Repeated USMLE Questions Step 1- 378

Q- A 30-year-old man tells you that when he carries a heavy lift, his muscle gives up all of a sudden. Which of the following actions is responsible for abrupt cessation of skeletal muscle contraction?

A- Activation of Golgi tendon organs

B- Activation of lower motor neuron

C- Activation of muscle spindles

D- Lower blood supply to the muscle

A- Activation of Golgi tendon organs- Prolonged stretch of a skeletal muscle results in activation of Golgi organs which leads to reflex relaxation of the muscle. Ischemia leads to gradual relaxation, not abrupt

Q- Which of the following factors directly stimulates the release of antidiuretic hormone (ADH)?

A- Decreased extracellular fluid osmolality

B- Decreased temperature

C- Increased blood volume

D- Increased extracellular fluid osmolality

D- Increased extracellular fluid osmolality- ADH secretion is triggered by increased extracellular fluid osmolality mainly due to dehydration leading to restoring water from losing it in urine.

Q- Laboratory tests for a patient are as follows:

Plasma creatinine concentration is 0.8 mg/dL

Urine creatinine concentration is 80 mg/dL

Urine volume is 1 ml/min

Which of the following is the creatinine clearance?

A- 50 ml/min

B- 100 ml/min

C- 200 ml/min

D- 300 ml/min

B- 100 ml/min- Creatinine clearance = urine volume X urine creatinine conc./ plasma creatinine conc.

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