visceral pericardium
Innermost layer of the serous membrane around the heart; epicardium
pericardial sac
This encases and protects the heart from trauma & infection. Has two layers (parietal & visceral). Holds 5-30 mL of pericardial fluid, lubricates the pericardial surfaces & cushions the heart.
parietal pericardium
the tough outermost layer of the pericardium that is attached to the diaphragm and the sternum
heart valve
structures within the heart that open and close with the heartbeat to regulate the one-way flow of blood
sinoatrial node
Pacemaker of the heart" located at the superior vena cava / right atrium junction; intrinsic rate of about 70 bpm
atrioventricular node
Coordinates the incoming electrical impulses from the atria and relays that impulse to the ventricles through a bundle of specialized muscle fibers called the bundle of His (AV Node)
bundle of His
neurological fibers, extending from the AV node to the right and left bundle branches, that fire the impulse from the AV node to the Purkinje fibers
Purkinje fibers
Distribute electrical charge to cardiac muscle cells of ventricles, causing depolarization of cells, which results in both ventricles contracting together
baroreceptors
sensors in the walls of the carotid arteries and aorta that detect changes in blood pressure, causing stimulation of the sympathetic or parasympathetic nervous system to alter the rate and force of cardiac contractions
contractility
Capacity of the heart to produce active force; cardiac muscles shorten or CONTRACT in response to electrical impulse, pumping blood from the heart
cardiac control center
Medulla oblongata
anastomoses
direct connections between coronary arteries and arterioles that have the potential to provide another course of blood to an area
collateral circulation
provided by anastomoses, an alternate route that can supply the tissue with blood if the primary route becomes obstructed
cardiac cycle
A complete heartbeat consisting of contraction and relaxation of both atria and both ventricles
systole
A phase during which the ventricles contract and eject blood into the pulmonary and systemic circuits.
diastole
'Filling Phase', atria and ventricles all relax, blood from atria flows to ventricles, and from major veins into atria.
isovolumetric phase
The period of ventricular systole when contraction has started, but all of the valves are closed (aortic valve has not changed) and thus there is no change of volume.
heart sounds
Lub-dub. 1st- a-v valves close. 2nd- aortic and pulmonary valves close
cardiac output
Volume of blood pumped by the ventricles into the pulmonary & systemic circulation in 1 minute (4 - 5L/min). CO = HR x SV
stroke volume
Volume of blood ejected by the ventricles with each contraction.
It can be affected by the amount of blood in the left ventricle at the end of diastole (preload), the resistance to left ventricular ejection (afterload), and myocardial contractility.
cardiac reserve
The ability of the heart to increase output in response to increased demand
preload
Volume of blood that fills the heart and stretches the heart muscle fibers during its resting phase (volume of blood in ventricles at end of diastole, just prior to contraction)
afterload
Pressure needed to eject blood out of heart into the aorta (blood viscosity, volume, and peripheral vascular resistance effect afterload); higher afterload means harder to eject blood which decrease SV.
peripheral vascular resistance
the resistance of the vessels to the flow of blood: increased when the vessels constrict, decreased when the vessels relax.
blood pressure
Pressure exerted by the blood upon the walls of the blood vessels, especially arteries, usually measured by means of a sphygmomanometer and expressed in millimeters of mercury.
systolic blood pressure
The blood pressure measured during the period of ventricular contraction; in blood pressure readings, it is the higher, upper number of the two measurements
diastolic blood pressure
Pressure exerted against the walls of the artery when the left ventricle is at rest
pulse pressure
Difference between the systolic and diastolic pressures, normally 30 to 40 mm Hg.
sympathetic nervous system
A subdivision of the autonomic nervous system that activates nerves, glands and visceral muscles in times of stress or threat (prepares the body for action)
parasympathetic nervous system
A subdivision of the autonomic nervous system that calms the body after action and also retains the body functioning at is normal state (homeostasis)