This mini-lesson covers the CCEA topic Coordination & control: how the body detects and responds to change using the nervous system and the hormonal (endocrine) system — including the three neurones, the spinal reflex arc, synapses, insulin & glucagon, negative feedback, diabetes and a touch of plant hormones.
Make a guess: how can your hand move before you think?
Mission 1How can you move before you think?
Mission 2What keeps your blood glucose steady?
Work through each screen, answer the questions as you go (some are wordy, some are calculations) and collect ⭐ stars. Press Start when you're ready.
Coordination · two systems
Nervous vs hormonal — compare & contrast
Your body responds to changes (stimuli) using two communication systems. CCEA wants you to compare and contrast them:
Nervous = fast, electrical, short-lived, targeted. Hormonal = slower, chemical, longer-lasting, can be widespread.
The brain and spinal cord make up the central nervous system (CNS).
The nervous system uses electrical impulses along neurones — very fast but short-lived.
The hormonal system releases chemical messengers (hormones) into the blood — slower to act but the effect lasts longer.
Quick check
Which system is it?
?Which system sends chemical messengers in the blood to produce slower, longer-lasting responses?
Coordination · neurones
Three types of neurone
Nerve impulses travel along neurones (nerve cells). CCEA asks you to know three types:
CCEA uses the term association neurone (other boards say relay neurone) for the one in the CNS.
Sensory neurone — carries impulses from receptors to the CNS.
Association neurone (relay) — found in the CNS; connects the sensory neurone to the motor neurone.
Motor neurone — carries impulses from the CNS to an effector (a muscle or a gland).
Synapse: where two neurones meet there is a tiny gap called a synapse. The impulse cannot jump the gap — instead a transmitter chemical (neurotransmitter) is released and diffuses across; if enough reaches the next neurone it triggers a new impulse.
Sort it
Which system does this?
Tap a statement, then tap the system it describes. (Some are true of both.)
⚡ Nervous
🩸 Hormonal
🔁 Both
Coordination · voluntary vs reflex
Voluntary and reflex actions
Some actions are under conscious control; others are automatic and protective.
Voluntary action — under conscious control; the brain decides (e.g. picking up a pen, waving).
Reflex action — automatic, very fast and not under conscious control. Reflexes protect the body (e.g. pulling your hand off a hot object, blinking, the knee-jerk).
A reflex is fast because it uses a spinal reflex arc that does not need the brain to start the response:
stimulus → receptor → sensory → association → motor → effector → responsethe neurones are joined at synapses in the spinal cord
The spinal reflex arc: it bypasses conscious thought, so the response is very fast.Quick check
Under control, or not?
?You touch a hot plate and your hand jerks away before you even think about it. Which type of action is this?
Quick check
Order the reflex arc
?In a spinal reflex arc, in which order do the impulses pass along the three neurones?
Mission 1 check
How can you move before you think?
?Walking barefoot, Sam treads on a sharp stone. His foot lifts before he even feels the pain. How can his foot move before he thinks?
Mission 2 of 2
What keeps your blood glucose steady?
Make a guess: what keeps your blood glucose steady?
Coordination · hormones · blood glucose
Hormones & controlling blood glucose
Hormones are chemical messengers that travel in the blood to a target organ, where they act. The pancreas monitors blood glucose and releases insulin, which acts on the liver (and muscles):
A change away from normal triggers a response that pushes it back towards normal — this is negative feedback.
Insulin — made by the pancreas when blood glucose rises. It makes the liver (and muscles) take up glucose, which lowers blood glucose; liver cells respire the glucose or store it as glycogen (glucose → glycogen).
When blood glucose falls, insulin release stops and the liver converts glycogen → glucose, which raises blood glucose back to normal. (A second pancreatic hormone, glucagon, triggers this — useful to know, but CCEA only names insulin.)
Negative feedback: a change away from the normal level triggers a response that reverses it, returning the level to normal (e.g. high glucose → insulin → glucose falls back to normal).
Quick check
What does insulin do?
?Blood glucose has risen after a meal. Which statement correctly describes insulin's job?
Calculate
Your turn — blood glucose change
1A person's resting blood glucose is 4 mmol/L. After a sugary meal it rises to 9 mmol/L. Calculate the increase in blood glucose.
mmol/L
Hint: increase = new value − start value = 9 − 4.
Calculate
Your turn — average reaction time
2In a ruler-drop test a student records three reaction times: 0.18 s, 0.21 s and 0.24 s. Calculate the mean (average) reaction time.
s
Hint: mean = (0.18 + 0.21 + 0.24) ÷ 3 = 0.63 ÷ 3.
Coordination · diabetes & plant hormones
Diabetes & plant hormones
Diabetes is a condition in which the blood-glucose control mechanism fails. Because glucose is not controlled properly:
Symptoms: high blood glucose, glucose present in the urine, lethargy/tiredness and thirst. Type 1 (usually early in life): the pancreas stops making insulin, so insulin is injected for life. Type 2 (linked to lifestyle and obesity): the pancreas gradually makes less insulin; managed by diet at first.
Possible long-term effects: eye damage, kidney failure, heart disease and strokes.
Plant hormones (brief):auxin controls phototropism (growth of a shoot towards light). Auxin is made at the shoot tip and moves down the shoot; light from one side causes an uneven distribution of auxin, and auxin makes cells elongate, so the shoot bends towards the light. Commercial uses include selective weed killers and rooting powder.
Quick check
Spot the symptom
?Which of these is a typical symptom of diabetes?
Mission 2 check
What keeps your blood glucose steady?
?Sam is healthy. After a large sugary drink, his blood glucose rises, then returns to normal within two hours. Which chain of events brought it back down?
Match it
Match each part to its role
Tap a part of the reflex arc on the left, then its matching role on the right.
Part
Role
Recap
The big ideas to know
Two systems: nervous = fast · electrical · short-lived · targeted; hormonal = slower · chemical · longer-lasting · widespread
Neurones: sensory (receptors → CNS) · association (links them in the CNS) · motor (CNS → effector); joined at synapses
Reflex arc: stimulus → receptor → sensory → association → motor → effector → response (fast, not conscious, protective)
Blood glucose: rises → pancreas releases insulin → liver takes up glucose, stores it as glycogen; falls → liver converts glycogen → glucose — negative feedback
Diabetes: control fails → glucose in urine, thirst, tiredness; long-term: eye/kidney/heart damage. Plant auxin → phototropism
You've covered CCEA Coordination & control. Press Finish to see your score.
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Mini-lesson complete!
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You've worked through Coordination & control for CCEA GCSE Biology. 🎉