LIFESCI 2 Lecture Notes - Lecture 18: Superior Vena Cava, Sinoatrial Node, Atrioventricular Node

• School: UCLA
• Department: Life Sciences
• Course: LIFESCI 2
• Professor: Arnold, A.P., Esdin, J.

Document Summary

Delay b/ atrial & ventricular contractions -> efficiency. 2 nodes don"t contract at same time ventricle contracts bottom up sinoatrial node initiates excitation wave, picked up by atrioventricular node, spreads down bundle of his, up purkinje fibers. Gap junction intercalated discs (proteins in gap junctions ensure cells are together) Action potential spreads: electrocardiogram measures heart activity each stage represents specific event of heart activity. T: ventricle relax: arteries, arterioles, capillaries, venules, and veins. Tunica intima, simple epithelium, smooth to reduce friction. Tunica media has involuntary smooth muscle to control diameter of lumen. Tunica externa has elastic & collagen fibers for flexibility: capillaries. O2, co2, hormones, nutrients, ions (some thru openings, some thru membrane: arteries close to heart, so high pressure, veins have low pressure, so working against gravity to deliver blood. So depends on squeezing of skeletal muscles to send blood to heart: blood. Made of cellular components (erythrocytes, leukocytes, and platelets) suspended in a plasma fluid.