Vesicular release

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  • Created by: Jess
  • Created on: 14-05-14 17:45
Outline the main steps in the production and recycling of synaptic vesicles.
Delivery of vesicle components to pm, endocytosis of components to form new vesicles, delivery to endosome, building of vesicles, loading of neurotransmitter, secretion by exocytosis.
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Why store transmitters in vesicles?
Provides a high conc to allow binding, protection from degradation, provides a storage system, allows for regulation.
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What is the ionic requirement for vesicle release?
Calcium is the trigger for fast evoked release and is an absolute requirement for release, sodium and potassium are not.
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What is the evidence that calcium is the trigger for release?
Pharmacological block of channels - no release, increase in calcium - release is facilitated, injection of calcium to axon terminal evokes release, calcium indicator dyes show an increase.
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What is calcium release proportional to?
Related to the power of calcium concentration (roughly 3 to 4). Non linear relationship.
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Name a calcium channel blocker.
Cadmium.
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What are the types of voltage gated calcium channel?
N (neither long lasting or trasient), L (long lasting, ms), P/Q, R.
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Why is the spacing of calcium channels and vesicles important?
When they are closely associated a single channel can elicit release but when they are separated a single channel is unlikely to elicit release.
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What is the evidence that P/Q-type channels are wholly responsible for control of ACh release?
A specific blocker of P/Q type channels abolishes release and EPSPs.
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What does cooperative mean?
The action of more than 2 inhibitors is greater than the sum of the individuals.
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Vesicular release is quantal, what implications does this have for the size of the response?
The size of the response is proportional to the number of quanta.
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What is a MEPP/mini?
Miniature end plate potential. Small depolarisation at a synapse due to the spontaneous release of one quantum (in the absence of presynaptic APs).
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How would quantal release be shown on a distribution histogram?
Multiple peaks.
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How does 4-AP (K channel blocker) increase efficiency of quantal release?
Blocks the K current involved in AP repolarisation, increases duration of the AP, more calcium released.
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What is the evidence that release is quantal at a specific synapse?
Electrical stimulation causes depolarisations with an amplitude of a multiple of the "mini", addition of 4-AP causes the similar phenomenon.
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What properties does a binomial experiment have?
Consists of repeated trials (n), only two possible outcomes, the probability of success (p) is the same on every trial, the trials are independent.
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What factors influence p?
Size/shape of depolarisation, number/functional state of Ca channels, distance of vesicles from channels, baseline of int Ca, number of primed vesicles, P state of presynaptic proteins.
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How do Clostridial toxins block quantal release?
Toxin is a zinc protease which cleaves the fusion proteins by which vesicles release ACh into the neuromuscular junction.
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What can botulinum toxin type A be used for?
Botox. Blocks transmission to reduce contractions of the facial muscles that cause wrinkles.
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Card 2

Front

Why store transmitters in vesicles?

Back

Provides a high conc to allow binding, protection from degradation, provides a storage system, allows for regulation.

Card 3

Front

What is the ionic requirement for vesicle release?

Back

Preview of the front of card 3

Card 4

Front

What is the evidence that calcium is the trigger for release?

Back

Preview of the front of card 4

Card 5

Front

What is calcium release proportional to?

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