Heart & Circulatory System General Information Part 2

IV. Heart Anatomy

a. Located between two lungs

b. Muscular pump

c. Four-chambers

d. Upper chambers - atrium; receive blood returning to heart

e. Lower chambers - ventricles; thicker, muscular walls that allow them to pump blood throughout the body

f. Flaps of tissue in heart called valves (such as tricuspid, mitral/bicuspid, pulmonary valves) prevent blood from flowing the wrong direction

 --> Heartbeat is the valves opening and closing

 a. Pacemaker sets rate at which heart contracts (located in wall of right atrium)

b. Pacemaker generates electrical impulses that spread quickly over walls of both atria, causing the contraction

c. Impulses spread to AV node, and then to the ventricles, causing them to contract

d. Contractions of ventricles causes blood spreading all over the body

e. Pacemaker creates rhythmic heartbeats

 - Diastole (atria and ventricles relaxed, allowing blood from veins to enter heart)

 - Systole (atria first contracts, blood forced into ventricles, which are relaxed. Then the ventricles contract, pumping blood into arteries, while the atria are relaxed)

f. Cardiac defibrillator (artificial pacemaker for if the pacemaker stops functioning)

VI. Blood Pressure

a. Systolic pressure - highest recorded pressure in an artery when the ventricles contract

b. Diastolic pressure - lowest recorded pressure in an artery during the relaxation phase of the heartbeat

c. 120/70 is normal for an adult

VII. Make-up of Blood

a. Plasma - 55% of blood is plasma, 45% red blood cells. Plasma = 90% water, 10% dissolved salts, proteins, and other transported substances

b. Red Blood Cells - carries oxygen from lungs to all tissues of the body. Contains hemoglobin, protein storing oxygen for delivery to cells (oxygen binds to iron in hemoglobin). Produced in bone marrow, as they mature, nuclei and mitochondria lost. Structure provides increased surface area for oxygen transfer. Average lifespan of 100-120 days

c. White Blood Cells - leukocytes. Have nuclei and mitochondria and are responsible for fighting infection and preventing cancer growth. Action takes place in interstitial fluid.