Physiology of the Cardiovascular System

Vocabulary flashcards for the Cardiovascular System

Hemodynamics

Collection of mechanisms that influence the dynamic circulation of blood

Conduction system of the heart

Intrinsic control of heartbeat due to SA and AV node

SA node (pacemaker)

Initiates each heartbeat and sets its pace; Specialized pacemaker cells in the node possess an intrinsic rhythm

Electrocardiogram (ECG)

Graphic record of the heart’s electrical activity, its conduction of impulses; a record of the electrical events that precede the contractions of the heart

P wave

Represents depolarization of the atria

QRS complex

Represents depolarization of the ventricles and repolarization of the atria

T wave

Represents repolarization of the ventricles

Cardiac cycle

A complete heartbeat consisting of contraction (systole) and relaxation (diastole) of both atria and both ventricles

Atrial systole

Contraction of atria completes emptying of blood out of the atria into the ventricles; AV valves are open; semiluminar (SL) valves are closed; Ventricles are relaxed and fill with blood

Isovolumetric ventricular contraction

Occurs between the start of ventricular systole and the opening of the SL valves; Ventricular volume remains constant as the pressure increases rapidly

Ejection

SL valves open and blood is ejected when the pressure increases in the ventricles exceeds the pressure in the pulmonary artery and aorta

Isovolumetric ventricular relaxation

Ventricular diastole begins with this phase; Occurs between closure of the SL valves and opening of the AV valves; A dramatic fall in intraventricular pressure but no change in ventricular volume

Passive ventricular filling

Returning venous blood increases intra-atrial pressure until the AV valves are forced open and blood rushes into the relaxing ventricles

Perfusion pressure

Pressure gradient needed to maintain blood flow through a local tissue

Cardiac output

Volume of blood pumped out of the heart per unit of time (ml/min or L/min)

Stroke volume (SV)

Volume pumped per beat

Starling’s law of the heart (Frank-Starling mechanism)

Within limits, the longer, or more stretched, the heart fibers at the beginning of contraction, the stronger the contraction

Contractility

Strength of contraction; can also be influenced by chemical factors

Aortic baroreceptor reflex

Aortic baroreceptors and carotid baroreceptors, located in the aorta and carotid sinus, they affect the autonomic cardiac control center, and therefore parasympathetic and sympathetic outflow, to help control blood pressure

Peripheral resistance

Resistance to blood flow imposed by the force of friction between blood and the walls of its vessels

Vasomotor mechanism

Muscles in walls of arteriole may constrict (vasoconstriction) or dilate (vasodilation), thus changing diameter of arteriole

Vasomotor pressor reflexes

Sudden increase in arterial blood pressure stimulates aortic and carotid baroreceptors; results in arterioles and venules of the blood reservoirs dilating

Vasomotor chemoreflexes

Chemoreceptors located in aortic and carotid bodies are sensitive to hypercapnia, hypoxia, and decreased arterial blood pH

Medullary ischemic reflex

Acts during emergency situation when blood flow to the medulla is decreased; causes marked arteriole and venous constriction

Vasomotor control by higher brain centers

Impulses from centers in cerebral cortex and hypothalamus transmitted to vasomotor centers in medulla to help control vasoconstriction and dilation

Venous return

Amount of blood returned to the heart by the veins

Stress-relaxation effect

Occurs when a change in blood pressure causes a change in vessel diameter (because of elasticity) and thus adapts to the new pressure to keep blood flowing (works only within certain limits)

Venous pumps

Blood-pumping action of respirations and skeletal muscle contractions facilitate venous return by increasing pressure gradient between peripheral veins and venae cavae

Capillary exchange

Governed by Starling’s law of the capillaries

Antidiuretic hormone mechanism

Decreases the amount of water lost by the body by increasing the amount of water that kidneys reabsorb from urine before it is excreted from the body; triggered by input from baroreceptors and osmoreceptors

Renin

Released when blood pressure in kidney is low; leads to increased secretion of aldosterone, which stimulates retention of sodium, causing increased retention of water and an increase in blood volume

Atrial natriuretic peptide mechanism

Adjusts venous return from an abnormally high level by promoting the loss of water from plasma, causing a decrease in blood volume; increases urine sodium loss, which causes water to follow osmotically

Arterial blood pressure

Measured with a sphygmomanometer and stethoscope; listen for Korotkoff sounds as the pressure in the cuff is gradually decreased

Systolic blood pressure

Force of the blood pushing against the artery walls while ventricles are contracting

Diastolic blood pressure

Force of the blood pushing against the artery walls when ventricles are relaxed

Pulse pressure

Difference between systolic and diastolic blood pressure

Arterial bleeding

Blood escapes from artery in spurts because of alternating increase and decrease of arterial blood pressure

Venous bleeding

Blood flows slowly and steadily because of low, nearly constant pressure

Minute volume

Determined by the magnitude of the blood pressure gradient and peripheral resistance

Pulse

Alternate expansion and recoil of an artery