1. Cardiovascular System
Chapter 13

2. Cardiovascular System
At rest, the heart pumps about 7,000 liters of blood through the body each day (contracting about 2.5 million times in the average lifetime)
1850 gallons = 925 gallons of milk
3 parts:
Heart
Blood vessels
Blood
2 closed pathways:
Pulmonary circuit: sends oxygen-poor blood to the lungs to pick up oxygen and unload carbon dioxide
Systemic circuit: sends oxygen-rich blood to all body cells and removes waste

3. Structure of the Heart Average adult heart—14 cm long and 9 cm wide
Bordered by the lungs, lies anterior to the vertebral column and posterior to the sternum
Pericardium: membranous sac that encloses the heart
Innermost layer called the visceral pericardium (covers the heart)
Middle layer called the parietal pericardium
Between the two is called the pericardial cavity (contains fluid that reduces friction between the membrane and the heart)

4. Pericardium

5. Wall of the Heart 3 distinct layers:
Epicardium (visceral pericardium)—reduces friction between the pericardium and the heart
Myocardium—consists of muscle tissue that pumps blood out of the heart chamber
Endocardium—contains elastic fibers, blood vessels and specialized muscle fibers

6. Heart Chambers Internally, the heart is divided into four chambers:
Two upper atria (plural for atrium)
Two lower ventricles
Solid, wall-like septum separates the left side of the heart and the right side of the heart
Blood from one side of the heart never mixes with blood from the other side
Atrioventricular valve (AV valve) on the right and left of the heart ensure one-way blood flow between the atrium and ventricle on each side

7. Heart Valves
Vena cavas (superior and inferior) bring deoxygenated blood to the right atrium
Tricuspid valve lies between the right atrium and right ventricle
Pulmonary valve lies between the right ventricle and pulmonary trunk
Pulmonary trunk receives blood from the right ventricle, separates into pulmonary arteries that lead to the lungs

8. Heart valves
Pulmonary veins deliver blood to the left atrium from the lungs (2 from the right and 2 from the left)
Mitral valve lies between the left atrium and left ventricle (also called the bicuspid valve)
Aortic valve lies between the left ventricle and the aorta
Aorta large artery that receives blood from the left ventricle

11. Heart Actions Functions in a coordinated fashion
While the atria contract, the ventricles relax
While the ventricles contract, the atria relax
Both atria and ventricles relax for a brief time
This series of events constitutes a complete heartbeat, or cardiac cycle

12. Heart Actions
Pressure changes in the heart chambers open and close the valves
Pressure within the heart fluxuates depending on which valves should be open for blood flow

13. Heart Sounds
The sound of a heart beat are due to vibrations in the heart tissues when the valves close
First part—when ventricles contract & AV valves close
Second part—when ventricles relax & pulmonary and aortic valves close

14. Electrocardiogram
An electrocardiogram (ECG/EKG) is a recording of the electrical changes in the myocardium (muscle layer of the wall of the heart)
The pattern is generated as action potentials stimulate cardiac muscle cells to contract

15. EKG

16. Heart Rates
Tachycardia is an abnormally fast heartbeat (more than 100 beats per minute)
Bradycardia is a slow heart rate (less than 60 per minute); may occur during sleep
Body temperature, certain drugs, heart disease can all affect heart rate

17. Blood Vessels
Closed circuit of tubes that carries blood from the heart to the body cells and back
Vessels include:
Arteries—strong, elastic vessels adapted for transporting blood away from the heart under relatively high pressure

18. Blood Vessels Vessels include:
Arterioles—small branch of an artery that communicates with a capillary network
Capillaries—smallest blood vessels that connect to arterioles and allow for exchange of nutrients and waste

19. Blood Vessels Vessels include:
Venules—vessel that transports blood from capillaries to veins
Veins—transport blood back to the atria and follow pathways that roughly parallel those of arteries

20. Blood Pressure
Force blood exerts against the inner walls of the blood vessels
Commonly refers to the pressure in arteries supplied by branches of the aorta

21. Arterial Blood Pressure
Rises and falls in a pattern corresponding to the phases of the cardiac cycle
Contraction of the ventricles squeezes blood out and into the pulmonary trunk and aorta which increases the pressure in these arteries
Maximum pressure during ventricular contraction is called the systolic pressure

22. Arterial Blood Pressure
When the ventricles relax:
Arterial pressure drops
Lowest pressure that remains in the arteries before the next ventricular contraction is called diastolic pressure

23. Pulse
The surge of blood entering the arteries during ventricular contraction expands the arterial walls
Pressure begins to drop almost immediately as contraction ends, and the arterial walls recoil
The alternating expanding and recoiling of arteries can be felt as a pulse

24. Factors the Influence Blood Pressure
Cardiac Output
The volume of blood pushed out from the ventricle per minute
If volume or heart rate increases, cardiac output increases = blood pressure increases

25. Factors the Influence Blood Pressure
Blood Volume
The sum of the formed elements and plasma in the vascular system
Blood pressure is directly proportional to blood volume in the system

26. Factors the Influence Blood Pressure
Peripheral Resistance
Force of friction between blood and the walls of the blood vessels
Blood pressure must overcome peripheral resistance if the blood is to continue flowing

27. Factors that Influence Blood Pressure
Blood Viscosity:
Difficulty with which the molecules of a fluid flow past one another
The greater the viscosity, the greater the greater the resistance to flow

28. Control of Blood Pressure
Blood pressure = Cardiac Output x Peripheral Resistance
Both cardiac output and peripheral resistance are controlled in part by baroreceptor reflexes
Baroreceptors are receptors that that sense changes in blood pressure
If arterial pressure increases, baroreceptors send impulses to the brain to decrease heart rate