W5- Electrical Signals And Calcium Concentration Flashcards
(22 cards)
What opens VGCC in a nerve terminal?
Depolarisation
What does calcium entry into a nerve terminal cause?
Release of NT
Where are the primary locations of L type calcium channels?
Muscle (skeletal), neurones, lungs
Given an example of a DHP
Nifedipine
Between which two cell types is an NMJ found?
Nerve and skeletal muscle fibre
What is the role of mitochondria and decreasing Ca2+ conc in a nerve terminal?
Mt can uptake Ca2+ so that the calcium conc can be decresased in time for the next a.p
What is the role of synaptotagmin in NT release?
When Ca2+ enters through Ca2+ channels, it binds to synaptotagmin. Vesicles are brought close to the membrane and a SNARE complex forms allowing a fusion pore of which NT can be released through.
How many bidning sites does each nAChR have for ACh?
Where does it bind?
2 per receptor.
ACh binds to the alpha subunits
What does ACh binding tot the nAChR cause?
A conformational change that opens the pore
What are the three ion channels present in a nerve terminal?
VGNC, VGKC, VGCC
Give an example of a competitive blocker and a depolarising blocker.
Competitive-tubocurarine.
Depolarising- succinylcholine
Which enzyme degrades ACh?
ACh esterase
How does tubocurarine work?
It binds to the nAChR so that ACh cannot bind and hence no a.p can be generated
How does succinylcholine work?
It causes a maintained depol at the pos-synaptic membrane so that Na+ channels become inactivated, desk satisfaction occurs and no a.p can be generated
What is a miniature end plate potential a result of?
How many mV?
The result of 1 ACh-containing vesicle releasing its content- 1mV
What is the size in mV of an end plate potential? What is it due to?
10mV, due to a.p induced release of CA2+ from Ca2+
What is mayasthenia gravis caused by?
Autoantibodies which degrade nAChR causing profound muscular weakened which is worse with exercise
What happens to the size of end plate potentials in myasthenia gravis? Why?
They are reduced in amplitude because there are less nAChR to be activated
What are some of the other roles of calcium in the body? List 5
Fertilisation,proliferation, secretion, learning and memory and apoptosis and necrosis
What are the advantages of having a large inward gradient of Ca2+?
Changes in conc can occur rapidly with little move to of Ca2+ and little has to be removed to re-establish resting conditions.
What are the disadvantages of having a large inward gradient of Ca2+?
Energy expensive, Ca2+ overload can lead to loss of regualtion and cell death
What 3 things does the Ca2+ gradient need to be set up and maintained?
Relative I permeability of p.m, expulsion of Ca2+ across p.m (Ca2+ATPase and Na+/Ca2+ exchanger) and Ca2+ buffers
