S1) Introduction to Body Systems

Question 1

What is normal (range) body temperature?

Answer 1

36.5 – 37.5 °C

Question 2

How can body temperature be measured?

Answer 2

Using a tympanic (ear) thermometer

Question 3

What is meant by core temperature?

Answer 3

It refers to the temperature of the internal environment of the body

Question 4

Identify and describe 3 regulatory mechanisms in the body for increased core temperature

Answer 4

• Hairs on the skin lie flat to trap less warm air
• Glands under the skin secrete sweat to increase heat loss by evaporation
• Blood vessels supplying blood to the skin dilate (vasodilation) to increase the amount of heat lost to the air

Question 5

Identify and describe 3 regulatory mechanisms in the body for decreased core temperature

Answer 5

• Hairs on the skin stand up to trap more warm air
• Blood vessels supplying blood to the skin constrict (vasoconstriction) to decrease amount of heat lost to air
• Shivering also increases heat production in muscles

Question 6

What is pyrexia?

Answer 6

Pyrexia is elevated body temperature

Question 7

How is pyrexia related to infection?

Answer 7

• Pyrogens are molecules produced by macrophages & travel in the blood to the hypothalamus
• Hypothalamus is stimulated to increase the body temperature which can kill or reduce the effectiveness of bacteria

Question 8

Why are ova bigger than spermatozoa?

Answer 8

• Ova carry the nutrients, cytoplasm and organelles necessary for cell division and growth in the zygote
• The sperm’s purpose is to carry the father’s genetic information to the egg cell so fertilisation can occur

Question 9

Where does the iodine in our diet come from?

Answer 9

• Iodated salt
• Dairy products
• Seafood
• Meat
• Eggs

Question 10

Why should pregnant women not drink organic milk?

Answer 10

• Iodine is important for the brain development of infants
• Organic milk contains 1/3 less iodine and thus can severely impact the IQ of unborn babies

Question 11

What is goitre?

Answer 11

- Goitre is an enlargement of the thyroid gland which presents as swollen neck

• It occurs when the thyroid gland does not function properly

Question 12

What is the commonest cause of goitre globally?

Answer 12

Worldwide, over 90% cases of goitre are caused by iodine deficiency

Question 13

What is homeostasis?

Answer 13

Homeostasis is the condition of equilibrium (balance) in the body’s internal environment due to the constant interaction of the body’s many regulatory processes.

E.g. the level of glucose in blood normally stays between 70 and 110 milligrams of glucose per 100 millilitres of blood.

Question 14

What is a feedback system?

Answer 14

A feedback system is a cycle of events in which the status of a body condition is monitored, evaluated, changed, re-monitored, re-evaluated, and so on

Question 15

What is a controlled condition?

Answer 15

Controlled condition: each monitored variable e.g. body temperature

Question 16

What is a stimulus?

Answer 16

Stimulus: any disruption that changes a controlled condition

Question 17

Identify the components of a feedback system

Answer 17

A feedback system includes three basic components:

• A receptor
• A control centre
• An effector

Question 18

Distinguish between positive and negative feedback mechanisms

Answer 18

• A positive feedback system tends to strengthen or reinforce a change in one of the body’s controlled conditions e.g. childbirth
• A negative feedback system reverses a change in a controlled condition (more common) e.g. blood pressure

Question 19

Distinguish between the actions of the autonomic and somatic nervous systems

Answer 19

• Autonomic Nervous System (ANS) – involuntary actions
• Somatic Nervous System – voluntary actions

Question 20

Distingush between the sympathetic and parasympathetic nervous systems in terms of:

• Actions
• Principle neurotransmitters

Answer 20

• Sympathetic nervous system – fight/flight responses (noradrenaline)
• Parasympathetic nervous system – rest and digest responses (acetylcholine)

Question 21

What does the endocrine system do?

Answer 21

The endocrine system regulates body activities in order to regulate homeostasis

Question 22

Describe the characteristic features of endocrine glands and identify 5 examples

Answer 22

Endocrine glands are ductless and secrete hormones directly into the bloodstream:

E.g. hypothalamas, pituitary gland, thyroid gland, pancreas, adrenal glands

Question 23

How much water is there in human beings?

Answer 23

Human beings are composed of 60% water

Question 24

Outline the body water distribution in a 70 kg male

Answer 24

42 litres of water = 70 kg male:

• 28 litres = Intracellular Fluid (2/3)
• 14 litres = Extracellular Fluid (1/3)

I. 11 litres = Interstitial fluid

II. 3 litres = Plasma

Question 25

Describe the composition of the circulating blood volume in humans

Answer 25

Circulating blood volume:

• 3 litres of Blood Plasma +
• 2 litres of RBC’s