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Muscular System (Types of Body Movement (Hyperextension-Extension beyond…
Muscular System
Types of Body Movement
Hyperextension-Extension beyond 180 degrees
Rotation-Movement of a bone around a longitudinal axis
Extension-Movement that increases angle of joint
Abduction-Movement of limb away from midline
Flexion-Movement that decreases angle of joint
Adduction-Movement of limb toward the midline
Circumduction-Proximal end of a limb is stationary and the distal end moves in circles
Dorsiflexion-Lifting the superior surface of foot towards shin
Plantar flexion-Pointing toe
Inversion-Turn sole of foot medially
Eversion-Turn sole of foot laterally
Supination-Forearm rotates laterally so palm faces anteriorly
Pronation-Forearm rotates laterally so palm of hand faces posteriorly
Opposition-Movement of thumb to touch tips of other fingers
Anatomy of Muscle Fibers
Myofibrils- Made of myofilaments
Thin Myofilaments-Primarilt actin
Thick Myofilaments-Myosin
Myosin-have cross bridges (links thin and thick filaments
Sarcolemma-cell membrane of muscle
Sarco=flesh
Sarcoplasm-cytoplasm of muscle cell
Sarcoplasmic reticulum-specialized smooth endoplasmic reticulum storage and release of calcium when muscle contracts, fuse to form cisternae
Transverse tubules(T-tubules)-infoldings of sarcolemma that penetrate into muscle fiber; filled with extracellular fluid
Myofibril-bundles of myofilaments aligned to give distinct bands
Sarcomere-one contractile unit or section of myofibril, extends from z line to z line
I band= Light band (Thin filament only)
Z line- dark midline of I band
A band= Dark band (thick and thin filaments)
H zone-lighter central area of A band (thick filaments only)
M line- central line of H zone
Neuromuscular Junction
Synaptic cleft-Gap between neuron and sarcolemma
Acetylcholine-Neurotransmitter for skeletal muscle
Neurotransmitter-Chemical messenger sore and release by synaptic vesicles into synaptic cleft
Axonal terminals-Ends of axons, mainly branches
Axon-Long portion of nerve, releases a chemical called neurotransmitter
Synaptic end bulb-Found in axonal terminal(Contains synaptic vesicles)
Synapse-Connection between nerve with muscles and other organs
Motor end plates-Region across synaptic cleft from the synaptic end bulb (On muscle fibers)
Naming of Skeletal Muscle
Location of the muscle: Many muscles are named for bones (Temporalis)
Shape of the muscle: Deltoid (Triangular)
Location of the muscle origin and insertion: Sterno (On the Sternum)
Relative size of the muscle: Maximus (Large)
Action of the muscle: Flexor and extensor (Flexes or extends a bone)
Direction of muscle fibers: Rectus (Straight)
Number of origins: Triceps (Three heads)
Connective Tissue of Muscle
Epimysium-Covers the entire skeletal muscle , three layers come together to form tendons
Tendons-Attach muscle to periosteumof bones
Perimysium-Around a fascicle (bundle of muscle fiber)
Aponeurosis-Broad band of CT which form a flat layer of tendons
Endomysium-Around single myocyte=muscle fiber=muscle cell
Fascia (bandage)-Thin band of fibrous CT under the skin or around organs
Function of Muscle
Motion-Change in body position
Movement-Of substances within the body
Stabilizing-Joints, body posture, regulating organ volume
Thermogenesis-Heat production
Types of Muscular Tissue
Cardiac-Cells are long, cylindrical, branched, has single central nucleus, has striations,forms heart wall, joined to another cells at inter-located disc, Involuntary
Smooth-Spindle-shaped cells with single central nucleus, has no striations, found mainly in hollow walls of organs and eyes (controls size of pupil), involuntary
Skeletal-Cells are long, cylindrical, parallel and multi nucleated, attached by tendons to bones, striated-visible bonding, voluntary-subject to conscious control
Motor Unit
Made of one motor neuron and all muscle fibers
Large-Controls large movements
Small-Control precise movements
Characteristics of Muscle
Irritability-Ability of muscles and nerves to respond to stimulus b producing electrical signals action potentials
Contractility-Ability to shorten when adequate is recived
Motor Neuron
Nerve cell that stimulates skeletal muscle
Muscle Contraction
Nerve impulse reaches synaptic end bulbs and causes synaptic vesicles to fuse with neurolemma and release ACH
Sliding Filament Theory
Nerve impulse or action potential travles down sarcolemma and into T-tubles, causing sarcoplasmic reticulum to release Ca++ into Sarcoplasm
Muscle Relaxation
Ach is broken down by an enzyme called Acetylcholinesterase, Actin potentials are no longer generated so the Ca++ channels in SR close, Resting potential is reached when Na+ returns to its initial position