Short Term Regulation of Arterial Blood Pressure Flashcards
Sympathetic Nervous System
(Fight or Flight)
Integrators
Subthalamic Locomotor Region, Cardiovascular Control Center (CVC)
Subthalamic Locomotor Region
Control Center
Subthalamic Locomotor Region Affects
Heart Rate, Arterial BP, LV Contractility
Subthalamic Locomotor Region Mechanism of Control
CVC
Subthalamic Locomotor Region Functions
Motor unit recruitment, Ventilatory Control
Cardiovascular Control Center (CVC)
Reticular Formation (Medulla and Pons; Effector arm of circulatory control (Efferent)
How many loose cnx of nerves are in medulla?
5 main areas (Pressor, Depressor, Cardioacceleration Center, Cardioinhibitory Center, Nucleus Tractus Solitarius
Pressor Area (cnx of nerves in medulla)
Increase BP via Increased Vasoconstriction (Increase Sympathetic Tone)
Depressor Area (cnx of nerves in medulla)
Reverse of Pressor (Decrease Sympathetic Tone)
Cardioacceleration Center (cnx of nerves in medulla)
Decrease HR (Via Cardiac Accel. Nerves)
Cardioinhibitory Center (cnx of nerves in medulla)
Decrease Heart Rate (Via Vagus Nerves)
Nucleus Tractus Solitarius (NTS) (cnx of nerves in medulla)
Receives afferent feedback from chemoreceptors and baroreceptors
What is the CVC effector?
The ANS
Afferents
Hypothalamus, Chemoreceptors, Baroreceptors, Muscle Afferents
Hypothalamus (Afferent) Function
Influence circulation in response to Δ Tcore (set point)
Hypothalamus (Afferent) Action
Afferent feedback to CVC (the effector)
Hypothalamus (Afferent) Opposing Messages
Hot= Anterior Hypothalamus, Cutaneous Vasodilation; Cold= Posterior Hypothalamus, Cutaneous Vasoconstriction
Chemoreceptors (Afferent) Multiple Locations
Peripheral> Aortic/ Carotid> Detects increase in pCO2, Decrease in pO2, and decrease in pH; Central> Medullary> Detects decrease in pH, increase in pCO2
Chemoreceptors (Afferent) Function
Sensitive to PCO2, PO2, pH (set point)
Chemoreceptors (Afferent) Action
Afferent signal to CVC via glossopharyngeal and vagus nerves, Causes inhibition of pressure center, Coordinates ventilatory response, High Metabolic Activity= Increased firing frequency, Low Metabolic Activity= Decreased firing frequency
Baroreceptors (Afferent) Major Arteries (high pressure)
Carotid Sinus> Glossopharyngeal> NTS; Aortic Arch> Vagus> NTS
Baroreceptors (Afferent) Heart (low pressure)
Atria; Decreased BP signals posterior pituitary, Increased BP causes atrial myocytes to release anti-aldosterone (ANP)
Baroreceptors (Afferent) Function
Sensitive to BP
Baroreceptors (Afferent) Action
Signal CVC (inhibit pressor center) via glossopharyngeal and vagus; High Flow= Increased firing frequency, Low Flow= Decreased firing frequency
Exercise Baroreflex
HR and BP increase immediately during exercise by baroreceptor “Resetting” to an increased set point; Baroreceptors play a critical role in active skeletal muscle circulation by allowing muscle vasodilation when pressure is high and muscle vasoconstriction when pressure is low (Alters Afferent Feedback Response)
Muscle Afferents
Oppose Chemoreceptors, Baroreceptors, and Autoregulation (Afferent)
4 types of muscle Afferents (only 2 cause Δ circulation)
Type III= Ergoreceptors (stretch sensitive); Type IV= Chemo & thermo sensitive
Action
Afferently signal CVC; Cardioacceleratory: Increase HR & contractility Pressor center= Increase vasoconstriction
Muscle Afferents, Mitchell paper (1983)
Type IV: Low exercise intensity (inactive/no stimuli); High exercise intensity (very active); VC in active muscle? (offset autoregulation) Explains Saltin (1988)!!!
Autoregulation: not regulated by a BCS but still very important! (Self Governance)
Blood flow increased to meet metabolic demands of tissue (Major factor during exercise); Arterioles dilate in response to: O2 Tension, CO2 Tension, Nitric Oxide, Potassium, Adenosine, pH
