Term
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Definition
| - The heart lies in the mediastinum, an anatomical region that extends from the sternum to the vertebral column, from the first rib to the diaphragm, and between the lungs |
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Term
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Definition
| Formed by the tip of the left ventricle (a lower chamber of the heart) and rests on the diaphragm. |
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Term
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Definition
- Posterior surface
- Formed by the atria (upper chambers) of the heart, mostly the left atrium. |
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Term
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Definition
| Deep to the sternum and ribs. |
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Term
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Definition
| Part of the heart between the apex and right border and rests mostly on the diaphragm |
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Term
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Definition
| Faces the right lung and extends from the inferior surface to the base. |
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Term
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Definition
- Also called the pulmonary border, faces the left lung
- Extends from the base to the apex |
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Term
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Definition
- The membrane that surrounds and protects the heart
- Confines the heart to its position in the mediastinum
- Allows sufficient freedom of movement for vigorous and rapid contraction. |
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Term
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Definition
- Consists of two main parts:
(1) Fibrous pericardium
(2) Serous pericardium |
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Term
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Definition
- Tough, inelastic, dense irregular connective tissue.
- Resembles a bag that rests on and attaches to the diaphragm
- Prevents overstretching of the heart
- Provides protection, and anchors the heart
- Partially fused to the central tendon of the diaphragm and therefore movement of the diaphragm, as in deep breathing
- Facilitates the movement of blood by the heart |
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Term
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Definition
| - Thinner, more delicate membrane that forms a double layer around the heart |
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Term
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Definition
- The outer layer of the serous pericardium
- Fused to the fibrous pericardium |
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Term
| Visceral Layer / Epicardium |
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Definition
- One of the layers of the heart wall
- Adheres tightly to the surface of the heart |
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Term
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Definition
- Between the parietal and visceral layers of the serous pericardium
- A thin film of lubricating serous fluid.
- Reduces friction between the layers of the serous pericardium as the heart moves. |
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Term
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Definition
| - Space that contains the few milliliters of pericardial fluid |
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Term
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Definition
- External Layer (Epicardium)
- Middle Layer (Myocardium)
- Inner Layer (Endocardium) |
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Term
| External Layer (Epicardium) |
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Definition
- Composed of two tissue layers.
- Outermost = visceral layer of the serous pericardium.
- Imparts a smooth, slippery texture to the outermost surface of the heart.
- Contains blood vessels, lymphatics, and vessels that supply the myocardium |
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Term
| Middle Layer (Myocardium) |
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Definition
- Responsible for the pumping action
- Composed of cardiac muscle tissue |
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Term
| Inner Layer (Endocardium) |
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Definition
- Thin layer of endothelium overlying a thin layer of connective tissue.
- Provides a smooth lining for the chambers of the heart and covers the valves of the heart.
- Minimizes the surface friction as blood passes through the heart. |
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Term
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Definition
The heart has four chambers:
1) Atria (x2)
2) Ventricles (x2) |
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Term
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Definition
- Two superior receiving chambers
- Receive blood from blood vessels returning blood to the heart, called veins |
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Term
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Definition
- Two inferior pumping chambers
- Eject blood from heart into blood vessels (arteries) |
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Term
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Definition
- Wrinkled pouchlike on the anterior surface of each atrium
- Increases capacity atrium to hold a greater volume of blood |
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Term
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Definition
- Encircles most of the heart
- Marks external boundary b/t the superior atria and inferior ventricles. |
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Term
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Definition
- Forms the right border of the heart -- Receives blood from three veins:
1. Superior vena cava
2. Inferior vena cava
3. Coronary sinus |
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Term
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Definition
| - Thin partition b/t right atrium and left atrium |
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Term
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Definition
- An oval depression
- Remnant of foramen ovale
- Opening in the interatrial septum of the fetal heart that normally closes soon after birth |
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Term
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Definition
- Blood passes from the right atrium into the right ventricle through a valve
- Consists of three leaflets or cusps
- Composed of dense connective tissue covered by endocardium |
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Term
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Definition
| - Forms most of the anterior surface of the heart |
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Term
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Definition
| - Tendonlike cords connected to the cusps of the tricuspid valve |
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Term
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Definition
| - Cone-shaped trabeculae carneae connected to chordae tendineae |
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Term
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Definition
| - Partition that separates right ventricle from the left ventricle |
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Term
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Definition
| - Blood passes from the right ventricle through pulmonary valve |
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Term
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Definition
- Receives blood from the lungs through four pulmonary veins.
- Like the right atrium, the inside of the left atrium has a smooth posterior wall.
- Because pectinate muscles are confined to the auricle of the left atrium, the anterior wall of the left atrium also is smooth. |
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Term
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Definition
| - Thickest chamber of the heart |
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Term
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Definition
| - Blood passes from the left ventricle through the aortic valve (aortic semilunar valve) into the ascending aorta |
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Term
| Myocardial Thickness and Function |
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Definition
- Thin-walled atria deliver blood under less pressure into the adjacent ventricles.
- Ventricles pump blood under higher pressure over greater distances, their walls are thicker
- Left is thicker b/c more work |
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Term
| Fibrous Skeleton of the Heart |
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Definition
- The heart wall also contains dense connective tissue
- Consists of four dense connective tissue rings that surround the valves of the heart
- Forming structural foundation for the heart valves
- Prevents overstretching of the valves as blood passes through them.
- Point of insertion for bundles of cardiac muscle fibers
- Acts as an electrical insulator between the atria and ventricles. |
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Term
| Atrioventricular (AV) Valves |
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Definition
- Lcated between an atrium and a ventricle, the tricuspid and bicuspid valves
- When open, the rounded ends of the cusps project into the ventricle.
- When ventricles relaxed, blood moves from a higher pressure in the atria to a lower pressure in the ventricles through open AV valves
- When the ventricles contract, the pressure of the blood drives the cusps upward until their edges meet and close the opening
- At the same time, the papillary muscles contract, which pulls on and tightens the chordae tendineae.
- Prevents the valve cusps from everting (opening into the atria) in response to the high ventricular pres- sure.
- If AV valves or chordae tendineae damaged, blood may regurgitate into the atria when the ventricles contract. |
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Term
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Definition
- Made up of three crescent moon–shape cusps
- Allow ejection of blood from heart into arteries
- Prevent backflow of blood into the ventricles. |
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Term
| Systemic and Pulmonary Circulations |
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Definition
- Two circuits are arranged in series:
- Output of one becomes the input
of the other |
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Term
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Definition
- Left side of the heart
- Receives bright red oxygenated (oxygen-rich) blood from the lungs
- Ultimately the blood flows back to the right atrium |
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Term
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Definition
- Right side of the heart is the pump
- Receives dark-red deox' blood returning from the systemic circulation.
- Blood ejected from the right ventricle -> pulmonary trunk -> Carry blood to the right and left lungs -> Unloads CO2 -> Exhaled, and picks up O2 from inhaled air -> freshly oxygenated blood then flows into pulmonary veins and returns to the left atrium. |
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Term
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Definition
| - Myocardium has own network of blood vessels |
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Term
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Definition
- Branch from ascending aorta and encircle the heart like a crown encircles the head
- While heart contracting, little blood flows in the coronary arteries because they are squeezed shut.
- Right and left coronary arteries, branch from ascending aorta and supply oxygenated blood to the myocardium |
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Term
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Definition
| - When heart relaxes,the high pressure of blood in the aorta propels blood through the coronary arteries, into capillaries, and then in coronary veins |
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Term
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Definition
| Most of the deoxygenated blood from the myocardium drains into a large vascular sinus in the coronary sulcus on the posterior surface of the heart |
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Term
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Definition
| The ends of cardiac muscle fibers connect to neighboring fibers by irregular transverse thickenings of the sarcolemma |
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Term
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Definition
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Term
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Definition
- Allow muscle action potentials to conduct from one muscle fiber to its neighbors.
- Allow the entire myocardium of the atria or the ventricles to contract as a single, coordinated unit |
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Term
| Autorhythmic Fibers: The Conduction System |
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Definition
- Source of electrical activity
- A network of specialized cardiac muscle fibers |
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Term
| Autorhythmic Fibers - Functions |
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Definition
1. Pacemaker
2. Cardiac Conduction System |
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Term
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Definition
| Setting rhythm of electrical excitation that causes contraction of the heart. |
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Term
| Cardiac Conduction System |
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Definition
- Network of specialized cardiac muscle fibers
- Provide path for each cycle of cardiac excitation to progress through the heart.
- Ensures cardiac chambers become stimulated to contract in a coordinated manner
- Makes the heart an effective pump. |
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Term
| (Step 1) Sinoatrial (SA) Node |
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Definition
- Each action potential from the SA node propagates throughout both atria via gap junctions in the intercalated discs of atrial muscle fibers.
- Following the action potential, the two atria contract at the same time. |
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Term
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Definition
- Do not have a stable resting potential.
- Repeatedly depolarize to threshold spontaneously.
- Where cardiac excitation begins |
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Term
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Definition
- Spontaneous depolarization of SA
- When reaches threshold, triggers an action potential. |
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Term
| (Step 2) Atrioventricular (AV) Node |
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Definition
- A/P reaches the atrioventricular (AV) node
- Located in the interatrial septum, just anterior to the opening of the coronary sinus
- At AV node, the A/P slows considerably as a result of various differences in cell structure in AV node.
- Delay provides time for atria to empty blood into ventricles. |
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Term
| (Step 3) Atrioventricular (AV) Bundle |
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Definition
- From the AV node, A/P enters AV bundle
- Only site where A/P's can conduct from the atria to the ventricles |
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Term
| (Step 4) Right & Left Bundle Branches |
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Definition
| - Bundle branches extend through the interventricular septum toward the apex of the heart |
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Term
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Definition
- Rapidly conduct A/P beginning at the apex of the heart upward to the remainder of the ventricular myocardium.
- Ventricles contract, pushing blood upward toward semilunar valves. |
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Term
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Definition
| - “Working” atrial and ventricular muscle fibers |
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Term
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Definition
| - Period of maintained depolarization. |
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Term
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Definition
| - Due to opening of voltage-gated slow Ca2+ channels in the sarcolemma |
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Term
| Voltage-gated Kﰓ+ Channels |
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Definition
- Voltage-gated K+ channels found in the sarcolemma of a contractile fiber.
- Just before the plateau phase begins, some of these K+ channels open, allowing potassium ions to leave the contractile fiber. Therefore, depolarization is sustained during the plateau phase because Ca2+ inflow just balances K+ outflow. |
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Term
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Definition
- Recovery of the resting membrane potential
- Outflow of K+ restores the negative resting membrane potential (-90 mV).
- Calcium channels closing |
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Term
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Definition
- Time interval during which a second contraction cannot be triggered
- Refractory period of cardiac muscle fiber lasts longer than the contraction itself.
- Another contraction cannot begin until relaxation is well under way. |
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Term
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Definition
| - As A/P propagate through heart, they gen' electrical currents that can be detected at the surface of the body |
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Term
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Definition
Possible to determine:
(1) if conducting pathway abnormal
(2) if the heart is enlarged
(3) if regions of heart damaged
(4) the cause of chest pai |
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Term
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Definition
- First
- Small upward deflection on the ECG
- Represents atrial depolarization, which spreads from the SA node through contractile fibers in both atria. |
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Term
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Definition
| - Begins as a downward deflection, continues as a large, upright, triangular wave, and ends as a downward wave |
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Term
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Definition
- Third wave is a dome-shaped upward deflection
- Smaller and wider than the QRS complex because repolarization occurs more slowly than depolarization. |
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Term
| Correlation of ECG Waves with Atrial and Ventricular Systole |
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Definition
| - The atria and ventricles depolarize and then contract at different times because the conduction system routes cardiac action potentials along a specific pathway. |
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Term
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Definition
| Refers to the phase of contraction |
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Term
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Definition
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Term
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Definition
- A single cardiac cycle includes all the events associated with one heartbeat.
- A cardiac cycle consists of systole and diastole of the atria plus systole and diastole of the ventricles. |
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Term
| Pressure and Volume Changes during the Cardiac Cycle |
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Definition
- The atria and ventricles alternately contract and relax, forcing blood from areas of higher pressure to areas of lower pressure.
- As a chamber of the heart contracts, blood pres-sure within it increases.
- Relation b/t the heart’s electrical signals (ECG) and changes in atrial pressure, ventricular pressure, aortic pressure, and ventricular volume during the cardiac cycle.
- Pressures on the right side considerably lower.
- Each ventricle expels same volume of blood per beat, and same pattern exists for both pumping chambers |
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Term
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Definition
- Lasts about 0.1 sec
- Atria contracting
- At same time, ventricles relaxed |
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Term
| End-diastolic Volume (EDV) |
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Definition
- Blood volume at the end of its relaxation period (diastole).
- Each ventricle contains about 130 mL |
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Term
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Definition
- Lasts about 0.3 sec
- Ventricles are contracting |
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Term
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Definition
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Term
| Isovolumetric Contraction |
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Definition
- Cardiac muscle fibers are contracting and exerting force but are not yet shortening.
- Muscle contraction is isometric (same length).
- B/C all four valves are closed, ventricular volume remains the same (isovolumic). |
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Term
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Definition
- Both SL valves open
- Ejection of blood from the heart begins.
- The period when the SL valves are open |
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Term
| End-systolic Volume (ESV). |
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Definition
- Left ventricle ejects about 70 mL of blood into the aorta and the right ventricle ejects same volume of blood into pulmonary trunk.
- The volume remaining in each ventricle at the end of systole, about 60 mL |
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Term
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Definition
- The volume ejected per beat fromeach ventricle, equals end-diastolic volume minus end-systolic volume: SV - EDV = ESV.
- At rest, the stroke volume is about 130 mL - 60 mL = 70 mL (a little more than 2 oz). |
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Term
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Definition
- Lasts about 0.4 sec, the atria and the ventricles are both relaxed.
- As the heart beats faster and faster, the relaxation period becomes shorter and shorter, whereas the durations of atrial systole and ventricular systole shorten only slightly. |
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Term
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Definition
- Caused by ventricular repolarization
- As the ventricles relax, pressure within the chambers falls, and blood in the aorta and pulmonary trunk begins to flow back-ward toward the regions of lower pressure in the ventricles.
- Backflowing blood catches in the valve cusps and closes the SL valves. |
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Term
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Definition
- After the SL valves close
- A brief interval when ventricular blood volume does not change because all four valves are closed. |
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Term
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Definition
- As ventricles continue to relax, pressure falls quickly.
- When ventricular pressure drops below atrial pressure, the AV valves open, and ventricular filling begins. -- The major part of ventricular filling occurs just after the AV valves open.
- Blood that has been flowing into and building up in the atria during ventricular systole then rushes rapidly into the ventricles.
- At the end of the relaxation period, the ventricles are about three-quarters full. The P wave appears in the ECG, signaling the start of another cardiac cycle. |
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Term
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Definition
- The sound of the heartbeat comes primarily from blood turbulence caused by the closing of the heart valves.
- Smoothly flowing blood is silent |
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Term
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Definition
- The first sound (S1)
- Louder and longer than second sound.
- Caused by blood turbulence associated with closure of the AV valves soon after ventricular systole begins. |
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Term
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Definition
- Second sound (S2)
- Shorter and not as loud as the first
- Caused by blood turbulence associated with closure of the SL valves at the beginning of ventricular diastole |
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Term
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Definition
he volume of blood ejected from left ventricle (or right ventricle) into the aorta (or pulmonary trunk) each minute.
- Cardiac output equals stroke volume (SV), the volume of blood ejected by the ventricle during each contraction, multiplied by the heart rate (HR) |
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Term
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Definition
- The difference between a person’s maximum cardiac output and cardiac output at rest.
- The average person has a cardiac reserve of four or five times the resting value. |
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Term
| Regulation of Stroke Volume |
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Definition
- A healthy heart will pump out the blood that entered its chambers during the previous diastole.
- If more blood returns to the heart during diastole, then more blood is ejected during the next systole.
1. Preload
2. Contractility
3. Afterload |
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Term
| Preload: Effect of Stretching |
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Definition
- A greater preload (stretch) on cardiac muscle fibers prior to contraction increases their force of contraction.
- Stretching of a rubber band. The more the rubber band is stretched, the more forcefully it will snap back.
- Within limits, the more the heart fills with blood during diastole, the greater the force of contraction during systole. |
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Term
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Definition
| - The volume of blood returning to the right ventricle. |
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Term
| Frank–Starling law of the heart |
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Definition
| - When venous return increases, a greater volume of blood flows into ventricles, and EDV is increased. |
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Term
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Definition
- Second factor that influences stroke volume is myocardial contractility
- The stength of contraction at any given preload |
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Term
| Positive Inotropic Agents |
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Definition
| - Substances that increase contractility |
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Term
| Negative Inotropic Agents |
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Definition
| - Substances that decrease contractility |
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Term
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Definition
- The pressure that must be overcome before a semilunar valve can open is termed
- An increase in after- load causes stroke volume to decrease, so that more blood remains in the ventricles at the end of systole |
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Term
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Definition
| Among the several factors that contribute to regulation of heart rate, the most important are the autonomic nervous system and hormones released by the adrenal medullae (epinephrine and norepinephrine) |
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Term
| Autonomic Regulation of Heart Rate |
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Definition
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Term
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Definition
- In the medulla oblongata
- Receives input from a variety of sensory receptors and from higher brain centers, such as limbic system and cerebral cortex.
- Directs appropriate output by increasing or decreasing the frequency of nerve impulses in both the sympathetic and parasympathetic branches of the ANS |
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Term
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Definition
- Monitor position of limbs and muscles
- Send nerve impulses at an increased frequency to the cardiovascular center.
- Major stimulus for the quick rise in heart rate that occurs at the onset of physical activity |
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Term
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Definition
| Monitor chemical changes in the blood |
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Term
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Definition
- Monitor stretching of major arteries and veins caused by pressure of the blood flowing through them.
- NP receptors located in the arch of the aorta and in the carotid arteries blood pressure and provide input to the cardiovascular center when it changes. |
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Term
| Cardiac Accelerator Nerves |
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Definition
- Extend out to the SA node, AV node, and most portions of myocardium.
- Impulses in cardiac accelerator nerves trigger the release of norepinephrine, |
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Term
| Two Separate Effects of Cardiac Accelerator Nerves (1st) |
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Definition
| (1) In SA (and AV) node fibers, norepinephrine speeds the rate of spontaneous depolarization so that these pacemakers fire impulses more rapidly and heart rate increases; |
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Term
| Two Separate Effects of Cardiac Accelerator Nerves (2nd) |
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Definition
| Contractile fibers throughout the atria and ventricles, norepinephrine enhances Ca2+ entry through the voltage-gated slow Ca2 |
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Term
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Definition
- Parasympathetic nerve impulses reach the heart via the right and left vagus (X) nerves
- Release acetylcholine, which decreases heart rate by slowing the rate of spontaneous depolarization in autorhythmic fibers. |
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Term
| Chemical Regulation of Heart Rate |
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Definition
| Several hormones and cations have major effects on the heart |
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Term
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Definition
| Epinephrine and norepinephrine (from the adrenal medullae) enhance the heart’s pumping effectiveness. |
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Term
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Definition
- Relative concentrations of three cations — K+, Ca2+, and Na+ — have a large effect on cardiac function.
- Elevated blood levels of K+ or Na+ decrease heart rate and contractility.
- Excess Na+ blocks Ca2+ inflow during cardiac action potentials, thereby decreasing the force of contraction
- Excess K+ blocks generation of action poten- tials.
- A moderate increase in interstitial (and thus intracellular) Ca2+ level speeds heart rate and strengthens the heartbeat. |
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Term
| Other Factors in Heart Rate Regulation |
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Definition
| Age, gender, physical fitness, and body temperature also influ- ence resting heart rate. |
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