Sensory receptors

• What is the specification reference for the study material?

  1. 1.3
• What are the specialized cells that detect changes in the environment called?

  Sensory receptors
• Where are sensory receptors often located?

  In sense organs, such as the ear and eye
• What do sensory receptors convert stimuli into?

  A nerve impulse
• What is the role of the brain in response to stimuli detected by sensory receptors?

  The brain coordinates the required response and sends an impulse to an effector
• What are the two main features of sensory receptors?

  They are specific to a single type of stimulus and act as transducers
• What are the four main types of sensory receptors in animals?

  • Mechanoreceptors
  • Chemoreceptors
  • Thermoreceptors
  • Photoreceptors
• What type of stimulus do mechanoreceptors detect?

  Pressure and movement
• What is an example of a mechanoreceptor?

  Pacinian corpuscle
• What type of stimulus do chemoreceptors detect?

  Chemicals
• What is an example of a chemoreceptor?

  Olfactory receptor
• What type of stimulus do thermoreceptors detect?

  Heat
• What is an example of a thermoreceptor?

  End bulbs of Krause
• What type of stimulus do photoreceptors detect?

  Light
• What is an example of a photoreceptor?

  Cone cell
• How do sensory receptors function as transducers?

  • Detect a range of stimuli (light, heat, sound, pressure)
  • Convert the stimulus into a nervous impulse (generator potential)
• What is a generator potential?


  A nervous impulse produced by sensory receptors in response to a stimulus
• What do Pacinian corpuscles specifically detect?

  Mechanical pressure
• Where are Pacinian corpuscles located?

  Deep within the skin, especially in fingers and soles of the feet
• What do Pacinian corpuscles respond to?

  Vibration and deep pressure
• Describe the structure of a Pacinian corpuscle.

  • Sensory neurone ending in the center
  • Surrounded by layers of connective tissue
  • Each layer separated by a layer of gel
• What type of sodium channels are found in the neurone ending of a Pacinian corpuscle?

  Stretch-mediated sodium channels
• What happens to the sodium channels when the membrane of a Pacinian corpuscle stretches?

  The sodium channels widen, allowing sodium ions to diffuse into the neurone
• What are the steps involved in converting mechanical pressure into a nervous impulse in a Pacinian corpuscle?

  1. Resting state: sodium channels are narrow, resting potential exists
  2. Pressure applied: corpuscle changes shape, membrane stretches
  3. Sodium channels widen: sodium ions diffuse into the neurone
  4. Depolarization: influx of sodium ions creates a generator potential
  5. Action potential: generator potential creates an action potential that passes along the sensory neurone
• What is the final outcome of the action potential generated by a Pacinian corpuscle?

  The action potential is transmitted along neurones to the CNS