Practise mammalian circulation, vessel and heart structure, cardiac-cycle control, haemoglobin transport and tissue-fluid exchange using images, pressure data and curves.
Hummingbirds are the smallest of birds and are found in the Americas. Some species migrate hundreds of kilometres between warmer overwintering areas and summer breeding grounds. Like mammals, birds maintain a constant body temperature.
Hummingbirds have a high requirement for sugars because they have a very high metabolic rate. Fig. 3.1 shows a hummingbird feeding on nectar, one of their main food sources.
Fig. 3.1
In birds such as hummingbirds:
- blood is kept within vessels
- for each complete circuit of the body, blood passes through the heart twice.
State the term used to describe this type of circulatory system.
Complete Table 3.1 to show the names and functions of the main blood vessels associated with the heart of mammals.
Table 3.1
Control of heartbeat is myogenic. This means the electrical activity controlling the rhythm of a regular heartbeat begins in the heart muscle itself.
Atrial fibrillation (AF) is an abnormal heart rhythm that causes rapid and irregular contractions of the atria. Untreated cases of AF can lead to a stroke.
A stroke is caused when a small blood clot, often forming in the left atrium, is carried by the blood to the brain where it blocks a small artery and leads to brain damage.
List all of the structures through which a blood clot in the left atrium must travel to reach the blood vessels supplying the brain.
The structures must be listed in the correct sequence.
A common cause of AF is when a small group of muscle cells in the wall of the left atrium starts to send out electrical impulses to the surrounding heart muscle cells.
Explain how the control of heartbeat by the sinoatrial node can be disrupted by AF , resulting in rapid and irregular atrial contractions.
Red blood cells are involved in the transport of oxygen and carbon dioxide in the blood.
Fig. 5.1 is a diagram representing the exchange of oxygen and carbon dioxide between a red blood cell in a capillary and a respiring cell. Some of the reactions that take place in the red blood cell are also shown. The diagram is not drawn to scale.
Fig. 5.1
Identify enzyme X and molecule Y in Fig. 5.1.
X
Y
The hydrogencarbonate ions shown in Fig. 5.1 leave the red blood cell and are replaced by chloride ions.
State why it is necessary for chloride ions to enter the red blood cell as hydrogencarbonate ions leave.
Identify the aqueous environment, labelled Z in Fig. 5.1, that surrounds the respiring cell.
The mammalian circulatory system is adapted for the long-distance transport of the respiratory gases, oxygen and carbon dioxide.
The system is described as a closed double circulation.
Name:
- the two different circulations of the double circulatory system of mammals
- the main vein returning deoxygenated blood to the heart.
In a closed circulation, blood is kept within vessels at all times.
Name the type of blood vessel that connects capillaries and veins.
Fig. 1.1 is a diagram of a section through the heart.
Fig. 1.1
On Fig. 1.1:
- add a label line and the letter L to show the artery that takes blood from the heart to the lungs
- add a label line and the letter R to show the valve that closes when the right ventricle is in systole.
The entry of carbon dioxide into red blood cells results in the production of hydrogencarbonate ions. This involves the enzyme carbonic anhydrase.
Complete the passage summarising the production of hydrogencarbonate ions by:
- writing the correct biological term in the spaces provided
- writing the molecular formula for two of the terms in the spaces in brackets.
Carbonic anhydrase has an overall spherical shape and is known as a protein. The enzyme acts within the cell so can be described as an enzyme. When blood passes into the capillary network through actively respiring tissues, carbon dioxide ( ) diffuses into red blood cells and carbonic anhydrase catalyses a reaction where ( ) is combined with to form , which rapidly forms ions ( and hydrogencarbonate ions ( ).