D neural/hormonal control mechanism and receptors

• sympathetic system stimulates heart to beat faster
• parasympathetic system returns heart to resting level
• nervous system

  consists of:

  • central nervous system
  • peripheral nervous system
• central nervous system

  • brain
  • spinal cord
• peripheral nervous system

  • nerve cells
  • transmit information to and from central nervous system
• CNS and PNS co-ordinated by cardiac control centre located in medulla oblongata
• where are chemoreceptors found?

  • cartoid arteries
  • aortic arch
• what do chemoreceptors do?

  • detect changes in blood acidity caused by increase or decrease in concentration of CO2
  • increased concentration of CO2 stimulates sympathetic nervous system
• where are baroreceptors located?

  • aortic arch
  • cartoid sinus
  • heart
  • pulmonary vessels
• what do baroreceptors do?

  • contain nerve endings
  • respond to changes in blood pressure to stimulate either sympathetic or parasympathetic nervous system
• how do baroreceptors carry out their job?

  • establish set point for blood pressure
  • increase in arterial pressure causes nerve endings to stretch resulting in decrease in heart rate
  • decrease in arterial pressure causes decrease in stretch resulting in increase in heart rate
• baroreceptors set point increases at start of exercise as body does not want heart rate to slow down
• where are proprioceptors located?

  • muscles
  • tendons
  • joints
• What do proprioceptors do?

  • provide information about movement and body position
• how do proprioceptors work at the start of exercise?

  • detect increase in muscle movement
  • send impulse to medulla oblongata
  • impulse then sent to SAN via sympathetic nervous system
  • heart rate increases
• adrenaline

  stress hormone released by sympathetic and cardiac nerves during exercise
• what does adrenaline do?

  • stimulates SAN
  • causes increase in speed and force of contraction
  • increases cardiac output