PHIS 206 1st Edition Exam 2 Study Guide Lectures 10 18 Lecture 10 I 3 Categories of Muscles 1 Skeletal voluntary control with striations stripes Other names for skeletal striated voluntary 2 Smooth Visceral Involuntary no striations 3 Cardiac makes up walls of the heart II Skeletal Muscle Striations caused by bundles of long slender proteins in a regular rhythm actin fairly THIN bundles myosin THICK bundles THIN and THICK bundles are connected by cross bridges sarcomere repeating unit middle of one filament to another length 2 microns Loaded with mitochondria conversion of ATP to ADP and Energy is released III Muscle Physiology Sarcolemma plasma membrane in a muscle cells Sarcoplasm cytoplasm of muscle cell Sarcoplasmic reticulum endoplasmic reticulum of muscle cell When muscle cell contracts thick and thin bundle size stays the same BUT the ends of the filaments get closer near the ends sliding filament So what happens in all of these parts When a motor neuron s action potential reaches the sarcolemma it then goes down into the T Tubules and the sarcoplasmic reticulum which gets leaky Then it reaches the sarcoplasm From there the action potential causes a release of Ca2 to help make muscles contract and increased Ca2 induces cross bridges and makes filaments slide IV Muscle Cell Contractions Muscles connected to bones by tendons and have a level of plasticity Contraction in which skeletal elements move isotonic contraction with same Force Dimensions stay the same isometric contraction Muscles Are Elastic V VI Length v Tension slowly upward increase until string cannot be stretched anymore Active tension height of peak maximum reach and then will be decreasing Passive tension does not require energy resistant to being stretched property of anything elastic Muscle Types Red muscles do not twitch with as much power resistant to fatigue Red muscle color comes from the red protein myoglobin which has a large concentration of O2 Myoglobin takes up space that can be used for actin and myosin so not as much Energy can be generated White muscles can generate enormous power fatigue quickly Lecture 11 I Muscle Mechanics Skeletal Muscles Tetanic stimulus no relaxation between stimuli Long contractions deliver a tetanic stimulus o motor neurons spread out and innervate more that 1 muscle cell 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 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 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 V VI 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 Lecture 12 I How The Blood Works Mechanical Blood is a fluid Fluids always flow downhill high to low pressure Heart valves only 1 way valves Valves will open when pressure pushing in is greater than pressure pushing back From pulmonary it goes down Left Atrial and down Left Ventricular to systemic From systemic it goes down Right Atrial and down Right Ventricular to pulmonary Systole heart contracting Diastole heart relaxing soon will be 0 mmHg heart fills passively expands where heart is closed in membrane II III IV V at the end heart begins to contract 1st atrial contracts Period of isometric contraction volume stays same only pressure is increased by ventricles Period of ejection blood is being ejected from ventricles End Systolic 50 mL End Diastolic 125 mL Stroke 75 mL Normal Cardiac Output 5 L minute 5 L in left will soon go to 5 L in right How The Blood Works Blood Flow Starling Law of Heart harder you heart ejects in stroke heart entering in diastole Summary cardiac output return Length Tension relationship gives heart the unique property of having input output External Factors that Modify Cardiac Output Parasympathetic decreases heart activity output Sympathetic increases heart activity output Sterling s Law is an INTERNAL factor Autoregulation if you exercise a muscle O2 increases arterials dilate smooth muscle relaxes when O2 increases o blood flows through o Venus return increases so heart pumps extra volume Electrical Properties of the Heart Since the stroke volume difference b w end systole and end diastole the heart gains efficiency if there is a time when every cell simultaneously relaxes or contracts Excitation Fastest contraction S A Node Atrium have simultaneous relaxation contraction will stay that way until 1st cell that generated the action potential goes back to relaxation o cells are in the S A Node Conductive Fibers carry action potentials from atria to ventricles since they cannot directly transfer to each other What happens in atria occurs in ventricles but only timing is different Lecture 13 I Action Potentials Reach from S A