Introduction to Physiology and Homeostasis Chapter 1 Physiology Physiology is the study of how living organisms function On the street explanations are in terms of meeting a bodily need Physiologic explanations emphasize how something occurs and how its occurrence contributes to the maintenance of normalcy i.e. the homeostatic condition known as life Assumptions in Physiology The same chemical and physical laws that apply to the inanimate world govern processes in the the living body. The laws describe how an organism lives using information from biology, chemistry, physics, and mathematics Not concerned with that part of life which cannot be explained by science Organization of the Body Levels of organization Chemical An organism is ultimately a set of highly organized, elegantly interacting, organic molecules Molecules composed of atoms Cellular Cells are basic unit of life Cells must perform certain functions to maintain live status Each cell contributes to the continued existence and possible demise of the organism Must obey basic laws of thermodynamics Cells exist at expense of surrounding environment
Organization of the Body (a) Chemical level: a molecule in the membrane that encloses a cell (b) Cellular level: a cell in the stomach lining Levels of organization Cells make up Tissue Tissues make up Organ Organs make up Body system Body systems make up Organism (f) Organism level: the whole body (c) Tissue level: layers of tissue in the stomach wall (d) Organ level: the stomach (e) Body system level: the digestive system Fig. 1-1, p. 3 Basic Functions of Living Cells 1. Obtain nutrients and oxygen from surrounding environment 2. Perform chemical reactions that provide energy for the cell a. Food + O 2 CO 2 + H 2 O + energy 3. Eliminate carbon dioxide and other wastes to surrounding environment 4. Synthesize needed cellular components Basic Functions of Living Cells 4. Control exchange of materials between cell and its surrounding environment 5. Monitor, detect and respond to change surrounding environment 6. Reproduction a. Exception: Nerve cells and muscle cells lose their ability to reproduce during their early development
Specialized Cell Functions Multicellular organisms cells also perform specialized functions that contribute to the life of the organism Specialized functions are modifications of some basic function e.g. Digestive enzymes Basic functions = individual cell survival Specialized functions = survival of organism Tissues Groups of cells with similar structure and specialized function Four primary types of tissues Muscle tissue Nervous tissue Epithelial tissue Connective tissue Tissues Muscle tissue Specialized for contracting which generate tension and produce movement Skeletal muscle Moves the skeleton Cardiac muscle Pumps blood out of the heart Smooth muscle Encloses and controls movement of contents through hollow tubes and organs Tissues Nervous tissue Consists of cells specialized for initiating and transmitting electrical impulses Found in brain, spinal cord, and nerves Epithelial tissue Consists of cells specialized for exchanging materials between the cell and environment Structures: Epithelial sheets & secretory glands
Tissues Connective tissue Connects, supports, and anchors various body parts Distinguished by having relatively few cells dispersed within an abundance of extracellular material Examples: Tendons, bone, blood Organs Two or more types of primary tissues that function together to perform a particular function or functions Example: Stomach Inside of stomach lined with epithelial tissue Wall of stomach contains smooth muscle Nervous tissue in stomach controls muscle contraction and gland secretion Connective tissue binds all the above together Organ: Body structure that integrates different tissues and carries out a specific function Surface epithelium Stomach Duct cell Secretory exocrine gland cell Epithelial tissue: Connective tissue: Muscle tissue: Nervous tissue: Protection, secretion, Structural support Movement Communication, (a) Exocrine gland and absorption coordination, and control Fig. 1-2, p. 4 Fig. 1-3a, p. 4
Surface epithelium Secretory endocrine gland cell Blood vessel Body Systems Groups of organs that perform related functions and interact to accomplish a common activity essential to survival of the whole body Do not act in isolation from one another Human body has 11 systems (b) Endocrine gland Fig. 1-3b, p. 4 Body Systems 1. Circulatory System 2. Digestive System 3. Respiratory System 4. Urinary System 5. Skeletal System 6. Muscular System 7. Integumentary System 8. Immune System 9. Nervous System 10. Endocrine System 11. Reproductive System Circulatory system heart, blood vessels, blood Digestive system: mouth, pharynx, esophagus, stomach, small intestine, large intestine, salivary glands, exocrine pancreas, liver, gallbladder Respiratory system nose, pharynx, larynx, trachea, bronchi, lungs Urinary system kidneys, ureters, urinary bladder, urethra Skeletal system bones, cartilage, joints Muscular system skeletal muscles Fig. 1-4a, p. 6
Homeostasis Integumentary system Immune system skin, hair, nails Nervous system Endocrine system lymph nodes, thymus, brain, spinal cord, all hormone-secreting bone marrow, tonsils, peripheral nerves, tissues, including adenoids, spleen, appendix, and, not shown, white blood cells, gut-associated lymphoid tissue and, not shown, special sense organs hypothalamus, pituitary, thyroid, adrenals, endocrine pancreas, gonads, kidneys, pineal, thymus, and, not shown, parathyroids, intestine, heart, skin, adipose tissue Reproductive system Male: testes, penis, prostate gland, seminal vesicles, bulbourethral glands, and associated ducts Female: ovaries, oviducts, uterus, vagina, breasts Defined as maintenance of a relatively stable internal environment (EXTRACELLULAR FLUID) The internal enviroment is the EXTRACELLULAR FLUID Each cell s activity somehow contributes to maintenance of a relatively stable internal environment Each cell s s activity somehow contributes to upset of internal environment Homeostasis is maintained by multifaceted, interacting, mechanisms In introductory physiology one studies and attempts to learn the mechanisms involved in these multifaceted, interacting control systems s which function to maintain homeostasis In introductory physiology, study is organized by systems for the convenience of the learner In nature the systems interact automatically and in a hierarchy that results in survival of the organism Fig. 1-4b, p. 6 Homeostatic Control Systems In order to maintain homeostasis, control system must be able to Detect deviations from normal in the internal environment that need to be held within narrow limits Integrate this information with other relevant information Make appropriate adjustments in order to restore factor to its desired value