Last MCQs Physiology 2

Explanation
Oxytocin actually increases uterine contractions. It is a hormone released by the pituitary gland that plays a crucial role in childbirth and breastfeeding. Oxytocin stimulates the muscles in the uterus to contract, which helps in the progression of labor and delivery. It also promotes the release of breast milk during breastfeeding. Therefore, the statement that oxytocin decreases uterine contractions is incorrect.

Explanation
Menstruation is the monthly shedding of the endometrium, the lining of the uterus, when pregnancy does not occur. This shedding is caused by a breakdown of the endometrial tissue, which is triggered by hormonal changes in the body. The breakdown of the endometrium leads to bleeding, which is what is commonly known as a period. Therefore, the statement "Menstruation is caused by a breakdown of endometrium in the womb" is true.

Explanation
Prolactin releasing hormone is not released by the plasma. Instead, it is released by the hypothalamus in the brain. The hypothalamus produces and releases various hormones that regulate the release of hormones from the pituitary gland, including prolactin releasing hormone.

Explanation
gonadotropin

Explanation
Involuntary control of breathing is regulated by the autonomic nervous system (ANS). The ANS is responsible for controlling various involuntary functions in the body, including breathing. This means that even when we are not consciously thinking about it, our body continues to regulate our breathing rate and depth to ensure the proper exchange of oxygen and carbon dioxide in the lungs. Therefore, the statement "Involuntary control of breathing is regulated by the ANS" is true.

Explanation
Central chemoreceptors are specialized cells located in the brain that are responsible for sensing changes in the levels of carbon dioxide (CO2) and pH in the blood. These receptors indirectly respond to hypoxemia, which is a decrease in the oxygen levels in the blood, through the changes in CO2 levels. When oxygen levels drop, CO2 levels tend to rise, leading to an increase in acidity (lower pH) in the blood. This change in pH is detected by central chemoreceptors, triggering an increase in respiratory rate to remove excess CO2 and restore the blood's pH balance. Therefore, central chemoreceptors do not directly respond to hypoxemia but rather indirectly through CO2 and pH changes.

Explanation
180

Explanation
proximal convoluted tubule

Explanation
Glucose reabsorption from the nephron is a sodium-dependent process because it occurs through a mechanism called secondary active transport. In this process, sodium ions are actively transported out of the nephron cells into the surrounding interstitial fluid, creating a concentration gradient. This gradient drives the passive transport of glucose molecules from the nephron lumen into the cells, facilitated by glucose transporters. Therefore, the reabsorption of glucose from the nephron relies on the presence of sodium ions.

Explanation
The Loop of Henle is a structure in the kidney responsible for reabsorbing water and electrolytes from the urine. The descending limb of the Loop of Henle is permeable to water, allowing water to passively diffuse out of the urine and into the surrounding tissues. This reabsorption of water helps to concentrate the urine and conserve water in the body. Therefore, it is true that reabsorption of water occurs in the descending limb of the Loop of Henle.

Explanation
If the renal clearance of a substance is greater than the glomerular filtration rate (GFR), it means that the substance is being removed from the blood at a faster rate than it is being filtered by the kidneys. This indicates that the substance is being actively secreted into the nephron, as the kidneys are actively removing it from the blood and excreting it into the urine. Therefore, the statement is true.

Explanation
An increase in plasma osmolality triggers the release of antidiuretic hormone (ADH) from the pituitary gland. ADH acts on the kidneys to increase water reabsorption, reducing urine output and helping to restore normal plasma osmolality. Therefore, the correct answer should be True, not False.

Explanation
An increase in the hormone ADH would lead to the production of a more concentrated urine. ADH, or antidiuretic hormone, is responsible for regulating the amount of water reabsorbed by the kidneys. When ADH levels rise, the kidneys reabsorb more water from the urine, resulting in a smaller volume of urine with a higher concentration of waste products. This helps to conserve water in the body and maintain proper fluid balance. Therefore, the statement is true.

Explanation
Aquaporin 2

Explanation
A negative free water clearance of -1.5ml/min indicates that the kidneys are unable to concentrate urine and are instead excreting excess water. This is commonly seen in individuals who are dehydrated because their bodies are trying to conserve water. In a dehydrated state, the kidneys prioritize water conservation over concentrating urine, resulting in a negative free water clearance value. Therefore, the given answer "True" is correct.

Explanation
A high dietary salt intake will not increase circulating levels of Angiotensin 2. Angiotensin 2 is a hormone that constricts blood vessels and increases blood pressure. While a high salt intake can lead to an increase in blood pressure, it does not directly affect the levels of Angiotensin 2 in the circulation.

Explanation
Aldosterone is a hormone produced by the adrenal glands that plays a key role in regulating sodium and potassium levels in the body. One of its main functions is to stimulate the activity of the epithelial sodium channel (ENaC) in the collecting duct of the kidneys. This channel allows for the reabsorption of sodium from the urine back into the bloodstream, which helps to maintain proper fluid balance and blood pressure. Therefore, the statement that aldosterone stimulates the activity of the epithelial sodium channel in the collecting duct is true.

Explanation
An increase in medullary blood flow refers to an increase in blood flow to the medulla, the innermost part of the kidney. This increased blood flow can lead to an increase in urine production, known as diuresis, as well as an increase in the excretion of sodium in the urine, known as natriuresis. Therefore, it is true that an increase in medullary blood flow generally promotes both diuresis and natriuresis.

Explanation
Increased aldosterone secretion does not stimulate renal potassium retention. In fact, aldosterone promotes the excretion of potassium by the kidneys. It acts on the distal tubules and collecting ducts of the kidneys to increase the reabsorption of sodium and the excretion of potassium. This helps to maintain electrolyte balance in the body. Therefore, the correct answer is false.

Explanation
Under normal conditions, the majority of calcium that is filtered in the glomeruli is reabsorbed in the nephrons. This is an important process to maintain calcium homeostasis in the body. The kidneys play a crucial role in regulating calcium levels by reabsorbing the majority of filtered calcium back into the bloodstream. This helps to prevent excessive calcium loss in the urine and ensures that the body maintains adequate levels of calcium for various physiological functions. Therefore, the statement is true.

Explanation
The phosphate buffer system is not the major chemical buffering system in ECF. The major buffering system in extracellular fluid (ECF) is the bicarbonate buffer system. This system helps maintain the pH balance in the blood by regulating the levels of carbon dioxide and bicarbonate ions. Phosphate buffer system, on the other hand, plays a more significant role in buffering intracellular fluids. Therefore, the correct answer is false.

Explanation
Persistent vomiting can lead to the loss of hydrogen ions (H ions) from the body. H ions play a crucial role in maintaining the acid-base balance in the body. When there is a loss of H ions, the pH level of the blood increases, making it more alkaline. This condition is known as metabolic alkalosis. Therefore, it is true that the loss of H ions due to persistent vomiting can result in metabolic alkalosis.

Explanation
In the proximal tubule of the kidney, bicarbonate ions are reabsorbed back into the bloodstream. This process requires the secretion of hydrogen ions into the tubule. The hydrogen ions combine with the filtered bicarbonate ions to form carbonic acid, which then dissociates into water and carbon dioxide. The carbon dioxide can easily diffuse back into the tubule cells, where it is converted back into bicarbonate ions. This bicarbonate is then transported back into the bloodstream. Therefore, the statement is true - reabsorption of bicarbonate in the proximal tubule does indeed require the secretion of hydrogen ions.

Explanation
Respiratory alkalosis is a condition characterized by decreased levels of carbon dioxide in the blood, leading to increased pH. In this condition, the bicarbonate buffering reaction actually shifts to the left, not to the right. This occurs in order to compensate for the decreased levels of carbon dioxide by decreasing the production of bicarbonate ions. Therefore, the statement that respiratory alkalosis results in an immediate shift in the bicarbonate buffering reaction to the right is false.