pacinian corpuscle

• Some cells and organs are called receptors. They are specific and only respond to one type of stimulus (light, sound and temperature). 
• Some cell receptors contain membrane surface proteins that detect changes on the environment. The brain perceives this information so we can make sense of it. 
• Pacinian corpuscles:

  Mechanoreceptors respond to mechanical stimuli like pressure. They wont respond to any other stimuli like heat, light or sound. 
• Pacinian corpuscles:

  Most abundant on the fingers and soles of feet. Also occur in joints, ligaments and tendons so we know which joint is moving. 

   
• Pacinian corpuscles structure:

  Single sensory neuron in the centre surrounded by layers of membrane separated by a gel.
• Resting potential of Pacinian corpuscle:

  Na+/P+ pump (active transport), Na+ voltage gated channels mostly closed and K+ voltage gated channels mostly open (facilitated diffusion). 
• Generator potential:

  Na+ ion channels in Pacinian corpuscle are stretch mediated, when pressure is applied the capsule distorts - deforming the nerve endings inside and opening the Na+ ions channels. 
• Generator to action potential:

  Bigger stimulus (pressure) more Na+ ion channels open, creating a bigger potential difference across the membrane which has the potential to reach the threshold and trigger an action potential. 
• Action potential:

  Na+ ions diffuse into the cell through the stretch mediated Na+ ion channels. The membrane becomes depolarised (inside is positive), causing voltage gated Na+ ions to open so more Na+ ions rapidly diffuse.