University:
Western Sydney University
Course:
MEDI 2003 | Clinical Sciences 2
Academic year:

2024
Views:

369

Pages:

2
Author:

Mariam A. A.

RENAL WEEK 2 SAQ QUESTIONS STUDY GUIDE 1. Explain the role of ANP in renal autoregulation and state if this is an intrinsic or an extrinsic mechanism of renal autoregulation (2 marks) Answer: • • • ANP is an extrinsic mechanism of autoregulation. ANP is released by the atria chambers of the heart in response to high blood pressure. They act as angiotensin II competitive antagonists, meaning it will bind on the receptors where angiotensin II is meant to bind. These locations include blood vessels (thus prevent vasoconstriction), adrenal cortex (thus prevent the release of aldosterone), thalamus (thus prevent thirst), post. Pituitary gland (thus prevent the release of ADH). As a result these will not be able to exert their functions of fluid reabsorption and thus cause a reduction in blood pressure. 2. Explain at the molecular level cell response to shrinkage. (3 marks) Answer: • • • Imbalance between the intracellular and extracellular osmolarity (more on the outside). A gradient is set up -> Na+ and Ca2+ ion channels are activated -> Na+ and Ca2+ enter the cell. As these ions enter the cell, water will follow -> the cell will get back to its normal state. 3. Explain at the molecular level cell response to swelling. (3 marks) Answer: • • • Imbalance between the intracellular and extracellular osmolarity (more on the inside). Sets up a gradient -> activate membrane bound K+ and Cl- channels -> K+ and Cl- leave the cell. Water will follow the ions -> water leaves the cell -> cell returns back to its’ normal state. 4. Write down the filtration fraction equation. (1 mark) Answer: FF= GFR/RPF 5. Describe the stimulation of AVP release (2 marks) Answer: • • • • In response to low blood pressure, there will be decreased stretching of the juxtaglomerular, decreased Na+ sensing by the macula densa and activation of the SNS (release catecholamines on beta-1 receptors on JG cells) will trigger the activation of the JG cells. This will cause the release of renin which will be converted by angiotensinogen by the liver to angiotensin I via cleavage. This will then travel though the pulmonary circulation, where in the pulmonary capillaries it will be cleaved by angiotensin converting enzyme into angiotensin II. When angiotensin II binds on its’ receptors on the adrenal cortex ADH will get released. 6. Some parts of the nephron are permeable to water and others are not. Indicate which are: (3 marks) a. Always highly permeable (1 mark) b. Always impermeable (1 mark) c. Only if ADH is present (1 mark) Answer: a. descending loop of Henle and proximal convoluted tubule b. ascending loop of Henle c. distal convoluted tubule and collecting duct. 7. List and explain how FOUR metabolic reactions can liberate H+. (4 marks) Answer: 1. 2. 3. 4. - HCO3- buffering system: CO2 + H2O <-> H2CO3 <-> HCO3- + H+ Phosphate buffering system: H2PO4 <-> H+ HPO4 protein buffering system: HHb <-> H+ + Hb Ammonia buffering system: NH4 <-> NH3 + H+