Cardiovascular System The Heart

Heart Facts The cardiovascular system is composed of the heart and a _________system of vessels through which blood is circulated. Hollow muscular organ Tipped slightly so that a part of it sticks out and taps against the ______side of the chest (apex), which is what makes it seem as though it is located there. During an average lifetime, the human heart will beat more than 2.5 billion times. Beats over 100,000 times/day and 35 million times/year to pump blood around the body's 60,000 miles of blood vessels. ____pints of blood pump throughout your entire body with one single heartbeat.

External Structure of the Heart Layers Edocardium (inner layer) Epicardium (outer layer) Myocardium (middle layer) _________________ - the protective membrane surrounding the heart ____________arteries – supply blood to the outside of the heart

External Structure

Internal Structure Septum Atria and ventricles atria contract while the ventricles relax ventricles contract while the atria relax. ____________________ (AV) Valves Bicuspid (____________) Valve – between left atria and ventricle Tricuspid Valve – between right atria and ventricle __________________(SL) Valves Pulmonary SL Valve – between right ventricle and pulmonary artery Aortic SL Valve – between left ventricle and aorta Ventricular ____________ - right and left ventricles are divided by a thick muscular wall babies born with "hole in the heart“ Why problematic? Septum

connect papillary muscles to AV valves “heartstrings”

The Cardiac Cycle The events associated with one heartbeat. A single cardiac cycle lasts ______ seconds Described as the contraction and relaxation of the four heart chambers. During relaxation, chambers fill with blood (_________________). During contraction, chambers expel blood (_________________). Heart Sounds The first heart sound (______) occurs during ventricular contraction when the tricuspid and bicuspid valves (___valves) close. The second heart sound (________) occurs during ventricular relaxation when the pulmonary and aortic valves (___ valves) close.

The walls of the left ventricle are ________ as it has to pump blood to all the tissues, compared to the right ventricle which only pumps blood as far as the _____. Septum

Blood Pressure Blood moves through circulatory system from areas of high pressure to low pressure. (Contraction of the heart produces the pressure.) Blood Pressure is a measurement of the _______ that blood exerts against the inner walls of ______________. 120/80 is normal = systole/diastole systolic pressure - The maximum pressure during ventricular contraction; systolic pressure is the peak arterial pressure. diastolic pressure - The lowest pressure of blood in the arteries during ventricular relaxation (diastole); the arterial pressure drops.

Blood Pressure vs. Distance From Left Ventricle

Conduction System Heart muscle cells contract without stimulation from the nervous system in a continuous, rhythmic pattern. Contraction is initiated by the sinoatrial (SA) node (_______________________). SA node is located in the right atrium Cells of the SA node can reach threshold on their own SA node initiates one action potential after another (~70-80 times/min) Pathway of electrical impulse Sinoatrial (SA) node Atrioventricular (AV) node Atrioventricular bundle (bundle of His) Bundle branches Purkinje fibers There is a momentary delay as the ventricles fill before they contract

Electrocardiograms (ECG / EKG) A recording of the electrical changes that occur within the myocardium as the heart contracts. R vent cont L vent cont R atr cont

Electrocardiograms (ECG / EKG) Atria repolarized Ventricle depolarized Heart relaxed Ventricular walls repolarize AV node and walls depolarize Atrial walls completely depolarized Atria repolarizes Ventricle depolarizes