Ch. 3 fluid and electrolytes

What percentage of an infant's body is water?

Approximately 77%

What percentage of an older adult's body is water?

About 45%.

Do women have more or less water in their bodies compared to men?

Less water.

Which groups are more likely to experience severe consequences from minor changes in fluid balance?

The older adult and the very young.

Why does fatty tissue contain less water than other tissues?

Fatty tissue does not hold as much water as other tissues.

How does body fat affect the percentage of body water?

The greater the amount of fat in the body, the lower the percentage of body water.

Why is maintaining a healthy weight important for fluid regulation?

It helps regulate the body's percentage of water.

Why is keeping body fluids within a normal range necessary?

Life processes for every cell of every organ take place within fluid.

What are nutrients needed for life and reproduction suspended in?

Water

What is the largest part of each cell composed of?

Fluid

What must continuously exchange for life processes to occur in cells?

Water, glucose, oxygen, nutrients, electrolytes, and waste products.

What is one main function of water in the body

To be a vehicle for the transportation of substances to and from the cells.

How does water assist in maintaining hydrogen balance in the body

It plays a role in maintaining hydrogen balance.

What role does water serve in digestion

It acts as a medium for the enzymatic action of digestion.

What are the two main compartments of body fluids?

Intracellular and extracellular

How is the body's fluid excreted?

Mainly through the kidney

What is the movement of body fluids?

Body fluids are continually in motion, moving in and out of the blood and lymph vessels, through the spaces surrounding the cells, and through the bodies of the cells themselves.

What do osmoreceptors in the hypothalamus sense?

The internal environment, specifically the ratio of fluid to solutes.

What mechanism do osmoreceptors promote when fluid intake is needed?

The thirst mechanism.

Where are baroreceptors located that detect pressure changes?

In the carotid sinus and aortic arch.

What do baroreceptors stimulate in response to blood volume changes?

The sympathetic or parasympathetic nervous system.

What hormone is released by the posterior pituitary to control fluid loss in urine?

Antidiuretic hormone (ADH).

What is the role of aldosterone in fluid balance?

It regulates the reabsorption of water and sodium ions from the kidney tubules.

What do brain natriuretic peptide (BNP) and atrial natriuretic peptide (ANP) promote?

Loss of water and sodium ions from the kidney tubules and cause vasodilation.

What triggers the release of ADH?

Decreased or increased concentration of the blood.

What causes the adrenal cortex to release aldosterone?

Low ECF volume or decreased sodium concentration.

What system regulates the release of aldosterone?

The renin-angiotensin-aldosterone system.

When is renin released?

When there is decreased blood flow to the kidney.

What do baroreceptors in the atrium of the heart detect?

Fluid overload.

What hormone is released by the myocardium in response to fluid overload?

ANP (Atrial Natriuretic Peptide).

What is the function of ANP?

To increase sodium excretion and protect the body from fluid overload.

What is released when the ventricles are stretched with volume?

BNP (B-type Natriuretic Peptide).

Which is a stronger diuretic, ANP or BNP?

BNP.

What processes allow movement of fluids and solutes across cell membranes?

Several processes including diffusion and osmosis.

How is fluid balance primarily assessed?

Through monitoring the intravascular space and external signs and symptoms.

What is used to monitor total body water?

Weight.

Why are intracellular, interstitial, and transcellular fluids not accessible for testing?

They cannot be easily measured or tested directly.

What are some examples of nonelectrolyte solutes?

Protein, urea, glucose, creatinine, and bilirubin.

What does osmolality measure?

The concentration of a solution determined by the number of solutes in it.

What is the role of osmolality in the body?

It controls water movement and extracellular compartments.

Which ion maintains the osmolality of the intracellular fluid (ICF)?

Potassium.

Which ion controls the osmolality of the extracellular fluid (ECF)?

Sodium.

What is the normal osmolality range of body fluids?

280 to 294 milliosmoles per kilogram.

What is diffusion?

Diffusion is the process by which substances move across the membrane until they are evenly distributed in the available space.

How does fluid move in capillaries?

Fluid moves into and out of the capillaries by filtering through the permeable capillary wall or cell membrane walls.

What happens when there is a concentration difference across a membrane?

Particles in the concentrated solution travel through the membrane to the less concentrated side to equalize the concentration.

What is the driving force behind diffusion?

Diffusion is possible because of kinetic motion, which causes molecules to mix and stir body fluids.

What is meant by movement down a concentration gradient?

Substances move from a high to a low concentration until the concentration on both sides of the membrane is equal.

Which substances commonly move by diffusion?

Glucose, oxygen, carbon dioxide, water, and other small ions and molecules move by diffusion.

What is an electrical gradient?

An electrical gradient is created by the attraction between particles of opposite charge and the repellent action between particles of like charge.

How do intracellular proteins affect ion movement?

Many intracellular proteins have a negative charge that attracts positively charged sodium and potassium ions from the extracellular fluid (ECF).

What is osmosis?

Osmosis is the movement of pure solvent (liquid) across a membrane.

How does water move by osmosis?

Water moves from an area of lesser concentration of solutes to an area of greater concentration until the solutions are of equal concentration.

What type of membrane allows some substances to pass through but prevents others?

A semipermeable membrane.

What is osmotic pressure?

Osmotic pressure is what holds fluid in the vascular space.

What happens to cells in a hypertonic solution?

The water in the cells will move to the more concentrated solution, causing the cells to dehydrate and shrink.

What is a hypotonic solution in relation to cells?

A hypotonic solution has less solute concentration than the cells.

What happens to cells in a hypotonic solution?

The cells swell from the extra fluid (overhydrate).

How are IV fluid solutions classified?

Solutions are classified as isotonic, hypertonic, or hypotonic according to their concentration of electrolytes and other solutes.

What is filtration?

Filtration is the movement of water and solutes through a semipermeable membrane as a result of a pushing force on one side of the membrane.

Where does filtration occur in the body?

Filtration occurs in the kidney.

What substances are eliminated through kidney filtration?

Waste substances and excess water are eliminated.

What creates hydrostatic pressure in the capillaries?

The pumping action of the heart creates hydrostatic pressure.

What is hydrostatic pressure?

Hydrostatic pressure is the pressure exerted by fluid within the capillaries.

What happens to water and electrolytes during filtration?

Water and electrolytes move through the capillary wall to the interstitial fluid.

What do nephrons do with the filtered fluid?

Nephrons pick up the fluid to form urine for excretion.

What role does the lymph system play in filtration?

The lymph system filters bacteria from lymph fluid.

What does the spleen filter from the blood?

The spleen filters the blood of old red cells.

What is active transport?

Active transport is a process that requires cellular energy to move molecules into cells against their concentration gradient.

What energy source is used in active transport?

The energy source for active transport is adenosine triphosphate (ATP).

How does active transport differ from diffusion and osmosis?

Active transport can move substances from an area of lower concentration to an area of higher concentration, unlike diffusion and osmosis.

What types of substances are moved by active transport?

Active transport moves amino acids, glucose, iron, hydrogen, sodium, potassium, and calcium through the cell membrane.

What is the sodium pump?

The sodium pump is the mechanism by which sodium and potassium are moved into or out of the cell via active transport.

What metabolic processes produce ATP in the body's cells?

ATP is produced during complex metabolic processes that metabolize carbon chains of sugars, fatty acids, and amino acids.

How do healthy people maintain fluid balance?

By drinking sufficient fluids and eating a balanced diet each day.

What percentage of water can solid foods contain?

Up to 85% water.

How is water produced in the body?

As a by-product of metabolism.

What role do healthy kidneys play in fluid balance?

They balance the amount of substances entering and leaving the blood.

How can illness affect fluid balance?

It may prevent ingestion of food or liquids, affect absorption, or impair kidney function.

What is the impact of diseases affecting circulation on fluid balance?

They affect the distribution and composition of body fluids.

What can cause extra fluid loss in the body?

An accelerated metabolic rate due to fever, thyroid crisis, burns, severe trauma, or extreme stress.

How much fluid can perspiration account for in an adult?

Up to 2 L/hr.

What is the insensible water loss associated with each degree of fever on the Celsius scale?

10%.

What are examples of insensible losses?

Perspiration and water lost in respiration.

How does hot and dry weather affect water loss from the body?

It increases water loss.

Who is at greater risk for fluid and electrolyte imbalance?

Seriously ill patients.

What are some reasons patients may be at risk for deficient fluid volume?

Patients may be at risk due to impaired swallowing, extreme weakness, disorientation or coma, unavailability of water, or excessive fluid loss from vomiting, diarrhea, hemorrhage, diaphoresis, excessive wound drainage, or diuretic therapy.

What happens to water in the body when a fluid deficit occurs?

Water moves from the cells into the interstitial and intravascular spaces, causing dehydration of the cells.

How is dehydration treated?

Dehydration is treated by administering fluid orally, intravenously, or through feeding or gastrectomy tubes.

What should be done for patients unable to take in fluids or food for an extended period?

A feeding tube must be placed or total parenteral nutrition (TPN) started.

What is one method to check for dehydration in patients?

Turgor is checked by gently pinching up the skin over areas like the abdomen, forearm, or thigh.

What indicates a fluid deficit when checking skin turgor?

If a fluid deficit is present, the pinched skin may remain elevated or tented for several seconds.

Why is skin turgor not a valid indicator of fluid status in older adults?

Older adults often have inelastic skin that routinely tents when pinched, making it an unreliable measure.

How is dehydration evident in infants?

Dehydration in infants is evident by sunken fontanels.

What is a fluid imbalance?

A fluid imbalance exists when there is an excess (too much) or a deficit (too little) of water in the body.

What happens to substances dissolved in body water during a fluid imbalance?

There will be an accompanying imbalance in the substances dissolved in body water.

How does water move in relation to sodium in the body?

Water follows sodium in the body through osmosis.

What causes an osmotic pull in the body?

The sodium concentration causes an osmotic pull.

Where does water go in relation to sodium concentration?

Water will go to where the sodium concentration is highest.

What is a common problem in older adults related to hydration?

Fluid volume deficit