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Alanna Vargas Period 3 Muscular - Coggle Diagram
Alanna Vargas Period 3 Muscular
3 types of muscles & their functions
Skeletal: moves bones, voluntary, striated
Cardiac: heart muscle, pumps blood, involuntary, striated
Smooth: walls of organs, moves things through body, involuntary, not striated
Muscle coverings (connective tissue coverings)
Epimysium: around whole muscle
Perimysium: around bundles (fascicles)
Endomysium: around each fiber
All connect to form tendons
Sarcomere
Functional unit of a muscle fiber
Bounded by Z-lines
Contains thick (myosin) and thin (actin) filaments
A band = dark (myosin)
I band = light (actin)
H zone = center region with only myosin
M line = holds myosin in place
Neuromuscular junction
Point of communication between motor neuron and muscle fiber
Synaptic cleft = gap between them
Acetylcholine aka ACh = neurotransmitter released
Motor end plate = muscle membrane with ACh receptors
Enzyme acetylcholinesterase breaks down ACh to stop signal
Sliding filament theory of muscle contraction
1-Nerve signal → calcium released
2-Calcium moves tropomyosin
3-Myosin grabs actin
4-Myosin pulls actin → muscle shortens
5-ATP lets myosin let go and reset
Disorders associated with the Muscular system
Muscular dystrophy: weak muscles (genetic)
Myasthenia gravis: nerve signals blocked
Tetanus: muscles stay contracted
Cramp: sudden muscle tightening
Major functions of the muscular system
Movement – of body parts, blood, and materials
Posture & Stability – maintains body position.
Heat Production – muscles produce heat during contraction
Joint Stabilization – tendons and muscles support joints
Protection – muscles cushion internal organs
Action potential in a muscle fiber
Depolarization – Na⁺ rushes in after ACh binds
Propagation – wave travels along sarcolemma & T-tubules
Ca²⁺ released from SR
Repolarization – K⁺ exits; resting potential restored
Leads directly to contraction steps
Skeletal Muscles
Head/Neck: frontalis, orbicularis oculi, zygomaticus, masseter, sternocleidomastoid
Torso: pectoralis major, rectus abdominis, external oblique, trapezius, latissimus dorsi
Arms: deltoid, biceps brachii, triceps brachii
Legs: gluteus maximus, quadriceps, hamstrings, gastrocnemius, tibialis anterior