transport in animals

• affinity


  The tendency of one substance to bind with another substance.
• aorta


  the artery that takes oxygenated blood away from the heart to the body
• arteriole


  a type of blood vessel that connects the arteries and capillaries. The walls of the arterioles contain large amounts of smooth muscle, some elastic fibres and some collagen.
• artery


  a type of blood vessel that carries blood away from the heart to the tissues, under high pressure. The walls of the arteries contain collagen, smooth muscle and elastic fibres
• atrial fibrillation


  An arrhythmia that involves the rapid contraction of the atria, preventing complete ventricular filling.
• atrial systole


  the stage of the cardiac cycle in which the atria contract, pushing blood into the ventricles. The AV valves are pushed open fully and the atria are emptied of blood.
• Atrioventricular node (AVN)


  A group of cells located between the atria that slow down the wave of excitation and pass it between the ventricles, along the bundle of His.
• Atrioventricular (AV) valves


  The valves found between the atria and ventricles. They prevent the backflow of blood from the ventricles into the atria. There are two types of atrioventricular valves: bicuspid and tricuspid
• bicuspid valves


  The atrioventricular valves found between the left atrium and left ventricle
• blood


  The transport medium in the mammalian circulatory system. It consists of plasma, red blood cells, white blood cells and platelets
• Bohr effect


  The loss of affinity of haemoglobin for oxygen as the partial pressure of carbon dioxide increases
• bradycardia


  A slow resting heart rate below 60 bpm.
• bundle of His


  A collection of Purkyne fibres which run from the AVN down to the apex of the ventricles
• capillaries 


  Microscopic blood vessels that form a large network through the tissues of the body and connect the arterioles to the venules. They are the site of exchange of substances between the blood and the tissues
• carbonic anhydrase


  An enzyme that catalyses the reversible reaction between water and carbon dioxide to produce carbonic acid.
• cardiac cycle


  Describes the sequence of events involved in one complete contraction and relaxation of the heart. There are three stages: atrial systole, ventricular systole and diastole.
• cardiac output


  The volume of blood pumped by the heart through the circulatory system in one minute. It is calculated using the equation: cardiac output = heart rate × stroke volume
• chloride shift


  The process by which chloride ions move into the erythrocytes in exchange for hydrogen carbonate ions which diffuse out of the erythrocytes. This maintains the electrochemical equilibrium of the cell.
• circulatory system


  The transport system in animals.
• closed circulatory system


  A circulatory system in which the blood pumped by the heart is contained within blood vessels. The blood does not come into direct contact with the cells. Closed circulatory systems are found in animals, e.g. vertebrates.
• diastole


  The stage of the cardiac cycle in which the heart muscle relaxes. The atria and ventricles fill with blood
• double circulatory system


  A circulatory system in which the blood flows through the heart twice in two circuits. Blood is pumped from the heart to the lungs before returning to the heart. It is then pumped around the body, after which it returns to the heart again. Double circulatory systems are found in mammals.
• ectopic heartbeat


  Additional heartbeats outside of the normal heart rhythm
• electrocardiogram (ECG)


  A technique used to indirectly measure the spread of electrical activity through the heart by measuring tiny changes in the skin's electrical conductivity. This produces a trace which is used to detect abnormalities in heart rhythm.
• Haemoglobin


  The red pigment found in erythrocytes that binds reversibly with four oxygen molecules to form oxyhaemoglobin. It is a globular protein that consists of four polypeptide chains, each with a prosthetic haem group
• Haemoglobinic acid


  The product formed when haemoglobin accepts free hydrogen ions. This enables haemoglobin to act as a buffer, reducing changes in blood pH.
• Heart rate


  The number of times the heart beats in one minute.
• Hydrostatic pressure


  The pressure exerted on the sides of a vessel by a fluid
• Inferior vena cava


  The vein that returns deoxygenated blood to the heart from the lower body
• Lymph


  Modified tissue fluid that drains into the lymphatic system. It carries less oxygen and fewer nutrients than tissue fluid, but also contains fatty acids
• Myogenic


  Describes cardiac muscle tissue that initiates its own contraction, without outside stimulation from nervous impulses
• Oncotic pressure


  The movement of water into the blood by osmosis due to the tendency of plasma proteins to lower the water potential of the blood
• Open circulatory system


  A circulatory system in which the transport medium pumped by the heart is not contained within vessels, but moves freely. The transport fluid comes into direct contact with the cells. Open circulatory systems are found in invertebrates, e.g. insects.
• Oxygen dissociation curve


  A graph that describes the relationship between the partial pressure of oxygen and the percentage saturation of haemoglobin in the blood.
• Plasma


  The main component of the blood that carries red blood cells. It is a yellow liquid that contains proteins, nutrients, mineral ions, hormones, dissolved gases and waste.
• Pulmonary arteries


  The arteries that carry deoxygenated blood away from the heart to the lungs.
• Pulmonary veins


  The veins that carry oxygenated blood from the lungs to the heart.
• Purkyne tissue


  Specialised cardiac muscle fibres which make up the bundle of His and conduct the wave of excitation through the septum, from the AVN down to the apex of the ventricles.
• Semilunar valves


  A pair of valves found between the ventricles and arteries. They prevent the backflow of blood from the arteries into the ventricles.
• Septum


  The wall of muscle which separates the left side of the heart from the right side of the heart, preventing oxygenated and deoxygenated blood from mixing.