2000 - Question 1. Myasthenia gravis is an autoimmune disease in which antibodies are generated against the nicotinic receptors on skeletal muscles. These antibodies bind to the receptors and effectively destroy most of them.
As a result, the patients have substantially reduced muscle strength.
(a) Part of the treatment for the condition is to give an inhibitor of acetylcholinesterase, such as neostigmine, systemically. Briefly explain how such a drug would help to restore muscle strength.
(5 minutes)
(b) Usually, when the anti-cholinesterase is given, the patients are also given atropine, or another drug that is an antagonist at muscarinic receptors. Why is this necessary?
(5 minutes)

 

2001-Question 3.
Around 100 years ago, the celebrated English physiologist, John Newport Langley, carried out a series of experiments that were instrumental in understanding the functional organisation of autonomic motor pathways. In these experiments, he used nicotine to identify the location of synapses between preganglionic and postganglionic sympathetic or parasympathetic neurons.
Langley knew that nicotine is an agonist at what we now know to be nicotinic acetylcholine receptors.
(a) Sympathetic innervation speeds up the heart and parasympathetic innervation slows the heart. How would you expect heart rate to be affected if you applied nicotine directly to the heart? Explain your answer.
[5 minutes]
(b) Some of the autonomic pathways identified by Langley are activated together with somatic motor pathways when we develop a fever in response to systemic infection. The responses include shivering, sweating and cutaneous vasoconstriction. Discuss the functions of acetylcholine in the peripheral neural pathways mediating each of these responses.
[10 minutes]

 

2002 - Megan Worrall is a 24-year old former Ansett flight attendant, who now works part-time with a car rental company. When her new boss complains that she looks ‘half-asleep’ all the time, she decides to consult her G. P. Megan tells the G.P: “I used to be full of energy. Last year, my problem was fitting time for golf into my flight schedule. Now I have more time and I have been out on the golf course a few times a week. But lately I feel tired. When I play gol I have to rest after each hole. I get tired walking up the fairway. I have had some double vision too. ”
Question 6
List key infonnation about Megan. Outline twp hypotheses that you consider most likely to account for her problems. For each hypothesis, briefly outline how the hypothesis relates to the key infomation.
(15 minutes)
Question 7
List three pieces of information you would seek from history or physical examination to help clarifir the nature of Megan’s problem. For each, indicate how possible answers would help confirm, eliminate or distinguish between your hypotheses.
(10 minutes)
Megan says she began noticing episodes of muscle weakness 3 or 4 months ago. She generally starts an activity feeling normal but then tires rapidly and is unable to continue any form of exertion. Periodic problems with double vision (diplopia) have been increasing over the last 2-3 months. She has noted occasional difficulties swallowing.
Megan says she was initially angry about the loss of her job with Ansett. However, she is reasonably
happy with her new job and “OK financially”. “Having some extra free time has been good, but
lately, I just don’t have the stamina to make the most of it. ”
Physical examination shows a relatively fit young woman. Her pulse, B.P. and respiration rate are
normal
She has noticeable ptosis (drooping of the eyelids) which becomes worse with sustained upgaze.
Diplopia becomes apparent on looking to the lefl‘ or right for more than 5 seconds. Her sensory responses and tendon reflexes are normaL She is unable to complete more than 5 squats.
Question 8
How does the new information influence your hypotheses‘? Explain briefly. Summarise what is now your preferred hypothesis to explain Megan’s condition.
(15 minutes)
Question 9
What further investigation or test would you conduct to help test your preferred hypothesis? Briefly explain the rationale.
(5 minutes)Megan is referred to a neurologist, who after a physical examination, tests the effects of an I. V. injection of edrophonium on Megan ’s ability to sustain exercise. Edrophonium is a short acting anticholinesterase agent. With a I0 mg dose of edrophonium, there is temporary resolution of her ptosis and diplopia (lasting 2 minutes).
A subsequent blood test revealed high levels of antibody to the nicotinic acetylcholine receptor. This antibody is not present in normal plasma.
Treatment with pyridostigmine, a long-acting reversible inhibitor of acetylcholinesterase, resulted in a marked improvement in Megan ’s muscle weakness.
Question 10
How do the results of the tests and effect of the pyridostigmine treatment influence your preferredhypothesis. Explain. Include in this answer
(i) a discussion of the role of the nicotinic acetylcholine receptor in muscle contraction,
(ii) a suggestion for how a reversible inhibitor of acetylcholinesterase might lead to an improvement in Megan’s condition.
(15 minutes)

 

2003 - 3. In essential hypertension the arterial blood pressure is raised. and treatment aims to retum the bloodpressure to normal. In the past one of the drugs trialed as a treatment for essential hypertension was hexamethonium, an antagonist of acetylcholine nicotinic recepbrs that is selective for the subtype of nicotinic receptors found in autonomic ganglia.
(a) What effect would you expect hexamethonium have on the comml of blood pressure? Explain your reasoning.
[10 min]
(b) In addition to a fall in blood pressure, what other effects would you expect hexamethonium to have?
[10 min]

 

2004 - Joe Smith (age 63) goes to see his GP. He complains that he feels dizzy whenever he stands up, although the dizziness passes quickly. This has come on gradually over several months.
Question 8.
Outline 2 hypotheses you consider most likely to account for Joe's dizziness. Explain your reasoning for each hypothesis.
(8 marks)
Question 9.
What further information would you seek from history, examination or investigations to test your hypotheses? Explain how the information would help to confirm or eliminate your hypotheses or distinguish between them.
(17 marks)

 

Joe's blood pressure while sitting is 135/80 mmHg, but falls to 95/70 when he stands up. Joe's heart rate while sitting is 80 beats per minute, and does not change when he stands up.
Joe's skin feels warm and dry. His pupils are slowly responsive to light and of unequal size. The GP asks Joe whether he has been producing a normal amount of urine. Joe assures the doctor that he produces a normal amount of urine of a normal colour, but comments that sometimes it's difficult to get the flow started when he goes to the toilet. Joe has no signs of dehydration.
Question 10.
What is your preferred hypothesis now? Explain your reasoning.
(15 marks)
Question 11.
Indicate any further questions you would seek to answer from history, physical examination or investigation to refine your hypothesis.
(5 marks)

 

2005 - Question 2.
Explain the role of the autonomic nervous system in keeping arterial blood pressure constant in a person who goes from a recumbent (lying down flat) position to standing.
(15 marks)

 

2004 - Question 3.
A drug is observed to produce the following effects:
dry mouth, reduced sweating , hypotension, increased blood flow to skin, dilation of the pupils, inability to focus on near objects
How is this drug acting? Explain your reasoning.
(5 marks)

 

2006 - Question 4.
The use of some drugs for treatment of central nervous system disorders is limited by unwanted
“antimuscarinic” side effects. (That is, their effects as antagonists of acetylcholine, acting at muscarinic
receptors.)
List 5 effects on organs or tissues outside the central nervous system that you would expect from such a
drug. For each effect, specify the location of the muscarinic receptors at which the drug is acting.
(5 marks)

 

2007 - Question 1.
(a) Name the major divisions and subdivisions of the peripheral nervous system.
(4 marks)
(b) An agricultural worker exposed to an organophosphate insecticide is given atropine to relieve his symptoms which include diarrhoea, wheezing and coughing. Explain how atropine acts and describe the rationale for its use in this situation.
(5 marks)
(c) A drug has been developed which inhibits the release of noradrenaline from sympathetic nerve terminals in a dose-related fashion. From your understanding of sympathetic control of the cardiovascular system, outline effects of a moderate dose of this drug on control of blood pressure.
(10 marks)

 

2008 - Question 3.
A 60 year old male has been diagnosed with a chronic disease that affects several body systems. The disease is known to cause damage to peripheral nerves.
His symptoms include:
rapid heart rate
dizziness when he rises quickly from sitting or lying down
difficulty urinating, both in starting to urinate and emptying the bladder
diarrhoea
reduced cutaneous sensation in his feet
For each symptom, state the particular part of the peripheral nervous system that has been damaged.
(6 marks)