Chapter 3: Neurohumoral Influences

  1. Parasympathetic Stimulation (Cholinergic)
    • Control located in medulla oblongata, cardioinhibitory center 
    • Via vagus nerve (CN X), cardiac plexus
    • Innervates all myocardium
    • Releases acetylcholine
    • Slows rate and force of myocardial contraction, decreases myocardial metabolism
    • Causes coronary artery vasoconstriction
  2. Sympathetic Stimulation (Adrenergic)
    • Control located in medulla oblongata, cardioacceleratory center
    • Via cord segments T1-T4, upper thoracic to superior cervical chain ganglia
    • Innervates all but ventricular myocardium
    • Releases epinephrine and norepinephrine
  3. Sympathetic Stimulation Effects
    • Causes increase in rate and force of myocardial contraction and myocardial metabolism 
    • Causes coronary artery vasodilation
  4. The Skin and Peripheral Vasculature
    • Receive only postganglionic sympathetic innervation 
    • Causes vasoconstriction of cutaneous arteries
    • Sympathetic inhibition must occur for vasodilation
  5. Drugs
    • Sympathomimetics = increase sympathetic function
    • Sympatholytics = decrease sympathetic function
  6. Baroreceptors
    • Main mechanisms controlling HR
    • Located in walls of aortic arch and carotid sinus
    • Via vasomotor center
  7. Circulatory Reflex
    • Respond to changes in BP
    • Increased BP → parasympathetic stimulation → decreased rate and force of cardiac contraction → sympathetic inhibition → decreased peripheral resistance

    • Decreased BP → sympathetic stimulation → increased HR and BP and vasoconstriction of peripheral blood vessels 
    • Increased R atrial pressure causes reflex acceleration of heart rate
  8. Chemoreceptors
    • Located in carotid body
    • Sensitive to changes in blood chemicals (O2, CO2, lactic acid) 
    • Increased CO2/decreased O2/decreased pH (elevated lactic acid) → increased HR
    • Increased O2 → decreased HR
  9. Body Temperature
    • Increased body temp → increased HR
    • Decreased body temp → decreased HR
  10. Hyperkalemia
    • Increased concentration of potassium ions 
    • Decreases rate and force of contraction
    • Produces ECG changes (widened PR interval and QRS, tall T waves)
  11. Hypokalemia
    • Decreased concentration of potassium ions
    • Produces ECG changes (flattened T waves, prolonged PR and QT intervals) 
    • Arrhythmias 
    • May progress to ventricular fibrillation
  12. Hypercalcemia
    • Increased calcium concentration 
    • Increases heart actions
  13. Hypocalcemia
    • Decreased calcium concentrations
    • Depresses heart actions
  14. Hypermagnesemia
    • Increased magnesium
    • Calcium blocker → arrhythmias or cardiac arrest
  15. Hypomagnesemia
    Decreased magnesium → ventricular arrhythmias, coronary artery vasospasm, and sudden death
  16. Peripheral Resistance
    • Increased peripheral resistance increases arterial blood volume and pressure
    • Decreased peripheral resistance decreases arterial blood volume and pressure
    • Influenced by arterial blood volume = viscosity of blood and diameter of arterioles and capillaries
Card Set
Chapter 3: Neurohumoral Influences
NPTE: Chapter 3