Chapter 01 The Study of Body Functions Copyright

What is Physiology? § Study of biological functions of body systems; how the body works • Concerned with the normal function of cells • Emphasizes mechanisms – how it works • Explains using cause and effect sequences • Derived from scientific experiments

Pathophysiology § Study of how diseases or injuries affect physiological processes § Aids understanding of normal processes

Comparative physiology § Studies the differences and similarities in the functions of invertebrates and vertebrates § Has aided in the development of pharmaceutical drugs

The Scientific Method 1. Make observations. 2. Form a hypothesis; the hypothesis must be testable and refutable. 3. Design and conduct experiments or make more observations. 4. Analyze the data. 5. Results must be replicated many times before a conclusion is accepted. 6. Several verified hypotheses may become a general theory.

Measurements, Controls, and Statistics Good physiological research requires: 1) 2) 3) 4) Quantifiable measurements An experimental group and a control group Statistical analysis Review and publication by a peer-reviewed journal

Developing Pharmaceuticals § Research begins by studying the effects of a chemical on cells in vitro (in a culture dish). § Next, studies are done in animals (usually rats and mice) to see if the same effects occur in vivo (in a living creature) and if there any toxic side effects. • • For these trials, many rats and mice are genetically modified to be susceptible to particular diseases. Animal trials may take several years. § Clinical trials

Phases of clinical trials § Phase I clinical trials test the drug on healthy human volunteers to test for side effects, rates of passage, dosage, toxicity, etc. § Phase II clinical trials test its effectiveness on people with the particular disease. § Phase III clinical trials are conducted on a large number of people to include both sexes, many age groups and ethnicities, and people with more than the one health condition. From here the FDA can approve the drug for sale. § Phase IV trials test other applications for the drug.

Brief history of physiology 1. Aristotle – Greece (384 -322 BC) – speculated about body function (thinkers, not doers) 2. William Harvey – England (1578 -1657) – demonstrated that the heart pumps through a closed system of vessels 3. Claude Bernard – France (1813 -1878) – observed that the internal environment (milieu interieur) stays relatively constant although changes are occurring 4. Walter Cannon – US (1932) – coined the term, homeostasis, to describe the internal consistency of the body

Homeostasis 1. Homeostasis is a state of dynamic constancy of the internal environment. 2. The main purpose of our physiological mechanisms is to maintain homeostasis. 3. Deviation from homeostasis indicates disease. 4. Homeostasis is accomplished most often by negative feedback loops.

Homeostasis 1. Main pathway a. Sensors in the body to detect change and send information to the: b. Integrating center, which assesses change around a set point (or range). The integrating center then sends instructions to an: c. Effector, which can make the appropriate adjustments to counter the change back to the set point.

Negative Feedback Loops Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for reproduction or display. 1 1 Sensor X Integrating center X Sensor X Effector Integrating center – – Effector X 2 2 Sensor activated Normal range Effector activated 1 X 2 Time X Normal range 1 Sensor activated 2 Effector activated

Example of negative feedback loops Body temperature a. Sensors in the brain detect deviation from 98. 6ºF (37ºC). Another part of the brain assesses this as actionable, and effectors (sweat glands) are stimulated to cool the body. b. Once the body is cool, sensors alert the integrating center, and sweat glands are inhibited. c. The end result regulates the entire process. Production of the end product shuts off or downregulates the process. This is why it is called a negative feedback loop.

Antagonistic Effectors Homeostasis is often maintained by opposing effectors that move conditions in opposite directions. 1) This maintain conditions within a certain normal range, or dynamic constancy. 2) When you are hot, you sweat; when you are cold, you shiver. These are antagonistic reactions. Other examples – blood glucose levels, blood p. H

Antagonistic Effectors Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for reproduction or display. Set point (average) – – – Normal range Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for reproduction or display. Sweat Normal range 37° C Shiver

Quantitative Measurements Provide a range of values for molecules and ions within the body under normal physiological conditions. A knowledge of normal ranges aids in diagnosing diseases and in assessing the effects of drugs and other treatments in experiments.

Quantitative Measurements

Positive Feedback 1. The end product in a process stimulates the process. 2. The action amplifies the changes that stimulated the effectors 3. Positive feedback could not work alone, but it does contribute to many negative feedback loops. a. For example, if a blood vessel is damaged, a process is begun to form a clot. Once the damage is fixed, clotting ends (negative feedback). However, the process of forming the clot involves positive feedback. b. The strength of uterine contractions during childbirth is also regulated by a positive feedback loop.

Intrinsic and Extrinsic Regulation of processes within organs can occur in two ways: 1. Intrinsically: Cells within the organ sense a change and signal to neighboring cells to respond appropriately. 2. Extrinsically: The brain (or other organs) regulates an organ using the endocrine or nervous system.

Neural and Endocrine Regulation § The nervous system “innervates” organs with nerve fibers. § The endocrine system releases hormones into the blood, which transports them to multiple target organs.

Neural Regulation Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for reproduction or display. Sensor Integrating center Effector Negative feedback response Lying down Standing up 1. Blood pressure falls 4. Rise in blood pressure Stimulus – 3. Heart rate increases 2. Blood pressure receptors respond Effector Motor nerve fibers Medulla oblongata of brain Integrating center Sensory nerve fibers Sensor

Endocrine Regulation – –

Feedback Control of Hormone Secretions Sensor Integrating center Effector Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for reproduction or display. Fasting Eating Blood glucose Pancreatic islets (of Langerhans) – Insulin Glucagon Insulin Cellular uptake of glucose Glucose secretion into blood by liver Cellular uptake of glucose (a) Blood glucose (b) Blood glucose –

The Primary Tissues

Levels of organization 1. Cell – basic unit of structure and function of living things 2. Tissue – group of similar cells that perform a similar function 3. Organ – group of two or more tissues into structural and functional units 4. System – group of organs that work together to perform related functions 5. Organism – systems working together in coordination

The Primary Tissues Our organs are composed of four major categories of tissues: 1. Muscle tissue 2. Nervous tissue 3. Epithelial tissue 4. Connective tissue Each tissue has particular structures and functions that dictate the physiology of the organ.

Muscle Tissue § Specialized for contraction § Three types: 1. Skeletal muscle 2. Cardiac muscle 3. Smooth muscle

Skeletal Muscle Tissue § § § Voluntary muscle (muscle you can consciously control) Most associated with bones that are pulled to produce movements A few do not cause skeletal movement but are under conscious control - tongue, esophagus, sphincters, and diaphragm Has cells organized in striations Fusion of separate cells called myoblasts to form myofibers – a syncytium Can produce a graded response

Skeletal Muscle Tissue Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for reproduction

Cardiac Muscle Tissue § § § Found only in the heart Fibers are short, branched, and interconnected both physically and electrically Striated, but very different in structure and action from skeletal muscle. Involuntary (you can not consciously control) Specialized cell connections called intercalated discs allow passage of ions between cells. Can not produce a graded contraction

Cardiac Muscle Tissue Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for reproduction

Smooth Muscle Tissue § § Found in the walls of digestive, urinary, and reproductive organs, blood vessels, and bronchioles of the lungs (hollow organs) Not striated, involuntary Generally found in layers that run in different directions Peristalsis – coordinated, wave-like contraction of smooth muscle layers to more substances through the organs

Smooth Muscle Tissue Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for reproduction

Nervous Tissue § § § Found in the brain, spinal cord, and nerves Composed of neurons and neuroglia Neurons conduct impulses and have three parts: 1. Dendrites: short, highly branched, cytoplasmic extensions that receive signals 2. Cell body: metabolic center containing the nucleus 3. Axon: long, single extension that sends signal § Neuroglia are supporting cells that do not conduct a nerve impulse but are essential for neuron function

Nervous Tissue Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for reproduction or

Epithelial Tissue § § Forms the membranes that cover body surfaces, line the inside of hollow organs, and glands Epithelial membranes are classified by the number of layers: a. Simple epithelium has one layer and is specialized for transport of substances. b. Stratified epithelium is composed of multiple layers and provides protection.

Epithelial Tissues § § § Epithelial tissues are also classified by the shape of their cells: a. Squamous: flattened cells b. Cuboidal: as tall as they are long c. Columnar: tall cells Put the cell shape together with the number of layers to name epithelial tissue Some modifications can occur such as in columnar tissues that have goblet cells that secrete mucus and cilia that move in a coordinated fashion.

Epithelial Tissues

Simple Epithelial Tissues § Simple squamous epithelium allows for rapid diffusion (ex. alveoli of the lungs) § Simple cuboidal epithelium allows for secretion of substances and lining of simple ducts (in various glands) § Simple columnar epithelium allows for absorption and secretion (ex. intestinal walls)

Simple Epithelial Tissues

Stratified Epithelial Tissue § Multiple layers of similar cells, held together by junctional complexes, to provide protection. 1) Cells are packed too close together to house blood vessels, so are nourished by connective tissues beneath. 2) Epithelial tissues are attached to connective tissues by a basement membrane.

Stratified Epithelial Tissue § Nonkeratinized membranes have living cells in all layers § Keratinized membranes have cells filled with keratin, a water-resistant protein, and layers of dead cells on the surface § Epithelial membranes continually renew by losing surface cells and replacing with new cells

Stratified Epithelial Tissue - Nonkeratinized Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for reproduction or display. Cytoplasm Nucleus Squamous surface cells Mitotically active germinal area Basement membrane Connective tissue (a) (b) a: © Ed Reschke

Stratified Epithelial Tissue - Keratinized Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for reproduction or display. Keratinized layer Epidermis Extracellular material: collagen fibers, scattered cells, tissue fluid Dermis A blood capillary A lymph capillary, which helps drain off tissue fluid The capillary wall– a living, semipermeable membrane

Exocrine Glands § § Derived from epithelial tissues Secretions are transported by ducts. § § § Examples include lacrimal, sweat, and sebaceous glands; digestive enzyme glands; and the prostate. Secretory portions may be tubes or acini groups Sweat glands 1) Eccrine – more numerous; secrete a salty sweat; involved in thermoregulation 2) Apocrine – located in axilla and pubic region; protein-rich sweat that bacteria feed on

Connective Tissues § Characterized by a matrix made up of protein fibers, extracellular material, and specialized cells § There are four major categories: 1. Connective tissue proper 2. Cartilage 3. Bone 4. Blood

Connective Tissue Proper § Composed of protein fibers and a gel-like ground substance § Made from cells called fibroblasts and fibrocytes § Subtypes: 1. Loose: collagen fibers scattered loosely with room for cells, blood vessels and nerves 2. Dense: thick, densely packed collagen fibers with little room for ground substances

Connective Tissue Proper (Loose) Adipose Areolar Extracellular matrix Protein fibers (collagen) Ground substance Mesenchymal cell Elastic fibers Fibroblast (a) Nucleus of adipocyte Fat globule Collagen fibers Reticular fibers Cytoplasm Macrophage Cell membrane (b) Adipocyte (fat cell) Blood vessel

Connective Tissue Proper (Loose) Reticular White blood cells (lymphocytes) Reticular fibers

Connective Tissue Proper Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for reproduction

Connective Tissue Proper Elastic fibers

Cartilage Connective Tissue § § Made from cells called chondroblasts and chondrocytes surrounded by a semi-solid ground substance Serves as a template skeleton during bone development Found in joints to provide a gliding surface for bones Subtypes: 1. Hyaline 2. Elastic 3. Fibrocartilage

Cartilage Connective Tissue Chondrocyte in lacuna Collagen fibers Matrix Fibrocartilage Hyaline Matrix Elastic

Bone § § § Cells called osteoblasts trap mineral salts, forming concentric layers of calcified material around a canal filled with blood vessels and nerves. Once the matrix has hardened, the cells are called osteocytes and live in spaces called lacunae The dentin of a tooth is similar to bone and is made by cells in the pulp; the outer enamel is harder than bone or dentin

Bone Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for reproduction or display. Central canal Osteocyte within a lacuna (a) Lamellae (b) Lamellae Central canal Osteocyte within a lacuna Canaliculi (c) b: © Ed Reschke

IV. Organs and Systems

Organs § § An organ is composed of two or more tissues that serve different functions in the organ. The skin is the largest organ in the body. a. The skin has all four primary tissues. b. Epidermis – keratinized stratified squamous epithelium to protect against water loss and abrasion c. Dermis – dense irregular connective tissue containing exocrine glands, hair follicles, sense receptors, and blood vessels d. Hypodermis – adipose tissue for padding and insulation

Organs – The Skin Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for reproduction or display. Hair Sebaceous gland Sweat pore Stratum corneum Epidermis (Epithelial tissue) Stratum granulosum Stratum spinosum Stratum basale Arrector pili muscle (Muscle tissue) Dermis (Connective tissue) Sweat gland Hypodermis Arteriole Venule Adipose tissue Hair bulb Motor nerve (Nerve tissue) Sensory nerve

Stem cells a. Tissue Development 1) Tissues are composed of highly specialized cells that arise from three embryonic germ layers: a) Endoderm b) Mesoderm c) Ectoderm

Types of Stem Cells § Zygotes are totipotent, which means their cells can become any type of cell. These are true stem cells. § § § As cells begin to differentiate, a few adult stem cells are retained to allow for cell replacement. Adult stem cells are still limited to a narrow range of possibilities but can become several related cells and thus are called multipotent. (Bone marrow cells can become any type of blood cell) Embryonic stem cells are pluripotent – can form any type of unrelated cells

Stem cells in bulge of hair follicle Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for reproduction or display. Hair Epidermis Basal layer Outer root sheath Sebaceous gland Inner root sheath Bulge region with stem cells Matrix Dermal papilla

Systems § Organs that perform related functions are grouped into systems. § Human have 11 inter-related organ systems

Systems

Body Fluid Compartments § Intracellular: area inside the cells; contains 65% of total body water § Extracellular: area outside the cells; examples: blood plasma and interstitial fluid § Both body fluid compartments are filled primarily with water and are separated by membranes.