What is Cardiac: Definition and 11 Discussions

The heart is a muscular organ in most animals, which pumps blood through the blood vessels of the circulatory system. The pumped blood carries oxygen and nutrients to the body, while carrying metabolic waste such as carbon dioxide to the lungs. In humans, the heart is approximately the size of a closed fist and is located between the lungs, in the middle compartment of the chest.In humans, other mammals, and birds, the heart is divided into four chambers: upper left and right atria and lower left and right ventricles. Commonly the right atrium and ventricle are referred together as the right heart and their left counterparts as the left heart. Fish, in contrast, have two chambers, an atrium and a ventricle, while reptiles have three chambers. In a healthy heart blood flows one way through the heart due to heart valves, which prevent backflow. The heart is enclosed in a protective sac, the pericardium, which also contains a small amount of fluid. The wall of the heart is made up of three layers: epicardium, myocardium, and endocardium.The heart pumps blood with a rhythm determined by a group of pacemaking cells in the sinoatrial node. These generate a current that causes contraction of the heart, traveling through the atrioventricular node and along the conduction system of the heart. The heart receives blood low in oxygen from the systemic circulation, which enters the right atrium from the superior and inferior venae cavae and passes to the right ventricle. From here it is pumped into the pulmonary circulation, through the lungs where it receives oxygen and gives off carbon dioxide. Oxygenated blood then returns to the left atrium, passes through the left ventricle and is pumped out through the aorta to the systemic circulation−where the oxygen is used and metabolized to carbon dioxide. The heart beats at a resting rate close to 72 beats per minute. Exercise temporarily increases the rate, but lowers resting heart rate in the long term, and is good for heart health.Cardiovascular diseases (CVD) are the most common cause of death globally as of 2008, accounting for 30% of deaths. Of these more than three-quarters are a result of coronary artery disease and stroke. Risk factors include: smoking, being overweight, little exercise, high cholesterol, high blood pressure, and poorly controlled diabetes, among others. Cardiovascular diseases frequently do not have symptoms or may cause chest pain or shortness of breath. Diagnosis of heart disease is often done by the taking of a medical history, listening to the heart-sounds with a stethoscope, ECG, and ultrasound. Specialists who focus on diseases of the heart are called cardiologists, although many specialties of medicine may be involved in treatment.

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  1. D

    Understanding the Cardiac Cycle: Diastole & Systole

    I am unsure about the underlined parts of the cardiac cycle. I was taught that the cardiac cycle started when the blood flowed into the atrium, but wouldn't there be a period when both artia and ventricles are at diastole simultaneously? For the second underlined part I was taught and read that...
  2. Sundog

    Medical How Does Venous Return = Cardiac Output?

    I'm not understanding this. To my knowledge, in normal function, the amount of blood coming into the heart is equal to the amount of blood going out. Venous return = cardiac output. But how can that be? How can the low pressure venous blood flow match the high pressure arterial blood flow...
  3. Asmaa Mohammad

    Rhythmicity of the heart and potassium ion

    Hello, I read that the rhythmicity of the heart increases due to decreasing in the permeability of SA node to K ions. I don't understand this mechanism, could anyone give me a simple explanation? Thanks!
  4. J

    Cardiac Action Potential Duration Question

    What does the APD (Action potential duration) determine in a cardiac cell and how can it be changed (do I need to effect any of the phases of the AP)? For example, if the vagal nerve releases acetylcholine here are its effects: Inhibits Atrial Muscle Contraction- Negative inotropic effect...
  5. S

    Work out cardiac cycle and heart rate

    I would just like to know if i have worked out one cardiac cycle and heart rate correctly. I have attached the image of the ecg called 'after exercise' here are my workings out: 1. CARDIAC CYCLE: there are 4 cycles so: 9 (grids) x 0.05 = 0.45 9x 0.05 = 0.45 9x 0.05 = 0.45 9x 0.05 = 0.45...
  6. J

    What is the difference between blood flow and cardiac output

    according to this one source, cardiac output (vascular) = blood flow (http://legacy.owensboro.kctcs.edu/gcaplan/anat2/notes/APIINotes5%20cardiac_equations.htm) However, their equations do not match: Cardiac output (CO)= Stroke volume * Heart Rate Blood Flow = cross sec area of vessel times...
  7. Q

    Wave Generator with Crystal Quartz Oscillator?

    Hi All! A little background info. I'm working with cardiac pacemaking devices with the overall scope of implementing piezoelectric energy harvesters into the devices. I'm in the initial stages of research and development. Okay, so this is my conundrum: I have an output pulse circuit as shown...
  8. N

    The Cardiac Cycle in Frogs: What is the Longest Part?

    I was struggling with the following question: In a frog heart preparation that is beating spontaneously, the longest part of the cardiac cycle involves: A. Contraction of the atria B. Contraction of the ventricle C. Relaxation of the ventricle D. Electrical conduction through the...
  9. C

    The Cardiac Cycle of the heart

    Hey guys, can someone make things clear for me? Does the heart goes atrial systole followed by ventricle systole then followed by both the atrial and ventricle diastole (at once) or atrial systole, ventricle systole (at the same time atrial diastole) then only ventricle systole?
  10. T

    Medical 8 letter word for a efficient grouping of cardiac muscle cells

    Doing a homework crossword and this is the last problem. I can't seem to find it anywhere. An efficient grouping of cardiac muscle cells, eight letters long ending in M. Any help would be much appreciated.
  11. G

    Cardiac Cycle, Tissue Fluid and Oxygen Dissociation Curve

    Hello people I am currently having problems doing my AS exam paper. Can you please help? The question is: During the cardiac cycle, the pressure in the left ventricle falls to a much lower level than in the aorta. Give an explanation for this difference? I have no idea about this...