What are the central integrating parts of the brain/SC associated wtih baroreceptor regulation?
Rostral Ventrolateral Medulla (RVLM)
Nucleus Tractus Solitarius
Where are the high pressure receptors found? What do they sense?
Found in the Media of the Carotid Sinus and Aortic arch
stretch receptors in medial muscle layer for stretch and recoil sensing at higher pressures
Where are the low pressure baroreceptors and what do they sense?
Found in RA at junction of SVC and IVS and in LA at junction of 4 pulmonary veins
Sense low pressure on venous side ~5 mm HG
Sense LA pressure from pulmonary veins ~ 8-12 mmHG
What and where are the Vagal C Fibers? What is the funny-named reflex that occurs? What purpose does this serve?
Stimulation of Vagal C fibers leads to Bradycardia, Hypotension and BRief Apnea in the Bezold-Jarisch Reflex
Sensory receptors in LV that inhibit Sympathetic to heart and increase Parasympathetic
Found in LV Endocardium and if hyperdynamic collapsing dramatically then they will get stimulated so don't rub together anymore
Characteristics of Baroreceptors?
More sensitive to Pulsatile pressure than constant pressure - respond to dynamic changes in pressure AND more to pulse pressure than to MAP
Increased Baroreceptor firing leads to Inhibition of tonic discharge of sympathetic nerves and excitation of vagal innervation of the heart
Activation leads to vasoconstriction (splanchnics most responsive) and withdrawal of sympathetic tone leads to vasodilation
*In Skeletal Muscle see Sympathetic Cholinergic Vasodilation
Describe the Valsalva Maneuver and what happens during the phases of it.
Used to slow HR and regulate SVT
Strain Phase: bear down and increase intrathoracic pressure
- Increase MAP and baroreceptors fire more to decrease HR
- Then pressure falls from decreased return from venous to heart and baroreceptors sense decrease BP and fire less to increase sympathetic and HR ramps up
Release Phase: breath and get transient decrease in BP from release and low blood circulating
- Immediately followed by INCREASE venous return to heart AND increase in HR - baroreceptors fire like crazy
- HR then drops dramatically for a sustained amount of time and increased vagal tone