Muscle & Movement PHSL 3051 2022 - PDF

Muscle & Movement PHSL 3051 Dr. Barnett Muscle Introduction Learning Objectives Class 11: Skeletal Muscle and Excitation Contraction Coupling Derrickson (1st edition: p. 364-381, 2nd edition: p 375- 392) 1. Draw and label a diagram that shows skeletal muscle at...

Muscle & Movement PHSL 3051 Dr. Barnett Muscle Introduction Learning Objectives Class 11: Skeletal Muscle and Excitation Contraction Coupling Derrickson (1st edition: p. 364-381, 2nd edition: p 375- 392) 1. Draw and label a diagram that shows skeletal muscle at all anatomical levels 1. Muscle fascicles 2. Single muscle cells 3. Myofibrils and Sarcomeres. 4. At the sarcomere level your drawing should identify the molecular components that are the basis of its striated appearance. Include two different stages of myofilament overlap. 2. Draw the structure of the neuromuscular junction including important proteins that are found on the pre- and post-synaptic membranes (label these proteins and other structural features). 3. List in sequence the steps involved in neuromuscular transmission for skeletal muscle and point out the location of each step on a diagram of the neuromuscular junction; name the neurotransmitter and describe three ways the neurotransmitter molecules in the synaptic cleft are removed after the nerve stops sending signals. 4. List the steps in excitation-contraction coupling in skeletal muscle, and describe the roles of the sarcolemma, transverse tubules, sarcoplasmic reticulum and the thin and thick filaments. Be certain to include the roles of modulatory proteins such as troponin and tropomyosin and of calcium ions. 5. Diagram the chemical and mechanical steps in the cross-bridge cycle, and explain how the cross- bridge cycle results in shortening of the muscle. 6. Describe Ca2+ accumulation in the sarcoplasmic reticulum mediated by Ca-ATPase. Explain the role that these (Ca2+-ATPase pump proteins) transporters play in muscle function. 7. Name three (3) roles of ATP in skeletal muscle contraction and relaxation. 2 Types of muscle Three exist in the body  Skeletal muscle Striated Voluntary Attached to bone  Cardiac muscle Striated Involuntary Heart  Smooth muscle Not striated Involuntary Hollow organs Figure 11.1 3 Muscle Functions Storing and moving substances within the body.  Smooth Muscle: storage is accomplished by sustained contractions of ring-like bands of smooth muscle called sphincters Prevent outflow of the contents of a hollow organ. Temporary storage of food in the stomach or urine in the urinary bladder Etc. (many other examples throughout the body)  Cardiac muscle contractions of the heart pump blood through the blood vessels of the body. 4 Skeletal Muscle Functions Producing body movements.  Walking and running, localized movements Stabilizing body positions.  Skeletal muscle contractions stabilize joints maintain body positions, such as standing or sitting  Postural muscles contract continuously when you are awake sustained contractions of your neck muscles hold your head upright Generating heat.  As muscle contracts, it produces heat This process is known as thermogenesis. 5 Skeletal Muscle Properties Electrical excitability  A property of both neurons and muscle cells Ability to respond to stimuli by producing action potentials Contractility  Ability of muscle to contract forcefully when adequately stimulated When a muscle contracts, it generates tension, and possibly movement Extensibility  Ability of muscle to stretch without being damaged Elasticity  Ability of a muscle to return to its original length and shape after a contraction or extension 6  Review: Skeletal Muscle Control The Somatic Nervous System Figure 10.9 ACh Somatic motor neuron Effector: Spinal cord skeletal muscle A division of the peripheral nervous system which sends commands to activate skeletal muscles. The motor neuron cell body resides in the grey matter of the spinal cord. The axon exits the spinal cord via the ventral root and travels to the target muscle with no intervening synapses. At the muscle, the neuron terminates as the pre-synaptic terminal of the neuromuscular junction and releases acetylcholine upon the arrival of an action potential. 7  Organization of Skeletal Muscles Figure 11.2 8  Components of a Skeletal Muscle Fiber Term Definition Whole muscle A bundle of muscle fascicles Figure 11.3 Muscle Fascicle A bundle of muscle fibers (cells) Muscle Fiber A muscle cell Myofibril Contractile assembly of proteins in a muscle cell Sarcomere Contracting subunits that make up each myofibril Sarcoplasmic Intracellular storehouse of Reticulum calcium ions Transverse Network of tubular passages Tubules within striated muscle that are an extension of the plasma membrane 9 Structural Relationships in Skeletal Muscles Myofibrils Muscle Fascicles Threadlike striated fibers inside muscle cells Muscle Fibers (cells) Sarcomeres Source of the striations Sarcoplasmic Reticulum Internal organelle Transverse Tubules Extension of the plasmalemma 10  Intracellular muscle structure Figure 11.3d 11  Myofibrils are Constructed of Sarcomeres Figure 11.4 12 Three Important Types of Sarcomeric Muscle Proteins Contractile proteins Structural proteins  Actin: Primary protein of the thin filament  Titin: spring-like connector of  Myosin: Primary protein of the thick the thick filament to the Z-disc filament ATP-driven molecular motor for muscle contraction  Alpha-actinin: primary structural protein of the Z-disc Regulatory proteins  Tropomyosin: blocks myosin binding sites on the thin filament  Myomesin: primary structural during relaxation proteins of the M-line Moves out of the way during muscle contraction 7 actin subunits per tropomyosin  Dystrophin: connects the Z-disc molecule to the membrane cytoskeleton  Troponin: 3 subunit complex on the thin filament Calcium sensor that triggers muscle  Nebulin: “template” for actin contraction filament length Locks Tropomyosin in place when muscle is relaxed 13  Contractile proteins Two  Myosin  Actin Figure 11.5 14  Contractile proteins Two  Myosin  Actin Figure 11.6 15  Regulatory proteins Two  Tropomyosin  Troponin Figure 11.6 16  Structural proteins Contribute to the alignment, stability, extensibility, and elasticity From Figure 11.4 Titin: spring-like connector of the thick filament to the Z-disc Alpha-actinin: primary structural protein of the Z-disc Myomesin: primary structural proteins of the M-line Dystrophin: connects the Z-disc to the membrane cytoskeleton Nebulin: “template” for actin filament length 17