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Neuroscience > Module B-05 > Flashcards

Module B-05 Flashcards

1
Q

What is Synaptic delay?

A

The time (0.5ms) btw arrival of an impulse at the end of an axon and the postsynaptic response

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2
Q

What causes Synaptic delay?

A

Time required for release, diffusion and binding of transmitter, opening of ion channels, movement of ions and changes in enzyme activity.

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3
Q

Number of neurotransmitter molecules in a vesicle

A

Quanta

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4
Q

What effects the probability of exocytosis of transmitter from a vesicle

A

intracelllar Ca2+ concentration

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5
Q

What are mini End plate potentials(mini EPPs)?

A

-spontaneous small transient depolarizations about 1 mV in
size in a muscle at rest
- caused by the motor nerve terminal releasing ACh
spontaneously

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6
Q

What happens when [Mg2+] at NMJ is increased

A

blocks voltage-gated Ca2+ channels and reduced EPPs

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7
Q

Number of quanta released by a single impulse is the _________

A

quantum content

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8
Q

Equation for Mean quantum content

A

Mean Quantum Content = (Mean size of EPP) / (Mean Size of MinEPP)

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9
Q

What is effect of Botulinum Toxin

A
  • Irreversibly Blocks Ach Release
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10
Q

How does Botulinum Toxin block Ach release

A
  • Binds to cholinergic nerve endings
  • enters cell
  • breaks down synptobrevin => prevents docking IRREVERSIBLY
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11
Q

Symptoms of Botulism

A
  • double vision,
  • dysphagia,
  • dry mouth,
  • dysarthria followed by weakness of limbs and trunk.
  • Paralysis of ventilatory muscles => death
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12
Q

Clinical use of Botulinum toxin

A
  • treat dystonias (dysfunctional and sometimes disfiguring contractions of muscle)
  • cosmetically to reduce facial wrinkles
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13
Q

How does the Tetanus toxin act

A
  • enters PNS and moves retrogradely to the CNS
  • enters Glycinergic interneurons (inhibitory
  • suppresses ( irreversibly) vesicle docking by breaking down synaptobrevin
  • prevents inhibition of lower motor neurons
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14
Q

Symptoms of Tetanus

A

powerfully sustained muscular contratcions

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15
Q

What is effect of Tetanus Toxin

A

Blocks Glycine release

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16
Q

Effect of Neomycin and streptomycin

A
  • Block Presynaptic Ca2+ channels => blocks release of Ach at motor nerve terminals
  • At high concentrations, both antibiotics also can block postsynaptic nAChRs
17
Q

How can Effect of Neomycin and streptomycin be reversed

A

By increasing extracellular Ca2+ conc.

18
Q

What is effect of 4-Aminopyridine

A

Prolongs the duration of an impulse

19
Q

How does 4-Aminopyridine prolong impulse

A

it is a K+ channel blocker
enhances ca2+ entry into the motor nerve ending
this increases Ach release ( quantum content)

20
Q

where do EPSPs (excitatory postsynaptic potentials) occur

A

in Dendrites and somata

21
Q

EPSPs spread with ___________

A

decrement

22
Q

where is the highest conc of voltage gated Na+ channels?

A

Axon Hillock (near sensory nerve ending for sensory neurons)

23
Q

Where is region of lowest threshold for excitation?

A

Axon Hillock (near sensory nerve ending for sensory neurons)

24
Q

Temporal summation of PSPs

A

impulses arrive in series add up to produce an EPSP because they arrive before the previous impulse has lapsed

25
Q

Spatial summation of PSPs

A

impulses arrive at different synapses simultaneously and their depolarizing current summates

26
Q

The firing rate of a neuron is dictated by the combined effect of the ______ and _______summation of _____ and _____ (inhibitory post-synaptic potentials)

A

spatial ; temporal ; EPSPs ; IPSPs

27
Q

How are peptides removed from synaptic zones

A
  • Peptide transporters found in blood-brain barrier cells.
  • Diffusion
  • extracellular proteases
28
Q

Slowest removed transmitters

A

ACh, peptides and gases

29
Q

How are Norepinephrine, epinephrine and dopamine degraded

A

1) Monoamine Oxidase (MAO) in the outer membrane
of mitochondria in the nerve endings (also in astrocytes and liver). Some extracellular MAO also exists
2) catechol-omethyltransferase(COMT)which methylates teh catechol ring; located in presynaptic mitochondria, postsynaptic nerve endings, astrocytes and liver

30
Q

How is Serotonin (5-HT)degraded?

A

MAO

Neuroscience (32 decks)

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