Structure and Integrative Functions of the Main Organ Systems

Structure and integrative functions of the main organ systems Respiratory System (BIO) • General function o Gas exchange, thermoregulation ▪ Gas exchange: takes place through passive diffusion. pO2 is high in the lungs and low in the capillaries. Causes O2 to diffuse into the capillaries. pCO2 is low in the lungs but high in the capillaries, so CO2 diffuses into the lungs of exhalation • Ficks Law: rate of diffusion is directly proportional to SA and differential partial pressure across the membrane, inversely proportional to membrane thickness o Protection against disease: particulate matter ▪ Nasal cavity traps dust particles • Nasal hairs and mucus trap dust particles. Cilia move them towards the pharynx, so they can be removed via spitting/swallowing • Structure of lungs and alveoli o Before entering lungs, trachea splits into left and right bronchi. Each bronchi branch to many bronchioles. Bronchioles terminate in alveolar sacs composed of many alveoli ▪ Alveoli are interface for exchange of CO2 and O2. Introduces respired oxygen into blood and gets CO2 from blood for expulsion via exhalation (HIGH SA) • Breathing mechanisms o Diaphragm, rib cage, differential pressure ▪ Inspiration and expiration governed by differential pressures in chest cavity and airway ▪ Inspiration: medulla oblongata signals for diaphragm (thin sheet of skeletal muscle) to contract. Makes pressure in air cavity and alveoli more negative so atmospheric pressure forces air into low pressure areas ▪ Expiration: medulla oblongata stops signaling, diaphragm relaxes o Resiliency and surface tension effects ▪ Resiliency: refers to elasticity of lungs. Increases pressure in lungs, chest cavity, and alveoli, expelling air to the outside atmosphere ▪ Surface tension effects: thin layer of water on inside of alveoli that creates a high surface tension due to H-bonding. Effect is amplified because alveoli has a large SA:V ratio. This exerts collapsing force on the alveolus and opposes lung expansion • Countered by excretion of a surfactant, which breaks up IMFs between water molecules • Thermoregulation: nasal and tracheal capillary beds; evaporation, panting o Panting: increases moisture on lungs, encourages evaporation which cools down body o Capillary beds help to fan out blood over a large SA • Particulate filtration: nasal hairs, mucus/cilia system in lungs • Alveolar gas exchange o Diffusion, differential partial pressures ▪ Passive diffusion of O2 into the blood due to concentration gradient of O2 between alveoli and blood o Henry’s Law (GC) ▪ Concentration of O2 dissolved in blood is directly proportional to partial pressure of O2 in equilibrium with the blood • Higher partial pressure of O2 in alveoli → more O2 dissolved in blood ▪ Greater pressure = greater solubility of gas • pH control o Deoxygenated hemoglobin acts as blood buffer by accepting excess protons from CO2 to bicarbonate reaction o Respiratory system controls pH by adjusting breathing rate • ▪ More breathing = expel more CO2 = increase pH ▪ Less breathing = retain more CO2 = decrease pH Regulation by nervous control o CO2 sensitivity ▪ Central and peripheral chemoreceptors detect CO2 concentrations. The medulla interprets these signals and regulates breathing accordingly • Regulating breathing allows for control of [CO2] Circulatory System (BIO) • Functions: circulation of oxygen, nutrients, hormones, ions and fluids, removal of metabolic waste • Role of thermoregulation o Arterioles and capillaries can regulate heat exchange • Four-chambered heart: structure and function • Endothelial cells • Systolic and diastolic pressure o Systole: when the ventricles contract o Diastole: when entire heart relaxes and then atria contract o Systolic Pressure: Higher blood pressure. Pressure during systole phase o Diastolic Pressure: Lower blood pressure. Pressure when heart relaxes, atria contract • Pulmonary and Systemic circulation o Systemic Circulation: directs oxygenated blood towards tissues and returns deoxygenated blood to heart ▪ 1) Blood from left ventricle of the heart pumped to aorta ▪ 2) Aorta branches into smaller arteries which then branch into smaller arterioles ▪ 3) Arterioles branch into still smaller capillaries which drops O2 off at tissue ▪ 4) Blood from capillaries collected into venules ▪ 5) Venules converge into larger veins ▪ 6) Veins converge into superior and inferior venae cavae ▪ 7) Vena cavae empty into right atrium of the heart o Pulmonary Circulation: directs deoxygenated blood towards lungs and returns oxygenated blood to heart ▪ 1) Deoxygenated blood from right ventricle of the heart pumped to pulmonary arteries • Pulmonary arteries are only arteries which carry deoxygenated blood ▪ 2) Branches into smaller arteries which then branch into smaller arterioles ▪ 3) Arterioles branch into smaller capillaries in lungs which pick up O2 from lungs ▪ 4) Blood from capillaries collected into venules ▪ 5) Venules converge into large veins ▪ 6) Veins converge into the pulmonary veins which lead to the heart ▪ 7) Pulmonary veins empty into left atrium of the heart • Arterial and venous systems (arteries, arterioles, venules, veins) o Structural and functional differences ▪ Functional • Arterial system (arteries, arterioles, capillaries) carry oxygenated blood • Venous system (venules, veins, venae cavae) carry deoxygenated blood • Arteries: pressure store • Arterioles: smaller than arteries but still wrapped in smooth muscle • Capillaries: exchange of materials within tissues • Veins: volume store for blood travelling back to heart, reservoir o Pressure and flow characteristics ▪ Contraction of smooth muscle around arteries and arterioles regulate blood pressure and reroute blood ▪ Pressure is inversely related to cross-sectional area • Capillaries have highest cross-sectional area, arteries lowest ▪ Pouseille’s Law • Shows radius has VERY LARGE EFFECT on blood flow • • • • • Capillary beds o Mechanisms of gas and solute exchange ▪ Capillary walls are only one cell thick. Enable nutrients to cross capillary walls based on differential pressures ▪ 4 methods for crossing capillary walls: • 1) Pinocytosis • 2) Diffusion or transport through capillary cell membranes • 3) Movement through pores (fenestrations) in cells • 4) Movement through space between the cells o Mechanism of heat exchange ▪ Thin walls enable heat exchange with surroundings o Source of peripheral resistance Composition of blood o Plasma, chemicals, blood cells ▪ Erythrocytes (red blood cells): no nucleus or organelles, basically only contain hemoglobin ▪ Leukocytes (white blood cells): contain organelles but not hemoglobin ▪ Albumins: transport fatty acid and steroids, control osmotic pressure • Increase in albumin in blood causes influx of interstitial fluid, increasing blood pressure ▪ Fibrinogen: protein that clots plasma in blood ▪ Most plasma proteins made in the liver o Erythrocyte production and destruction; spleen, bone marrow ▪ RBC’s made from stem cells in bone marrow. Destroyed by being passed through narrow channels in spleen o Regulation of plasma volume ▪ Volume of blood regulated by altering amount of water in plasma Coagulation, clotting mechanisms Oxygen transport by blood • • o Hemoglobin, hematocrit ▪ Hemoglobin: protein which binds O2, allosteric binding, so binding of O2 once increases affinity in future binding ▪ Hematocrit: ratio of volume of RBCs to total volume of blood o Oxygen content o Oxygen affinity ▪ Sigmoidal binding curve (indicates allosteric binding) ▪ The less affinity of O2 for hemoglobin, the GREATER amount of O2 can get to tissues (Hb can let go of O2) – TOW RIGH ▪ 2,3-BPG: decreases affinity of O2 for hemoglobin • Released in high CO2, H+ ion concentrations, or in high T environments ▪ CO2: binding to Hb causes decreased affinity for O2 Carbon dioxide transport and level in blood o Overall path of CO2 transport ▪ 1) CO2 diffuse into red blood cells from tissues ▪ 2) Carbonic anhydrase converts CO2 to bicarbonate ▪ 3) Bicarbonate flows down its concentration gradient from RBC’s into plasma cells ▪ 4) Plasma cells flow to lungs, bicarbonate diffuses back to RBC’s and is converted to CO2 ▪ 5) Process repeats o Exponential binding curve o Increased pCO2 in lungs → increased CO2 in blood → more CO2 bound to hemoglobin o Effect of O2 on CO2 binding ▪ Haldane effect: Oxygenation of Hb causes affinity for CO2 to be lowered. Facilitates transfer of CO2 from blood to lungs (oxygenation of Hb at alveoli causes dissociation of CO2) o 3 ways CO2 is carried to blood: ▪ 1) Dissolved in solution ▪ 2) As bicarbonate By FAR most dominant ▪ 3) Carbamino compounds o Bicarbonate ▪ CO2 and H2O react to make HCO3- and H+ • Reaction catalyzed by carbonic anhydrase ▪ Reaction is in equilibrium, direction depends on concentration of species, which vary based on location • In tissues: CO2 concentration high, so rxn proceeds → • In lungs: pCO2 low, so rxn proceeds ▪ Chloride shift: decreases negative charge in blood by absorbing chloride ions into plasma cells and releasing bicarbonate in turn Nervous and endocrine control o Nervous control of heart contractions ▪ Sinoatrial (SA) node: group of specialized cardiac muscle cells. Contract at regular intervals without PNS input. Contractions propagate via gap junctions. Causes heart contractions. ▪ Atrioventricular (AV) node: Action potential from SA node propagates here. Slower to depolarize than SA node so atria can finish contracting before ventricles being to o Baroreceptor reflex: Nervous regulation of blood pressure, fast ▪ Communicates with SNS or PNS to alter BP by slowing/speeding up contractions ▪ PNS: counteracts increase in BP by slowing contractions ▪ SNS: counteracts decrease in BP by increasing contractions o Renin-anginotension-alderosterone system: Hormonal regulation of blood pressure, slow- acting ▪ Secretion of renin triggers a cascade of enzymatic effects leading to increased intake and retention of water ▪ More water → higher blood volume → higher blood pressure ▪ ADH and aldosterone are involved in this effect Lymphatic System (BIO) • Structure of lymphatic system o Open system ▪ Interstitial fluid gets in by flowing over overlapping endothelial cells. Particles force themselves into cracks between cells. • Cells overlap in such a way that once they’re in, particles can’t get out o Processed fluid drains out of lymph via thoracic duct and right lymphatic duct ▪ Right lymphatic duct drains lymph from right arm and head. Thoracic arm gets rest of body o 2 ways fluid is propelled through lymph: ▪ 1) Smooth muscle around larger lymph vessel walls pushes lymph through ▪ 2) Lymph vessels are squeezed by adjacent skeletal muscle, body movements, arterial pulsations, and compression from objects outside the body • Major functions o Equalization of fluid distribution ▪ Collects excess interstitial fluid that results from fluid exchange in capillary beds and returns it to the blood o Transport of proteins and large glycerides ▪ Removes proteins and large glycerides that are too big to get taken up by capillaries o Production of lymphocytes in immune reactions ▪ Lymph nodes contain lymphocytes which are stimulated to respond to pathogens o Return of materials to the blood ▪ Recycles materials by passing it through lymph nodes, which both filter particles and trigger a potential immune response ▪ Filtered lymph returned to blood Immune System (BIO) • Innate (non-specific) vs. adaptive (specific) immunity o Innate: occurs quickly at the start of an infection, non-specific o Adaptive: slower to occur, specific ▪ Primary response: immune response for first exposure to an antigen, takes about 20 days to reach its full potential ▪ Secondary response: immune response after first exposure to an antigen, takes 5 days to reach its full potential • Adaptive immune system cells o T-lymphocytes: cell-mediated immunity ▪ 4 types: helper T-cells, memory T-cells, suppressor T-cells, killer T-cells • Helper T-cells: activate B and T lymphocytes to make secondary immune response possible • Memory T-cells: recognize a specific antigen during secondary immune response (similar to memory B-cells) • Suppressor T-cells: negative feedback and regulatory role in immune system • Killer T-cells: perforate infected cells to destroy them o Can kill many cells without being destroyed themselves o B-lymphocytes: humoral or antibody-mediated response ▪ • • • • Effective against free-floating pathogens. Can’t act against invading substances within body cells ▪ B-lymphocytes synthesize antibodies • Antibodies can either float freely or attach to B-lymphocytes and become B-cell receptors ▪ Differentiate into plasma cells and memory-B cells during primary response after BCR (B-cell receptor) recognizes appropriate antigen • Plasma cells: synthesize free antibodies • Memory B-cells: immune cells that recognize the specific antigen, remain in blood Innate immune system cells o Phagocytes: earliest responders. Class of cells which eat dangerous substances and destroy them ▪ Macrophages: first responders, can engulf ~100 bacteria at once ▪ Neutrophils: arrive after macrophages, stored in bone marrow until they’re needed. Drawn to infected area by chemicals released by infected tissue or the infection itself. Can engulf ~20 bacteria at once ▪ Monocytes: circulate in blood until they’re needed. Leak out through capillaries. Once they’re in infected tissue, they mature to become macrophages o Pus: fluid made of dead macrophages and neutrophils (which die after engulfing bacteria) Tissues o Bone marrow: synthesize B and T cells, site of clonal selection for B-cells o Spleen: site of lymphatic tissue and B and T cell activation o Thymus: site of maturation and clonal selection for T cells o Lymph nodes: site of activation of B and T cells Concept of antigen and antibody o Antigen: potentially harmful foreign particle o Antibody: particle which can recognize and bind to an antigen ▪ 4 ways an antibody promotes pathogen destruction • 1) Binds to a pathogen, marks it for consumption by macrophages and natural killer cells • 2) Bound antibody may trigger a cascade involving blood proteins which perforate the antibody • 3) Antibodies may cause antigens to stick together or, for toxins, block their chemically active portions • 4) Antibodies may attach their bases to mast cells. These release histamines and other chemicals when the antibody binds to a pathogen Antigen presentation o MHC’s (Major histocompatibility complex (display antigens for recognition o Signal 1 and Signal 2: signals needed for B and T cell action. Both must be present for activation to occur ▪ Signal 1: BCR and TCR recognize its appropriate antigen • T-cells: Signal 1 received from professional APCs. APCs engulf pathogens and display antigen on MHC II’s. • B-cells: Signal 1 received when an antibody binds to multiple BCR’s on the same cell ▪ Signal 2: “danger signal,” received when there’s an actual infection occurring. “Oh shit, this antigen is harmful” • T-cells: Signal 2 provided by activation of innate immune system (ex: increase in circulating cytokines) • B-cells: Signal 2 provided by signals from helper T-cells • • • • • Clonal selection: selects for B and T cells that do their job well o Positive selection: allows T and B cells, which can recognize host MHC’s to survive. Those that can’t undergo apoptosis o Negative selection: lets T and B cells which don’t attack host cells survive. Those that do undergo apoptosis o Opposing processes ensure only good T and B cells are kept Antigen-antibody recognition o Process by which an antibody recognizes a foreign particle o Antigenic determinant: binding portion of antibody, highly specific for a certain pathogen Structure of antibody molecule o Y-shaped, with “variable regions” making up the arms of the Y o Variable regions can bind specifically to antigens, determines specificity o Disulfide bonds hold the antibody together Recognition of self vs. non-self, autoimmune diseases o Failure in negative selection (destroying lymphocytes which attack healthy cells) can cause autoimmune diseases Major histocompatibility complex o Membrane proteins which display antigens for recognition by immune system o 2 classes of MHC’s ▪ MHC I: Display antigens derived from intracellular pathogens (viruses, some bacteria). Endogenous pathway • All nucleated cells have these since all nucleated cells can be attacked by intracellular pathogens ▪ MHC II: Display antigens derived from extracellular pathogens. Exogenous pathway. • Only cells that phagocytose need these, since these pathogens must be phagocytosed to enter the cell • Professional antigen-presenting cells (APCs): Cells that phagocytose extracellular bacteria for the sole purpose of displaying their antigens. WAY TO TAKE ONE FOR THE TEAM. WHAT A HOMIE CELL. o e.g., Macrophages, some B-cells, dendritic cells o Steps for how antigens are processed to be displayed on MHC’s ▪ 1) Antigen uptake: pathogen is either already in the cell (MHC I) or needs to be phagocytosed (MHC II) ▪ 2) Antigen processing: pathogen processed into smaller peptides in cytosol (exogenous) or in vesicles (endogenous) ▪ 3) Peptide-MHC association: antigens associate with MHC in the ER (endogenous) or via fusion with vesicles (exogenous) ▪ 4) Cell surface expression: antigen-MHC complex placed on cell surface for interaction with appropriate immune cells Digestive System (BIO) • Ingestion o Saliva as lubrication and source of enzymes ▪ α-Amylase: breaks down glucose polymers ▪ Saliva lubricates the food in esophagus, helping it move down o Ingestion; esophagus, transport function ▪ Chewing increases SA of food, enabling more enzymatic activity ▪ Bolus: clump of food chewing shapes food into • Bolus is pushed into esophagus ▪ Peristalsis: a contraction of smooth muscle in the digestive tract; moves food down • • • • • Stomach o Main purpose of stomach: to break down macromolecules for absorption in small intestine o Storage and churning of food ▪ Churns food into chyme (semi-fluid mass) o Low pH, gastric juice, mucal protection against self-destruction ▪ Stomach has pH of 2 • Helps denature proteins and kill bacteria ▪ Gastric juice: combination of acid, enzymes, and hormones that maintains low pH ▪ 4 primary secretory cells in the stomach • 1) Mucous cells: secrete mucous to lubricate stomach wall and protect it from acidic environment • 2) Chief cells: secrete pepsinogen (zymogen to pepsin) • 3) Parietal cells: secrete HCl o This lowers pH of stomach, increases pH of blood • 4) G cells: activated to release gastrin, which stimulates parietal cell activity ▪ All secretory cells secrete mucous o Production of digestive enzymes, site of digestion ▪ Produces pepsin to break down proteins • First site of protein breakdown o Structure (gross) ▪ Fundus: can expand to hold gas, excess food ▪ Body: where digestion takes place ▪ Pylorus: prevents undigested food from getting in small intestine Liver o Structural relationship of liver with gastrointestinal system o Production of bile o Role in blood glucose regulation, detoxification ▪ Detoxification • Capillaries in digestive tract feed into the hepatic portal vein • Hepatic portal vein carries blood from digestive system to liver, which screens it for toxins • Now detoxified blood goes to vena cava Bile o Storage in GALL BLADDER o Function: emulsify fats and enable enzymes to access them easier Pancreas o Production of enzymes ▪ Trypsin and chymotrypsin: degrade proteins ▪ Pancreatic amylase: hydrolyzes polysaccharides to tri/disaccharides ▪ Lipase: degrades fats o Transport of enzymes to small intestine ▪ Gall bladder: stores bile and transports it to the small intestine by funneling it through the cystic duct, the common bile duct, and then the pancreatic duct • Bile: emulsifies fat, increasing their SA so they can be digested Small intestine o Absorption of food molecules and water ▪ Duodenum performs chemical digestion of chime in preparation for absorption ▪ Jejunum and ileum absorb food and water ▪ Lacteals and capillary network of villi uptake fats and other macromolecules • Lacteals uptake fats into the lymph • • • • • Capillary network uptake fats into blood o Function and structure of villi ▪ Structure • Line walls of small intestine • Contain a capillary network and a lymph vessel (Lacteal) • Microvilli: smaller villi which project off of villi, increase SA even more o Brush border: fuzzy appearance of villi due to thousands of microvilli, contains many digestive enzymes which break down food into their constituent parts ▪ Function • Increases SA of small intestine • Absorb fats and nutrients o Production of enzymes, site of digestion ▪ Sites of digestion • Pancreas produces digestive enzymes which break down food in lumen of small intestine • Clumps of broken down food broken down to smallest parts by enzymes in brush border ▪ Production of enzymes • Pancreas aids in production of digestive enzymes since small intestine is so specialized in absorption o Neutralization of stomach acid ▪ Stomach acid is neutralized in the duodenum by bicarbonate (which is released by the pancreas) ▪ pH of the duodenum is 6 o Structure (anatomic subdivisions) ▪ Duodenum, jejunum, ileum • Duodenum digests food • Jejunum and ileum absorb food Large intestine o Absorption of water ▪ Primary purpose of large intestine is reabsorption of water and electrolytes o Bacterial flora ▪ Large intestine contains bacterial flora which produce vitamins from partially digested food o Structure (gross) ▪ Ascending colon ▪ Transcending colon ▪ Descending colon ▪ Sigmoid colon ▪ Rectum Rectum: storage and elimination of waste, feces o Rectum stores feces until it is eliminated through the anus Muscular control o Peristalsis: contraction of digestive tract muscles that pushes food down Endocrine control o Hormones ▪ Gastrin: increases HCl production when stomach is full, released in stomach ▪ Secretin: regulates pH, signals for the pancreas to release bicarbonate and enzymes after chyme gets to small intestine, released in duodenum ▪ • Gastric inhibitory polypeptide: released in response to fat and protein digestion in duodenum, decreases motor activity of stomach and stimulates pancreatic enzyme activity ▪ Cholecystokinin: released in response to fat and causes gallbladder contraction and pancreatic enzyme secretion, released in duodenum o Target tissues ▪ Brain stimulates the stomach, which signals the small intestine, which signals the pancreas Nervous control: the enteric nervous system o Enteric nervous system: network of neurons around digestive organs, help to regulate digestive processes Excretory System (BIO) • Roles in homeostasis o Blood pressure o Osmoregulation o Acid-Base balance o Removal of soluble nitrogenous waste • Kidney structure o Cortex ▪ Outer portion of kidney o Medulla ▪ Inner portion of kidney • Nephron structure o Glomerulus ▪ Capillary bed surrounding Bowman’s Capsule o Bowman’s Capsule ▪ Fenestrations: a filter for blood, screens out blood cells and large protein • Blood from capillary bed pushed through fenestrations via hydrostatic pressure ▪ Arterioles: supply blood to glomerulus and take it away • Afferent arteriole: supplies blood to glomerulus, constriction decreases blood flow and hydrostatic pressure, decreasing filtration • Efferent arteriole: takes blood away from glomerulus, constriction increases hydrostatic pressure, increasing filtration o Proximal Tubule ▪ Secretion • Toxins, drugs, solutes secreted into filtrate by specialized cells • Hydrogen ions secreted via an antiport system driven by the sodium concentration gradient ▪ Reabsorption • Valuable nutrients that were accidentally filtered out are reabsorbed back into the Proximal Tubule via passive or active transport o Loop of Henle ▪ Descending Loop of Henle • Low permeability to salt, high permeability to water • Causes filtrate osmolarity to increase ▪ Ascending Loop of Henle • High permeability to salt, low permeability to water • Causes filtrate osmolarity to decrease o Distal Tubule ▪ • • • Secretion • Secretes K, H, and HCO3 into filtrate ▪ Reabsorption • Reabsorbs Na and Ca2+ into cortex ▪ Net effect is to lower filtrate osmolarity ▪ Collecting tubule • Acted upon by ADH to allow for water reabsorption • Not the same as the collecting duct o Collecting duct ▪ Carries filtrate back into medulla ▪ Acted upon by ADH • ADH = always digging holes, pokes holes in collecting duct to drain it Formation of urine o Glomerular filtration ▪ Blood passed through fenestrations in glomerulus, filters out blood cells and large proteins, leaving plasma o Secretion and reabsorption of solutes ▪ Aldosterone • Reabsorbs sodium in distal tubule back into blood • Ultimately causes more water to flow into blood, increasing blood pressure without changing blood osmolarity ▪ Juxtaglomerular apparatus • Monitors filtrate pressure in the distal tubule • Secretes renin when filtrate pressure is too low o Renin increases blood pressure o Concentration of urine o Counter-current multiplier mechanism ▪ How the kidney can constantly move fluid through itself ▪ Steps • 1) Single effect causes filtrate concentration to decrease and medulla solute concentration to increase • 2) Increase in medulla solute concentration causes water in descending loop to flow into medulla to equilibrate • 3) Dilute filtrate in ascending limb gets pushed out of loop, concentrated filtrate in descending limb gets shifted towards the bottom hairpin turn ▪ Takeaways • Active transport is necessary to establish a solute concentration in the medulla • The medulla’s high solute concentration helps to reabsorb water into the body and concentration urine Storage and elimination: ureter, bladder, urethra o Urine produced in kidney, emptied into renal pelvis o Renal pelvis is emptied by the ureter o Ureter carries urine to the bladder o Relaxation of urinary sphincter empties urine out of bladder into urethra Osmoregulation: capillary reabsorption of H2O, amino acids, glucose, ions o Single effect ▪ Process in ascending Loop of Henle where active transport of solutes from filtrate into medulla establishes a solute gradient • Concentration of solute is higher outside the tubule than inside the tubule ▪ Dilutes filtrate and concentrates the medulla in the ascending limb and concentrates • filtrate in the descending limb Muscular control: sphincter muscle o Relaxation of urinary sphincter in bladder allows for urination Reproductive System (BIO) • Male and female reproductive structures and their functions o Gonads o Genitalia o Differences between male and female structures • Hormonal control of reproduction o Male and female sexual development o Female reproductive cycle o Pregnancy, parturition, lactation o Integration with nervous control Muscle System (BIO) • Important functions o Support: mobility o Peripheral circulatory assistance o Thermoregulation (shivering reflex) • Structure of three basic muscle types: striated, smooth, cardiac o Striated ▪ Connects one bone to another via two points: origin and insertion • Origin: a muscle’s attachment around the midpoint of a larger, stationary bone • Insertion: a muscle’s other attachment to the end of a smaller bone that moves relative to the origin bone ▪ Functions • Two major functions are movement and stabilization of body position • Peripheral circulatory assistance: contractions help to squeeze blood and lymph • Thermoregulation: shivering reflex is the rapid contraction of skeletal muscle, controlled by the hypothalamus ▪ Lever arm • When you pick something up, muscle insertion is between the joint and the object • Takes more force than the weight of the object to pull the object up (object is farther from the joint than the insertion) o This allows for more control over the movement and a less bulky body ▪ Contain multiple nuclei ▪ Striated = composed of sarcomeres o Cardiac ▪ Forms a net around the heart that contracts in upon itself • Not connected to bone ▪ Intercalated discs • Discs separating cardiac muscle cells • Contain gap junctions that allow for quick propagation of AP’s ▪ Cardiac muscle is striated too (composed of sarcomeres) ▪ Innervation • Sympathetic innervation increases heart rate • Parasympathetic innervation via the vagus nerve decreases the heart rate ▪ One nucleus o Smooth ▪ • • Two types • Single-unit: gap junctions between single unit muscle allows for fast propagation of electric signal. This enables single-unit smooth muscle fibers to act in a coordinated manner o Found in smaller arteries and veins, digestive tract • Multi-unit: each muscle fiber is directly attached to a neuron. This enables fibers to act independently of other fibers in the same area o Found in large arteries and respiratory system ▪ No sarcomeres ▪ Intermediate filaments • Attached to dense bodies o Similar to Z-lines. Contraction of thick and thin filaments cause intermediate filaments to pull dense bodies together ▪ One nucleus Muscle structure and control of contraction o T-tubule system ▪ T-tubule: divots in the sarcolemma which allow for AP to propagate quickly along a muscle fiber o Contractile apparatus ▪ Sarcomere: smallest functional unit of the contractile apparatus, made up of thin and thick filaments ▪ Muscle fiber: bundle of sarcomeres ▪ Fasciculus: bundles of muscle fibers ▪ Muscle: bundles of fasciculi o Sarcoplasmic reticulum ▪ Myofibril: sarcomeres positioned end to end, many mitochondria are wedged b/w the myofibrils in a muscle fiber ▪ Sarcoplasmic reticulum: specialized endoplasmic reticulum of muscle cells, surrounds myofibrils ▪ Sarcolemma: modified plasma membrane that wraps around many myofibrils to make a muscle fiber ▪ Muscle fiber: sarcolemma wrapped around many myofibrils and the sarcoplasmic reticulum ▪ Fasciculus: many muscle fibers bound together ▪ Muscle: composed of many fasciculi bound together o Fiber type ▪ Type I (slow twitch): red colored (b/c contains lots of myoglobin for oxygen storage), has a slow contractile velocity and produces a small amount of force but has a high resistance to fatigue and uses aerobic metabolism for energy ▪ Type II A (fast twitch): red colored (lots of myoglobin), has a fast-contractile velocity and produces high force but not as resistant to fatigue as type I fibers, uses long-term anaerobic metabolism for energy ▪ Type II B (fast twitch): white colored (little myoglobin, lots of glycogen), has a very fast contractile velocity and very high force production but fatigues very easily, uses short-term anaerobic metabolism for energy o Contractile velocity of different muscle types ▪ Contractile velocity in ascending order for muscle fibers • Type I < Type II A < Type II B Regulation of cardiac muscle contraction o Plateau after depolarization ▪ Cardiac muscle is slow to repolarize • Plateau not seen in neuronal action potentials (repolarization is quick) Slow voltage-gated calcium channels allow Ca2+ to enter and stay in the membrane, maintaining depolarization ▪ Purpose: lengthens time of contraction to give heart enough time to refill with blood • Plateau is critical in allowing the heart to work as a pump Oxygen debt: fatigue o Oxygen debt: when the body needs excess oxygen after exercise to metabolize the lactic acid produced from anaerobic glycolysis Nervous control o Motor neurons ▪ Attaches to the motor end plate, releases acetylcholine once excited • Note: only striated muscle uses acetylcholine (skeletal and cardiac) ▪ Motor unit: a motor neuron and all the muscle fibers it innervates • Motor units vary in size • Small motor units activated first, and larger ones activated as needed to create smooth movements ▪ Acetylcholine • Excites skeletal muscle, inhibits cardiac muscle o Neuromuscular junction, motor end plates ▪ Motor end plate: easily excitable region of muscle where neuromuscular junction is located ▪ Neuromuscular junction: the synapse between the motor neuron and the motor end plate o Sympathetic and parasympathetic innervation o Voluntary and involuntary muscles ▪ Skeletal muscles are voluntary (somatic nervous system control) ▪ Cardiac and smooth muscles are involuntary (autonomic nervous system control) ▪ • • Specialized Cell – Muscle Cell (BIO) • Structural characteristics of striated, smooth, and cardiac muscle • Abundant mitochondria in red muscle cells: ATP source o Type I (slow twitch muscle) has a lot of mitochondria. This is b/c it relies on aerobic metabolism to generate ATP for contractions • Organization of contractile elements: actin and myosin filaments, cross bridges, sliding filament model o Actin and myosin filaments ▪ Thick filaments: made of several myosin strands wrapped around each other, with globular myosin heads protruding out the ends ▪ Thin filaments: made of actin, with the proteins troponin and tropomyosin on each end participating in contraction o Sliding filament model: depicts how myosin and actin work together by sliding across each other ▪ 1) Myosin head is in high-energy “cocked” position, with ADP and P bound to it ▪ 2) Ca2+ binds to troponin on actin, causing tropomyosin to reveal myosin binding sites on actin ▪ 3) Myosin head binds to actin, forming a cross bridge ▪ 4) Myosin kicks off ADP and P, causing the head to bend back to assume a low energy position. This drags the actin back as well, contracting it ▪ 5) ATP binds to myosin, causing it to detach from the now contracted actin ▪ 6) ATP is hydrolyzed to ADP and P. The energy of hydrolysis is used to recock the myosin head • Sarcomeres: “I” and “A” bands, “M” and “Z” lines, “H” zone o o o o • • Z-line: border separating two sarcomeres. Where actin filaments attach H-zone: area in the center of the sarcomere where there’s only myosin M-line: midpoint of the sarcomere A-band: area where myosin is present (including where it overlaps with actin), includes the Hzone and M-line o I-band: area where actin is present Presence of troponin and tropomyosin o Proteins on the end of actin filaments which enable contraction of muscle ▪ Troponin: Ca2+ binds to troponin ▪ Tropomyosin: Ca2+ binding to troponin signals for tropomyosin to reveal the active sites for myosin binding Calcium regulation of contraction o Motor neuron releasing acetylcholine causes action potential to propagate across sarcolemma ▪ T-tubules: infoldings of the sarcolemma which allow for faster propagation of an AP o Action potential causes Ca2+ channels in sarcoplasmic reticulum to open, causing Ca2+ to flow out and increasing [Ca2+] around sarcomeres o Ca2+ binds to troponin, allowing myosin and actin filaments to slide Skeletal System (BIO) • Functions o Structural rigidity and support o Calcium storage ▪ Calcium in bone • Most calcium in bone is stored as the mineral hydroxyapatite, which provides compressive strength • Some calcium is stored as calcium salts (e.g. CaHPO4) which buffer plasma Ca2+ levels ▪ Maintains gradient • Too much free calcium in the blood causes membranes to be hypoexcitable (harder to excite) • Maintains gradient of high calcium concentration outside of cells, low calcium concentration in cytosol o Physical protection o Energy storage (adipose cells in bone marrow) • Skeletal structure o Specialization of bone types, structures ▪ Two broad bone types • Spongy bone: contain red bone marrow, produce red blood cells, found in the center of a bone • Compact bone: contains lamellae and Haversian canals usually form a shell around spongy bone • Medullary cavity: contain yellow bone marrow, which holds adipose cells for fat storage. A hollow cavity within compact bone ▪ Four specialized bone types • Long: long shaft that’s important for strength, composed of spongy and compact bone (e.g. leg, arm, finger bones) • Short: cuboidal shape (e.g. ankle, wrist bones) • Flat: provide organ protection and large areas for muscle attachment (e.g. ribs, sternum, shoulder blades) • Irregular: irregular shape and variable amounts of spongy and compact bone (e.g. pelvis, ossicles in the ear) Structures • Compact bone: constantly being remodeled by osteoblasts and osteoclasts o Osteoclasts burrow tunnels in compact bone, osteoblasts fill these holes in o Lamellae: concentric rings formed by osteoblasts filling in holes o Haversian canals: open hole in center of lamellae that contain blood and lymph vessels and allow for blood and nutrient exchange ▪ Volkmann’s canals: lateral canals connecting different Haversian canals o Osteons: entire system of lamellae and a Haversian canal o Join structures ▪ Fibrous joints: very tightly held together by fibrous connective tissue. Maintains a fixed relationship between two bones, allows for very little movement (e.g. joints holding the skull bones together) ▪ Cartilaginous joints: tightly held together by cartilage. Maintains a fixed relationship but allows for slight flexibility, allowing joint to absorb energy and protect bones in trauma ▪ Synovial joints: not held together by cartilage on ends of bones, bones are separated by a capsule filled with synovial fluid. Allows for a wide range of motion • Synovial fluid: provides nourishment to cartilage, removes microbes and particles o Endoskeleton vs. Exoskeleton Bone structure o Calcium/protein matrix ▪ Inorganic materials that surround four types of bone tissue cells o Cellular composition of bone ▪ 1) Osteoprogenitor cells: differentiate into osteoblasts, only bone cell that undergoes mitosis ▪ 2) Osteoblasts: form bone by releasing collagen and other organic compounds which form bone. Incapable of mitosis. Eventually are envelopes by the matrix they release and differentiate into osteocytes ▪ 3) Osteocytes: exchange nutrients and waste materials with the blood. Incapable of mitosis ▪ 4) Osteoclasts: consume bone and release minerals into the blood. Thought to have developed from white blood cells Cartilage: structure and function o Structure ▪ Composed primarily of collagen ▪ High tensile strength (can be stretched without breaking) o Function ▪ Provides cushion, connectivity, and elasticity to joints ▪ Helps give shape and structure to various body parts (e.g. ears) Ligaments, tendons o Ligaments: connective tissue linking bone to bone o Tendons: connective tissue linking muscle to muscle Endocrine control o Opposing effects: PTH and calcitonin ▪ Parathyroid hormone: stimulates osteoclasts to release Ca2+ into the blood, breaking down bone ▪ Calcitonin: stimulates osteoblasts to store excess calcium as bone, building up bone o Vitamin D: promotes calcium absorption in the digestive system to restore calcium stores in bone ▪ • • • • Skin System (BIO) • Structure o Layer differentiation, cell types ▪ 2 principle parts • Epidermis: superficial layer • Dermis: deeper tissue ▪ Epidermis • 4 types of epidermis cells o 1) Keratinocytes: provide water impermeability and strength to skin ▪ Keratinization: keratinocytes rise to the top layer of the epidermis, dying in the process and creating a protective layer of keratin o 2) Melanocytes: transfer melanin to keratinocytes o 3) Langerhans cells: interact with Helper T-cells in immune system o 4) Merkel cells: connect with motor neurons to sense touch • 4 layers of epidermis (bottom to top) o Bottommost layer contains Merkel and stem cells ▪ Stem cells give rise to more keratinocytes and other cell types o Topmost layer contains dead keratinocytes, creating a protective layer ▪ Dermis • 5 different elements o 1) Collagen and elastic fibers: provide strength, elasticity o 2) Sensory receptors: contains touch, pain, temperature, and pressure receptors o 3) Hair follicles: traps heat around skin to maintain body heat, also plays a role in touch sensation o 4) Oil gland: associated with hair follicles, dumps oil onto skin and hair o 5) Sweat glands o Relative impermeability to water ▪ Skin is basically impermeable to water, which protects against dehydration and maintains ideal solute concentrations • Functions in homeostasis and osmoregulation o Homeostasis ▪ Skin prevents the diffusion of water, protecting against dehydration o Osmoregulation ▪ Sweating and excretion allow for skin to maintain solute concentration in body • Sweat if there’s too much solute in body • Functions in thermoregulation o Hair, erectile musculature ▪ Hairs can be erected via sympathetic stimulation ▪ This insulates warm air next to the skin o Fat layer for insulation ▪ Located between dermis and epidermis ▪ Insulates heat when epidermis begins to get colder o Sweat glands, location in dermis ▪ Eccrine sweat glands: located everywhere along dermis, responds to temperature, releases sweat to cool body ▪ Apocrine sweat glands: located in central regions of the dermis, responds to stress, releases acrid sweat o Vasoconstriction and vasodilation in surface capillaries ▪ Vasoconstriction: caused by blood being shunted away from capillaries of the skin, reduces heat loss ▪ • • • Vasodilation: caused by blood being directed towards surface capillaries, increases heat loss Physical protection o Nails, calluses, hair o Protection against abrasion, disease organisms ▪ Skin is a physical barrier from abrasion, disease Immune control o Specialized cells in epidermis provide immunity Blood reservoir / Hormonal control o Vessels in dermis can hold a lot of blood / sweating, the vasos