SEHS Option D.2 Water and Electrolyte Balance

D.2.1 State the reasons why humans cannot live without water for a prolonged period of time.

-Basic substance for all metabolic processes. -Regulates body temperature. -Enable transport of substances essential for growth. -Exchange of nutrients and metabolic end products.

D.2.2 State where extracellular fluid can be located throughout the body.

-Blood plasma and lymph -Salive -Fluid in the eyes -Fluid secreted by glands and digestive tract -Fluid surrounding the nerves and spinal cord -Fluid secreted from skin and kidneys.

D.2.6 Describe how the hydration status of athletes can be monitored.

-Change in body weight (simplest). -Urine volume, osmolality, specific gravity, and color. -Changes in serum osmolality or serum sodium. -Body water stores using bioelectrical impedence.

D.2.7 Explain why endurance athletes require a greater water intake.

-Expands total body water volume delaying dehydration. -Maintain plasma volume, stroke volume, and cardiac output. -Prevent excessive rise in body core temperature. -Drinking too much fluid with too little sodium can lead to hyponatremia. -Concentration of sodium in body fluid is too low. -Plasma sodium concentration below 136-143 mmol. L-1. -Symptoms appear in stages: weakness, disorientation, seizures, coma, and death if not reversed.

D.2.4 Explain that homeostasis involves monitoring levels of variables and correcting changes in levels by negative feedback mechanisms.

-Homeostasis is where the body's internal environment remains relatively constant (with physiological limits) -Feedback system is cycle of events in which body condition is continually monitored. -Negative feedback initiates actions that reverse/reduce the stimulus. -Receptors detect change and send input to control center. -The control center evaluates input and issues output commands to an effector. -An effector produces a physiological response to return to controlled condition in normal state. -Nervous and hormonal systems work in harmony to achieve homeostasis.

D.2.8 Discuss the regulation of electrolyte balance during acute and chronic exercise.

-Prolonged exercise --> vascular system can be disturbed with a large volume of sweat/electrolyte loss. -Loss of plasma, increase in osmolarity which simulates secretion of electrolyte regulatory hormones. -ADH is regulated by kidneys. -Electrolytes in a fluid replaced during exercise greater than one hour. -Unless replacement contains sodium, urine ouput increase driving thirst. -Narrow concentration of electrolytes maintained within intracellular and extracellular compartments.

D.2.5 Explain the roles of the loop of Henlé, medulla, collecting duct and ADH in maintaining the water balance of the blood.

-When body fluids are low receptors n the hypothalamus are stimulated. -Hypothalamus stimulates pituitary gland releasing ADH. -ADH acts on kidneys. -Increases the water permeability of the renal tubules and collecting ducts. -Leads to increased re-absorption of water.

D.2.3 Compare water distribution in trained and untrained individuals.

Trained: -greater water content both intra and extracullularly. -improved temperature regulatory processes -lower sweat response -greate sweat produced -enlarges sweat glands -increase in blood volume Untrainted: -less lean muscle mass -greater percentage of body fat -less blood plasma volume -reduced sweat response