Systemic Anatomy and Physiology –
This case study is designed to help you link the concepts we are learning in lectures with a “real-life” scenario. You will need to use the lecture material as well as other resources to help you answer the questions. This case study will assess the endocrine, urinary and gastrointestinal systems
Please make sure you do the following:
You will be assessed not only on content but the arrangement in terms of a logical argument based on scientific evidence (referencing appropriately). Please refer to the marking rubric for the full marking criteria.
Jacob and his mates went to an all-you-can-eat seafood buffet. About a month later he starts to feel unwell. He develops a fever, he is nauseous, starts vomiting and has diarrhoea. This continues for several days and he is starting to feel quite weak. He also notices that he doesn’t have to urinate very often but when he does it is only a small amount of dark yellow urine.
The hormone responsible for maintaining water balance homeostasis is anti-diuretic hormone (ADH). Complete the following table outlining the feedback mechanism for ADH (2 marks).
|Site of production|
|Site of release|
Mechanisms of hormone action
|Impact on urine output|
What type of feedback loop is this and explain your reasoning? (2 marks)
Using an example from the endocrine system explain the other type of feedback loop. (2 marks)
After a week he has an appointment with his doctor. The doctor notices that his sclera (whites of his eyes) are yellow and doctor suspects that he jaundice possibly as a result of a hepatitis virus – but is not sure which type. He immediately sends Jacob for a blood and urine test to confirm. By the time Jacob makes it for his tests his urine has become a dark amber colour and his skin is turning yellow. The results of his test confirm the diagnosis of Hepatitis A. In addition, it was noted that his urine has high levels of potassium
The source of hepatitis A virus was determined to be the seafood from the buffet.
1. Outline the table regarding the feedback control of ADH hormone and its urine regulation (2 marks).
|Stimulus||Osmotic pressure within cells|
|Site of production||Hypothalamus|
|Site of release||Posterior Pituitary gland|
|Mechanisms of hormone action||Release of hormone from pituitary as per dehydration or physiological stress. The increased secretion of ADH causes an increase in plasma hormone concentration. This, in turn, increases the permeability of water in the distalconvolutingtubule and collecting ducts in the kidney . The increase in water reabsorption occurs, and urine excretion is reduced.|
|Impact on urine output||Urine release is stopped, and the osmolarity is restored in the blood.|
2. Explain with reason the nature of feedback control (2 marks)
The decrease of the osmolarity within the negative blood feedback reduces the activity of the hypothalamus. Hence, the osmoreceptor activities within the kidneys are reduced. This is a negative feedback mechanism since the water moves out of the kidney down its concentration gradient back into the bloodstream through the Aquaporin-2 channels.
3. Using an example from the endocrine system explain the other type of feedback loop. (2 marks)
The endocrine system also has positive feedback loop where the stimulus increased the outcome. During blood clotting, the clotting factors stimulate the influx of repair cells and platelets into the damaged tissue . The chemicals attract the plalets and helping them to coagulate in the wound and in turn attract more platelets to the region to stop the blood from flowing out of the body.
4. Explain the process of urine formation (3 marks)
Glomerular Filtration:The flow of blood from the glomerulus imparts a pressure pushing the water molecules and solutes into the capsule from the capillaries. The membrane filtration process begins in the next step to eliminate the larger proteins and blood cells. The filtrate is passed on to the nephron .
Tubular reabsorption:Inside the nephrons, the renal tubules the necessary substances are reabsorbed through the tubes. This mostly includes vital nutrients like essential ions, glucose, very small proteins and amino acids etc.
Tubular secretion: The tubules secrete waste ions and hydrogen ions through the capillaries. The remaining filtrate flows out into a collecting duct, then to a renal pelvis, into the ureter and down to its bladder
5. Using your knowledge of the hormones involved in the urinary discuss what might have caused the high levels of potassium in Jacob’s urine. (3 marks)
Potassium as well as sodium is responsible for controlling the water balance in the body. The sodium levels in the body are indirectly proportion to the level of potassium in the body. High levels of potassium in urine are indicated by lowered potassium level in blood. The disruption of the aldosterone mediated water balance in the body is the result of incessant dehydration in Jacob. The retention of the potassium in kidneys is a result of the failure in aldosterone-mediated regulation in the patient’s body. In addition to this, the disruption of the liver function in Jacob resulted in the renal failure . The conditions resulted in the high potassium content in Jacob’s urine sample.
6. Describe the pathophysiology of diarrhoea and explain how it causes Jacob’s dehydration, lethargy and weakness (5 marks)
The diagnosis of Jacob indicated that he acquired inflammatory or infectious type of diarrhoea. In this type of diarrhoea, the pathogen generally destroys the epithelial layer of the intestine. This disrupts the absorptive characteristics of the inner intestinal walls and excessive loss of water can be observed. The pathophysiology involved includes the release of cytokines by the immune system of the patient in response to a viral attack, in this case, Hepatitis A. The cytotoxins are released by the inflammatory cells to destroy the viral infected epithelial tissue. The increased influx of inflammatory cells, platelet-activating factors and prostaglandins increase the level of cytokines in the affected area through positive feedback loop. The white blood cells on the other hand release reactive oxygen species to kill the virus-infected cells in the intestine. The new cells generated in the region do not possess the cellular morphology to absorb the water through canal. Therefore, prolonged diarrhoea is experienced causing dehydration, vomiting and loss of sodium from the body.