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Max's Cardiology 102
A guide to the Cardiovascular System
| term | definition |
|---|---|
| aorta | The largest artery in the human body, carrying oxygenated blood from the left ventricle of the heart to the rest of the body. As it leaves the heart, it curves to the side, forming the aortic arch. |
| atrial systole | The period when the atria contract, forcing blood into the ventricles. |
| atrioventricular bundle | A collection of modified cardiac muscle cells called Purkinje fibres that are connected to the atrioventricular node and transmit electrical signals to the ventricles. Also known as the bundle of His. |
| atrioventricular node (AVN) | Group of specialised heart muscle fibres at the junction between the atria and ventricles that control the contraction of the ventricles. |
| atrioventricular valve | Valves that regulate the flow of blood from the atria to the ventricles. The valve found on the right side of the heart is known as the tricuspid valve and that on the left side as the mitral or bicuspid valve. |
| atrium (pl. atria) | One of the two upper chambers of the heart receiving blood from the veins. |
| autorhythmicity | The intrinsic ability that allows heart muscle to contract in a controlled rhythmic manner that is not dependent on the nervous supply to the heart. |
| baroreceptor reflex | A reflex mechanism, governed by the baroreceptors, that helps to maintain blood pressure within the normal range by restoring the body to its original condition. |
| baroreceptors | Receptors in the body that detect changes in blood pressure. |
| bicuspid valve | The atrioventricular valve found on the left side of the heart (also known as the mitral valve). |
| cardiac action potential | The electrical signal that initiates contraction of the cardiac muscle. |
| cardiac output | The volume of blood pumped out of the heart in one minute. Cardiac output = stroke volume × heart rate. |
| cardio-inhibitory centre | A nerve centre situated in the medulla (hindbrain region) which gives rise to the vagus nerve that innervates the heart (and other structures). |
| chemoreceptors | A sensory receptor that is responsive to chemical stimuli. |
| chordae tendineae | Strong cords that support the heart valves. They pass from the papillary muscles at the base of the ventricles to the ventricular surface of the valve flaps, and are also called heart strings. |
| complete cardiac diastole | The period during the cardiac cycle when the heart is in a state of complete rest. |
| contractility | An increase in the strength of contraction of cardiac muscle unrelated to the degree of ventricular stretching but under the control of the sympathetic nervous system. |
| coronary circulation | The vascular circulatory system that supplies the heart muscle with blood. |
| coronary sinus | Collection of veins joined together to form a large vessel that collects blood from the myocardium. Blood then drains directly into the right atrium. |
| depolarisation | A reduction in magnitude of a cells membrane potential, increasing electrical excitability and causing heart muscle contraction. |
| diastole | The period between two contractions of the heart when the heart muscle relaxes and allows the chambers to fill with blood. |
| diastolic blood pressure | The blood pressure recorded whilst the heart is relaxed and filling with blood. |
| electrocardiogram (ECG) | The graphic recording obtained using an electrocardiograph. The ECG represents the composite activity of the pacemaker nodes of both the heart and the cardiac muscle. |
| end diastolic volume | The volume of blood in the ventricles at the end of ventricular diastole. |
| end systolic volume | The volume of blood left in the ventricles after ventricular contraction. |
| erythrocytes | Red blood cells. These cells are biconcave in shape and contain haemoglobin. |
| erythropoietin | Hormone produced by the kidneys and also by the liver, which stimulates red blood cell production in the bone marrow. |
| haematocrit | The height of the column of erythrocytes relative to the total height of the column of blood (about 45% in healthy individuals). |
| haematopoiesis | The constant formation of blood cells from a common population of precursor stem cells in bone marrow. |
| haemoglobin | A globular iron-containing protein present in red blood cells, which binds oxygen at the lungs and transports it to the tissues. |
| inferior vena cava | The great vein which collects deoxygenated blood from the lower half of the body and transports it upwards to the right atrium of the heart, the other being the superior vena cava. |
| ion | An atom or molecule that has lost or gained one or more electrons, leaving it with a positive or negative charge, respectively. |
| isovolumetric contraction phase | The period during ventricular systole when both the atrioventricular valve and the semilunar valve are closed and the blood is trapped within the ventricles. |
| leukocyte | An immune system cell that circulates around the body helping to protect the body from infection and disease. Also known as a white cell. |
| leukocytes | A collective term for the various types of white blood cell. |
| mitral valve | The atrioventricular valve found on the left side of the heart (also known as the bicuspid valve). |
| myocardium | The muscular tissue of the heart. |
| negative feedback mechanism | When a system (such as the human body) responds in the opposite direction to a change in the parameter under regulation. It is the major physiological principle underlying homeostasis the means of returning the system to its original condition. |
| oxyhaemoglobin | Haemoglobin that is saturated with oxygen. |
| P wave | Defined as the first wave in an electrocardiogram, representing the wave of depolarisation that starts from the sinoatrial node and spreads throughout the atria. |
| pacemaker | A natural or artificial device for stimulating the heart muscle and regulating its contractions. |
| peripheral resistance | Resistance of the systemic circulation to blood flow. |
| plasma | The clear, yellowish liquid part of blood. Composed mainly of water, with dissolved proteins, ions, nutrients, hormones and waste products. |
| platelets | Small colourless disc-shaped cell fragments found in large numbers in the blood and involved in clotting. |
| pulmonary artery | The artery carrying deoxygenated blood from the right ventricle to the lungs. |
| pulmonary circulation | The closed interconnecting loop of blood vessels, carrying blood from the heart to the lungs and back again; Pulmonary artery moves deoxygenated blood from the heart to the lungs, pulmonary vein carries oxygenated blood from the lungs back to the heart. |
| Purkinje fibres | Modified cardiac muscle fibres that are part of the atrioventricular bundle, which is also known as the bundle of His. |
| QRS complex | Forms part of the ECG trace and represents the wave of ventricular depolarisation that precedes the contraction of the ventricles. |
| semilunar valves | Valves within the arteries leaving the heart that prevent blood flowing back from the arteries into the ventricles. These valves (the pulmonary and aortic valves) have cusps that are shaped in a pattern that resembles a half-moon. |
| septum | The muscular wall that separates the left and right sides of the heart. |
| sinoatrial node (SAN) | A group of cells (called a node) embedded in the wall of the right atrium, close to where the superior vena cava enters the heart, that initiate the wave of depolarisation that causes the heart to contract. |
| sinus rhythm | The normal regular cardiac rhythm produced by the activity of the sinoatrial node. |
| Starling's law | The force of contraction is related to the degree the heart is stretched before it contracts. More specifically, stroke volume is determined by the degree of distension of the atria and ventricles before contraction. |
| stroke volume | The volume of blood pumped out of the heart during one beat. |
| superior vena cava | The great vein which collects deoxygenated blood from the upper half of the body and transports it downwards to the right atrium of the heart, the other being the inferior vena cava. |
| systemic circulation | The closed loop of interconnected blood vessels, of varying diameters, carrying blood between the heart and body and returning the blood back to the heart. |
| systole | The contraction of the heart, when blood is pumped into the arteries. |
| systolic blood pressure | The maximum value of the blood pressure, which occurs during systole and the ejection of blood from the heart. The range of normal values is 100 140 mmHg. |
| T wave | Forms part of the ECG trace and corresponds to the period of ventricular repolarisation. |
| tricuspid valve | The atrioventricular valve found on the right side of the heart. |
| vagus nerve | The parasympathetic nerve that innervates the heart (activation of this nerve slows the heart). |
| vasomotor centre | Sympathetic nerve centre in the medullary region of the brain controlling cardiovascular function. |
| venous return | Blood flowing back through the veins into the right atrium of the heart. |
| ventricle | One of the two lower chambers of the heart pumping blood into the arteries. |
| ventricular ejection phase | The period when blood is ejected from the ventricles into the pulmonary artery and the aorta. |
| ventricular systole | The period when the ventricles are contracting. |
Created by:
maxchan666
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