MDS PREP
MCQ: The macula densa is found in:
1) The proximal convoluted tubule
2) The loop of Henle
3) The distal convoluted tubule
4) The collecting duct
The macula densa is found in the distal convoluted tubule, where it senses sodium chloride concentration and helps regulate glomerular filtration rate.
What is the primary action of endorphins on the body?
1) Inhibition of pain
2) Stimulation of growth
3) Regulation of mood and emotions
4) Increased blood pressure
E. Regulation of sleep-wake cycle
Endorphins, particularly ?-endorphin, are opioid peptides that act as natural painkillers. They are released during stress and pain and bind to opioid receptors in the brain and spinal cord to inhibit the transmission of pain signals. While they do have secondary effects on mood and stress response, their primary function is pain inhibition.
Which of the following is NOT a secondary bile acid?
1) Cholic acid
2) Deoxycholic acid
3) Lithocholic acid
4) Chenodeoxycholic acid
Physiology
Answer: 1
Cholic acid is a primary bile acid, while deoxycholic acid and lithocholic acid are secondary bile acids formed by bacterial action in the colon.
Which hormone is primarily responsible for the conversion of 7-dehydrocholesterol to cholecalciferol in the skin?
1) Parathyroid hormone (PTH)
2) Vitamin D
3) Ultraviolet B (UV2) light
4) 25-hydroxyvitamin D3
Ultraviolet B (UVB) light is primarily responsible for the conversion of 7-dehydrocholesterol to cholecalciferol (vitamin D3) in the skin.
The glomerular filtration barrier consists of:
1) Endothelial cells
2) Basement membrane
3) Podocytes
4) All of the above
The glomerular filtration barrier is a three-layered structure composed of endothelial cells of the glomerular capillaries, the basement membrane, and the podocytes (visceral epithelial cells of Bowman's capsule). These layers work together to filter blood, allowing small molecules to pass into the nephron while retaining larger ones.
What is the function of titin in muscle contraction?
1) It provides the structural framework for the sarcomere
2) It acts as a bridge between actin and myosin filaments
3) It is the primary contractile protein in muscle fibers
4) It regulates muscle length during contraction and relaxation
Titin acts as a scaffold that supports the alignment of the thick and thin myofilaments in muscle cells, maintaining the integrity of the sarcomere structure during contraction.
What is the significance of the intestinal phase of gastric acid secretion?
1) It is responsible for the majority of acid secretion
2) It is primarily responsible for the inhibition of acid secretion
3) It is only triggered by the thought of food
4) It is not a significant phase of gastric acid secretion
The intestinal phase of gastric acid secretion is primarily responsible for the inhibition of acid secretion, helping to regulate the digestive process after food enters the intestine.
The first heart sound relates to
1. Closure of the A-V valves
2. Opening of the A-V valves
3. Excitation of the auricles
4. Closure of the aortic valve
Physiology
Answer: 2
The first heart sound relates to Opening of the A-V valves