The heart and circulation

The table compares features of different types of blood vessel in mammals.

Use the letters E to H to complete the following table.

Each letter may be used once, more than once, or not at all.

Unlike most other veins, pulmonary veins do not have valves.

Suggest why valves are not needed in pulmonary veins.

This is a drawing of a dissected human heart.

Identify the structures labelled J to M.

* This is an electrocardiogram (ECG) trace of a single heartbeat.

Describe how contraction of the heart muscle at rest is initiated and relate this process to the electrical activity recorded by the ECG.

Extra answer space if required.

Fig. 20.1 shows a normal ECG trace.

Fig. 20.1

Fig. 20.2 shows an ECG trace from a patient with abnormal heart activity.

Fig. 20.2

Identify this abnormality.

Give a reason for your identification.

Fig. 20.3 shows an ECG trace from another patient with abnormal heart activity.

Fig. 20.3

Identify this abnormality.

Give a reason for your identification.

21

Describe three ways fish gills are adapted for efficient gas exchange.

Explain why insects can function with open circulatory systems.

The largest fish is the whale shark. Whale sharks have an average mass of 20 tonnes.

The largest marine mammal is the blue whale. Blue whales have an average mass of 150 tonnes.

Use your knowledge of gas exchange and circulatory systems to suggest why marine mammals can grow to a much larger size than fish.

Explain how the structure of haemoglobin allows it to transport oxygen from the lungs to the tissues.

Which of the statements about the heart is correct?

A Contraction of the ventricles is known as ventricular systole.

B Deoxygenated blood enters the heart by the pulmonary vein.

C The pressure in the ventricles is always greater than in the atria because of the thicker ventricle wall.

D The wall of the left ventricle is less thick because it only has to pump blood to the lungs.

Your answer

During pregnancy the mother’s body undergoes several physiological changes to support the developing fetus. These changes affect every organ system in the body.

Changes to the heart and circulatory system begin in the first few weeks of pregnancy.

Fig. 16.1 shows the changes in stroke volume and heart rate that occur during pregnancy.

Fig. 16.1

Use the data in Fig. 16.1 to calculate the cardiac output in week 20.

Suggest an advantage of the increase in cardiac output.

Fig. 16.2 shows how blood pressure varies throughout pregnancy.

Fig. 16.2

A student looked at the data in Fig. 16.1 and Fig. 16.2 and drew the following conclusion:

‘As cardiac output increased blood pressure dropped so there must have been a decrease in vascular resistance.’

Evaluate this conclusion.

* Describe the flow of blood through the left side of the heart during the cardiac cycle and explain the role of valves and pressure differences in this process.

Additional answer space if required.

Another change that occurs in pregnancy is an increase in oxygen uptake by the mother. This is partly due to an increase in the mother’s metabolic rate and partly to supply the developing fetus.

Fig. 16.3 shows the oxygen dissociation curve for the mother’s haemoglobin.

Fig. 16.3

Sketch the oxygen dissociation curve for fetal haemoglobin.

Answer on Fig. 16.3.

Explain how the different affinities of maternal and fetal haemoglobin enable transfer of oxygen from the maternal circulation to the fetus.

Changes to kidney function during pregnancy can be confused with some diseases, such as chronic kidney disease or kidney failure.

The estimated glomerular filtration rate (eGFR) in a healthy 30–39-year-old is 107 cm³ min The eGFR usually decreases with age but in pregnancy, can increase by between 50 and 85%.

The table shows the results of some of the physiological measurements that a clinic carried out on two 35-year-old women. One of the patients was pregnant.

A doctor concluded that patient A was undergoing a normal pregnancy whereas patient B was suffering from kidney failure.

Explain the doctor’s conclusion.

The heart can be affected by a variety of disorders, some of which involve the immune system.

Fig. 1.1 shows the roles of three different types of antibody, labelled R, S and T.

R S

Harmful molecules released by pathogens Fig. 1.1

State the names of the three different types of antibody shown in Fig. 1.1.

A condition called rheumatic heart disease can occur when a person’s antibodies attack antigens on their own heart cells.

State the name of the type of disease represented by rheumatic heart disease.

Fig. 1.2 shows two electrocardiogram (ECG) traces:

• an ECG of normal heart activity

• an ECG of a person with a type of heart disease

Fig. 1.2

Describe how the ECG trace of the heart with heart disease is different from the ECG trace of a normal heart.

Gene therapy is a possible future treatment for heart disease.

The AC6 gene codes for one form of the enzyme adenylyl cyclase.

Clinical trials have tested the effect of increasing levels of the AC6 gene in heart cells.

Suggest how using gene therapy to increase levels of the AC6 gene in heart cells may improve heart function.

State one method for inserting the AC6 gene into the heart cells during gene therapy.

The results from gene therapy trials are published in peer-reviewed journals.

State why the results from gene therapy trials are published in journals.

The sea sponge, Aplysina aerophoba, and the zebra shark, Stegostoma fasciatum, are both animals.

A. aerophoba does not have an internal circulatory system. Instead, it filters food and oxygen from the surrounding water, as shown in Fig. 4.1.

Suggest why A. aerophoba does not need a circulatory system.

A diagram of the circulatory system of S. fasciatum is shown in Fig. 4.2.

Describe the type of circulatory system that S. fasciatum has.

Both A. aerophoba and S. fasciatum reproduce sexually, but under particular conditions they are both able to reproduce asexually.

In asexual reproduction in A. aerophoba:

• clumps of diploid cells detach from the body of the sponge

• the cells reattach to a surface and grow into new, adult sponges.

In asexual reproduction in S. fasciatum:

• meiosis occurs in a female

• two of the haploid cells produced by meiosis fuse to form a diploid cell

• the diploid cell develops into a new shark.

A student stated, ‘When they reproduce asexually, both animals produce clones of themselves.’.

Evaluate the student’s statement.

* Humans can produce artificial clones of animals.

Describe two methods for producing artificial clones of animals.

Additional answer space if required.

Fig. 16.1 shows a drawing of a dissected human heart.

Identify the structures labelled A to E on Fig. 16.1.

State which subdivision of the peripheral nervous system supplies structure A Fig. 16.1.

Fig. 16.2 is a diagram of a section through the human brain.

Identify the letter and name of the structure in Fig. 16.2 that is connected by nerves to structure A in Fig. 16.1.

Normal human resting heart rate is approximately 70 beats per minute (bpm). Cutting the parasympathetic nerve to the heart increases this to approximately 100 bpm.

Suggest two conclusions that could be made from this observation about the control of resting heart rate in normal humans.

Injury to the parts of the brain labelled G and H in Fig. 16.2 can lead to a range of symptoms including:

• fatigue

• weight gain

• menstrual irregularities

• low blood pressure or dizziness

• increased sensitivity to cold.

Outline how injury to G and H is able to cause such a wide range of symptoms.

Suggest why it can be difficult for a doctor to conclude that the symptoms described in part (iii) are definitely caused by damage to parts of the brain.

Complete the following passage using the most appropriate terms.

The knee-jerk reflex is an example of a spinal reflex as it only goes through the

........ whereas the blinking reflex is a cranial reflex as the pathway goes

through the brain.

Reflexes are very fast as they only involve one or two........, which

are the slowest parts of nerve transmission. This is one reason why reflexes give a survival

advantage.

Valves control the flow of blood through the heart.

Complete the table below to show the roles of two valves in the heart.

A ventricular septal defect (VSD) is a hole in the septum of the heart.

The diagram below shows a heart with VSD.

Describe and explain why people with VSD can easily become tired.

Creatine kinase (CK) is an enzyme that catalyses reactions in heart muscle. High levels of CK in the blood indicate that a person may have had a heart attack.

Suggest why high levels of CK in the blood indicate that a person may have had a heart attack.

Mice are often used in laboratory studies to research treatments for heart conditions.

These mice are often clones.

Suggest one reason why clones are used in these studies.

Fig. 16 shows pressure changes during the cardiac cycle.

Using Fig. 16, compare the changes in pressure in the left ventricle with the changes in pressure in the left atrium.

Using Fig. 16, calculate the heart rate of this individual.

Give your answer to 2 significant figures.

Using Fig. 16, calculate the percentage change between minimum and maximum pressure in the aorta.

Give your answer to 2 significant figures.

Name the valve which closes at point X on Fig. 16.

The heart supplies oxygenated blood to the tissues.

VO₂^max is a measurement of the maximum volume of oxygen that an individual can use during intense exercise in a given time.

Smart watches can estimate the VO₂^max of an individual by measuring heart rate while exercising.

Having a higher VO₂^max is associated with improved aerobic fitness.

Two male students exercised for 30 min and used smart watches to record their VO₂^max. Table 16 shows their masses and the VO₂^max values they recorded.

Student 1 drew the following conclusion from this result:

Student 2 said that this conclusion is invalid because several variables have not been controlled.

State three variables necessary for a valid comparison that have not been controlled in the above experiment.

Brown fat is a type of tissue.

Brown fat has a higher need for oxygen because fat cells in this tissue carry out aerobic respiration at a higher rate than fat cells in other tissues.

Suggest which organelle is present in higher numbers in brown fat cells than in other fat cells.

Mammals and fish both need circulatory systems to transport oxygen to respiring tissues. They have different circulatory systems because they have different oxygen requirements.

Acetylcholine (ACh) is a neurotransmitter in mammals. Studies have suggested that it also functions as a hormone in some invertebrate species, such as squid.

When ACh comes into contact with specialised cells in squid skin, it causes them to change colour. These colour changes allow the squid to communicate and to camouflage itself.

ACh is made by cells in the centre of the squid’s body.

Explain how it is possible for ACh to have an effect on cells in the skin of the squid.

Squid blood contains a blue oxygen-carrying protein called haemocyanin.

High partial pressures of carbon dioxide reduce the affinity for oxygen of haemocyanin.

Suggest a mechanism by which carbon dioxide could reduce the affinity for oxygen of haemocyanin.

Fig. 21.1 shows a transverse section of a human adrenal gland.

Using Fig. 21.1, identify the letter and name of the region of the adrenal gland that secretes adrenaline.

Identify patients X, Y and Z by labelling the traces in Fig. 21.2.

Sketch a trace for a patient who has entered atrial fibrillation.

Suggest why reduced heart rate is sometimes seen in people who are very aerobically fit.

Which of the statements, A to D, explains why diastole follows systole in the mammalian heart?

A Cardiac muscle is myogenic.

B Cardiac muscle takes a short time to repolarise after being stimulated.

C The aorta is capable of maintaining the pressure generated by the left ventricle.

D The SAN receives impulses from the AVN.

Your answer