neuromuscular junc lecture

neuromuscular junc lecture - Neuromuscular Junction Lecture...

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Neuromuscular Junction Lecture Notes These notes supplement the lectures and cover background material that will help place the experiments in context. © University of Minnesota Version: July, 2008
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Table of Contents 1 Muscle Contraction: cardiac, smooth and skeletal ________________________ 3 2 The Neuromuscular Junction ________________________________________ 13 3 Membrane Resting Potential _________________________________________ 21 4 NMJ References___________________________________________________ 29 5 Readings _________________________________________________________ 31 NMJ Lecture Notes 1
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1 Muscle Contraction: cardiac, smooth and skeletal 1. Types On the basis of structure, contractile properties and control mechanisms, three types of muscle can be identified: 1) skeletal muscle, 2) smooth muscle and 3) cardiac muscle. Although there are significant differences between these muscle types, the force- generating mechanisms are similar. Skeletal Muscle: most skeletal muscle is attached to bone and its contraction is responsible for supporting and moving the skeleton. The contraction of these muscles is initiated by action potential propagating down motoneurons to the muscle and can be under voluntary control. Smooth Muscle: sheets of smooth muscle surround various hollow organs and tubes (e.g., stomach, intestines, urinary bladder, uterus, blood vessels and airways). Contraction of these cells may propel the luminal contents through the organ or regulate internal flows by changing tube diameters. Single and groups of smooth muscle cells are also found distributed throughout organs and perform various other functions: e.g., iris of the eye and attachment of hair. Smooth muscle contraction can be spontaneous or controlled by: the autonomic nervous system, hormones and other chemical signals. Cardiac Muscle: The muscle of the heart surrounds four pumping NMJ Lecture Notes 3
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chambers. Contraction of cardiac muscle provides the impetus for the movement of blood through the pulmonary and systemic circulatory systems. Spontaneous cycling of an intrinsic pacemaker triggers each heartbeat (or contraction). However the autonomic nervous system and circulating hormones modulate the frequency of this activation. 2. Structure and Function of Skeletal Muscle If one sections through a skeletal muscle, one can observed that it is organized into bundles of fibers call fascicles. The individual muscle fibers, multinucleated cells, contain long slender structures called myofibrils. These are made of myofilaments, which are organized into sarcomeres, the functional unit of contractions. Both skeletal and cardiac muscle have a striated appearance under a light microscope, due to the organization of the myofilaments. Each myofibril is composed of thick and thin filaments arranged in a repeating pattern
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neuromuscular junc lecture - Neuromuscular Junction Lecture...

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