water balance. water balance in a general sense: increased water intake = increase urine output ...
TRANSCRIPT
WATER BALANCE
Water Balance
In a general sense: increased water intake = increase urine
output exercise or decreased water = reduce urine
output These adjustments involve the
interaction of the body’s two communication systems: the nervous system the endocrine system
Regulating ADH
Antidiuretic Hormone (ADH) Helps regulate the osmotic
pressure of body fluids by causing the kidneys to increase water reabsorption
Results in a more concentrated urine, therefore conserving body water
ADH is produced by specialized nerve cells in the hypothalamus
Stored and released by the pituitary gland
Regulating ADH
Specialized nerve receptors in the hypothalamus detect changes in water (osmotic) pressure. osmoreceptors
When our water level decreases, blood becomes more concentrated (more solutes, less water) The osmotic pressure of the blood increases
Water then moves into the bloodstream, causes the cells of the hypothalamus to shrink
When the hypothalamus shrinks, a nerve message is sent to the pituitary, signals the release of ADH, travels through blood vessels
to the kidneys Kidneys respond be reabsorbing more water
Regulating ADH
The shrinking of the cells of the hypothalamus also initiates a behavioural response Thirst!
Opposite Response to Increased water levels: If more water is taken in, it is absorbed by the blood and
the concentration of solutes in the blood decreases. as the volume of water consumed increases, osmotic
pressure decreases As the blood becomes more dilute, fluids move from the
blood into the hypothalamus. The cells of the hypothalamus swell, and nerve messages
to the pituitary stop. Less ADH is released, and less water is reabsorbed from
the nephrons.
ADH and the Nephron
Approximately 85% of the water filtered into the nephron is reabsorbed in the proximal tubule. The proximal tubule is very permeable to water BUT most of the rest of the nephron is NOT
Without ADH, the remaining 15% of the H2O filtered into the nephron will be lost
ADH makes the upper part of the distal tubule and collecting duct permeable to water
Water is drawn from these areas due to the high concentration of NaCl
As more water is drawn out, the remaining filtrate (urine) in the nephron becomes more concentrate
Alcohol and ADH
Alcohol impedes the release of ADH
How does this explain some of the symptoms related to excessive alcohol consumption Dehydration Frequent Urination Headaches Dizziness
Alcohol and ADH
…because I know you are probably falling asleep
Class Activity: Design a short 3-5 minute skit that
demonstrates your understanding of ADH, water balance, and how alcohol interferes with the regular function of ADH
Must involve some moving around!
Kidneys and Blood Pressure
The kidneys also plays a role in the regulation of blood pressure By adjusting for blood volume
Aldosterone = A hormone called that acts on the nephrons to increase Na+ reabsorption (salt)
The hormone is produced in the adrenal glands Located above the kidneys.
As NaCl reabsorption increases, the concentration gradient increases Therefore more water moves out of the nephron by
osmosis.
Kidneys and Blood Pressure
Conditions that lead to increased fluid loss can decrease blood pressure Reduces the delivery of oxygen and nutrients to tissues
What are some examples of such conditions? Low Blood Pressure is detected by the nephron, and
the enzyme angiotensin is released. Angiotensin has two important functions
1. Causes constriction of blood vessels.2. Stimulates the release of aldosterone from the
adrenal gland. Aldosterone acts on the nephron to increase Na+
transport.