PHSI 208 Lecture Notes - Lecture 22: Intercalated Disc, Endoplasmic Reticulum, Skeletal Muscle
Document Summary
Cardiac muscle = is made up of cardiac myocytes (myocardial muscle cells) It"s st(cid:396)iated a(cid:374)d has sa(cid:396)(cid:272)o(cid:373)e(cid:396)es (cid:272)o(cid:374)tai(cid:374)i(cid:374)g a si(cid:373)ila(cid:396) a(cid:396)(cid:396)a(cid:455) of thi(cid:272)k a(cid:374)d thi(cid:374) fila(cid:373)e(cid:374)ts, like skeletal muscles: they are not straight cylinders, but are branched. Myocardial cells are shorter, branched cells and usually contain a single nucleus. Less abundant but larger t-tubules in comparison to skeletal muscle: t-tubules are larger in diameter to e(cid:374)su(cid:396)e the(cid:396)e"s ade(cid:395)uate e(cid:454)t(cid:396)a(cid:272)ellula(cid:396) ca2, t-tubules run perpendicularly and parallel to muscle cells. Smaller amounts of sarcoplasmic reticulum: cardiac muscles require the entry of extracellular ca2, less ca2+ stored in the muscle itself, since they need ca2+ influx for muscle contraction. An abundance of mitochondria (~1/3 of cell volume: uses oxidative metabolism for atp production, they need to make lots of atp as the heart contracts continuously, they also use lots of oxygen as well. Cardiac muscle cells may contract almost 3 billion times in an average life span w/o resting.
