PHIS 206 1st Edition Lecture 11 Outline of Last Lecture I 3 Categories of Muscles II Skeletal Muscle III Muscle Physiology IV Muscle Cell Contractions V Muscles Are Elastic Muscle Types Outline of Current Lecture I Muscle Mechanics Skeletal Muscles II Smooth Muscles III Cardiac Muscles IV Atrial and Ventricular V Mechanism of Stimulation Cardiac Muscle VI Cardiac Cycle Current Lecture I Muscle Mechanics Skeletal Muscles Brief shock administered brief contraction shock Tetanic stimulus no relaxation between stimuli Long contractions deliver a tetanic stimulus Muscles contract and do not relax for anything above 60 s cycle Vary strength of contraction how many muscle cells contracting simultaneously strength goes up by increasing of muscle cells o motor neurons spread out and innervate more that 1 muscle cell o in some muscles selectively stimulate very few muscle cells Motor unit 1 motor neuron and all of the muscle cells it innervates so all cells simultaneously contract fine movements smaller motor units SUMMARY can vary duration of contraction and strength of stimulus in skeletal muscles II Smooth Muscles No striations because myosin and actin are organized in all directions irregular Can contract in several planes shorter narrower etc Rate of contraction is slower and less forceful because of the irregular elements Can propagate action potentials from 1 cell to another CANNOT for SKELETAL These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute conductive cells if stimulated everything wave of contraction will contract relax at the same time Smooth muscles will relax if waste product increase and O2 production decreases III Cardiac Muscles hybrid between skeletal and smooth is striated and cylindrical like SKELETAL muscle action potential can propagate in 1 direction like SMOOTH muscle NOTE Smooth muscles however can propagate action potentials in ALL directions 3 Basic Types 1 Atrial 2 Ventricular 3 Conductive In any tissue a group of cells that are connected so that they can transmit action potentials to each other syncytium IV Atrial and Ventricular Similarities look like striated muscle cells contractile generate action potentials Differences Duration of plateau refractory period atrial 150 millisec v ventricular 300 millisec atrial maximum rate of contraction is 360 minute ventricular maxium rate of contraction is 180 minute atrial contracts with more frequency longer refractory period Mechanism of Stimulation Cardiac Muscle same as routine of skeletal muscle sarcolemma sarcoplasm etc rhythmic contraction b c of rather leaky cells different parts of heart have different levels of leakiness o Drift rapidly if more leaky higher frequencies to reach thresholds o Drift slowly if less leaky lower frequencies to reach thresholds Cardiac Cycle from one end of the contraction to another left ventricular pumps blood to everywhere except lungs 2 Gross Phases 1 Systole heart contracting 2 Diastole heart resting Sino Atrial S A Node most leaky generates action potentials more frequently than any other parts of the heart V VI 90 millisec for cycle from S A node to entire atrial and back
View Full Document
Unlocking...