The document provides an overview of the functional organization of the human body and control of the internal environment. It discusses how the body is organized from cells to tissues to organs to organ systems. The internal environment is regulated through homeostasis, maintained by the nervous and endocrine systems. The nervous system provides rapid responses while the endocrine system provides slower, long-term responses. Overall, this functional organization and control of the internal environment is essential for the body to maintain homeostasis.

1. Chapter no1
Functional Organization of
the Human Body
and Control of the “Internal
Environment”

2. Extracellular Fluid The internal
Environment”
Human Physiology
Cells as the Living Units of the body
Homeostatic” Mechanisms of the
Major Functional System
CONTENTS
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02
03
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3. 01
Functional Organization of
the Human Body
and Control of the “Internal
Environment”

4. The human body is organized into different levels of complexity, from cells to tissues,
organs, organ systems, and the whole organism. Each level has a specific function,
and all levels work together to maintain the body's homeostasis, or internal balance.
At the cellular level, cells perform various functions such as metabolism,
reproduction, and responding to stimuli. Tissues are made up of cells that work
together to perform a specific function, such as muscle tissue, nervous tissue, and
epithelial tissue. Organs are made up of tissues that work together to perform a
specific function, such as the heart, liver, and brain. Organ systems are groups of
organs that work together to perform a specific function, such as the digestive system,
respiratory system, and circulatory system.
The internal environment of the body is regulated by a complex system called
homeostasis. This system maintains the body's internal balance by regulating various
factors such as body temperature, blood pH, and glucose levels. The nervous and
endocrine systems play a crucial role in homeostasis by sensing changes in the
internal environment and sending signals to various organs to respond appropriately.

5. The nervous system is responsible for the body's rapid, short-term responses to changes
in the environment. It consists of the brain, spinal cord, and a network of nerves that
connect to various parts of the body. The endocrine system, on the other hand, is
responsible for the body's slower, long-term responses to changes in the environment. It
consists of various glands that secrete hormones, which travel through the bloodstream
to target organs and tissues.
Overall, the functional organization of the human body and control of the internal
environment are essential for the body to maintain its homeostasis and function properly.

6. 02 Human physiology
Human physiology is the study of the functions and processes that occur within the
human body. It encompasses a wide range of topics, including anatomy, biochemistry,
genetics, neuroscience, and pharmacology, among others. Understanding human
physiology is crucial for understanding how the body works, how it responds to different
stimuli, and how diseases and disorders can affect its function.
Some of the key areas of human physiology include:
Cardiovascular physiology: This involves the study of the heart and the circulatory
system, including how blood is pumped through the body, the regulation of blood
pressure, and the function of blood vessels.
th and well-being.
Respiratory physiology: This involves the study of the lungs and the process of
respiration, including how oxygen and carbon dioxide are exchanged between the lungs
and the blood.

8. Renal physiology: This involves the study of the kidneys and the process of urine
formation, including how the body maintains fluid and electrolyte balance.
Digestive physiology: This involves the study of the digestive system, including how
food is broken down and absorbed by the body.
Endocrine physiology: This involves the study of the endocrine system, including the
role of hormones in regulating various bodily functions.
Neurophysiology: This involves the study of the nervous system, including how nerve
cells communicate with each other and how the brain controls bodily functions.
Reproductive physiology: This involves the study of the reproductive system, including
how hormones and other factors control fertility and reproduction.
Overall, human physiology is a complex and fascinating field that helps us understand
how the human body works and how we can maintain optimal h

9. Extracellular Fluid—The “Internal Environment”
The extracellular fluid (ECF) is the fluid that surrounds and bathes the cells in the
body. It is one of the two main fluid compartments in the body, the other being the
intracellular fluid (ICF), which is the fluid inside the cells. The ECF includes interstitial
fluid, plasma, and lymphatic fluid.
The ECF is essential for the normal functioning of cells and tissues because it provides
them with nutrients, oxygen, and other essential substances. It also helps to remove
waste products and maintain the proper balance of electrolytes and pH levels in the
body.
The ECF is regulated by a complex system called homeostasis, which maintains the
body's internal balance. Homeostasis is achieved through the interplay of various
physiological mechanisms, including the regulation of fluid and electrolyte balance,
blood pressure, and acid-base balance.

10. The kidneys play a critical role in regulating the ECF volume and composition by
filtering blood and removing excess water and electrolytes. The renin-angiotensin-
aldosterone system, which is a hormone system that regulates blood pressure, also
helps to regulate the ECF volume by controlling the retention or excretion of sodium and
water.
Overall, the ECF is an essential component of the body's internal environment, and
maintaining its proper balance is crucial for the body to function properly. Any
disturbance in the ECF volume or composition can lead to various health problems,
such as dehydration, electrolyte imbalances, and acid-base disturbances.

12. Extracellular fluid (ECF) and intracellular fluid (ICF) are two main types of fluid
compartments in the human body. While both fluids are composed mainly of water
and electrolytes, there are some key differences between them:
Location: The main difference between ECF and ICF is their location. ECF is located
outside the cells and surrounds them, while ICF is located inside the cells.
Composition: The composition of ECF and ICF is different. ECF has a higher
concentration of sodium, chloride, and bicarbonate ions, while ICF has a higher
concentration of potassium, magnesium, and phosphate ions.
Volume: ECF and ICF differ in volume. ECF accounts for about one-third of the
body's total water content, while ICF accounts for about two-thirds of the total water
content.

13. Function: ECF and ICF have different functions in the body. ECF provides nutrients
and oxygen to cells and removes waste products, while ICF maintains the proper
environment for the cell's metabolic processes.
Regulation: ECF and ICF are regulated differently. The ECF is regulated by the
kidneys, while the ICF is regulated by the movement of ions across the cell membrane.
Overall, while ECF and ICF have some similarities, they are distinct compartments with
different compositions, functions, and regulatory mechanisms. Maintaining the balance
between these two fluid compartments is essential for the proper functioning of the
body

14. 05 Homeostatic” Mechanisms of theMajor Functional
System
Homeostatic mechanisms are physiological processes that maintain the internal
environment of the body within a narrow range of values, despite changes in external
conditions. The major functional systems in the human body, such as the nervous,
cardiovascular, respiratory, digestive, renal, and endocrine systems, all have
homeostatic mechanisms that ensure the optimal functioning of the body.
Here are some examples of homeostatic mechanisms in each of these systems:
Nervous System: The nervous system maintains homeostasis through various
mechanisms, such as the regulation of body temperature, blood pressure, and heart
rate. For example, when the body temperature rises above normal, the hypothalamus in
the brain triggers sweating to cool the body down.

16. Cardiovascular System: The cardiovascular system maintains homeostasis by
regulating blood pressure, heart rate, and blood volume. When blood pressure drops, for
example, the baroreceptors in the carotid arteries and aortic arch detect the change and
send signals to the brain to increase the heart rate and constrict blood vessels to
increase blood pressure.
Respiratory System: The respiratory system maintains homeostasis by regulating the
levels of oxygen and carbon dioxide in the blood. When carbon dioxide levels rise, the
respiratory center in the brainstem is activated, leading to increased respiratory rate and
depth to eliminate excess carbon dioxide.
Digestive System: The digestive system maintains homeostasis by regulating the
absorption and elimination of nutrients and waste products. For example, the liver plays
a critical role in maintaining glucose homeostasis by releasing glucose into the
bloodstream when levels drop below normal.

17. Renal System: The renal system maintains homeostasis by regulating the balance of
water and electrolytes in the body. The kidneys remove excess water and electrolytes
from the blood and excrete them in urine, while retaining essential substances such as
glucose, amino acids, and electrolytes.
Endocrine System: The endocrine system maintains homeostasis by secreting
hormones that regulate various bodily functions, such as growth and development,
metabolism, and stress response. For example, the pancreas secretes insulin and
glucagon to regulate blood glucose levels.
Overall, these homeostatic mechanisms are essential for maintaining the internal
environment of the body within a narrow range of values and ensuring optimal
functioning of the major functional system

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