BIOL 2410 Lecture Notes - Lecture 18: Vascular Smooth Muscle, Cardiac Muscle, Smooth Muscle Tissue

• School: University of Manitoba
• Department: Biological Sciences
• Course: BIOL 2410
• Professor: Mc Lachlan Elizabeth

Document Summary

Triggered by influx of calcium through gap junctions from ap of either autorhythmic pacemaker cells or adjacent contractile cells: fast na channels open. At -90mv: na channels close fast k channels open - at the peak. At +20mv: ca channels open, fast k channels close. Plateau stage: ca channels close, slow k channels open. High permeability to k not to ca: resting potential -90mv. Refractory period of skeletal muscle vs. cardiac muscle. Skeletal muscle fast twitch fibre - the refractory period is very short compared with the amount of time required for the development of tension: a second ap cannot be generated. Skeletal muscles that are stimulated repeatedly will exhibit summation and tetanus - Cardiac muscle fibre - the refractory period lasts almost as long as the entre muscle twitch: because channels are not activated. Long refractory period in a cardiac muscle prevents tetanus: heart contracts and wont relax - good luck.