Chp 12 Part A.pdf

Physiology: Chp 12 Part A Autonomic & Somatic Motor Control Juan J. Bustamante, Ph.D. Assistant Professor Pharmaceutical Science Phone (361) 221-0643 Email: [email protected] Office: Room 223 © 2016 Pearson...

Physiology: Chp 12 Part A Autonomic & Somatic Motor Control Juan J. Bustamante, Ph.D. Assistant Professor Pharmaceutical Science Phone (361) 221-0643 Email: [email protected] Office: Room 223 © 2016 Pearson Education, Inc. © 2016 Pearson Education, Inc.  The somatic motor division Mostly voluntary © 2016 Pearson Education, Inc.  Figure 11.9-2 Efferent Divisions of the Nervous System Somatic pathways are always excitatory, unlike autonomic pathways, which may be either excitatory or inhibitory. Single neuron CNS origin: Cell body located either in the ventral horn of the spinal or in the brain. Myelinated Terminus Branches SOMATIC MOTOR PATHWAY ACh Nicotinic receptor CNS Target: skeletal muscle always excitatory - no antagonistic innervation to relax skeletal muscles-instead relaxation occurs when the somatic motor neurons are inhibited in the CNS © 2016 Pearson Education, Inc. Figure 11.10a Somatic Motor Neurons and the Neuromuscular Junction © 2016 Pearson Education, Inc. Figure 11.10c Somatic Motor Neurons and the Neuromuscular Junction Neuromuscular junction Synaptic vesicle (ACh) Presynaptic membrane Synaptic cleft Nicotinic ACh receptors Postsynaptic membrane of skeletal muscle fiber Is modified into a motor end plate. © 2016 Pearson Education, Inc. Figure 12.11 Timing of E-C coupling Action potentials in the axon terminal (top graph) Motor Neuron Action Potential and in the muscle fiber (middle graph) are followed by a muscle twitch (bottom graph). +30 Muscle fiber Neuron membrane Action potential potential from CNS in mV −70 Time Motor Recording end plate electrodes Axon Muscle Fiber Action Potential terminal +20 Muscle fiber Muscle action membrane potential potential in mV −80 2 msec Time NAVIGATOR Neuro- muscular Development of Tension during One Muscle Twitch junction (NMJ) Latent Contraction Relaxation E-C period phase phase coupling Tension FIGURE QUESTIONS Movement of what ion(s) in what direction(s) creates Muscle (a) the neuronal action potential? 10–100 msec twitch (b) the muscle action potential? Time © 2016 Pearson Education, Inc. Figure 11.10d Somatic Motor Neurons and the Neuromuscular Junction An action potential arrives at the axon terminal, causing voltage-gated Ca2+ channels to open. Calcium entry causes synaptic vesicles to fuse with the presynaptic membrane and release ACh into the synaptic cleft. Presynaptic membrane Synaptic vesicle (ACh) Synaptic cleft Ca2+ Ca2+ ACh Acetyl + choline Postsynaptic Voltage-gated membrane is Ca2+ channel modified into a motor end plate. AChE Nicotinic Skeletal muscle receptor fiber Acetylcholine (ACh) is metabolized by acetylcholinesterase (AChE). © 2016 Pearson Education, Inc. Figure 11.10e Somatic Motor Neurons and the Neuromuscular Junction The nicotinic cholinergic receptor binds two ACh molecules, opening a nonspecific monovalent cation channel. The open channel allows Na+ and K+ to pass. Net Na+ influx depolarizes the muscle fiber. action potential that causes muscle contraction of the skeletal muscle K+ Na+ ACh K+ Na+ Closed channel Open channel © 2016 Pearson Education, Inc. Interesting facts: The nAChR channels of the skeletal muscle are similar by not identical to the nicotinic Ach receptors found on the neurons. This difference is illustrated by the fact that the snake toxin α- bungarotoxin binds to nicotinic skeletal muscle receptors but not to those of the autonomic ganglia. © 2016 Pearson Education, Inc.  Slide 3 Initiation of Muscle Action Potential Axon terminal of KEY somatic motor neuron DHP = dihydropyridine L-type calcium channel RyR = ryanodine receptor-channel Muscle fiber ACh - - - - - ++ + - + Somatic motor neuron releases - + Na+ ACh at neuromuscular junction. - + - + - + Motor end plate + - RyR Net entry of Na+ through ACh + - receptor-channel initiates a T-tubule + - muscle action potential. + Ca2+ Sarcoplasmic reticulum Z disk + - + - DHP Troponin Actin Tropomyosin M line Myosin head Myosin thick filament Calcium release from the sarcoplasmic reticulum is mediated by two membrane proteins. L-type calcium channel dihydropyridine (DHP) receptor and ryanodine receptors (RyR) © 2016 Pearson Education, Inc. Figure 12.11 Timing of E-C coupling Action potentials in the axon terminal (top graph) Motor Neuron Action Potential and in the muscle fiber (middle graph) are followed by a muscle twitch (bottom graph). +30 Muscle fiber Neuron membrane Action potential potential from CNS in mV −70 Time Motor Recording end plate electrodes Axon Muscle Fiber Action Potential terminal +20 Muscle fiber Muscle action membrane potential potential in mV −80 2 msec Time NAVIGATOR Neuro- muscular Development of Tension during One Muscle Twitch junction (NMJ) Latent Contraction Relaxation E-C period phase phase coupling Tension FIGURE QUESTIONS Movement of what ion(s) in what direction(s) creates Muscle (a) the neuronal action potential? 10–100 msec twitch (b) the muscle action potential? Time © 2016 Pearson Education, Inc.  Slide 4 Calcium release from the sarcoplasmic reticulum is mediated KEY by two membrane proteins. DHP = dihydropyridine L-type 1. L-type calcium channel dihydropyridine (DHP) receptor calcium channel 2. Ryanodine receptors (RyR) RyR = ryanodine receptor-channel Action potential in t-tubule Excitation-Contraction Coupling alters conformation of DHP receptor. - + - + - + DHP receptor opens RyR Ca2+ T-tubule - + release channels in sarco- × Sarcoplasmic plasmic reticulum, and Ca2+ - + reticulum enters cytoplasm. + - + + - - - Ca2+ released. Actin Ca2+ binds to troponin, allowing actin-myosin binding. A latent period is the short delay between the muscle action potential and beginning of muscle tension development. Time required for calcium release and binding to troponin © 2016 Pearson Education, Inc.  Slide 6 KEY DHP = dihydropyridine L-type calcium channel RyR = ryanodine receptor-channel Action potential in t-tubule Excitation-Contraction Coupling alters conformation of DHP receptor. - + - + - + DHP receptor opens RyR Ca2+ - + T-tubule release channels in sarco- Sarcoplasmic × plasmic reticulum, and Ca2+ reticulum enters cytoplasm. - + + - + + - - - Ca2+ released. Actin Ca2+ binds to troponin, allowing actin-myosin binding. Myosin thick filament Myosin heads execute power stroke. Distance actin moves Actin filament slides toward center of sarcomere. © 2016 Pearson Education, Inc. Figure 12.10c Excitation-Contraction Coupling and Relaxation Slide 2 Relaxation Phase KEY DHP = dihydropyridine L-type calcium channel RyR = ryanodine receptor-channel Relaxation Phase + - + - Sarcoplasmic Ca2+-ATPase + - pumps Ca2+ back into SR. T-tubule + - Sarcoplasmic × reticulum + - ATP + ++ - - - - Ca2+ © 2016 Pearson Education, Inc. Figure 12.10c Excitation-Contraction Coupling and Relaxation Slide 3 Relaxation Phase KEY DHP = dihydropyridine L-type calcium channel RyR = ryanodine receptor-channel Relaxation Phase + - + - Sarcoplasmic Ca2+-ATPase + - pumps Ca2+ back into SR. T-tubule + - Sarcoplasmic × reticulum + - ATP Decrease in free cytosolic + ++ - [Ca2+] causes Ca2+ to unbind - - - Ca2+ releases. Ca2+ from troponin. Actin © 2016 Pearson Education, Inc. Figure 12.10c Excitation-Contraction Coupling and Relaxation Slide 4 Relaxation Phase KEY DHP = dihydropyridine L-type calcium channel RyR = ryanodine receptor-channel Relaxation Phase + - + - Sarcoplasmic Ca2+-ATPase + - pumps Ca2+ back into SR. T-tubule + - Sarcoplasmic × reticulum + - ATP Decrease in free cytosolic + ++ - [Ca2+] causes Ca2+ to unbind - - - Ca2+ releases. Ca2+ from troponin. Actin Tropomyosin re-covers binding site. When myosin heads release, Myosin thick filament elastic elements pull filaments back to their relaxed position. Distance actin moves A muscle twitch is a single contraction-relaxation cycle © 2016 Pearson Education, Inc.  Three Metabolic Pathways to Obtain Energy © 2016 Pearson Education, Inc.  Three Metabolic Pathways to Obtain Energy © 2016 Pearson Education, Inc.  Three Metabolic Pathways to Obtain Energy © 2016 Pearson Education, Inc.  Three Metabolic Pathways to Obtain Energy © 2016 Pearson Education, Inc. Phosphocreatine Anaerobic glycolysis Aerobic respiration breakdown: short produces lactate and (citric acid cycle and burst of energy acid: quick, no oxygen electron transport required, small amount chain): slow, requires of energy released oxygen, large amount of energy released © 2016 Pearson Education, Inc. Chapter 12 Muscles Figure 12.1 The three types of muscles Skeletal muscle fibers are large, multinucleate cells that appear Nucleus striped or striated under the microscope. Muscle fiber (cell) Striations Nucleus Cardiac muscle fibers are also striated but they are smaller, Muscle fiber branched, and uninucleate. Cells are joined in series by junctions called intercalated disks. Intercalated disk Striations Smooth muscle fibers are small and lack striations. Nucleus Muscle fiber © 2016 Pearson Education, Inc. Figure 12.24 Duration of muscle twitch in the three types of muscle © 2016 Pearson Education, Inc.