Cardiovascular System: Circulation Pathways and BP Regulation General Physiology Tony Serino, Ph.D. Biology Department Misericordia University

Blood Vessels Types Arteries –conduct blood away from heart Elastic arteries, Muscular arteries, arterioles Veins –conduct blood toward heart Venules, small and large veins Capillaries –thinnest blood vessel; used in exchange, is the functional unit of circulatory system (Microcirculation) AV shunts, metarterioles, pre-capillary sphincters, and capillary bed

Capillary 12.37.jpg

Capillary Types Tight Capillary Fenestrated Capillary Sinusoidal Capillary

Capillary Bed 12.38.jpg

Forces Affecting Bulk Flow across the Capillary Wall

Artery vs. Vein Arteries are known as resistance vessels, especially the arterioles Arteries withstand the greatest BP Veins are capacitance vessels, they are able to change the diameter to hold more or less blood

Pressure Changes down CV tree Small changes in arteriolar diameter produce big changes in resistance; termed total peripheral resistance (TPR) 12.29.jpg

Elastic Recoil and Artery Contraction 12.30.jpg

Arterial Pressure Curve (Dicrotic Notch) 12.31.jpg

TPR (total peripheral resistance) TPR is the opposition to blood flow through the vessel (caused by friction) Arteries with their smaller lumen resist blood flow Arteriolar diameter contribute the most to TPR Arteriolar compliance (the ability of the vessel to distend) controls the TPR Sympathetic innervation controls arteriolar radius The viscosity of the blood also affects resistance

Small changes in Arteriole Diameter create large changes in BP 12.49.jpg

Blood Flow Velocity in Vascular Tree

Blood Flow Regulation is mainly a Local Response 12.34.jpg Understand Reactive Hyperemia and Inflammation; ANS control modifies BF based on “whole body needs”

ANS Control of Arterioles 12.35.jpg (Alpha receptors outnumber Beta in most vascular beds; except in skeletal muscles. Here epinephrine causes vasodilation)

Modifiers of Arteriolar Radius 12.36.jpg

Adjustment of Perfusion to Exercise 12.61.jpg

CV Adjustment to Exercise 12.62.jpg

Some Exercise Physiology Mechanisms 12.63.jpg

Atherosclerotic plaques are a primary cause of hypertension due to Increase in TPR

Capacitance Vessels (Veins) Skeletal Muscle Pump 12.44.jpg

Fig. 12.46 12.46.jpg

Blood Pressure BP = SP/DP Systolic Pressure (SP) –the pressure in the artery during systole Diastolic Pressure (DP) –the pressure in the artery during diastole Mean Arterial Pressure (MAP) (weighted average) MAP = DP + 1/3 (PP) Pulse Pressure (PP) = SP - DP MAP = CO x TPR

SP DP

Baroreceptor Locations

3. Increased parasympathetic Carotid sinus baroreceptors 1. Baroreceptors in the carotid sinus and aortic arch monitor blood pressure. 2. Action potentials are conducted by the glossopharyngeal and vagus nerves to the cardioregulatory and vasomotor centers in the medulla oblongata. 3. Increased parasympathetic stimulation of the heart decreases the heart rate. 4. Increased sympathetic stimulation of the heart increases the heart rate and stroke volume. 5. Increased sympathetic stimulation of blood vessels increases vasoconstriction. 1 Aortic arch baroreceptors Glossopharyngeal nerve 3 Vagus nerve 2 Vagus nerve (parasympathetic) Cardioregulatory and vasomotor centers in the medulla oblongata 4 Sympathetic nerves Sympathetic chain 5 Blood vessels

Better at controlling BP drops than rise Better at controlling BP drops than rise. High BP causes shift in set point of receptors similar to exercise.

Baroreceptor Reflex (Note: if decrease BP: arrows reverse) 12.55.jpg

Renal Hormonal Control of BP (ACE) ↑ BP ↑ blood volume

Other Renal Mechanisms affecting BP (ADH) ↑ blood volume ↑ BP ↓ blood volume ↓ BP

Mechanism of BV changes on BP 12.57.jpg

Overview of BP Regulation 12.51.jpg

12.08.jpg

Hemorrhage Compensation Response Primary Effects 12.56.jpg

Fig. 12.58 12.58.jpg

Fig. 12.06 12.06.jpg

Fig. 12.47 12.47.jpg

Elephantiasis Vector : mosquito Pathogen: filaria worms blocking lymph vessels 12.48.jpg