1. CHAPTER 11 - THE CARDIOVASCULAR SYSTEM Anatomy and Physiology

2. Closed system (double – looped circulation) In one day pushes total volume of our blood (6 quarts) through our blood vessels over 1000 times, which means it pumps about 6000 quarts of blood a day. Beats, on average, 75 beats per minute. Made up of: a. Heart – pumps blood b. Blood vessels - allow blood to circulate to all parts of the body  Arteries – carry blood away from heart  Veins – carry blood to the heart  Capillaries – minute blood vessel connecting arteries to veins; gas exchange in body takes place here Main function – transportation system to deliver oxygen, nutrients, cell wastes, hormones, and other substances vital for body homeostasis to and from the cells. Heart provides the force for this travel. Location  Thorax between the lungs  Pointed apex directed toward left hip  Great vessels emerge from the broader base, points toward right shoulder and lies beneath 2 nd rib. About the size of your fist  Hollow  Cone-shaped  Rests on diaphragm

3. The Heart: Coverings Pericardium – a double serous membrane Visceral pericardium (epicardium)  Next to heart tightly hugging it, part of heart wall Parietal pericardium  Outside layer that protects heart and anchors it to surrounding structures like diaphragm and sternum Serous fluid – slippery lubricating fluid that fills the space between the layers of pericardium. It allows heart to beat easily in a frictionless environment and the pericardial layers can slide smoothly by each other. PERICARDITIS – inflammation of pericardium, results in a decrease in amount of serous fluid. Pericardial layers bind and stick to one another forming painful adhesions that interfere with heart movement.

4. Internal Heart Anatomy The Heart: Heart Wall Three layers 1. Epicardium (already described)  Outside layer  This layer is the parietal pericardium  Connective tissue layer 2. Myocardium  Middle layer  Mostly cardiac muscle  Layer that actually contracts 3. Endocardium  Inner layer  Endothelium, very thin, lines heart chambers.

5. The Heart: Chambers Right and left side act as separate pumps Four hollow chambers lines with endocardium 2 upper chambers: (Atria)  Receiving chambers  Right atrium  Left atrium 2 lower chambers: (Ventricles) Discharging chambers  Right ventricle  Left ventricle Interventricular septum – wall that divides the heart longitudinally Heart is single organ, but a double pump (double circulation)

6. Right side of heart – pulmonary (lungs) circuit pump. Receives oxygen-poor blood from veins of the body Superior and Inferior vena cava – veins of the body that oxygen-poor blood passes through into the right atrium Pulmonary trunk – splits into right and left pulmonary arteries that then carry blood from right ventricle to lungs (blood is releasing CO 2 & picking up O 2 Pulmonary circulation – blood traveling from right side of heart to lungs and back to left side of heart. Left side of heart – systemic (body) circuit pump. Receives oxygen-rich blood from the veins of lungs. Right and Left pulmonary veins – veins of the lungs that oxygen-rich blood passes through into the left atrium Aorta (major artery of the heart) Clean blood leaves the left ventricle by way of this artery and from which the systemic arteries branch to supply essentially all body tissues with oxygen and nutrients Systemic circulation – blood traveling from left side of heart to body and back to right side of heart

8. Operation of Heart Valves  Allow blood to flow in only one direction – valve opens as blood is pumped through  Four valves in heart  Atrioventricular valves (AV valves) – between atria and ventricles; prevents backflow into the atria when the ventricles contract  Bicuspid valve (left AV valve); also called the “mitral “valve”; made up of 2 cusps made of endocardium  Tricuspid valve (right AV valve)  Chordae tendineae – “heart strings” - tiny white cords that anchor the cusps to the walls of the ventricles.  Semilunar valves - between ventricle and artery – guards the bases of the 2 large arteries leaving the ventricular chambers.  Pulmonary semilunar valve – 3 cusps, fit tightly together when valves are closed  Aortic semilunar valve – 3 cusps, tight fit also

9. Each set of valves operates at a different time.  The AV valves open during heart relaxation and close when ventricles are contracting.  Semilunar valves close during heart relaxation and forced open when the ventricles contract.  Valves force blood to continually move forward in its journey through the heart. http://highered.mheducation.com/sites/0072495855/student_view0/chapter22/ani mation__the_cardiac_cycle__quiz_2_.html

10. Problems with heart valves Valvular stenosis – valve flaps become stiff due to repeated bacterial infection of the endocardium – causes the heart to contract more vigorously than normal increasing the workload of the heart, ultimately weakening the heart and causing it to fail. Under these conditions, the faulty valve is replaced with a synthetic valve or a valve taken from a pig. The Heart: Associated Great Vessels Great vessels is a term used to refer collectively to the large vessels that bring blood to and from the heart.  Aorta - Leaves left ventricle  Pulmonary arteries - Leave right ventricle  Vena cava - Enters right atrium  Pulmonary veins (four) - Enter left atrium

11. Coronary Circulation Blood in the heart chambers does not nourish the myocardium (the cardiac muscle layer of the heart wall)  The heart has its own nourishing circulatory system  Coronary arteries – (oxygenated blood) branches from aorta and encircles the heart in the atrioventricular groove at the junction of the atria and ventricles. The coronary arteries and their major branches are compressed when the ventricles are contracting and fill when heart is relaxed  Cardiac veins - Myocardium is drained by several cardiac veins, which empty into an enlarged vessel on the backside of the heart called the coronary sinus  Coronary sinus - blood empties into the right atrium via the coronary sinus When the heart beats too rapidly, the myocardium may receive an inadequate blood supply due to shorten periods of relaxation keeping good quantities of blood from flowing into heart tissue. When the myocardium is deprived of oxygen, a crushing chest pain can occur. This is called ANGINA. This pain is a warning and if prolonged attacks are ignored, the ischemic heart cells may die forming an INFARCT. The resulting myocardial infarction is commonly called a HEART ATTACK or CORONARY.

12. The Heart: Conduction System Heart muscle cells contract, without nerve impulses, in a regular, continuous way. Atrial cells beat 60 times per minute, ventricular cells contract much more slowly (20-40 bpm). A unifying control system gets the beating into a rhythm. Intrinsic conduction system (nodal system)  Special tissue built into the heart that sets the pace. Cross between muscle and nervous tissue. Coordinates beats and averages about 75 beats per minute.  Sinoatrial node (most important) - PACEMAKER – crescent-shaped. Located in the right atrium. Starts each heart beat (contraction is initiated by the sinoatrial node) and sets the pace for the whole heart.  Atrioventricular node - found at the junction of the atrias and ventricles. Impulse travels from SA node to here  Atrioventricular bundle - located in interventricular septum. Impulse, after brief pause to let atria fill, travels here  Bundle branches - also located in interventricular septum. Impulse travels here from atrioventricular bundle  Purkinje fibers - spread within the muscle of the ventricle wall. Contraction of ventricle begins at heart apex and moves toward atria.  Sequential stimulation occurs at other auto rhythmic cells

13. highered.mheducation.com/sites/0072495855/student_view0/chapter22/animation

14. Damage to the nodal system: ISCHMEIA – lack of an adequate blood supply to the heart muscle, may lead to FIBRILLATION – a rapid uncoordinated shuddering of heart muscle. Fibrillation makes the heart totally useless as a pump and is a major cause of death from heart attacks in adults TACHYCARDIA – is a rapid heart rate (over 100 bpm). BRADYCARDIA – heart rate substantially slower than normal (less than 60bpm). Prolonged tachycardia may progress to fibrillation. Cardiac Cycle and Heart Sounds: SYSTOLE and DIASTOLE means heart contraction and relaxation, respectively. Since ventricles do most of the work, these terms refer to the contraction/relaxation of the ventricles. CARDIAC CYCLE – events of one complete heartbeat, during which both atria and ventricles contract and then relax (0.8 second).  Atria contract simultaneously  Atria relax, then ventricles contract  Systole = contraction  Diastole = relaxation

15. HEART SOUNDS: 2 distinct sounds can be heard during each cardiac cycle: “lub-dub” a. “lub” – caused by closing of the AV valves b. “dub” – occurs when semilunar valves close at the end of systole. MURMURS – Abnormal heart sounds. Can indicate valve problems. Common in children, older adults.

16. The Heart: Cardiac Cycle  Cardiac cycle – events of one complete heart beat  Mid-to-late diastole – blood flows into ventricles  Ventricular systole – blood pressure builds before ventricle contracts, pushing out blood  Early diastole – atria finish re-filling, ventricular pressure is low The Heart: Cardiac Output  Cardiac output (CO)  Amount of blood pumped by each side of the heart in one minute  CO = (heart rate [HR]) x (stroke volume [SV])  Stroke volume  Volume of blood pumped by each ventricle in one contraction

17. Cardiac Output Regulation

18. The Heart: Regulation of Heart Rate  Stroke volume usually remains relatively constant  Starling’s law of the heart – the more that the cardiac muscle is stretched, the stronger the contraction  Changing heart rate is the most common way to change cardiac output The Heart: Regulation of Heart Rate  Increased heart rate  Sympathetic nervous system  Crisis  Low blood pressure  Hormones  Epinephrine  Thyroxine  Exercise  Decreased blood volume  Decreased heart rate  Parasympathetic nervous system  High blood pressure or blood volume  Decreased venous return