Water Physiology Flashcards

What happens to central blood volume when a person is immersed to the neck in water?

Answer: It increases by about 700 mL

Hydrostatic pressure pushes peripheral blood toward the thorax, raising central blood volume by roughly 700 mL.

Which hormone's release is suppressed during neck-deep immersion, contributing to diuresis?

Answer: Antidiuretic hormone (ADH)

Increased central blood volume suppresses ADH (and renin/aldosterone), increasing urine output.

Compared with land, resting heart rate during thermoneutral neck-deep immersion typically:

Answer: Decreases slightly

Increased stroke volume from greater venous return lets heart rate fall slightly at rest.

Approximately how much does stroke volume increase with immersion to the neck?

Answer: 25-35%

Stroke volume rises roughly 25-35% due to higher preload from hydrostatic pressure.

Which statement about vital capacity during chest-deep immersion is correct?

Answer: It decreases roughly 6-12%

Hydrostatic pressure on the chest wall and increased thoracic blood volume reduce vital capacity.

Which respiratory muscle work changes most noticeably during immersion?

Answer: Inspiratory work increases

Inspiration must overcome water pressure on the chest, increasing work of breathing.

Water's specific heat compared with air is about:

Answer: 1,000 times greater

Water holds about 1,000 times more heat per volume than air, so it conducts heat away rapidly.