I. Describe the role of the following hormones in the formation of urine, specifically explain the stimulus for their release, actions (decrease/increase GFR) and whether or not dilute/concentrated urine results):
ADH (Vasopressin) – ADH has an antidiuretic action that prevents the production of dilute urine. Formation of urine = in the DCT and collecting ducts, water movement out of the body is regulated by ADH. Stimulus for their release = lowered blood pressure or low salt or water concentration in the blood will stimulate the release of ADH from the posterior pituitary. Actions (decrease/increase GFR) = increased ADH would decreases the GFR and a decrease in ADH would increase GFR. Dilute/Concentrated Urine Results = if there is a high amount of ADH, water moves out and will produce concentrated urine and if ADH is absent water will not be reabsorbed and will produce dilute urine.
Stimulus for their release = if blood pressure drops dramatically this will trigger renin secretion from the JG cells, renin acts on angiotensinogen to form angiotensin I, angiotensin I is converted to angiotensin II therefore angiotensin II causes mean arterial pressure to rise and stimulates the adrenal cortex to release aldosterone. As a result, both systemic and glomerular hydrostatic pressure rises. Actions (decrease/increase GFR) = the efferent arteriole constricts, forcing blood to build up in the glomerulus, which maintains the GFR. The activation of the RAAS causes a decrease in GFR. Dilute/Concentrated Urine Results = activation of the Renin-Angiotensin-Aldosterone System will result in concentrated urine results.
Atrial Naturetic Pepetide (ANP) Hormone
Stimulus for their release = large increase in blood volume promotes release of ANP. Actions = result is more urinary output, less blood volume and decreased blood pressure. GFR will increase with the release of ANP. Dilute/Concentrated Urine Results = urine will be more dilute.
II. Diabetic patients (with hyperglycemia), typically have symptoms of polyuria, polydypsia and polyphagia. Define these terms and explain why these patients are polyuric and polydypsic.
Polyuria is the excessive secretion of urine. Polydypsia causes blood hyperosmolarity, this condition activates the thirst center in hypothalamus and makes the subject drink excessive water. Polyphagia is excessive eating.
Patients that are polyuric can have diabetes, diabetes mellitus, premenstrual syndrome, urinary stones. Common causes are bladder conditions, congestive heart failure, cystitis, or generalized anxiety disorder. Uncommon causes causes include anorexia nervosa, interstitial cystitis, and sickle-cell anaemia. Rare causes can be different types of cancer, cushing’s syndrome and pituitary tumors.
Patients that are polydypsic can possibly be diagnosed with diabetes insipidus and diabetes mellitus. Often as one of the initial symptoms, and in those who fail to take their anti-diabetic medications or whose dosages have become inadequate. It can also be caused by a change in the osmolality of the extracellular fluids of the body, hypokalemia, decreased blood volume and other conditions that create a water deficit. This is usually a result of osmotic diuresis. Polydipsia is also a symptom of anticholinergic poisoning. Zinc is also known to reduce symptoms of polydipsia by causing the body to absorb fluids more efficiently (reduction of diarrhea induces constipation) and it causes the body to retain more sodium; thus a zinc deficiency can be a possible cause. Antipsychotics can have side effects such as dry mouth that may make the patient feel thirsty.
III. A 45-year-old patient was admitted to the hospital with a diagnosis of cirrhosis of the liver. He is thin and malnourished. His abdomen is very large due to an accumulation of fluid in the abdominal cavity. His lower extremities are very swollen.
A. Explain why these changes have...
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