Unit 12 Cardiovascular System PDF

Unit 12: Cardiovascular System Role: - Transportation: O and CO2, nutrients, waste, hormone - Regulation: Temp (vasoconstriction and vasodilation), blood pressure in tissue - Protection: Blood clotting, immune cells arranged into 2 circuits: - Pulmonary: blood goes to lung to pick up...

Unit 12: Cardiovascular System Role: - Transportation: O and CO2, nutrients, waste, hormone - Regulation: Temp (vasoconstriction and vasodilation), blood pressure in tissue - Protection: Blood clotting, immune cells arranged into 2 circuits: - Pulmonary: blood goes to lung to pick up fresh oxygen - Systemic: deliver oxygen to the body Heart is composed of cardiac muscle tissue and separated in 4 chambers: - 2 atria - 2 ventricles Cardiac Muscle Tissues Cells have 1-2 nuclei, located centrally - Striated and uses the sliding filament mechanism to contract - Has large mitochondria, produces energy needed and prevents heart from fatiguing - Intercalated Discs: contains desmosomes and gap junctions (critical to heart’s contraction, allows travel of ion and action potential from cells to cells) o Joins cardiac muscle fibers - Heart contains cells, called nodes, which stimulates their own action potential, called autorhythmicity - Myocardium is involuntary Heart Features External Features: Internal Structures: Cardiac Cycle and Conducting System Cardiac Cycle: All events involved with blood flow through the heart during 1 heartbeat - Systole: Contraction phase - Diastole: Relaxation phase - Arterial blood pressure is measured as systolic/diastolic. Higher systolic pressure indicates stronger contraction, while higher diastolic pressure reflects increased resistance in the arteries Conducting System: - 1% of cardiac myocytes don’t function in contraction but have specialized features essential for normal heart excitation = nodes - Nodes have networks called conducting system of the heart, and are in electrical contact with cardiac muscle cells via gap junctions - This system helps initiate heartbeat and help spread impulses rapidly throughout the heart - “self-exciting”: spontaneously generate electrical signals (ex: the heart doesn’t need signal from the brain to beat) - The heart is innervated by both sympathetic and parasympathetic nerve fibers – only controls heart rate Electrical Conduction - Action potential = electrical conduction - For electrical current to move down a neuron, there must be a change in ion concentration o There are more Na and Cl ion in the interstitial fluid and K ions in the cytoplasm - Difference in ion concentration creates Concentration gradient and Electrical Gradient (charge inside the cell is slightly more – than outside) = polarized cell - Resting Membrane Potential = -70mV inside the cell Depolarization: - When nerve receive impulse, Na flows in, K flows out along the membrane, making this part of the cell more positively charged - When membrane potential becomes –55mV, more Na channels open, so more Na comes in – creating membrane potential of +30mV - This is how “current” moves down a neuron Repolarization: - As signal moves down the neuron, the areas that were opened, “reset” their charge by opening k channels and K flows out. - The cell becomes negative again - This continues down the neuron, following and “resetting” areas that was depolarized - Cell gets to original membrane potential (-70), using Na and K pump Electrical Conduction of the Heart SA Node (pacemaker of the heart): things happen differently here. - Cells have resting membrane potential that fluctuates (rises and falls irregularly), but usually at –60mV - These are no signals that causes depolarization because it happens spontaneously: o Na channel allows slow leak of Na into the cell, when it depolarized to –40mV, Ca channels open o Ca rapidly flows into the cell, depolarizing more until +10mV, then K channels open for repolarization o These steps repeat as Na channel slowly leaks Na back into the cell Conducting systems of the heart: - Sinoatrial (SA) Node: generate cardiac impulses – travels to AV Node - Atrioventricular (AV) Node: Passes impulses to the AV bundle - AV Bundle: Impulses pass to the AV bundle and travel down the interventricular septum - Bundle Branches: AV bundle divides into left and right bundle branches under the endocardium  - Purkinje fibers: Bundle branches give off the purkinje fibers, which spread impulses to the ventricular wall and papillary muscles o stimulate contraction of the papillary muscles at the same time as the ventricles contract in a twisting, upward motion. Excitation of Cardiac Myocytes - The contractile myocytes must be stimulated by the electrical current of the heart - The myocytes contain a specialized network of channels called the sarcoplasmic reticulum which store Ca ions - When the myocyte is activated, Na+ and Ca2+ flow into the cell, but a small amount also flows into adjacent myocytes via gap junctions – this cell is stimulated to depolarize like the first myocyte and the action potential moves from one cell to the next - The influx of calcium also causes the myocyte to contract Arrythmias: - Irregular heart rhythm due to defect in conduction system - SA node disrupted - Causes: o Coronary artery disease – atherosclerosis o Hypertension, Myocardial infarction, Hyperthyroidism, Defective heart valves, Stress, Drugs and chemicals Cardiac Output Total amount of blood ejected from the left ventricle per minute- - Cardia Output (CO) = Heart Rate x Stroke (SV) Math: - mL/min = (beats/min) x (mL/beats) - =mL/min = mL/min Can be affected by: - ANS, Endocrine system, Blood V, Condition of the heart, Ability to pump blood, Different hormones, Ion concentration Heart Rate (Beats/min) - Influenced by: o Stress, exercise, blood ion concentration - Controlled mainly by Autonomic nervous system (ANS) and its 2 parts: - Sympathetic nervous system (SNS) o Releases norepinephrine = increase HR and force of contractions o Refers to flight, fight, freeze reaction - Parasympathetic nervous system (PNS) o Releases acetylcholine = decreases HR and force of contractions o Rest and digest Stroke Volume (mL/Beats) - Stroke volume produced by the heart of avg size = around 70 mL - Strength of contraction is directly proportional to the amount of stretch in the myocardial fibers o Larger the blood V = larger the stretch = greater the strength of contraction - SV is difference between 2 different V in the left ventricles: o End-diastolic Volume (about 120 ml) - more V o End-systolic Volume (About 50ml) - less V o SV = EDV (volume after beat) – ESV (volume before beat) - Preload (Volume of blood returning to the right atria)): proportional to the amount of ventricular myocardial fiber stretch just before the ventricle contracts - Afterload: The pressure that ventricles must overcome to force open the aortic and pulmonary valves o Anything that increases systemic or pulmonary arterial pressure can increase afterload o Ex: Hypertension Anatomy of the Blood Vessels Arteries and Arterioles: - Carried blood away from heart - Needs to be able to expand because of the high-pressure cause by contraction of the heart - Contains elastic and smooth muscle layer - Vasoconstriction and vasodilation: regulate blood flow - Controlled by ANS Veins and Venules: - Returns blood to heart - Walls are thinner because blood pressure is lower than in arteries - Has unidirectional valves that prevent backward flow of blood Capillaries: - Site for oxygen and nutrient exchange from the blood to body’s cells - Made of only endothelial cells - Lower blood pressure than in arteries - Precapillary sphincters: Can open or close capillary beds based on the needs of the tissue Circulatory Routes: pulmonary circulation The flow of blood through the heart and circulatory system occurs as follows: 1. Deoxygenated blood enters the right atrium from the body via the superior and inferior vena cava. 2. The right atrium pumps blood into the right ventricle, which sends it to the lungs via the pulmonary artery for oxygenation (pulmonary circulation). 3. Oxygenated blood returns to the left atrium from the lungs via the pulmonary veins.  4. The left atrium pumps blood into the left ventricle, which sends it to the body through the aorta (systemic circulation). Vascular Resistance and Blood Pressure - Sphygmomanometer: measures blood pressure o Normal healthy blood pressure = about 120/80 Factors affecting blood flow: - Atherosclerosis: primary cause of cardiovascular disease o Build-up of plaque (mostly fat and immune cells) within the walls of blood vessels - Leads to Turbulent blood flow increases resistance and decreases both blood flow to tissues and clot formation Cardiovascular Disease Most preventable of all diseases Hypertension - Cause of untreated hypertension for many years: o Stress on the heart: enlarged heart (heart muscle will increase in size to compensate for increase load ▪ Arrthythmias and hypoxia o Small hemorrhages: cause of increased pressured in the capillary ▪ Kidney damage, brain damage (stroke), retinal damage, lung damage  Hemorrhage classification: - Medication: o Diuretic decreases blood V o Vasodilators decreases vascular resistance Angina/Myocardial Infarction - Symptoms: chest pain, pressure, heaviness, tightness, burning - Lasts for few minutes or less – heart attack last longer, even hours - Causes: o Ischemia or hypoxia: lack of oxygen to the heart muscle - Cause of ischemia: decreased blood flow in coronary arteries o Atherosclerosis: plaque in blood vessels o Hypertension: enlarged heart Stroke - Transient ischemic attack (TIA): Mild symptoms, stroke highly likely - Other symptoms depend on which part of the brain was damaged: o Headache, dizziness, weakness on one side of the body, nausea - Long-term affect depends on the extent of hypoxia - Too much damage can lead to death of the cells that lacked oxygen Component of the blood Blood is made of cells, platelets and plasma Plasma: made up of water, ions, vits, nutrients, hormones, plasma proteins, waste product - 55-58% of the total blood V - Electrolytes: ions dissolved and must be in balance to maintain functioning of all cells Platelets: cell fragments derived from thrombocytes in bone marrow - Cell fragments have no organelles but has granules – important for blood clotting/coagulation - Hemophilia: Genetic Disorder, deficiency in clotting factors (usually factor VIII) - Vit K deficiency: o Decreased synthesis of clotting factors o Need healthy gut bacteria because they make vit K White blood cells (Leukocytes): Helps defend the body against diseases and can leave the bloodstream to fight infections - Formed in red bone marrow from hematopoietic stem cells - 7 types circulating in the blood, distinguished by size, granular appearance of the cytoplasm, shape of the nucleus and staining characteristics - Classified in: - Granulocytes (4): has granular cytoplasm (neutrophils, eosinophils, and basophils), natural killer cells, short lifespan (about 12 hours) - Agranulocytes (2): no granular cytoplasm (monocytes and lymphocytes – T & B cells), longer lifespan Erythrocytes (RBC): - 42-45% of blood V - Function in oxygen and CO2 transport o Has a bi-concave disk shape, flexible membrane, large surface area for diffusion ▪ Hemoglobin (binds oxygen and CO2) and made of 4 proteins + iron  - Made in red bone marrow by the process called erythropoiesis (also called hematopoiesis) o Erythropoietin (hormone made in kidneys) triggers differentiation of stem cells to erythrocytes Blood type Blood type Antigen Antibodies Can receive Can give to from (recipients) (donors) A A B A, O A, AB B B A B, O B, AB AB A, B none A, B, AB, O AB (universal recipient) O none A, B O A, B, AB, O (Universal donor) Blood type Antigen antibodies donors recipients RH+ + +, - + RH- + - +, - RH factors (surface antigen D): a protein that tells the full blood type - Another surface erythrocytes antigen - Determine Rh blood type - When present = Rh+ - When absent = Rh- - Antibodies to Rh factor: o Appears when Rh- person is exposed to Rh+ blood o Inappropriate blood transfusion