Human Physiology: Internal Environment Quiz

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Questions and Answers

What is the primary component of the internal environment?

Transcellular fluid

Extracellular fluid (correct)

Intracellular fluid

Interstitial fluid

Which of these is NOT a component of the extracellular fluid?

Cytoplasm (correct)

Plasma

Transcellular fluid

Interstitial fluid

What percentage of a 70 kg man's body weight is made up of intracellular fluid?

60%

40% (correct)

10%

20%

What is the main difference between interstitial fluid and plasma?

Interstitial fluid does not circulate, while plasma does. (B) Signup and view all the answers

What is a major component of intracellular fluid?

Potassium (B) Signup and view all the answers

What does it mean to say that the internal environment remains remarkably constant despite changing conditions in the external environment?

The body is able to maintain a stable internal environment even when the external environment is changing. (C) Signup and view all the answers

What is the role of epithelial tissue in maintaining a stable internal environment?

Epithelial tissue helps regulate the movement of substances between the internal and external environments. (C) Signup and view all the answers

What is the primary function of transcellular fluid?

To lubricate and protect various body cavities and organs. (C) Signup and view all the answers

What type of compound is water?

Inorganic (D) Signup and view all the answers

What is the definition of a salt?

An ionic compound containing cations other than H+ and anions other than OH- (C) Signup and view all the answers

Which of the following is NOT a salt commonly found in the body?

Fe (D) Signup and view all the answers

What is the primary characteristic of an acid?

It releases hydrogen ions in solution (C) Signup and view all the answers

What is a base?

A substance that removes hydrogen ions from solution (B), A substance that accepts protons (C) Signup and view all the answers

What is the pH of a neutral solution?

7 (C) Signup and view all the answers

Which of the following is a source of H+ ions in the body?

Oxidation of carbon in organic food substances (A) Signup and view all the answers

What is the pH scale used for?

Measuring the concentration of hydrogen ions in a solution (A) Signup and view all the answers

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

75% (D) Signup and view all the answers

How does the volume of interstitial fluid in neonates change with their development?

It decreases significantly to adult levels. (A) Signup and view all the answers

What is the primary factor causing the decrease in total body water percentage in older adults?

Increased fat tissue. (B) Signup and view all the answers

Approximately how much water is typically consumed in a day, through fluids?

2100 ml (C) Signup and view all the answers

What is the water loss through sweat, feces and urine, combined?

1500 ml (C) Signup and view all the answers

Which compartment of the body has the highest concentration of potassium ions?

Intracellular fluid (A) Signup and view all the answers

What is the approximate concentration of sodium ions in interstitial fluid?

153 mEq/L (D) Signup and view all the answers

Which of the following ions has the highest concentration in intracellular fluid?

Potassium (C) Signup and view all the answers

Which of these is NOT an anion?

Potassium (A) Signup and view all the answers

What is the approximate concentration of protein in the plasma?

16 mEq/L (C) Signup and view all the answers

Which of the following is NOT a factor that contributes to the maintenance of pH in the body?

Hormonal regulation (D) Signup and view all the answers

What is the main source of H+ ions in the body that is regulated by the respiratory system?

Carbonic acid (H2CO3) (C) Signup and view all the answers

Which buffer system is considered more important than all the others in the body?

Bicarbonate-carbonic acid system (C) Signup and view all the answers

What is the primary mechanism by which the renal system regulates pH?

Excretion of hydrogen ions (A) Signup and view all the answers

What condition occurs when the rate of CO2 removal from the alveoli is less than the rate of CO2 production by cells?

Respiratory acidosis (D) Signup and view all the answers

Which of the following is a characteristic of the chemical buffer system in maintaining pH balance?

Rapid response time (B) Signup and view all the answers

What is the effect of hyperventilation on blood pH?

Increases blood pH (B) Signup and view all the answers

How does the respiratory system act as a feedback regulatory system for pH control?

By adjusting the rate of CO2 removal from the blood (B) Signup and view all the answers

Which of the following is NOT a mechanism by which the kidney helps regulate pH?

Excretion of Na+ in alkalosis (A) Signup and view all the answers

What is the primary mechanism by which the body maintains homeostasis?

Negative feedback (B) Signup and view all the answers

What is the role of the integrating center in negative feedback?

Comparing the set point to the actual level of the regulated variable (B) Signup and view all the answers

What is the difference between homeothermic and poikilothermic animals?

Homeothermic animals can regulate their body temperature, while poikilothermic animals cannot (A) Signup and view all the answers

Which of the following is NOT a mechanism of heat transfer between the body and the external environment?

Osmosis (C) Signup and view all the answers

What is the normal human body temperature in Celsius?

37°C (B) Signup and view all the answers

What is hyperthermia?

Increase in body temperature above 41°C (C) Signup and view all the answers

Which of the following is an example of insensible water loss?

Evaporation of water from the skin (D) Signup and view all the answers

Which of the following is NOT a part of the thermoregulatory system?

Liver (A) Signup and view all the answers

What is the thermonetural zone?

The range of outside temperatures where alterations in blood flow alone regulate body temperature (D) Signup and view all the answers

What happens to blood flow to the skin when body temperature increases?

It increases to dissipate heat (D) Signup and view all the answers

What is the role of pyrogens in fever?

They cause an increase in the body's set point for temperature (D) Signup and view all the answers

Which of the following is an example of positive feedback in the body?

The release of oxytocin during labor, which further stimulates contractions (A) Signup and view all the answers

Why is positive feedback generally not involved in maintaining homeostasis?

It is usually short in duration and infrequent (B) Signup and view all the answers

Study Notes

Introduction to Human Physiology

Physiology is the study of biological functions of organs and their relationships.
This study utilizes many levels of human body organization.
The internal environment remains remarkably constant despite external changes.

The Body's External Environment

The interior of the body is separated from the external environment by a layer of epithelial tissue.
Structures like the respiratory, gastrointestinal, and urinary systems' lumens are considered part of the external environment.

The Body's Internal Environment

The internal environment is the fluid surrounding cells.
A 70 kg man has a total body water of 42 liters.
Intracellular fluid (ICF) makes up 28 liters (about 40% of body weight)
Extracellular fluid (ECF) accounts for 14 liters, consisting of 3 liters of plasma and 11 liters of interstitial fluid.

Body Fluid Compartments

Total body water (TBW) = 42 liters.
ICF = 28 liters.
ECF = 14 liters (Plasma = 3 liters, Interstitial fluid = 11 liters)

Intracellular Fluid (ICF)

ICF comprises two-thirds of the body's water (approximately 40% of body weight).
ICF is primarily a solution of potassium and organic anions; proteins are also present.
The ICF isn't uniform throughout the body, with variations between cells.

Extracellular Fluid (ECF)

ECF is one-third of the body's water (approximately 20% of body weight).
ECF is chiefly a solution of sodium chloride (NaCl) and sodium bicarbonate (NaHCO3).
ECF is subdivided into interstitial fluid (ISF), which surrounds the cells (about 3/4 of ECF), and plasma (about 1/4 of ECF), which is the extracellular component of blood.

Transcellular Fluid

This comprises 1-2 liters of fluid not contained within the usual body compartments.
Examples include cerebrospinal fluid (CSF), digestive juices, and mucus.

Variation Due to Age

Neonates have a higher water content (75-80%) compared to adults.
By 12 months of age, the water percentage is closer to the adult value (60%).
Total body water percentage of total body weight decreases with aging and is around 50% in 60-year-old men, mostly due to increased fat tissue.

Daily Intake and Output of Water (ml/day)

Input:
- Ingested fluids: 2100 ml
- Metabolic Water: 200 ml
- Total Intake: 2,300ml
Output:
- Insensible water loss (skin): 350 ml
- Insensible water loss (lungs): 350 ml
- Sweat: 100 ml
- Feces: 100 ml
- Urine: 1400 ml
- Total Output: 2,300ml

Body Fluid Composition

Data provided as a table showing the composition of electrolytes (e.g. sodium, potassium) and anions (e.g., chloride, bicarbonate) in plasma, interstitial fluid, and ICF in mEq/L.

Inorganic Compounds

Water is the most plentiful and critical inorganic substance in living matter.
It constitutes 60-80% of the volume of most living cells.

Salts

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

Acids

Acids release hydrogen ions (H+) in noticeable amounts.
They're also proton donors.
Common body acids: HCl, H2CO3.
Acids can be strong or weak depending on the amount of H+ ions they liberate.

Bases

Bases dissociate, liberating hydroxyl ions (OH-).
They are often called proton acceptors.
Common body bases: NaOH, ammonia (NH3).

pH

pH indicates the concentration of H+ in a solution.
The pH scale ranges from 0 to 14, with 7 being neutral.
pH = -log[H+] where [H+]=molar H+ concentration.
Acidic solutions have a pH less than 7, and basic solutions have a pH greater than 7.
Water has a neutral pH of 7.

Sources of H+ in the Body

Oxidation of carbon in organic food substances produces CO2 which further forms carbonic acid (H2CO3). This process releases H+ ions and bicarbonate ions (HCO3−) in the body daily.
Oxidation of sulfur and phosphorus in proteins and lipids can result in acidosis.
Ingestion of acids or acidifying salts like NH4Cl is another source.
Anaerobic glycolysis in muscle tissue during prolonged activity or starvation leads to lactic acid.
Hydrolysis of ATP and CP also results in H+ production.

Body Defensive Mechanisms Against pH Disturbances

Body metabolism and muscle activity tend to increase acidity in the body fluids.
The body has alkaline reserves to help to counteract this tendency.

Maintenance of pH

Chemical buffers act quickly (in a fraction of a second).
Respiratory regulation takes 1–12 minutes.
Renal regulation is the slowest but most effective method for correction and takes hours to days.

Homeostasis

Homeostasis is the process of maintaining a stable internal environment conducive to life.
Many organ systems contribute to homeostasis.

Negative Feedback Control in Homeostasis

This is the primary mechanism maintaining homeostasis.
External changes trigger changes in internal variables that trigger responses to oppose the change, returning the variable to the normal set point.

Negative Feedback Mechanisms

Set point is the desired level of a regulated variable.
Sensors detect the variable and report it to an integrating center.
The integrating center compares the variable's level to the set point.
The error signal is the difference between the actual level and the set point.
The integrating center sends signals to effectors to adjust the variable toward the set point.

Negative Feedback Example: Blood Glucose Regulation

High blood glucose level stimulates insulin release from the pancreas
Insulin facilitates glucose uptake by cells, lowering blood glucose levels.
Low blood glucose level stimulates glucagon release, which promotes glucose release from the liver, increasing blood glucose levels.

Thermoregulation

Homeothermic animals maintain a stable body temperature within a narrow range, while poikilothermic animals do not.
Normal human body temperature is 37°C (98.6°F).
Hypothermia is a decrease in body temperature, and hyperthermia is an increase. Above 41°C is dangerous; above 43°C is usually deadly.
Heat transfer between the body and the environment occurs through radiation, conduction, evaporation (sweating), and convection.
Thermoregulatory components include receptors, integrating center (hypothalamus), and effectors (blood vessels, sweat glands, muscles).

Thermoneutral Zone

This is the range of outside temperatures where changes in blood flow in the skin can adequately maintain body temperature.

Positive Feedback

Positive feedback is a regulatory mechanism where the response to a stimulus causes the controlled variable to move further from the set point.
Positive feedback loops are usually short-term, or infrequent.
Example: blood clot formation.

Fever

Fever is an increase in body temperature that accompanies infections.
White blood cells release pyrogens to raise the body temperature set point.
Fever enhances the body's immune response.

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Description

Test your knowledge on the internal environment of the human body. This quiz covers essential components such as extracellular fluid, intracellular fluid, and the role of epithelial tissue. Dive into the details of body fluids, pH levels, and their significance in maintaining homeostasis.