The Heart

FACTS ABOUT THE HEART When someone listens to your heart with a stethoscope the sound is often described as - lub-dub lub-dub. The 1st heart sound (lub) is caused by the acceleration and deceleration of blood and vibration of the heart at the time of the closure of the Tricuspid and Mitral Valves. The 2nd heart sound (dub) is caused by the same acceleration and deceleration of blood and vibrations at the time of closure of the Pulmonic and Aortic Valves.

MORE FACTS AgePulse- Newborn130 3 months140 6 months130 1 year120 2 years115 3 years100 4 years100 6 years100 8 years90 12 years85 adult60 - 100

MORE FACTS How many times does you heart beat? The average heartbeat is 72 times per minute. In the course of one day it beats over 100,000 times. In one year the heart beats almost 38 million times, and by the time you are 70 years old, on average, it beats 2.5 billion times!

MORE FACTS 100How much blood does your heart pump? An average heart pumps 2.4 ounces (70 milliliters) per heartbeat. An average heartbeat is 72 beats per minute. Therefore an average heart pumps 1.3 gallons (5 Liters) per minute. In other words it pumps 1,900 gallons (7,200 Liters) per day, almost 700,000 gallons (2,628,000 Liters) per year, or 48 million gallons (184,086,000 liters) by the time someone is 70 years old. That's not bad for a 10 ounce pump!

Location Mediastinum- between lungs and the sternum, rests just above the diaphragm

Pericardium 2 layer membrane that surrounds the heart 1. fibrous- outer membrane made of dense irregular connective tissue 2. serous- 2 layers a. parietal-outer membrane b. visceral or epicardium-inner membrane adheres directly to the surface of the heart Pericardial or serous fluid between a+b. Pericarditits- inflammation of serous fluid can lead to cardiac tamponade

Myocardium Cardiac muscle that makes up the majority of the heart Striated Involuntary Branched -- interlacing bundles

Cardiac muscle Forms 2 networks atrial and ventricular. Fibers are connected by intercalated disks.

Endocardium 2.endocardium 1. purkinje fibers 3. myocardium

Chambers 2 upper chambers the Atria Rt. atrium leads to the tricuspid and the rt. Ventricle. Lt. atrium leads to the bicuspid and the left ventricle.

Lower Chambers Rt. Ventricle –leads to the semilunar valve into the pulmonary arteries. Lt. Ventricle -leads to the semilunar valve into the aorta

Vessels of the Heart Vena Cava- drains O2 poor blood from the body into the Rt. Atrium. Coronary Sinus- drains O2 poor blood into the rt. atrium Pulmonary arteries- from the rt. Vent. to the lungs Pulmonary veins- from the lungs to the lt. atria Aorta- from the left vent. to systemic circulation

Vessels continued Coronary arteries- from the aorta, brings O2 rich blood to the heart Carotid arteries- to the head and brain Descending Aorta-systemic circulation Brachiocephalic- branches into the subclavian and carotid arteries Jugular vein- drains blood from the head

Valves Atrioventricular valves Tricuspid connects rt. atrium to rt. ventricle, has 3 cusps Bicuspid (mitral) connects lt. atrium to lt. ventricle, has 2 cusps Chordae tendinae- connect to papillary muscle on the ventricular wall

Valves continued Semilunar valves. Have 3 cusps Pulmonary valve rt. side Aortic valve left side Regurgitation- backflow of blood thru a faulty valve.

Cardiac problems Ischemia- reduced oxygen to a cell Angina Pectoris- chest pain Myocardial Infarction ( MI )- heart attack, death in cardiac tissue. Ventricular Fibrilation ( V-FIB )-asynchronous muscle contraction.

Conduction of the Heart Controlled by the Autonomic Nervous System, (ANS) ANS- regulates heart rate but does not initiate it. Sinatrial Node (SA)- located in the right Atrial wall,initiates heartbeat.”pacemaker” Atrioventricular Node (AV)- located in the interatrial septum, depolarized by the SAnode. The Av slows down the action potential so that the atria can empty into the ventricles.

Conduction continued AV bundle ( Bundle of Hiss)- stems from the AV node down thru branches into the interventricular septum of the heart. Purkinje fibers or conduction myofibers- distribute the action potential thru the ventricular myocardial cellsat about the same time.

Electrocardiogram EKG

Heartbeat Systole– during contraction Diastole– during relaxation Average or normal range around 120/80 Systole/Diastole

3 Phases of the heartbeat 1.Relaxation- (T-wave), repolarization of ventricular fibers, semilunar valves close 2. Ventricular filling, 75% occurs without atrial contraction, SA-node fires (P-wave), atrial contraction 25% vent filling 3. Ventricular Systole (contraction) (QRS-wave), firing of AV-node and ventricular depolarization

Timing Average heartbeat 75x per minute Takes about 0.8 sec Diastole 0.7sec Systole 0.1sec When the heart is beating faster the relaxation period is shortened.

Cardiac Output Cardiac Output(CO)-The amount of blood ejected from the ventricles into the Aorta and pulmonary trunk each minute. Stroke volume-the amount of blood ejected by a ventricle during each contraction. Cardiac Output =stroke volume x beats per minute

Factors affecting heartrate ANS-cardiovascular center in the Medulla Oblongata Sympathetic cardiac accelerator nerves release Norepinephrine increasing heartrate and stregth of contraction Parasympathetic fibers via the vagus nerves initiate the release of Acetylcholine decreases heartrate and weakens contractions

Heart rate -control Baroreceptors- neurons sensitive to changes in blood pressure. Located in the aortic arch, carotid arteries, rt.atrium If pressure increases the baroreceptors send impulses along the glossopharyngeal nerve which stimulate the cardioinhibitory center. This increases parasympathetic impulses which decrease rate and force of heart contraction This also decreases sympathetic impulses which causes vasodialation.

Heart rate control- continued If blood pressure is low the baroreceptors do not stimulate the cardiac inhibitory center. Heart rate and force of contraction increases Cardiac Output (CO) increases Vasococonstriction All lead to increased blood pressure

Chemicals Epinephrine from the adrenul medulla increase heart rate Elevated Potassium or Sodium decrease heart rate Lower levels of Oxygen in the blood increase heart rate

Other Factors Temperature Fever increases AV-node activity increasing heart rate. Emotions like fear, anger, anxiety increase heart rate. Depression and grief tend to decrease heart rate Gender and Age Females a little faster than males Starts fast at birth and slows down as we get old