Physiology Chapter 4.2

Basic Physiology Concepts

• The human body is compared to a complex machine, with numerous interrelated working parts that require a source of fuel to operate.
• Anatomy is the scientific study of cells and other body structures, while physiology is the scientific study of how cells and body structures function.

Cells and Tissues

• A cell is the smallest living functional unit in an organism, with approximately 100 trillion cells in the human body.
• Cells can be classified into numerous types, each with a specific function (e.g., muscle cells, red blood cells, white blood cells).
• Cells contain organelles, which are structures that have specific functions (e.g., nucleus, mitochondria, ribosomes).
• The nucleus contains DNA, which provides coded instructions for making proteins.
• Mitochondria generate energy for the cell.
• Ribosomes are involved in the assembly of proteins.
• The cytoplasm is a jelly-like fluid that surrounds the organelles and holds them in place.
• The plasma membrane defines the boundaries of the cell and controls the passage of materials into and out of the cell.

Organization of the Body

• Cells with similar characteristics and functions are joined together into tissues.
• There are four basic types of tissues: epithelial, connective, muscle, and nervous.
• Tissues are organized into organs, which are composed of various tissues that function together.
• Organs are organized into organ systems, which are groups of organs that work together for a similar purpose.

Organ Systems

• The following organ systems are present in the human body:
  • Digestive system: breaks down food into nutrients and absorbs them into the bloodstream.
  • Cardiovascular system: circulates blood throughout the body.
  • Respiratory system: enables the exchange of oxygen and carbon dioxide.
  • Lymphatic/immune system: defends the body against diseases and maintains fluid balance.
  • Urinary system: filters waste products from the blood and maintains fluid balance.
  • Muscular system: enables movement and provides stability.
  • Skeletal system: provides support, movement, and protection.
  • Nervous system: regulates body functions, including thought processes, muscle contractions, and physical responses.
  • Endocrine system: produces hormones that regulate various physiological activities.
  • Integumentary system: protects the body against external damage, regulates body temperature, and aids in the synthesis of vitamin D.
  • Reproductive system: produces children and maintains reproductive health.

Homeostasis

• Homeostasis is the ability of the body to maintain a stable internal environment despite changes in the external environment.
• The body strives to maintain internal conditions, such as body temperature and blood pressure, within specific limits.
• Changes in the cell's internal and external environment can disrupt homeostasis, leading to sickness or even death.
• The body uses various mechanisms to regain homeostasis, including maintaining proper body temperature, acid-base balance, and tissue fluid levels.

COVID-19

• Infection with the coronavirus that causes COVID-19 affects almost every body system, especially the respiratory system.
• Symptoms of COVID-19 include dry cough, fever, fatigue, and shortness of breath.
• The disease can cause serious illness and even death, especially in those with compromised immune systems.