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Sarcoplasmic Reticulum: A network of tubules and sacs in the cytoplasm of Skeletal muscle fibers that assist with muscle contraction and relaxation by releasing and storing calcium ions.

Endoplasmic Reticulum

JoVE 10969

The Endoplasmic Reticulum (ER) in eukaryotic cells is a substantial network of interconnected membranes with diverse functions, from calcium storage to biomolecule synthesis. A primary component of the endomembrane system, the ER manufactures phospholipids critical for membrane function throughout the cell. Additionally, the two distinct regions of the ER specialize in the manufacture of specific lipids and proteins. The rough ER is characterized by the presence of microscopically-visible ribosomes on its surface. As a ribosome begins translation of an mRNA in the cytosol, the presence of a signal sequence directs the ribosome to the surface of the rough ER. A receptor in the membrane of the ER recognizes this sequence and facilitates the entry of the growing polypeptide into the ER lumen through a transmembrane protein complex. With the assistance of chaperones, nascent proteins fold and undergo other functional modifications, including glycosylation, disulfide bond formation, and oligomerization. Properly folded and modified proteins are then packaged into vesicles to be shipped to the Golgi apparatus and other locations in the cell. Chaperones identify improperly folded proteins and facilitate degradation in the cytosol by proteasomes. Lacking ribosomes, the smooth ER is the cellular location of lipid and steroid synthesis, cellular detoxification, ca

 Core: Cell Structure and Function

Cross-bridge Cycle

JoVE 10870

As muscle contracts, the overlap between the thin and thick filaments increases, decreasing the length of the sarcomere—the contractile unit of the muscle—using energy in the form of ATP. At the molecular level, this is a cyclic, multistep process that involves binding and hydrolysis of ATP, and movement of actin by myosin.

When ATP, that is attached to the myosin head, is hydrolyzed to ADP, myosin moves into a high energy state bound to actin, creating a cross-bridge. When ADP is released, the myosin head moves to a low energy state, moving actin toward the center of the sarcomere. Binding of a new ATP molecule dissociates myosin from actin. When this ATP is hydrolyzed, the myosin head will bind to actin, this time on a portion of actin closer to the end of the sarcomere. Regulatory proteins troponin and tropomyosin, along with calcium, work together to control the myosin-actin interaction. When troponin binds to calcium, tropomyosin is moved away from the myosin-binding site on actin, allowing myosin and actin to interact and muscle contraction to occur. As a regulator of muscle contraction, calcium concentration is very closely controlled in muscle fibers. Muscle fibers are in close contact with motor neurons. Action potentials in motor neurons cause the release of the neurotransmitter acetylcholine in the vicinity of muscle fibers. This ge

 Core: Musculoskeletal System

Muscle Contraction

JoVE 10869

In skeletal muscles, acetylcholine is released by nerve terminals at the motor end plate-the point of synaptic communication between motor neurons and muscle fibers. Binding of acetylcholine to its receptors on the sarcolemma allows entry of sodium ions into the cell and triggers an action potential in the muscle cell. Thus, electrical signals from the brain are transmitted to the muscle. Subsequently, the enzyme acetylcholinesterase breaks down acetylcholine to prevent excessive muscle stimulation. Individuals with the disorder myasthenia gravis, develop antibodies against the acetylcholine receptor. This prevents transmission of electrical signals between the motor neuron and muscle fiber and impairs skeletal muscle contraction. Myasthenia gravis is treated using drugs that inhibit acetylcholinesterase (allowing more opportunities for the neurotransmitter to stimulate the remaining receptors) or suppress the immune system (preventing the formation of antibodies). Unlike skeletal muscles, smooth muscles present in the walls of internal organs are innervated by the autonomic nervous system and undergo involuntary contractions. Contraction is mediated by the interaction between two filament proteins-actin and myosin. The interaction of actin and myosin is closely linked to intracellular calcium concentration. In response to neurotransmitter or hormone sig

 Core: Musculoskeletal System

Creating a Structurally Realistic Finite Element Geometric Model of a Cardiomyocyte to Study the Role of Cellular Architecture in Cardiomyocyte Systems Biology

1Cell Structure and Mechanobiology Group, University of Melbourne, 2Systems Biology Laboratory, Melbourne School of Engineering, University of Melbourne, 3Department of Biomedical Engineering, University of Melbourne, 4School of Mathematics and Statistics, Faculty of Science, University of Melbourne, 5Department of Engineering Science, University of Auckland, 6Advanced Microscopy Facility, Bio21 Molecular Science and Biotechnology Institute, University of Melbourne, 7ARC Centre of Excellence in Convergent Bio-Nano Science and Technology, University of Melbourne, 8School of Medicine, Faculty of Medicine, Dentistry and Health Sciences, University of Melbourne, 9Living Systems Institute, University of Exeter

JoVE 56817

 Bioengineering

Contractility Measurements of Human Uterine Smooth Muscle to Aid Drug Development

1Harris-Wellbeing Preterm Birth Research Centre, Department of Cellular and Molecular Physiology, Institute of Translational Medicine, University of Liverpool, 2School of Biomedical Sciences, The University of Queensland, 3Faculty of Chemistry, Institute of Biological Chemistry, University of Vienna, 4Institute for Molecular Bioscience, University of Queensland, 5Center for Physiology and Pharmacology, Medical University of Vienna

JoVE 56639

 Medicine

High-Throughput Analysis of Optical Mapping Data Using ElectroMap

1Institute of Cardiovascular Sciences, University of Birmingham, 2EPSRC Centre for Doctoral Training in Physical Sciences for Health, School of Chemistry, University of Birmingham, 3School of Computer Science, University of Birmingham, 4Institute of Clinical Sciences, University of Birmingham, 5Institute of Microbiology and Infection, School of Biosciences, University of Birmingham

JoVE 59663

 Medicine

Simultaneous Electrical and Mechanical Stimulation to Enhance Cells' Cardiomyogenic Potential

1Insuficiencia Cardiaca y Regeneración Cardiaca (ICREC) Research Program, Health Science Research Institute Germans Trias i Pujol, 2Amsterdam Universitair Medisch Centrum (UMC), Vrije Universiteit Amsterdam, Pulmonology and Physiology, Amsterdam Cardiovascular Sciences, 3Electronic and Biomedical Instrumentation Group, Departament d'Enginyeria Electrònica, Universitat Politècnica de Catalunya, 4Cardiology Service, Germans Trias i Pujol University Hospital, 5Department of Medicine, Universitat Autònoma de Barcelona, 6Centro de Investigación Biomédica en Red (CIBER) Cardiovascular, Instituto de Salud Carlos III

JoVE 58934

 Bioengineering

Crystal Structure of the N-terminal Domain of Ryanodine Receptor from Plutella xylostella

1Tianjin Key Laboratory for Modern Drug Delivery & High-Efficiency, Collaborative Innovation Center of Chemical Science and Engineering, School of Pharmaceutical Science and Technology, Tianjin University, 2State Key Laboratory of Ecological Pest Control for Fujian/Taiwan Crops and Institute of Applied Ecology, Fujian Agriculture and Forestry University, 3Joint International Research Laboratory of Ecological Pest Control, Ministry of Education, Fuzhou, 4Fujian-Taiwan Joint Centre for Ecological Control of Crop Pests, Fujian Agriculture and Forestry University

JoVE 58568

 Biochemistry

Preparation of Acute Myocardial Tissue Slices from Biopsies of Human Neonates and Infants with Congenital Heart Disease for Physiological Measurements

1Department of Pediatric Cardiology, University Hospital of Cologne, 2Institute for Neurophysiology, University of Cologne, 3Department of Cardio-thoracic Surgery, University Hospital of Cologne, 4Department of General Pediatrics, Neonatology and Pediatric Cardiology, University Children's Hospital, Heinrich Heine University, 5Children's Hospital for Wales, University Hospital of Wales

Video Coming Soon

JoVE 55566

 JoVE In-Press

Local Field Fluorescence Microscopy: Imaging Cellular Signals in Intact Hearts

1School of Natural Sciences, University of California, Merced, 2Centro de Investigaciones Cardiovasculares, Universidad de la Plata and Conicet, 3Facultad de Ingenieria, Universidad Nacional de Entre Rios, 4Department of Physiology, Midwestern University, 5School of Engineering, University of California, Merced

JoVE 55202

 Biology

Isolation and Cryopreservation of Neonatal Rat Cardiomyocytes

1Department of Molecular Biomedical Sciences and Center for Comparative Medicine and Translational Research, College of Veterinary Medicine, North Carolina State University, 2Joint Department of Biomedical Engineering, University of North Carolina at Chapel Hill, North Carolina State University, 3The Cyrus Tang Hematology Center, Soochow University

JoVE 52726

 Developmental Biology

Assessment of Calcium Sparks in Intact Skeletal Muscle Fibers

1Department of Surgery, Davis Heart and Lung Research Institute, The Ohio State University Wexner Medical Center, 2Department of Physiology and Cell Biology, Davis Heart and Lung Research Institute, The Ohio State University Wexner Medical Center, 3Department of Molecular Biophysics and Physiology, Rush University Medical Center, 4Department of Internal Medicine, Davis Heart and Lung Research Institute, The Ohio State University Wexner Medical Center

JoVE 50898

 Biology

Optocardiography and Electrophysiology Studies of Ex Vivo Langendorff-perfused Hearts

1Sheikh Zayed Institute for Pediatric and Surgical Innovation, Children's National Hospital, 2Children's National Heart Institute, Children's National Hospital, 3Center for Neuroscience Research, Children's National Hospital, 4Department of Biomedical Engineering, School of Engineering, University of Alabama at Birmingham, 5Department of Pediatrics, Department of Pharmacology & Physiology, School of Medicine and Health Sciences, George Washington University

Video Coming Soon

JoVE 60472

 JoVE In-Press

Preparation and Utilization of Freshly Isolated Human Detrusor Smooth Muscle Cells for Characterization of 9-Phenanthrol-Sensitive Cation Currents

1Department of Pharmaceutical Sciences, College of Pharmacy, University of Tennessee Health Science Center, 2Department of Urology, Medical University of South Carolina, 3Department of Urology, College of Medicine, University of Tennessee Health Science Center, 4Department of Pharmacology, College of Medicine, University of Tennessee Health Science Center

Video Coming Soon

JoVE 59884

 JoVE In-Press
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