Key Takeaways for The Human Nervous System

1. Homeostasis

  • Definition: Maintenance of a stable internal environment (e.g., blood glucose, body temperature, water balance).
  • Importance: Ensures optimal conditions for enzyme activity and cellular function.
    • Example: Blood glucose regulation prevents energy shortages (hypoglycaemia) or coma (hyperglycaemia).
  • Key Components:
    • Receptors: Detect changes (e.g., temperature receptors in skin).
    • Control Centres: Process information (brain, spinal cord, pancreas).
    • Effectors: Execute responses (muscles/glands).

Tip: Use the acronym “RICE” to remember: Receptor → Input → Control Centre → Effector.

2. Structure of the Nervous System

  • Central Nervous System (CNS): Brain + spinal cord.
  • Peripheral Nervous System (PNS): Network of nerves branching from the CNS.
  • Neurones:TypeFunctionExampleSensoryCarry impulses to CNSDetecting heat from a flameRelayTransmit impulses within CNSProcessing pain in spinal cordMotorCarry impulses from CNS to effectorsTriggering muscle contraction
  • Synapses: Gaps between neurones where neurotransmitters (e.g., dopamine) transmit signals chemically.
    • Process: Electrical impulse → neurotransmitter release → diffusion → new impulse.
    • Equation: Reaction time can be calculated using t=2dgt=g2d​​ (simplified for ruler-drop experiments).

Tip: Draw a labelled reflex arc to visualise the pathway:
Stimulus → Receptor → Sensory Neurone → Relay Neurone → Motor Neurone → Effector → Response.

3. Reflex Arcs

  • Purpose: Rapid, automatic responses to avoid harm (e.g., withdrawing hand from hot objects).
  • Pathway: Bypasses the brain to save time.
    • Example: Touching a radiator → pain receptor → spinal cord → immediate muscle contraction.
  • Key Terms:
    • Reflex Arc: Route of impulse (no brain involvement).
    • Neurotransmitters: Chemicals like acetylcholine cross synapses.

Trick: Remember “SRMR” for the neurone sequence: Sensory → Relay → Motor → Response.

4. The Brain

  • Main Regions:RegionFunctionExampleCerebral CortexConsciousness, memory, intelligenceSolving a maths problemCerebellumMuscle coordination & balanceRiding a bikeMedullaControls unconscious processes (e.g., breathing)Regulating heart rate
  • Studying the Brain: MRI scans map activity; damage studies (e.g., Broca’s area linked to speech).

Tip: Use the mnemonic “Cerebral Cortex = Clever Cat” for higher-order functions.

5. The Eye

  • Structure & Function:PartFunctionCorneaRefracts light into the eyeLensFocuses light onto retina (accommodation)RetinaContains rods (low light) and cones (colour)Optic NerveTransmits impulses to the brain
  • Accommodation:
    • Near Objects: Ciliary muscles contract → lens becomes thicker.
    • Distant Objects: Ciliary muscles relax → lens becomes thinner.

Vision Defects:

  • Myopia (short-sightedness): Corrected with concave lenses.
  • Hyperopia (long-sightedness): Corrected with convex lenses.

Example: Reading a book → lens thickens; looking at stars → lens thins.

6. Temperature Regulation

  • Mechanisms:Too HotToo ColdSweatingShiveringVasodilationVasoconstriction
  • Vasodilation: Arterioles widen → more blood to skin → heat loss.
  • Vasoconstriction: Arterioles narrow → less blood to skin → heat conserved.

Example: Exercising → flushed skin (vasodilation); cold day → pale skin (vasoconstriction).

Tip: Link to homeostasis: “Hot = Sweat & Wide Vessels; Cold = Shiver & Narrow Vessels”.

7. Practical Investigations

  • Reaction Time:
    • Method: Ruler-drop test (visual/auditory cues).
    • Variables: Independent = caffeine/alcohol; Dependent = distance caught.
    • Calculation: Convert distance to time using pre-made charts.
  • Sweating Experiment:
    • Setup: Flask wrapped in wet/dry cloth → measure cooling rate.
    • Conclusion: Evaporation of water (sweat) increases heat loss.

Trick: Use repeat readings and mean values to improve accuracy.

8. Key Equations & Terminology

  • Reaction Time: t=2dgt=g2d​​ (simplified for ruler drop).
  • Homeostasis: Negative feedback loops (e.g., body temperature regulation).

Common Mistakes:

  • Confusing vasodilation (vessel widening) with physical movement.
  • Mixing rods (low light) and cones (colour).

Final Tip: Practice past paper questions on reflex arcs and homeostasis diagrams!

50 GCSE Questions on The Human Nervous System

Section A: Homeostasis

  1. Define homeostasis.
  2. List three internal conditions regulated by homeostasis.
  3. Explain why maintaining blood glucose concentration is critical.
  4. What is the role of the thermoregulatory centre?
  5. Describe how the body responds to a rise in temperature.

Section B: Neurones & Synapses

  1. Name the three types of neurones and their functions.
  2. Why are reflex responses faster than conscious decisions?
  3. What is a synapse? Describe how signals cross it.
  4. State the formula to calculate reaction time in a ruler-drop experiment.
  5. Explain why neurotransmitters are broken down after crossing a synapse.

Section C: Reflex Arcs

  1. Draw and label a reflex arc pathway.
  2. Why does a reflex arc bypass the brain?
  3. Give an example of a reflex action.
  4. What is the role of relay neurones in a reflex arc?
  5. How does a reflex arc protect the body from harm?

Section D: The Brain

  1. Name the three main regions of the brain and their functions.
  2. What did Paul Broca discover about the brain?
  3. How does the cerebellum contribute to movement?
  4. Explain how MRI scans help study brain activity.
  5. Why is the cerebral cortex associated with intelligence?

Section E: The Eye

  1. Label the parts of the eye: cornea, lens, retina, optic nerve.
  2. What is accommodation? Describe how the lens changes shape.
  3. Compare rods and cones.
  4. Explain how hyperopia is corrected.
  5. Why can’t we focus on objects closer than the near-point?

Section F: Temperature Regulation

  1. Define vasodilation and vasoconstriction.
  2. How does sweating cool the body?
  3. Why does shivering occur when cold?
  4. What happens to blood vessels during hypothermia?
  5. Explain the term “negative feedback” in temperature regulation.

Section G: Practical Investigations

  1. Describe a method to test reaction time using a ruler.
  2. What variables should be controlled in a caffeine reaction-time experiment?
  3. How would you calculate reaction time from the distance a ruler falls?
  4. Outline an experiment to show the cooling effect of sweating.
  5. Why are repeat readings important in these experiments?

Section H: Miscellaneous

  1. What is the difference between the CNS and PNS?
  2. Name two effectors in the body.
  3. Why are sensory neurones longer than motor neurones?
  4. Describe the role of the iris in the eye.
  5. What causes myopia, and how is it corrected?
  6. Explain how the thermoregulatory centre uses skin receptors.
  7. Compare hormonal and nervous responses.
  8. What is the function of the medulla oblongata?
  9. Why do synapses slow down impulse transmission?
  10. How does the cerebellum differ from the cerebral cortex?
  11. What happens to neurotransmitters after they cross a synapse?
  12. Explain why reptiles sunbathe.
  13. Why is the fovea important for vision?
  14. Describe the role of the ciliary muscles in the eye.
  15. What is the optimum temperature for human enzymes?

Detailed Answers

  1. Homeostasis: The maintenance of a stable internal environment (e.g., blood glucose, temperature).
  2. Three conditions: Blood glucose, body temperature, water balance.
  3. Blood glucose regulation: Prevents hypoglycaemia (low energy) or hyperglycaemia (coma).
  4. Thermoregulatory centre: Monitors blood temperature and coordinates cooling/heating responses.
  5. Rise in temperature: Sweating, vasodilation, reduced metabolic rate.
  6. Neurone types:
    • Sensory: Carry impulses to CNS.
    • Relay: Transmit within CNS.
    • Motor: Carry impulses to effectors.
  7. Reflex speed: Bypasses the brain; fewer synapses.
  8. Synapse: Gap between neurones. Process: Electrical → chemical neurotransmitters → diffusion → new impulse.
  9. Formula: t=2dgt=g2d​​ (simplified for ruler drop).
  10. Neurotransmitter breakdown: Prevents continuous firing of impulses.
  11. Reflex arc pathway: Stimulus → receptor → sensory neurone → relay neurone → motor neurone → effector → response.
  12. Bypass brain: To save time and prevent injury.
  13. Example: Hand withdrawal from heat.
  14. Relay neurones: Transmit impulses within the spinal cord.
  15. Protection: Rapid response avoids tissue damage.
  16. Brain regions:
  • Cerebral cortex: Intelligence, memory.
  • Cerebellum: Balance, coordination.
  • Medulla: Controls heart rate, breathing.
  1. Broca’s discovery: Frontal lobe lesions impair speech (Broca’s area).
  2. Cerebellum: Coordinates muscle movements via spinal cord signals.
  3. MRI scans: Detect blood flow changes to map active brain regions.
  4. Cerebral cortex: Contains 19–23 billion neurones for complex tasks.
  5. Eye labels:
  • Cornea: Refracts light.
  • Lens: Focuses light.
  • Retina: Contains rods/cones.
  • Optic nerve: Transmits impulses.
  1. Accommodation:
  • Near: Ciliary muscles contract → lens thickens.
  • Far: Muscles relax → lens thins.
  1. Rods vs cones:
  • Rods: Low light, no colour.
  • Cones: Colour vision, need bright light.
  1. Hyperopia correction: Convex lenses.
  2. Near-point limit: Lens cannot thicken enough to focus.
  3. Vasodilation: Arterioles widen → more blood to skin.
    Vasoconstriction: Arterioles narrow → less blood to skin.
  4. Sweating: Evaporation removes heat energy.
  5. Shivering: Muscle contractions generate heat via respiration.
  6. Hypothermia: Vasoconstriction → pale/bluish skin.
  7. Negative feedback: Reverses changes to restore equilibrium.
  8. Ruler method:
  • Partner drops ruler; measure catch distance.
  • Convert distance to time using t=2dgt=g2d​​.
  1. Controlled variables: Same ruler, drop height, tester.
  2. Calculation: Use pre-made charts or the equation above.
  3. Sweating experiment:
  • Wrap flasks in wet/dry cloths → measure cooling rate.
  1. Repeat readings: Reduce random errors; improve reliability.
  2. CNS vs PNS:
  • CNS: Brain + spinal cord.
  • PNS: Nerves branching from CNS.
  1. Effectors: Muscles (contract) and glands (secrete hormones).
  2. Sensory neurone length: To transmit impulses from distant receptors.
  3. Iris: Controls pupil size to regulate light entry.
  4. Myopia: Eyeball too long/cornea too curved → concave lenses.
  5. Thermoregulatory centre: Uses skin receptors to detect external temperature changes.
  6. Nervous vs hormonal:
  • Nervous: Fast, electrical impulses.
  • Hormonal: Slow, chemical messengers.
  1. Medulla: Controls unconscious processes (breathing, heart rate).
  2. Synapse delay: Time needed for neurotransmitter diffusion.
  3. Cerebellum vs cortex:
  • Cerebellum: Coordinates movement.
  • Cortex: Higher-order thinking.
  1. Neurotransmitter fate: Broken down by enzymes or reabsorbed.
  2. Reptiles sunbathe: To raise body temperature (ectothermic).
  3. Fovea: High cone density for sharp vision.
  4. Ciliary muscles: Adjust lens shape during accommodation.
  5. Optimum temperature: 36.5–37.5°C (enzyme efficiency).

Study Tip: Use flashcards for key terms like synapse and vasodilation. Practice drawing diagrams of reflex arcs and the eye!