Transport in animals - Module 3

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.

Single circulatory system

A circulatory system in which the blood travels one circuit; blood

flows through the heart and is pumped around the body before returning to the heart. Single

circulatory systems are found in fish.

Sinoatrial node (SAN)

A group of cells in the wall of the right atrium that generate electrical

activity, causing the atria to contract. The SAN is often referred to as the heart’s pacemaker.

Stroke volume

The volume of blood pumped by the left ventricle of the heart in a single

contraction.

Superior vena cava

The vein that returns deoxygenated blood to the heart from the head

and upper body.

Tachycardia

A rapid resting heart rate over 100 bpm.

Tissue fluid

The fluid that surrounds the cells of animals. It has the same composition of

plasma but does not contain red blood cells or plasma proteins.

Tricuspid valves

The atrioventricular valves found between the right atrium and right

ventricle.

Vein

A type of blood vessel that carries blood towards the heart under low pressure. They

have a wide lumen, a smooth inner lining and valves. The walls of the veins contain large

amounts of collagen, smooth muscle and little elastic fibre.

Ventricular systole

The stage of the cardiac cycle in which the ventricles contract, pushing

blood into the arteries. The semi-lunar valves are pushed open fully.

Venule

A type of blood vessel that connects the capillaries and veins. The walls of the

venules contain small amounts of collagen and smooth muscle.