BSC 215- Week 8 Notes
BSC 215- Week 8 Notes BSC 215
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This 6 page Class Notes was uploaded by Alexia Acebo on Sunday March 6, 2016. The Class Notes belongs to BSC 215 at University of Alabama - Tuscaloosa taught by Dr. Jason Pienaar in Summer 2015. Since its upload, it has received 10 views. For similar materials see Human Anatomy & Physiology I in Biological Sciences at University of Alabama - Tuscaloosa.
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Date Created: 03/06/16
BSC 215- Week 8 Notes Lecture 13 -Muscle Tissue I- LO 1. Muscle Tissue 1. Striated skeletal and cardiac 2. Smooth **Fiber and cell interchangeable Cells ECM Skeletal long, Endomysium holds multinucleated and muscle cells together connected to nerves within muscle tissue Cardiac shorter, uni or binucleated, branched, involuntary, connected to each other by gap junctions Smooth short, spindle shaped, uninucleated, connected to each other by gap junctions CHARACTERISTICS: Contractility- ability of protein fibers within myocytes to draw together Excitability- responds to stimuli (electrical/chem.. Conductivity- Conduct stimulus (electrical) Extensibility- can be stretched up to 3x resting length Elasticity- ability to regain original state after stretch Cytoplasm=sarcoplasm Plasma membrant= sarcolemma SER= sarcoplasmic reticulum rearrangement of cytoskeleton: -myofibril (surrounded by sarcoplasmic reticulum) different from myofiber LO 2. Skeletal muscle organization Perimysium: connect cells and endomysium into fasicles, continues as tendon Epimysium: surrounds muscle and continues as tendon LO 3. Structural components of fibers, sarcoplasmic reticulum (stores calcium) and myofibrils To identify: -cell size/shape -striations -multiple nuclei **sarcoplasmic reticulum -neuromuscular junction stimulates sarcolemma sodium ion channels (voltage gated) -tubules -t tubules sarcolemma down into the cell **Myofibrils A band- dark (overlap)… myosin-thick I band- light… actin-thin **Filament proteins -Actin: actin subunits -Myosin -Titin: elastic filament -Tropomyosin: long string -Troponin: “ball” to attach Ca LO 4. How myofilaments are arranged AND mechanism H zone: slightly lighter region w/in A band **I band changes width as contracts, A band DOES NOT in A band: H zone narrows Z disc: establishes sarcomere, everything occurs between 2 z discs Sarcomere=functional contractile unit -Actin filaments slide along myosin toward m line, pulling z discs closer together LO 5. Membrane potential Electrical Gradient: separation of charged particles (electrolyte pairs) across the plasma membrane ( sarcolemma) Electrical potential: potential energy due to barrier (sarcolemma) maintaining gradient Voltage: difference in electrical potential between 2 points Membrane Potential: potential difference between either side of the membrane (polarized) o Resting membrane potential for myocytes=-85 mV **Na/K pumps help sarcolemmas more permeable to K than Na Clicker Quiz Plasma membrane of skeletal muscle o Sarcolemma Which protein=elastic filaments o Titin Skeletal muscle fibers posess intercalated discs o False Skeletal muscle fibers w/ perimysium o fasicle Lecture 14 -Muscle Tissue II- LO 1. Action Potentials Action Potential- quick, local, temporary change in membrane potential Voltage gated channel proteins (Na 3 out, K 2 in) -generated initial resting potential rest passive diffusion (through ion channels) opened by change in voltage 1. Resting phase a. Gated channels are closed, Na & K gradients maintained by pumps and K leak channels 2. Depolarization phase a. Na channels open in response to a depolarizing stimulus b. Na enters the cell down its gradient and further depolarizes the membrane 3. Repolarization phase a. Na channels close b. K channels open, K exits the cell down its gradient and repolarizes the membrane 4. Na/K pump restores resting potential **Ligand gates channels where neuron interacts with muscle neuromuscular junction to t tubule LO 2. Neuromuscular junction Motor neurons o Stimulate skeletal muscle to contract ** All skeletal muscle fibers are innervated Axon branches of motor neuron synapse with muscle fibers at neuromuscular junctions Synaptic vesicles at end of axons contain acetylcholine, a neurotransmitter Acetylcholine is secreted into the synaptic cleft and interacts with acetylcholine receptors on the motor end plate of the sarcolemma 1. AP propagated through nurilemma 2. Chem. Signal at synapse 3. AP propagated through sarcolemma LO 3. Excitation/ Contraction 1. AP from neuron acetylcholine secretion in synaptic cleft 2. Ligand gated Na channels in sarcolemma open 3. Generated AP wave that travels down t tubules of sarcolemma 4. T tubule depolarization results in Ca channels in the terminal cisternae of sarcoplasmic reticulum to open 5. Ca interacts with troponin, release tropomyosin and allows myosin heads to interact with actin sarcomere contraction 6. Muscle relaxes when Acetylcholine no longer present Ca in sarcoplasm returns to normal AP down t tubules T tubule depolarization= open voltage gated Ca channels **at rest, tropomyosin twists around actin, blocking active sites **Ca binds to troponin causing tropomyosin to fall off the actin, exposing the active sites CONTRACTION phase: the crossbridge cycle 1. ATP hydrolysis “cocks” the myosin head 2. Myosin heads bind to actin active sites 3. Myosin releases ADP and Pi, overstroke pulls actin toward m line 4. Binding of a new ATP “breaks crossbridge 5. Cycle restarts Muscle Relaxation 1. Acetylcholinesterase: degrades acetylcholine in synaptic cleft 2. Sarcolemma returns to resting potential and Ca channels in sarcoplasmic reticulum close 3. Ca pumps LO 5. Energy Muscle fibers require a lot of ATP o Na/K pumps o Cross bridge cycle Where do they get it from? o Source Immediate Anaerobic glucose catabolism Aerobic glucose catabolism
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