lecture 13 end of progress test Flashcards
Describe the structure if a nicotinic acetylcholine receptor
One channel/ receptor is made up of 5 subunits that surround the pore in the membrane. Each individual subunit is made up of 4 transmembrane domains connected by ropes with a carboxyl group and one end and a NH3 group on the other. these domains are arranged together similar to how the subunits do it.
Describe the NAChR
Chemically gated channel that opens with the binding of 2 ACh. It is a non selective ion channel that is permeable to both Na+ and K+. It’s opening results in depolarization of the Post synaptic area due to the influx of Na+
Describe Myasthenia gravis
An autoimmune disorder that target the NAChR, reducing their numbers and blocking many of the remaining.
This means you can’t respond to the appropriate amount of ACh released resulting in muscle weakness
How come some AP dont result in muscle contraction for people with MG
As stimuli increases less ACh is in the readily releasable pool this results in lower activation of NAChR but still the same amount of time to activate the receptors.
when a person has MG they have less receptors and plenty of blocked receptors compared to a normal person so when the NT are released they only have the same amount of time as in a normal person to find a receptor and with most gone or blocked they dont have time to make it resulting in not enough NT binding to propagate the AP further as theyve already been reuptaken
How do we treat MG
Through the use of Acetylcholinesterase inhibitors, this enzyme is what causes the uptake and breakdown of acetylcholine. By inhibiting this enzyme we prolong the amount of time that ACh is sitting in the synaptic cleft allowing for them to reach the further unblocked NAChR letting them reach the needed amount activated to propagate the AP into the Muscle fibres
