General Principles of Pathophysiology

I. The Normal Cell

A. General Information 1. The fundamental unit of the human body is the cell. a. Cells are the basic structural unit of all plants and animals. b. Contain all necessary components to carry out basic life functions. 2. Kingdoms of Cells a. Prokaryotes - cells of lower plants and animals. b. Eukaryotes - cells of higher plants and animals.

B. Cell Structure 1. Cell Membrane (also called Plasma Membrane) a. Outer covering that encircles and protects cell. b. Semipermeable (1) Means that it is selectively permeable. (2) Allows only certain substances to pass from one side to another. c. Vital Functions of the Cell Membrane (1) Electrolyte and fluid balance (2) Transfer of enzymes, hormones, and nutrients into and out of the cell. d. Without this membrane, the cell would quickly die. 2. Cytoplasm (also called Protoplasm) a. The thick, viscous fluid that fills and gives shape to the cell. b. Cytosol (1) The clear liquid portion of cytoplasm. (2) Substances dissolved in cytosol are mainly electrolytes, proteins, glucose (sugar), and lipids (fatty substances). 3. Organelles a. The structures that perform specific functions within the cell. b. The most important organelles are: (1) Nucleus (a) Contains DNA i) The genetic material ii) Chromatin – tangles of chromosome filaments containing DNA (b) Also contains enzymes necessary for copying DNA (c) Nucleoli – smaller organelles inside the nucleus (2) Mitochondria (a) The energy factories (powerhouses) of the cells. (b) Convert nutrients into energy i) Usually in the form of ATP (adenosine triphosphate) ii) Energy is stored in ATP C. Cell Functions 1. All cells of the human body have the same general structure and genetic material. 2. Differentiation (also called maturation) - the process of cells becoming specialized 3. The Seven Major Functions of Cells a. Movement – performed by muscle cells. b. Conductivity – performed by nerve cells c. Metabolic Absorption – performed by cells of the intestines and kidneys. d. Secretion – performed by cells of the glands e. Excretion – all cells do this as they break down nutrients and expel wastes. f. Respiration – a function of all cells as they take in oxygen which is used to transform nutrients into energy. g. Reproduction – when cells enlarge, divide, and reproduce. Some cannot.

D. Tissues 1. Groups of cells that perform a similar function. 2. Four Basic Types of Tissues: a. Epithelial (1) Lines internal and external body surfaces. (2) Examples: (a) Skin (b) Mucous membranes (c) Lining of the intestinal tract b. Muscle (1) Cardiac (a) Found only in the heart. (b) Can generate its own electrical impulse and therefore can contract on its own without external stimulation. (2) Smooth (a) Involuntary (not under your conscious control) (b) Found in the intestines and encircling blood vessels. (3) Skeletal (a) Most abundant muscle type. (b) Allows movement of the body. (c) Voluntary (mostly under your conscious control) c. Connective (1) Most abundant tissue in the body. (2) Provides support, connection, and insulation. (3) Examples: (a) Bones and cartilage (b) Fat (c) Blood is sometimes classified as connective tissue. d. Nerve (1) Specialized to transmit electrical impulses. (2) Examples: (a) Brain (b) Spinal Cord (c) Peripheral nerves E. Organs, Organ Systems, and the Organism 1. Organ = a group of tissues functioning together. 2. Organ system = a group of organs working together. 3. Important Organ Systems of the Body a. Cardiovascular b. Respiratory c. Gastrointestinal d. Genitourinary e. Reproductive f. Nervous g. Endocrine h. Lymphatic i. Muscular j. Skeletal 4. Organism = the sum of all cells, tissues, organs, and organ systems. 5. The failure of any component of an organism, from the cellular level to the organ system level, can result in a serious medical emergency.

F. System Integration 1. Homeostasis = the body's natural tendency to maintain a steady internal environment. 2. Metabolism = the building up (anabolism) and breaking down (catabolism) of substances by the body to produce energy. 3. Communication among cells is vital to metabolic processes. a. Chemical signals are sent out via hormones and neurotransmitters. b. These messages are received by receptors. (1) Chemoreceptors (2) Baroreceptors (3) Alpha and beta adrenergic receptors c. When something interferes with the normal sending or receiving of these messages, a disease process can begin or advance. 4. When normal metabolism is disturbed the body attempts to restore normal metabolism (homeostasis). a. Negative feedback loop b. Decompensation 5. Feedback activity of the body’s various systems is orchestrated by two main systems: a. Nervous system response (1) Messages are sent via sensory and motor nerves (2) Response is rapid but short-lived b. Endocrine system response (1) Messages are sent via hormones (2) Response is slower but longer-lasting

G. Pathophysiology 1. Pathology-study of disease and its causes 2. Pathophysiology-study of how diseases alter normal physiology