Receptors biology.

• Pacinian corpuscles?

  • pressure opens stretch mediated sodium ion channels
  • sodium ions diffuse in and change charge across membrane
  • depolarisation occurs called the *generator potential*
  • greater pressure, more channels open, more depolarisation
• Pacinian corpuscle is made of lamellar which surround the end of a sensory neurone, which contains stretch mediated sodium ion channels.
• Rhodopsin?

  • evenly around the retina
  • allow black and white vision
  • low visual activity
  • sensitive to light
• Iodopsin?

  • green, red and blue
  • present mainly in fovea
  • allow colour vision
  • not sensitive to light
  • high visual acuity for a sharp image
• Rod cells?

  • poor visual acuity as many rods are connected to one bipolar neurone
  • brains can’t distinguish the impulses
  • sensitive as enough NETs released in total by the many rods reaches action potential threshold even in low light
• Cones?

  • high visual acuity as each cone is attached to knee bipolar neurone so it can distinguish light
  • each cone cell can’t produce enough NETs unless in bright light so less likely that action potential threshold can be met, so they are less sensitive
• Control of heart rate?

  • Sino-atrial node sends electrical impulse to atrium walls
  • atria contract
  • atrioventricular node transfers electrical impulse to bundle of HIS
  • bundle of HIS conducts impulse down to purkyne fibres
  • purkyne fibres carry electrica, impulse to muscles and ventricles to contract from the base upwards
• Sympathetic nerve?

  • stimulates effectors
  • speeds up heart rate
  • fight or flight
  • NETs, noradrenaline
• Parasympathetic nerve?

  • inhibits effectors
  • controls activity at rest
  • NETs, acetylcholine
• heart rate controlled by?

  medulla oblongata

  • acceleratory centre for sympathetic nervous system
  • inhibitory for parasympathetic nervous system
• Pressure receptors in aorta and carotid artery, high blood pressure?

  • more frequent impulses from inhibitory centre in medulla to SA nice via parasympathetic
  • decreases frequency of impulses from SA node across atria
  • heart rate decreases, blood pressure returns to normal
• Pressure receptors in aorta and carotid artery, when blood pressure is low?

  • more frequent impulses from accelerators centre in medulla to SA node via sympathetic
  • increase in frequency of impulses from SA node to atria
  • heart rate increases the blood pressure goes back to normal
• Chemoreceptors when CO2 increases?

  • pH decreased
  • detected by chemoreceptors
  • impulses sent to medulla oblongata
  • increases impulses sent from accelerators centre ti sympathetic nerve
  • frequency of impulses to SA node increases
  • more blood pumped more CO2 lost
• chemoreceptors when CO2 decrease?

  • pH increases
  • detected by receptors in artery and carotid artery
  • impulses sent to the medulla oblongata
  • increases impulses send from inhibitor centre to parasympathetic nerve
  • frequency of impulses to SA node decrease
  • heart rate decreases, less CO2 lost.