Grade 12 Biology Unit 5 : Human Body System

This unit, “Human Body System,” shows you how your body controls itself and stays balanced through two coordinating systems: the fast-acting nervous system and the slower endocrine system. You’ll follow a nerve signal from one cell to the next, learn how your skin, tongue, nose, eyes, and ears collect information about the world, and discover how hormones and the kidney keep your internal conditions steady even as the outside world changes.

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Chapter 5.1 – The Nervous System

This chapter covers the cells and signals that carry messages around your body at high speed.

• Neurons and their functions: Describe the structure of a neuron — the cell body, dendrites, and axon — and explain how the myelin sheath speeds up signals.
• The Nerve Impulse and transmission: Explain how an electrical impulse travels along an axon and how it is passed on.
• Neurotransmitters: Define a neurotransmitter as the chemical that carries the signal across the synapse between two neurons.
• Types of the nervous system: Identify the central nervous system (brain and spinal cord) and the peripheral nervous system, and state the job of each.

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Chapter 5.1.6 & 5.1.7 – Reflex Action and Drug Abuse

This part looks at automatic responses and how drugs harm the nervous system.

• Reflex action: Explain a reflex as a fast, automatic response and trace the reflex arc with an example.
• Drug abuse: Describe how abused drugs change the way neurons work and analyse their effects on the body and behaviour.

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Chapter 5.2 – Sense Organs

This chapter covers the organs that detect stimuli from your surroundings.

• Skin, Tongue, and Nose: Identify how the skin senses touch and temperature, and how the tongue and nose detect taste and smell.
• The Eye: Explain how the eye bends light to form an image on the retina.
• The Ear: Describe how the ear turns sound waves into nerve signals and helps you keep balance.

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Chapter 5.2.6 – The Endocrine System

This chapter explains how glands control the body using hormones.

• Hormones: Define a hormone as a chemical messenger carried in the blood to target cells.
• The endocrine glands: Identify the main endocrine glands and describe how their hormones regulate body processes.

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Chapter 5.3 – Homeostasis in the Human Body

This chapter explains how your body keeps its internal conditions stable.

• Homeostasis: Define homeostasis and explain how negative feedback returns the body to normal.
• The structure and function of the human kidney: Describe how the kidney removes waste and controls water balance to keep the internal environment steady.

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Learning Outcomes

By the end of this unit, you will be able to:

• Explain the structure and functions of the nervous system, including neurons, nerve impulses, and neurotransmitters.
• Compare the central and peripheral nervous systems and explain a reflex arc.
• Describe how the sense organs detect stimuli and send signals to the brain.
• Explain how the endocrine glands and their hormones coordinate the body.
• Explain homeostasis and describe how the kidney keeps internal conditions stable.
• Describe the effects of drug abuse on the nervous system.