Question

In which order do the events of antidiuretic hormone (ADH) secretion stimulated by plasma osmolarity occur? 1. Osmoreceptors are activated. 2. Water is reabsorbed from renal tubules. 3. Plasma osmolarity is increased. 4. Antidiuretic hormone (ADH) is released. 5. Extracellular fluid is decreased.

Answer 1

The order of events for ADH secretion due to increased plasma osmolarity starts with an increase in osmolarity, followed by osmoreceptor activation, ADH release, water reabsorption from the kidneys, and a decrease in extracellular fluid.

Step-by-step explanation:

In response to increased plasma osmolarity, the sequence of events for antidiuretic hormone (ADH) secretion is as follows:

1. Osmoreceptors are activated by the high osmolarity.
2. Antidiuretic hormone (ADH) is released from the posterior pituitary gland.
3. ADH makes the renal tubules more permeable to water, leading to water reabsorption.
4. Increased water reabsorption dilutes the blood, lowering the plasma osmolarity towards normal levels.
5. As plasma osmolarity decreases, the stimulation of osmoreceptors is reduced, which in turn decreases the secretion of ADH.

Thus, the correct order of events is 3 (Plasma osmolarity is increased), 1 (Osmoreceptors are activated), 4 (Antidiuretic hormone (ADH) is released), 2 (Water is reabsorbed from renal tubules), 5 (Extracellular fluid is decreased).