Blood Volume, Sodium, and Hormonal Control

Why does sodium regulation affect blood volume

Water follows sodium, so changes in sodium retention influence ECF volume.

Vasopressin (ADH)

A hormone that increases kidney water reabsorption.

Effect of vasopressin on urine

It increases water reabsorption, reducing urine volume.

Hypothalamic osmoreceptors

Receptors that monitor fluid osmolarity and help regulate thirst and vasopressin release.

What stimulates hypothalamic osmoreceptors

Increased fluid osmolarity.

Response to increased osmolarity

Increased thirst and vasopressin secretion, helping restore water balance.

Effect of thirst on fluid balance

Drinking increases water intake and helps lower elevated osmolarity.

Left atrial volume receptors (LAVR)

Receptors that respond to substantial reductions in ECF volume.

What happens when LAVR are activated

Thirst and vasopressin secretion increase to help restore blood volume.

What reduction in ECF volume activates LAVR in the slides

A reduction greater than 7%.

Atrial natriuretic peptide (ANP)

A hormone released by the atria that promotes a reduction in blood volume.

Dipsogen

An agent that increases the urge to drink.

Polydipsia

Excessive thirst.

Polyuria

Excessive urine production.

Insensible water loss

Water loss that a person is not normally aware of, mainly through the lungs and skin.

Main sources of water intake

Drinking fluids, food, and metabolic water production.

Average daily water intake in the slides

Approximately 2,600 mL/day.

Main regulator of water output

The kidneys