B5

Question 1

What is the function of the heart and how does it work?

Answer 1

The heart circulates blood through two pathways: the pulmonary circuit and the systemic circuit.

In the pulmonary circuit, deoxygenated blood leaves the right ventricle of the heart via the pulmonary artery and travels to the lungs, then returns as oxygenated blood to the left atrium of the heart via the pulmonary vein.

In the systemic circuit, oxygenated blood leaves the body via the left ventricle to the aorta, and from there enters the arteries and capillaries where it supplies the body’s tissues with oxygen. Deoxygenated blood returns via veins to the venae cavae, re-entering the heart’s right atrium.

Question 2

What is the function of the arteries?

Answer 2

they carry oxygen-rich blood from your heart to all parts of your body, getting smaller as they get further away from the heart

Question 3

What is the function of the capillaries?

Answer 3

they connect the smallest arteries to the smallest veins, and help exchange water, oxygen, carbon dioxide and other nutrients and waste substances between the blood and the tissues around them

Question 4

What is the function of the veins?

Answer 4

they carry blood, lacking in oxygen, back towards your heart, and get bigger as they get nearer your heart

Question 5

What happens when the coronary arteries get blocked?

Answer 5

If your coronary arteries are narrowed or blocked, the blood supply to your heart will be impaired. This is the most common form of heart disease, known as coronary heart disease (sometimes called coronary artery disease or ischaemic heart disease).

Eventually, your arteries may become so narrow they can’t deliver enough blood to your heart. This can cause angina - a pain or discomfort in your chest, arm, neck, stomach or jaw.

If the fatty material breaks off or ruptures, a blood clot will form, which can cause heart attack (or stroke, if the artery affected is carrying blood to your brain).

Question 6

What is the function of the endocrine system?

Answer 6

The endocrine system is the collection of glands that produce hormones that regulate metabolism, growth and development, tissue function, sexual function, reproduction, sleep, and mood, among other things.

Question 7

How is blood sugar level controlled?

Answer 7

The blood sugar level is controlled by the release and storage of glucose, which is in turn controlled by a hormone called insulin.

Question 8

How is body temperature controlled?

Answer 8

This is controlled to maintain the temperature at which enzymes work best, which is 37°C. Body temperature is controlled by:

• controlling blood flow to the skin
• sweating
• shivering

Question 9

How is the body’s water content controlled?

Answer 9

This is controlled to protect cells by stopping too much water from entering or leaving them. Water content is controlled by water loss from:

• the lungs when we exhale
• the skin by sweating
• the body, in urine produced by the kidneys

Question 10

What happens when blood glucose levels become too high?

Answer 10

Insulin is secreted into the blood and the liver converts glucose into glycogen. The blood glucose level goes down.

Question 11

What happens when blood glucose levels become too low?

Answer 11

Insulin is not secreted into the blood. The liver does not convert glucose into glycogen and the blood glucose level goes up.

Question 12

How are the kidneys controlled to determine the concentration of urine?

Answer 12

The more concentrated the plasma, the more ADH is released into the blood. When the ADH reaches the kidneys, it causes them to reabsorb more water. This keeps more water in the body and produces more concentrated urine.

When the plasma is more dilute, less ADH is released into the bloodstream. This allows more water to leave the kidneys, producing a more dilute urine.

Question 13

Which hormones regulate the menstrual cycle and how?

Answer 13

Before ovulation:
- FSH causes the ovaries to develop a follicle containing an egg, and to produce oestrogen.
- When the level of oestrogen reaches a certain point, it inhibits the release of FSH. This ensures that only one egg develops in each cycle.
- Oestrogen also stimulates the release of LH from the pituitary gland. LH stimulates an egg to be released from the follicle (ovulation).
After ovulation:
- Progesterone is secreted from the empty follicle. It inhibits the release of LH and FSH.
- Oestrogen also inhibits the release of LH and FSH.
- If a woman becomes pregnant progesterone will continue to be produced by the placenta, preventing the maturation of another follicle.

Question 14

Describe some hormonal and non-hormonal methods of contraception.

Answer 14

Hormonal:

• The oral contraceptive, which is known as the pill, contains oestrogen or progesterone. These hormones inhibit the production of FSH, so eggs cannot mature and ovulation does not take place.
• Contraceptive injections, implants or skin patches contain slow-release progesterone to inhibit the maturation and release of eggs.

Non-hormonal:

• Physical barrier methods such as condoms and diaphragms, which prevent the sperm reaching an egg.
• Intrauterine devices (IUD), also known as a coil, prevent the implantation of an embryo or release of a hormone.
• Spermicidal agents which kill or disable sperm.
• Abstaining from intercourse when an egg may be in the oviduct.
• Surgical methods of male and female sterilisation. An example is a vasectomy, where the sperm ducts are cut and tied.

Question 15

How can type 1 diabetes be treated?

Answer 15

Type 1 diabetes arises when the pancreas

stops making insulin; blood sugar can be regulated using insulin injections.

Question 16

How can type 2 diabetes be treated?

Answer 16

Type 2 diabetes develops when the body no longer responds to its own insulin or does not make enough insulin; blood sugar can be regulated using diet (high in complex carbohydrates), exercise and insulin injections.

Question 17

Describe the cornea and its function.

Answer 17

The cornea is the front part of the tough outer coat, the sclera. It is convex and transparent. Its function is to refract light - bend it as it enters the eye.

Question 18

Describe the iris and its function.

Answer 18

The iris is pigmented and decides the colour of your eyes so light cannot pass through. Its muscles contract and relax to alter the size of its central hole or pupil. Its function is to control how much light enters the pupil.

Question 19

Describe the ciliary muscles and their function.

Answer 19

A ring of muscle that surrounds the lens. Changes the shape of the lens to focus light on the retina (a process which is called ‘accommodation’).

Question 20

Describe the lens and its function.

Answer 20

The lens is a transparent, bi-convex, flexible disc behind the iris attached by the suspensory ligaments to the ciliary muscles. Its function is to focus light onto the retina.

Question 21

Describe the retina and its function.

Answer 21

The retina is the lining of the back of eye containing two types of photoreceptor cells - rods - sensitive to dim light and black and white - and cones - sensitive to colour. A small area called the fovea in the middle of the retina has many more cones than rods. Its function to contain the light receptors.

Question 22

Describe the optic nerve and its function.

Answer 22

The optic nerve is a bundle of sensory neurons at the back of eye. Its function is to carry impulses from the eye to the brain.

Question 23

Describe the pupil and its function.

Answer 23

The pupil is the small opening at the front of the eye. Its function is to allow light to enter the eye and be focused onto the retina.

Question 24

How does damage to neurons lead to debilitating illness?

Answer 24

Neurons, once differentiated, do not undergo mitosis, so cannot divide to replace lost neurons; this means damage to the nervous system can be difficult or impossible to treat.