11.2 Structure and Function of the Heart Hollow organ located between your lungs made mostly of muscle Pumps oxygen-poor blood to your lungs and oxygen-rich blood to your entire body When the heart contracts blood is pumped out and when your heart relaxes blood enters the heart For the average person at rest, the entire process of pumping and filling the heart takes _________ this is known as the cardiac cycle 0.8 seconds

The pericardium is a protective sac that encloses the heart Filled with fluid that lubricates the surface of the heart and roots of the major blood vessels Humans and other mammals have a four chambered heart comprised of the: Right Atrium Right Ventricle Left Atrium Left Ventricle

Atria Ventricles The two upper chambers Receive blood returning to the heart Pump the blood into the ventricles Contain thin walls Ventricles The two lower chambers Receive blood from atria Pump the blood out of the heart Contain thick muscular walls

Valves in the heart prevent blood from flowing backward The valves located between the atria and ventricles are called atrioventricular valves left atrium to left ventricle = left atrioventricular valve AKA bicuspid valve (or mitral valve) right atrium to right ventricle = right atrioventricular valve AKA tricuspid valve The valves located between the ventricles and the arteries are called semilunar valves left ventricle to aorta = aortic valve right ventricle to pulmonary artery = pulmonary valve

With each heartbeat the valves open allowing blood to flow through Then the valves close preventing blood from flowing back When the valves close they cause the familiar “lub dub” sound of the heart The “lub” sound is the atrioventricular valves closing The “dub” sound is the aortic and pulmonary valves closing Video: Human Heartbeat 30 seconds http://www.youtube.com/watch?v=qYBtchCqPao

The heart is one organ that functions as two pumps One pump pushes blood to the lungs One pump pushes blood to the entire body The two pathways of blood are referred to as the: Pulmonary Circuit Systemic Circuit Follow along the diagram on page 312 Return to slide 3, show ventricle wall thickness difference for the circuits

In the Pulmonary Circuit: Oxygen-poor blood travels from the right side of your heart through the pulmonary arteries to your lungs In the lungs blood picks up O2 and releases CO2 Oxygen-rich blood travels from lungs through the pulmonary veins to the left side of the heart Note: Artery/Vein classification is only for direction! We inhale oxygen and exhale carbon dioxide

In the Systemic Circuit Oxygen-rich blood from the lungs enters the left atrium and it is then pumped into the left ventricle Blood is then pumped by the left ventricle through the aorta The aorta is the artery that supplies the oxygen-rich blood to all of the systems of the body Aorta -> Arteries -> Arterioles -> Capillaries

Capillaries -> Venules -> Veins -> Vena Cava(s) From the capillaries oxygen and nutrients diffuse out of the blood and carbon dioxide and other wastes diffuses in This deoxygenated blood will now will now return to the heart passing through the superior vena cava and inferior vena cava Capillaries -> Venules -> Veins -> Vena Cava(s) Oxygen-poor blood from the body enters the right atrium and it then pumped into the right ventricle, which pumps the blood to the lungs through the pulmonary arteries (pulmonary circuit begins again) The superior vena cava is supplied by the upper body and the inferior vena cava is supplied by the lower body Video: Heart Circulation 5min but skip from 45sec to 2min mark (animation pauses) http://www.youtube.com/watch?v=gn6QmETEm8s

The heart itself also needs a blood supply The heart receives very little oxygen and nutrients for its own cells from the blood it pumps through its chambers Instead a pair of arteries called coronary arteries branch from the aorta which cover the surface of the heart to supply the heart with oxygen and nutrients The coronary sinus is a collection of veins joined together to form a large vessel that collects deoxygenated blood from the heart and delivers it to the right atrium

Located in wall of right atrium The heart of a physically mature human beats over __________ times per day! Averaging 60-100 times per minute Heartbeat is effected by age, fitness, emotions A specific region of your heart muscle is known as the pacemaker because it sets the rate at which your heart contracts Located in wall of right atrium Generates electrical impulses that spread to a region of the heart called the atrioventricular (AV) node 100 000 times Heartbeat is effected by age, fitness, emotions Tissues working together to form organs, organs in systems, systems in organisms

The contracting ventricles send blood to the rest of the body First the atria contract and blood is forced into the ventricles which are relaxed Then the ventricles contract and pump blood into the arteries while the atria are relaxed The contracting ventricles send blood to the rest of the body Therefore the pacemaker ensure that the heart beats in a rhythmic cycle This cycle repeats about every second when at rest The pacemaker is controlled by both the nervous system and the endocrine system Sets of nerves with opposing antagonistic action, one to speed up heart rate and the other to increase heart rate, also hormones/chemicals to adjust hear rate Homework: read and make notes on Blood Pressure pg. 314-315, pg. 317 #2-15