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Lecture

Homeostasis


Department
Physiology
Course Code
PSL201Y1
Professor
Christopher Perumalla

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Outline
1. Organization of the Body
2. What is physiology?
3. Body plans and body compartments
4. Homeostasis
5. Biomolecules
6. Cell Structure
7. Protein synthesis
1. Organization of the body
-Atoms are the basic building blocks of matter. Practically
everything is made of atoms. Elements consist of only one kind of
atom. Atoms cannot be decomposed to simpler substances. There
are some atomic particles that contains neutrons and protons that
lie in the nucleus of the atom, with electrons spinning around on
organized orbits in the nucleus. All matter is composed of elements,
92 of them. The human body consists of mostly four elements;
carbon, nitrogen, oxygen and hydrogen. Atoms join together to
form molecules. An example of molecules is H2O. Large molecules
or macromolecules are applied to proteins, carbohydrates, fat and
nucleic acids. The next level of complexity is the cell or organelle.
An organelle is a specialized subunit within a cell that has a specific
function. They are separately enclosed, each performing a specific
function within the cell. The cell is the smallest is the smallest
functional unit of all living organisms that carry out all the basic
functions of life. Nothing smaller than a cell is considered being
alive. Cells are grouped together to form tissues which are grouped
together to form organs. Organs are generally composed of two
tissue types. Several organs work together to from an organ
system. For example, the digestive system consists of various
organs such as the stomach, pancreas, liver etc. An organ system is
a group of organs with specific functions such as digestion,
respiration etc. The human body has 11 organ systems. An
organism is a single complete individual.

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-Tissue types: Nerves, muscles, epithelium and the connective
tissues. Nerve tissues transmit information to the body for
communication. They have branches to receive and send
information. Some neurons process information. Muscle cells are
specialized cells with the ability to contract. They are either
voluntary (Example of contraction is the flexing of your forearm-
Skeletal muscle cell) and involuntary (smooth muscle cells in the
stomach used for digestion or cardiac muscle cells in the heart used
to pump blood). Epithelium tissue is a sheet like layer of cells on
the surface of the body, hollow body tubes (blood vessels), organs
etc. They function as a physical barrier or as a transport
membrane. Epithelium glands manufacture a product. Major classes
of glands include exocrine glands which have ducts and endocrine
glands which do not have ducts. They discharge their products
(hormones) in the blood stream. The fourth type of tissue is the
connective tissue which is the most diverse and is characterized by
an extracellular matrix. The connective tissue anchors and links
structures of the body for example bones, tendons, fat and blood
cells.
2.What is physiology?
Physiology is the study of how living organisms function including
areas such as nutrition, movement and reproduction.
3. Body plans and body compartments
The external and internal environment are separated naturally by
an epithelium membrane. The epithelium barrier is continuous.
Examples of external environment include surroundings that are
external to skin, lungs and the air, food and the stomach and urine
in the bladder. Most cells do not have direct exchange with the
external environment. In the diagram, we can see the exchange
between the internal and external environments as well as the
interaction between the external environment and the blood. There
is also interaction between blood and tissue fluids and tissue fluids
with tissue cells. Also shown is the interaction of the blood with the
external environment, lungs and the external environment, external
environment and gastrointestinal system and finally external
environment and kidneys. The figure also depicts mechanisms of
exchange in the gastrointestinal tract which includes secretion and
absorption. There is also exchange of fluid across the kidneys
including the processes of filtration, reabsorption and secretion.

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The body is divided into two major compartments and these
compartments contain fluid. Fluid inside the cell, inside all the cells
in the body is called the intracellular fluid (ICF) and fluid outside
the cells is called the extracellular fluid (ECF). The total of the water
in these two compartments is called the total body water (TBW).
ECF has two sub compartments which are the plasma and the
interstitial fluid (ISF). Plasma is the fluid portion of the blood and
ISF is the fluid present in between the cells throughout the body.
4. Homeostasis
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