sensory receptors

• Describe what a sensory receptor is

  
  

  detect stimuli and convert them into nervous impulses
• What does the stimulation of sensory receptors lead to

  The generation of an action potential in a neurone
• What are the four main types of sensory receptors present in animals?

  Mechanoreceptors, chemoreceptors, thermoreceptors, and photoreceptors
• How do sensory receptors function as transducers?

  • They detect stimuli
  • Convert stimuli into nervous impulses (generator potential)
• What is a generator potential?

  A nervous impulse produced by a sensory receptor in response to a stimulus
• How does a Pacinian corpuscle respond to pressure?

  It detects pressure and generates a nervous impulse
• How do sensory receptors convert stimuli into nervous impulses?

  By producing a generator potential in response to the detected stimulus
• Describe the stimulus, sense organ and example associated with a mechanoreceptor

  • STIMULUS- pressure and movement
  • EXAMPLE- pacinian corpuscle
  • SENSE ORGAN- skin- fingers and soles of the feet
• Describe the stimulus, sense organ and example associated with a chemoreceptor

  • STIMULUS- chemicals
  • EXAMPLE- olfactory receptor
  • SENSE ORGAN- nose
• Describe the stimulus, sense organ and example associated with a thermoreceptor

  • STIMULUS- heat
  • EXAMPLE- end-bulbs of Krause
  • SENSE ORGAN- tongue
• Describe the stimulus, sense organ and example associated with a photoreceptor

  • STIMULUS- light
  • EXAMPLE- cone cell
  • SENSE ORGAN- eye
• Describe sodium ion channels in the pacinian corpuscle

  • Transport sodium ions across a membrane
  • Stretch mediated sodium ion channels
  • When this channel changes shape (eg stretches) its permeability to sodium changes
• what are the two main features of all sensory receptors?

  • they act as transducers
  • they are specific to a type of stimulus
• describe the pacinian corpuscle

  • Sensory receptor
  • Detect mechanical pressure
  • Located in skin- fingers and soles of feet, or in joints
  • sensory neurones end in centre of the corpuscle, surrounded by layers of connective tissue
  • Each tissue layer separated by a layer of gel

  
• describe how the pacinian corpuscle converts mechanical pressure into a nervous impulse

  1. At resting potential, the stretch mediated sodium ion channels are too narrow to allow sodium ions to pass through them
  2. When pressure is applied to the corpuscle, it changes shape, causing the membrane surrounding its neurone to stretch
  3. Cause sodium ions channels to widen, sodium now diffuses into neurone
  4. Influx of positive sodium ions depolarises the membrane, resulting in generator potential
  5. Generator potential creates action potential that passes along sensory neurone
  6. the action potential then transmitted along neurones to the CNS