Key term
OCR A-Level Biology B H422
The Developing Cell: Cell Division and Cell Differentiation
The Developing Individual: Meiosis, Growth and Development
The Development of Species: Evolution and Classification
Cells and Microscopy
Topic overviewMicroscopy and the cell theoryBlood smears, staining and microscope drawingsBlood cells and their structureMagnification and measuring cellsHaemocytometer cell counts and dilutionsFlow cytometry in blood analysisUltrastructure of the animal cellPlant and prokaryotic cellsMembrane lipids and the fluid mosaic modelMovement of molecules across membranesThe roles of membranes and the secretion of proteins
Water and Its Importance in Plants and Animals
Proteins and Enzymes
Nucleic Acids
Patterns of Inheritance
Population Genetics and Epigenetics
Gene Technologies
The Principles and Importance of Homeostasis
The Hormonal Control of Blood Glucose and the Management of Diabetes
Kidney Functions and Malfunctions
Topic overviewExcretion and the gross structure of the kidneyThe nephron: ultrafiltration and selective reabsorptionInvestigating the composition of urine, plasma and filtrateOsmoregulation and the action of ADHThe kidney as an endocrine gland and kidney failureDialysis, transplantation and the future of transplant surgery
The Cellular Basis of Cancer and Treatment
Respiratory Diseases and Treatment
Cellular Respiration
Metabolism and Exercise
Topic overviewThe consequences of exercise on the bodyAerobic fitness and VO₂ maxTraining, F.I.T.T. factors and investigating fitnessEnhancing athletic performanceHaemoglobin and the transport of oxygenOxygen dissociation curves of different respiratory pigmentsOxygen deficit and oxygen debtThe structure of skeletal muscleThe sliding filament theory of muscle contraction
Pathogenic Microorganisms
The Immune System
Controlling Communicable Diseases
Photosynthesis, Food Production and Management of the Environment
Topic overviewChloroplast ultrastructure and photosynthetic pigmentsThe light-dependent stage of photosynthesisThe Calvin cycleInvestigating the factors affecting photosynthesisThe Hill reaction and DCPIPUsing TP and GP to build carbohydrates, lipids and amino acidsThe compensation point and crop productionMicroorganisms, the nitrogen cycle and biosensorsBiomass transfer and efficiency in food productionRuminants in the human food chainFarms as ecosystems and the conflict with conservationDeflected succession and measuring biodiversity
The Impact of Population Increase
Planning and Implementing Practical Work
Analysing and Evaluating Practical Results
Practical Skills, Apparatus and Techniques
Topic overviewInvestigative approaches and working safelyFollowing instructions, recording and presenting dataResearch, referencing and processing data with softwareMeasuring mass, volume, time, temperature, length and pHColorimeters and potometersLaboratory glassware and serial dilutionsLight microscopy, graticules and biological drawingQualitative reagents for biological moleculesChromatography and electrophoresisAseptic technique and dissectionWhole-organism responses, fieldwork sampling and data logging
Fertility and Assisted Reproduction
The Effects of Ageing on the Reproductive System
Plant Reproduction
The Nervous System and the Identification and Consequences of Damage
Topic overviewOrganisation of the nervous system and nervous tissueThe structure and function of the human brainThe structure of motor, sensory and relay neuronesResting potential and the action potentialSynapses and the integration of responsesReflexes, reaction times and their investigationBrain scans and the consequences of nervous system damageDrugs, brain function and dependency
Monitoring Visual Function
The Effect of Ageing on the Nervous System
The Heart and Monitoring Heart Function
Transport Systems in Mammals
Gas Exchange in Mammals and Plants
The Principles and Importance of Homeostasis
- 4 subtopics
- 12 things to know
- Components 01, 02 and 03
What The Principles and Importance of Homeostasis covers
The Principles and Importance of Homeostasis is examined in all three written papers — the specification states that Components 01, 02 and 03 can each assess content from any of the five modules, so nothing is confined to one paper. It covers homeostatic principles, normal ranges and feedback, the nervous and hormonal control of heart rate, the control of body temperature and the role of thyroxine and measuring core body temperature, hypothermia and hyperthermia.
Where it is assessed
Components 01, 02 and 03
Every module can be assessed on any of the three papers.
Check the OCR specification ↗The 4 subtopics
Each one has its own page.
- Homeostatic principles, normal ranges and feedbackRecall questions on homeostasis, receptors, coordination centres and effectors, negative feedback, the normal ranges of core temperature, blood pH, fasting blood glucose and blood pressure, and positive feedback through oxytocin in labour.Open →
- The nervous and hormonal control of heart rateRecall questions on what myogenic means, the cardiovascular centre and its sympathetic and parasympathetic outputs, baroreceptor and carbon dioxide responses, and why adrenaline's effect outlasts a nerve impulse.Open →
- The control of body temperature and the role of thyroxineRecall questions on peripheral and central temperature receptors, the hypothalamus, vasodilation, vasoconstriction, sweating and shivering, and thyroxine, its TRH and TSH pathway, negative feedback control and effect on metabolic rate in prolonged cold.Open →
- Measuring core body temperature, hypothermia and hyperthermiaRecall questions on oral, tympanic, axillary and rectal temperature measurement, the thresholds for fever and hypothermia, the causes, symptoms and treatment of hypothermia, heat exhaustion and heat stroke, fuel poverty, and judging claims that climate change affects their incidence.Open →
What you need to know
Answer each one before you reveal it.
Your recallNot started
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How does a rise in the carbon dioxide concentration of the blood during exercise increase heart rate?
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How does sweating cool the body?
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What is meant by fuel poverty, and why is it a risk factor for hypothermia?
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Define homeostasis.
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The heart is described as myogenic. Explain what this means.
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Why does the body need both peripheral and central temperature receptors?
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State the four sites commonly used to measure body temperature in clinical practice.
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Name the three functional components of a homeostatic control system, in the order that information passes through them.
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Which structure sets the basic rhythm at which the heart beats?
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How does vasodilation help to lower body temperature?
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Why does a tympanic thermometer give a good estimate of core temperature?
Take The Principles and Importance of Homeostasis further
The same content, four other ways.
Commonly confused
Pairs that lose marks when they are blurred together.
Negative feedback vs Positive feedback
Negative feedback: a control loop in which the response reverses the original change and returns the factor to its set point. Positive feedback: a control loop in which the response amplifies the original change and drives the factor further from its set point.
Vasodilation vs Vasoconstriction
Vasodilation: widening of the arterioles supplying the skin capillaries, so more blood flows close to the surface and more heat is lost. Vasoconstriction: narrowing of the arterioles supplying the skin capillaries, so less blood flows close to the surface and heat is conserved.
Heat exhaustion vs Heat stroke
Heat exhaustion: a state in which the core reaches about 40 °C but the person is still sweating heavily, remains conscious and is still regulating their temperature. Heat stroke: a state in which the core rises above 40 °C, sweating has stopped, the skin is hot and dry and consciousness is impaired.
Questions from this topic
Each one with the model answer underneath.
- 1
Define homeostasis.
Model answer
Homeostasis is the maintenance of a stable internal environment within narrow limits, despite changes in the external environment.
- 2
Name the three functional components of a homeostatic control system, in the order that information passes through them.
Model answer
A receptor that detects the change, a coordination centre that processes the information, and an effector that brings about the corrective response.
- 3
How does negative feedback return a factor to its normal level?
Model answer
A receptor detects the deviation from the set point and the effector is stimulated to produce a change in the opposite direction, so the factor is brought back towards normal and the original stimulus is removed.
- 4
Why does holding temperature and pH steady matter so much for metabolism?
Model answer
Enzymes work fastest at an optimum temperature and pH, so keeping these constant maintains high reaction rates and prevents the enzymes from being denatured.
- 5
State the normal core body temperature of a healthy adult.
Model answer
Core body temperature is normally about 37 °C.
- 6
What is the normal pH range of human arterial blood?
Model answer
Blood pH is normally held between about 7.35 and 7.45.
What is inside Levo
Six ways to work the same material.
The Principles and Importance of Homeostasis revision questions
- What does The Principles and Importance of Homeostasis cover in OCR A-Level Biology B?
- 4 subtopics: homeostatic principles, normal ranges and feedback, the nervous and hormonal control of heart rate, the control of body temperature and the role of thyroxine and measuring core body temperature, hypothermia and hyperthermia. Each one has its own page with questions and model answers.
- How is The Principles and Importance of Homeostasis organised?
- By the OCR H422 specification, subtopic by subtopic, so it matches the order you are taught it in.
Every question in The Principles and Importance of Homeostasis, on a schedule.
Attempt a question from memory, write the correct version, then attempt it again. Levo records the jump between your first attempt and your last, and brings each question back on the day you are due to forget it.
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