heart

• The septum divides the heart into right and left sides.
• Pericardium:

  • A fluid-filled membrane that bathes the heart
  • Prevents friction between the outer wall and covering membrane
• Size of human heart: No larger than your fist (~300g)
• Human heart vs. Blue whale heart:

  • Average resting heart rate is between 60 and 80 beats per minute (bpm)
  • Lower for more fit individuals
  • Walking or mild exercise increases heart rate by ~20 to 30%
  • Those in good health have heart rates that can increase up to 200 bpm indicating the capacity of the heart to meet changing needs
• Pulmonary Circulatory System:

  • Includes the RIGHT SIDE of the heart and the blood vessels that carry blood to and from the lungs
  • Receives deoxygenated blood from body tissues and pumps it to the lungs to become oxygenated
• Systemic Circulatory System:

  • Includes the LEFT SIDE of the heart and the blood vessels that carry blood to and from the body’s other cells
  • Receives oxygenated blood from the lungs and pumps it to the other cells of the body
• One Way Flow of Blood:

  • Deoxygenated blood is carried to the heart by these veins:
  • Superior vena cava carries deoxygenated blood from the head, chest, and arms to the heart (right atrium)
  • Inferior vena cava carries deoxygenated blood from tissues of the lower body to the heart (right atrium)
  • Deoxygenated blood is carried away from the heart by arteries:
  • Pulmonary arteries (right and left) carry deoxygenated blood from the heart to the lungs
  • Oxygenated blood, flowing from the lung, returns to the heart (left atrium) by way of the pulmonary veins
• Left Atrium fills with blood eventually pumped into the larger left ventricle and out to the body’s tissues via the aorta
• Valves of the Heart:

  • Atrioventricular Valves (AV valves):
  • Separate the atria from the ventricles
  • Prevent blood from flowing back into the atria
  • Right AV valve = tricuspid valve (three flaps)
  • Left AV valve = bicuspid valve (two flaps)
  • Semilunar Valves:
  • Present on arteries
  • Prevent blood from flowing back into the ventricles
• How is heart tissue oxygenated?

  • Coronary arteries supply the cardiac muscle with oxygen and other nutrients
• The stimulus that triggers a heartbeat is an electrical signal that originates from within the heart itself. The nervous system will determine the rate and strength of the heartbeat
• Sinoatrial Node (SA Node):

  • A bundle of specialized nerves and muscle tissue
  • Acts as a pacemaker sets the rate of heartbeat
  • Located in the wall of the right atrium
• Atrioventricular Node (AV node):

  • Nerve impulses spread from SA node over the two atria, making them contract simultaneously
  • Contractions travel to the second node atrioventricular node (AV node) which serves as a conductor
  • AV node transmits the electrical signal through a bundle of specialized fibers called the bundle of His
  • The fibers relay the signal through two bundle branches (right and left bundles) that divide into fast-conducting Purkinje fibers, which initiate the almost simultaneous contraction of all cells of the right and left ventricles
• Monitoring Heart Function:

  • Electrocardiograph: An instrument for recording the changes of electrical potential occurring during the heartbeat. Electrodes are placed on the body’s surface and connected to a recording device
  • Electrocardiogram (ECG): The graph that displays the electrical impulses recorded from the electrocardiograph. Used to determine the health of the heart
• Heart Rate Influenced by Autonomic Nerves:

  • Sympathetic Nerve is stimulated during times of stress and increases heart rate
  • Increases blood flow to tissues
  • Enables the body to meet increased energy demands
  • Heart rate > 100 bpm is called tachycardia
  • Parasympathetic Nerve is stimulated during times of relaxation
  • Slows heart rate
  • Condition where the heart beats very slowly (40-60 bpm) is called bradycardia
• What is a cardiac arrhythmia?

  • A cardiac arrhythmia describes a heart that is beating irregularly. It may be beating too slow, too fast, or irregularly and fast
• Heart Sounds “Lubb/Dub”:

  • Diastole: refers to heart muscles relaxing. As a result, the heart fills with blood
  • Systole: refers to heart muscles contracting. The heart is pumping blood out
  • Lubb: When the ventricles contract, blood is forced up and causes the AV valves to close. The “lubb” is the sound produced when the AV valves close
  • Dubb: Sound produced when the semi-lunar valves close
  • Heart murmur: caused by faulty heart valves. Permits the backflow of blood into one of the heart chambers
• Cardiac Output & Stroke Volume:

  • Cardiac output is defined as the amount of blood that flows from each side of the heart per minute
  • Stroke Volume is the quantity of blood pumped with each beat of the heart
  • Heart Rate is the number of times the heart beats per minute
• Blood Pressure:

  • Sphygmomanometer (aka blood pressure cuff): a device used to measure blood pressure
  • Blood pressure is measured in the unit mmHg (= millimeters of mercury)
  • TWO values are reported for an individual’s blood pressure:
  • Systolic blood pressure: pressure blood exerts during ventricular contraction. Average of 120 mmHg
  • Diastolic blood pressure: pressure blood exerts during ventricular relaxation. Average of 80 mmHg
  • Blood pressure is read as a value of systolic blood pressure/diastolic blood pressure
• Regulation of Blood Pressure:

  • Blood pressure receptors (known as baroreceptors) located in the walls of the aorta and carotid arteries
  • Response to HIGH BLOOD PRESSURE:
  • Sympathetic nerve (“stress nerve”) is turned down and the parasympathetic nerve (“slow-down nerve”) is stimulated
  • Arterioles dilate
  • Decreased stroke volume and heart rate
  • Slows movement of blood into arteries thereby lowering blood pressure to acceptable levels
  • Response to LOW BLOOD PRESSURE:
  • Sympathetic nerve is stimulated
  • Arterioles constrict
  • Increased stroke volume and heart rate
• • Increased movement of blood into arteries, accompanied by decreased outflow, raises blood pressure to acceptable levels
• The atria are thin-walled chambers that receive blood from veins, while the ventricles have thicker walls to pump blood out to arteries.
• the right ventricle pumps deoxygenated blood to the lungs via pulmonary trunk
• the left ventricle pumps oxygenated blood to the body via arteries
• the right atrium receives blood from the vena cava
• The left atrium receives deoxygenated blood from the lungs and pumps it into the left ventricle.
• The heart is a muscular organ located in the chest cavity.
• The right atrium receives deoxygenated blood from the body through the superior vena cava and inferior vena cava, while the left atrium receives oxygenated blood from the lungs via pulmonary veins.
• valves prevent back flow of blood between chambers or out of the heart
• Semilunar valves prevent backflow of blood from the ventricles into the great vessels
• Pulmonary circulation carries deoxygenated blood from the right ventricle to the lungs where it picks up oxygen and releases carbon dioxide. It then returns to the left atrium through four pulmonary veins.
• the left atrium receives blood from the pulmonary vein