Physiology Lecture (1) Exam

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Questions and Answers

What is the basic unit of structure and function in the human body?

Organ

Cell (correct)

System

Tissue

How much of the total body fluids is classified as intracellular fluid (ICF)?

2/3 (correct)

1/3

40-42 liters

10-12 liters

Which of the following is NOT a component of extracellular fluid (ECF)?

Cytoplasm (correct)

Interstitial fluid

Plasma

Trans-cellular fluid

What is the primary fluid composition of the extracellular fluid (ECF)?

Sodium and chloride ions Signup and view all the answers

Which of the following correctly describes the relationship between intracellular fluid and extracellular fluid?

ICF is separated from ECF by the cell membrane Signup and view all the answers

What proportion of body fluids does the extracellular fluid (ECF) represent?

1/3 Signup and view all the answers

What type of fluid is found in the spaces between cells?

Interstitial fluid Signup and view all the answers

Which of the following is a component of body fluids?

Inorganic molecules Signup and view all the answers

Which criterion is NOT essential for the indicators or dyes used in body fluid measurement?

Rapidly excreted Signup and view all the answers

Which indicator is most frequently used to measure total body water (TBW)?

Heavy water (D2O) Signup and view all the answers

What is the primary function of body water in the human body?

Regulation of all chemical reactions Signup and view all the answers

Which of the following statements about the distribution of body water is accurate?

The percentage of water decreases with increased fat percentage. Signup and view all the answers

Which indicator is specifically used to measure extracellular fluid (ECF) volume?

Mannitol Signup and view all the answers

How is intracellular fluid volume calculated?

TBW - ECF volume Signup and view all the answers

What happens to total body water percentages from childhood to old age?

They decrease. Signup and view all the answers

Which of the following is a trait of an ideal dye for measuring the plasma volume?

Non-toxic and bound to plasma protein Signup and view all the answers

What is the primary role of water in regulating body temperature?

It evaporates with a high latent heat. Signup and view all the answers

How much water intake is estimated as normal per day?

2400 ml Signup and view all the answers

What is the primary function of homeostasis?

To maintain a constant internal environment Signup and view all the answers

Which hormone primarily controls urine volume?

Antidiuretic hormone (ADH) Signup and view all the answers

What is not a method of water output from the body?

Metabolism Signup and view all the answers

Which system is responsible for rapid responses in maintaining homeostasis?

Nervous system Signup and view all the answers

What is the purpose of negative feedback mechanisms?

To stabilize the internal environment Signup and view all the answers

Which statement accurately describes the role of water in the digestive system?

It shares in the formation of digestive enzymes. Signup and view all the answers

Which scenario is an example of negative feedback?

Elevated CO2 levels causing increased respiration Signup and view all the answers

What triggers the thirst sensation to help control water input?

Increase in plasma osmolarity Signup and view all the answers

Which of the following is NOT a component maintained by homeostasis?

Nutrient storage Signup and view all the answers

What is the typical volume of urine output per day?

1500 ml Signup and view all the answers

How does water contribute to osmotic equilibrium?

By moving through cell membranes easily Signup and view all the answers

In positive feedback mechanisms, what typically occurs?

Response leads to further increases in the stimulus Signup and view all the answers

During labor, which physiological change exemplifies positive feedback?

Increase in cervical dilatation leading to more contractions Signup and view all the answers

What type of feedback mechanism is usually associated with harmful cycles such as heart failure?

Positive feedback Signup and view all the answers

Study Notes

Organization of Human Body

The human body is structured into several hierarchical levels: systems, organs, tissues, and cells.
Cells are the basic units of structure and function, containing a nucleus and organelles, including mitochondria and ribosomes.
The plasma membrane facilitates communication between intracellular and extracellular compartments.

Body Fluids

Body fluids are water-soluble solutions containing carbohydrates, proteins, lipids, nucleic acids, and ions.
Comprise about 65% of body weight (approximately 40-42 liters in a 70 kg adult).
Divided into two compartments:
- Intracellular fluid (ICF): 2/3 of total body fluids, about 25-28 liters.
- Extracellular fluid (ECF): 1/3 of total body fluids, about 14-15 liters.

Extracellular Fluid (ECF)

Serves as the internal environment supplying cells with nutrients.
Composed of:
- Plasma (3-3.5 liters): fluid inside blood vessels.
- Interstitial fluid (10-12 liters): fluid between cells.
- Trans-cellular fluid (1 liter): includes fluids in body cavities like GIT and cerebrospinal fluid.
ECF is rich in sodium, chloride, and bicarbonate ions while ICF has high levels of potassium and phosphate ions.

Measurement of Body Fluid Volumes

Utilizes the dye dilution technique for determining compartment volumes.
Total Body Water (TBW) is measured using deuterium oxide (D2O); distributed in ICF and ECF.
ECF volume is assessed with indicators such as inulin (not entering ICF).
Intracellular fluid volume is calculated by subtracting ECF volume from TBW.
Plasma volume is measured with Evans blue dye or iodine-labeled serum albumin.

Body Water

Maintained at a constant level through regulation of water input/output: 2400 ml/day for both.
Input includes ingested water and metabolism; output includes urine, insensible loss, sweating, and feces.
Factors affecting water percentage: females (50%), males (60%), children (70%), decreases with age and increased fat.

Functions of Body Water

Regulates chemical reactions and body temperature.
Acts as a solvent, aiding in digestion and formation of secretions.
Moistens tissues and lubricates joints, facilitates osmotic equilibrium.
Plays a critical role in filtration, absorption, and excretion across various body systems.

Water Balance

Adjusted via thirst sensation for water intake and urine volume for water loss.
Thirst is stimulated by increased plasma osmolarity or decreased blood volume.
Antidiuretic hormone (ADH) regulates urine volume primarily in response to hypertonicity and hypovolemia.

Homeostasis

Mechanisms that keep internal environments constant across various parameters (water, ions, temperature, glucose, pH, and blood pressure).
Maintained by body systems:
- Nervous system: rapid responses.
- Endocrine system: slower, regulatory actions.
Feedback mechanisms:
- Negative feedback: response counteracts stimulus (e.g., high CO2 leading to increased ventilation).
- Positive feedback: response enhances stimulus (e.g., during labor, increased contractions).

Feedback Mechanisms

Negative: inhibits initial stimulus—regulates physiological variables such as blood pressure and glucose levels.
Positive: amplifies physiological conditions—can be beneficial (e.g., childbirth) or detrimental (e.g., heart failure).

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الامتحان الخاص بالمحاضرة الأولى فسيولوجي - د. الصاوي