Introduction to Physiology

• Physiology is a biological science studying body functions across different levels of organization, focusing on the functioning of living organisms, including animals, plants, tissues, and cells.
• Originating from the Greek words "Physis" (nature) and "logos" (study), physiology is essentially the study of function.

Levels of Organization

• Atoms are the basic units, such as hydrogen and carbon.
• Molecules, like water and glucose, form from atoms.
• Macromolecules are large molecules including proteins and DNA.
• Organelles, such as nucleus and mitochondria, are structures within cells.
• Cells include muscle cells and are the basic unit of life.
• Tissues, like connective tissues, are groups of similar cells performing specific functions.
• Organs, such as heart and kidneys, are composed of different tissues working together.
• Organ systems, like skeletal and cardiovascular systems, consist of multiple organs collaborating.
• An organism, such as a human or cat, represents the complete living being.

Characteristics of Life

• Reproduction is the process by which organisms create new individuals.
• Growth increases the size or number of cells in an organism.
• Movement involves the ability of an organism to change its position.
• Respiration is the process of energy production at the cellular level.
• Responsiveness enables an organism to react to changes in its environment.
• Digestion breaks down food to produce energy.
• Absorption is the uptake of broken down molecules from the intestinal cavity into the body.
• Circulation involves the transport of substances throughout the body.
• Assimilation is the formation of new compounds from absorbed molecules for cell function.
• Excretion is the removal of waste products from the body.

Body Requirements

• Water is essential for various bodily functions.
• Food provides nutrients and energy.
• Oxygen is necessary for cellular respiration.
• Heat helps maintain body temperature.
• Pressure is needed for certain physiological processes.

Body Fluid

• Intracellular fluid is the fluid inside cells.
• Extracellular fluid is the fluid in the spaces outside the cells.

Removal of Metabolic End Products

• Carbon dioxide get removed by the lungs, representing waste removal.
• Urea, uric acid, and excess water are excreted by kidneys.
• Undigested materials are excreted as feces through the gastrointestinal tract.
• Detoxification of drugs and chemicals occurs via feces, processed by the liver.

Regulation and Protection

• The nervous system regulates body functions.
• The hormonal system regulates body functions.
• The immune system protects the organism.
• The integumentary system (skin) protects the organism.

Digestive System Functions

• Involved in mechanical processing of food.
• Involves chemical digestion.
• Responsible for food absorption.
• Responsible for secretion of water, acids, enzymes, buffers, and salt.
• Responsible for waste excretion.

Nervous System Functions

• It controls the body's internal environment to maintain homeostasis, such as regulating body temperature.
• The nervous system programs spinal cord reflexes, like the stretch reflex.
• Memory and learning are key functions.
• Voluntary control of movement occurs.

Cardiovascular System Functions

• Circulates oxygen and removes carbon dioxide.
• Provides cells with nutrients.
• Removes waste products for disposal.
• Protects against disease and infection.
• Stops bleeding after injury through clotting.

Respiratory System Functions

• Responsible for moving air to and from the lungs exchange surfaces.
• Enables the organism to produce sound.
• Facilitates gas exchange
• Protects.
• Maintains the acid-base balance.
• Facilitates olfactory sense
• Regulates blood volume and blood pressure.

Urinary System Functions

• Removes waste products and medicines.
• Balances body fluids.
• Balances electrolytes like Na+.
• Releases hormones to control blood pressure.
• Releases hormones for red blood cell production.
• Bone health is aided by controlling calcium and phosphorus.

Reproductive System Functions

• The four functions of the reproductive system are producing egg and sperm cells, transporting and sustaining these cells, nurturing developing offspring, and producing hormones.

Skeletal System Functions

• Supports the body.
• Facilitates movement.
• Protects internal organs.
• Produces blood cells.
• Stores and releases minerals and fat.

Muscular System Functions

• Primarily responsible for movement.
• Provides support.
• Offers protection.
• Generates heat.
• Enables speaking and chewing.
• Aids in digestion.
• Maintains blood circulation.

Homeostasis

• Homeostasis is the maintenance of constant conditions in the internal environment.
• Lungs provide oxygen to extracellular fluid.
• Kidneys maintain constant ion concentrations.
• The gastrointestinal system provides nutrients.
• Control systems maintain sodium and hydrogen ion concentrations.

Control Mechanisms

• Regulation of oxygen and carbon dioxide concentration in the extracellular fluid is achieved.
• Arterial blood pressure regulation is achieved.
• Feedback systems return the body to its normal internal state, known as homeostasis.
• Positive feedback systems.
• Negative feedback systems.

Negative Feedback

• Functions to arrest change, and reverse the direction of change
• Also known as balancing feedback
• Example: A high concentration of carbon dioxide in the extracellular fluid increases pulmonary ventilation reducing extracellular carbon dioxide in the body
• If some factors become excessive or deficient, the control system initiates negative feedback to regain homeostasis

Positive Feedback

• Increases the intensity of change in the same direction.
• Blood clotting is a beneficial use.
• Unwanted clots can form resulting in heart attack.
• Childbirth is another example of positive feedback activity.