Acid Base Balance

What is the total body water content influenced by?

Age, body mass, gender, and body fat.

What percentage of body water content do infants have?

About 73% due to low body fat and bone mass.

How much body water content do men and women typically have?

Men have about 60%, women about 50% due to higher body fat.

What happens to body water as a person ages?

It declines and comprises about 45% of total body mass in old age.

What are the two main fluid compartments of the body?

Intracellular compartment and extracellular fluid.

What makes up the extracellular fluid subcompartments?

Blood plasma and interstitial fluid.

What are nonelectrolytes?

Organic molecules that do not dissociate in water and carry no net charge.

What are electrolytes and why are they significant?

Substances that dissociate in water to ions; they have greater osmotic power.

Which cation is the most abundant in extracellular fluids?

Sodium (Na+).

Which anion is major in extracellular fluids?

Chloride (Cl-).

What is the major cation in intracellular fluid?

Potassium (K+).

What is the major anion in intracellular fluid?

Phosphate (PO4^3-).

What do cells have more of compared to extracellular fluids?

Soluble proteins.

What are the most abundant solutes in body fluids?

Electrolytes, proteins, and some nonelectrolytes.

What effect does changing solute concentration in any compartment have?

It leads to net water flows.

How do substances reach the intracellular fluid?

They must pass through both the plasma and interstitial fluid.

What forces liquid into the interstitial fluid during exchanges between plasma and interstitial fluid?

Hydrostatic pressure.

How do nutrients and waste typically move between IF and ICF?

In one direction.

What must equal for the body to remain properly hydrated?

Water intake and water output.

What are the main sources of water intake?

Ingested liquids, food, and cellular metabolism.

What causes insensible water loss?

Evaporative loss from lungs and skin.

What triggers the thirst mechanism?

A decrease in plasma osmolality.

What quells thirst?

Moistening of the mouth mucosa and distention of the stomach and intestines.

What is obligatory water loss?

Water lost due to insensible losses, food residues, and a minimum of 500 ml in urine.

What does ADH regulate?

The amount of water reabsorbed in renal collecting ducts.

What happens when ADH levels are low?

Most water in the collecting ducts is not reabsorbed, resulting in dilute urine.

What leads to concentrated urine?

High levels of ADH leading to increased water reabsorption.

What is dehydration?

When water output exceeds water intake.

What can result from dehydration?

Weight loss, fever, mental confusion, or hypovolemic shock.

What is hypotonic hydration?

A result of renal insufficiency or excessive and rapid water intake.

What is edema?

The accumulation of fluid in the interstitial space.

What is the central role of sodium in fluid balance?

It regulates fluid and electrolyte balance due to its abundance and osmotic pressure.

What happens to plasma volume when sodium levels change?

A compensatory shift of water affects plasma volume and blood pressure.

What are some potent regulators of sodium balance?

Aldosterone, renin-angiotensin-aldosterone mechanism, and atrial natriuretic peptide.

What is aldosterone's main function?

Reabsorption of sodium in the kidneys.

What condition can trigger renin release?

Low blood volume and pressure.

What hormone counters the effects of aldosterone?

Atrial natriuretic peptide (ANP).

How does aldosterone affect potassium levels?

Its secretion enhances potassium secretion as sodium reabsorption increases.

What is the primary function of potassium in the body?

Maintaining membrane potential in neurons and muscle cells.

How is potassium balance chiefly regulated?

By renal mechanisms, which control potassium secretion in filtrate.

What influences potassium secretion levels?

Blood plasma levels of potassium.

Which hormones affect calcium ion levels?

Parathyroid hormone and calcitonin.

What happens during acidosis regarding chloride absorption?

Less chloride is absorbed as sodium absorption is coupled to bicarbonate.

What is the main chemical buffer system in extracellular fluid?

The bicarbonate buffer system.

What happens to bicarbonate when a strong acid is added?

It binds excess H+ forming more carbonic acid.

How do kidneys regulate bicarbonate levels?

They can conserve or generate bicarbonate depending on H+ secretion.

What is the role of the respiratory system in acid-base balance?

It helps regulate blood pH by managing levels of CO2.

What occurs during hypercapnia?

Blood pH drops, activating respiratory centers to increase breathing rate.

What is the role of kidneys in acid-base balance?

They remove acids and regulate alkaline substances.

What is metabolic acidosis characterized by?

Low blood pH and bicarbonate levels.

What distinguishes metabolic alkalosis?

Rising blood pH and bicarbonate levels.

What is the normal pH range for life?

Between 6.8 and 7.8.

What happens to respiratory rate during metabolic acidosis?

It increases to help eliminate CO2.

What do kidneys do during respiratory acidosis?

Retain bicarbonate to compensate for high CO2 levels.

How do kidneys respond to respiratory alkalosis?

They actively excrete bicarbonate to lower pH.

What can result from excessive loss of bicarbonate?

Metabolic acidosis.

What happens if blood pH rises above 7.45?

The body is in alkalosis.

What effect does lactic acid have in the body?

It contributes to metabolic acidosis.

When does CO2 play a significant role in blood pH?

When it accumulates due to hypoventilation.

What is the bicarbonate system's weak acid and weak base?

Carbonic acid is the weak acid; sodium bicarbonate is the weak base.

What assists in the body’s acid-base balance?

The respiratory and renal systems.

How does blood react when CO2 levels drop?

Blood pH increases, leading to respiratory alkalosis.

When are bicarbonate levels typically higher in the blood?

During respiratory acidosis.

What causes an increase in respiratory rate?

Metabolic acidosis leads to increased removal of CO2.

How does sodium influence water absorption?

Sodium absorption creates osmotic absorption of water.

What typically occurs during acidosis in terms of potassium levels?

ECF potassium levels rise.

How does acute dehydration affect body physiology?

It may lead to symptoms like confusion or shock.

How are soluble proteins distributed in body compartments?

They are present in higher concentrations in intracellular fluids.

What physiological changes occur due to dehydration?

Dehydration can lead to decreased blood volume and pressure.

What is the first response to a rise in extracellular fluid osmolality?

The thirst mechanism is triggered.

How is electrolyte balance crucial to cellular function?

It influences neural and muscular excitability.

What happens to blood volume during excessive sweating without fluid replacement?

Blood volume decreases, which can affect blood pressure.

What indicates a need for aldosterone release?

Sympathetic stimulation or decreased blood pressure.

What do the kidneys excrete to manage blood pH during acidosis?

They excrete hydrogen ions.

How does the cardiovascular system respond to low blood pressure?

Increases sympathetic stimulation and renal blood flow.

What can alter respiratory functions during metabolic imbalances?

Normal breathing rates can change in response to blood pH alterations.

Which hormone controls water retention by affecting sodium transport?

Aldosterone.

In what way can the hypothalamus influence fluid balance?

By regulating the secretion of ADH based on plasma osmolarity.

What role does the atrial natriuretic peptide play?

It promotes sodium excretion and lowers blood pressure.

What is characteristic of protein buffers?

They can bind or release H+ depending on pH changes.

What triggers physiological buffering systems to respond to pH shifts?

Significant changes in acid or base levels.

What is the role of kidneys during prolonged acidosis?

To restore bicarbonate levels and manage hydrogen excretion.

How do dietary sources affect acid-base balance?

Food intake influences the overall acid load in the body.

What can result from rapid changes in bicarbonate levels?

Acute shifts in blood pH and acid-base imbalance.

How does hormonal regulation of sodium relate to extracellular fluid volume?

Sodium retention affects ECF volume and consequently blood pressure.

What is the physiological response to inhaling excess CO2?

Increase in respiratory rate to expel additional CO2.

How does temperature relate to metabolic reactions in the body?

Temperature affects enzymatic activity, impacting metabolic reactions.