|
Baroreceptors
  • Baroreceptors
    • overview 
      • baroreceptors, aka mechanoreceptors, sense changes in arterial pressure
        • "pressure sensors" located in walls of carotid sinus and aortic arch
          • respond to stretching
    • carotid sinus
      • baroreceptors that respond to ↑ AND ↓ in arterial pressure (aka BP)
        • transmit to brainstem via carotid sinus nerve
          • carotid sinus nerve joins with glossopharyngeal nerve (CN IX)
            • CN IX synapses in nucleus tractus solitarius of medulla
    • aortic arch
      • baroreceptors that respond ONLY to ↑ in arterial pressure (aka BP)
        • transmit to brainstem via vagus nerve (CN X)
          • CN X synapses in nucleus tractus solitarius of medulla
  • Baroreceptor reflex
    • overview
      • a fast, neurally-mediated reflex that attempts to keep arterial pressure constant via changes in output of sympathetic and parasympathetic nervous systems in the heart and blood vessels
      • note: the description below is an example of the baroreceptor reflex in response to a decrease in blood pressure. If blood pressure were increased the response would be exactly the opposite of below.
      • description 
        • (1) ↓ in BP is sensed by baroreceptors in carotid sinus
          • decrease in blood pressure = decrease in stretch
        • (2) ↓ in stretch causes ↓ firing of afferent nerves
          • carotid sinus nerve (glossopharyngeal nerve, CN IX)
          • vagus nerve (CN X)
        • (3) glossopharyngeal and vagus nerves synapse in nucleus tractus solutarius
          • nerves relay ↓ in blood pressure to brain
        • (4) nucleus tractus solutarius directs a series of coordinated responses using medullary cardiovascular centers that increases blood pressure
    • e.g., hypotension and hemorrhage (↓ arterial pressure)
      • ↓ arterial pressure → ↓ stretch → ↓ afferent baroreceptor firing → ↑ efferent sympathetic firing and ↓ efferent parasympathetic firing →
        • vasoconstriction
        • ↑ HR
        • ↑ contractility
        • BP
    • e.g., carotid massage
      • ↑ pressure on carotid artery → ↑ stretch → ↑ afferent baroreceptor firing → HR   
    • Cushing reaction
      • mechanism
        • increase in intracranial pressure constricts cerebral arteries
          • causes cerebral ischemia
        • cerebral ischemia induces hypertension (sympathetic response)
          • causes reflex bradycardia
      • Cushing triad
        • hypertension, bradycardia, and respiratory depression
Chemoreceptors
  • Chemoreceptors 
    • peripheral chemoreceptors
      • receptors in carotid sinus and aortic arch sense ↓ PO2, ↑ PCO2, ↓ pH
        • ↓ PO2 (if PO2 < 60 mmHg)
      • carotid bodies
        • aka chemoreceptors in carotid sinus
        • transmit to brainstem via carotid sinus nerve
          • carotid sinus nerve joins with glossopharyngeal nerve (CN IX)
            • CN IX synapses in nucleus tractus solitarius of medulla
      • aortic bodies
        • aka chemoreceptors in aortic arch
        • transmit to brainstem via vagus nerve (CN X)
          • CN X synapses in nucleus tractus solitarius of medulla
    • central chemoreceptors
      • receptors in medulla sense ↑/↓ PCO2, ↑/↓ pH (NOT ↑/↓ PO2) in brain fluid
        • PCO2, pH influenced by arterial CO2
 
 

Please rate topic.

Average 4.8 of 4 Ratings

Questions (2)
EVIDENCE & REFERENCES (2)
Topic COMMENTS (11)
Private Note