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Emmanuel Flores Per 5 Muscular System - Coggle Diagram
Emmanuel Flores Per 5
Muscular System
Action potential in a muscle fiber
Initiation
Neuromuscular Junction
: The action potential begins when a motor neuron releases the neurotransmitter acetylcholine (ACh) into the synaptic cleft at the neuromuscular junction.
Binding to Receptors
: ACh binds to receptors on the muscle fiber’s sarcolemma (membrane), opening sodium (Na+) channels.
Depolarization
: This influx of Na+ ions depolarizes the muscle fiber’s membrane, initiating an electrical impulse (action potential).
Propagation
Travel Along Sarcolemma
: The action potential spreads across the sarcolemma, the muscle fiber’s outer membrane.
Down T-Tubules
: It then travels down the T-tubules (invaginations in the sarcolemma) to reach the inner areas of the muscle fiber.
Signal Distribution
: T-tubules help evenly distribute the action potential throughout the fiber, ensuring a coordinated contraction.
Calcium Release
Sarcoplasmic Reticulum Activation
: The action potential reaches the sarcoplasmic reticulum, a specialized organelle storing calcium ions (Ca2+).
Calcium Floods Sarcomere
: The sarcoplasmic reticulum releases Ca2+ into the sarcoplasm (muscle cell cytoplasm), where it binds to troponin on the actin filaments.
Trigger for Contraction
: This calcium binding moves tropomyosin, exposing binding sites on actin and allowing the cross-bridge cycle to begin, which leads to muscle contraction.
Sarcomere
Structure
Z-line to Z-line
: The sarcomere is the functional unit of muscle contraction, defined by the area between two Z-lines (also called Z-discs).
Actin Filaments (Thin)
: Anchored to the Z-line, these filaments slide inward during contraction.
Myosin Filaments (Thick)
: Located between actin filaments, these filaments have myosin heads that interact with actin.
Contraction
Cross-Bridge Formation
: Myosin heads attach to binding sites on the actin filaments, forming cross-bridges.
Power Stroke
: The myosin heads pivot, pulling actin filaments towards the center of the sarcomere, which shortens the muscle fiber.
Detachment and Recocking
: ATP binds to myosin, allowing it to detach from actin, then hydrolyzes to reposition the myosin head for the next cycle.
Regions of the Sarcomere
A-band
: The region that includes the entire length of the myosin filaments; remains constant in length during contraction.
I-band
: The light region containing only actin filaments; shortens during contraction.
H-zone
: The central region within the A-band where only myosin filaments are present; it shortens and may disappear during contraction.
M-line
: The middle line within the H-zone, where myosin filaments are anchored, stabilizing their position during contraction.
Disorders associated with the Muscular system
Myasthenia Gravias
Description: An autoimmune disorder where antibodies attack the neuromuscular junction, causing muscle weakness.
Cause: Autoimmune response targeting acetylcholine receptors.
Symptom: Muscle weakness that worsens with activity and improves with rest, especially in the face and neck.
Treatment: Immunosuppressive drugs, acetylcholinesterase inhibitors, and plasmapheresis to reduce antibodies.
Fibromyalgia
Description: A chronic condition causing widespread muscle pain and tenderness, often with fatigue and mood issues.
Cause: The exact cause is unknown; factors may include genetics, infections, and physical or emotional trauma.
Symptom: Widespread musculoskeletal pain, especially tender points around joints.
Treatment: Pain relievers, antidepressants, and lifestyle therapies like exercise and stress management.
Cerebral Palsy
Description: A group of disorders that affect movement and muscle tone, often due to brain damage before or during birth.
Cause: Brain injury or abnormal development, often from birth complications, infections, or genetic factors.
Symptom: Muscle stiffness, involuntary movements, and poor coordination.
Treatment: Physical and occupational therapy, muscle relaxants, surgery in severe cases.
Muscular Dystrophy
Description: A group of genetic disorders that progressively weaken and degenerate skeletal muscles.
Cause: Genetic mutations that interfere with muscle protein production, often involving dystrophin.
Symptom: Progressive muscle weakness, especially in the legs and pelvis.
Treatment: Physical therapy, corticosteroids to slow progression, and sometimes gene therapy.
Myositis
Description: Inflammation of the muscles, often leading to muscle weakness and pain.
Cause: Autoimmune response or infection, with types including polymyositis and dermatomyositis.
Symptom: Muscle pain, weakness, and sometimes skin rashes.
Treatment: Corticosteroids, immunosuppressants, and physical therapy to regain strength.
Major functions of the muscular system
Movement: Involves skeletal muscles contracting to move bones.
Posture Maintenance: Muscles keep the body upright and stable against gravity.
Joint Stabilization: Muscles surrounding joints provide stability and prevent dislocation.
Heat Production: Muscles generate heat as they contract, crucial for body temperature regulation.
Circulation: Cardiac muscle pumps blood, and smooth muscles in blood vessels help maintain blood pressure.
Digestion: Smooth muscles aid in moving food through the digestive system.
Sliding filament theory of muscle contraction
Cross-Bridge Cycle
Attachment: Myosin heads (on thick filaments) attach to active binding sites on actin filaments (thin filaments), forming cross-bridges.
Power Stroke: Once attached, the myosin heads pivot, pulling the actin filaments toward the center of the sarcomere, shortening it.
Detachment: After the power stroke, ATP binds to the myosin head, causing it to release from actin.
Re-cocking: The ATP is hydrolyzed, re-energizing and repositioning the myosin head for the next cycle.
Role of ATP
Energy for Movement: ATP provides the energy needed for myosin heads to perform the power stroke and slide actin filaments.
Detachment and Re-cocking: ATP is essential for detaching the myosin head from actin and resetting it, allowing repeated cycles for sustained contraction.
Calcium Ions
Release from Sarcoplasmic Reticulum: When an action potential reaches the muscle fiber, calcium ions (Ca2+) are released from the sarcoplasmic reticulum.
Binding to Troponin: Calcium binds to the troponin complex on actin filaments, causing a conformational change.
Tropomyosin Shift: This change moves tropomyosin away from actin’s binding sites, allowing myosin heads to attach to actin.
Muscle coverings (connective tissue coverings)
Epimysium
Location: The outermost layer of connective tissue that surrounds the entire muscle.
Function: Provides structural support and protects the muscle from friction against surrounding muscles and bones. It also contributes to the muscle's strength by integrating with tendons, which attach the muscle to bones.
Perimysium
Location: A connective tissue layer that surrounds bundles of muscle fibers called fascicles within the muscle.
Function: Separates and organizes muscle fibers into fascicles, allowing each bundle to function independently. It also houses blood vessels and nerves that supply the muscle fibers within each fascicle, supporting efficient nutrient delivery and signal transmission.
Endomysium
Location: The innermost layer of connective tissue, surrounding each individual muscle fiber within a fascicle.
Function: Provides a thin, protective layer around each muscle fiber, helping maintain its shape and facilitating exchange of nutrients and waste between the muscle fibers and the surrounding capillaries. It also contributes to the fine control and flexibility of muscle movements.
Neuromuscular junction
Synapse Formation
Neuromuscular Junction (NMJ)
: The specific synapse where a motor neuron meets a muscle fiber, allowing for communication between the nervous system and the muscular system.
Synaptic Cleft
: The small gap between the neuron and muscle fiber where neurotransmitters are released.
Motor End Plate
: Specialized part of the muscle fiber’s membrane at the NMJ, with receptors ready to bind the neurotransmitter.
Acetylcholine (ACh) Release
Vesicle Release
: When an action potential (electrical signal) reaches the end of the motor neuron, it triggers the release of acetylcholine from vesicles into the synaptic cleft.
Binding to Receptors
: Acetylcholine diffuses across the synaptic cleft and binds to specific receptors on the motor end plate of the muscle fiber.
Ion Channels Open
: This binding causes ion channels to open, allowing sodium ions (Na+) to flow into the muscle fiber, which initiates depolarization.
Depolarization and Action Potential
Depolarization
: The influx of Na+ ions changes the muscle fiber’s membrane potential, creating an electrical impulse along the sarcolemma (muscle fiber membrane).
Action Potential Propagation
: This action potential travels along the sarcolemma and down into the muscle fiber via T-tubules.
Calcium Release
: The action potential triggers the sarcoplasmic reticulum to release calcium ions (Ca2+), which are essential for muscle contraction as they allow actin and myosin to interact.
Names of all the skeletal muscles (including the facial muscles)
Upper Body Muscles
Shoulders and Arms
:
Deltoid
: Shoulder abduction and flexion.
Biceps Brachii
: Flexes the elbow and rotates the forearm.
Triceps Brachii
: Extends the elbow.
Brachialis
: Flexes the elbow, located under the biceps.
Chest and Back
:
Pectoralis Major
: Adducts and flexes the arm at the shoulder.
Latissimus Dorsi
: Extends, adducts, and medially rotates the arm.
Trapezius
: Elevates, retracts, and rotates the scapula.
Rhomboids
: Retracts and stabilizes the scapula.
Core Muscles
Abdominal Muscles
:
Rectus Abdominis
: Flexes the lumbar spine, stabilizes the core.
External Obliques
: Rotates and laterally flexes the torso.
Internal Obliques
: Works with external obliques for torso rotation and flexion.
Transversus Abdominis
: Compresses abdominal contents, providing core stability.
Back Muscles
:
Erector Spinae
: Extends and stabilizes the spine.
Multifidus
: Stabilizes vertebrae during movement.
Lower Body Muscles
Thigh Muscles
:
Quadriceps
: Includes
rectus femoris
,
vastus lateralis
,
vastus medialis
, and
vastus intermedius
; extends the knee.
Hamstrings
: Includes
biceps femoris
,
semitendinosus
, and
semimembranosus
; flexes the knee and extends the hip.
Adductor Group
: Includes
adductor longus
,
adductor brevis
, and
adductor magnus
; adducts the thigh.
Calf and Lower Leg Muscles
:
Gastrocnemius
: Plantar flexes the foot and flexes the knee.
Soleus
: Plantar flexes the foot.
Tibialis Anterior
: Dorsiflexes and inverts the foot.
Gluteal Muscles
:
Gluteus Maximus
: Extends and laterally rotates the hip.
Gluteus Medius
: Abducts and medially rotates the hip.
Gluteus Minimus
: Also assists in hip abduction.
Facial Muscles
Mouth and Cheek
:
Orbicularis Oris
: Controls movements of the mouth and lips.
Buccinator
: Compresses the cheek, helping in chewing.
Zygomaticus
: Raises the corners of the mouth, as in smiling.
Eye Muscles
:
Orbicularis Oculi
: Closes the eyelids.
Jaw Muscles
:
Masseter
: Elevates the jaw, crucial for chewing.
Temporalis
: Assists in jaw closure and elevation.
Forehead
:
Frontalis
: Raises the eyebrows and wrinkles the forehead.
3 types of muscles & their functions
Skeletal Muscle
Control: Voluntary, meaning it’s consciously controlled by the nervous system.
Appearance: Striated (striped) due to the arrangement of actin and myosin filaments in sarcomeres.
Location and Function: Primarily attached to bones and responsible for body movements like walking, lifting, and facial expressions.
Key Characteristics: Multinucleated cells and organized, parallel fibers for powerful, rapid contractions.
Cardiac Muscle
Control: Involuntary; it contracts automatically without conscious input, regulated by the autonomic nervous system and intrinsic conduction.
Appearance: Striated with unique intercalated discs, which contain gap junctions and desmosomes that help synchronize heartbeats.
Location and Function: Found only in the heart, where it continuously pumps blood throughout the body.
Key Characteristics: Branched fibers that form a network, allowing coordinated contractions for effective blood circulation.
Smooth Muscle
Control: Involuntary, controlled by the autonomic nervous system.
Appearance: Non-striated due to a different arrangement of actin and myosin filaments; fibers are spindle-shaped.
Location and Function: Found in walls of hollow organs (e.g., stomach, intestines, blood vessels) where it helps regulate functions like digestion, vasodilation, and peristalsis.
Key Characteristics: Can sustain contractions for long periods and respond to both neural and hormonal stimuli, allowing it to maintain essential body functions.