PGY 300 1st EditionExam #2 Study Guide Lectures: 1 - 7Structure of heart 4 Chambers- RA, RV,LA,LV RA & LA are reservoirs for blood being sent to the RV & LV RV & LV are the main pumping chambers of the heart RA & RV goes to lungs, gets rid of CO2, Pulmonary circulation LA & LV Systemic circulation Heart contains 4 valves AV valves & 2 semilunar valves Tricuspid valve is between the RA & RV (AV valve) Bicuspid or Mitral valve is between the LA & LV (AV valve) Pulmonic valve is between the RV & pulmonary artery (semilunar valve) Aortic valve is between the LV & aorta (semilunar valve) Valves open and close in response to pressure changes in the heart Valves act as one way doors to keep blood moving forwardSystemic Circulation: Carries O2 to tissue, high resistance = high pressurePulmonary Circulation: Oxygenated blood, low resistance = low pressureVenus Return: blood returning back to heart VR from systemic to right heart VR from pulmonary to left heart  VR = COOxygen Transport Oxygen Comsumption (VO2): How much oxygen body consumers per min Cardiac Output (CO): blood pumped out of heartBlood flow from heart -> tissue, oxygen delivered to tissuesBlood Flow Pressure difference between two points in the circulation: ΔP = P1 - P2 Resistance to flow Radius (1/r4), length (1/L) , blood viscosity (1/v) R = 1/r4  BF = ΔP/R MAP = BP x R BF proportional to ΔP, i.e. increase ΔP increased BF decreased ΔP decreased BF BF inversely proportional to increase ΔP decreased BF decreased ΔP increased BF Small change in radius = large change in resistanceAutonomic Control of Cardiac Function  Autonomic – Cardiovascular Control Center- Controls the “Pacemaker” of the heart (excites heart) Sympathetic nerve activity (SNA)- Excitatory - Accelerates the heart - Two chemicals are influenced by the sympathetic system – epinephrine & norepinephrine- These chemicals increase HR, contractibility, automaticity, and AV conduction Parasympathetic nerve activity (PSNA)- Depressant, Slows the heart, - The vagus nerve is one of this systems nerve, when stimulate decrease HR and AV conduction.Structure of Heart Pericardium: connective tissue sack around heart, protective layer  Myocardium: contracting part of muscle  Aorta: comes out of LV, brings blood to brain  Descending aorta: goes to abdomen then dependent limbs Pulmonary artery: comes out of RV goes up into the lung  Superior Vena Cava: bring blood back to venous side into RACardiac cells – two types, electrical and myocardial (``working") Electrical cells- Make up the conduction system of the heart- Are distributed in an orderly fashion through the heart- Automaticity: the ability to spontaneously generate and discharge an electrical impulse- Excitability: the ability of the cell to respond to an electrical impulse- Conductivity: the ability to transmit an electrical impulse from one cell to the next Myocardial cells- Make up the muscular walls of the atrium and ventricles of the heart- Contractility - the ability of the cell to shorten and lengthen its fibers- Extensibility - the ability of the cell to stretch- Have striations - dependent on deliver of oxygen by blood- -Slow twitch fibers: highly dependent on oxygenVentricular Contraction: AV valves remain closed to prevent back flow of blood to the atriaVentricular Relaxation: Semilunar valves prevent blood that entered the arteries from flowing back into the ventricle during ventricular relaxationConduction system Inherent firing rate: rate at which the SA node or another pacemaker site normally generates electrical impulses SA Node - Sinoatrial node- Dominant or primary pacemaker of the heart- Inherent rate 60 – 100 beats per minute- Located in the wall of the right atrium, near the inlet of the superior vena cava- Once an impulse is initiated, it usually follows a specific path through the heart, and usually does not flow backward Intra-atrial tracts - Bachmann's bundle- As the electrical impulse leaves the SA node, it is conducted through the left atria by way of the Bachmann's bundles, through the right atria, via the atrial tracts AVJunction - Made up of the AV node and the bundle of His- AV node: - Is responsible for delaying the impulses that reach it - Located in the lower right atrium near the interatrial septum -Waits for the completion of atrial emptying and ventricular filling, to allow thecardiac muscle to stretch to it's fullest for peak cardiac output -The nodal tissue itself has no pacemaker cells, the tissue surrounding it (calledthe junctional tissue) contains pacemaker cells that can fire at an inherent rate of 40 – 60 beats per minute Bundle of His- Resumes rapid conduction of the impulses through the ventricles- Makes up the distal part of the AV junction then extends into the ventricles next to the interventricular septum- Divides into the Right and Left bundle branches Purkinje Fibers- Conduct impulses rapidly through the muscle to assist in depolarization and contraction- Can also serve as a pacemaker, discharges at an inherent rate of 20 – 40 beats per minute or even more slowly- Are not usually activated as a pacemaker unless conduction through the bundle of His becomes blocked or a higher pacemaker such as the SA node or AV junction do not generate an impulse- Extends form the bundle branches into the endocardium and deep into the myocardial tissueDepolarization and Repolarization- Cardiac cells at rest are considered polarized, meaning no electrical activity takes place- The cell membrane of the cardiac muscle cell separates different concentrations of ions, such as sodium, potassium, and calcium = resting potential- Electrical impulses are generated by automaticity of specialized cardiac cells- Depolarization: Once an electrical cell generates an electrical impulse, this electrical impulse causes the ions to cross the cell membrane and causes the action potential- The movement of ions across the cell membrane through sodium, potassium and calcium channels, is the drive that causes contraction of the cardiac cells/muscle- Depolarization with corresponding contraction of myocardial muscle moves as a wave through the heart- Repolarization: the return of the ions to their previous resting state, which corresponds with relaxation of the myocardial muscle-