Nutritrion D.2: Water and Electrolyte Balance Flashcards
D.2.1. State the reasons why humans cannot live without water for a prolonged period of time.
- basic substance for all metabolic processes in the body
- enables transport of substances essential for growth
- allows for the exchange of nutrients and metabolic end products
- regulates body temperature
D.2.2. State where extracellular fluid can be located throughout the body
- the blood plasma and lymph
- saliva
- fluid in the eyes
- fluid secreted by glands and the digestive tract
- fluid surrounding the nerves and spinal cord
- fluid secreted from the skin and kidneys
D.2.3. Compare water distribution in trained and untrained individuals
Muscle: 65–75% water; fat: 5–20%.
Trained:
- Training increases water in cells.
- More muscle = more water.
- Higher intra & extracellular water.
- More glycogen = more stored water.
- Trained athletes have more dilute sweat.
- Increased blood plasma volume.
- Better temperature regulation.
D.2.4. Explain that homeostasis involves monitoring level of variables and correcting changes in levels by negative feedback mechanisms
- Low fluid levels trigger hypothalamus receptors
- Hypothalamus signals pituitary to release ADH
- ADH increases kidney water reabsorption
- Regulated by a negative feedback loop
D.2.5. Explain the roles of the loop of Henlé, medulla, collecting duct and ADH in maintaining the water balance of the blood.
Loop of Henlé:
- Absorbs solute/water
- Descending loop - water moves out and into medulla
- Ascending loop - Sodium Chloride (NaCl) moves out
D.2.5. Explain the roles of the loop of Henlé, Medulla, collecting duct and ADH in maintaining the water balance of the blood.
ADH:
- Antidiuretic Hormone (Vasopressin)
- Hormone made by the hypothalamus in the brain and stored in the posterior pituary gland
- Tells kidney how much water to conserve
- Constantly regulates and balances the amount water in blood
D.2.6. Describe how the hydration status of athletes can be monitored
- urine colour
- urine osmolarity: the amount of solute per unit volume
- variation in body mass loss
D.2.7. Explain why endurance athletes require a greater water intake.
- Water intake helps to maintain hydration
- Thermoregulation
- Maintain plasma volume
- Prevent decline in athletic performance
- May lead to serious health problem
- May result in stress on the cardiovascular system
- May result in inadequate heat transfer to the skin and environment
- Associated with increased plasma osmolality
- Decreased plasma volume
- May affect intra and extracellular electrolyte balance
D.2.8. Discuss the regulation of electrolyte balance during acute and chronic exercise.
SPORTS INDUCED FLUID ANDE LECTROLYTE IMBALANCES:
- Hypohydration
- Hyponatremia
- Hypokalemia
D.2.5. Explain the roles of the loop of Henlé, Medulla, collecting duct and ADH in maintaining the water balance of the blood.
Medulla:
- The renal medulla - internal portion of kidney
- Where primary functions of the organ occur
- Filtering of waste materials and elimination of fluid from body
D.2.5. Explain the roles of the loop of Henlé, Medulla, Collecting duct and ADH in maintaining the water balance of the blood.
Collecting duct:
- Water is reabsorbed
- Collects filtrate from nephrons
- Lined with ADH-sensitive epithelium
- ADH allows water reabsorption into blood
- Without ADH, water is lost as dilute urine
Hypohydration
- Water loss > electrolyte loss, especially in hot conditions
- Caused by losing ≥2% body water without replacement
- Speeds up fatigue and hinders cooling
- 2% loss reduces physical performance
- 5% loss risks serious dehydration and halts activity
Hyponatremia
- 2–3+ liters of water can dilute electrolytes
- Caused by excessive water intake
- Symptoms: mental changes, coma, seizures
- Sodium <130 MEQ/L linked to altered thinking
Hypokalemia
- A lower than normal potassium level in your blood stream
- Potassium loss in sweat is minimal for exercise under 30 mins
What are the two fluid compartments?
- Intracellular fluid compartment
- Extracellular fluid compartment
What is intracellular fluid?
- Fluid enclosed in cells by their plasma membranes
- Principal component of the cytosol/cytoplasm
- Makes up ~60% of total water in human body
- Fluid volume is very stable
- Too little water → cell is too concentrated = cannot function normally
- Too much water → cell may burst and destroyed
What is extracellular fluid?
- The fluid that is not contained within the cells
- Remaining 1/3 of body water’s content
- 20% of extracellular fluid is in plasma
- The rest are in joints, lymph, saliva, etc…
What is homeostasis?
The tendency to resist change to maintain a stable internal environment, usually via negative feedback.
What is negative feedback loop?
A regulatory process where a stimulus triggers an opposite response to maintain balance
