Human Physiology Theory: 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
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].
Starting with Acetylcholine binding on the motor end plate, describe in detail
by which a neural stimulus leads to muscle contraction (i.e. E-C coupling),
include a description of the mechanisms underlying muscle relaxation. [3
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].
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].
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].