Fluids, Electrolytes, and pH

What percentage of an infant's body mass is water?

About 75%.

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

About 50-60%.

What percentage of an elderly person's body mass is water?

About 45%.

Which organs have the highest proportion of water?

The brain and kidneys.

Which body structure has the lowest proportion of water?

The teeth.

Approximately how much water can the brain contain?

About 85%.

Approximately how much water do teeth contain?

About 8%.

What are the two main fluid compartments of the body?

Intracellular fluid and extracellular fluid.

What is intracellular fluid (ICF)?

Fluid found inside the body's cells.

What is extracellular fluid (ECF)?

Fluid found outside the body's cells.

What acts as the barrier between ICF and ECF?

The plasma membrane.

What are the two main components of extracellular fluid?

Plasma and interstitial fluid.

What is plasma?

The fluid portion of blood.

What is interstitial fluid?

Fluid that surrounds body cells outside the blood vessels.

What are examples of other extracellular fluids?

Cerebrospinal fluid, synovial fluid, and pleural, pericardial, and peritoneal fluid.

Which fluid compartment contains the most body water?

Intracellular fluid.

What is the main difference between ICF and ECF?

ICF is inside cells; ECF is outside cells.

How do materials travel between blood plasma and body cells?

Through the interstitial fluid between capillaries and cells.

What is a solute?

A substance dissolved in a liquid.

What is an electrolyte?

A substance that forms ions when dissolved in water.

What is a non-electrolyte?

A dissolved substance that does not separate into ions.

Give examples of non-electrolytes.

Glucose, lipids, creatine, and urea.

Which has greater osmotic power: electrolytes or non-electrolytes?

Electrolytes.

What causes water to move between fluid compartments?

Osmotic gradients.

Which two ions are mainly concentrated in ECF?

Sodium and chloride.

Which major ion is mainly concentrated in ICF?

Potassium.

What maintains the different sodium and potassium concentrations?

The sodium-potassium pump.

What does the sodium-potassium pump do?

Uses ATP to move sodium out of cells and potassium into cells.

How many sodium ions move out during one sodium-potassium pump cycle?

Three sodium ions.

How many potassium ions move into the cell during one sodium-potassium pump cycle?

Two potassium ions.

What is hydrostatic pressure?

The force exerted by fluid against a wall.

What is blood hydrostatic pressure?

The pressure of blood against blood vessel walls caused by the pumping heart.

What does hydrostatic pressure cause?

Movement of fluid between body compartments.

What is colloid osmotic pressure?

The pulling force created by proteins in blood that helps draw water into capillaries.

What happens at the arterial end of a capillary?

Hydrostatic pressure pushes fluid and nutrients out into surrounding tissues.

Why does fluid leave capillaries at the arterial end?

Capillary hydrostatic pressure is greater than blood colloid osmotic pressure.

What happens near the middle of a capillary?

There is approximately no net fluid movement when the opposing pressures are equal.

What happens at the venous end of a capillary?

Fluid and cellular wastes move from surrounding tissues back into capillaries.

Why does fluid return to capillaries at the venous end?

Blood colloid osmotic pressure is greater than capillary hydrostatic pressure.

What happens to excess interstitial fluid that does not return to capillaries?

The lymphatic system drains it and returns it to the bloodstream.

Where does lymphatic fluid eventually reenter the blood circulation?

At the subclavian veins.

How does increased hydrostatic pressure affect kidney filtration?

More water leaves the capillaries, producing more urine filtrate.

How does decreased hydrostatic pressure affect kidney filtration?

Less water leaves the capillaries, producing less urine filtrate.

How can severe dehydration affect the kidneys?

It can impair kidney function and may lead to kidney failure.

What is active solute transport?

Movement of substances using energy, often against a concentration gradient.

What is passive solute transport?

Movement of substances down a concentration gradient without using energy.

What direction does passive transport move substances?

From higher concentration to lower concentration.

What is an example of active transport?

The sodium-potassium pump.

Which substances move easily through the cell membrane?

Gases, lipids, and water.

What are aquaporins?

Protein channels that allow water to move through cell membranes.

Which substances commonly require facilitated transport?

Glucose, amino acids, and ions.

Does facilitated transport require energy?

No. It moves substances down their concentration gradient through membrane proteins.

What is facilitated diffusion?

Passive movement through specific membrane transport proteins.

What is edema?

Accumulation of excess fluid in body tissues.

What causes edema?

Excess fluid leaks from capillaries or is not adequately removed from tissues.

What are possible causes of edema?

Medical conditions, medications, pregnancy, injury, and allergic reactions.

Where is edema commonly found?

The lower extremities, such as the legs and feet.

What is pitting edema?

Swelling that leaves an indentation after pressing on the affected area.

What is non-pitting edema?

Swelling that does not leave an indentation when pressed.

What is pulmonary edema?

Accumulation of excess fluid in the air sacs of the lungs.

What conditions commonly cause pulmonary edema according to the slides?

Heart disease and kidney disease.

What is plasma osmolality?

The ratio of dissolved solutes to water in blood plasma.

What does plasma osmolality help indicate?

The body's hydration status.

What happens when blood osmolality increases?

The blood becomes more concentrated, stimulating thirst and ADH release.

Which part of the brain monitors blood osmolality?

The hypothalamus.

What are osmoreceptors?

Sensory receptors that detect changes in the concentration of solutes in blood.

What happens when osmoreceptors detect increased blood osmolality?

The hypothalamus increases thirst and stimulates ADH release.

What is antidiuretic hormone (ADH)?

A hormone that helps the kidneys conserve water.

Where is ADH produced?

The hypothalamus.

Where is ADH stored and released?

The posterior pituitary gland.

What is the main purpose of ADH?

To increase water reabsorption by the kidneys and reduce water loss in urine.

What happens to thirst when blood osmolality increases?

Thirst increases, encouraging water intake.

How does the hypothalamus affect saliva during dehydration?

It signals the salivary glands to decrease water secretion, causing dry mouth.

What happens to blood volume when the body loses too much water?

Blood volume decreases.

What are baroreceptors?

Receptors that detect changes in blood pressure.

Where are important baroreceptors located?

The aortic arch and carotid arteries.

What do baroreceptors detect during dehydration?

A decrease in blood pressure.

How does the heart respond to decreased blood pressure?

It may increase its rate or strength of contraction.

What does RAAS stand for?

Renin-angiotensin-aldosterone system.

What activates the RAAS during dehydration?

Reduced blood volume and blood pressure stimulate the system.

What is angiotensin II?

A hormone that stimulates thirst, causes vasoconstriction, and promotes aldosterone release.

What does aldosterone do?

Increases sodium reabsorption and potassium excretion by the kidneys.

How does water follow sodium during reabsorption?

Water follows sodium back into the blood through osmosis.

What is the overall purpose of RAAS?

To help restore blood pressure, blood volume, and fluid balance.

Where does the body lose most of its water?

Through the renal system in urine.

Approximately how much water is lost through urine daily according to the slides?

About 1.5 liters.

What determines how much water the kidneys conserve or remove?

How much water the body takes in and how much it needs to conserve.

Where does ADH act in the kidneys?

The renal tubules, especially the collecting ducts.

What are the two major effects of ADH?

It constricts peripheral arterioles and increases water reabsorption by the kidneys.

How does ADH affect peripheral blood vessels?

It constricts arterioles, reducing blood flow to the extremities and supporting blood supply to the body core.

How does ADH increase water reabsorption?

It causes aquaporins to be inserted into collecting tubule cell membranes.

What happens when more aquaporins are inserted into collecting ducts?

More water moves from the urine filtrate back into the blood.

How does ADH affect urine production?

More ADH generally means more water reabsorption and less urine output.

What happens when ADH levels decrease?

Less water is reabsorbed by the kidneys, generally increasing urine output.

What is a diuretic?

A substance that increases urine production and decreases water conservation.

Why are diuretics prescribed?

They can help treat hypertension and congestive heart failure.

How does alcohol affect ADH?

Alcohol inhibits ADH release, increasing water loss in urine.

What other natural diuretic is mentioned in the slides?

Caffeine.

What are electrolytes?

Ions that help regulate important body functions.

What are the six major electrolytes?

Sodium, potassium, chloride, bicarbonate, calcium, and phosphate.