When human blood plasma volume decreases and osmotic pressure rises due to dehydration, a homeostatic endocrine feedback mechanism is activated. Arrange the following physiological events of this hormonal response in the correct chronological sequence from initial detection to the restoration of water balance:
- 1Osmoreceptors in the hypothalamus detect an elevated solute concentration in the blood plasma.
- 2The posterior lobe of the pituitary gland secretes antidiuretic hormone (ADH) into the bloodstream.
- 3ADH binds to receptor sites on epithelial cells of the renal distal convoluted tubules and collecting ducts, increasing aquaporin permeability.
- 4An increased volume of water is osmotically reabsorbed from the renal filtrate back into the surrounding blood capillaries.
- 5Blood osmotic pressure decreases to the normal set point, inhibiting further release of ADH via negative feedback.
Answer
The correct chronological sequence is: 1) Hypothalamic osmoreceptors detect elevated blood solute concentration; 2) Posterior pituitary secretes ADH into the bloodstream; 3) ADH increases water permeability in kidney tubule cells; 4) Water is reabsorbed from renal filtrate into blood capillaries; 5) Normal blood osmotic pressure is restored, initiating negative feedback.
The physiological cascade starts with hypothalamic osmoreceptors detecting elevated blood osmotic pressure. This leads directly to ADH secretion from the posterior pituitary into the blood. ADH targets kidney nephrons to increase the permeability of distal convoluted tubules and collecting ducts, facilitating osmosis of water back into blood capillaries. Finally, as normal plasma osmolality is achieved, negative feedback reduces ADH secretion.
Step-by-Step Solution
Key Concept
Osmoregulation and negative feedback control via antidiuretic hormone (ADH)
Estimated Time:2m 0s