A 22 year old woman complains of weakness and fatigue that...

Name: a 22 year old woman complains of weakness and fatigue that is worse in the afternoon and during prolonged activity but improved by rest on physical exam dtrs and sensation are normal which o 91847
Uploaded: 2023-02-18T20:11:52-08:00
Duration: 8 min 11 s
Channel: Bryan Valdivia
Description: a 22 year old woman complains of weakness and fatigue that is worse in the afternoon and during prolonged activity but improved by rest on physical exam dtrs and sensation are normal which o 91847

A 22 year old woman complains of weakness and fatigue that is worse in the afternoon and during prolonged activity, but improved by rest. On physical exam, DTRs and sensation are normal. Which of the following is the likely pathogenesis of the disease? O prevention of the release of acetylcholine at the neuromuscular junctions autonomic synapses O axonal demyelinating disease with lower motor neuron palsy O progressive muscular atrophy caused by spinal degeneration O caused by an autoimmune attack on the acetylcholine receptor complex at the post synaptic membrane of the neuromuscular junction resulting in a defective neuromuscular transmission

Transcript

00:01 Not to answer this question, let's talk about this clinical case.

00:05 It is a 25 -year -old preschool teacher, sandy thompson, has not been feeling like herself lately.

00:12 She has been feeling quite tired, and her coworkers have commented on her drooping eyelids.

00:20 Additionally, she's experiencing weakness in her arms and legs, has difficulty talking clearly and even her students, parents, have been concerned that sandy hasn't been looking very happy at work.

00:34 One day at lunch, sandy started to choke on her foot, causing one of her coworkers to perform the hemish maneuver on her.

00:41 While the scare didn't cause any permanent damage, sandy's combined that it is time to go see a doctor.

00:47 It says, how would antibodies against acetal -colding receptors affect the neuromuscular junction? so in this case, if this is your present antigenic neuron, and here you have your vesicles containing acetylcholine.

01:03 What normally happens is that here you have voltage -gated calcium channels.

01:10 And when the membrane of the presynatic neuron depolarizes, it is going to open this calcium -gated or your voltage -gated calcium channels, and it is going to allow calcium to enter to this place here.

01:26 And when calcium enters here, there are going to be some, proteins that are going to eat in exocytosis of these vesicles.

01:37 So these vesicles are going to perform esocytosis, and they are going to release acetylcholine to the synaptic left.

01:46 Okay, so this is the synaptic left here, and here you have the post -synatic neuron that in this case is the skeletal muscle, okay, or the sarcolima.

01:55 So in this case you have your nicotinic receptors, acetyl -colon nicotinic receptors that are particularly ligand -girated ion channels.

02:05 So this is an ion channel that is closed, but when acetylcholine comes and binds here, this channel is going to open and it's going to move ions across the cell membrane.

02:15 And in this case, sodium is going to enter into the cell and this is going to cause depolarization of the sarcolyma and hence muscle contraction.

02:23 So in this case, it says how does acetyl antibodies against the acetylcholine receptors affect the neuromuscular junction? in this case, if you have antibodies here against these receptors, then it is going to prevent acetyl calling to bind to these pockets here, to this pocket here and to this pocket here.

02:48 So it means that this channel is not going to be able to be opened, and this channel is not going to open, and it is going to get or to keep closed.

03:00 And if it keeps closed, then it means that there is not going to be depolarization of the muscle, and hence muscle contraction is not going to occur.

03:10 Now it says, how would antibodies against the ach receptors affect the influx of sodium into the cell? and again, this nicotine receptor is a ligand -gated voltage or a ligand -gated ion channel.

03:27 It means it is an ion channel that depends on a ligand in order to open.

03:31 In this case, the ligand is acetylcholine.

03:34 So if acetyl -calling cannot bind, to this pockets here because of the antibodies against the receptors, then this ion channel is not going to open, and hence sodium is not going to be able to enter into the sarcolima, into the cytoplasm of the skeletal muscle, and hence action potential and muscle contraction is not going to cure, because muscle contraction, in order for it to happen, it requires an action potential.

04:01 So sodium is not going to be able to enter the muscle cell...

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