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SK299/K

Module Examination 2018

HUMAN BIOLOGY

PART 1

This Part carries 25 marks of the 75 marks available for this paper and consists of a single question. You should attempt ALL parts of the question. Write your answers in the answer book provided. You are advised to spend no more than 1 hour on this part of the paper.

Question 1

Dr Belinda Baker is a neurologist working at University College Hospital. She has been asked to consult on the case of a Teresa Battleforce, a 29-year old woman who was referred by her GP after experiencing extreme fatigue, incontinence and dizziness for the past two months. The images from Teresa’s MRI scan show three lesions in her brain that are characteristic of Multiple Sclerosis (MS). Dr. Baker explains to Teresa that MS is an autoimmune disorder affecting the brain and spinal cord in which the myelin protein is degraded. This affects neural communication and leads to symptoms of MS such as difficulties with vision and balance, muscle spasms and bladder problems.

1a. Briefly explain the role of myelin in neural communication.

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b. If the conduction velocity of an unmyelinated neuron is 2.3 m/s, how many milliseconds would it take an action potential initiated in the spinal cord to reach the bladder if it is carried by a myelinated neuron? Make sure to show your work and include units in your calculations. Round your answer to 1 decimal place.

Teresa is shocked by her diagnosis, as she had felt healthy and fit until just recently. At home, she searches the internet for information about the causes and prevalence of MS around the world. She discovers that the prevalence of MS varies for different countries and this is shown in Table 1

Table 1 Prevalence of MS in six countries and their proximity to the equator.

c. Using the graph paper provided, draw a bar chart showing the prevalence of MS in each country listed in Table 1, based on the country's distance from the equator in ascending order. Make sure to choose appropriate scales for the axes, label the axes, and include an appropriate title for the graph.

d. Looking at the graph you have just drawn, what general conclusion can be made about the relationship between the prevalence of MS in a country and the country's proximity to the equator?

e. Based on the data in Table 1, would you predict that levels of vitamin D are higher or lower in people with MS? In your answer, briefly explain your reasoning.

f. Briefly, describe one example of how a gene-environment interaction influences the phenotype of an individual (your example must be unrelated to MS).

g. What do the differences in risk of developing MS, based on migration patterns between countries during childhood versus adulthood, suggest about how vitamin D may influence the risk of developing this condition?

h. Name two other examples of autoimmune disease

PART 2

Answer ONE of the essay questions in this Part. Write your answer, starting on a new page, in the same answer book as you used for Part 1. You are advised to spend about 1 HOUR 20 MINUTES on this part of the paper. Your answer should include an essay plan and your essay, written in an appropriate essay style with proper sentences and paragraphs. You should include relevant drawings, tables and diagrams if you think these will enhance your answer. You are not required to provide references.

The question from this Part carries 35 marks of the 75 marks available for this paper.

Question 2

This question is based on the chosen topic Reproduction and fertility. Use your knowledge of SK299 to describe the processes of oogenesis and spermatogenesis from stem cell to mature gamete.

Question 3

This question is based on the chosen topic Musculoskeletal system. Use your knowledge of SK299 to describe the factors that affect the balance of bone resorption and deposition. In your answer, explain how the ACCESS risk factors contribute to the development of osteoporosis.

Question 4

This question is based on the chosen topic Stress

The term ‘stress epidemic’ is frequently used to describe the pressures of modern life. Is the stress response beneficial or harmful to human health? Use your knowledge of SK299 to discuss the beneficial and harmful effects of stress. In your answer, ensure you describe the physiological mechanisms and anatomical structures involved in the stress response.

PART 3

This Part contains one question and carries 15 marks of the 75 marks available for this paper. Answer ALL the parts of this question. Write your answers, starting on a new page, in the same answer book used for Part 1 and Part 2 (if you need another answer book, ask the invigilator). You should answer each part of this question in the style requested.

You are advised to spend no more than 40 MINUTES on this part of the paper, which carries 15 marks of the 75 marks available for this paper

Question 5

a. Based on his BMI score, what is Mark’s current weight classification?

b. Using the information shown in Figure 1, briefly describe (i) the role of ghrelin in the feeling of hunger and (ii) how working the night shift may be contributing to Mark’s weight gain.  

The GP also measures Mark’s blood pressure and notes that it is high. Concerned about his cardiovascular health, he checks the pulse in Mark’s leg and finds that it is weak. The GP notes that this may be a sign of atherosclerosis; the deposition of lipid on the inside of the walls of his arteries that would lead to narrowing of the vessel diameter.

c. Briefly explain how atherosclerosis can lead to increased blood pressure. When answering this question, ensure you refer to the cardiac output equation.

Armed with a weight loss plan that includes a modified diet and exercise plan, Mark notices that he is slowly losing weight. Hoping to speed up the weight loss, he decides to climb the steep hill behind his house on his daily walk. During one of these walks, Mark starts to feel unwell and collapses. He is rushed to the hospital, where a CT scan of his brain reveals that he has had an ischemic stroke in his left somatosensory cortex. Mark is quickly administered alteplase, a tissue plasminogen activator (TPA) analogue, to remove the clot in his blood vessel.

d. Briefly describe the mechanism of action by which tissue plasminogen activators promote the breakdown of blood

The TPA treatment is successful and Mark regains consciousness a couple of hours later. However, Mark notices that he has lost the feeling in his right hand and arm. 

e. Briefly discuss why damage to Mark’s left somatosensory cortex would cause a loss of sensation to touch and temperature on the right side of his body

Last updated: Jan 11, 2022 01:02 PM