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General Physiology

Overview​

General Physiology is a crucial field in medical science, focusing on how living organisms function at molecular, cellular, and systemic levels. It provides the foundation for understanding other branches of medicine, such as pharmacology and pathology.

This chapter covers the following key concepts in general physiology:

  1. Cellular structure and function
  2. Homeostasis and regulation
  3. Energy production and utilization
  4. Nervous system function
  5. Circulatory system function
  6. Respiratory system function
  7. Digestive system function
  8. Endocrine system function

Cellular Structure and Function​

Cells are the building blocks of life, and understanding their structure and function is fundamental to physiology.

Cell Membrane​

The cell membrane, also known as the plasma membrane, is a semi-permeable barrier composed of a lipid bilayer. It regulates the movement of substances in and out of the cell through various mechanisms:

  • Passive transport: Includes diffusion and osmosis, where molecules move from high to low concentration without energy.
  • Active transport: Involves pumping molecules against their concentration gradients, requiring energy in the form of ATP.

Cytoplasm​

The cytoplasm is the fluid-like substance inside the cell membrane, where numerous metabolic reactions take place. It consists of:

  • Organelles: Structures like mitochondria (which produce energy), ribosomes (which synthesize proteins), and lysosomes (which break down waste).
  • Cytosol: The fluid portion in which the organelles are suspended.

Example: Mitochondrial ATP Production​

Mitochondria generate ATP (adenosine triphosphate) through cellular respiration, providing energy for the cell's functions.

Homeostasis and Regulation​

Homeostasis is the process by which living organisms maintain a stable internal environment despite external changes. It involves the regulation of:

  • Body temperature
  • pH levels
  • Blood pressure
  • Glucose concentration

Key systems like the nervous and endocrine systems play a significant role in maintaining homeostasis.

Energy Production and Utilization​

Cells need energy to perform various functions, such as growth, repair, and maintaining homeostasis. The main source of energy is ATP, produced primarily through the breakdown of carbohydrates, fats, and proteins in metabolic pathways.

Nervous System Function​

The nervous system is responsible for transmitting signals between different parts of the body. It includes:

  • Central nervous system (CNS): Comprises the brain and spinal cord, responsible for processing information.
  • Peripheral nervous system (PNS): Consists of nerves that carry signals to and from the CNS.

Circulatory System Function​

The circulatory system transports oxygen, nutrients, and waste products throughout the body. It includes:

  • Heart: Pumps blood.
  • Blood vessels: Arteries, veins, and capillaries that carry blood to and from tissues.

Respiratory System Function​

The respiratory system is responsible for gas exchange, supplying oxygen to the blood and removing carbon dioxide. The main organs include:

  • Lungs
  • Trachea
  • Diaphragm

Digestive System Function​

The digestive system breaks down food into nutrients that the body can absorb and use for energy, growth, and repair. Major components include:

  • Stomach
  • Intestines
  • Liver
  • Pancreas

Endocrine System Function​

The endocrine system regulates physiological processes through hormones secreted by glands such as the thyroid, pancreas, and adrenal glands. These hormones control metabolism, growth, and reproduction.