The Muscular System: Yatziri Carmona Per.1
Attachments
Connective Tissue Sheaths
The Types of Muscle Tissue
Skeletal: striated, voluntary
Cardiac: striated, involuntary
Smooth: visceral, non striated, involuntary
Muscle Functions
Characteristics of Muscle Tissue
elasticity: ability of a muscle cell to recoil and resume
Extensibility: ability to stretch or extend
Contractility: ability to shorten forcibly
Excitability: responsiveness
Maintain posture
Produce movement
Generate heat
Stabilize joints
Perimysium and fascicles: "around the muscle", layer of dense irregular connective tissue
Endomysium: "within the muscle", fine areolar connective tissue
Epimysium : "outside the muscle", dense irregular connective tissue"
direct/ fleshy attachments: epimysium of the muscle is fused to the periosteum of a bone or perichondrium of a cartilage
indirect attachments: the muscles connective tissue wrappings extend beyond the muscle as either a rope like tendon or as a sheet like aponeurosis.
Sliding Filament Theory:the myosin (thick) filaments of muscle fibers slide past the actin (thin) filaments during muscle contraction, while the two groups of filaments remain at relatively constant length.
The sarcoplasmic reticulum stimulated to release calcium ions
cross bridges detach from binding sites on actin
muscle fiber lengthens and relaxes
calcium ions bind to troponin
-causes troponin to drag tropomyosin off cross bridge binding sites
-cross bridges bind to actin
cross bridges on myosin pull on actin (power stroke)
-actin filaments slide to middle of sarcomere
-muscle shortens and contracts
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Neuromuscular junction
Clinical terms
Neuromuscular junction is the site where a motor neuron excites a skeletal muscle fiber
The junction is a chemical synapse consisting of the points of contact between the axon terminals of a motor neuron and the motor end plate of the skeletal muscle fiber
Nerve impulses are also known as action potentials, travel from the brain or spinal cord to trigger the contraction of the skeletal muscles
an action potential travels the length of an axon of a motor neuron to an axon terminal
voltage gated calcium channels open and calcium ions diffuse into the terminal
Calcium entry causes synaptic vesicles to release acetylcholine via exocytosis
Acetylcholine diffuses across the synaptic cleft and binds to acetylcholine receptors which contain ligand gated channels
the ligand gated cation channels open
How are skeletal muscles named?
sodium ions, enter the muscle fiber while potassium ions exit the muscle fiber. This outward flux on K+ causes the membrane to become less negative
once the membrane reaches a threshold, an AP can propagate along the sarcolemma
muscle size
muscle shape
muscle location
direction of muscle fibers
number of origins
location of attachments
muscle action
Fascicle arrangements help determine muscle shape and force
parallel
mulipennate
fusiform
bipennate
convergent
unipennate
circular
Muscles acting with bones to form lever systems
2nd class lever- In second class levers the load is between the effort (force) and the fulcrum.
3rd class levers-With third class levers the effort is between the load and the fulcrum
1st class lever- First class levers have the fulcrum between the force and the load
Effort farther than load from fulcrum= lever operates at a mechanical disadvantage
Effort farther than load from fulcrum= lever operates at a mechanical advantage
myalgia: muscle pain from muscle disorder
myopathy: any disease of the muscle
hernia: protrusion of an organ through its body cavity
myotonic distrophy: a form of muscular dystrophy, gradual reduction in muscle mass
fibromyalgia: a group of conditions involving chronic muscle pain
RICE- rest, ice, compression, elevation (standard treatment of a pulled muscle)
tennis elbow- tenderness due to the overuse of the tendon of the origin of the forearm extensor muscles at the lateral epicondyle of the humerus
Charley horse: painful muscle spasm
torticollis: a condition in which the neck stays rotated to one side, results from problems with sternocleidomastoid
shin splits: medial tibial stress syndrome