinic
alpha- bungarotoxin
Snake venom that binds alpha subunit of nicotinic receptor
What are ganglionic, depolarizing, and non-depolarizing nicotinic inhibitors?
Hexamethonium, succinylcholine, D-tubocurarine
Where are nicotinic receptors found?
NMJ and preganglionic ANS
Where are muscarinic receptors found?
Cerebellum, striatum, cortx, Renshaw cell of SC (glycine)
What inhibits muscarinic receptors?
Atropine and scopolamine
What stimulates muscarinic receptors?
Bethanechol (Bladder), Carbachol (GI), Pilocarpine (eye)
GABA-A opens what type of channel?
Chloride channels –> inhibitory postsynaptic potential
Alcholol, barb, and benzos increase ___?
Chloride channel opening
GABA-B
Increases K+ conductance –> IPSP
Baclofen
GABA-B agonist. Clinically thought to balance excitatory and inhibitor input to reduce muscle hyperactivity
Picrotoxin
inhibits GABA-A. Binds B subunit
Glutamate receptor
ionotropic receptors that induce EPSP. Include NMDA and Kainate
NMDA receptor
permeable to Ca, Na, K. Normally blocked by Mg –> removed by depol and Glycine required to open. Important in long-term potentiation at synapse
PCP
inhibits NMDA receptor
Strychnine
blocks glycine release (Renshaw cell neurotransmitter)
Dopamine receptors
5 groups, all metabotropic. D1- hyperpolarization, D2- depolarization (where antipsychotics selectively inhibit)
LSD
agonist of 5HT-1c Receptor
Ondansetron
agonist of 5-HT3 receptor
Name two sites of neurogenesis:
Subependymal zone, Hippocampus (dentate gyrus c projections to CA3)
Apoptosis leads to –>
chromatin condensation, outer membrane blebbing, cellular fragmentation, phagocytosis
What is the caspase pathway for apoptosis
1) Death induced by Fas signaling complex –> activation of Caspase 8
2) DNA damage- Caspase 9: Cellular stress -> cytochrome c -> apoptosome ->Caspase 8&9 -> Caspase 3&7 -> outer membrane blebbing, DNA condensation, fragmentation, phagocytosis
Bcl-2
antiapoptotic: prevents cytochrome c release and thus Caspase 9
p53
tumor suppressor gene: suppress cell cycle progress after DNA damage –> apoptosis
What is the resting neuron membrane potential?
-70mV: secondary to high intracellular K+ (-75mV)
Tetrodotoxin
blocks voltage gated Na Channels
Tetraethylammonium
blocks voltage gated K channels
What increases axonal conduction velocity
Large diameter (thick myelin sheath) and transmembrane resistance. Long internode length between nodes of Ranvier. Low internal resistance and membrane capacitance (dependent on number of membrane channels).
What is the average total brain water content?
78%
What maintains flexor tone balance by inhibiting extensor activity?
Rubrospinal tract
Botox
Interfers with Acetylcholine release
Curare
blocks acetylcholine receptor
What is the genetic defect of Down syndrome and what are the associated conditions?
Triplication of 21q22. Early onset Alz, leukemia, DM, brachycephaly, microcephaly, atlantoaxial instability, os odontoideum
What are three endogenous antioxidants?
1) SOD
2) Glutathione peroxidase
3) Catalases