PHGY 210 Lecture Notes - Lecture 4: Atrioventricular Node, Sinoatrial Node, Pericardium

• School: McGill University
• Department: Physiology
• Course: PHGY 210
• Professor: John White

Document Summary

The resistance is inversely proportional to r^2, proportional to v, and l. => the radius influence the. Control the diameter (cross section) in arterial. The arterial in small artery provide the resistance to flow. Ex: start exercise ---(cid:271)lood pressure do(cid:374)"t (cid:272)ha(cid:374)ge, the perfusio(cid:374) pressures (cid:374)o (cid:272)ha(cid:374)ge. But you need the flow to go up without changing the perfusion pressure. The resistance of the flow is falling, get dilation of vessel. (the smooth muscle cells (arterial wall) can contract or relax) The vessels get to be bigger (radius goes up), the resistance drop and the flow goes up. The accumulation of waste product act on the smooth muscle to make it relax. All the arterials are innervated by autonomic nervous system. This system can make them constrict (or sometimes relax) Hor(cid:373)o(cid:374)e (cid:272)ir(cid:272)ulati(cid:374)g i(cid:374) the (cid:271)lood (cid:894)epi(cid:374)ephri(cid:374)e, (cid:374)orepi(cid:374)e . ,(cid:895) these horo(cid:373)o(cid:374)e a(cid:272)t o(cid:374) s(cid:373)ooth muscle to make it constrict or relax.