Receptors

• Receptors

  • only detect one type of stimulus
  • all receptors are transducers
• Pacinian Corpuscle

  = mechanoreceptor which detects pressure and vibrations in the skin.

  • encapsulated nerve ending surrounded by layers of connective tissue and gel.
  • within the membrane of the neurone there are sodium ion channels- responsible for transporting sodium across the membrane
  • the neurone ending has a stretch-mediated sodium channel, when they change shape (stretch) their permeability to sodium also changes.
• How a pacinian corpuscle converts converts mechanical pressure into a nervous impulse

  1 in its resting state, the stretch-mediated sodium ion channels are too narrow to allow sodium ions to pass through, the neurone has a resting potential.

  2 when pressure is applied to the pacinian corpuscle, the corpuscle changes shape which causes the membrane surrounding its neurone to stretch.
• 3 when the membrane stretches the sodium ion channels present widen so sodium ions diffuse into the neurone

  4 the influx of positive sodium changes the potential of the membrane which becomes depolarised. This results in a generator potential.

  5 the generator potential creates an action potential (nerve impulse) that passes along the sensory neurone