Cardiac reflexes

Master answer

Cardiac reflex: “a fast-acting reflex loop between the heart and central nervous system that contributes to regulation of cardiac function and maintenance of physiologic homeostasis”

1. Chemo receptor reflex

• Sensor
  •  Carotid body, central chemoreceptors
• Stimulus
  • ↓in PaO₂, ↑ in PaCO₂
• Response
  • Increased SNS stimulation
  • Increased HR, SV (via increased contractility), PVR

2. Baroreceptor response (high pressure)

• Sensor
  • Arterial baroreceptors
    • Aortic arch (CN X)
    • Carotid sinus (CN IX)
• Stimulus
  • Increased MAP
    • Continuous resting tone when MAP >60mmHg
• Response
  • Increase SNS stimulation
  • Increased HR, SV (via increased contractility), PVR
    

3. Baroreceptor response (low pressure)

• Sensor
  • Atrial pressure sensors
• Stimulus
  • Atrial filling
  • Atrial contraction
• Response
  • Peripheral vasodilation
  • Increased HR
  • Also renal and hormonal effects to decrease circulating volume

4. Bainbridge reflex

• Sensor
  • Atrial stretch receptors – right atrial wall, cavoatrial jucntion
• Stimulus
  • Increased atrial blood volume
• Response
  • Increased HR

5. Cushing reflex

• Sensor
  • Medullary sympathetic cell bodies
• Stimulus
  • Compression of cell bodies with increased intracranial pressure
• Response
  • Increased SNS stimulation -> increased SVR
  • Reflex bradycardia
    • Via reflex #3

6. Oculocardiac

• Sensor
  •  Via CN III
• Stimulus
  • Ocular compression
• Response
  • Vagal stimulation -> decreased HR

7. Bezold-Jarisch reflex

• Sensor
  • Chemoreceptors and mechanoreceptors in LV wall
• Stimulus
  • Noxious chemical stimuli
• Response
  • Increase in parasympathetic outflow
  • Bradycardia
  • Peripheral vasodilation

Mooney 2016

Answer by Mooney