Human Physiology/Physiology Introduction

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Physiology The word physiology has Greek origin, is the study of how organisms perform their vital functions. An example is the study of how a muscle contract or what kind of forces contracting muscles exert on the skeleton.

Types of human physiology

Human physiology is the study functions of the human body that can be divided into the following types:.

Cell physiology

This is the cornerstone of human physiology; it is the study of the functions of cells.

Special physiology

This is the study of the functions of special organs. For example, renal physiology is the study of kidney function.

Systemic physiology

It includes all aspects of the function of the body systems, such as cardiovascular physiology, respiratory physiology, reproductive physiology etc..

Pathophysiology It is the study of the effects of diseases on organ or system functions (pathos is the Greek word for disease).

Level of organization

Different levels of organization Atom:

An atom is defined as the smallest particle of an element [carbon (C), Hydrogen (H), Oxygen (O), etc.].

Molecule: A molecule is defined as a particle composed of two or more joined atoms (carbon dioxide CO2, water H2O).

Macromolecule: A macromolecule is defined as a large molecule (carbohydrates, lipids, proteins, nucleic acids).

Organelles: An organelle is defined as a small organ of a cell, which performs a particular function (cell membrane, cytoplasm and nucleus)

Cell: The cell is defined as the basic unit of structure and function of living organisms.

Tissue: A tissue is defined as a group of similar cells that performs a specialized function (epithelia, connective, muscle and nervous).

Organ: An organ is defined as a structure consisting of a group of tissues that perform a specialized function (skin, heart, brain, etc…).

System: The system is defined as a group of organs that act together to perform a specialized function. Human body: An organism is the most complex level of organization. It consists of all systems


The seven characteristics of life

1. Cells: All living organisms have cells; cells are the building blocks of life.

2. Metabolism: All living organisms eat, drink, breathe and excrete.

3. Growth: All living organisms take in material from the environment to enlarge.

4. Reproduction: All living organisms are able to produce a copy of themselves.

5. Irritability: All living organisms are able to react to a change in their environment.

6. Adaptation: All living organisms are able to compete with each other for food and space to survive.

7. Movement: All living organisms are able to move.


Cells physiology

Cells are not all the same but all cells share general structures



Cells are organized into three main regions: Nucleus, cytoplasm and plasma membrane.

The nucleus Control center of the cell because it contains genetic material (DNA). It contains three regions: Nuclear membrane, nucleolus and chromatin

Nuclear membrane Nuclear membrane serves as a barrier of nucleus. It consists of a double phospholipid membrane and contains nuclear pores that allow for exchange of material with the rest of the cell. Nucleolus Nucleus contains one or more nucleoli. It functions as sites of ribosome production. Ribosomes then migrate to the cytoplasm through nuclear pores. Chromatin They are composed of DNA and protein scattered throughout the nucleus. Chromatin condenses to form chromosomes when the cell divides. Plasma membrane Barrier for cell contents. It consists of double phospholipid layer and monolayer of protein scattered around phospholipid layer. Other materials in plasma membrane such as cholesterol and glycoproteins.

Cytoplasm It represents the material outside the nucleus and inside the plasma membrane. It consists of Cytosol: Fluid that suspends other elements Organelles: That perform the metabolic activity of the cell

Cytoplasmic organelles

Ribosomes They represent sites of protein synthesis in the cell. They are found at two locations: Free in the cytoplasm and attached to endoplasmic reticulum. Endoplasmic reticulum (ER) Fluid-filled tubules for carrying substances. There are two types of ER Rough endoplasmic reticulum: Carry ribosomes that represent sites where proteins are synthesized Smooth endoplasmic reticulum: Functions in cholesterol synthesis and breakdown, fat metabolism, and detoxification of drugs.

Golgi apparatus Their functions are modified and packaged proteins, secrete vesicles, plasma membrane components and lysosomes.

Lysosomes They contain enzymes that digest nonusable materials within the cell

Peroxisomes Membranous sacs of oxidase enzymes. The detoxify harmful substances and break down free radicals.

Mitochondria They represent powerhouse of the cell. They can change shape continuously. They also carry out reactions where oxygen is used to break down food to provide ATP for cellular activities.

Centrosome The centrosome is composed of two centrioles surrounded by an amorphous mass of protein. Centrosomes are associated with the nuclear membrane during prophase of the cell cycle. In mitosis the nuclear membrane breaks down and the centrosome can interact with the chromosomes to build the mitotic spindles.

Centrioles: Centrioles are self-replicating organelles made up of nine bundles of microtubules. They appear to help in organizing cell division, but aren't essential to the process. Cytoskeleton Network of protein structures that extend throughout the cytoplasm. It provides the cell with an internal framework. Fore example, microfilaments and microtubules.

a-Microfilaments Microfilaments are solid rods made of proteins called actin. These filaments are an important supports of the cytoskeleton.

b-Microtubules These straight, hollow cylinders are found throughout the cytoplasm of all human cells and carry out a variety of functions, ranging from transport to structural support.