THE HEART Biology 20 – Unit D: Human Systems Pg

Introduction What kind of muscle is the heart made out of?

K-W-L 1. What do you already know about the circulatory system? 2. What do you want to know about the circulatory system?

Facts The heart is a muscular organ that pumps to circulate blood throughout the body What does the blood transport? The heart is the size of your fist (300 g) Beats on average 70 times/min (bpm)

“Exploring the Heart” Video

The Heart A fluid-filled membrane called the pericardium surrounds the heart Prevents friction between its outer wall and covering membrane Consists of two parallel pumps separated by a septum Pumps are synchronized

Pulmonary Circuit The system of blood vessels that carries deoxygenated blood to the lungs and oxygenated blood back to the heart Left lung Right lung

Systemic Circuit The system of blood vessels that carries oxygenated blood to the tissues of the body and deoxygenated blood back to the heart

Four-chambered Heart Left Atrium Right Atrium Left Ventricle Right Ventricle Atrium (plural: atria): A thin-walled chamber of the heart that receives blood from veins Ventricle: A muscular, thick- walled chamber of the heart that delivers blood to the arteries Septum

Heart Valves (one-directional blood flow) Left Atrioventricular (AV) valve Bicuspid Valve Right Atrioventricular (AV) valve Tricuspid Valve Semilunar Valve Atrioventricular (AV) valve: a heart valve that prevents the backflow of blood from a ventricle into an atrium Semilunar valve: a valve that prevents the backflow of blood from an artery into a ventricle (moon-shaped)

Veins and Arteries Left pulmonary artery Superior vena cava Right pulmonary artery Aorta: the largest artery in the body; carries oxygenated blood to the tissues Inferior vena cava Right pulmonary veins Left pulmonary veins

Coronary Arteries Arteries that supply the cardiac muscle with oxygen and nutrients Fat deposits and plaque can collect inside coronary arteries causing chest pain (too little O 2 reaches the heart)

Setting the Heart’s Tempo Cardiac muscle displays a branching pattern Unique ability to contract without being stimulated by external nerves = myogenic muscle !!! Heart can beat outside the body !!!

Setting the Heart’s Tempo Ventricle muscle tissue beats slower Atria muscle tissue follows a faster rhythm United, they assume a single beat – slower muscle assumes the tempo set by the faster muscle

Setting the Heart’s Tempo Beat rate set by the sinoatrial (SA) node (upper right atrium) Acts as a pacemaker Moves to a second node; the atrioventricular (AV) node Serves as a conductor AV node passes electrical nerve impulses to two large nerve fibres (Purkinje fibres) through the septum toward the ventricles

Setting the Heart’s Tempo These branching Purkinje fibres carry impulses from the AV node to the bottom tip of the heart A wave of cardiac contraction follows

Heart Rate (HR) Influenced by autonomic nerves Conduct impulses from the brain to the SA node Sympathetic nervous system: a division of the autonomic nervous system that prepares the body for stress (increases HR) Increases blood flow, meeting increased energy demands Can lead to tachycardia (>100 bpm from exercise or drugs) Parasympathetic nervous system: a division of the autonomic nervous system that returns the body to normal resting levels following adjustments to stress (decreases HR)

Summary The pulmonary circulatory system is the system of blood vessels that carries blood to and from the lungs. The systemic circulatory system is the system of blood vessels that carries blood to and from the body The heart consists of two parallel pumps separated by the septum Blood enters the heart through the atria Ventricles pump the blood to the body tissues Atrioventricular valves prevent the flow of blood from the ventricles back into the atria Semilunar valves prevent the flow of blood from arteries back into the ventricles Coronary arteries supply the heart with oxygen and nutrients The heart rate is set by the sinoatrial (SA) node. Contractions in the SA node travel to the atrioventricular (AV) node and then travel along the Purkinje fibres to the rest of the heart