Hemorrhage causes a critical loss of blood volume resulting in hypovolemia and hypotension, which activate various vital homeostatic mechanisms to restore circulatory stability. These responses include hormonal changes, vascular receptor signaling, and adjustments in kidney function.

Key Homeostatic Responses After Hemorrhage

A. Increased Release of Vasopressin (Antidiuretic Hormone, ADH)

• Hypovolemia and hypotension stimulate vasopressin release from the posterior pituitary.

• Vasopressin conserves water by increasing water reabsorption in the kidneys and acts as a vasoconstrictor, helping maintain blood pressure.pubmed.ncbi.nlm.nih+2

• This response is a critical compensatory mechanism.

B. Increased Water Retention and Reduced Plasma Osmolality

• Although vasopressin promotes water retention, during hemorrhage,

• Plasma osmolality typically increases or remains stable due to hypovolemia.

• Water retention helps to restore volume without diluting plasma excessively.

• Therefore, plasma osmolality is not reduced; this statement is incorrect in hemorrhage.cvphysiology

C. Increased Rate of Afferent Discharge from Low Pressure Receptors of Vascular System (Cardiopulmonary Baroreceptors)

• Low-pressure baroreceptors located in the atria and pulmonary vessels decrease their afferent firing rate during hypovolemia as a result of reduced blood volume.

• Thus, the firing rate decreases, not increases.

• This statement is incorrect as it contradicts physiological observations.pubmed.ncbi.nlm.nih+1

D. Decreased Rate of Afferent Discharge from High Pressure Baroreceptors

• High-pressure baroreceptors in the carotid sinus and aortic arch respond to blood pressure.

• During hypotension, the firing rate decreases, leading to activation of sympathetic and hormonal responses.

• This statement is correct and aligns with known physiology.cvphysiology+1

Identifying the Incorrect Statements

• Statement A (Increased vasopressin release) is correct.

• Statement B (Increased water retention and reduced plasma osmolality) is incorrect — plasma osmolality is not reduced.

• Statement C (Increased discharge from low-pressure receptors) is incorrect — discharge decreases.

• Statement D (Decreased discharge from high-pressure receptors) is correct.

Answer Options Analysis

• (1) Only A — Incorrect, because A is true.

• (2) A and B — Incorrect, as A is true.

• (3) Only C — Incorrect, C is false but B also false.

• (4) B and D — Incorrect, D is true.

Both B and C are incorrect, but since the question asks which statement is NOT correct, and the option that fits B and D is (4) but D is correct, the best option covering incorrect is:

(4) B and D if considering only given options, but physiological data says D is correct.

Hence the most reasonable choice based on content provided in options is:

(4) B and D

However, if choosing per statement correctness:

• B is incorrect,

• C is incorrect,

• D is correct.

Most physiological literature indicates C is incorrect, so the best fit for all incorrect statements here is only C (option 3), or B and D if forced.

Conclusion

The physiological mistake in the statements includes that plasma osmolality is reduced (B) and low pressure baroreceptor firing increases (C), both of which are incorrect. The firing of high-pressure baroreceptors (D) decreases with hypotension and is correct.