sympathetic activity – venous smooth muscle has an abundant nervous innervation by the sympathetic nervous division
{"Image DocumentName": "sympathetic activity \u2013 venous smooth muscle has an abundant nervous innervation by the sympathetic nervous division", "Image ImageDescription": "can produce a small amount of constriction in the veins increasing venous BP and increasing the forces driving blood back to the heart. this contraction also decreases the amount of blood that can be held in the veins (decreases venous capacity) by decreasing the diameter of the vein itself. so less blood remains in the veins but is returned faster to the heart. skeletal muscle activity \u2013 contraction of skeletal muscles can push on the vein walls, decreasing their size and decreasing their capacity. venous valves \u2013 venous vasoconstriction and skeletal muscle contraction also drive blood away from the heart. -evolved extensions off the endothelium \u2013 valves. -these valves can shut off sections of veins to prevent back-flow towards the feet when standing. 4. respiratory activity\u2013 pressure in the chest is 5 mm Hg less than atmospheric. blood flowing through the thoracic cavity on the way back to the heart is exposed to subatmospheric conditions. this creates a pressure differential between the pressure in the limb veins and those in the thoracic region veins \u2013 drives more blood from the limbs = respiratory pump.", "Image XResolution": "37", "Image YResolution": "37", "Image ResolutionUnit": "Pixels/Centimeter", "Image Software": "SlidePlayer", "Image YCbCrPositioning": "Centered"}