Module 1: Nerves and Muscle Group Case Study Assignment The Doe family have been through a hard time since Huntah died (remember the octopus?) and John tore his hamstring at the gym. Luckily though, Oscar Doe (the family’s trusty golden retriever) has always had a smile on his face and brought joy to the Doe clan despite their recent misfortune. While John was at home resting his hamstring (and watching repeats of My Kitchen Rules of course!), he noticed that Oscar did not seem himself. Oscar was struggling to walk (his hind limbs fatigued very easily), he had to attempt to swallow his food a number of times in order to get it down (normally he woofs it down in 2 mins flat!), and his eyes were a bit droopy. Oscar still seemed happy, but John knew something was not quite right and decided to investigate using his new iPad Pro. According to Dr. Google, it sounded like Oscar had Myasthenia Gravis (a disorder at the level of the synapse that can affects both dogs and humans). HBS2PTA Human Physiology Theory A 2017 Page 2 of 2 Q1. How is skeletal muscle contraction controlled in a normal healthy person (or dog)? Describe synaptic transmission at the neuromuscular junction. Begin your description with the arrival of an action potential at the pre-synaptic nerve terminal and detail the events that occur up to and including the removal of neurotransmitter from the synaptic cleft [3 marks]. Q2. Starting with Acetylcholine binding on the motor end plate, describe in detail the process by which a neural stimulus leads to muscle contraction (i.e. E-C coupling), remembering to include a description of the mechanisms underlying muscle relaxation. [3 marks]. Q2. Myasthenia gravis is an autoimmune disorder where the thymus gland produces antibodies against the nicotinic acetylcholine receptor. How would this lead to the symptoms Oscar is experiencing? [1mark]. Q3. Myasthenia gravis does not affect smooth muscle. Based on your knowledge of smooth muscle regulation, why might this be the case? Include in your answer a discussion of the differences between smooth and skeletal muscle in terms of how the nervous system controls contraction [3 marks]. Q4. If an autoimmune condition existed in which the proteins that form gap junctions were attacked by Oscar’s own antibodies, how would you expect this to affect his smooth muscles? Would all types of smooth muscle in his body be affected equally? What effect would this hypothetical condition have on his skeletal muscles? [2 marks].