F211 - Transport in animals Flashcards
Why do multicellular organisms need a transport system?
Multicellular organisms are relatively big, they have a low surface area to volume ratio. A lot of multicellular organisms are very active so their cells need a constant, rapid supply of glucose and oxygen.
What’s a single circulatory system and give a named example.
A single circulatory system is where the blood only passes through the heart once for each complete circuit of the body. Fish have a single circulatory system. The heart pumps blood to the gills (to pick up oxygen) and then on to the rest of the body in a single circuit.
What’s a double circulatory system and give a named example.
A double circulatory system is where the blood passes through the heart twice for each complete circuit of the body. Mammals have a double circulatory system. The right side of the heart pumps blood to the lungs (to pick up oxygen). From the lungs, it travels to the left side of the heart, which pumps it around the rest of the body.
What’s a closed circulatory system and give a named example.
In a closed circulatory system, the blood is enclosed inside blood vessels.
E.G FISH: the heart pumps blood into arteries which branch out into millions of capillaries. Substances like oxygen and glucose diffuse in the capillaries into the body cells but the blood stays inside the blood vessels as it circulates.
What’s an open circulatory system and give a named example.
In an open circulatory system, blood isn’t enclosed in blood vessels all the time. It flows freely through the body cavity.
E.G: INSECTS: The heart is segmented. It contracts a wave, starting from the back, pumping blood into a single main artery which opens up into the body cavity. The blood flows around the insect’s organs, gradually making its way back into the heart segments through a series of valves.
Why does the left ventricle of the heart have thicker, more muscular walls than the right ventricle?
Because it needs to contract powerfully in order to pump the blood all around the body whereas the right ventricle only needs to pump blood to the lungs which are a considerable amount closer.
Why do the ventricles have thicker, more muscular walls than the atria?
Because they have to pump blood out of the heart whereas the atria only need to push blood a short distance into the ventricles.
What is the cardiac cycle?
An ongoing sequence of contraction (systole) and relaxation (diastole) of the atria and ventricles that keeps blood continuously circulating round the body.
Describe the cardiac cycle.
- VENTRICLE DIASTOLE, ATRIA SYSTOLE:
The atria fills with blood which decreases their volume and increases the pressure. This high pressure will cause the atrioventricular valve to open so all the blood goes into the ventricles. The atria will contract (systole) in order to force the remaining blood out. - VENTRICLE SYSTOLE, ATRIA DIASTOLE:
The ventricles fill with blood, meaning the volume decreases and the pressure increases. Since there’s a higher pressure in the ventricles rather than the atria, the atrioventricular valve will close to prevent backflow. The high pressure causes the semi-lunar valves to open and blood is forced out into the pulmonary artery and aorta. - VENTRICLE DIASTOLE, ATRIA DIASTOLE:
There’s a higher pressure in the pulmonary artery and the aorta which causes the semi-lunar valve to close, preventing backflow. The atria will then fill with blood again due to the higher pressure in the vena cava and the pulmonary vein and the cycle will start again.
Describe how heart action is coordinated.
The process starts in the sino-atrial node, which is in the wall of the right atrium. The sino-atrium node is like a pacemaker as it sets the rhythm of the heartbeat by sending regular waves of electrical activity over the atrial walls. This is what causes the right and left atria to contract at the same time. The waves of electrical activity is then sent to the atrioventricular node which is responsible for passing the waves of electrical activity on to the BUNDLE OF HIS. But there would be a slight delay before the atrioventricular node reacts, to make sure that the ventricles have contracted. The BUNDLE OF HIS is a group of muscle fibres responsible for conducting the waves of electrical activity to the PURKYNE TISSUE which carries the waves of electrical activity into the muscular walls of the right and left ventricles, causing them to contract simultaneously.
How do you work out heart rate (bpm)?
60 / time taken for one heartbeat (seconds)
Describe the structure and function of arteries.
Arteries carry blood from the heart to the rest of the body. Their walls are thick and muscular and have elastic tissue to cope with the high pressure produced by a heartbeat. The endothelium is folded, allowing the artery to expand. All arteries carry oxygenated blood, except the pulmonary arteries - which take deoxygenated blood to the lungs.
Describe the structure and function of veins.
Veins take blood back to the heart under low pressure. They’re quite wide but have very little elastic or muscle tissue. Veins contain valves to stop blood flowing backwards. All veins carry deoxygenated blood (since the oxygen has been used up by body cells), except for the pulmonary veins - which carry oxygenated blood from the lungs to the heart.
Describe the structure and function of the capillaries?
Arteries branch into capillaries, which are the smallest of the blood vessels. Substances like oxygen and glucose are exchanged between cells and capillaries so they’re adapted for efficient diffusion (due to their walls being one cell thick).
