MDS PREP
What is the primary function of the theophylline?
1) It acts as a muscle relaxant
2) It increases intracellular cAMP levels
3) It inhibits acetylcholine receptors
4) It stimulates the release of insulin
Theophylline is a methylxanthine derivative that acts as a phosphodiesterase inhibitor, leading to increased intracellular cyclic AMP (cAMP) levels. This can stimulate various cellular processes, including smooth muscle relaxation and bronchodilation in the respiratory system. It also enhances insulin secretion.
MCQ: The primary site of absorption for:
1) Calcium - Jejunum
2) Iron - Jejunum
3) Vitamin B12 - Duodenum
4) All of the above
The primary site of absorption for calcium, iron, and vitamin B12 is the jejunum, making the answer "All of the above" correct.
What is the primary mechanism of sodium reabsorption in the distal convoluted tubule and collecting ducts?
1) Passive diffusion
2) Active transport with sodium-potassium ATPase pump
3) Facilitated diffusion
4) Countercurrent exchange with hydrogen ions
The primary mechanism of sodium reabsorption in the distal convoluted tubule and collecting ducts is active transport with the sodium-potassium ATPase pump.
Which vitamin is the most important antioxidant in the body, acting in the lipid phase of membranes?
1) Vitamin C
2) Vitamin A
3) Vitamin E (tocopherol)
4) Vitamin B
Vitamin E (tocopherol) is the most important antioxidant in the body, acting in the lipid phase of membranes to protect against oxidative damage.
What is the transport maximum for glucose reabsorption in the kidneys?
1) 125 mg/min
2) 250 mg/min
3) 375 mg/min
4) 500 mg/min
Physiology
Answer: 3
The transport maximum for glucose is about 375 mg/min, beyond which it is not fully reabsorbed and begins to appear in the urine.
Which of the following statements about Secretin is true?
1) It is structurally similar to insulin.
2) It is structurally similar to glucagon.
3) It stimulates the release of hydrochloric acid by the stomach.
4) It is secreted in response to high blood glucose levels.
Secretin is structurally similar to glucagon, which is involved in glucose metabolism and regulation.
What is the primary effect of excitatory postsynaptic potentials (EPSPs) on the excitability of a neuron?
1) Depolarization
2) Hyperpolarization
3) No change in excitability
4) Initiation of an action potential
Answer: 1) DepolarizationExplanation: EPSPs occur when the neurotransmitter binds to postsynaptic receptors that open sodium channels, allowing sodium ions to flow into the neuron and causing the membrane to depolarize. This increases the excitability of the neuron, bringing the membrane potential closer to the threshold for action potential firing.
What is the primary mechanism responsible for the reabsorption of sodium in the distal tubules and collecting ducts of the nephron?
1) Sodium-hydrogen exchange
2) Sodium-glucose cotransport
3) Sodium-potassium-2-chloride cotransport
4) Sodium-phosphate cotransport
E) Sodium-chloride symport
The primary mechanism for sodium reabsorption in the distal tubules and collecting ducts is sodium-hydrogen exchange, which occurs through the NHE3 transporter. This allows for the reclamation of sodium while maintaining the acid-base balance by exchanging sodium for hydrogen ions, which are then secreted into the tubular lumen.