Biology · Unit 8

Nervous System and Brain

Neurons, the brain and the senses

The nervous system is a signalling problem: how do you get information from a toe to a brain fast enough to be useful, and how do you make a decision at the other end?

The unit starts with the neuron and the electrical and chemical steps that move a signal along it and across a synapse, then works outward to the spinal cord, reflexes, the brain's regions and the senses. Reflexes deserve close attention - they are the clearest demonstration that not every response involves the brain at all.

This unit breaks down into 20 short steps and 120 questions, starting at difficulty 1 and building to 3. Below you can see exactly what it covers, how the path is structured, and worked examples with explanations.

Steps: 20
Questions: 120
Difficulty: 1-3

What this unit covers

Neurons
The Brain
Spinal Cord and Reflexes
The Senses
Nerve Signals and Synapses

Where this fits

Sits well after Human Body Systems. It also connects sideways to the Psychology track, which picks up where the biology of the brain stops.

Where people slip

A nerve signal is electrical along a neuron but chemical between neurons. The switch at the synapse is where most of the difficulty lives, and it is also where almost every drug that affects the brain does its work.

How the unit is structured

Nervous System and Brain runs as 20 short steps that unlock in order. 15 are practice rounds and 5 are challenge rounds that pull together everything before them. Questions start at difficulty 1 and climb to 3 as you progress.

Step 1 · easierStep 20 · harder

Challenge rounds

Example questions

30 real questions from this unit, with the answer and the reason behind it, grouped by what they practise. There are 120 in the unit altogether.

Nerve Signals and Synapses

Multiple choiceLevel 1
1. What is a synapse?
- A tiny gap between two neuronscorrect
- The long fibre of a neuron
- A region of the brain
- A type of muscle
A synapse is the tiny gap or junction between two neurons where a signal is passed on.
Build the sentenceLevel 2
2. Build the sentence that explains what happens at a synapse.
Answer: Neurotransmitters bind to receptors on the next neuron
Neurotransmitters cross the gap and bind to receptors on the next neuron to pass the signal on.
Fill the blankLevel 2
3. Chemicals called ____ carry the nerve signal across the gap of a synapse.
- neurotransmitterscorrect
- hormones
- enzymes
- antibodies
Neurotransmitters are the chemical messengers that carry the signal across a synapse.
Match the pairsLevel 2
4. Match each neurotransmitter to its best-known role.
Answer: Acetylcholine = Triggers muscle contraction; Dopamine = Reward and movement control; Serotonin = Mood regulation; GABA = Calms and inhibits neurons
Acetylcholine drives muscle contraction, dopamine handles reward and movement, serotonin affects mood, and GABA calms neurons.
Choose all that applyLevel 3
5. Which of these are ways neurotransmitter is removed from the synaptic cleft to stop the signal? (Select all that apply.)
- Reuptake back into the presynaptic neuroncorrect
- Breakdown by enzymes such as acetylcholinesterasecorrect
- Being copied into new vesicles by the postsynaptic cell
- Absorption by red blood cells inside the cleft
Neurotransmitter is cleared by reuptake into the presynaptic terminal and by enzymatic breakdown, which ends the signal.
Guess the numberLevel 3
6. Roughly how wide is the synaptic cleft between two neurons, in nanometres?
Answer: 20 nm
The synaptic cleft is only about 20 nm wide, so neurotransmitter can diffuse across it almost instantly.

Neurons

Choose all that applyLevel 1
7. Which of these are parts of a neuron? (Select all that apply)
- Axoncorrect
- Dendritescorrect
- Cell bodycorrect
- Retina
The axon, dendrites and cell body are all parts of a neuron; the retina is part of the eye.
Multiple choiceLevel 1
8. The three main types of neuron are sensory, motor, and which other type?
- Relay neuroncorrect
- Cardiac neuron
- Optic neuron
- Vascular neuron
The three main neuron types are sensory, motor and relay neurons.
Fact or fibLevel 2
9. In saltatory conduction, the action potential jumps from one node of Ranvier to the next, speeding the impulse along a myelinated axon.
Answer: True
Myelin insulates the axon so the impulse only regenerates at the nodes, letting it jump between them and travel faster.
Fill the blankLevel 2
10. A ____ neuron connects sensory and motor neurons inside the central nervous system.
- relaycorrect
- motor
- sensory
- cardiac
Relay neurons link sensory and motor neurons within the CNS.
Guess the numberLevel 2
11. What is the typical resting membrane potential of a neuron, in millivolts?
Answer: -70 mV
A resting neuron sits at about -70 mV, with the inside of the membrane negative relative to the outside.
Match the pairsLevel 2
12. Match each part of a neuron to its job.
Answer: Dendrite = Receives incoming signals; Axon = Carries the impulse away; Cell body = Contains the nucleus; Myelin sheath = Insulates and speeds up the impulse
Dendrites receive signals, the axon carries the impulse away, the cell body holds the nucleus, and the myelin sheath insulates the axon.

Spinal Cord and Reflexes

Choose all that applyLevel 1
13. Which of these are reflex actions? (Select all that apply)
- The pupil getting smaller in bright lightcorrect
- The knee jerking when tappedcorrect
- Pulling your hand off something sharpcorrect
- Deciding to wave at a friend
The pupil narrowing, the knee jerk and pulling away from something sharp are reflexes; waving at a friend is a voluntary choice.
Fill the blankLevel 1
14. In a reflex arc, a ____ detects the stimulus and starts the nerve impulse.
- receptorcorrect
- effector
- muscle
- gland
A receptor detects the stimulus and triggers the sensory neuron to fire an impulse.
Sequence recallLevel 1
15. A reflex arc passes through three neurons. Repeat them in the order the impulse travels.
Answer: Sensory neuron -> Relay neuron -> Motor neuron
The impulse travels from the sensory neuron, to the relay neuron, then to the motor neuron.
Sort into groupsLevel 1
16. Sort each action into voluntary or involuntary.
Answer: Writing your name = Voluntary; Kicking a ball on purpose = Voluntary; Pulling your hand off a hot pan = Involuntary; Blinking when dust flies at your eye = Involuntary
Voluntary actions are chosen consciously; involuntary actions like reflexes happen automatically.
Multiple choiceLevel 2
17. Why are reflex actions so fast?
- The impulse does not have to travel to the conscious part of the braincorrect
- They use special super-fast blood cells
- They skip the spinal cord completely
- The muscles move before any nerve signal is sent
Reflexes are fast because the impulse passes through the spinal cord and does not have to travel to the conscious part of the brain first.
Put in orderLevel 2
18. Put the steps of a reflex arc in the correct order.
Answer: Stimulus -> Receptor -> Sensory neuron -> Relay neuron -> Motor neuron -> Effector -> Response
A reflex arc runs: stimulus, receptor, sensory neuron, relay neuron, motor neuron, effector, response.

The Brain

Fact or fibLevel 1
19. The brain stem controls automatic actions like breathing and heart rate.
Answer: True
The brain stem manages vital involuntary processes such as breathing and heartbeat.
Fill the blankLevel 1
20. The ____ is the part of the brain that controls balance and coordination.
- cerebellumcorrect
- cerebrum
- brain stem
- hypothalamus
The cerebellum coordinates muscle movement and helps keep the body balanced.
Multiple choiceLevel 1
21. The central nervous system (CNS) is made up of which two parts?
- The brain and the spinal cordcorrect
- The brain and the nerves in the arms
- The spinal cord and the heart
- The nerves and the muscles
The CNS consists of the brain and the spinal cord.
Odd one outLevel 1
22. Which of these is NOT a part of the brain?
- Cochleacorrect
- Cerebrum
- Cerebellum
- Brain stem
The cochlea is found in the ear; the cerebrum, cerebellum and brain stem are all brain parts.
Guess the numberLevel 2
23. How many pairs of cranial nerves does a human have?
Answer: 12 pairs
Humans have 12 pairs of cranial nerves that emerge directly from the brain.
Match the pairsLevel 2
24. Match each brain region to what it mainly controls.
Answer: Cerebrum = Thinking and memory; Cerebellum = Balance and coordination; Brain stem = Breathing and heart rate; Hypothalamus = Body temperature
The cerebrum handles thinking, the cerebellum controls balance, the brain stem controls breathing and heart rate, and the hypothalamus controls body temperature.

The Senses

Fill the blankLevel 1
25. Light-sensitive receptor cells are found in the ____ at the back of the eye.
- retinacorrect
- pupil
- iris
- cornea
The retina at the back of the eye contains the light-sensitive receptor cells.
Guess the numberLevel 1
26. How many main senses do humans traditionally have?
Answer: 5 senses
Humans traditionally have five main senses: sight, hearing, smell, taste and touch.
Match the pairsLevel 1
27. Match each sense to the organ that carries it out.
Answer: Sight = Eye; Hearing = Ear; Smell = Nose; Taste = Tongue
Sight uses the eye, hearing uses the ear, smell uses the nose, and taste uses the tongue.
Build the sentenceLevel 2
28. Build a true sentence about colour vision.
Answer: Cone cells detect colour in bright light
Cone cells detect colour and work best in bright light, while rod cells handle dim-light vision.
Fact or fibLevel 2
29. The optic nerve carries visual information from the retina to the brain.
Answer: True
The optic nerve is the cranial nerve that transmits signals from the eye's retina to the visual centres of the brain.
Choose all that applyLevel 3
30. Which statements about cone cells are correct? (Select all that apply.)
- They allow colour visioncorrect
- There are three types, sensitive to different wavelengths
- They are most concentrated at the foveacorrect
- They work best in very dim light
Cones give colour vision, come in three wavelength types and cluster at the fovea; they need bright light, unlike rods.

Where these questions come from. Each unit starts as a plan of the concepts it should cover and the difficulty it should span. Questions are written against that plan with AI assistance, then checked by a validator that rejects anything without a single defensible answer, an explanation, or plausible wrong options. How we write questions sets out the whole process, and corrections are fixed in the bank and reach the site and the app the same day.

How you practise

This unit mixes 17 different question formats, so you are recalling and applying rather than recognising the same layout every time.

Build the sentence
Choose all that apply
Fact or fib
Fill the blank
Guess the number
Listen and choose
Match the pairs
Multiple choice
Odd one out
Picture question
Put in order
Sequence recall
Sort into groups
Spell it
Tap the pairs
True or false
Type the answer

Practise Nervous System and Brain

120 questions across 20 steps. Start with step one and crawl at your own pace.

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Read about Nervous System and Brain

Explainers from our blog on what this unit covers. Each one ends with real questions from the bank.

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