Human Physiology Water Balance Quiz

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Questions and Answers

What is the percentage of total body water in a healthy adult male?

75%

80%

50% (correct)

60%

Which of the following is NOT a major route of water output?

Sweat

Urine

Feces

Inhalation (correct)

Which of these components contributes the MOST to the total cation concentration in plasma?

Magnesium

Sodium (correct)

Potassium

Calcium

What is the approximate percentage of total body water in a neonate?

80% (A) Signup and view all the answers

Which fluid compartment contains the highest concentration of potassium?

Intracellular Fluid (C) Signup and view all the answers

How does the concentration of chloride ions in interstitial fluid compare to plasma?

Higher in interstitial fluid (B) Signup and view all the answers

What is the primary mechanism for regulating total body water?

Hormonal regulation (D) Signup and view all the answers

What is the approximate daily water intake for a healthy adult?

2300 ml (B) Signup and view all the answers

Which component contributes the most to the total anion concentration in intracellular fluid?

Phosphate (A) Signup and view all the answers

How does the proportion of extracellular fluid (ECF) in neonates compare to adults?

Higher in neonates (B) Signup and view all the answers

What role do thermoreceptors play in the thermoregulatory system?

Detecting temperature changes (C) Signup and view all the answers

What occurs within the thermoneutral zone?

The body temperature is maintained by altering blood flow. (A) Signup and view all the answers

How does fever affect the immune response?

It enhances the immune response. (B) Signup and view all the answers

Which system is responsible for integrating temperature information in the body?

Hypothalamus (A) Signup and view all the answers

What characterizes positive feedback in a regulatory mechanism?

It induces rapid changes in a variable. (D) Signup and view all the answers

What is the primary role of physiology in relation to the human body?

To examine the biological functions of organs and their interrelationships. (D) Signup and view all the answers

What constitutes the internal environment of the human body?

Fluid surrounding cells known as extracellular fluid (ECF). (B) Signup and view all the answers

What percentage of the body's total water is intracellular fluid (ICF)?

66% (A) Signup and view all the answers

Which statement about extracellular fluid (ECF) is correct?

ECF is made primarily of NaCl and NaHCO3 solutions. (C) Signup and view all the answers

Interstitial fluid (ISF) is best described as:

Fluid that surrounds the cells but does not circulate. (A) Signup and view all the answers

What is the total body water of a 70 kg man approximately?

42 liters (A) Signup and view all the answers

Transcellular fluid can be described as:

Fluids outside of the normal compartments like CSF and digestive juices. (C) Signup and view all the answers

Which of the following best defines the term 'homeostasis' as it relates to the body's internal environment?

The body's ability to maintain stability despite external changes. (B) Signup and view all the answers

What is the most abundant inorganic compound in living materials?

Water (A) Signup and view all the answers

Which of the following is a characteristic of acids?

Releases hydrogen ions (A) Signup and view all the answers

What kind of pH value indicates a basic solution?

pH greater than 7 (C) Signup and view all the answers

What does a pH value of 7 indicate about a solution?

It is neutral (C) Signup and view all the answers

Which of the following is classified as a salt?

KCl (B) Signup and view all the answers

Which of the following substances can be considered a base?

NaOH (C) Signup and view all the answers

What is the role of hydroxyl ions in the definition of bases?

They remove H+ ions from solution (D) Signup and view all the answers

Which ion is a common source of hydrogen ions (H+) in the body?

Carbon dioxide (CO2) (A) Signup and view all the answers

What is the primary mechanism responsible for maintaining homeostasis?

Negative feedback control (A) Signup and view all the answers

What happens when the integrating center detects an error signal?

It sends output to effectors to correct the variable (D) Signup and view all the answers

In humans, what is the normal set point for body temperature?

37°C (98.6°F) (C) Signup and view all the answers

Which of the following describes poikilothermic animals?

They do not regulate their body temperature (D) Signup and view all the answers

What would an increase in body temperature above 43°C indicate?

A potential for hyperthermia (C) Signup and view all the answers

What is one mechanism of heat transfer that involves direct contact?

Conduction (A) Signup and view all the answers

In the context of renal function, what does the kidney excrete during alkalosis?

NaHCO3 (A) Signup and view all the answers

Which of the following correctly describes the relationship between sensors and the integrating center in homeostasis?

Sensors detect the regulated variable and provide input (B) Signup and view all the answers

What is the primary function of chemical buffers in the body?

To minimize changes in pH when acids or bases are added (A) Signup and view all the answers

How rapidly do chemical buffers respond to pH disturbances?

In a fraction of a second (D) Signup and view all the answers

Which buffer system is considered more important than all other body buffer systems?

The bicarbonate-carbonic acid system (D) Signup and view all the answers

What role does the respiratory system play in pH regulation?

It controls CO2 tension, affecting H+ ion concentration (D) Signup and view all the answers

What occurs during hypoventilation in relation to pH balance?

Increased CO2 content leading to respiratory acidosis (C) Signup and view all the answers

How does hyperventilation affect blood pH when metabolic acidosis occurs?

It leads to respiratory alkalosis (C) Signup and view all the answers

What is the final and most important defense against H+ ion concentration disturbances?

Renal regulation (B) Signup and view all the answers

Which of the following statements about respiratory regulation of pH is true?

It serves as a feedback regulatory system for pH (B) Signup and view all the answers

Study Notes

Introduction to Human Physiology

Physiology is the study of the biological functions of organs and their interrelationships.
This study utilizes the many levels of organization of the human body.
The internal environment remains remarkably constant despite changing external conditions.
The interior of the body is separated from the external environment by a layer of epithelial tissue.
The lumen of the respiratory, gastrointestinal, and urinary systems are part of the external environment.
Internal environment is defined as the fluid surrounding cells (extracellular fluid).

Body Fluid

A 70kg man has a total body water (TBW) of 42 liters
- 28 liters of intracellular fluid (ICF)
- 14 liters of extracellular fluid (ECF)
  - 3 liters are plasma
  - 11 liters are interstitial fluid (ISF)
Intracellular fluid (ICF) comprises 2/3 of the body's water content.
- ICF is approximately 40% of body weight in a person who is 60% water by weight.
- Primarily a solution of potassium and organic anions, proteins, and other particles.
Extracellular fluid (ECF) comprises 1/3 of the body's water content.
- ECF is primarily a NaCl and NaHCO3 solution.
- Subdivided into interstitial fluid (ISF) and plasma.
- Interstitial fluid surrounds cells and does not circulate; approximately 3/4 of ECF.
- Plasma circulates as the extracellular component of blood and is approximately 1/4 of ECF.
Transcellular fluid are fluids outside of the normal compartments, including cerebrospinal fluid (CSF), digestive juices, mucus, etc.

Variation Due to Age

Neonates contain more water than adults (75-80%).
Extracellular fluid is proportionally larger at birth compared to adults.
By 12 months of age, the proportion of body water has decreased to 60%, the adult value.
Total body water decreases progressively with age, reaching only 50% of total body weight by the age of 60 in males, mainly due to an increase in adipose tissue.

Daily Intake and Output of Water

Input:
- Fluids ingested: 2100 ml/day
- From metabolism: 200 ml/day
- Total intake: 2300 ml/day
Output:
- Insensible-skin: 350 ml/day
- Insensible-lungs: 350 ml/day
- Sweat: 100 ml/day
- Feces: 100 ml/day
- Urine: 1400 ml/day
- Total output: 2300 ml/day

Composition

Electrolytes and anions (concentrations in mEq/L in parentheses):
- Sodium (Plasma: 142, ECF: 153, ISF: 145, ICF: 10)
- Potassium (Plasma: 4, ECF: 4.3, ISF: 4, ICF: 160)
- Calcium (Plasma: 5, ECF: 5.4, ISF: 5, ICF: 2)
- Magnesium (Plasma: 2, ECF: 2.2, ISF: 2, ICF: 26)

Inorganic Compounds

Water is the most abundant and important inorganic compound in living materials, comprising 60-80% of most living cells.

Salts

Salts are ionic compounds containing cations other than H⁺ and anions other than the hydroxyl ion (OH⁻).
When dissolved in water, they dissociate into their component ions.
Common body salts include NaCl, CaCO3, KCl, Ca3(PO4)2.
Other important body ions include Fe, I, Mg, and Zn.

Acids

Acids are substances that release hydrogen ions (H⁺) in detectable amounts.
A hydrogen ion is a hydrogen nucleus and therefore, acids are also proton donors.
Common body acids include HCl and H2CO3.
Acids can be strong or weak depending on the amount of hydrogen ions liberated.

Bases

Bases are substances which dissociate liberating hydroxyl ions (OH⁻).
Bases remove H⁺ ions from solution and are often called proton acceptors.
Common body bases include NaOH and ammonia (NH3).

pH

The concentration of H⁺ in a solution is usually indicated in pH units on a pH scale that runs from 0 to 14.
- pH = -log[H⁺]
- [H⁺] = Molar H⁺ concentration
Acidic solutions have a pH of less than 7.
Basic solutions have a pH of greater than 7.
A solution with a pH of 7 is neutral, for example, water.

Sources of H⁺ in the body

Oxidation of carbon in organic foods produces CO2, which dissolves in fluids to form carbonic acid (H2CO3), releasing H+ and bicarbonate (HCO3-), about 300 Lit. CO2 & 13.000 mEq of H+ ion resulted per day in normal adults.
Oxidation of sulfur and phosphorus in proteins and lipids leads to acidosis.
Intake of acids (e.g. citric acid in lemons) or acidifying salts (e.g., NH₄Cl) also contributes.
Anaerobic glycolysis in muscles during prolonged contractions or starvation releases lactic acid.
Hydrolysis of high-energy phosphate bonds (e.g., ATP or CP) yields H⁺.

Body Defensive Mechanisms against pH Disturbances

Body metabolism and muscle activity tend to add acids to body fluids.
An alkaline reserve in the body system opposes this tendency.
The maintenance of stable pH depends on: -[A] Chemical buffers (very rapid, in a fraction of a second). -[B] Respiratory regulation (1-12 minutes). -[C] Renal regulation (hours to days).

Homeostasis

Homeostasis is the process of maintaining a stable internal environment, which is compatible for life.
Most organ systems contribute to homeostasis.

Negative Feedback Control

The primary mechanism for maintaining homeostasis is negative feedback control.
External changes trigger changes in regulated variables within the internal environment.
The reaction triggered by these changes opposes the change and returns the regulated variable back to its normal (set point).
- Set point is the desired level of the regulated variable.
- Sensors detect the level of the regulated variable and send information to the integrating center.
- The integrating center compares the set point and the actual level.
- If there is a difference (error signal), the integrating center sends instructions (output) to the effectors.
- Effectors initiate corrective actions to return the regulated variable to the set point.

Thermoregulation

Homeothermic animals regulate their body temperature within a narrow range.
Poikilothermic animals do not regulate their body temperature.
- Humans maintain a body temperature of 37°C (98.6°F).
- Hypothermia is a decrease in body temperature.
- Hyperthermia is an increase in body temperature; above 41°C is dangerous, and above 43°C is deadly.
Components of the thermoregulatory system include thermoreceptors (sensors), hypothalamus (integrator), and sweat glands, blood vessels, and skeletal muscles (effectors).
Heat transfer between the body and the external environment occurs via radiation, conduction, evaporation, and convection.
The thermoneutral zone is the range of outside temperatures where body temperature is regulated only by blood flow to the skin.

Fever

Fever accompanies infections.
White blood cells secrete pyrogens.
Body temperature set point increases.
Fever enhances immune response.

Positive Feedback

Positive feedback is a regulatory mechanism where the response to a stimulus causes the controlled variable to move farther from the set point.
Usually does not maintain homeostasis; it's characterized by being short in duration and infrequent.
- Example: blood clotting.

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Description

Test your knowledge on the physiology of water balance in the human body. This quiz covers topics such as total body water percentages, routes of water output, and fluid compartments. Perfect for students studying human physiology or related health sciences.