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Questions and Answers
The pericardium is a single layer of tissue that surrounds the heart.
False
The superior and inferior venae cavae are vessels that convey blood away from the heart.
False
The right and left pulmonary veins return oxygenated blood to the heart.
True
The ascending aorta has four branches.
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The marginal artery is a vessel that supplies blood to the heart.
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The great cardiac vein is a vessel that drains blood from the heart.
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The anterior interventricular artery is a vessel that returns blood to the heart.
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The right coronary artery is located in the atrioventricular groove.
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The small cardiac vein is a vessel that conveys blood away from the heart.
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The circumflex artery is a vessel that supplies blood to the heart.
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Study Notes
Cardiac Cycle
- The cardiac cycle refers to all events associated with blood flow through the heart
- It consists of systole (contraction of heart muscle) and diastole (relaxation of heart muscle)
- Phases of the cardiac cycle:
- Ventricular filling (mid-to-late diastole): heart blood pressure is low as blood enters atria and flows into ventricles
- Atrial systole: AV valves are open, then atrial systole occurs
- Ventricular systole (contraction): atria relax, rising ventricular pressure results in closing of AV valves, isovolumetric contraction phase, and ventricular ejection phase opens semilunar valves
- Isovolumetric relaxation (early diastole): ventricles relax, backflow of blood in aorta and pulmonary trunk closes semilunar valves, and dicrotic notch – brief rise in aortic pressure caused by backflow of blood rebounding off semilunar valves
Heart Physiology
- Heart Physiology: Intrinsic Conduction System
- Autorhythmic cells: initiate action potentials, have unstable resting potentials called pacemaker potentials, and use calcium influx (rather than sodium) for rising phase of the action potential
- Heart Physiology: Sequence of Excitation
- Sinoatrial (SA) node generates impulses about 75 times/minute
- Atrioventricular (AV) node delays the impulse approximately 0.1 second
- Impulse passes from atria to ventricles via the atrioventricular bundle (bundle of His) and splits into two pathways in the interventricular septum (bundle branches)
Cardiac Output and Reserve
- Cardiac Output (CO) is the amount of blood pumped by each ventricle in one minute
- CO is the product of heart rate (HR) and stroke volume (SV)
- HR is the number of heart beats per minute
- SV is the amount of blood pumped out by a ventricle with each beat
- Cardiac reserve is the difference between resting and maximal CO
Regulation of Stroke Volume
- SV = end diastolic volume (EDV) minus end systolic volume (ESV)
- EDV = amount of blood collected in a ventricle during diastole
- ESV = amount of blood remaining in a ventricle after contraction
- Factors affecting stroke volume:
- Preload – amount ventricles are stretched by contained blood
- Contractility – cardiac cell contractile force due to factors other than EDV
- Afterload – back pressure exerted by blood in the large arteries leaving the heart
Frank-Starling Law of the Heart
- Preload, or degree of stretch, of cardiac muscle cells before they contract is the critical factor controlling stroke volume
- Slow heartbeat and exercise increase venous return to the heart, increasing SV
- Blood loss and extremely rapid heartbeat decrease SV
Extrinsic Factors Influencing Stroke Volume
- Contractility is the increase in contractile strength, independent of stretch and EDV
- Increase in contractility comes from:
- Increased sympathetic stimuli
- Certain hormones
- Ca2+ and some drugs
- Agents/factors that decrease contractility include:
- Acidosis
- Increased extracellular K+
- Calcium channel blockers
Regulation of Heart Rate
- Positive chronotropic factors increase heart rate
- Caffeine
- Negative chronotropic factors decrease heart rate
- Sedatives
- Regulation of Heart Rate: Autonomic Nervous System
- Sympathetic nervous system (SNS) stimulation is activated by stress, anxiety, excitement, or exercise
- Parasympathetic nervous system (PNS) stimulation is mediated by acetylcholine and opposes the SNS
- PNS dominates the autonomic stimulation, slowing heart rate and causing vagal tone
- If the Vagus Nerve was cut, the heart would lose its tone
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Description
Test your knowledge of the external heart anatomy, including vessels that supply and drain the heart, as well as the structure and function of the atria. Identify key arteries, veins, and features of the heart's posterior view. Get ready to ace this quiz!
