Part B: Nervous system function (17 marks) Jenny had surgery to set her broken bone; this was done under general anaesthesia.
The unlabelled
graph of the
action potential
phases has been
provided to
assist with your
answers 1. When nerve cells are at rest, there is a resting membrane potential (RMP; phase #1 on
graph) for the neuron cell membrane. Describe how the RMP is generated. (3 marks)
2. Jenny is conscious and alert when certain neurons in her brain are active. Her neurons
depolarise, produce action potentials, repolarise and hyperpolarise. Define
depolarization and hyperpolarization and explain their relationship to threshold. (3
marks). 3. Jenny’s nerve cell membranes have both leak (passive) potassium channels and
voltage-gated potassium channels. Explain how these channels differ, in terms of
where in the cell they are located and in how they work. (3 marks) 4. Anaesthesia to be used for Jenny’s procedure will affect her neurons for
consciousness and sensation of pain. The anaesthetic acts by opening more potassium
leak (passive) channels. How does this make Jenny’s neurons less likely to produce
the action potentials that would normally keep her awake and experience pain? (3
marks)
5. Skeletal muscle has similar types of potassium leak (passive) channels that react with
the general anaesthesia. What might be the effect on Jenny’s skeletal muscle
contraction during surgery? Explain. (2 marks) 6. Prior to surgery, Jenny’s pre-op blood testing revealed hyperkalaemia (indicated high
levels of extracellular potassium. What effect would elevated extracellular potassium
have on muscle and nerves cells? (3 marks) Part C: General questions on Nervous System Function (6.5 marks)
1. In terms of nerve communication,
a. Why might a patient experience sensations of tingling and numbness in their
lips/tongue/face/neck? Suggest possible steps in nerve transmission that may be affected
(3 marks) b. Suggest likely affected peripheral nerves that may cause paralysis in the face and
mouth; Justify your choice. (3.5 marks) Part D: Skeletal muscle function (24.5 marks) You will need to research this topic.
Search terms and topics: Malignant Hyperthermia (MH); Ryanodine (RyR) receptors;
Halothane binding to variant RyR1 receptor.
Brian Wilson is an 18-year-old male student who was healthy until two days ago when he
experienced severe abdominal pain, fever, and vomiting. A visit to his GP revealed that he
had acute appendicitis. Brian is in excellent health but during the surgery, his body
temperature began to rise quite quickly. Medical staff managed this emergency and later
diagnosed a genetic condition called Malignant Hyperthermia (MH) that causes a rapid rise in
core body temperature, severe muscle contractions and respiratory distress under general
anaesthesia (with Halothane). 1. How do Brian’s skeletal muscles contribute to his body temperature? (2 marks) 2. In a normal muscle cell, describe the sequence of events and cell locations that lead to
calcium release for contraction. (4 marks) 3. During Brian’s sedation, Halothane anaesthetic caused an adverse effect by binding with
Brian’s variant RyR1 ryanodine receptor located in his skeletal muscle cells. At what
location in Q2 did this occur? Explain what happened at the molecular level that caused
the severe muscle contractions. (4 marks) 4. This MH condition causes a hypermetabolic state in skeletal muscle, which is triggered
by high demands for ATP during uncontrolled muscle contractions. a. Explain what “hypermetabolic” means. (1 mark) b. Discuss the impact of the hypermetabolic state on chemical demands and adjustments to
metabolism in Brian’s skeletal muscle cells. (10 marks) c. How does ATP contribute to maintaining calcium concentration gradients in muscles?
(1.5 marks) 5. Suggest a likely mode of action for a drug to reduce excessive skeletal muscle
contraction during in any future procedures where Brian needs anaesthesia. (1 mark) 6. What effect do you expect this drug would this have on Brian’s body temperature? Why?
(1 mark)

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