BIOL2012SEF Human Physiology PDF

1 BIOL2012SEF Human Physiology Dr Emily Wong 2 Anatomy The study of structure and form. The word “anatomy” is derived from the Greek word anatome, which means to cut apart or dissect. 3 Physiology The study of how living organisms function. Physiologists are interested in function and integration ▫...

1 BIOL2012SEF Human Physiology Dr Emily Wong 2 Anatomy The study of structure and form. The word “anatomy” is derived from the Greek word anatome, which means to cut apart or dissect. 3 Physiology The study of how living organisms function. Physiologists are interested in function and integration ▫ How different parts of the body work together at various levels of organization as well as the entire organism Relate Physiology to Medicine Disease state ▫ when physiology “goes wrong” ▫  pathophysiology 4 Levels of Organization Cell Tissue Organ System 5 6 Levels of Organization A group of specialized cells with the same function become specific tissue Different kinds of tissues join together to form an organ which usually has specific functions and recognizable shape System is a collection of organs that together perform an overall function 6 7 Cell Basic unit of an organism Organisms can be classified according to the number of cells Unicellular vs multicellular 7 8 Interesting Question How many number of cells is human body made up of? Million? Billion? Trillion? 8 9 Number of cells in Human body 3.72 × 1013 ≈ 37 000 000 000 000 37 trillion If contains 10 billion of cells 37 trillion ≈ x 3700 Reference: Bianconi, E. (2013) Ann Hum Biol, 40(6):463-71 9 10 Basic Cell Structure 10 11 Functions of cell organelles Organelles Main functions Nucleus Storage and transmission of genetic information in the form of DNA Ribosome Protein synthesis 11 12 Organelles Endoplasmic reticulum (ER) Main functions Rough ER: (with ribosomal particles attached to its surface) protein synthesis; distributes protein to other organelles or secretes out of the cell Smooth ER: lipid synthesis; Ca2+ storage Mitochondri a Powerhouse of the cell; energy production in the form of ATP 12 13 Organelles Main functions Golgi Apparatus Concentrates, modifies and sorts protein from rough ER; deliver or secrete protein via Golgi vesicles Lysosome Cellular stomach; breakdown of debris from dead cells or bacteria 13 14 Muscle Cells and Tissue All muscle cells are specialized to generate mechanical force. There are 3 types of muscle cells in the human body: cardiac, skeletal, and smooth. Control of cardiac and smooth muscle is involuntary, while skeletal muscle control is voluntary. 15 Neurons and Nervous Tissue A neuron is a cell of the nervous system that is specialized to initiate, integrate, and conduct electrical signals to other cells, sometimes over long distances. A collection of neurons forms nervous tissue (brain or spinal cord). Cellular extensions from many neurons are packaged together along with connective tissue to form a nerve. 16 Epithelial Cells and Epithelial Tissue (1) Epithelial cells are specialized for the selective secretion and absorption of ions and organic molecules, and for protection. These cells are characterized and named according to their unique shapes, including cuboidal (cube-shaped), columnar (elongated), squamous (flattened), and ciliated. Epithelial tissue (known as an epithelium) may form from any type of epithelial cell. Epithelia may be arranged in single-cell-thick tissue, called a simple epithelium, or a thicker tissue consisting of numerous layers of cells, called a stratified epithelium. The type of epithelium that forms in a given region of the body reflects the function of that particular epithelium. For example, the epithelium that lines the inner surface of the main airway, the trachea, consists of ciliated epithelial cells. 17 Epithelial Cells and Epithelial Tissue (2) Epithelia are located at the surfaces that cover the body or individual organs, and they line the inner surfaces of the tubular and hollow structures within the body. Epithelial cells rest on an extracellular protein layer called the basement membrane. The side of the cell anchored to the basement membrane is called the basolateral side; the opposite side, which typically faces the interior, is called the apical side. A defining feature of many epithelia is that the two sides of all the epithelial cells in the tissue may perform different physiological functions. In addition, the cells are held together along their lateral surfaces by extracellular barriers called tight junctions Tight junctions enable epithelia to form boundaries between body compartments and function as selective barriers regulating the exchange of molecules. 18 Epithelial Cells and Epithelial Tissue 19 Connective Tissue Cells and Connective Tissue Connective-tissue cells connect, anchor, and support the structures of the body. Types of connective tissues include: ▫ ▫ ▫ ▫ ▫ ▫ Loose Connective Dense Connective Blood Bone Cartilage Adipose 20 What Surrounds the Cells? The immediate environment that surrounds each individual cell in the body is the extracellular fluid and extracellular matrix (ECM). ECM consists of a mixture of proteins, polysaccharides, and in some cases, minerals. The ECM serves two general functions: (1) it provides a scaffold for cellular attachments, and (2) it transmits information in the form of chemical messengers to the cells to help regulate their activity, migration, growth, and differentiation. Some proteins of the ECM consist of fibers, rope-like collagen fibers, and rubber band-like elastin fibers; others are a mixture of nonfibrous proteins that contain carbohydrate. 21 22 Organs and Organ Systems Organs are composed of two or more of the four tissue types (for example: blood vessels have layers of smooth muscle cells, endothelial cells and fibroblasts). Organ systems are a collection of organs that together perform an overall function (for example: the urinary system includes the kidney, ureters, bladder, and urethra). Table 1.1 outlines the structural components and primary functions of the major organ systems of the body. Table 1.1 Organ Systems of the Body (1) System Major Organs or Tissues Primary Functions Circulatory Heart, blood vessels, blood Transport of blood throughout the body Digestive Mouth, salivary glands, pharynx, esophagus, stomach, small and large intestines, anus, pancreas, liver, gallbladder Digestion and absorption of nutrients and water; elimination of wastes Endocrine All glands or organs secreting hormones; pancreas, testes, ovaries, hypothalamus, kidneys, pituitary, thyroid, parathyroids, adrenals, stomach, small intestine, liver, adipose tissue, heart, and pineal gland; and endocrine cells in other organs Regulation and coordination of many activities in the body, including growth, metabolism, reproduction, blood pressure, water and electrolyte balance, and others Immune White blood cells and their organs of production Defense against pathogens Integumentary Skin Protection against injury and dehydration; defense against pathogens; regulation of body temperature Lymphatic Lymph vessels, lymph nodes Collection of extracellular fluid for return to blood; participation in immune defenses; absorption of fats from digestive system Table 1.1 Organ Systems of the Body (2) System Major Organs or Tissues Primary Functions Musculoskeletal Cartilage, bone, ligaments, tendons, joints, skeletal muscle Support, protection, and movement of the body; production of blood cells Nervous Brain, spinal cord, peripheral nerves and ganglia, sense organs Regulation and coordination of many activities in the body; detection of and response to changes in the internal and external environments; states of consciousness; learning; memory; emotion; others Reproductive Male: testes, penis, and associated ducts and glands Female: ovaries, fallopian tubes, uterus, vagina, mammary glands Male: production of sperm; transfer of sperm to female Female: production of eggs; provision of a nutritive environment for the developing embryo and fetus; nutrition of the infant Respiratory Nose, pharynx, larynx, trachea, bronchi, lungs Exchange of carbon dioxide and oxygen; regulation of hydrogen ion concentration in the body fluids Urinary Kidneys, ureters, bladder, urethra Regulation of plasma composition through controlled excretion of ions, water, and organic wastes 25 Body Fluid Compartments (1) The term “body fluid,” refers to the watery solution of dissolved substances (oxygen, nutrients, and wastes) present in the body. The fluid in the blood and in spaces surrounding the cells is called extracellular fluid (essentially all fluid outside of cells). Of this, 20 to 25% is in the fluid portion of blood (plasma); the remaining 75 to 80% lies around and between cells and is called the interstitial fluid. The space containing interstitial fluid is called the interstitium. Therefore, the total volume of extracellular fluid is the sum of the plasma and interstitial fluid volumes. 26 Body Fluid Compartments (2) Intracellular fluid is the fluid located inside the cells and accounts for 67% of all the fluid in the body. The composition of the extracellular fluid is very different from that of the intracellular fluid. Maintaining differences in fluid composition across the cell membrane is an important way in which cells regulate their own activity. 27 Fluid Compartments of the Body 28 Homeostasis Most physiological variables such as blood pressure, body temperature, and blood gases, are maintained within a predictable range. Physiological variables can change dramatically over a 24-hour period, but the body is still in overall balance. Homeostasis refers to physiological variables in a state of dynamic constancy; it is not a static process. When homeostasis is maintained, this refers to physiology; when it is not, this refers to pathophysiology. Changes in Blood Glucose Concentration During a Typical 24-Hour Period Blood glucose levels increase after eating, and then levels return to their set point via homeostasis. This is an example of dynamic constancy. Levels change over short periods of time, but remain relatively constant over long periods of time. A Homeostatic Control System Maintains Body Temperature When Room Temperature Decreases *Interpret the arrows in this flow chart as “leads to” or “causes.” (For example, decreased room temperature causes increased heat loss from the body, which leads to a decrease in body temperature, etc.) 31 Control Systems Feedback loops or systems are a common mechanism to control physiological processes. A positive feedback system enhances the production of the product or accelerates a process. E.g. ▫ Immune response ▫ Laboring A negative feedback system brings about responses that move a variable opposite to the direction of its original change. ▫ Regulation of blood glucose by insulin and glucagon ▫ Elevated estrogen and testosterone suppress the release of FSH and LH 32 Please note that due to differing operating systems, some animations will not appear until the presentation is viewed in presentation mode (Slide Show view). You may see blank slides in the “Normal” or “Slide Sorter” views. All animations will appear after viewing in Slide Show mode and playing each animation. Most animations will require the latest version of the Flash Player, which is available at http://get.adobe.com/flashplayer. Negative Feedback “Active product” controls the sequence of chemical reactions by inhibiting the rate-limiting enzyme, “Enzyme A.” 34 Some Important Generalizations About Homeostatic Control Systems Stability of an internal environmental variable is achieved by balancing inputs and outputs. It is not the absolute magnitudes of the inputs and outputs that matter but the balance between them. In negative feedback, a change in the variable being regulated brings about responses that tend to move the variable in the direction opposite the original change – that is, back toward the initial value (set point). Homeostatic control systems cannot maintain complete constancy of any given feature of the internal environment. Therefore, any regulated variable will have a more or less narrow range of normal values depending on the external environmental conditions. The set point of some variables regulated by homeostatic control systems can be reset – that is, physiologically raised or lowered. It is not always possible for homeostatic systems to maintain every variable within a narrow normal range in response to an environmental challenge. There is a hierarchy of importance, so that certain variables may be altered markedly to maintain others within their normal range. 35 Reflexes (1) A reflex is a specific, involuntary, unpremeditated, “built-in” response to a particular stimulus. Example: pulling your hand away from a hot object or shutting your eyes as an object rapidly approaches your face. 36 Reflexes (2) The pathway mediating a reflex is known as the reflex arc. A reflex arc has several components: stimulus, receptor, afferent (incoming) pathway, integrating center, efferent (outgoing) pathway, and effector. A stimulus is defined as a detectable change in the internal or external environment, and a receptor detects the environmental change. The signal travels between the receptor and the integrating center along the afferent pathway. The information going from the integrating center to the effector travels along the efferent pathway. An integrating center often receives signals from many receptors, some of which may respond to quite different types of stimuli. Thus, the output of an integrating center reflects the net effect of the total afferent input; that is, it represents an integration of numerous bits of information. General Components of a Reflex Arc that Functions as a Negative Feedback Control System Reflex for Minimizing the Decrease in Body Temperature that Occurs on Exposure to a Reduced External Environmental Temperature 39 Hormones and Glands Can Be Reflex Components Almost all body cells can act as effectors in homeostatic reflexes. Muscles and glands, however, are the major effectors of biological control systems. Glands may be both a receptor and an integrating center, and they secrete hormones into the blood that act as effectors. A hormone is a type of chemical messenger secreted into the blood by cells of the endocrine system (see Table 1.1). Hormones may act on many different cells simultaneously because they circulate throughout the body. 40 Intercellular Chemical Messengers Hormones are produced in and secreted from endocrine glands or in scattered cells that are distributed throughout another organ. Hormones travel through the blood to their target cells. Neurotransmitters are chemical messengers that are released from the endings of neurons onto other neurons, muscle cells, or gland cells. 41 Chemical Messenger Points of Emphasis A neuron, endocrine gland cell, and other cell types may all secrete the same chemical messenger. In some cases, a particular messenger may function as a neurotransmitter, a hormone, or a paracrine or autocrine substance. Norepinephrine, for example, is not only a neurotransmitter in the brain; it is also produced as a hormone by cells of the adrenal glands. Categories of Chemical Messengers A given chemical messenger can fit into more than one category. For example, the steroid hormone cortisol affects the very cells in which it is made, the nearby cells that produce other hormones, and many distant targets, including muscles and liver. 43 Biological Rhythms Many body functions are associated with rhythmical changes. The most common type is the circadian rhythm, which cycles approximately once every 24 hours. Waking and sleeping, body temperature, hormone concentrations in the blood, the excretion of ions into the urine, and many other functions undergo circadian variation. Circadian Rhythm Body Temperature in a Human Subject with Light On and Off A full analysis of the hormone cortisol requires not only knowledge of the signals that cause its synthesis and secretion, but also consideration of biological rhythms. 45 Relationship Between Biological Rhythms and Homeostasis Biological rhythms add an anticipatory component to homeostatic control systems, and in effect, are a feedforward system operating without detectors. Negative feedback homeostatic responses are corrective responses. They are initiated after the steady state of the individual has been perturbed. Biological rhythms enable homeostatic mechanisms to be utilized immediately and automatically by activating them at times when a challenge is likely to occur but before it actually does occur. Balance of Chemical Substances in the Body Many homeostatic systems regulate the balance between addition and removal of a chemical substance from the body. Two important generalizations concerning the balance concept are: (1) during any period of time, total-body balance depends upon the relative rates of net gain and net loss to the body; and (2) the pool concentration depends not only upon the total amount of the substance in the body, but also upon exchanges of the substance within the body. Three states of total-body balance are possible: Negative balance loss gain Positive balance gain loss Stable balance gain loss Balance Diagram for a Chemical Substance These are some of the potential inputs and outputs that can affect the “pool” of a substance (like glucose), which is a dynamically regulated physiological variable. 48 General Principles of Physiology (1) Homeostasis is essential for health and survival. The functions of organ systems are coordinated with each other. Most physiological functions are controlled by multiple regulatory systems, often working in opposition. Information flow between cells, tissues, and organs is an essential feature of homeostasis and allows for the integration of physiological processes. 49 General Principles of Physiology (2) Controlled exchange of materials occurs between compartments and across cellular membranes. Physiological processes are dictated by the laws of chemistry and physics. Physiological processes require the transfer and balance of matter and energy. Structure is a determinant of - and has coevolved with - function. Clinical Case Study A 64-year-old, fair-skinned man in good overall health spent a very hot, humid summer day gardening in his backyard. After several hours in the sun, he began to feel light-headed and confused as he knelt over his vegetable garden. Although earlier he had been perspiring profusely and appeared flushed, his sweating had eventually stopped. Because he also felt confused and disoriented, he could not recall for how long he had not been perspiring, or even how long it had been since he had taken a drink of water. He called to his wife, who was alarmed to see that his skin had turned a pale-blue color. She asked her husband to come indoors, but he fainted as soon as he tried to stand. The wife called for an ambulance, and the man was taken to a hospital and diagnosed with a condition called heatstroke. What happened to this man that would explain his condition? How does it relate to homeostasis? Sequence of Events in Heatstroke 52 Sequence of Events in Heatstroke Long Description Increased body temperature leads to sweating, deceased body fluid volume and blood pressure, and constriction of skin blood vessels. This causes decreased heat loss and sweating, which leads to the increased body temperature of heatstroke.