Heart

Heart Structure The ________ separates the heart into 2 separate pumps The right side of the heart pumps blood into the __________ circuit The left side of the heart pumps blood into the _________ circuit The muscles in the (atria/ventricles) is thicker On average, our heart beats over 100,000 times per day, totalling up to nearly 2.5 billion times in a life time

Cardiac Cycle Cardiac cycle: a complete heartbeat, including the contraction and relaxation of heart muscle Takes 0.8 seconds to complete Cardiac cycle is divided into two phases Diastole: Ventricles are relaxed, being filled with blood Systole: Ventricles contract, blood is ejected What is the pericardium’s function?

Diastole begins when the atria begin to fill with blood, once the pressure and volume has built up in the atria, it causes the atrioventricular valves to open, sending blood into the ventricles The atria walls contract to send remaining blood into the ventricles Once the ventricles are filled to capacity, they contract, sending blood to the lungs and body by pushing through the semilunar valves The ventricles can then open up again (increasing in ’empty’ volume)

Heart Sounds The lubb-dubb sound of the heart is made by the valves closing Lubb = Atrioventricular valves Dubb = Semilunar valves Heard through the use of a stethoscope Heart murmur: valves fail to close properly, leads to ineffective blood delivery What was the sound associated with the heart beating? People with heart murmurs have an increased heart rate, why do you think this is?

Experiments have shown that when the heart is removed, it continues to beat for a short time What could this mean?

Cardiac Muscle Myogenic muscle: cardiac muscle, unusual ability to contract and relax on its own without an external source Ensures the heart will continue to beat even if the nervous system is damaged ‘Brain Dead’ Coma

Cardiac Muscle Sinoatrial (SA) node: mass of nerve and muscles cells in the right atrium, maintains a normal heartbeat Pacemaker Atrioventricular (AV) node: mass of conducting cells in the wall of the right atrium/ right ventricle, transmits signals from SA to ventricles Purkinje fibers: conducting fibers on the septum and ventricles, transmit signals from AV to muscles There are three components that allow for the heart to have precise and timely contractions and relaxations

Autonomic Nervous System Sympathetic Preparation for stress “Fight or Flight” Parasympathetic “Rest + Digest” What does the autonomic nervous system control? There are two divisions of the autonomic nervous system Sympathetic and Parasympathetic What would happen to heart rate when the body is signalling stress?

Electrocardiograph Electrocardiograph (ECG): device that detects the electrical activity of the heart through electrodes placed on the body’s surface Produces an electrocardiogram Because the heartbeat is electrically stimulated, it can be indirectly observed by reading those electrical signals An electrocardiogram is the reading it produces (the graph)

Electrocardiograph A single heartbeat includes the P wave, the ORS complex, and the T wave P = Contraction of the atria by the signals from the SA node The space in between (the plateau) is the delay when the SA node signals are reaching the AV node QRS = contraction of the ventricles (from the tip and moving upwards, think of squeezing a yogurt tube) Another slight delay as the ventricles recover and get ready for another contraction T = recovery period, To look for heart beat problems, you simply compare the normal graph to the one your patient produced, and look for the problem areas Animation: Figure 7 http://k12resources.nelson.com/science/9780176517595/student/ebook/data/animation/animation_ecg_video.html