Edexcel Biology 2105, also Science 2101, Additional Science 2103

Unit B1 b

Topic 3 — Electrical and Chemical Signals

People have always wanted to know how the brain works. Speedy responses are possible through electrical impulses in nerve cells, and some are linked to muscles by reflex arcs. Hormones can coordinate body functions, including the female menstrual cycle. The contraceptive pill and fertility treatments are examples of the ways in which sex hormones can be used medically.
Some hormones can be produced by genetic modification of bacteria for medical purposes eg in insulin production.
In this topic there are opportunities to measure and interpret data on body reactions such as reaction times and reflex actions. The development of a scientific explanation of diabetes through experiments on animals can be demonstrated and its ethical implications discussed. The application of science in controlling fertility and helping infertile couples to conceive can be considered, and the benefits, risks and drawbacks discussed.

Guidance for students

Have you ever wondered?
How does my brain tell my body what to do?
How do my hormones 'know' where to go?
How do contraceptive pills work?
Why do people with diabetics inject themselves with products from bacteria?
When travelling in a car, why do I duck down when a bird flies low over me?
Learning objectives
• The body needs to be maintained in an optimum state.
• The central nervous system lets your body respond to changes in its surroundings.
• Hormones regulate the functions of cells and organs.
• Artificial hormones can be used to control reproduction and alter body functions.
Glossary
You will be expected to be able to recall, explain, describe and use appropriately the following words and phrases:
bacteria                                glucose muscle reflex
brain                           grand mal epilepsy; oestrogen sense organs
central nervous system  (CNS) hormone pancreas stimulus
contraception                        infertility Parkinson's disease stroke
diabetes                               insulin pregnancy target organ
electrical impulse         in-vitro fertilisation(IVF)   progesterone    tumour
epilepsy                      iris reflex reaction time      voluntary
genetically modified          menstrual cycle receptor
follicle stimulating hormone (FSH) luteinising hormone (LH) genetically modified organism (GMO) motor neurone          nerve
peripheral nervous system (PNS) relay neurone sense organs sensory neurone         stimulus

Information for teachers
ICT is an integral part of the way science works, and students should be given opportunities to experience and explore its use. It is expected that ICT will be used where it enhances the learning and teaching of science and helps to make scientific concepts easier to understand.
Some of the learning outcomes have been written deliberately in order to promote discussion and expression of opinion. Where contentious, unresolved or other scientific issues are discussed, it is expected that students will be exposed to the facts, evidence and opinions from all sides of the argument.
Learning outcomes
Learning outcomes, words or statements in bold indicate that this content is designated for Higher tier students only.
Students will be assessed on their ability to:
• explore ways of measuring reaction times  B1 b 3.1
• demonstrate an understanding of the structure of the central and peripheral nervous systems, including the main regions of the brain and their functions (memory and thinking, hearing, touch, smell, taste, vision) B1 b 3.2
• explain how nerves carry electrical impulses from sense organs to muscles B1 b 3.3
• describe how strokes, brain tumours, Parkinson's disease and grand mal epilepsy disrupt the functioning of the brain
 B1 b 3.4
• explain that receptors in sense organs detect internal and external changes, allowing the body to respond to these stimuli
 B1 b 3.5
• describe the difference between voluntary and reflex responses and the advantages of reflex responses in helping to safeguard the body:
– the iris reflex
– accommodation
– 'ducking' reaction to objects travelling close to the head
 B1 b 3.6
• explain how the composition and function of the blood is related to its function
B1 b 3.7
• explain how hormones act as chemical messages affecting target organs and/or cells B1 b 3.8
• demonstrate understanding of the role and interpret data to explain that oestrogen causes the lining of the uterus to thicken during the early part of the menstrual cycle B1 b 3.9
• demonstrate understanding of the role and interpret data to explain that progesterone maintains the lining of the uterus during the middle part of the menstrual cycle and during pregnancy
B1 b 3.10
• explain how manufactured sex hormones can be used for contraception and to treat infertility in women
 B1 b 3.11
• discuss the social and ethical implications of IVF treatment, including its use in mature clients B1 b 3.12
• explain how insulin produced by the pancreas regulates glucose concentrations in the blood
 B1 b 3.13
• explain how human insulin is produced from genetically modified bacteria and the advantages of this method compared to extracting insulin from mammals. B1 b 3.14