Water
WATER
Roles and regulation in the body
Introduction
• Water is a polar molecule (neutrally charged) • excellent universal solvent in the body; attracts charged particles into solutions
Introduction We all need water (vital for life and optimal health) o hot vs. cold, thirsty or not, sedentary or not o water needs vary according to physical activity levels, environment, etc • our bodies contain more water than other substance: ~ 60% of adult body weight is water, muscles 75% water, bones 20% water, blood 90% water, teeth 5% water • water is distributed into two compartments, 1) inside cells (intracellular), 2) outside cells (extracellular) [water between cells, blood, lymph, GIT spinal synovial eye fluids]; most of body water is found inside cells 3
Introduction Electrolytes: compounds that partly dissociate in water to form charged particles called ions Ions: electrically charged particles, e.g. Sodium (+ve charge; cation) or Chloride (-ve charge, anion) Buffers: compounds that can help to keep the acidity of a solution from changing by neutralising acids and bases (gather or release Hydrogen ions) • minerals (act as buffers) help to maintain acid-base balance when in solution • kidneys help to control the balance by excreting more or less acidic urine (dilute vs. concentrated) • lungs excrete more or less CO2 (in blood, carbonic acid)
Roles
Water provides the medium for transportation of nutrients and wastes body fluids (blood, lymph, interstitial fluid) carry substances within the body; water-based GIT secretions carry enzymes
Medium in which chemical reactions take place water is a critical solvent, many reactions can take place only if dissolved in water, dissociate into chemically charged ions .
Participate in biochemical reactions water is a reacting compound in hydrolysis reactions when CHOs, fat, protein are broken down into smaller units hydrolyses the bonds holding together
Lubricates and cushions solid materials when sliding against each other (body fluids) • saliva, tears, synovial; found in the mouth, GIT, eyes, joints
Regulates body temperature (thermoregulation) • human life is supported within narrow range of temperature 37°C; too low (28°C) muscle failure occurs & hypothermia sets in; too high (44°C) central nervous system fails, enzymes stop functioning, death occurs • water is good at storing heat, movement between compartments distribute heat, equalize body temperature; helps maintain temperature set point despite changes in surrounding environment • hypothalamus is the thermoregulatory center, has sensors in blood; temperature sensors in the skin
Cooling temperatures • muscle tissue surrounding blood vessels constrict, reduce blood flow & heat lost to the environment; hypothalamus sends signals to muscles to erect hairs, shiver and to endocrine glands [thyroid hormone] to increase metabolism Increased temperatures • muscle tissue surrounding blood vessels dilate, more blood flows to body’s periphery, extra heat is lost via perspiration (sweat) • water and electrolytes are lost in sweat; need to be replenished to maintain fluid-electrolyte balance • perspiration is a process that link temperature homeostasis with fluid and electrolyte homeostasis
8
Sources INTAKE (averages 2.5 litres, 2500 ml) Drinking water & beverages: club soda is 100% water, tea, coffee, diet drinks are 99% water, other drinks e.g. lemonade, milk, alcoholic beverages contain higher amounts of dissolved solids that displace water Water within foods: fruits, vegetables, certain dairy products have relatively high water content, whereas nuts, dried fruit, cereals have low water content Metabolic water: small amount is obtained during final stages of fat, protein, CHO metabolism (350ml)
Sources
Water does not need to be broken down into smaller units • minute amount is absorbed in the stomach • over 80% is absorbed in the small intestine; remainder goes to large intestine where it is reabsorbed
Sources Concerns on water intake (at risk: infants, elderly, athletes in long endurance events like marathon) • high solute levels due to concentrated milk formulas fed to infants without adequate water; must draw on own water stores to dilute the concentrated milk • coffee and alcoholic beverages are diuretics (increase the loss of body water through the urine), these are poor sources for meeting body fluid needs • eating salty foods calls for drinking extra fluid since you need water to excrete excess salt from the body • increased consumption of whole-grain products, fibrerich foods call for extra fluid intake because they absorb much water which leaves the body with solid waste (faeces)
Sources
OUTPUT • Majority excreted through the kidneys o more water ingested, more urine produced • Loss through sweat (physical activity, temp., humidity, clothing, etc) • Respiration through lungs • Excreted through intestinal fluids in the stool – depends on intake of dietary fibres, presence of diarrhea
Requirements • debate over the amount of water required to maintain health because there is no consistent scientific evidence proving that drinking a particular amount improves health or reduces risk of disease • amount of water/fluids a person should consume every day is variable, should be based on climate a person lives in, age, physical activity level and kidney function • a general guide is based on how much water is lost from the body (i.e. output) then intake is estimated
Sources Adverse effects of dehydration % Body weight loss and effects 0 Thirst 2 Stronger thirst, vague discomfort, loss of appetite, impaired physical performance 3 Decreased blood volume, reduced urinary output, dry mouth 4 Increased effort for physical work, impatience, sleepiness, nausea, emotional instability 5 Intense thirst 6 Impairment in exercise temperature regulation, increased pulse & respiratory rate 8 Dizziness, labored breathing with exercise, increased weakness, mental confusion 10Spastic muscles, inability to balance with eyes closed, delirium 11Inability of decreased blood volume to circulate normally, failing kidney function
Water regulation
• Water moves freely in and out of cells across semipermeable cell membrane according to electrolyte concentration on either side; moves toward the area of higher concentration and dilutes it to the same concentration as the other side (i.e. osmosis) • Electrolytes (Na, K, other minerals) regulate the balance of intracellular and extracellular water. K+ is found primarily inside cells, Na+ and Cl-outside cells
Water regulation
homeostatic control for water regulation • intake is prompted by sense of thirst (cells dehydrate, decrease in size) (↓ volume body fluids, ↑ concentration of dissolved substances in blood, dry mouth mucosa & pharynx) • Kidneys detect blood volume • Hypothalamus detects blood osmolality (number of solute particles per unit volume of solution) • Adrenal glands detect blood osmolality receptors in the brain (hypothalamus-pituitary gland) stimulate hormones which regulate water balance • Antidiuretic: kidney excrete less water more electrolytes • Aldosterone: kidneys reabsorb Na+ , excrete K+
Water regulation
• sodium-potassium ATPase exchange pump (present in all cells) against a concentration gradient, uses energy • renin-angiotensin-aldosteronesystem
Roles and regulation in the body
Introduction
• Water is a polar molecule (neutrally charged) • excellent universal solvent in the body; attracts charged particles into solutions
Introduction We all need water (vital for life and optimal health) o hot vs. cold, thirsty or not, sedentary or not o water needs vary according to physical activity levels, environment, etc • our bodies contain more water than other substance: ~ 60% of adult body weight is water, muscles 75% water, bones 20% water, blood 90% water, teeth 5% water • water is distributed into two compartments, 1) inside cells (intracellular), 2) outside cells (extracellular) [water between cells, blood, lymph, GIT spinal synovial eye fluids]; most of body water is found inside cells 3
Introduction Electrolytes: compounds that partly dissociate in water to form charged particles called ions Ions: electrically charged particles, e.g. Sodium (+ve charge; cation) or Chloride (-ve charge, anion) Buffers: compounds that can help to keep the acidity of a solution from changing by neutralising acids and bases (gather or release Hydrogen ions) • minerals (act as buffers) help to maintain acid-base balance when in solution • kidneys help to control the balance by excreting more or less acidic urine (dilute vs. concentrated) • lungs excrete more or less CO2 (in blood, carbonic acid)
Roles
Water provides the medium for transportation of nutrients and wastes body fluids (blood, lymph, interstitial fluid) carry substances within the body; water-based GIT secretions carry enzymes
Medium in which chemical reactions take place water is a critical solvent, many reactions can take place only if dissolved in water, dissociate into chemically charged ions .
Participate in biochemical reactions water is a reacting compound in hydrolysis reactions when CHOs, fat, protein are broken down into smaller units hydrolyses the bonds holding together
Lubricates and cushions solid materials when sliding against each other (body fluids) • saliva, tears, synovial; found in the mouth, GIT, eyes, joints
Regulates body temperature (thermoregulation) • human life is supported within narrow range of temperature 37°C; too low (28°C) muscle failure occurs & hypothermia sets in; too high (44°C) central nervous system fails, enzymes stop functioning, death occurs • water is good at storing heat, movement between compartments distribute heat, equalize body temperature; helps maintain temperature set point despite changes in surrounding environment • hypothalamus is the thermoregulatory center, has sensors in blood; temperature sensors in the skin
Cooling temperatures • muscle tissue surrounding blood vessels constrict, reduce blood flow & heat lost to the environment; hypothalamus sends signals to muscles to erect hairs, shiver and to endocrine glands [thyroid hormone] to increase metabolism Increased temperatures • muscle tissue surrounding blood vessels dilate, more blood flows to body’s periphery, extra heat is lost via perspiration (sweat) • water and electrolytes are lost in sweat; need to be replenished to maintain fluid-electrolyte balance • perspiration is a process that link temperature homeostasis with fluid and electrolyte homeostasis
8
Sources INTAKE (averages 2.5 litres, 2500 ml) Drinking water & beverages: club soda is 100% water, tea, coffee, diet drinks are 99% water, other drinks e.g. lemonade, milk, alcoholic beverages contain higher amounts of dissolved solids that displace water Water within foods: fruits, vegetables, certain dairy products have relatively high water content, whereas nuts, dried fruit, cereals have low water content Metabolic water: small amount is obtained during final stages of fat, protein, CHO metabolism (350ml)
Sources
Water does not need to be broken down into smaller units • minute amount is absorbed in the stomach • over 80% is absorbed in the small intestine; remainder goes to large intestine where it is reabsorbed
Sources Concerns on water intake (at risk: infants, elderly, athletes in long endurance events like marathon) • high solute levels due to concentrated milk formulas fed to infants without adequate water; must draw on own water stores to dilute the concentrated milk • coffee and alcoholic beverages are diuretics (increase the loss of body water through the urine), these are poor sources for meeting body fluid needs • eating salty foods calls for drinking extra fluid since you need water to excrete excess salt from the body • increased consumption of whole-grain products, fibrerich foods call for extra fluid intake because they absorb much water which leaves the body with solid waste (faeces)
Sources
OUTPUT • Majority excreted through the kidneys o more water ingested, more urine produced • Loss through sweat (physical activity, temp., humidity, clothing, etc) • Respiration through lungs • Excreted through intestinal fluids in the stool – depends on intake of dietary fibres, presence of diarrhea
Requirements • debate over the amount of water required to maintain health because there is no consistent scientific evidence proving that drinking a particular amount improves health or reduces risk of disease • amount of water/fluids a person should consume every day is variable, should be based on climate a person lives in, age, physical activity level and kidney function • a general guide is based on how much water is lost from the body (i.e. output) then intake is estimated
Sources Adverse effects of dehydration % Body weight loss and effects 0 Thirst 2 Stronger thirst, vague discomfort, loss of appetite, impaired physical performance 3 Decreased blood volume, reduced urinary output, dry mouth 4 Increased effort for physical work, impatience, sleepiness, nausea, emotional instability 5 Intense thirst 6 Impairment in exercise temperature regulation, increased pulse & respiratory rate 8 Dizziness, labored breathing with exercise, increased weakness, mental confusion 10Spastic muscles, inability to balance with eyes closed, delirium 11Inability of decreased blood volume to circulate normally, failing kidney function
Water regulation
• Water moves freely in and out of cells across semipermeable cell membrane according to electrolyte concentration on either side; moves toward the area of higher concentration and dilutes it to the same concentration as the other side (i.e. osmosis) • Electrolytes (Na, K, other minerals) regulate the balance of intracellular and extracellular water. K+ is found primarily inside cells, Na+ and Cl-outside cells
Water regulation
homeostatic control for water regulation • intake is prompted by sense of thirst (cells dehydrate, decrease in size) (↓ volume body fluids, ↑ concentration of dissolved substances in blood, dry mouth mucosa & pharynx) • Kidneys detect blood volume • Hypothalamus detects blood osmolality (number of solute particles per unit volume of solution) • Adrenal glands detect blood osmolality receptors in the brain (hypothalamus-pituitary gland) stimulate hormones which regulate water balance • Antidiuretic: kidney excrete less water more electrolytes • Aldosterone: kidneys reabsorb Na+ , excrete K+
Water regulation
• sodium-potassium ATPase exchange pump (present in all cells) against a concentration gradient, uses energy • renin-angiotensin-aldosteronesystem
No comments: