Unit 1 1. Diagram, without reference to your notes or book, the path of blood flow through the heart and lungs. Right Atrium, Tricuspid Valve, Right Ventricle, Pulmonary Valve, Pulmonary trunk and arteries, pulmonary capillaries, pulmonary veins, left atrium, bicuspid valve, left ventricle, aortic valve, aorta and systemic arteries, systemic capillaries and veins, superior vena cava, inferior vena cava and coronary sinus. 2. Describe the sequence of excitation of the cardiac conduction system. Sinoatrial node  pacemaker in the right atrial wall spontaneously discharge action potentials at a rate of 100120/ minute, autonomic nerves modify the rate to about 70b/minute (depolarization) Atrioventricular node poorly conducting tissue (small fibers and few gap junctions) AV bundle of Hisleads to the right and left bundle branches transmitting the AP into muscle of both ventricles atrial repolarization Left and right bundle branches Purkinje fibers the lower portions of the ventricles contract first pushing blood upwards 3. Define and describe the major determinants of stroke volume, and the underlying mechanisms of each. Cardiac Output (L/min)= Stroke Volume (L/beat) X Heart Rate (beats/min) Stroke volume is affected by the aortic blood pressure (afterload), end diastolic volume (preload) and contractility. Afterload ventricles cannot eject blood into the aorta or pulmonary artery until the pressure in the ventricle exceeds the pressure in the vessel (increase in arterial pressure will have a major impact on work of heart and stroke volume) Preload end diastolic volume and impacts stroke volume SV cannot increase unless the rate of cardiac filling also increases Contractility the strength of the cardiac muscle contraction Active change due to sympathetic stimulation Passive change due to changes in length of the muscle fibers 4. Describe how the autonomic nervous system (ANS) controls heart rate. ANS affect heart rate by chronotropic effects, ANS activity can be modified by circulating hormones and higher brain structures. Sympathetic neurons that send nerve fibers to the heart are located in the cardiovascular center (caudal portion of medulla oblongata) Sympathetic (increases rate of depolarization due to increased Na current) neurons in CV center synapse upon preganglionic neurons in intermediolateral cell columns of thoracic spinal cord 1. preganglionic neurons synapse (release ACh) on postganglionic neurons located in sympathetic chain ganglia 2. PGN sent their axons (releases NE) to the SA and AV nodes and cardiac muscle fibers 3. NE activates beta 1 receptors a. neurons are brought to threshold more frequently because Na+ abundant Parasympathetic PSN in CV centers of brain stem send axons to heart in vagus nerves 1. vagal motoneurons synapse directly on the SA and AV nodes and on atrial muscle fibers a. release ACh into postsynaptic cells leading to slowing of heart rate b. Ach increased potassium permeability of cells so K diffusion is increased c. results in hyperpolarization of cell membrane d. takes more time for spontaneous upward drift in membrane potential to reach the threshold for Ca++ channel activation 5. Describe the forces that result in movement fluid into and out of capillaries Bulk flow fluid exchange between ISF and capillaries occurs primarily by bulk flow Movement out of blood capillaries into the ISF *Blood hydrostatic pressure pushes fluid out through the capillary pores interstitial fluid osmotic pressure pulls fluid out via osmosis (small compared to BHP) Movement into blood capillaries from ISF *Blood colloid osmotic pressure differences in protein concentration between plasma and ISF tends to pull water from the ISF into the capillaries Interstitial fluid hydrostatic pressure pressure exerted by interstitial fluid but is typically very small Net filtration pressure NFP= (BHP+IFOP) (BCOP+IFHP) push (filtration)pull (reabsorption) Filtration results in constant flow of fluid that washes over the tissue cells at the arterial end of the capillary, carrying nutrients and oxygen with it Reabsorption results in a return of fluid to the capillary at the venous end, thereby depositing waste into the venous system 6. Describe the principal components of vascular resistance, and explain why vessel diameter has such a large impact on resistance. Hemodynamics the study of fluid flow in vascular system Fluids flow from regions of high pressure to regions of lower pressure Resistance to fluid flow is caused by friction between the molecules in the fluid and with walls of the tube Frictional resistance reduces flow Aorta 3cm^2 40cm/sec Vena Cava 14 cm^2 520 cm/sec Capillaries 5000 cm^2 0.1 cm/sec 7. Describe how hormones can either decrease or increase blood pressure. Catecholamines circulate and bind directly to cardiac muscle fibers and to blood vessel smooth muscle cells (increases HR and SV and constriction of veins and arterioles) Brain and heart vessels have little smooth muscle and do not vasoconstrict by SNS and catecholamines (autoregulated) Increase Blood Pressure Angiotensin II causes intense vasoconstriction when renal perfusion is inadequate acts on arterioles simultaneously when released into blood Low pressure stimulates release of renin by the kidney=> converts angiotensinogen to AT I in the lungs angiotensin converting enzyme in lungs converts AT I to AT II Aldosterone causes water retention and increases blood volume Angiotensin regulates aldosterone secretion high ATII levels stimulates aldosterone secretion by adrenal cortex ADH causes widespread vasoconstriction in cases of extreme low BP Decrease Blood Pressure Atrial natriuretic peptide ANP released by cells of the atria when blood pressure is high Promotes vasodilation promotes water loss and salts by the kidneys reduces blood volume and pressure Histamine released by mast cells causes vasodilation by relaxing blood vessel smooth muscle role in increasing blood flow to inflamed or damaged tissue 8. Describe the origin and production of the formed elements in the blood. I. Formed elements A. RBCs 1. Pluripotent stem cells =>myloid stem cells=> proerythroblasts=> reticulocytes=> RBC B. WBC 1. Granular leukocytes a) neutrophils (myloid stem cell) b) eosinophils (MSC) c) basophils (MSC) 2. agranular leukocytes a) lymphocytes (lymphoid stem cell) b) monocytes (MSC) C. Platelets (special cell fragments)