BIOL 5600 Notes 2-1-16
BIOL 5600 Notes 2-1-16 BIOL 5600
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This 2 page Class Notes was uploaded by LaurenC on Wednesday February 17, 2016. The Class Notes belongs to BIOL 5600 at Auburn University taught by Dr. Mendonća in Winter 2016. Since its upload, it has received 32 views. For similar materials see Biomedical physiology in Biology at Auburn University.
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Date Created: 02/17/16
BIOL 5600 2-1-16 Recap o Skeletal muscle -Bundles -Connective tissue component >All the way to the sub cellular level *Myofibrils *Filaments all help maintain the arrangement *The sarcomere is the functional unit -Be aware of the A and I bands and their relation to contraction/relaxation Remember the relative concentration of ions in and out of cells -There is a relative negative charge inside the cell (resting membrane potential) and a relative positive charge outside the cell Passive channels -Excitable -CR channels -VR channels When the muscle goes from resting potential to excited, it causes the initiation of an action potential Stimulation from 1 axon terminal/ skeletal muscle cell 1 neuron innervating a skeletal muscle fiber (motor neuron because it’s connected muscle, and muscle is an effector) -Each skeletal muscle fiber has an axon terminal going to it 1 neuron innervating multiple muscle cells (varying number) -This set up called a motor unit -Action potential goes to all cells causing them all to contract -Larger motor unit increases tension in levels that you can create Motor end plate -Specialized part of cell membrane called sarcolemma in muscle cell -You find CR Na_ channels (directly attached) -There are receptors directly on the channels -Receptors for neurotransmitter acetylcholine (Ach) The whole setup is called the neuromuscular junction (equivalent to the synapse) -There is a space between axonal terminals -Ach must diffuse across space and bind to receptors -Lots of Ach is needed to make it across -Binding of Ach causes CR channels to open and allow Na+ to enter cell Action potential causes a wave of depolarization -Causes VR Ca2+ channels to open, Ca+2 goes in and Na+ follows and depolarizes -Sarcolemma makes long indentions into cell called t-tubule -Sarcoplasmic reticulum (endoplasmic reticulum) -Extends bag-like formation called terminal cisternae >Terminal cisternae is Ca2+ storage -Intracellular Ca2+ levels are low -Along the sarcolemma are CR Na+ and K+ channels -The rest of the sarcolemma is VR channels -Enough Na+ comes in, creates depolarization, creates action potential -Action potential causes negative charge to become positive, Ca+2 release from “bags”, then an increase in Ca+2 levels inside the cell Process of Excitation -Purpose is to increase intracellular Ca+2 levels 1) A wave of depolarization comes down axonal terminal -Because the terminal has CR NA+ and K+ channels, you have a spread of + charge -Change from negative to positive (wave of depolarization) opens VR Ca2+ channels to open *In skeletal muscle neuromuscular junction is Ach 2) Increased Ca+2 initiates exocytosis of Ach into the neuromuscular junction 3) Ach binds to Ach receptor associated with CR Na+ channels, opens Na+ channels 4) Negative charge to positive charge -Na+ enters and depolarized all to initiate action potential opening /closing the Na+ /K+ channels 5) Action potential causes VR Ca+2 to open -20% Ca2+ comes from sarcolemma -80% Ca2+ comes from terminal cisternae
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