Holmes 4 Flashcards

(23 cards)

1
Q

Synaptic transmission…two types, what are they? how do they differ?

A

Electrical synapse: current passes directly to the postsynaptic cell, depolarizing it
-no delay and is BIDIRECTIONAL

Chemical synapse: current results in release of transmitters that act on postsynaptic membrane to open ion channels
-has gap delay and is UNIDIRECTIONAL

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2
Q

What structure connects two cells in an electrical synapse? what disease are associated with defects?

A
  • connected by gap junction (pair of hemichannels)
  • 6 subunits called connexins (12 total)

defect: deafness, neuropathies (charcot-marie-tooth-disease), cataracts
- cancer; gap junction is a tumor suppressor gene

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3
Q

T/F electrical transmission is NOT graded and occurs when the currents in the presynaptic cell are below the threshold for an AP

A

False, it IS graded (does not need AP to transmit information) and can even occur when the currents in the presynaptic cell are below the threshold for an AP

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4
Q

Gap junctions are important for cardiac muscles. Why?

A

Signals pass efficiently through gap junctions. Allows cardiomyocytes to contract together (tandem). Problem is with ectopic pacemakers (pacemaking activity that arises elsewhere in the heart; competes with normal pacemaking)

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5
Q

What stimulates neurotransmitter release in chemical synapses?

A

Ca2+ uptake, remember there is delay in chemical synapses

-human neuromuscular muscles don’t have excitatory and inhibitory inputs into muscle (just excitatory)

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6
Q

What is the advantage of electrical synapse? Chemical?

A

Electrical synpase: has speed and reliability

Chemical synapse: can mediate excitation or inhibition, greater plasticity

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7
Q

What are the principal inhibitory neurotransmitters of the human nervous system? Excitatory?

A

GABA and glycine

  • glutamate is the excitatory neurotransmitter
  • all are of the amino acids class

-acetylcholine (Ach) is also very important (depends, excites nicotinic receptors)

NO NEUROTRANSMITTER IS INTRINSICALLY INHIBITORY OR EXCITATORY

-oxytocin is for maternal fxns

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8
Q

What is the diff between neuropeptide neurotransmitters and those of other classes?

A

Neuropeptide neurotransmitters are larger and cost more energy to produce

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9
Q

What is the major CNS excitatory neurotransmitter? Describe it.

A

Glutamate (amino acids)

  • ionotropic receptors: AMPA, NMDA, Kainate
  • acts on GPCRs mGluR receptor (ionotropic)
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10
Q

Describe histamine

A

Excitatory or inhibitory
-Acts on H1-4 receptors and GPCRs (metabotropic)
H1: modulate circadian cycle
H3: inhibits release of other neutrotransmitters (Ach, dopamine, etc.)

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11
Q

Major inhibitory neurotransmitters? Describe

A

GABA: made from glutamate (amino acids)
-acts on GABA receptors
GABAa: Cl- channels (ionotropic)
GABAb: K+ channel activation (causes hyperpolarization) using G protein (GPCR) (metabotropic)

Glycine: acts on glycine receptors (amino acids)
GlyR: Cl- channel (ionotropic)

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12
Q

Acetylcholine? Serotonin?

A

Acetylcholine (excitatory in NMJ) (choline esters)
nicotinic and muscarinic receptors (iono/metabotropic)
-neuromuscular junction exclusive
-acts on parasymp nervous system, sympathetic nervous system and adrenal medulla

Serotonin (biogenic amine)

  • derived from typtophan
  • excitatory and inhibitory
  • acts on serotonin receptors, metabo/ionotropic
  • acts on brain/GI tract
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13
Q

Dopamine? Norepinephrine? Epinephrine?

A

Excitatory and inhibitory; derived from tyrosine..class of catecholamines

dopamine: inhibits release of prolactin (biogenic amine)
- metabotropic/GPCRs

norepinephrine: fight or flight (biogenic amine)
- metabotropic/GPCR
- adrenergic neurons

epinephrine: fight or flight (biogenic amine)
- adrenergic neurons
- metabotropic/GPCRs
- released by adrenal medulla

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14
Q

describe process of making neuropeptide

A

mRNA -> pre-prohormone -> prohormone (in golgi) -> vesicles -> synaptical terminal

neuropeptide into neurohormone or neuromodulator

neurohormone: secreted into bloodstream distant sites

neuromodulator in presynaptic cell: regulate neurotransmitter release

neuromodulator in postsynaptic cell: cosecreted with other neurotransmitters

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15
Q

Describe NO

A

NO - nitric oxide

  • freely diffusing gas
  • does not bind to membrane receptors
  • covalently modifies effectors
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16
Q

Describe purines (ATP) as a neurotransmitter

A
  • ATP is released with noradrenaline (NA) and neuropeptide Y (NPY) from perivascular sympathetic nerves
  • evoke smooth muscle contraction
  • important for immune system
17
Q

Describe parkinson’s disease and causes.

A

causes are genetic and environmental
-derivatives of L-Dopa (dopamine derivative) are used to tread PD to compensate for loss of dopaminergic neurons in the SUBSTANTIA NIGRA

18
Q

What is reserpine toxicity?

A
  • Reserpine was drug to treat hypertension

- caused depression though because of irreversible blocking of vesicular monoamine transporter (VMAT)

19
Q

Describe calcium release for synapses.

A

1) open voltage-gated Cav channel
2) Ca2+ rises near presynaptic membrane
3) triggers fusion of presynaptic vesicles loaded with transmitters

fxn similarly to Nav channels

  • slower inactivation than Nav
  • located near vesicle docking zones
  • during AP, Ca2+ concentration can rise more than 1000x
20
Q

What disorder is associated with malfunctioning presynaptic release at NMJ?

A

Lambert-Eaton myasthenic syndrome

  • LEMS is an autoimmune disorder
  • antibodies against voltage-gated calcium channels in presynaptic terminal at NMJ
  • treatment of malignancy can treat LEMS
21
Q

What are some proteins involved in synaptic vesicle fusion?

A

SNAP, SNARE (zipper model), VAMP, Synaptotagmin (calcium sensor)

22
Q

What is botox?

A

Botox uses botulinum toxin to cleave SNARE proteins (zipper)

23
Q

What happens to the empty vesicles at presynaptic cleft?

A

Classical pathway: excess membrane retrieved by clathrin-coated pits (not found at active zone)

Kiss and run pathway: vesicle does not completely integrate with PM, neurotransmitter released through fusion pore

Bulk endocytosis pathway: excess membrane reenter the terminal by budding from uncoated pits (formed at active zone)