Sensory receptors

• what do sensory receptors create


  nerve impulses
• change in light intensity


  light sensitive cells in retina, light to electrical
• change in temp

  temp receptors in skin and hypothalamus, heat to electrical
• change in pressure in skin

  pacinian corpuscles in skin, movement to electrical
• change in sound

  vibration receptors in cochlea of ear, movement to electrical
• movement


  hair cells in inner ear, movement to electrical
• changes in length of muscle

  muscle spindles in skeletal muscle, movement to electrical
• chemicals in air

  olfactory cells in epithelium lining in nose,
• pacinian corpuslces 


  the pressure sensor in skin
• structure of pacinian corpuslce


  oval shaped, series of concentric rings of connective tissure wrapped around nerve cell
• sodium potassium

  3 sodium ions for every 2 potassium ions, conc of na outside cell increases, conc of k inside cell increases
• hows a nerve impulse created

  by altering the permeability of the nerve cell membrane to sodium ions
• why do membranes need special channel proteins to enable movement of ions


  because narrow pores in the membrane restrict passage to ions of appropriate size and charge
• explain why a constant sound would become unoticable after a while

  the corpuscle is only sensitive to changes in pressure that deform the rings of connective tissue
• why is energy required to produce a concentration gradiant

  particles are moved against their concentration gradiant which requires active transport and atp
• explain why a concentration gradiant is needed to ensure sodium ions move rapidly into the cell

  na ions would diffuse rapidly down a concentration gradiant even without immediate availability of atp
• what is meant by facilliated diffusion

  high conc to low conc assisted by carrier