How do nerves and hormones coordinate the body and keep its conditions steady?
The central nervous system and the three neurones, the reflex arc as a fast automatic response, hormones as chemical messengers carried in the blood, how insulin controls blood glucose, type 1 and type 2 diabetes, and homeostasis by negative feedback.
A focused CCEA GCSE Single Award Science answer on coordination and control, covering the central nervous system and neurones, the reflex arc, hormones as chemical messengers, how insulin controls blood glucose, type 1 and type 2 diabetes, and homeostasis by negative feedback.
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What this dot point is asking
CCEA wants you to describe the central nervous system and the three types of neurone, explain the reflex arc, explain that hormones are chemical messengers carried in the blood, describe how insulin controls blood glucose, distinguish type 1 and type 2 diabetes, and explain homeostasis by negative feedback.
The nervous system
The reflex arc
The order is always: stimulus, receptor, sensory neurone, relay neurone (in the CNS), motor neurone, effector, response. Because it bypasses the conscious brain, a reflex is very fast, which is useful for protection such as pulling away from a sharp pin.
Hormones as chemical messengers
Controlling blood glucose
The pancreas keeps blood glucose steady, an example of homeostasis. When blood glucose is too high after a meal, the pancreas releases insulin, which makes cells take up glucose and the liver convert glucose to glycogen for storage, so the level falls. When glucose is too low, the liver releases glucose back into the blood.
Diabetes
Homeostasis and negative feedback
Homeostasis keeps internal conditions, such as blood glucose, steady. It often works by negative feedback: a change triggers a response that reverses the change. Adrenaline, released from the adrenal glands in fear or excitement, raises the heart rate and breathing rate and releases glucose, preparing the body for action.
Examples in context
Example 1. Why a reflex is faster than a thought. If you touch something hot, you pull away before you feel the pain. The reflex arc routes the impulse straight through the spinal cord to the muscle without waiting for the conscious brain, so the response is much faster. The pain message reaches the brain a moment later. This shows why reflexes evolved: speed protects the body from damage.
Example 2. Comparing nervous and hormonal control. Touching a hot pan is handled by the nervous system: the response is almost instant but brief. Going through puberty is handled by hormones: the response is slow to start but lasts for years. Both coordinate the body, but nerves are fast and short-lived using electrical impulses, while hormones are slow and long-lasting using chemicals in the blood. CCEA often asks you to contrast the two systems in exactly this way.
Try this
Q1. Name the two parts of the central nervous system. [1 mark]
- Cue. The brain and the spinal cord.
Q2. Name the hormone that lowers blood glucose and the organ that releases it. [2 marks]
- Cue. Insulin, released by the pancreas.
Exam-style practice questions
Practice questions written in the style of CCEA exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
CCEA SAS 20195 marksDescribe the path of a nerve impulse in a reflex action when a person touches a hot object and pulls their hand away.Show worked answer →
Five marks for the reflex arc in the correct order.
The hot object is the stimulus, detected by a receptor in the skin.
A sensory neurone carries the impulse to the central nervous system (the spinal cord).
A relay neurone passes the impulse across to a motor neurone inside the spinal cord.
The motor neurone carries the impulse to an effector, a muscle in the arm.
The muscle contracts and pulls the hand away, the response.
Markers reward the order: stimulus, receptor, sensory neurone, relay neurone, motor neurone, effector, response, and the point that it does not involve the conscious brain, so it is fast.
CCEA SAS 20214 marksExplain how the body lowers blood glucose after a meal, and state what is different in type 1 diabetes.Show worked answer →
Four marks for the control and the diabetes link.
After a meal the blood glucose rises above normal, and the pancreas detects this.
The pancreas releases insulin, which makes the body cells take up glucose and the liver convert glucose to glycogen for storage.
As a result the blood glucose falls back to the normal level, an example of negative feedback.
In type 1 diabetes the pancreas cannot make enough insulin, so blood glucose is not lowered and can rise dangerously high; it is treated with insulin injections.
Markers reward insulin from the pancreas, cells taking up glucose, liver storing glycogen, and the type 1 cause being too little insulin.
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Sources & how we know this
- CCEA GCSE Science: Single Award specification — CCEA (2017)