How big is the heart?
About the size of a fist. Weights 9-12 oz.
How many times does the heart beat per day?
100,000 beats per day
How much blood does the heart pump?
About 7,000 liters per day
Where is the heart located?
Above the diaphragm between the lungs in the mediastinum.
How much pericardial fluid is in the heart?
What is the pericardium?
The outer cover of the heart. Has a parietal cover which is outside and a visceral cover which is on the inside and consists of 2 layers. Pericardial fluid is in between the two layers.
What are the 3 layers of the heart wall?
The outer is epicardium. The middle layer is myocardium ((striated, involuntary, branched)). The inner layer is endocaridum (connective tissue, covers valves).
Describe the myocardium.
One nucleus per cell, short, many mitochondria, best blood supply, locked together at intercalated discs, twitches all the time with long refractory periods, lipids have more energy potential, aerobic even when active.
What is systole and diastole?
Systole is contraction of the chambers, diastole is relaxing of the chambers. Happens at the same time in atria and ventricles.
What does the SA node do?
Also called the pacemaker, it initiates the stimulus for the heart to contract.
What is the P portion of a PQRST wave?
Represents the depolarization in the sinus node and subsequent atrial contraction. Small due to small mass of the atrium
What is the QRS complex?
Represents the conductance and sequential depolarization of the ventricles. Large due to large mass of the ventricles.
What is the T portion of a PQRST wave?
Represents the repolarization of the ventricles.
Define cardiac arrhythmia
It is an irregular heartbeat. More common as one gets older.
What is atrial fibrillation?
An irregular and often rapid heart rate that commonly causes poor blood flow to the body. Happens when the two atrial chambers have an irregular beat.
What is premature atrial contraction?
An atrial contraction that happens earlier than the next regular beat should have happened.
What is premature ventricular contraction?
Extra, abnormal heartbeats that begin in one of your heart’s two lower pumping chambers (ventricles).
What is ventricular fibrillation?
When the heart’s electrical activity becomes disordered and the ventricles contract in a rapid unsynchronized way. Heart pumps little or no blood.
What happens if the SA node malfunctions?
The AV node sets the pace of the heart which is about 40-60 bpm. Less blood gets circulated to the body.
What is the pace when the hearts conductive system is normal?
About 70 bpm
What is bradycardia?
A slower than normal heart rate.
What is tachycardia?
A faster than normal heart rate.
What are the two phases of the cardiac cycle?
Systole and diastole.
What are the average times for the cardiac cycle?
Atrial systole happens at 100ms. Ventricle systole happens between 100-360ms. Early ventricular diastole happens around 360-800ms.
What terms describes the ability to listen to heart sounds?
What sounds are we listening for when using a stethoscope?
Listening for turbulence when blood sloshes around when valves close (lubbdupp sound)
What is the first sound heard (lubb)?
The closing of the AV valve.
What is the second sound heard?
the “dupp” is the closing of the semilunar valve (aortic and pulmonary)
What are heart murmurs?
Any abnormal sound before or after the valves close.
What is the formula for cardiac output?
Stroke Volume (mL/beat) x BPM (beats/minute) = Cardiac Output (mL/minute)
What is stroke volume?
The amount of blood per beat ejected into the aorta and pulmonary artery.
What is end-systolic volume (ESV)?
The volume of blood in a ventricle at the end of contraction (systole). Lowest volume of blood in the ventricle at any point in the cardiac cycle.
What is end-diastolic volume (EDV)?
The volume of blood in the right and/or left ventricle at the end of diastole.
What is Starling’s Law?
The strength of the heart’s systolic contraction is directly proportional to its diastolic expansion with the result that under normal physiological conditions the heart pumps out of the right atrium all the blood returned to it without letting any back up in the veins
What is cardiac reserve?
The work that the heart is able to perform beyond that required under the ordinary circumstances of daily life.
What are some factors that influence heart rate?
Temperature, body position, age, emotions, sex of individual, hormones (epinephrine), potassium decrease, calcium increase.
What are baroreceptors?
Pressure sensors in arteries that regulates the blood pressure throughout the body. Located on the aorta, carotid and atrial arteries.
What is Marey’s Law?
The pulse rate varies inversely with the blood pressure (pulse is slow when the pressure is high).
What is the brainbridge reflex?
Acceleration of the heart rate results in increased blood pressure. Prevents pooling of the blood in veinous system.
How many blood vessels do we have?
Enough to go around the globe twice. About 65,000 miles of blood vessels
How does blood move through the vessels?
Arteries take blood away from the heart and veins bring the blood back to the heart. In between arteries and veins are capillaries. Arterioles take blood from the arteries to the capillaries and venules take blood from the capillaries to the veins.
What are the 3 layers of blood vessels?
Tunica intima (interna), tunica media, tunica externa (adventitia). They are the same for arteries and veins.
Describe the tunica intima
Made up of a thin layer of endothelial cells and lines the entire circulatory system. Capillaries only have a tunica intima
Describe the tunica media
The muscular, middle layer of arteries and veins. Bigger in arteries than veins. Made of elastic and collagenous fibers.
Describe the tunica externa
The outside layer composed of elastic and collagenous fibers. Protect the vessel from over expansion. Vasa Vasorum are found on this level that supplies blood to the vessels.
Describe elastic arteries.
Receives blood directly form the heart. They are thin in order to stretch and accommodate the blood surge.
Describe muscular (distributing) arteries
Further away from the heart. Goes to specific organs. Smaller than elastic.
What are arterioles?
Small vessels that moves blood from arteries to capillaries. May have only smooth muscle cells in tunica externa. Can dilate to affect blood pressure.
What are venules?
Carries blood from capillaries to veins. Has three layers: Inner endothelium, middle later of muscle and elastic tissue, outer layer of fibrous connective tissue. Comes from individual organs.