Free FMGE Physiology questions

Explanation

The first heart sound occurs at the beginning of ventricular systole due mainly to closure of the atrioventricular valves. S2 results from closure of the aortic and pulmonary valves.

Explanation

The QRS complex represents ventricular depolarization. Ventricular repolarization is represented primarily by the T wave.

Explanation

The hyperpolarization-activated funny current contributes to spontaneous diastolic depolarization in pacemaker cells. This helps the SA node reach threshold rhythmically.

Explanation

Greater ventricular filling stretches myocardial fibers within physiological limits, enhancing force of contraction. This is the basis of the Frank-Starling mechanism.

Explanation

Surfactant reduces surface tension at the air-liquid interface of alveoli. This improves compliance and helps prevent collapse, particularly of smaller alveoli.

Explanation

Both ventilation and perfusion decrease toward the apex, but perfusion decreases proportionately more. Therefore the V/Q ratio is higher at the lung apex.

Explanation

Increased 2,3-BPG reduces hemoglobin's affinity for oxygen and shifts the curve to the right. Increased temperature, PCO2, and H+ have a similar effect.

Explanation

An ideal filtration marker has clearance equal to GFR. Inulin classically fulfills these physiological characteristics.

Explanation

PAH entering the kidney is removed from plasma by both glomerular filtration and proximal tubular secretion. Its extraction is therefore high enough for clearance to approximate effective renal plasma flow.

Explanation

Metabolic acidosis stimulates respiratory compensation through increased ventilation, lowering PCO2. Renal compensation also develops but is slower.

Explanation

The thick ascending limb reabsorbs ions through NKCC2 but is relatively impermeable to water. It is therefore an important diluting segment and contributes to the medullary osmotic gradient.

Explanation

Cortisol is a steroid hormone and binds an intracellular glucocorticoid receptor. Peptide hormones and catecholamines primarily use cell-surface receptors.

Explanation

Dopamine released from the hypothalamus exerts tonic inhibitory control over prolactin secretion. Interruption of this pathway can result in hyperprolactinemia.

Explanation

Skeletal muscle end plates contain muscle-type nicotinic acetylcholine receptors, designated Nm. Their activation generates the end-plate potential.

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Calcium binding to troponin C shifts the troponin-tropomyosin complex away from actin's myosin-binding sites. Cross-bridge cycling can then occur.

Explanation

Secretin is released from duodenal S cells in response to acid. It promotes bicarbonate-rich pancreatic and biliary secretion.

Explanation

Before ovulation, sustained high estradiol changes from negative to positive feedback on the hypothalamic-pituitary axis. This produces the LH surge responsible for ovulation.

Explanation

The dorsal column system transmits vibration, discriminative touch, and conscious proprioception. Lower-body fibers ascend through the fasciculus gracilis.

Explanation

Muscle spindles detect changes in muscle length and provide the afferent signal for the stretch reflex. Golgi tendon organs mainly monitor muscle tension.

Explanation

Isotonic saline remains predominantly within the extracellular compartment and does not significantly change extracellular osmolality. Therefore little net water movement occurs across cell membranes.