Anatomy of the Heart
4 Chambers Blood Circulation |
Right AV valve (tricuspid) -> pulmonary(semilunar) valve -> left AV valve/bicuspid/mitral -> aortic/semilunar valve |
Pulmonary circulation |
Chambers on the right pump oxygen poor blood to the lungs |
Systemic Circulation |
Chambers on the left pump oxygen rich blood to body tissues |
Right atrium |
receives oxygen poor blood from inferior and superior vena cava |
Right Ventricle |
receives oxygen poor blood from the right atrium and pumps blood through the pulmonary valve into pulmonary artery |
Left atrium |
receives oxygen rich blood from pulmonary circulation via the left and right pulmonary veins |
Left Ventricle |
receives oxygen rich blood from left atrium and pumps blood through aortic valves into aorta |
Chordae Tendinae |
tendonous fibers attached to the inside edges of AV valves and base of ventricles via papillary muscles, prevents valves from everting |
Connective Tissue |
separates atria for ventricles providing attachment of heart valves |
Electrical Activity
Autorhythmiticity |
heart muscle is capable of generating its own rhythmic electrical acticity |
Pacemaker activity |
spontaneous, rhythmic generation of electrical impulses by specialized heart cells (like those in the sinoatrial node) that initiate and regulate the heartbeat, ensuring consistent cardiac contraction and blood circulation |
SA Node |
generates 70 AP per min, located in the wall of the right atrium near superior vena cava |
AV Node |
50 AP per minute, located at the base of the right atrium follows the SA node |
Bundle of His |
specialized pacemaker cells originating at AV node projecting into left and rightventricles |
Purkinje FIbers |
30 AP per min, spread throughout ventricular myocardium |
Interatrial Pathway |
specialized cardiac cells that conducts pacemaker activity from the right atrium to the left atrium |
Internodal Pathway |
pathway of specialized cardiac cells that conducts pacemaker activity from SA to AV nodes |
AV nodal delay |
Pacemaker activity is conducted relatively slowly through the AV node resulting in a delay of approximately 100 ms |
Electrocardiogram Waveforms
P wave |
Depolarization of the atria |
QRS complex |
depolarization of the ventricles |
T wave |
repolarization of the ventricles |
PR segment |
represents AV nodal delay |
Electrocardiogram Waveforms
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Mechanical Events of the Cardiac Cycle
Systole |
Contracting and emptying |
Diastole |
relaxation and filling |
End Dastolic Volume |
volume of blood in chamber at end of diastole , equivalent to max amount og blood chamber holds during cycle |
Isovolumetric ventricular contraction |
period of time during contraction when chambers stay closed increasing chamber pressure during this periods |
End systolic volume |
amount of blood remaining in the chamber at the end of systole |
Stroke volume |
amount of volume blood pumped out of the chamber with each contraction |
Stroke volume equation |
EDV - ESV |
Isovolumetric ventricular relaxation |
period of time during relaxation when the chamber remains closed and therefore no blood can enter or leave, chamber pressure decreases then |
Lub |
closure of AV valves |
Dup |
Closing of the semilunar valves |
Murmurs |
abnormal heart sounds from turbulent flow of blood through malfunctioning valves |
Stenotic valve |
stiff narrow valve that doesn't open completely , abnormal whistling sound |
Insufficient valve |
structurally damaged valve that does not close, abnormal swishing sound |
Rheumatic fever |
an auto-immune disease triggered by streptococcal bacteria that leads to valvular stenosis and insufficiency |
Regulation of Cardiac Output
Cardiac Output |
HR - SV |
Heart rate regulation done by |
parasympathetic and sympathetic nervous systems |
Stroke Volume |
regulated intrinsically by volume of venous blood returning to the ventricles and extrinsically by the sympathetic nervous system |
Parasympathetic |
Vagus Nerve to the SA and AV nodes and to the contractile cells of the atria |
Parasympathetic NTs |
ACh and Muscarinic receptors |
Effects of Parasympathetic Release of ACh |
Increases permeability of SA nodal cells to K+ in the SA node leading to greater hyperpolarization and slowing of the K component of the pacemaker potential, in AV node increases permeability of AV nodal to K and in atrial contractile cells, shortens duration of cardiac fiber AP reducing Ca++ permeability |
Sympathetic |
Norepinephrine through beta adrenergic receptors |
Effects of Sympathetic influence on HR |
SA node - less hyperpolarization, acceleration of the K component, av node slowing increase in Ca++ permeability |
Stroke Volume Regulation |
Extrinsically regulated by neural control and intrinsically by the volume of venous blood returning to heart |
Intrinsic control |
direct correlation between end-diastolic volume and stroke volume |
Heart failure |
inability of CO to meet emands of the body |
Basic Organization
Arteries |
composed of large vessels that carry blood from the heart |
Arterioles |
small diameter vessels that arise from the branching of arteries |
Capillaries |
smallest diameter vessels that are formed when arterioles branch |
Venules |
the vessels that form when capillaries join together |
Veins |
large diameter vessels formed by merging of venules |
Microcirculation |
name given to collection of arterioles, capillaries and venules |
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Blood Flow
Blood flow |
determined by pressure gradient in the vessels and resistance to flow caused by friction and viscosity of the blood |
Blood flow equation |
F=deltaP/R |
F |
Flow rate, volume of blood passing through a vessel per unit of time |
Delta P |
Pressure gradient - difference in pressure between the beginning and end of the vessel |
Resistance |
depends on blood viscosity, vessel length, vessel radius |
Blood viscocity |
friction developed in blood determined by the concentration of plasma proteins and number of circulating RBCs |
Vessel length |
friction between blood and the inner surface of a vessel is proportional to the vessel length |
Vessel radius |
friction between blood and the inner surface of a vessel is inversely proportional to the 4th power of the vessel radius |
Pressure resovoir |
Serves as a driving force during ventricular diastole, elasticity of the of artery walls smooth muscle, collagen, elastin |
Pulse Pressure |
pressure difference between systolic pressure and diastolic pressure |
Mean Arterial Pressure |
pressure that is monitored and regulated by BP reflexes |
Intrinsic (local control)
intrinsic control |
factors intrinsic to an organ or tissue |
Local metabolic changes |
factors derived from metabolic activity causing dilation. smooth muscle tone is controlled by release of mediators such as NO |
O2 concentration |
reduced O2 during metabolic demand |
CO2 concentration |
increased CO2 during metabolic demand |
pH |
increases in CO2 and or lactic acid lowers blood pH |
Extracellular K+ conc. |
increased neuronal activity that outpaces the Na+/K+ ATPase |
Osmolarity |
increased solute concentration resulting from metabolic activity |
Adenosine |
released in Cardiac muscle in response to metabolic demand |
Prostaglandins |
produced from teh metabolism of faty acids |
Histamine release |
release when tissues are damaged and leads to vasodilation accompanying an inflammatory response |
local physical control |
temperature and myogenic response |
Temperature |
arteriolar smooth muscle tone is inversely proportional to temperature |
Myogenic response |
arteriolar smooth muscle responds to stretch by contracting |
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