I. Nervous Control

A.  Autonomic Nervous System (ANS)

1. Parasympathetic Relaxation

      • controlled by the cardio-inhibitory center of the medulla oblongata
      • via the Vagus Nerve acetylcholine DECREASES heart rate

2. Sympathetic Stimulation

      • controlled by the cardio-acceleratory center of the medulla oblongata
      • via the Accelerator Nerve nor-epinephrine INCREASES heart rate

B.  Cardiac Reflexes

1. Chemoreceptors

      • located in the aortic arch & carotid sinus
      • monitors pO2, pCO2, & pH
      • low pO2, high pCO2, & low pH stimulate cardio-acceleratory center
      • increased heart rate increases cardiac output increases pulmonary blood flow

2. Baroreceptors (= Pressoreceptors)

a.  Marey's Law of the Heart (= Aortic Reflex + Carotid Sinus Reflex) [ARTERIAL BP]

        • increased arterial BP stimulates stretch receptors in aortic arch and/or carotid sinus
        • sensory neurons travel to cardio-inhibitory center Vagus Nerve acetylcholine released
        • heart rate DECREASES (decreases "pushing") decreases cardiac output decreases arterial blood volume decreases arterial BP

b.  Bainbridge Reflex (= Right Atrial Reflex) [VENOUS BP]

        • increased venous BP stimulates stretch receptors in right atrium (= Vena Cavae)
        • sensory neurons travel to cardio-acceleratory center Accelerator Nerve nor-epinephrine released
        • heart rate INCREASES (increases "pulling") decreases venous blood volume decreases venous BP

II. Endocrine Control

A.   Adrenal Medulla

B.   Thyroid

III.  Serum Control

A.  Sodium (Na+)

B.  Potassium (K+)

C.  Calcium (Ca++)

D.  Magnesium (Mg++)