Homeostasis and the Nervous System

Year 1 / ASYear 2 / A-Level All Boards (AQA, Edexcel, OCR, WJEC, CCEA) AQA

A-Level Biology revision: Homeostasis and the Nervous System. Learning objectives, key points, worked examples and practice questions across AQA, Edexcel, OCR, WJEC and CCEA.

Exam Board:

📌 Key Points

Key Fact: Negative feedback: deviation -> correction (e.g. blood glucose, temp, water); Positive: amplifies (e.g. oxytocin in childbirth)

Key Fact: Kidney: cortex/medulla; nephron (Bowman's capsule, PCT, loop of Henle, DCT, collecting duct); ADH: increases water permeability of DCT/CD; Loop: counter-current multiplier creates medullary gradient

Key Fact: Neurones: sensory, relay, motor; Resting potential -70mV (Na⁺/K⁺ pump, K⁺ leak); Action potential: depolarisation (Na⁺ in), repolarisation (K⁺ out), refractory period

Key Fact: Synapse: Ca^2⁺ -> vesicle fusion -> neurotransmitter -> receptor -> depolarisation; Summation: temporal/spatial

Key Fact: Hormones: insulin (β-cells, lowers glucose), glucagon (α-cells, raises glucose), adrenaline (fight/flight), thyroxine (metabolic rate); Diabetes: type 1 (no insulin), type 2 (insulin resistance)

🎯 Learning Objectives

Explain homeostasis: set point, receptors, effectors, negative/positive feedback
Detail kidney structure and osmoregulation (ADH, loop of Henle)
Describe nervous system: CNS/PNS, neurone types, resting/action potential, synapses
Explain hormonal control: endocrine glands, insulin/glucagon, adrenaline, thyroxine
Understand temperature regulation: hypothalamus, vasodilation/constriction, sweating, shivering

💡 Worked Example

Exam-Style Question

Question: Describe how the loop of Henle creates a water potential gradient in the kidney medulla

Model Answer:

Descending limb: permeable to water, impermeable to ions -> water leaves by osmosis. Ascending limb: impermeable to water, active Na⁺/Cl⁻ transport out -> filtrate diluted, medulla concentrated. Counter-current multiplier: flow in opposite directions maintains gradient

❓ Practice Questions

Model answers are being added progressively - questions marked ✗ don't have one yet. Cross-check with your teacher or the official mark scheme.

Questions:

Define homeostasis✗ answer coming soon
Explain action potential phases✗ answer coming soon
How does insulin lower blood glucose?✗ answer coming soon
Role of hypothalamus in thermoregulation✗ answer coming soon
Difference between type 1 and type 2 diabetes✗ answer coming soon

🎬 Video Resources

Homeostasis and the Nervous System - Overview -- YouTube Search
Homeostasis and the Nervous System - Exam Questions -- YouTube Search

📄 Past Papers & Exam Resources

🔗 Further Reading & Resources

Physics & Maths Tutor - Homeostasis and the Nervous System -- Free notes, worksheets, and past paper questions by topic
Dr Frost Maths - Homeostasis and the Nervous System -- Free resources, slides, and interactive questions
BBC Bitesize - Homeostasis and the Nervous System -- BBC Bitesize revision resources

📚 Lesson Plan (50 minutes)

Starter (5 min): Recall prior knowledge of homeostasis and the nervous system with quick questions.
Teaching (15 min): Work through each of the learning objectives, explaining principles step by step.
Key points review (5 min): Revisit the key points together, confirming understanding.
Worked example (10 min): Model the example question: Describe how the loop of Henle creates a water potential gradient in the kidney medulla. Solution: Descending limb: permeable to water, impermeable to ions -> water leaves by osmosis. Ascending limb: impermeable to water, active Na⁺/Cl⁻ transport out -> filtrate diluted, medulla concentrated. Counter-current multiplier: flow in opposite directions maintains gradient
Practice (10 min): Students attempt the practice questions independently; circulate and support.
Plenary (5 min): Review answers and address misconceptions.

🏠 Homework

Define homeostasis
Explain action potential phases
How does insulin lower blood glucose?
Role of hypothalamus in thermoregulation
Difference between type 1 and type 2 diabetes

🧾 Assessment

Check practice answers against the model answer; use the built-in practice questions as formative assessment.

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