5. Neuromuscular Junction Flashcards
Neuromuscular junction is when an A alpha comes down and meets a muscle cell.
Neuromuscular junction is when an A alpha comes down and meets a muscle cell.
What is the neurotransmitter used for Neuromuscular junctions?
Acetylcholine
Why can’ the synaptic cleft be a space full of air and what is in it?
the synaptic cleft can’t be a space full of air because neurotransmitters can’t travel through air. They need to travel through liquid so basal lamina is within the synaptic cleft. It is a sponge with fluid.
What is the name given to receptors that respond to ACH? to Nicotine?
Cholinergic and Nicotinic
What must be done in order to activate the Nicotinic-m-Acetylcholine receptor (NmAchR)?
the ligand-dependent ion channel has to take 2 Ach to activate.
General NMJ function is to get an action potential from an A alpha motor neuron to trigger an action potential in muscle cells so that the muscle cells can be triggered to contract. List the steps of this process.
1) A alpha motor neuron fires AP and goes to presynaptic terminal.
2) Activate P/Q Ca++ channels. Ca++ has a higher quantity outside so there is an influx of Calcium into the synaptic terminal.
3) Calcium triggers vesicle exocytosis. Causes vesicles to fuse with membrane and release Ach.
4) Ach diffuses across the cleft, 2 Ach neurotransmitters bind to the NmAchR which then activates. Sodium comes into the postsynaptic terminal and causes a depolarization. This depolarization may be named EndPlate Potential (EPP). This depolarization may cause an action potential.
What are the ways in which you can terminate Ach release?
1) stop exocytosis, otherwise Ach keeps getting dumped and EPP goes up. In order to stop exocytosis, the calcium diffuses away from vesicles.
2) there are also pumps that pump calcium out of the presynaptic terminal.
3) Ach dissociates from the NmAchRs. ach gets off receptors and receptor deactivates. Stops letting sodium in.
4) Removal of Ach out of cleft. Some diffuse away while others go through an enzymatic breakdown using the enzyme AchE or acetylcholineesterase. This yields choline and acetate as the product.
The choline that is in the cleft is recycled to create Ach. Neurons don’t make their own choline, so they take the choline from the cleft and put it back into the presynaptic terminal. This process is called choline uptake. Choline + AcCoa -> Ach + Coa
Neurons don’t make their own choline, so they take the choline from the cleft and put it back into the presynaptic terminal. This process is called choline uptake. Choline + AcCoa -> Ach + Coa
