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Muscular system Bella Villa Period 1 - Coggle Diagram
Muscular system
Bella Villa
Period 1
Major Functions
Joint stabilization: intact muscle tone reinforces articulating bone contractions
Heat Generation: heat released during muscle contraction maintains homeostatic body temp
Posture/Body position maintenance: continuous tiny adjustments to combat gravity
Protection/Support: shields deep internal thoracic, abdominal organs
Movement production: walking, running, localized movements (facial expressions)
Neuromuscular Junction
Axon Terminal: The ending tip of a motor neuron containing synaptic vesicles filled with ACh
Synaptic Cleft: The fluid filled physical gap space dividing the neuron terminal and muscle cell
Motor End Plate: Specialized pocket region of the muscles sarcolemma packed with ACh receptors
Neurotransmitter Release: Action potential arrives, voltage gated Ca channels open, Exocytosis of ACh into cleft, ACh binds to motor endplate receptors
ACh Breakdown: Acetylcholinesterase enzyme rapidly degrades ACh in the cleft to prevent sustained contraction
Sliding filament of muscle contraction
Step 2: Power Stroke: Myosin head pivots and bends, releasing ADP and inorganic phosphate, dragging the thin acting Filament along m line
Step 3: Cross bridge detachment: A new ATP molecule binds to the myosin head, breaking the link with actin
Step 1: Cross bridge formation: Activated myosin head binds to exposed actin binding site
Step 4: Cocking of myosin head: ATP hydrolyzes into ADP, resetting the myosin head into its energized high energy state
Muscle coverings
Endomysium: Fine, delicate reticular sheath surrounding each separate individual muscle fiber cell
Deep Fascia/Tendon: Coalescing blending layers extending past the muscle belly to anchor directly onto bones
Perimysium: Fiborous mid teir sheath wrapping around a cluster bundle of muslce cells called a fascicle.
Epimysium: Dense outer overcoat wrapping around the entire superficial belly of the muscle organ
Skeletal muscles
Thorax/Abdomen: Pectoralis major, Rectus abdominis, External obliques, Latissimus dorsi
Arm/Forearm: Biceps brachii, triceps brachii, brachioradilalis
Neck/Shoulder: Sternocleidomastoid, trapezius, deltoid
Hip/Thigh: Gluteus maximus, iliopsoas, quadriceps femoris, Rectus femoris, vastus lateralis, vastus medialis, vastus intermedius, hamstrings, biceps femoris, semitendinosus, semimembranosus, gracilis, sartorius
Facial/Head: Frontalis, Obicularis oculi, Orbicularis Oris, Masseter, Temporalis, Zygomaticus
Lower Leg: Tibialis anterior, Gastrocenius, Soleus
Sarcomere
I band: Light strip consisting of thin acting filaments flanking the Z line
H zone: inner zone within the A band where thick filaments exist without thin filament overlap
A band: Dark central strip spanning the full length of the thick myosin filament
M line: Exact structural midpoint center of the sarcomere anchoring thick filaments
Z discs/line: Anchor boundaries marking the start and finish of individual functional sarcomere
Myofilaments
Thick Filament(myosin): Protein with projecting golf club like globular heads
Thin Filament (acting complex): Composedof actin, tropomyosin, troponin
3 types of muscles
Cardiac Muscle: Striated, branched, single nucleus, intercalated discs. Involuntary; contracts heart walls to circulate blood through the cardiovascular grid
Smooth Muscle: Non straited, spindle cells, single nucleus
Involuntary, found in walls of hallow internal organs to propel
Skeletal Muscle: Straited, multinucleated, cylindrical fibers
Voluntary, attached to skeleton to facilitate locomotion
Action potential in muscle fiber
Depolrization: local threshold is breached; Voltaged gated Na channels open down the sarcolemma generating an electrical impulses action potential
Propagation: Action potential sweeps along the outer sarcolemma surface and plunges down deep into the cell interiorvia t tubules
Generation of End Plate Potential: ACh binding opens chemically gated ion channels: Na rushes inward
Calcium Release: The impulse travelling down t tubules shifts voltage sensors prompting the sarcoplasmic reticulum to dump stored Ca ions directly into the sarcoplasm
Disorders
Fibromyalgia: Chronic neural condition marked by widespread musculoskeletal pain, fatigue, and localized tendresness
Muscle Strain: Microscopic tearing injury to muscle fibers or tendons due to mechanical overstretching
Myasthenia Gravis: Autoimmune attack where antibodies destroy ACh receptors at the NMJ causing progressive chronic muscle weakness
Tetanus: Bacterial Toxin infection causing continuous, painful involuntary spasms and locking contractions of skeletal muscles
Muscular Dystrophy: Inherited genetic defect leading to missing dystrophin protein, triggering progressive muscle mass degradation.