Dr. Basim Al-Ka'abi
Cellular Physiology
First Lecture
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Lecture Name: Introduction to Cellular Physiology
Lecturer Name: Dr. Basim A. Al-Ka'abi
Department: Medical Physiology
Stage: First Stage Medical Students
Lecture Objectives:
By the end of this lecture students the should be able to know the following:
Meaning of physiology as a science.
The concept of homeostasis.
An introduction to cellular physiology with a simple overview of some
cellular components.
References:
Barrett, K et al. (2018). Ganong's Review of Medical Physiology. Twenty-
sixth edition. USA.
Guyton, A and Hall, J (2015). Text Book of Medical Physiology.
Thirteenth edition. Philadelphia, USA.
Dr. Basim Al-Ka'abi
Cellular Physiology
First Lecture
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Introduction
Definition of physiology: It is the science that study of the function of
living organisms and their parts.
-In human physiology, we are concerned with characteristics of the human
body that allow us to sense our environment, to move about, to think and
communicate, to reproduce and to perform all of the functions that enable
us to survive and thrive as living beings.
Homeostasis
-Is defined as the maintenance of a stable internal environment, so, simply
it means the maintenance of constant conditions in the internal
environment of the body.
-Essentially, all organs and tissues of the body perform functions that help
to maintain these stable conditions.
-The body can be divided into several major functional systems, each of
which performs a particular task in maintaining homeostasis.
Cell Physiology
-The basic living unit of the body is the cell, and each organ is an aggregate
of many different cells held together by intercellular supporting structures.
-Each type of cells is especially adapted to perform one or a few particular
functions.
-Although the many cells of the body often differ markedly from each
other, the general mechanisms for changing nutrients into energy are the
same in all cells, and the cells deliver the products of their chemical
reactions into the surrounding fluids.
-A typical cell, as seen by light microscope have two major parts, which
are the nucleus and cytoplasm.
Dr. Basim Al-Ka'abi
Cellular Physiology
First Lecture
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-The nucleus is separated from the cytoplasm by a nuclear membrane, and
the cytoplasm is separated from the surrounding fluid by a cell membrane.
-Both nucleus and cytoplasm are filled with highly viscous fluid containing
water, proteins, carbohydrates, electrolytes, lipids and other substances.
The water
-The principal fluid medium of the cell is water, which is present in most
cells in a concentration of 70-85%. Many cellular chemicals are dissolved
in the water, whereas others are suspended.
Electrolytes
-The most important electrolytes in the cell are potassium, magnesium,
phosphate, sulfate, bicarbonate and small quantities of sodium, chloride
and calcium. The electrolytes provide inorganic chemical for cellular
reactions.
-Besides, electrolytes acting at the cell membrane allow transmission of
electrochemical impulses in nerve and muscle fibers.
Proteins
-Next to water, the most abundant substance in most cells is proteins, which
normally constitute 10-20% of the cell mass.
-Proteins can be divided into two types, structural proteins that are present
in the cell mainly in the form of long thin filaments and microtubules that
provide the cytoskeleton. The other type is globular proteins, which are
mainly enzymes.
Lipids
-The most important lipids in most cells are phospholipids and cholesterol
which together constitute about 2% of the total cell mass.
Dr. Basim Al-Ka'abi
Cellular Physiology
First Lecture
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-These lipids are mainly insoluble in water and therefore, are used to form
the cell membrane as well as intracellular membranous barriers that
separate the different cell compartments.
-In addition to these lipids, some cells contain large quantities of
triglycerides (neutral fat).
-In fat cells, triglycerides often account for as much as 95% of the cell
mass.
Carbohydrates
-Carbohydrates have little structural function in the cell except as part of
glycoprotein molecules, but they a play a major role in nutrition of the cell.
-Most human cells do not maintain large stores of carbohydrates, usually
averaging about 1% of their total mass but increasing to as much as 3% in
muscle cells and 6% in liver cells.
-Carbohydrate are present as dissolved form such as glucose or as insoluble
form that is stored as glycogen.
The nucleus
-Act as the control center of the cell.
-The nucleus contains large amounts genetic material as deoxyribonucleic
acid (DNA), which determines the characteristics of the cells’ proteins,
including the enzymes of the cytoplasm.
-So, the genes control the structure of the cell through the types of
structural proteins formed, and control the function of the cell mainly
through the types of protein enzymes that are formed.