The autonomic nervous system often in conjunction with circulating hormones plays a critical
role in regulating both cardiac and vascular function (arterial and venous).
Sensors which monitor arterial blood pressure, blood volume, blood chemistry, and plasma
osmolarity are critical in providing afferent information to the brain. The pressure and volume
sensors are located in important locations: specific arteries, specific veins and cardiac
chambers. Likewise, blood chemistry detectors are located in specific regions of the carotid
arteries, aorta and in the medulla and plasma osmolarity detectors are found in the
Medulla, hypothalamus and cortex: regulate cardiac and vascular function depending on
NTS: nucleus tractus solidarius – site in medulla receiving input from baroreceptors and
chemoreceptors and then inhibitory and excitatory projections occur to SNS and PNS.
Projections to hypothalamus also occur (temperature control).
Vagal tone: degree of PNS activity which affects basal activity of heart (HR)
Baroreceptors at carotid sinus
The higher the pressure, the higher the number of action potentials.
Lower threshold of 50 mm Hg and upper of about 200 mm Hg
Respond more to pulsatile pressure than to constant pressure
Increases in resistance evoked by reduced pressure to carotid sinus vary among
vascular beds – greatest increase in skeletal muscles with less response in kidneys and