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].