Transcript Chapter 9: Nutrients Involved in Fluid and Electrolyte Balance

Chapter 9 Lecture
Chapter 9:
Nutrients Involved
in Fluid and
Electrolyte
Balance
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Body Fluids
• Body fluid is the liquid portion of cells and
tissues
• Characterized by its ability to move freely and
changeably, adapting to the shape of the
container that holds it
• About 50–70% of healthy adult body weight
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Body Fluids
• Intracelluar fluid: within the cell
• 2/3 of body fluid
• Extracellular fluid: outside the cell
• 1/3 of body fluid
• Interstitial fluid flows between cells that
make up a particular tissue or organ (muscle,
liver)
• Intravascular fluid is the water in the blood
and lymph
• Plasma transports blood cells within arteries,
veins, and capillaries
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© 2017 Pearson Education, Inc.
Body Fluids
• Fluid composition of tissue varies by:
• Tissue type: lean tissues have higher fluid
content than fat tissues
• Gender: males have more lean tissue and
therefore more body fluid than females
• Age: decrease in body water results partly
from loss of lean tissue as people age
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Electrolytes
• Electrolytes are dissolved substances that
disassociate in solution into electrically charged
particles called ions
• Positive charge (cations): sodium, potassium
• Negative charge (anions): chloride,
phosphorus
• Predominant electrolytes
• Extracellular fluid: sodium, chloride
• Intracellular fluid: potassium, phosphorus
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Functions of Body Fluids
• Fluids dissolve and transport substances
• Water is an excellent solvent because it
dissolves a variety of substances
• Water-soluble substances are readily
transported in the bloodstream: amino acids,
glucose, water-soluble vitamins, minerals,
some medications
• Fatty substances must be attached to or
surrounded by water-soluble proteins
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Functions of Body Fluids
• Fluids account for blood volume
• Appropriate body fluid levels are essential for
maintaining healthful blood volume
• Blood pressure increases when blood volume
rises
• High blood pressure (hypertension) is a risk
factor for heart disease and stroke
• Low blood pressure can cause people to feel
tired, confused, or dizzy
• Kidneys help to regulate blood volume and
blood pressure
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Functions of Body Fluids
• Fluids account for blood volume
• Antidiuretic hormone (ADH) released from
the pituitary gland stimulates the kidneys to
reabsorb water, reducing urine output
• Enzyme renin secreted from the kidneys
responds to decreased blood pressure;
catalyzes the conversion of blood protein
angiotensinogen to angiotensinogen I
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Functions of Body Fluids
• Fluids account for blood volume
• Angiotensin I is converted to Angiotensin II
(vasoconstrictor); increases blood pressure
• Hormone aldosterone secreted from the
adrenal glands signals the kidneys to retain
sodium and chloride, thereby retaining water,
increasing blood pressure, and decreasing
urine output
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© 2017 Pearson Education, Inc.
Functions of Body Fluids
• Fluids help maintain body temperature
• Fluids maintain body temperature within a
safe range
• Water has a high capacity for heat, which
means that only sustained high heat can
increase body temperature
• Sweating releases heat as the evaporation of
water from the skin cools the skin and blood
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© 2017 Pearson Education, Inc.
Functions of Body Fluids
• Protect and lubricate tissues
• Cerebrospinal fluid protects the brain and
spinal cord
• Amniotic fluid protects the fetus
• Synovial fluid lubricates joints
• Tears cleanse and lubricate eyes
• Saliva moistens food for swallowing
• Pleural fluid allows lungs to expand and
retract without friction
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Functions of Electrolytes
• Electrolytes help regulate fluid balance
• Cell membranes are permeable to water, but
not freely permeable to electrolytes
• Water moves by osmosis to areas where the
concentration of solute is high
• This action provides a means to control
movement of water into and out of the cells
• Osmotic pressure keeps electrolytes in
solution from drawing liquid toward them
across a semipermeable membrane
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© 2017 Pearson Education, Inc.
Functions of Electrolytes
• Electrolytes enable nerves to respond to
stimuli
• Nerve impulses are initiated at nerve cell
membranes in response to a change in
electrical charge across the membrane
• Depolarization—Action Potential—
Repolarization
• Sodium and potassium ensure that nerve
impulses are generated, transmitted, and
completed
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© 2017 Pearson Education, Inc.
Functions of Electrolytes
• Electrolytes signal muscles to contract
• Muscles are stimulated to contract in
response to stimulation of nerve cells
• Increased flow of calcium ions from its
storage site into the muscle stimulates
muscle contraction
• Muscles can relax after contraction once the
electrical signal is complete and calcium is
pumped out of the muscle cell
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Fluid Balance
• Fluids gained through consumption and
metabolism
• As much as 90% of fluids needs met by
beverages and food
• Metabolic water formed from metabolic
reactions contributes 10–14% of the water
the body needs each day
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Fluid Balance
• Thirst mechanism (hypothalamus) prompts us
to drink. It is stimulated by:
• Increased concentration of salt and other
dissolved substances in the blood
• A reduction in blood volume and blood
pressure, such as during profuse sweating,
vomiting, diarrhea, or low fluid intake
• Dry mouth and throat from reduced saliva
• ADH signals the kidneys to retain water
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© 2017 Pearson Education, Inc.
Fluid Balance
• Sensible fluid loss
• Kidneys excrete water as urine
• Sweat during exercise or in hot environment
• Insensible fluid loss
• Skin (not sweating) or lungs during exhalation
• Significant loss
• Illness, traumatic injury, blood donation,
surgery, exercise, high altitude, low humidity,
pregnancy, breastfeeding, diuretics
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How Much Water Should We Drink?
• Requirements are individualized
• Amount needed varies with age, body size,
health status, physical activity level,
environment
• Athletes, highly active people, and people
working in hot environments may need
additional fluid to replace fluid lost in sweat
• Sources of drinking water: tap, carbonated,
mineral, bottled
• Distilled and purified water not suitable for
drinking
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© 2017 Pearson Education, Inc.
Minerals Contribute to Fluid Balance
• Major extracellular cation
• Functions of sodium:
• Allows cells to maintain fluid balance
• Blood pressure regulation
• Transmission of nerve signals
• Muscle contraction and relaxation
• Assists in glucose absorption from the small
intestine
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Sodium
• How much sodium?
• AI: 1.5 g/d; other health groups recommend
no more than 2.3 or 2.4 mg/d
• Found naturally in many foods, processed
and restaurant foods are high in sodium
• High sodium diets associated with high blood
pressure
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Sodium (cont.)
• What if you consume too much sodium?
• Hypernatremia is abnormally high blood
sodium concentration
• Patients with congestive heart failure or
kidney disease cannot effectively excrete
sodium
• Causes high blood volume, edema (swelling),
and high blood pressure
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Sodium (cont.)
• What if you don't consume enough sodium?
• Hyponatremia is abnormally low blood
sodium level
• From prolonged sweating, vomiting, diarrhea
• Symptoms: headaches, dizziness, fatigue,
nausea, vomiting, and muscle cramps
• If untreated: seizures, coma, and death
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Potassium
• Major intracellular cation
• Together with sodium, maintains fluid
balance, regulates transmission of nerve
impulses, and muscle contraction
• High potassium intake helps maintain a lower
blood pressure
• How much potassium?
• Recommended intake is 4.7 g/day
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Potassium (cont.)
• Sources of potassium
• Good sources include: fresh fruits,
vegetables, legumes, and whole grains
• Processing foods increases sodium and
decreases potassium content
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© 2017 Pearson Education, Inc.
Potassium (cont.)
• What happens if you consume too much
potassium?
• Hyperkalemia: high blood potassium levels
• Can alter normal heart rhythm, resulting in
heart attack and death
• People with kidney disease are unable to
regulate their blood potassium levels and
should avoid consuming potassiumcontaining salt substitutes
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Potassium (cont.)
• What happens if you don't consume enough
potassium?
• Hypokalemia: low blood potassium levels
• Seen in people with kidney disease or
diabetic ketoacidosis
• Can occur when taking certain diuretics and
with extreme dehydration, vomiting, diarrhea,
alcohol abuse, long-term consumption of
natural licorice (glycyrrhizic acid or GZA), or
eating disorder (abnormal heart rhythms)
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Chloride
• Major extracellular anion
• Functions of chloride
• Assists with fluid balance
• Aids digestion: hydrochloric acid (HCl) in the
stomach
• Assists the immune system
• Transmission of nerve impulses
• Recommended intake
• AI: 2.3 g/day
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Chloride (cont.)
• What happens if you consume too much
chloride?
• Primary dietary source: table salt
• Hypertension in salt-sensitive individuals
• What happens if you don't consume enough
chloride?
• This is rare but can occur in people with
severe dehydration, frequent vomiting, and
eating disorders
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Phosphorus (cont.)
• Major intracellular anion
• Functions of phosphorus:
• Fluid balance maintenance
• Critical role in bone formation
• Regulates biochemical reactions by activating
or deactivating enzymes (phosphorylation)
• Found in ATP, DNA, RNA, cell membranes
(phospholipids), and lipoproteins
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Phosphorus (cont.)
• Recommended intake
• RDA for phosphorus is 700 mg/day
• Sources of phosphorus
• Widespread in many foods
• High in protein foods (meat, milk, eggs)
• More readily absorbed from animal sources
• Phytic acid: plant storage form (beans,
whole grains, nuts)
• Soft drinks
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© 2017 Pearson Education, Inc.
Phosphorus (cont.)
• What happens if you consume too much
phosphorus?
• High blood phosphorus can occur among
people with kidney disease or when taking
too many vitamin D supplements
• Causes muscle spasms, convulsions
• What if you don't consume enough phosphorus?
• Deficiencies of phosphorus are rare
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Disorders Related To Fluid And Electrolyte
Imbalance
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Dehydration
Heat stroke
Water intoxication
Hypertension
Neuromuscular disorders
Kidney disorders
Congestive heart failure
Obesity
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© 2017 Pearson Education, Inc.
Dehydration
• Dehydration occurs when fluid loss exceeds
fluid intake
• Commonly due to heavy exercise or high
environmental temperatures
• Elderly and infants are at increased risk
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© 2017 Pearson Education, Inc.
Heat Stroke
• Heat stroke occurs from failure in the body's
heat-regulating mechanisms
• Hot, humid environments
• Symptoms: rapid pulse, hot and dry skin, high
body temperature, loss of consciousness
• Fatal during exercise in extreme heat
• Stop exercising when feeling dizzy, lightheaded, disoriented, or nauseated
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Water Intoxication
• Overhydration (water intoxication) can occur,
but it is rare
• Kidneys retain too much water, causing
overhydration and hyponatremia
• Documented cases of deaths among college
students (hazing rituals)
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Hypertension
• Hypertension: major chronic disease
characterized by high blood pressure
• Often without symptoms
• Increases a person's risk of heart disease,
stroke, kidney disease
• Can reduce brain function, impair physical
mobility, and cause death
• Systolic pressure over 140 mm Hg
• Diastolic pressure over 90 mm Hg
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Hypertension (cont.)
• What causes hypertension?
• Primary (or essential) hypertension: unknown
cause for 90–95% of cases
• 5–10% of cases are caused by kidney
disease, sleep apnea, and chronic alcohol
abuse
• Salt sensitivity: about 2/3 adults with
hypertension
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Hypertension (cont.)
• Recommendations for reducing hypertension:
• Losing weight
• Regular exercise
• Limiting alcohol intake
• Reducing sodium intake
• Eating more whole grains, fruits, vegetables,
and low-fat dairy foods
• DASH diet
• Avoid tobacco products
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© 2017 Pearson Education, Inc.
Hypertension (cont.)
• Medications
• Help in normalizing blood pressure
• Should also continue to practice healthful
lifestyle changes
• Hypertension: "the silent killer"
• Often no obvious symptoms of this disease
• Importance of regular blood pressure check
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Neuromuscular Disorders
• Electrolyte imbalances can alter nervous system
and muscle function
• Seizures: uncontrollable muscle spasms
• Muscle cramps: involuntary, spasmodic, and
painful muscle contractions
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Kidney and Heart-Related Disorders
• Kidney disorders
• Kidneys have major role in regulation of fluid,
electrolyte, and acid-base balance
• Kidney disease can lead to edema and fluid
retention
• Congestive heart failure
• Heart can no longer pump adequate supply of
blood throughout the body
• Heart can fail on the left or right sides, with
varying consequences
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Obesity
• Popularity of sweetened beverages (U.S.)
• 20% of calories from beverages: sweetened
soft drinks, fruit juices, sweetened bottled
waters, energy drinkds, bottled teas, specialty
coffee
• Appetite not curbed: extra calories from
drinks are not compensated for by eating less
• Displace more nutritious beverages such as
milk (source of protein, calcium, vitamin D,
and other nutrients important for bone health)
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