15.1.2

Receptors

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Receptors

Receptors have two important features:

Specificity

Specificity

  • Receptors only respond to specific stimuli. Examples of these stimuli include:
    • Light.
    • Temperature.
    • Pressure.
  • This means that a receptor that responds to light will not respond to temperature or pressure.
Generator potentials

Generator potentials

  • Receptors connect with sensory neurones. When stimulated, the receptor creates a generator potential in the sensory neurone.
  • An example where stimulation of the receptor creates a generator potential is in the Pacinian corpuscle.

The Pacinian Corpuscle

The Pacinian corpuscle is a mechanoreceptor found in the skin. Mechanoreceptors respond to changes in pressure to establish a generator potential. The receptor reacts in the following way:

Resting potential

Resting potential

  • The Pacinian corpuscle consists of concentric rings of connective tissue that surround a sensory neurone.
  • When the corpuscle is not being stimulated it is at resting state.
  • At resting state, the charge inside the neurone is more negative than outside (-70mV). This is because there are more Na+ ions outside the neurone than inside.
  • A difference in charge across the cell membrane is called the potential difference.
Stimulation of the receptor

Stimulation of the receptor

  • When pressure is applied to the Pacinian corpuscle, the rings of connective tissue apply pressure on the sensory neurone.
  • The sensory neurone has stretch mediated Na+ channels, these channels normally restrict the movement of Na+ ions.
  • Applied pressure causes the stretch-mediated Na+ channels to open.
Generator potential

Generator potential

  • Na+ ions flood into the sensory neurone through the open Na+ channels.
  • There are now more Na+ ions inside the neurone than outside.
  • The charge inside the neurone becomes more positive than outside, so the potential difference has changed.
  • The generator potential has been established.
Action potential

Action potential

  • If the generator potential reaches the threshold level (about -50mV) then an action potential is produced in the sensory neurone.
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1

Cell Structure

1.1

Cell Structure

1.1.1Studying Cells - Microscopes1.1.2Introduction to Eukaryotic & Prokaryotic Cells1.1.3Ultrastructure of Eukaryotic Cells1.1.4Ultrastructure of Eukaryotic Cells 21.1.5Ultrastructure of Eukaryotic Cells 31.1.6Prokaryotic Cells1.1.7Viruses1.1.8End of Topic Test - Cell Structure1.1.9Exam-Style Question - Microscopes1.1.10A-A* (AO2/3) - Cell Structure
2

Biological Molecules

2.1

Testing for Biological Modules

2.1.1Tests for Sugars & Starch2.1.2Tests for Lipids & Proteins
2.2

Carbohydrates & Lipids

2.2.1Monomers & Polymers2.2.2Carbohydrates2.2.3Examples of Carbohydrates2.2.4Triglycerides & Phospholipids2.2.5Types of Fatty Acids2.2.6Exam-Style Question - Carbohydrates2.2.7End of Topic Test - Carbohydrates & Lipids
2.3

Proteins

2.3.1Amino Acids & Overview of Protein Structure2.3.2Primary & Secondary Structure2.3.3Tertiary & Quaternary Structure2.3.4Globular & Fibrous Proteins2.3.5Haemoglobin2.3.6Collagen2.3.7End of Topic Test - Proteins
2.4

Water

2.4.1Water Structure & Function2.4.2End of Topic Test - Water
3

Enzymes

3.1

Enzymes

3.1.1Enzyme Action3.1.2Factors Affecting Enzyme Activity3.1.3Factors Affecting Enzyme Activity 23.1.4A-A* (AO2/3) - Enzymes
4

Cell Membranes & Transport

4.1

Biological Membranes

4.1.1Fluid Mosaic Model4.1.2Cell Signalling4.1.3End of Topic Test - Biological Membranes4.1.4Exam-Style Question - Membranes
4.2

Movement Into & Out of Cells

4.2.1Passive Movement Across the Membrane4.2.2Active Movement Across the Membrane4.2.3Osmosis4.2.4Osmosis & Plant Cells4.2.5Surface Area to Volume Ratio4.2.6Adaptions to Surface Area to Volume Ratio4.2.7Calculations - Volume4.2.8Calculations - Surface Area
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The Mitotic Cell Cycle

5.1

Replication & Division of Nuclei

5.1.1Chromosomes5.1.2The Cell Cycle5.1.3Mitosis5.1.4Role of Mitosis5.1.5Stem Cells5.1.6Mitosis & Cancer5.1.7End of Topic Test - Replication & Division5.1.8A-A* (AO2/3) - Cell Cycle & Transport
6

Nucleic Acids & Protein Synthesis

6.1

Nucleic Acids

6.1.1Introduction to DNA & RNA6.1.2Nucleotides6.1.3Polynucleotides6.1.4ADP & ATP6.1.5DNA6.1.6DNA Replication6.1.7RNA6.1.8End of Topic Test - Nucleic Acids & ATP
6.2

Protein Synthesis

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Transport in Plants

7.1

Transport in Plants

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8

Transport in Mammals

8.1

Circulatory System

8.1.1Double Circulation8.1.2Blood Vessels8.1.3Important Blood Vessels8.1.4Blood Cells8.1.5Tissue Fluid
8.2

Transport of Oxygen & Carbon Dioxide

8.2.1Haemoglobin8.2.2Oxygen Dissociation
8.3

The Heart

8.3.1Structure of the Heart8.3.2The Cardiac Cycle8.3.3Coordination of Heart Action
9

Gas Exchange

9.1

Gas Exchange System

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10

Infectious Diseases

10.1

Infectious Diseases

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10.2

Antibiotics

10.2.1Antibiotics
11

Immunity

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The Immune System

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11.2

Antibodies & Vaccination

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12

Energy & Respiration (A2 Only)

12.1

Energy

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12.2

Respiration

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13

Photosynthesis (A2 Only)

13.1

Photosynthesis

13.1.1Introduction to Photosynthesis13.1.2Light-Dependent Reactions13.1.3Light-Independent Reactions13.1.4Limiting Factors13.1.5Investigating Photosynthesis13.1.6End of Topic Test - Photosynthesis13.1.7A-A* (AO3/4) - Photosynthesis
14

Homeostasis (A2 Only)

14.1

Homeostasis

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14.2

The Kidney

14.2.1Kidneys & Osmoregulation
14.3

Cell Signalling

14.3.1Messengers & cAMP
14.4

Blood Glucose Concentration

14.4.1Blood Glucose Concentration14.4.2Controlling Blood Glucose14.4.3Urinalysis
14.5

Homeostasis in Plants

14.5.1Stomata & Guard Cells
15

Control & Coordination (A2 Only)

15.1

Control & Coordination in Mammals

15.1.1Neurones15.1.2Receptors15.1.3Taste15.1.4Reflexes15.1.5Action Potentials15.1.6Saltatory Conduction15.1.7Synapses15.1.8Cholinergic Synnapses15.1.9Neuromuscular Junction15.1.10Skeletal Muscle15.1.11Sliding Filament Theory Contraction15.1.12Sliding Filament Theory Contraction 215.1.13Menstruation15.1.14Contraceptive Pill
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Control & Co-Ordination in Plants

15.2.1Venus Flytrap15.2.2Auixns15.2.3Gibberellins
16

Inherited Change (A2 Only)

16.1

Passage of Information to Offspring

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16.2

Genes & Phenotype

16.2.1Key Terms in Genetics16.2.2Inheritance16.2.3Linkage16.2.4Multiple Alleles16.2.5Chi-Squared Test16.2.6Mutations16.2.7Specific Mutations16.2.8End of Topic Test - Genetics16.2.9A-A* (AO2/3) - Genetics
16.3

Gene Control

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17

Selection & Evolution (A2 Only)

17.1

Variation

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17.2

Natural & Artificial Selection

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17.3

Evolution

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Classification & Conservation (A2 Only)

18.1

Biodiversity

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18.2

Classification

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18.3

Conservation

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19

Genetic Technology (A2 Only)

19.1

Manipulating Genomes

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19.2

Genetic Technology Applied to Medicine

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19.3

Genetically Modified Organisms in Agriculture

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Practice questions on Receptors

Can you answer these? Test yourself with free interactive practice on Seneca — used by over 10 million students.

  1. 1
    Which of the following statements about receptors are true?True / false
  2. 2
    What type of receptor is the Pacinian corpuscle?Multiple choice
  3. 3
    Which of the following statements about the Pacinian corpuscle are true?True / false
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Neurones

Taste