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exam 2 notes - Part 2 Physiology 206 Notes Muscle 3 Major...

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Part 2 Physiology 206 Notes Muscle - 3 Major categories: 1.) Skeletal - Voluntary- Striated Muscle 2.) Smooth - Involuntary- Visceral 3.) Cardiac - Heart Muscle - All Muscles contact. - Muscle is a mechanical device. Requires energy. Real device; efficiency is NOT perfect; doing work generates heat. Examples: Shivering when cold. & Exercise rises body temperature. Skeletal Muscle - Known since mid-19 th Century that it has striations. - Striations are made from the arrangement of proteins. Vocabulary - Cell Membrane = Sarcolemma - Endoplasmic Reticulum = Sacrcoplasmic Reticulum - Muscle Cell = Muscle Fiber Within it are Myofibrils - Visible manisfestations of proteins. Proteins 1.) Actin - Thinner- known as thin filaments 2.) Myosin - Thicker- known as thick filaments. ** In muscle of Bundles ** -- Overlap one another. -- They are attached to one another. ** Gives rigidity - makes hard to pull apart.** - When Muscle fiber contracts, the thick and thin filaments stay the same size, they just get closer to one another.- Known as Sliding- Filament Mechanism . Energy source is ADP. Provides energy for contraction. Gets energy from mitochondria;* Muscle cells have lots of Mitochondria.* Two things Muscle can do 1.) Isometric Contraction - Can generate force without shortening. 2.) Isotonic Contraction - Can shorten without generating force. (At same tension) Rarely do any happen in pure form. Mostly approximation. Example: Piano player starts with isometric, then turns to isotonic. Isometric Contraction -Force low, Velocity High. -Force high, Velocity Low. Physical Definition of Work - Move Force through a distance. By definition, Isometric does no work. Power - Rate at which you do work.
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By definition, Isometric doesn’t generate power. ** Maximum Ability to do work at high rate- 1/3 of 0 velocity and max velocity. ** Muscle --- If you stimulate again, before muscle is relaxed, it can stay contracted; this is called Tetany . --- Sensation that leads to it is called Tetanic Stimulation Average - 50-55 Stimulations per second --- Electric current in US-60 stimuli per sec.(cycle current) --- Most of the rest of the world-50 stimuli per sec. Reason US does this-Historical Meaning-it was believed that anything less than 60 cycles, would flicker. Truth is that you can see no flickering with cycles all the way to around 40 cycles. Twitch - either it contracts or it doesn’t- NO halfway! Neural Control - Helps to make fine movements; Brain sends out instructions to how many Motor Units to Send out. Motor Unit = 1 Motor Neuron & all the muscle cells it stimulates - 1 Motor Unit innervates more than one cell - Motor Nerves that make fingers work have small motor units - In thigh, the motor units include several hundred cells-generate great power. ** Reason we play piano with fingers, not heels! ** Smooth Muscle --- Differences between striated: 1.) Doesn’t have striations Actin & Myosin present, but elements are not lined up in registered order, so do not see the visible manifestations of striations.
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