Form 4 · Paper 2 essay guide

Coordination and Response in Humans, Paper 2 essay guide

How Coordination and Response in Humans appears in Paper 2 essays: themes, a planning grid, a model answer structure and the keyword list.

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Essay themes this chapter supports

The reflex arc and why reflexes are fast and protective: Define a reflex action as fast, automatic and involuntary. → State the five parts of the reflex arc in order. → Describe how the impulse passes from receptor to effector using a worked example. → Explain why processing in the spinal cord makes the reflex fast. → Conclude by linking the reflex to protecting the body from harm.
Comparing nervous and hormonal coordination: State that the body uses two coordination systems working together. → Describe nervous coordination using electrical impulses along neurones. → Describe hormonal coordination using chemicals carried in the blood. → Compare their speed, duration and how widely each spreads. → Conclude that nerves suit quick responses and hormones suit sustained changes.
The endocrine system and the control of blood glucose: Describe the endocrine system as glands releasing hormones into the blood. → Name the main glands with their hormones and effects. → Explain negative feedback as a change triggering a correcting response. → Describe how insulin and glucagon control blood glucose as antagonistic hormones. → Conclude by linking this control to a stable internal environment.
When coordination systems malfunction: State that both the nervous and endocrine systems can malfunction. → Explain a stroke as loss of neurones when blood supply to the brain is cut off. → Explain Parkinson's disease as the death of neurones needed for smooth movement. → Explain diabetes mellitus as too little insulin or poor response to it. → Conclude by linking each disorder to the specific part of the normal system that has failed.

How to structure your essay

Open with one or two sentences that define the topic and set the scope.
Devote one paragraph to each key concept, in a logical order.
Use precise biological terms and, where relevant, a labelled diagram.
Give an example or state where the process happens in the body or plant.
Close by linking the ideas back to the question.

Planning grid

Question	Answer
Introduction	Name the system, pathway or disorder the question is about in one clear sentence, and state the key idea behind it.
Point 1	Describe the structures involved accurately, naming the neurones, brain parts, glands or hormones as relevant.
Point 2	Explain the mechanism step by step, such as the reflex pathway, synapse transmission or negative feedback.
Point 3	Give a comparison or application, such as nervous versus hormonal coordination or a named disorder.
Conclusion	Summarise by linking the structure and mechanism back to the response or problem described in the question.

Key terms to include

stimulus
response
receptor
effector
sensory neurone
relay neurone
motor neurone
synapse
neurotransmitter
reflex arc
cerebrum
cerebellum
medulla oblongata
hormone
insulin
glucagon
negative feedback
blood glucose concentration

A model essay outline

Nervous system, The nervous system is made up of the central nervous system, the brain and spinal cord, where most information is processed and decisions are made, and the peripheral nervous system, the network of nerves that carries electrical impulses between the central nervous system and every receptor and effector in the body.
Neurones, Sensory neurones carry impulses from a receptor towards the central nervous system, motor neurones carry impulses away from the central nervous system to an effector such as a muscle or gland, and relay neurones inside the brain or spinal cord connect the two, allowing impulses to be processed or redirected.
Synapse, A synapse is a tiny gap between the end of one neurone and the start of the next. When an impulse arrives, it triggers the release of a chemical neurotransmitter that diffuses across the gap and binds to receptors on the next neurone, generating a new impulse and ensuring signals travel in one direction only.
Reflex arc, A reflex arc is a fast, automatic, involuntary pathway that does not require conscious thought: a stimulus is detected by a receptor, carried by a sensory neurone to a relay neurone in the spinal cord, passed to a motor neurone, and finally reaches an effector, which responds within a fraction of a second.
Voluntary vs involuntary actions, A voluntary action, such as picking up a pen, is consciously decided and controlled by the brain, involves the cerebrum, and can be started, changed or stopped at will. An involuntary action, such as a reflex or the beating of the heart, happens automatically without conscious control and usually protects the body or maintains an internal process.

Frequently asked questions

What is a reflex arc?

A reflex arc is the pathway of a reflex action: a receptor detects a stimulus, a sensory neurone carries the impulse to the spinal cord, a relay neurone passes it to a motor neurone, and the motor neurone triggers an effector (muscle or gland) to respond. It is fast and automatic because it does not wait for the brain to decide.

How is nervous coordination different from hormonal coordination?

Nervous coordination uses electrical impulses along neurones; it is very fast, precise and short-lasting. Hormonal coordination uses chemicals (hormones) carried in the blood; it is slower to start, more widespread and longer-lasting. The body uses both, nerves for quick responses and hormones for sustained changes such as growth.

What happens at a synapse?

A synapse is a small gap between two neurones. When an impulse reaches the end of the first neurone, it releases a chemical neurotransmitter that diffuses across the gap and triggers an impulse in the next neurone. This allows impulses to pass one way between neurones.