Form 4 · Common mistakes

Coordination and Response in Humans, common mistakes

The mistakes SPM students make on Coordination and Response in Humans, why each one loses marks, and the correct version.

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The mistakes, why they lose marks, and the fix

Common mistake	Why it loses marks	What earns the mark
Saying an impulse crosses the synapse electrically.	The impulse cannot jump the gap; it is carried across by a chemical neurotransmitter.	State that a neurotransmitter is released, diffuses across the gap and binds to receptors on the next neurone to start a new impulse.
Writing that reflexes are controlled by conscious thought in the brain.	A reflex is processed in the spinal cord so it can act before the brain decides, which is why it is so fast.	State that a reflex is automatic and processed in the spinal cord, not by conscious thought.
Confusing sensory and motor neurones.	They carry impulses in opposite directions, so swapping them reverses the whole pathway.	State that a sensory neurone carries impulses towards the central nervous system and a motor neurone carries them away to an effector.
Saying hormones give fast, short responses.	Hormones travel in the blood, so they are slower to act and longer-lasting than nerve impulses.	State that hormones give slower, longer-lasting and more widespread responses, while nerves give fast, short, targeted ones.
Saying insulin and glucagon do the same job.	They are antagonistic hormones with opposite effects on blood glucose concentration.	State that insulin lowers blood glucose concentration while glucagon raises it.
Saying diabetes means the pancreas has stopped working completely.	Diabetes can result from too little insulin or from cells responding poorly to it, not only from a failed pancreas.	State that diabetes arises when the body produces too little insulin or its cells respond poorly to insulin.
Naming the cerebrum as the centre for balance.	Balance and muscle coordination are controlled by the cerebellum, not the cerebrum.	State that the cerebellum controls balance and coordination, while the cerebrum controls conscious thought and voluntary action.
Treating the nervous and endocrine systems as completely independent.	The hypothalamus in the brain controls the pituitary gland, linking nervous and hormonal coordination.	State that the hypothalamus controls the pituitary gland, so a nervous signal can trigger a hormonal response.
Getting the order of the reflex arc wrong.	The five parts act in a fixed sequence, so an out-of-order answer describes an impossible pathway.	State the order as receptor, sensory neurone, relay neurone, motor neurone, effector.
Saying a hormone affects every cell it reaches.	A hormone only affects target cells that carry the matching receptor, even though it travels everywhere.	State that a hormone travels all over the body but only affects cells with the matching receptor.
Confusing a stimulus with a response.	A stimulus is the change detected by a receptor, while a response is the action of an effector, so mixing them answers the wrong part.	State that a stimulus is detected by a receptor and a response is carried out by an effector such as a muscle or gland.
Saying the medulla oblongata controls conscious movement.	The medulla oblongata controls involuntary actions such as heartbeat and breathing rate, not conscious voluntary movement.	State that the medulla oblongata controls involuntary actions, while the cerebrum controls voluntary movement.

How to avoid these mistakes

Draw and label the reflex arc and write the pathway of the impulse from receptor to effector, in the correct order.
Compare nervous and hormonal control in a table, covering speed, duration and how widely the effect spreads.
Learn the main hormones with their glands and effects, and one example of a negative feedback loop.
Learn where each hormone in this chapter is produced and at least one specific effect it has on the body.
Compare a nervous system health issue and an endocrine health issue side by side, focusing on what has stopped working normally.
Practise labelling a neurone diagram and a synapse diagram from memory, including the direction the impulse travels.

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.