Skeletal Muscle Functions 1. Movement - contract (get shorter) bones function as levers 2. Heat...
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Transcript of Skeletal Muscle Functions 1. Movement - contract (get shorter) bones function as levers 2. Heat...
![Page 1: Skeletal Muscle Functions 1. Movement - contract (get shorter) bones function as levers 2. Heat production through catabolism ( homeostasis) 3. Posture.](https://reader030.fdocuments.in/reader030/viewer/2022032722/56649f435503460f94c62de7/html5/thumbnails/1.jpg)
Skeletal Muscle
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Functions• 1. Movement - contract (get shorter) bones
function as levers
• 2. Heat production through catabolism ( homeostasis)
• 3. Posture - muscle tone (constant, slight flexing of muscles)
• 4. Joint stabilization
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Macroscopic Structure• 1. Belly = main part of
the muscle
• 2. Origin = attachment to the nonmoving bone
• 3. Insertion = attachment to the moving bone
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Skeletal Muscle Organs• 1. Components - Study drawings
(pp. 282, 283, 285) know for quiz!!!– a. Epimysium (deep fascia) -
fibrous connective tissue sheath around each muscle.Extends past muscle as:• 1) Tendon - connects muscle
to bone• 2) Aponeurosis - connects
muscle to muscle as a flattened connective tissue sheet
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Skeletal Muscle Organs (continued)
• b. Perimysium - connective tissue around bundles of deep fascia fibers (cells)
1) Fasicle = bundle of muscle cells
2) Myofiber = muscle cell
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Skeletal Muscle Organs (continued)
• c. Endomysium - around each muscle fiber (cell)
1. Myofibril - bundle of muscle proteins
2. Myofilament - muscle protein (actin (thin) or myosin (thick))
3. Sarcomere the unit of contraction, from Z disc to Z disc
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Skeletal Muscle Organs (continued)
• 2. Nerve Supply– a. Somatic motor neuron
= nerve cell that tells a skeletal muscle to contract.
– b. Motor unit = one neuron and all of the muscle cells it goes to.
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Skeletal Muscle Organs (continued)
• c. Motor end-plate or neuromuscular junction = where neuron and myofiber meet at synaptic cleft (which is the space between them)
• d. Acetylcholine (Ach) = neurotransmitter (chemical) that initiates contraction. Broken down by acetylcholinesterase (Ach-ase) enzyme.
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Muscle• 1. Contracts only when stimulated
by a motor neuron.• 2. Types of contraction:
– a. Tonic contraction = continual partial contraction muscle tone and posture.
– b. Isotonic contraction = tone stays the same, but muscle shortens movement.
– c. Isometric = length stays the same, but tone increases.
– d. Twitch = quick, jerky contraction in response to a single stimulus (done in lab with electricity.)
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Types of contraction (continued):• e. Summation - 2nd contraction is stronger if 2nd
stimulus is applied before relaxation of the first
contraction. • f. Treppe (unfused tetanus) (staircase phenomenon) -
muscle contracts more forcefully after a few contractions (warm up exercise ex.) to a maximum.
• g. Tetanic contraction (tetanus) - from series of stimulation with no relaxation period between. (Normal movements are by complete tetanus.)
• h. Convulsions = abnormal, uncoordinated tetanic contractions.
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• 3. Skeletal muscle organs contract on graded strength principle.
• 4. Skeletal muscle cells contract on the all-or-none principle (once threshold has been reached.)
• 5. Strength of contraction depends on:– a. Initial fiber length (Starling’s law of heart muscle)
= a stretched muscle contracts with more force.
– b. Metabolic condition (O2 and food supply)
– c. Number of fibers contracting (depends on frequency and intensity of stimulation.)
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• d. Previous contraction (warm up)• e. Load (recruitment) - lifting a pencil compared to
lifting a book.• f. Muscle fatigue - build up of lactic acid until muscle
can no longer contract O2 debt.
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Muscle Movement• 1. Skeletal Muscles move by pulling on
bones.• 2. Muscles are proximal to the part they
move.• 3. Muscles act in groups
– a. Prime movers - produce Work inthe movement
opposition to– b. Antagonists - relax when each
other the prime movers contract– c. Synergists contract at same time as
prime movers; help stabilize the movement
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4. Muscle movements• a. Flexion / extension =
decrease / increase angle between bones
• b. Adduction / abduction = lower to / raise from midline
• c. Rotation
• d. Pronation / supination = inward / outward turning of palm
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Naming of Muscles (pp 325-26)
• 1. Location - temporalis
• 2. Shape - deltoid• 3. Size - ____ maximus• 4. Direction of muscle
fibers - _____ oblique
• 5. Number of origins - triceps
• 6. Location of origin and/or insertion - sternocleidomastoid
• 7. Action of muscle - adductor _______