Applied Anatomy and Physiology Lecture 1 PDF

MOLECULAR BUILDING BLOCKS OF LIFE: 33 All matter is made up of atoms & molecules - 4 Biological Elements account for 96% of living matter: o Carbon o Oxygen o Hydrogen o Nitrogen 34  These 4 elements combin...

MOLECULAR BUILDING BLOCKS OF LIFE: 33 All matter is made up of atoms & molecules - 4 Biological Elements account for 96% of living matter: o Carbon o Oxygen o Hydrogen o Nitrogen 34  These 4 elements combine to form the 4 major Macromolecules of life: o Carbohydrates (Sugars) o Fats (Polymers of Fatty Acids) o Proteins (Polymers of Amino Acids) o Nucleic Acids (Polymerizes to form DNA & RNA) 35  Most of them are polymers o Made by stringing together many smaller molecules (monomers) o Monomers bond (polymerise) by dehydration reactions and break down by hydrolysis: 36 37 38 CARBOHYDRATES: 39  What Are They? - Biological compounds containing covalently bonded carbon, hydrogen, and oxygen (in a 1:2:1 ratio) General Info About Importance: o Monosaccharides = important cellular Carbohydrates nutrients o Metabolised by cells to produce usable energy o Important store of energy reserves 40  o Monosaccharides = Single-Sugar units: Structural ▪ Glucose Classifications: ▪ Fructose ▪ Galactose 41  Polysaccharides = Multi-Sugar Polymers: ▪ Glycogen ▪ Starch ▪ Cellulose (Plants) 43  - Monosaccharide Literally Means: “single” “Sugar- unit” o Cannot be broken down into simpler sugars - Examples: o Glucose o Fructose Monosaccharides o Galactose (Simple Sugars): - Monosaccharides are Isomers: o Ie: Have the same chemical formulae but different structural arrangements o Still contain exactly the same amount of energy - In aqueous solutions, monosaccharides form rings o Are the main fuel used by cells 44 45  Each Monosaccharide Has Its Own Metabolic Pathway: o Glucose → Glycolysis → ATP o Fructose → Fructolysis → Glycolysis → ATP o Galactose → Leloir Pathway → Glycolysis → ATP o (Note how ALL 3 eventually feed into Glycolysis) 46 Each Monosaccharide Has Its Own Metabolic Pathway: o Glucose → Glycolysis → ATP o Fructose → Fructolysis → Glycolysis → ATP o Galactose → Leloir Pathway → Glycolysis → ATP o (Note how ALL 3 eventually feed into Glycolysis) 47 48  “Double-Sugar Units o Consist of 2 monosaccharides Disaccharides: 3x Digestible Disaccharides: o Maltose: Glucose + Glucose o Lactose: Glucose + Galactose o Sucrose (table sugar): Glucose + Fructose 49 50  Disaccharide Metabolism: o First requires breakdown into constituent Monosaccharides In order for the body to utilise o Requires Specific Enzymes ▪ Sucrase → Hydrolyzes Sucrose into Glucose + Fructose ▪ Lactase → Hydrolyzes Lactose into Glucose + Galactose ▪ Maltase → Hydrolyzes Maltose into Glucose + Glucose 51 52 Polysaccharides: - AKA: Complex Carbohydrates o Long Polymers of Monosaccharides (Single Sugar Units) 53 54  Glycogen Metabolism & Storage In The Body: o Glycogenesis = Creating glycogen from excess glucose following a meal o Glycogenolysis = Tapping into glycogen to liberate glucose in times of fasting 55 56 LIPIDS / FATS: General Info About Lipids/Fats: - What are they? o Biological compounds containing hydrocarbons o Not soluble in water (hydrophobic) o Eg: Fats/waxes/oils/sterols/triglycerides/phospholipids 57  o Major structural component of cell membranes (lipid bilayer) o Major class of chemical messenger (Eg: Steroid hormones) o Major store of energy (triglycerides) o Major source of energy (fatty acids) Importance: o Major solvent for certain vitamins (Vitamins A, D, E & K) o Major functional barriers (Eg: Skin oils, ear wax, cerumen) o Major source of insulation/cushioning of vital organs (Eg: Kidneys and heart) 58 3 Relevant Types: o Fatty Acid: A long hydrocarbon chain with a carboxyl group end ▪ Saturated fatty acids are straight Pack tightly together Solid @ Room Temperature ▪ Unsaturated fatty acids are kinked Pack loosely together Liquid @ Room Temperature o Triglycerides: 3 x fatty acids bonded to a glycerol through dehydration (ester linkage) 59 60 61 PROTEIN General Info About Proteins: - What are they? o Biological polymers of linked amino acid monomers (via a peptide bond) o The most complex and functionally diverse molecules of living organisms 62 63 64  Amino Acids: - Each amino acid consists of: o A central carbon covalently bonded to 4 partners o An amino group o A carboxyl group o A side group (Variable among all 20 amino acid types) - ALL proteins are constructed from Amino Acids o Amino acids join together by dehydration reactions forming peptide bonds: 65 66  There are 20 relevant amino acids o Some are Essential (Either cannot be synthesized at all or cannot be synthesized in sufficient quantities in the body; Therefore, must be consumed in food) o Some are Non-Essential (Body can synthesize them & in sufficient quantity) 67 Protein Shape/Structures: Primary Protein Structure (multiple peptide bonds = polypeptide *chains*) o Written L→R from amino end to carboxylic acid end Secondary Protein Structure Tertiary Protein Structure Quaternary Protein Structure o Complete functional protein 68 69  Proteins as Enzymes: What are Enzymes: o Compounds that Catalyse biological reactions o Almost all enzymes are proteins o Act to Lower the activation energy of a reaction o May contain cofactors (metal ions for vitamins) 70 Most Enzyme Names end in “-ase” o Is specific for the chemical that it reacts § Eg: Sucrase – reacts sucrose § Eg: Lipase – reacts lipids o Describes the function of that enzyme § Eg: Oxidase – catalyses oxidation § Eg: Hydrolase – catalyses hydrolysis 71 72 73 74 75 76 Anatomical Position. Anatomical Position. 77  Anatomical positions are universally accepted as the starting points for positional references to the body. In anatomical position, the subject stands erect and faces the observer; the feet are together, and the arms are hanging at the sides with the palms facing forward. 78 79 80 81 82 83 84 85  ANY QUESTIONS 86  Homeostasis The concept of homeostasis has been of immense value in the study of physiology because it allows diverse regulatory mechanisms to be understood in terms of their “why” as well as their “how.” The concept of homeostasis also provides a major foundation for medical diagnostic procedures. When a particular measurement of the internal environment, such as a blood measurement, deviates significantly from the normal range of values, it can be concluded that homeostasis is not being maintained and that the person is sick. A number of such measurements, combined with clinical observations, may allow the particular defective mechanism to be identified. 87  In order for internal constancy to be maintained, changes in the body must stimulate sensors that can send information to an integrating center. This allows the integrating center to detect changes from a set point. The set point is analogous to the temperature set on a house thermostat. In a similar manner, there is a set point for body temperature, blood glucose concentration, the tension on a tendon, and so on. The integrating center is often a particular region of the brain or spinal cord, but it can also be a group of cells in an endocrine gland. A number of different sensors may send information to a particular integrating center, which can then integrate this information and direct the responses of effectors—generally, muscles or glands. The integrating center may cause increases or decreases in effector action to counter the deviations from the set point and defend homeostasis. 88  If the body temperature exceeds the set point of 37° C, sensors in a part of the brain detect this deviation and, acting via an integrating center (also in the brain), stimulate activities of effectors (including sweat glands) that lower the temperature. For another example, if the blood glucose concentration falls below normal, the effectors act to increase the blood glucose. One can think of the effectors as “defending” the set points against deviations. Because the activity of the effectors is influenced by the effects they produce, and because this regulation is in a reverse, direction, this type of control system is known as a negative feedback loop 89 How it works! The negative feedback mechanism in the human body is a regulatory process that helps maintain homeostasis, or balance, by reversing a change that deviates from a normal state. It operates by detecting deviations from a set point (such as temperature, pH, or hormone levels) and triggering responses that restore the system to its normal condition. Here's a general breakdown of how it works: 90 Components of Negative Feedback 1.Stimulus: A change occurs in the internal environment (e.g., an increase in body temperature). 2.Sensor (Receptor): Specialized sensors detect this change (e.g., thermoreceptors detect a rise in body temperature). 3.Control Center: Information from the sensor is sent to the control center, typically the brain, which processes the information and determines the appropriate response (e.g., the hypothalamus in the brain senses the temperature change). 4.Effector: The control center sends signals to an effector (muscles or glands) to initiate a response to correct the imbalance (e.g., sweat glands are activated to cool the body down). 5.Response: The effector’s action (e.g., sweating) works to reverse the original stimulus, bringing the system back to the desired state. 91 Negative Feedback Loops 92 Antagonistic Effectors Most factors in the internal environment are controlled by several effectors, which often have antagonistic actions. Control by antagonistic effectors is sometimes described as “push-pull,” where the decreasing activity of an antagonistic effector accompanies the increasing activity of one effector. This affords a finer degree of control than could be achieved by simply switching one effector on and off. Eg: Room temperature can be maintained, for example, by simply turning an air conditioner on and off, or by just turning a heater on and off. However, a more stable temperature can be achieved if a thermostat controls the air conditioner and heater. Then the heater is turned on when the air conditioner is turned off, and vice versa. Normal body temperature is maintained at about a set point of 37° C by the antagonistic effects of sweating, shivering, and other mechanisms 93 94  Blood Sugar Regulation Stimulus: Blood sugar levels rise after eating. Receptor: Beta cells in the pancreas detect the increase in blood sugar. Another Control Center: The pancreas releases insulin into the bloodstream. example : Effector: Cells in the liver and muscles take up glucose from the blood. Response: Blood sugar levels decrease back to the normal range. 95  Postive feedback The constancy of the internal environment is maintained by effectors that act to compensate for the change that served as the stimulus for their activation; in short, by negative feedback loops. A thermostat, for example, maintains a constant temperature by increasing heat production when it is cold and decreasing heat production when it is warm. The opposite occurs during positive feedback—in this case: the action of effectors amplifies those changes that stimulate the effectors. For example, a thermostat that works by positive feedback would increase heat production in response to a rise in temperature. 96 Positive feedback Homeostasis must ultimately be maintained by negative rather than by positive feedback mechanisms. However, the effectiveness of some negative feedback loops is increased by positive feedback mechanisms that amplify the actions of a negative feedback response. Blood clotting, for example, occurs as a result of a sequential activation of clotting factors; the activation of one clotting factor results in the activation of many in a positive feedback cascade. In this way, a single change is amplified to produce a blood clot. Formation of the clot, however, can prevent further loss of blood and thus represents the completion of a negative feedback loop that restores homeostasis. 97 Another This occurs when estrogen, secreted by the ovaries, stimulates the women’s pituitary gland to example of secrete LH (luteinising hormone). This stimulatory, positive feedback effect creates an “LH surge” positive (rapid rise in blood LH concentrations) that triggers ovulation. Interestingly, estrogen secretion after ovulation has an inhibitory, negative feedback feedback effect on LH secretion. mechanism, 98 Neural and Endocrine Regulation 99  Two general categories of regulatory mechanisms maintain homeostasis: (1) those that are intrinsic, or “built into” the organs being regulated (such as molecules produced in the walls of blood vessels that cause vessel dilation or constriction); and (2) those that are extrinsic, as in regulating an organ by the nervous and endocrine systems. The endocrine system functions closely with the nervous system in regulating and integrating body processes and maintaining homeostasis. 100  The nervous system controls the secretion of many endocrine glands, and some hormones in turn affect the function of the nervous system. Together, the nervous and endocrine systems regulate the activities of most of the other systems of the body. Regulation by the endocrine system is achieved by the secretion of chemical regulators called hormones into the blood, which carries the hormones to all organs in the body. Only specific organs can respond to a particular hormone, however; these are known as the target organs of that hormone. 101  Nerve fibres are said to innervate the organs that they regulate. When stimulated, these fibres produce electrochemical nerve impulses that are conducted from the origin of the fibre to its terminals in the target organ innervated by the thread. These target organs can be muscles or glands that may function as effectors in maintaining homeostasis. For example, we have negative feedback loops that help maintain homeostasis of arterial blood pressure, in part by adjusting the heart rate. If everything else is equal, blood pressure is lowered by a decreased heart rate and raised by an increased heart rate. This is accomplished by regulating the activity of the autonomic nervous system, as will be discussed later. Thus, a fall in blood pressure— produced daily from lying to standing—is compensated by a faster heart rate (fig). As a consequence of this negative feedback loop, our heart rate varies as we go through our day, speeding up and slowing. 102  Negative feedback control of blood pressure. Blood pressure influences the activity of sensory neurons from the blood pressure receptors (sensors); a rise in pressure increases the firing rate, and a fall in pressure decreases the firing rate of nerve impulses. The blood pressure momentarily falls when a person stands up from a lying-down position. The resulting reduced firing rate of nerve impulses in sensory neurons affects the medulla oblongata of the brain (the integrating centre). This causes the motor nerves to the heart (effector) to increase the heart rate, helping to raise the blood pressure. 103 Feedback Control of Hormone Secretion Hormones are secreted in response to specific chemical stimuli. A rise in the plasma glucose concentration, for example, stimulates insulin secretion from structures in the pancreas known as the pancreatic islets, or islets of Langerhans. Hormones are also secreted in response to nerve stimulation and stimulation by other hormones. The secretion of a hormone can be inhibited by its effects in a negative feedback manner. Insulin, as previously described, produces a lowering of blood glucose. Because a rise in blood glucose stimulates insulin secretion, lowering blood glucose caused by insulin’s action inhibits further insulin secretion. This closed-loop control system is called negative feedback inhibition. 104  Homeostasis of blood glucose is too important—the brain uses blood glucose as its primary energy source—to entrust to the regulation of only one hormone, insulin. So, when blood glucose falls during fasting, several mechanisms prevent it from falling too far. First, insulin secretion decreases, preventing muscle, liver, and adipose cells from taking too much glucose from the blood. Second, the secretion of a hormone antagonistic to insulin, glucagon, increases. Glucagon stimulates processes in the liver that cause it to secrete glucose into the blood. Through these and other antagonistic negative feedback mechanisms, the blood glucose is maintained within a homeostatic range. 105  Negative feedback control of blood glucose. (a) The rise in blood glucose that occurs after eating carbohydrates is corrected by the action of insulin, which is secreted in increasing amounts at that time. (b) During fasting, insulin secretion is inhibited when blood glucose falls, and the secretion of an antagonistic hormone, glucagon, is increased. This stimulates the liver to secrete glucose into the blood, helping to prevent blood glucose from continuing to fall. This way, blood glucose concentrations are maintained within a homeostatic range following eating and fasting. 106 THE PRIMARY TISSUES 107  The body's organs are composed of four primary tissues, each with its characteristic structure and function. The activities and interactions of these tissues determine the physiology of the organs. 108  Although physiology is the study of function, it is difficult to properly understand the body's function without some knowledge of its anatomy, particularly at a microscopic level. Microscopic anatomy constitutes a field of study known as histology. The anatomy and histology of specific organs will be discussed together with their functions. We are going to describe the common “fabric” of all organs. 109 Cells are the basic units of structure and function in the body. Cells that have similar functions are grouped into categories called tissues. The entire body is composed of four major types of tissues. These primary tissues are (1) muscle, (2) nervous, (3) epithelial, and (4) connective tissues. These four primary tissues are grouped into anatomical and functional units called organs. Organs, in turn, may be grouped by common functions into systems. The body systems act in a coordinated fashion to maintain the entire organism. 110  Muscle tissue is specialised for contraction. There are three types of muscle tissue: skeletal, cardiac, and smooth. Muscle Skeletal muscle is often called voluntary muscle because its contraction is consciously controlled. Tissue Both skeletal and cardiac muscles are striated; they have striations, or stripes, extending across the muscle cell’s width. A characteristic arrangement of contractile proteins produces these striations, so skeletal and cardiac muscle have similar contraction mechanisms. Smooth muscle lacks these striations and has a different contraction mechanism. 111 Skeletal Muscle Skeletal muscles are generally attached to bones at both ends by means of tendons; hence, contraction produces skeleton movements. There are exceptions to this pattern, however. The tongue, superior portion of the oesophagus, anal sphincter, and diaphragm are also composed of skeletal muscle, but they do not cause movements of the skeleton. The muscle fibres within a skeletal muscle are arranged in bundles; within these bundles, the fibres extend in parallel from one end to the other. The parallel arrangement of muscle fibres allows each thread to be controlled individually: one can thus contract fewer or more muscle fibres and, in this way, vary the strength of contraction of the whole muscle. The ability to vary, or “grade,” the power of skeletal muscle contraction is needed to control skeletal movements precisely. 112 cardiac muscle Although cardiac muscle is striated, it differs markedly from skeletal muscle in appearance. Cardiac muscle is found only in the heart, where the myocardial cells are short, branched, and intimately interconnected to form a continuous fabric. Particular areas of contact between adjacent cells stain darkly to show intercalated discs characteristic of the heart muscle. The intercalated discs couple myocardial cells together mechanically and electrically. Unlike skeletal muscles, therefore, the heart cannot produce a graded contraction by varying the number of cells stimulated to contract. Because of how the heart is constructed, the stimulation of one myocardial cell stimulates all other cells in the mass and a “wholehearted” contraction. 113 Smooth Muscle As the name implies, smooth muscle cells do not have the striations characteristic of skeletal and cardiac muscle. Smooth muscle is found in the digestive tract, blood vessels, bronchioles (small air passages in the lungs), and the ducts of the urinary and reproductive systems. Circular arrangements of smooth muscle in these organs produce constriction of the lumen (cavity) when the muscle cells contract. The digestive tract also contains longitudinally arranged layers of smooth muscle. The series of wavelike contractions of circular and longitudinal layers of muscle known as peristalsis pushes food from one end of the digestive tract to the other. 114 Nervous Tissue Nervous tissue consists of nerve cells, or neurons, which are specialised for generating and conducting electrical events, and of supporting cells, which provide the neurons with anatomical and functional support. Supporting cells in the nervous system (particularly in the brain and spinal cord) are called neuroglial (or glial) cells. Each neuron consists of three parts: (1) a cell body, (2) dendrites, and (3) an axon. The cell body contains the nucleus and serves as the metabolic centre of the cell. The dendrites (literally, “branches”) are highly branched cytoplasmic extensions of the cell body that receive input from other neurons or receptor cells. The axon is a single cytoplasmic extension of the cell body that can be quite long (up to a few feet long). It is specialised for conducting nerve impulses from the cell body to another neuron or an effector (muscle or gland) cell. 115 Epithelial Tissue Epithelial tissue consists of cells that form membranes, which cover and line the body surfaces, and of glands, which are derived from these membranes. There are two categories of glands. Exocrine glands (from the Greek exo = outside) secrete chemicals through a duct that leads to the outside of a membrane and, thus, to the outside of a body surface. Endocrine glands (from the Greek endon = within) secrete chemicals called hormones into the blood. Epithelial membranes are classified according to the number of layers and the shape of the cells in the upper layer. Epithelial cells that are flattened in shape are squamous; Those that are as wide as they are tall are cuboidal; and those that are taller than they are wide are columnar. Those epithelial membranes that are only one cell layer thick are known as simple membranes; those composed of a number of layers are stratified membranes. 116  Epithelial membranes cover all body surfaces and line every hollow organ's cavity (lumen). Thus, epithelial membranes provide a barrier between the external environment and the body's internal environment. Stratified epithelial membranes are specialised to provide protection. Simple epithelial membranes, in contrast, offer little protection; instead, they are specialised for transporting substances between the internal and external environments. For a substance to get into the body, it must pass through an epithelial membrane, and simple epithelia are specialised for this function. For example, a simple squamous epithelium in the lungs allows oxygen and carbon dioxide to rapidly pass between the air (external environment) and blood (internal environment). As another example, a simple columnar epithelium in the small intestine allows digestion products to pass from the intestinal lumen (external environment) to the blood (internal environment). 117  For today…….any questions 118 119