Physiology Thermoregulation and Fluid Balance

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Questions and Answers

What is the primary role of thermoreceptors in the thermoregulatory system?

To detect changes in body temperature (correct)

To increase muscle activity during cold temperatures

To regulate blood flow to organs

To enhance the immune response

What effect does an increase in body temperature have on blood flow to the skin?

Blood flow to the skin remains unchanged

Blood flow to the skin decreases

Blood flow to the skin increases (correct)

Blood flow to internal organs increases

Which component serves as the integrator in the thermoregulatory system?

Sweat glands

Thermoreceptors

Hypothalamus (correct)

Skeletal muscles

How does the body respond to a decrease in temperature within the thermoneutral zone?

Blood flow to the skin decreases (C) Signup and view all the answers

What is a characteristic of positive feedback mechanisms?

They cause variables to move away from the set point (A) Signup and view all the answers

What is the primary component of Intracellular Fluid (ICF)?

Proteins and organic anions (C) Signup and view all the answers

Which type of fluid surrounds the cells but does not circulate?

Interstitial fluid (ISF) (D) Signup and view all the answers

What percentage of total body water does the Extracellular Fluid (ECF) represent?

20% (C) Signup and view all the answers

What is a defining characteristic of the body's internal environment?

It remains remarkably constant despite external changes. (B) Signup and view all the answers

Which fluid compartment comprises about 1/4 of the Extracellular Fluid (ECF)?

Plasma (B) Signup and view all the answers

How much total body water does a 70 kg man have?

42 liters (D) Signup and view all the answers

What is the primary solute in the extracellular fluid?

Sodium (Na+) (B) Signup and view all the answers

Transcellular fluid includes which of the following?

Cerebrospinal fluid (A) Signup and view all the answers

What is the primary mechanism for maintaining homeostasis?

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

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

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

What defines homeothermic animals?

They maintain body temperature within a narrow range. (B) Signup and view all the answers

Which buffer system is considered the most important in the body?

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

What occurs when the body temperature rises above 41°C?

Hyperthermia is established, which is dangerous. (B) Signup and view all the answers

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

Biochemical change (C) Signup and view all the answers

How does the respiratory system help regulate pH?

By controlling the blood's CO2 tension (A) Signup and view all the answers

What condition is likely to develop if CO2 removal is less than CO2 production?

Respiratory acidosis (D) Signup and view all the answers

What happens in the kidney during diabetic conditions?

Excretion of ketoacids (C) Signup and view all the answers

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

To compare the set point to the actual level of the variable (D) Signup and view all the answers

What occurs in metabolic acidosis regarding breathing patterns?

Hyperventilation occurs (A) Signup and view all the answers

What is the ultimate defense against H+ ion homeostasis in the body?

Renal regulation (D) Signup and view all the answers

What is considered hypothermia?

Decreasing body temperature below normal levels (D) Signup and view all the answers

Which mechanism is considered more powerful than all chemical buffers combined?

Respiratory regulation (A) Signup and view all the answers

What type of change triggers a reaction to oppose the change in negative feedback control?

An external change (A) Signup and view all the answers

In the bicarbonate-carbonic acid system, what happens when a strong acid is added to plasma?

It neutralizes the acid to form NaCL and H2CO3 (A) Signup and view all the answers

What percentage of total body water is present in neonates?

75-80% (A) Signup and view all the answers

At what age does total body water as a percentage of body weight reach 50% in males?

60 years (D) Signup and view all the answers

What is the total daily water intake in milliliters?

2300 ml (B) Signup and view all the answers

Which fluid output represents the highest volume per day?

Urine (D) Signup and view all the answers

What proportion of interstitial fluid is larger in neonates compared to adults?

Three times larger (B) Signup and view all the answers

What is the typical daily output of water from the skin (insensible) in milliliters?

350 ml (B) Signup and view all the answers

What cation is present in the highest concentration in plasma water?

Sodium (D) Signup and view all the answers

What is the total output of water per day?

2300 ml (C) Signup and view all the answers

How much potassium is found in intracellular fluid?

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

What change occurs in total body water with aging?

Decreases due to increased fat (D) Signup and view all the answers

What is the primary function of water in living cells?

Makes up 60 to 80% of the cell volume (B) Signup and view all the answers

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

HCl (A) Signup and view all the answers

What characterizes acids in terms of hydrogen ions?

They release hydrogen ions in detectable amounts. (A) Signup and view all the answers

Which statement about bases is true?

They dissociate liberating hydroxyl ions. (D) Signup and view all the answers

What is the pH of pure water at standard conditions?

7 (C) Signup and view all the answers

Which of the following sources contributes to hydrogen ion concentration in the body?

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

What does a pH value greater than 7 indicate?

Basic solution (B) Signup and view all the answers

What process can lead to the accumulation of lactic acid in the body?

Prolonged muscle contraction (A) Signup and view all the answers

Study Notes

Introduction to Human Physiology

Physiology is the study of the biological functions of organs and their interconnectedness.
To understand human physiology, the multilevel organization of the human body will be utilized.
The internal environment of the body maintains remarkable consistency despite external environmental changes.

The Body's External Environment

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

The Body's Internal Environment

The internal environment is the fluid surrounding cells.
In a 70 kg human, total body water amounts to 42 liters.
Intracellular fluid (ICF) makes up 28 liters of this.
Extracellular fluid (ECF) comprises 14 liters.
- Plasma accounts for 3 liters of ECF.
- Interstitial fluid (ISF) accounts for 11 liters of ECF.

Intracellular Fluid (ICF)

ICF constitutes about 2/3 of body water.
Approximately 40% of a person's weight is ICF.
ICF is primarily composed of potassium ions, organic anions, and proteins.
ICF composition is not uniform throughout, but a collection of fluids from different cells.

Extracellular Fluid (ECF)

ECF comprises 1/3 of body water.
ECF is approximately 20% of a person's weight.
It primarily consists of sodium and bicarbonate ions.
ECF is further divided into interstitial fluid and plasma.
Interstitial fluid surrounds cells and makes up 3/4 of the ECF.
Plasma is the extracellular component of blood, accounting for 1/4 of ECF.

Transcellular Fluid

Transcellular fluid is situated outside the typical compartments.
These fluids sum up to 1-2 liters, encompassing fluids like cerebrospinal fluid (CSF), digestive juices, and mucus.

Variation in Body Fluids due to Age

Neonates possess a higher proportion of water (75-80%) compared to adults.
Interstitial fluid is significantly greater in infants than in adults.
By the age of one year, the proportion decreases to the adult value of 60%.
Water content in the body decreases with increasing age.
By age 60, total body water (TBW) comprises only 50% of total body weight in males, mostly due to increasing adipose tissue.

Daily Intake and Output of Water (ml/day)

Daily water intake consists of ingested fluids (2100 ml) and metabolic water (200 ml).
Total intake totals to 2300ml
Daily water output includes insensible losses through skin and lungs (350ml each), sweat (100 ml), feces (100 ml), and urine (1400 ml).
Total output totals to 2300ml

Body Fluid Composition (mEq/L)

Data presented in a table shows the relative concentrations of electrolytes and anions in plasma, interstitial fluid, and intracellular fluid.

Inorganic Compounds

Water is the most abundant and crucial inorganic compound in living materials.
It represents 60-80% of most living cells.

Salts

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

Acids

Acids are substances that release hydrogen ions (H+) in measurable amounts.
Because a hydrogen ion is simply a hydrogen nucleus, acids can also be defined as proton donors.
Common body acids include HCl and H2CO3.
Acid strength is determined by the degree of H+liberation.

Bases

Bases are substances that release hydroxyl ions (OH-) when dissolved in water or remove H+ ions from solution.
They are sometimes referred to as proton acceptors.
Common bases in the body include NaOH and ammonia (NH3).

pH

pH scale measures the hydrogen ion (H+) concentration in a solution.
The range of the pH scale is 0 to 14.
A pH of 7 is neutral.
pH below 7 is acidic, above 7 is alkaline.
The pH formula is pH = -log[H+].

Sources of H+ in the body

Oxidation of carbon in foods creates CO2, which dissolves into fluids, forming carbonic acid (H2CO3) and releasing H+ and bicarbonate (HCO3-).
Oxidation of sulfur and phosphorus in proteins and lipids can lead to acidosis.
Ingestion of acids like lemon juice or acidifying salts like NH4Cl.
Anaerobic glycolysis in muscles during prolonged exertion can lead to lactic acid build-up.
Hydrolysis of high-energy phosphate bonds in ATP or CP releases H+.

Body Defensive Mechanisms Against pH Disturbances

Body metabolism and muscle activities produce acids, so the body has an alkaline reserve to counteract.
Chemical buffering, respiratory regulation (1-12 minutes), and renal regulation (hours to days) are crucial for pH homeostasis.

Homeostasis

Maintaining a stable internal environment optimal for life is called homeostasis.
Most organ systems contribute to maintaining homeostasis.

Negative Feedback Control in Homeostasis

Negative feedback is the main mechanism for achieving homeostasis.
External changes trigger adjustments in the internal environment.
Regulatory responses oppose the change and return the regulated variable to its normal set point.

Negative Feedback Mechanisms

Set point is the desired level of a regulated variable.
Sensors detect the regulated variable level and feed the information to an integrating center.
The integrating center compares the input to the set point.
The difference between the actual and set point values is the error signal.
The integrating center controls effectors.
Effectors make adjustments to return the variable toward the set point.

Negative Feedback Example (Blood Glucose)

Insulin and glucagon regulate blood glucose levels by either storing glucose as glycogen or releasing stored glucose into the blood to maintain normal values.

Thermoregulation

Homeothermic animals maintain a narrow range of body temperature, while poikilothermic animals do not regulate their body temperature.
In humans, the normal body temperature is 37°C (98.6°F).
Hypothermia is a decrease in body temperature, while hyperthermia is an elevation of body temperature above 41°C (dangerous), and above 43°C (deadly).
Mechanisms of heat transfer include radiation, conduction, evaporation (sweating), and convection.
Thermoregulatory components include thermoreceptors, hypothalamus, and effectors (sweat glands, blood vessels).
The thermoneutral zone is the range of environmental temperatures where blood flow controls the body temperature.

Fever

Fever is often associated with infections.
White blood cells release substances (pyrogens) which increase the body's set point for temperature.
Fever enhances immune responses.

Positive Feedback

Positive feedback loops typically do not maintain homeostasis, but are characterized by short duration and infrequent use.
An example is blood clotting, where the response to a stimulus (blood vessel damage) causes a variable to move further away from its normal level, such as a blood clot formation until the damage is sealed.
Similar to blood clotting, there are other positive feedback loops (such as uterine contractions during childbirth) in the body .

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Description

This quiz covers essential concepts related to thermoregulation and fluid balance in the human body. Questions explore the roles of thermoreceptors, the impact of temperature on blood flow, and the characteristics of various fluid compartments. Test your understanding of homeostasis and extracellular fluid properties.