A&P Notes PDF

# Introduction The body is composed of many different structures, each with its own specific function. These structures are organized into different levels of complexity, from the simplest atoms and molecules to entire organ systems. ## Levels of Organization 1. **Chemical Level:** The simplest...

# Introduction The body is composed of many different structures, each with its own specific function. These structures are organized into different levels of complexity, from the simplest atoms and molecules to entire organ systems. ## Levels of Organization 1. **Chemical Level:** The simplest level of organization, composed of atoms and molecules. Examples include proteins, lipids, carbohydrates, and nucleic acids. 2. **Cellular Level (Cytology):** When chemicals are joined together in different ways, a cell may be formed. Cells are the basic unit of life, and all organisms are composed of cells. Some organisms are unicellular, while others are multicellular. 3. **Tissue Level (Histology):** A group of similar cells that work together to perform a specific function. Examples include epithelial, connective, muscle, and nervous tissues. 4. **Organ Level:** When different tissues organize and join together, they form an organ. Organs have specific functions and a recognizable shape. Examples include the heart, lungs, skin, and stomach. 5. **Organ System Level:** A group of organs that work together to perform a major function in the body. Examples include the cardiovascular, respiratory, digestive, and nervous systems. > **Note:** When all systems work together to create a functioning individual, it is an organism. ## Homeostasis The body attempts to maintain a constant internal environment despite internal and external disruptions. This state of balance is known as homeostasis. Examples of variables kept in balance include temperature, blood glucose levels, and pH. When homeostasis is disturbed, illness, disease, and even death can occur if the body does not counteract the effects. ### Stress Any disturbance that causes an imbalance within the normally acceptable ranges of homeostasis can be physical, chemical, or emotional. The body will naturally try to compensate for these changes and try to return itself to a normal resting level of homeostasis. ## Control Mechanisms Homeostasis is maintained by feedback loops. Feedback loops keep the body informed of any changes that may be occurring and also return the body to homeostasis. These loops consist of: 1. **Controlled Condition:** The variable that is being regulated (e.g., body temperature, blood glucose level). 2. **Receptor (sensor):** Monitors the controlled condition and detects changes. 3. **Control Center (integrating center):** Processes the information from the receptor and determines the appropriate response. 4. **Effector:** Carries out the response (e.g., muscles contract, glands release hormones). ### Feedback Loops - **Negative Feedback Loop:** The most common type of feedback loop. The response reduces or counteracts the change, restoring the controlled condition back to its original range. For example, when body temperature decreases, the control center signals the effectors to stimulate shivering and vasoconstriction, which raise body temperature. - **Positive Feedback Loop:** The response amplifies or enhances the change. Positive feedback loops are less common in the body and are usually associated with stressful situations. For example, during childbirth, the pressure of the baby's head on the cervix stimulates the release of oxytocin, which further increases uterine contractions. # Connect Regulation _Usually, this is done through the nervous System or the endocrine system (group of glands that secretes hormones)._ ### Negative Feedback - Common > - **Example:** A decrease in blood pressure (BP) is sensed by baroreceptors in the blood vessels, stimulating the heart to beat faster and/or the blood vessels to constrict, raising the BP to normal. ### Positive Feedback - **Example:** The release of oxytocin during labor stimulates uterine contractions, which push the baby towards the cervix, further stimulating oxytocin release, continuing the cycle until the baby is delivered. ## Organization of Organs A collection of organs working together to form a functional organism are known as organ systems. - **Integumentary system** - Protection, senses, and temperature regulation. - **Muscular system** - Movement and heat production. - **Skeletal system** - Protection, support, and mineral storage. - **Nervous system** - Control and regulation of body activities and metabolism. - **Endocrine system** - Regulates the body’s internal environment through the use of hormones. - **Immune system** - Defends the body from infection, recycling interstitial fluid; blood cell production. - **Cardiovascular system** - Carries oxygen and nutrients to body cells and removes waste products. - **Respiratory system** - Gas exchange and regulation of pH. - **Digestive system** - Breaks down food and absorbs nutrients. - **Urinary system** - Rids waste, maintains pH, and regulates body fluid. - **Reproductive system** - Produces gametes (sperm and egg). # Anatomical Planes - **Sagittal plane:** Passes vertically through the body or an organ and divides it into left and right portions. - **Frontal plane:** Extends vertically but is perpendicular to the sagittal plane and divides the body into anterior (front) and posterior (back) portions. - **Transverse plane:** Passes across the body or an organ perpendicular to its long axis and divides the body or organ into superior (upper) and inferior (lower) portions. # Unit 2: Chemistry ## Atoms Atoms are composed of smaller particles: - **Protons:** Located in the nucleus of an atom, they carry a positive charge. - **Neutrons:** Also located in the nucleus, they have no charge. - **Electrons:** Orbit the nucleus and carry a negative charge. Electrons occupy space around the nucleus in an orderly fashion. They are arranged into energy levels called electron shells. Each electron shell has a certain number of electrons it can hold: - The first energy level can hold 2 electrons. - The second energy level holds 8 electrons. - The third energy level holds 18 electrons. **Note:** An atom with 8 electrons in its outer shell (valence shell) is considered chemically stable. This is known as the octet rule. **Reactive Atoms** Atoms that have their outer electron shell unfilled are reactive. They will readily react with other atoms. **Stable Atoms** Atoms with filled outer electron shells are not reactive. ## Terms and Concepts - **Atomic number:** The number of protons in an atom. - **Mass number:** The number of protons and neutrons in an atom. - **Element:** A substance that cannot be divided into different substances. It is composed of only one type of atom. ### Major Elements of the Body - **Four** major elements make up 96% of the body: carbon (C), nitrogen (N), hydrogen (H), and oxygen (O). - **Mineral Elements:** The body also contains several major minerals (Na, Ca, K, Cl, Mg, P). - **Trace Elements:** Present in only small amounts (Fe, I, Zn) ## Chemical Bonds Atoms will react with one another to form chemical bonds. These bonds are formed through the sharing, borrowing, or donating of electrons. This can form molecules or compounds. ### Types of Chemical Bonds - **Ionic bonds:** Formed when one atom gives up an electron to another atom. The atom that donates an electron becomes a positively charged ion (cation), while the atom that accepts an electron becomes a negatively charged ion (anion). These ions attract each other, resulting in an electrostatic force. > - **Example:** Sodium chloride (NaCl). Sodium donates its valence electron to chlorine, creating a sodium cation (Na+) and a chlorine anion (Cl-). These opposite charges attract each other, forming an ionic bond. - **Covalent bonds:** Formed when two or more atoms share electrons. Covalent bonds are stronger than ionic bonds and do not easily dissociate in water. > - **Example:** Water (H2O), Each hydrogen atom shares an electron with the oxygen atom, forming two covalent bonds. - **Hydrogen bonds:** Weak attractive force between hydrogen and either oxygen or nitrogen atoms. Hydrogen bonds are not strong enough to form a molecule, but they are very important for many reasons, such as: * Holding water together * Maintaining the shape of proteins and * DNA * Helping to regulate metabolic reactions. ## Chemical Reactions - **Chemical reactions:** Processes of making and breaking bonds between atoms. Breaking bonds releases energy (catabolism), while forming bonds requires energy (anabolism). - **Metabolism:** The sum of all chemical reactions within a living organism. - **Catabolism:** Breaking down a molecule (releases energy) - **Anabolism:** Building molecules (requires energy) ## Essential Chemical Reactions in Physiology - **Decomposition reaction:** Larger molecules are broken down into smaller molecules (e.g., digestion of food). - **Hydrolysis:** A decomposition reaction that occurs when water is used to break a single molecule down into two smaller ones. - **Synthesis reaction:** Assembles smaller molecules into a larger molecule. - **Dehydration synthesis (condensation):** Occurs when water is removed to form a larger molecule. ## Water and Its Role in the Body Water makes up approximately 60-70% of our body weight and is extremely important in the functioning of the body. Water has several unique properties: 1. **Water is a great solvent:** Many molecules (e.g., sugars, salts, and proteins) will dissolve in water, allowing for transport and chemical reactions. 2. **Water takes part in chemical reactions:** For example, hydrolysis and dehydration synthesis. 3. **Water has a high heat capacity:** This means it takes a lot of energy to heat water, which allows for temperature regulation in the body. > -**Example** The relatively high heat capacity of water helps maintain a stable internal temperature in the body. ### Solutions - **Aqueous solution:** A solution that has water as the solvent. ### Solutes - **Hydrophilic molecules:** Molecules that mix with water (i.e., water-soluble) due to their polar properties (e.g., sugars, salts, and charged amino acids). - **Hydrophobic molecules:** Molecules that do not mix with water (i.e., water-insoluble) due to their nonpolar properties (e.g., fats and oils). ## Acids, Bases, and pH - **Acid**: Any solute that dissociates in solution and releases a hydrogen ion (H+) and an anion. > - **Strong acid**: Dissociates almost completely. >> - **Example**: Hydrochloric acid (HCl) → H+ + Cl- > - **Weak acid**: Dissociates only partially in solution and releases very few H+ ions. >>- **Example:** Carbonic acid (H2CO3) → H+ + HCO3- - **Base**: Any solute that dissociates in solution and releases hydroxide ions (OH-) and a cation. > - **Strong base**: Dissociates almost completely. >>- **Example:** Sodium hydroxide (NaOH) → Na+ + OH- > - **Weak base**: Dissociates only partially in solution and releases very few OH- ions. >>- **Example:** Ammonia (NH3) + H2O → NH4+ + OH- ## The pH Scale The pH scale measures the amount of hydrogen ions (H+) and hydroxide ions (OH-) present in a solution. - **pH 7.0** is neutral. The pH of pure water is 7.0. - **Values below 7.0** indicate an acidic solution: Increased H+ concentration - **Values above 7.0** indicate a basic (alkaline) solution: Decreased H+ concentration. **Note** The pH scale is logarithmic: A pH of 5 is 10 times more acidic than a pH of 6. A pH of 4 is 100 times more acidic than a pH of 6. ## Buffers Buffers are substances that can bind or release hydrogen ions (H+) to help maintain a stable pH within a narrow range. Many buffer systems are used in the body to help regulate pH. ## Unit 3: Organic Compounds Organic compounds are a special class of compounds that always contain carbon. The 4 major macromolecules found in living organisms are: carbohydrates, lipids, proteins, and nucleic acids. ## Carbohydrates Carbohydrates are composed of carbon (C), hydrogen (H), and oxygen (O), typically with a 1:2:1 ratio. They serve as an energy source when bonds are broken. Carbohydrates are not usually stored in large quantities, so they only account for about 1% of body weight. ### Types of Carbohydrates - **Monosaccharides:** Simple sugars, such as glucose, fructose, and galactose. They contain 3 to 7 carbon atoms. - **Glucose** (a hexose) is the most common monosaccharide in the body and serves as the primary metabolic fuel. - **Fructose** (a hexose) and **galactose** (a hexose) are other important monosaccharides. - **Disaccharides:** Two simple sugars joined together by a dehydration synthesis reaction. Examples include sucrose (glucose + fructose), lactose (glucose + galactose), and maltose (glucose + glucose). - Most disaccharides are soluble in water. - **Polysaccharides:** Long chains of monosaccharides and disaccharides linked together. They can branch or be unbranched. - **Starch** is the primary storage form of carbohydrates in plants and is digestible by humans. - **Glycogen** is the storage form of carbohydrates in animals. It is stored primarily in the liver and muscles. - **Cellulose** is a structural polysaccharide found in plant cell walls. Humans cannot digest cellulose (fiber). ## Lipids Lipids are composed of long chains of carbon atoms (hydrocarbon tails) saturated with hydrogen. They are also called fats and contain very little oxygen. Lipids are not soluble in water and serve as energy reserves, insulation, and protection. ### Types of Lipids - **Fatty acids:** Long carbon chains with hydrogen atoms attached. They contain a carboxyl group (COOH) at one end. Fatty acids can be classified as saturated or unsaturated based on the number of hydrogen atoms present. - **Saturated fatty acids:** Contain the maximum number of hydrogen atoms; "saturated" with hydrogen. They are usually solid at room temperature. They are primarily found in animal products (e.g., butter, lard, and bacon fat). - **Unsaturated fatty acids:** Contain fewer hydrogen atoms because they have at least one double or triple bond between carbon atoms. This "kink" in the structure makes unsaturated fats liquid at room temperature. They are primarily found in plant products (e.g., olive oil, canola oil, and vegetable oil). - **Glycerides:** Fatty acids attached to glycerol. - **Monoglycerides** contain one fatty acid attached to glycerol. - **Diglycerides** contain two fatty acids attached to glycerol. - **Triglycerides** contain three fatty acids attached to glycerol. Triglycerides are the most common type of lipid in the body and serve as energy reserves, insulation, and protection. - **Phospholipids:** Contain a phosphate group (PO43-) linked to a diglyceride. The phosphate group is hydrophilic, while the hydrocarbon tails are hydrophobic. This structure makes phospholipids ideal for forming cell membranes, where they create a barrier between the watery interior of the cell and the watery exterior of the cell. >> - **Amphipathic:** Phospholipids are considered amphipathic because they have both a hydrophilic and hydrophobic region. - **Steroids:** Constructed from a cholesterol-based molecule. Cholesterol has four interconnected carbon rings. Steroid examples include the sex hormones estrogen, testosterone, and progesterone, as well as bile salts, which help with the digestion of fats. ## Proteins Proteins are the most abundant organic molecules in the body. They are composed of smaller units called amino acids linked together by peptide bonds. The sequence of amino acids in a protein determines its structure, function, and properties. There are over 200 amino acids identified, but only 20 are essential to humans. Some must be obtained from the diet. ### Functions of Proteins - **Structural proteins:** Provide support and framework to the body (e.g., collagen in connective tissue and keratin in hair, skin, and nails). - **Contractile proteins:** Allow muscle contraction (e.g., actin and myosin). - **Hormonal proteins:** Act as chemical messengers (e.g., insulin, growth hormone, and glucagon). - **Enzymes:** Catalyze (speed up) biochemical reactions in the body (e.g., lactase breaks down lactose, and pepsin digests proteins). - **Antibodies:** Help defend the body against infection by identifying and binding to foreign substances (e.g., viruses, bacteria). - **Transport proteins:** Bind and carry substances throughout the body (e.g., hemoglobin in red blood cells carries oxygen). ### Protein Structure Proteins have different levels of structure: - **Primary structure:** The sequence of amino acids in a protein chain. This is determined by the DNA sequence for the protein. - **Secondary structure:** Folding of the polypeptide chain due to hydrogen bonding between amino acids. This can result in the formation of an alpha-helix (coiled) or a beta-pleated sheet (folded) shape. - **Tertiary structure:** The three-dimensional shape of the protein. It is determined by interactions between amino acids, including hydrogen bonds, ionic bonds, disulfide bridges, and hydrophobic interactions. - **Quaternary structure:** The arrangement of multiple polypeptide chains that form a single functional protein molecule. This structure is only present in proteins that have more than one polypeptide chain. ## Nucleic Acids Nucleic acids are large organic molecules that contain carbon, hydrogen, oxygen, nitrogen, and phosphorous. They are essential for storing and transmitting genetic information. The two types of nucleic acids are: - **Deoxyribonucleic acid (DNA):** Found primarily in the nucleus of cells. It is a double-stranded helix that contains the genetic code for protein synthesis. The genetic code is organized into genes. Each gene is a segment of DNA that codes for a particular protein. - DNA consists of a sugar-phosphate backbone and nitrogenous bases (adenine, thymine, cytosine, and guanine). - **Complementary base pairing:** Adenine pairs with thymine (A=T), and guanine pairs with cytosine (G=C). These hydrogen bonds formed between the nitrogenous bases hold the two strands of DNA together. - **Chromosomes**: DNA is organized into chromosomes, which are thread-like structures that contain genes. - **Ribonucleic acid (RNA):** Found in the nucleus and the cytoplasm of cells. It plays a crucial role in protein synthesis. There are three main types of RNA: - **Messenger RNA (mRNA):** Carries genetic information from DNA in the nucleus to ribosomes in the cytoplasm. Ribosomes are the sites of protein synthesis. - **Transfer RNA (tRNA):** Transports amino acids to ribosomes. - **Ribosomal RNA (rRNA):** Forms part of the structure of ribosomes. ## Unit 5: Glucose Catabolism - **Glucose** obtained from the diet, can be stored in fat cells as triglycerides and as glycogen in the muscles and liver. This glucose can be systemically broken down to release energy, which is stored as ATP. ### Energy Production 1. **Anaerobic Energy Production** - **Does not require O2** - Occurs in the cytoplasm. - **Process:** Glycolysis > - **Overall Reaction:** >>>- **Glucose + 2 ATP → 2 Pyruvate + 4 ATP + 2 NADH + 2 H+** 2. **Aerobic Energy Production** - **Requires O2** - Occurs in the mitochondria. ## Steps in Glucose Catabolism 1. **Glycolysis:** The breakdown of glucose into pyruvate (a 3-carbon molecule) which occurs in the cytoplasm. 2. **Formation of Acetyl Coenzyme A:** Pyruvate is converted into acetyl CoA. This process occurs in the mitochondria, specifically in the mitochondrial matrix. 3. **The Citric Acid Cycle (Krebs Cycle):** A series of enzyme-catalyzed reactions that oxidize acetyl CoA to CO2. The Citric Acid Cycle is a major source of electron carriers, NADH and FADH2, which are critical for the electron transport chain. 4. **Electron Transport Chain:** A series of electron carriers located in the inner mitochondrial membrane. These carriers pass electrons from NADH and FADH2 to oxygen, forming water (H2O). The energy released in this process is used to generate ATP. ### ATP Production The complete oxidation of a glucose molecule yields a total of approximately 38 ATP molecules. ## Anaerobic Glycolysis - When oxygen is not available (such as during strenuous exercise), cells can only generate ATP via anaerobic glycolysis. - **Process:** Pyruvate is converted into lactic acid, which can build up in the muscles during strenuous exercise. - **Cori Cycle:** The process of converting lactic acid back to glucose in the liver. ## Gluconeogenesis - The metabolic process of generating glucose from lactic acid. - Occurs mainly in the liver to maintain blood glucose levels during times of fasting, starvation, or prolonged exercise.