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P & A Cardiovascular System

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P & A Notes Cardiovascular System

February 07, 2011

Cardiovascular System 

*Heart- About the size of your fist.
- Located in the pericardial cavity.
- Covered by a membrane...pericardium.
- Has four chambers: Two upper chambers are called atria (single atrium). They receive the blood from the veins. Two lower chambers called the ventricles. They force the blood out of the heart into the arteries.

Septum- Muscular wall that separates the atrium and ventricle on the right from those on the left.

-Right atrium receives blood from the superior and inferior vena cava which drains blood from the head, shoulders and lower part of the body. It also receives blood from a smaller coronary sinus which drains the walls of the heart.


- The right ventricle isn’t as heavily muscled as the left because it only has to pump the blood to the lungs. The left ventricle pumps blood into the aorta-> body

(Know the Blood flow through heart)
see handout

-Right side of heart will have blood that is low in oxygen. Left side will be high in oxygen.

-Tissues of the heart need a blood supply. The first two branches off the aorta do this. They are the right and left coronary arteries. The muscles of the heart must have a constant fresh blood supply. These arteries break down to arterioles and then to the capillaries (where food, waste, and gasses are exchanged), these join to form larger ventricles and then veins. These cardiac veins join forming the coronary sinus that dumps into the right atrium.


-During the cardiac cycle pressures in the chambers will rise and fall; when the atria contract they force blood into the ventricles. Atrial pressure rises (atrial systole). Then the atrium will relax and fill with blood (atrial diastole). When the ventricles contract they push blood into the arteries, causing a rise in pressure (ventricle systole). When the ventricles relax and fill with blood there is less pressure in the arteries. (ventricular diastole).

-Doctors use an instrument called a “Sphygmomanometer” to check your blood pressure.
120--> systolic
over 180--> diastolic


-Senatorial node (S-A node) is a small mass of muscle tissue located on the back wall of the right atrium. The cells of the S-A node initiates the impulse that causes the right and left atrium to contract at almost the same time, about 70-80 times a minute.


S-A node is also called the pacemaker. It then stimulates the atrioventricular node (A-V node), which in turn stimulates the ventricles to contract.

An electrocardiogram (ECG) is a recording of the electrical changes during the cardiac cycle.

Regulation of the heart rate is controlled by the Medulla Oblongata.

-Parasympathetic nerve fibers that go to the S.A. and A.V. nodes release acetylcholine. (slows heart rate).

-Sympathetic nerve fibers that go to the S.A. and A.V. nodes secrete norepinephrine. (increases heart rate).

- Cardiovascular system is a closed system of tubes. Tubes that move blood away from the heart are called arteries-which branch into arterioles-branch into capillaries.

-Every cell in your body is very close to a capillary. Capillaries come together to form veinules. (moving toward the heart.) -These join to form veins.

Arteries- Are elastic, which allows them to take the pressure of blood moving out of the heart. Arteries have more muscle in their walls than veins, making them thicker.

All vessels except capillaries have muscles in their walls which aid in maintenance of blood pressure, and blood flow. Vasoconstriction and Vasodilatation.

Capillaries- Smallest vessels. Walls are semipermeable. At the entrance of capillaries is a muscle called the precapillary sphincter. When the cells need O2 and Nutrients which are supplied by that capillary the sphincter relaxes. When the need is met, the sphincter will contract again.

Diffusion, Osmosis, Filtration,-- ways material move out of capillaries. Diffusion is the main method.

--Why don’t plasma proteins move into the interstitial fluid?

Venules- Capillaries merge to form venues.
Venules merge to form veins.
-Move blood back to heart
-Run pretty much parallel to arteries
-Fairly thin walled. Have less smooth muscle and less elastic tissue than arteries do.
-Many veins, especially those in arms and legs, have valves. Valves open as long as blood flow is toward the heart, and it closes if it tries to back up.
-When there is a hemorrhage and a drop in blood pressure, the muscular walls in the veins constrict causing a rise in blood pressure. This ensures normal blood flow even when as much as 25% of the blood volume is lost.


C6H12O6+ 6O2---->6CO2+6H2O+energy

-What is circulatory systems role in above formula?
-Explain why heart rate increases when we exercise.

-Know at least three differences between arteries and veins.


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