Week 6: Body Water Balance and Hydration Flashcards
How much of our body is made up of water?
60-70%
What is our typical survival time without drinking water?
100 hours
What is the typical rate of sweat during exercise per hour?
1-2 litres per hour
What does total body water include?
Fluid that occupies intra-cellular and extra-cellular space roughly equals 60% of body mass
What does intra-cellular fluid volume include?
Fluid within tissue cells roughly equals 40% of body mass
Which enzyme electrolyte has the greatest concentration in plasma?
Sodium
Name the two main hormones that help regulate plasma osmolatity
Antidiuretic hormone
Aldosterone
What plasma osmolality reading is classified as euhydration?
285-290 mOsmol per kg
What are the organic substances that make up body fluids?
Glucose Amino acids Fatty acids Hormones Enzymes
What are the inorganic substances that make up body fluids?
Sodium Potassium Calcium Magnesium Chloride Phosphate Sulphate
What effect the distribution of body water?
The relative concentration of the solutes within the blood
What is body water balance?
When the volume of water intake is equal to the volume that is lost
How do we intake water?
Food
Fluids
Metabolism
How is water lost?
Urine
Faeces
Skin
Lungs
What is total body water (TBW)?
Fluid that occupies intra-cellular and extra spaces
What is intra cellular fluid volume (ICFV)?
Fluid within tissue cells
What is extra cellular volume (ECV)?
All fluids outside of cells
What is interstitial fluid volume (IFV)?
Located spaces between tissue cells
What is plasma volume (PV)?
Liquid portion of blood
What separates the intracellular fluid and the interstitial fluid?
Plasma membrane
What type of membrane is the plasma membrane?
Semi-permeable
What separates the interstitial fluid and the plasma?
The vascular wall
What type of membrane is the vascular wall?
Semi-permeable
How does water travel across the semi-permeable membrane?
Via osmosis
What happens in euhydration?
Normal body water level
The osmolarity of the intracellular and extracellular fluids are the same
What happens in hypohydration?
The fluid around the cell has a higher solute concentration, causing water to diffuse out of the cell
What happens in hyperhydration?
The fluid around the cell has a lower solute concentration therefore water diffuses into the cell
What are the four general functions of electrolytes?
Control osmosis between body fluid compartments
Help maintain the acid-base balance
Carry electrical current
Serve as cofactors
What is the most abundant ion in the extracellular fluid?
Sodium
What does sodium help control?
Our body water status
What is fluid balance critical for?
Metabolic, cardiac and thermoregulatory funciton
How is fluid balance controlled?
The endocrine system
What are the two primary hormones that regulate water balance?
Antidiuretic hormone (ADH)/ arginine vasopressin Aldosterone
Where is the antidiuretic hormone (ADH) released?
The posterior pituitary glands
What stimulates secretion of antidiuetic hormone?
Haemoconcentraction (too much salt)
Increase in plasma osmolality
Decrease in plasma volume
What does antidiuretic hormone (ADH) do and why?
Promotes water retention in the kidney in an effect to dilute plasma electrolyte concentration back to normal
Where is aldosterone released from?
The adrenal cortex
What stimulates aldosterone secretion?
Decrease in plasma sodium
Decrease in blood volume
Decrease in pressure
Increase in plasma potassium concentration
What type of hormone is aldosterone?
A mineralcorticoid hormone
What does aldosterone do and why?
Promotes renal reabsorption of sodium causing increased fluid retention
When is atrial natriuretic peptide (ANP) released?
Atrial distension
Endothelin
Sympathetic stimulation
What does atrial natriuretic peptide (ANP) do?
Reduces blood pressure
Reduces blood volume
Causes vasodilation
Which electrolyte has the greatest conc in plasma?
Sodium
Name the two main hormones that help regulate plasma osmolality?
Antidiuretic hormone
Aldosterone
What plasma osmolality reading is classified as euhydrated, including units?
295 mOsmol/kg
What are the cellular consequences of dehydration?
Loss of solutes/reduced blood volume
Causes change in osmotic pressure
Cells lose water and shrink due to osmosis
How does sweating effect blood volume and therefore plasma volume?
Decreases blood volume due to a decreased plasma volume
What are the cardiovascular consequences of dehydration?
Decreased stroke volume
Decreased cardiac output (less blood pumped)
Decreased blood pressure (less muscle blood flow)
Why do we become dehydrated during exercise?
Sweating
Why does dehydration impair endurance exercise performance?
Decreased: Plasma volume Blood volume End diastolic volume Stroke volume Cardiac output Vo2 max Increased anaerobic metabolism
Why does dehydration impair game performance?
Endurance performance impairments plus motor and cognitive impairments
