IB TOPIC 6.2 THE BLOOD SYSTEM
TERMS TO KNOW circulation ventricle artery vein THE BLOOD SYSTEM 6.2.U1 - Arteries convey blood at high pressure from the ventricles to the tissues of the body Circulation William Harvey - mid 1600 s systemic blood network arteries - veins -
TERMS TO KNOW atrium myocardium THE BLOOD SYSTEM The mammalian (and avian) heart has 4 chambers 2 atria: collect blood on its return 2 ventricles pump blood out 2 separate circuits right (pulmonary) from body, to lungs left (systemic) from lungs to body thicker myocardium. Why?
CIRCULATION OF BLOOD
TERMS TO KNOW lumen THE BLOOD SYSTEM Arteries have specialized structures: narrow lumen to maintain ~80-120mmHg pressure thick wall with connective tissue 6.2.U2: inner layer of muscle and connective (elastic) tissue
TERMS TO KNOW THE BLOOD SYSTEM 6.2.U3: muscle and elastic fibers assist in maintaining blood pressure between pumping cycles muscle withstands high pressure can contract and narrow the lumen to maintain pressure elastic fibers allow wall to stretch and then recoil
THE BLOOD SYSTEM 6.2.U4: Blood flows through tissues in capillaries. Capillaries have permeable walls that allow exchange of materials between tissue and blood one layer of (thin, leaky) endothelial tissue lowest pressure (greatest area)
THE BLOOD SYSTEM 6.2.U5: veins collect blood low pressure holds most of a resting person s blood thinner than arteries takes blood back to atria if low pressure, how does blood get moved? valves prevent back flow
TERMS TO KNOW pulmonary THE BLOOD SYSTEM 6.2.U7: separate circuit for the lungs double circulation pulmonary circulation why must blood from lung capillaries go back to heart to be pumped again to body? systemic circulation
The Mammalian Heart: Pulmonary artery Aorta Can you ID the following? Anterior vena cava Pulmonary artery AV Valves Semilunar Valves Chambers Right atrium Pulmonary veins Semilunar valve Atrioventricular valve Left atrium P Semilunar valve Atrioven val Veins, Arteries Figure 42.6 Posterior vena cava Right ventricle Left ventricle
Mammalian Heart Pulmonary artery Aorta Anterior vena cava Pulmonary artery Right atrium Left atrium Pulmonary veins Pulmonary veins Semilunar valve Right AV valve tricuspid valve Semilunar valve Left AV valve bicuspid valve mitral valve Figure 42.6 Posterior vena cava Right ventricle Left ventricle
Cardiac Cycle Systole The contraction, or pumping, phase of the cycle Diastole The relaxation, or filling, phase of the cycle http://www.digitallyobsessed.com/heartbeat/images/heart.gif
The Cardiac Cycle Semilunar valves closed 2 Atrial systole; ventricular diastole 0.4 sec 0.1 sec 0.3 sec Semilunar valves open AV valves open Figure 42.7 1 Atrial and ventricular diastole AV valves closed 3 Ventricular systole; atrial diastole Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Cardiac muscle is self excitable Rate and timing of cardiac contraction is set by: sinoatrial (SA) node, or pacemaker Impulses go: SA node -> atrioventricular (AV) node Delayed at the AV node Then travel to the Purkinje fibers (make the ventricles contract) Cardiac Cycle The heartbeat is initiated at the SA node
ECG 1 Pacemaker generates wave of signals to contract. 2 Signals are delayed at AV node. 3 Signals pass to heart apex. 4 Signals spread Throughout ventricles. SA node (pacemaker) AV node Bundle branches Heart apex Purkinje fibers ECG Figure 42.8
Pacemaker The pacemaker is influenced by nerves (1 inc, 1 dec) hormones (epinephrine: fight or flight) body temperature and exercise
Blood Pressure BP = hydrostatic pressure that blood exerts against the wall of a vessel BP value = Systolic/Diastolic Systolic pressure Is the pressure in the arteries during ventricular systole Is the highest pressure in the arteries Diastolic pressure Is the pressure in the arteries during diastole Is lower than systolic pressure BP is due to both cardiac output, and arteriole constriction
1 Blood Pressure A typical blood pressure reading for a 20-year-old is 120/70. The units for these numbers are mm of mercury (Hg); a blood pressure of 120 is a force that can support a column of mercury 120 mm high. 4 The cuff is loosened further until the blood flows freely through the artery and the sounds below the cuff disappear. The pressure at this point is the diastolic pressure remaining in the artery when the heart is relaxed. Blood pressure reading: 120/70 Pressure in cuff above 120 Pressure in cuff below 120 Pressure in cuff below 70 Rubber cuff inflated with air 120 120 70 Artery Sounds audible in stethoscope Sounds stop Artery closed 2 A sphygmomanometer, an inflatable cuff attached to a pressure gauge, measures blood pressure in an artery. The cuff is wrapped around the upper arm and inflated until the pressure closes the artery, so that no blood flows past the cuff. When this occurs, the pressure exerted by the cuff exceeds the pressure in the artery. 3 A stethoscope is used to listen for sounds of blood flow below the cuff. If the artery is closed, there is no pulse below the cuff. The cuff is gradually deflated until blood begins to flow into the forearm, and sounds from blood pulsing into the artery below the cuff can be heard with the stethoscope. This occurs when the blood pressure is greater than the pressure exerted by the cuff. The pressure at this point is the systolic pressure. Figure 42.12
Cardiovascular Disease CV diseases Are disorders of the heart and the blood vessels > half the deaths in the United States
Atherosclerosis Connective tissue Smooth muscle Endothelium Plaque (a) Normal artery (b) Partly clogged artery 50 µm 250 µm Figure 42.18a, b
CV Diseases Hypertension, or high blood pressure Promotes atherosclerosis and increases the risk of heart attack and stroke A heart attack Death of cardiac muscle tissue from blockage of one or more coronary arteries A stroke Death of nerve tissue in the brain, from rupture or blockage of arteries in the head