controlling heart rate

• why is it essential that heart rate can be changed?

  • uncontrolled can cause high pressure which can cause damage to capillaries and organs
  • exercise - needs to be higher so you can get more oxygen
  • sleep - lower rate to not waste energy
• what is an accelerator nerve?

  • a part of the sympathetic NS and delivers a higher than usual frequency of impulses to the sinoatrial node to increase the heart rate
• what is a vagus nerve?

  • opposite to accelerator nerve, part of parasympathetic NS and works to decrease heart rate by delivering a lower than usual frequency of impulses to the sinoatrial node
• what is a chemoreceptor?

  • detect chemical changes, e.g. oxygen concentration, carbon dioxide levels, pH of blood
• what is a baroreceptor?

  • detects changes in blood pressure
• what is the carotid artery?

  • primary vessels supplying blood to brain and face
• where are chemoreceptors found?

  • aorta
  • carotid artery
  • medulla
• what occurs when there is a lowered pH?

  • high CO2 concentration, carbonic acid is formed when CO2 interacts with water in the blood
  • chemoreceptors detect this and trigger increased heart rate
  • blood flows quickly to lungs so CO2 can be exhaled
• where are baroreceptors located?

  • aorta
  • vena cava
  • carotid arteries
• what is the negative feedback system of blood pressure?

  • too high, impulses sent to medulla oblongata, decrease heart rate, impulses sent along parasympathetic NS to SAN to decrease rate, back to normal
  • too low, impulses sent to medulla oblongata, increases heart rate, impulses send along sympathetic NS to SAN which increases rate, increases back to normal
• what is the role of hormones in control of the heart rate?

  • times of stress, adrenaline and noradrenaline released
  • hormones affect pacemaker region of heart, speeding up heart rate by increasing frequency of impulses produced by SAN
• what are the effects of exercise on heart rate?

  • blood pressure increases to supply cells with more oxygen and glucose
  • baroreceptor in carotid arteries detects and communicates to medulla oblongata
  • increases frequency of impulses down Vagus nerve (parasympathetic nervous system) to SAN
  • heart rate decreases
  • blood pressure returns to normal - so arteries don't sustain any unnecessary damage
• what are effects of more CO2 in blood?

  • pH decreases as more CO2 released by aerobic respiration from cells, dissolves in blood forming carbonic acid
  • chemoreceptors in carotid arteries detects and communicates to medulla oblongata
  • increases frequency of impulses down accelerator nerve (sympathetic nervous system) to SAN
  • heart rate increases
  • increased blood flow allows increased CO2 to reach lungs to be removed quicker so CO2 levels decreases, and thus the pH returns to normal