3.5.9

Reflex Arc

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Components of a Reflex Arc

The different parts of a reflex arc are:

Stimulus

Stimulus

  • A stimulus can be any change in the environment to which the body needs to respond.
  • The stimulus is detected by a receptor.
Receptor

Receptor

  • Receptors are found all over the body.
  • They detect the change in the environment and initiate (start) a signalling process within the body.
  • The signal is picked up by a neurone (nerve cell).
Coordinators

Coordinators

  • There are three types of neurone (nerve cell):
    • The sensory neurone, which carries the signal in the form of an electrical impulse to the central nervous system (CNS).
    • The relay neurone (in the CNS) relays the electrical impulse from the sensory neurone to the appropriate motor neurone.
    • The motor neurone is another type of nerve cell that carries the electrical impulse from the CNS to an effector.
Effector

Effector

  • An effector is a muscle or gland that brings about an action in response to the change in the internal or external environment.
Response

Response

  • The response can be any action that helps the organism to avoid the harmful situation.
Jump to other topics
1

The Nature & Variety of Living Organisms

1.1

Characteristics of Living Organisms

1.1.1MRS GRENC1.1.2M.R.S.1.1.3G.R.E.N.C.
1.2

Variety of Living Organisms

1.2.1Types of Cells1.2.2Properties of Prokaryotes1.2.3Structure of Eukaryotic Cells1.2.4Organisms: Animals & Plants1.2.5Other Kingdoms1.2.6Pathogens1.2.7Viruses
2

Structure & Functions in Living Organisms

2.1

Organisation Structure

2.1.1Cells2.1.2Tissues2.1.3Organs2.1.4Organ Systems2.1.5Organisms2.1.6Animal cells2.1.7Plant cells2.1.8Cell Differentiation2.1.9Stem Cells2.1.10Uses of Stem Cells2.1.11Disadvantages of Stem Cells2.1.12End of Topic Test - Cell Types & Structures2.1.13Exam-Style Questions - Cells2.1.14Diffusion2.1.15Factors affecting Diffusion2.1.16Surface Area to Volume Ratio2.1.17Diffusion - Experiment2.1.18Osmosis2.1.19Required Practical - Osmosis2.1.20Active Transport2.1.21Transport in Cells2.1.22End of Topic Test - Cell Transport2.1.23Grade 9 - Cell Transport2.1.24Exam-Style Questions - Substance Exchange
2.2

Biological Molecules

2.2.1Chemical Elements2.2.2Larger Molecules2.2.3Required Practical - Food Testing2.2.4Enzymes2.2.5Rate of Enzyme Action2.2.6Investigating Effect of pH on Amylase2.2.7Grade 9 - Enzymes
2.3

Nutrition

2.3.1Photosynthesis2.3.2Photosynthesis Equation2.3.3Factors affecting Rate of Photosynthesis2.3.4Photosynthesis - Calculations2.3.5Investigating Photosynthesis2.3.6Testing Leaves for Starch2.3.7Grade 9 - Photosynthesis Experiment2.3.8Exam-Style Questions - Rate of Photosynthesis2.3.9Leaf Adaptations2.3.10Ion Deficiencies2.3.11Human Diet2.3.12Vitamins and Minerals2.3.13Dietary Needs2.3.14Human Digestive System2.3.15Peristalsis2.3.16Villi2.3.17Digestive Enzymes2.3.18Amylase2.3.19Protease2.3.20Lipase2.3.21Bile2.3.22End of Topic Test - Enzymes & Nutririon2.3.23Exam-Style Questions - Enzymes & Digestion
3

Organism Functions

3.1

Respiration

3.1.1Respiration3.1.2Aerobic and Anaerobic3.1.3Investigating Respiration3.1.4End of Topic Test - Respiration
3.2

Gas Exchange

3.2.1Guard Cells & Stomata3.2.2States of Stomata3.2.3Plant Gas Exchange3.2.4Human Thorax3.2.5Breathing Process3.2.6Gas Exchange in Lungs3.2.7Exchange Surfaces3.2.8Alveoli3.2.9Breath Composition3.2.10Exercise and Breathing3.2.11Smoking
3.3

Transport

3.3.1Surface Area to Volume Ratio3.3.2Exchange Surfaces3.3.3Examples of Exchange Surfaces3.3.4Root Hair Cells3.3.5Transpiration3.3.6Rate of Transpiration3.3.7Measuring Transpiration3.3.8Xylem3.3.9Translocation3.3.10Blood Components3.3.11Plasma3.3.12Red Blood Cell3.3.13Platelets3.3.14The Immune System3.3.15Antibodies3.3.16Vaccination3.3.17Types of Blood Vessel3.3.18Blood Vessels - Arteries3.3.19Blood Vessels - Veins3.3.20Blood Vessels - Capillaries3.3.21Function of the Heart3.3.22Structure of the Heart3.3.23Heart Rate3.3.24Heart Disease3.3.25Double Circulatory System3.3.26Important Blood Vessels3.3.27End of Topic - Transport3.3.28Exam-Style Questions - The Heart
3.4

Excretion

3.4.1Excretion3.4.2Kidneys3.4.3Urine Production3.4.4Urinary System3.4.5Nephron3.4.6Water in Urine
3.5

Coordination & Response

3.5.1Homeostasis3.5.2Regulating Internal Conditions3.5.3Coordinated Responses3.5.4Types of Tropisms3.5.5Auxin and Phototropism3.5.6Nervous System3.5.7Synapses3.5.8Reflex Actions3.5.9Reflex Arc3.5.10Sense Organs3.5.11The Eye3.5.12Eye - Focusing3.5.13Eye - Adapting to Light3.5.14Thermoregulation3.5.15Sweating and Shivering3.5.16Thermoregulation - Blood Vessels3.5.17Exam-Style Questions - Homeostasis3.5.18Endocrine Glands3.5.19Hormones3.5.20Nervous vs Endocrine3.5.21Adrenaline3.5.22Glucose3.5.23Puberty3.5.24Menstruation3.5.25Menstrual Cycle3.5.26Menstrual Hormones3.5.27Grade 9 - Hormonal Coordination3.5.28End of Topic Test - Coordination & Response
4

Reproduction & Inheritance

4.1

Reproduction

4.1.1Asexual Reproduction4.1.2Sexual Reproduction4.1.3Gamete vs Zygote4.1.4Plant Reproduction4.1.5Flower Anatomy4.1.6Germination4.1.7Pollination4.1.8Pollination Methods4.1.9Male Reproductive System4.1.10Female Reproductive System4.1.11Pregnancy4.1.12Exam-Style Questions - Sexual Reproduction
4.2

Genetics

4.2.1Cell Division4.2.2Meiosis4.2.3Genome4.2.4Genome Diagram4.2.5DNA4.2.6RNA4.2.7Protein Synthesis4.2.8Synthesis Process4.2.9End of Topic Test - Reproduction & Genetics
4.3

Variation

4.3.1Alleles4.3.2Phenotype4.3.3Monohybrid Inheritance4.3.4Punnett Square4.3.5Sex Determination4.3.6Codominance4.3.7Cystic Fibrosis Punnett Square4.3.8Cystic Fibrosis Pedigree Diagram4.3.9Variation4.3.10Mutations4.3.11Natural Selection4.3.12Evolution4.3.13Resistant Bacteria4.3.14End of Topic Test - Variation4.3.15Grade 9 - Evolution4.3.16Exam-Style Questions - Cystic Fibrosis
5

Ecology

5.1

Ecosystems

5.1.1Ecosystems5.1.2Resources5.1.3Interdependence5.1.4Growth Factors5.1.5Assessing Ecosystems5.1.6Quadrats5.1.7Required Practical5.1.8Exam-Style Questions - Sampling5.1.9Energy Flow5.1.10Food Chains5.1.11Trophic Levels5.1.12Decomposers5.1.13Pyramids of Biomass5.1.14Transfer of Biomass5.1.15Reasons for Wastage5.1.16End of Topic Test - Food and Trophic Levels5.1.17Recycling Materials5.1.18Carbon Cycle5.1.19Exam-Style Questions - Carbon Cycle5.1.20Nitrogen Cycle5.1.21The Nitrogen Cycle and Microorganisms5.1.22End of Topic Test - Ecosystems5.1.23Grade 9 - Ecosystems
5.2

Human Impacts

5.2.1Waste Management5.2.2Eutrophication5.2.3Air Pollution5.2.4Deforestation5.2.5The Greenhouse Effect5.2.6Greenhouse Gases5.2.7Global Warming5.2.8End of Topic Test - Human Impacts5.2.9Exam-Style Questions - Air Pollution
6

Biological Resources

6.1

Food Production

6.1.1Intensive Farming - Crop Yield6.1.2Intensive Farming - Ion Deficiency6.1.3Intensive Farming - Pest Control6.1.4Intensive Farming - Fish Farming6.1.5Microorganisms in Food6.1.6Factors Affecting Microorganism Growth6.1.7Industrial Fermentation6.1.8Selective Breeding6.1.9Selective Breeding Process6.1.10Uses of Selective Breeding6.1.11Exam-Style Questions - Selective Breeding
6.2

Genetic Engineering

6.2.1Genetic Engineering6.2.2Uses of Genetic Engineering6.2.3Producing Human Proteins in Bacteria6.2.4Tissue Culture6.2.5Uses of Tissue Culture6.2.6Artificial Animal Cloning6.2.7Exam-Style Questions - Mitosis & Cloning

Practice questions on Reflex Arc

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  1. 1
    Which part of a reflex arc carries the signal to the CNS?Multiple choice
  2. 2
    What happens when a motor neurone carries a signal to an effector?Multiple choice
  3. 3
    Name the stages of the reflex arc in order:Fill in the list
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Reflex Actions

Sense Organs