L1: Functional Organization of The Human Body, Body Fluids and Homeostasis

Question 1

Organization of the human body

Answer 1

 The human body is made up of different systems e.g. digestive system.
 Each system formed of many organs that are formed of many tissues with complementary functions.
 Each tissue formed of millions of cells.
 The cell is the basic unit of structure and function in the body.

Question 2

What are cells considered as?

Answer 2

Cells are the basic unit of structure and function

Question 3

What does plasma or cell membrane allow?

Answer 3

Allow Selective communication between IC & EC compartments.

Question 4

What are the eukaryotic cells formed from?

Answer 4

-plasma or cell membrane: Allow Selective communication between IC & EC compartments.

-organelles: 
 Cytoplasm.
 Nucleus.
 Ribosomes: protein synthesis.
 Mitochondria: energy production.

Question 5

What is the definition of body fluids?

Answer 5

Solutions of water containing:

1. Organic molecules (carbon-containing molecules such as carbohydrates, lipids, proteins, and nucleic acids).
2. Inorganic molecules.
3. Ions (atoms with a net charge).

Question 6

What is the value (amount) of body fluids?

Answer 6

65% i.e. 40-42 liters in an adult weighing 70 Kg.

Question 7

What are the compartments of body fluids?

Answer 7

ICF:
The fluid inside the cell.
2/3 of total body fluids.
25-28 liters.

ECF:
Fluid Outside cell.
1/3 of total body fluids.
14-15 liters.

Question 8

What does ECF consist of?

Answer 8

Plasma: Inside blood vessels - 3 or 3.5 liters
Interstitial fluid: in spaces between cells - 10 or 12 liters
Trans-cellular fluid: in body cavities e.g. GIT & CSF - 1liter

Question 9

What is the composition of body fluids?

Answer 9

 ECF contains large amounts of Na+, Cl-, and HCO3 ions, while ICF contains large amounts of K+, Mg2+, and HPO4 ions.

Question 10

What are the molecules that are more within the cell?

Answer 10

K - proteins - Mg - HPO4

Question 11

What are the molecules with a high ratio in the ECF?

Answer 11

Na - Cl - Ca - HCO3

Question 12

What is the TBW in females, males, children, and elderly people respectively?

Answer 12

50% as their body contains more fat
60%
70% so water loss leads to rapid dehydration.
Down to 40-45%

Question 13

What is the function of body water?

Answer 13

1. It is required for all chemical reactions inside the body.
2. It acts as a powerful solvent that dissolves various substances to make them accessible to the body. So, it acts as a vehicle that carries nutrients and gases to the body cells and removes wastes from them.
3. It is important in the regulation of body temperature as water has a high latent heat of evaporation (each gram H2O needs 0.58 ◦C to evaporate from the body).
4. It moistens tissues such as the mouth, eyes, and nose, and lubricates joints.
5. Digestive function: water shares in the formation of digestive secretions and the action of enzymes.
6. Absorption: at the venous end of capillaries.
7. Filtration: at the arterial end of capillaries.
8. At the kidney: water helps filtration, reabsorption, and secretion.

Question 14

What does the increase in fat do to the ratio of water?

Answer 14

the increasing of the percentage of fat in the body decreases the percentage of water

Question 15

What is the amount of water input?

Answer 15

2400 ml/day.

Question 16

What are the sources of water input?

Answer 16

 Exogenous water :
ingested in form of water or liquid→ 2200 ml/day.

 Endogenous water :
Synthesized as a result of metabolism → 200 ml/day.

Question 17

What is the water input controlled by?

Answer 17

Thirst sensation which caused by stimulation of the thirst center in the hypothalamus.

Question 18

What is the amount of water output?

Answer 18

2400 ml/day.

Question 19

What are the sources of water output?

Answer 19

 Urine → 1500 ml.
 Insensible (vapor & perspiration)→ 700ml.
 Sweating →100 ml.
 Feces → 100ml.

Question 20

What controls the water output?

Answer 20

Adjusting urine volume by antidiuretic hormone (ADH) secreted from the posterior pituitary gland

Question 21

What is homeostasis?

Answer 21

Mechanisms keeping the internal environment constant.

Question 22

What is the importance of homeostasis?

Answer 22

This is very important as the cells lie in the internal environment, This Keeps the normal cellular functions as body water, temperature, blood glucose, ions, pH, and arterial blood pressure (ABP).

Question 23

What are the mechanisms of homeostasis?

Answer 23

A. Negative feedback mechanisms: These mechanisms keep the internal environment constant because the response inhibits the stimulus

B. Positive feedback mechanisms: The response increases the stimulus

Question 24

What are examples of negative feedback mechanisms?

Answer 24

• Increased CO2 (stimulus) → hyperventilation (response) → washout of excess CO2 → decreased CO2 to normal.
• Increased arterial blood pressure (ABP) (stimulus) → reflex VD and decreased heart rate (response) → decreased arterial blood pressure back to normal

Question 25

What are the examples of positive feedback?

Answer 25

• Usually, +ve feedback disturbs homeostasis e.g. death cycles:

In heart failure → decreased cardiac output (stimulus) → decreased arterial blood pressure → decreased coronary blood flow (response) → more heart failure

• Some positive feedback cycles are useful

e.g.
During delivery of baby, cervix dilatation (stimulus) → ↑ uterine contractions→ descent of baby →more cervical dilatation → more uterine contractions (response) → more descent of baby, till complete labor.