Osmoregulation
Biological negative feedback systems can be controlled by the
nervous system or the endocrine system (or both).
Osmoregulation
- regulation of water and
ion balance in the body
- role of the kidney
The functional unit of the kidney
is called a nephron.
The nephron is responsible for:
• filtering the blood
• keeping the waste (urea) in the filtrate
• reclaiming water and nutrients (e.g. Na+, amino acids,
glucose)
The process of water reclamation is controlled by ADH
(antidiuretic hormone) and includes the following steps:
1) Glomerular Filtration
2) Tubular Reabsorption
3) Collection and secretion of wastes
ADH (Antidiuretic Hormone)
Diuresis: urine production
Diuretic: increased urine production
nephron is less permeable so less water is
reabsorbed from nephrons into the blood
Anti-Diuretic: decreased urine production
nephrons becomes more permeable so more
water is reabsorbed from nephron into blood
Increased ADH → decreased urine → decreased water loss
ADH will be produced by the body if:
1) the outside temperature is hot
2) liquid intake decreases
3) increase in physical activity
Stimulus (decreased blood pressure)
↓
Receptor (pressure receptors in blood vessels)
↓
Regulator (Brain - hypothalamus)
↓
Effector (ADH released and enters the collecting ducts)
↓
Response (nephrons permeability increases, more water is
reabsorbed into blood and blood pressure
increases, urine volume decreases)