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Muscular System Camila CastilloCruz P.2 - Coggle Diagram
Muscular System
Camila CastilloCruz P.2
Major Functions of the Muscular System
Muscles are organs that generate force to cause all types of movements
Support
Heat Generation
Blood Circulation
3 Types of Muscles Found and their Functions
Cardiac Muscle:
Complex membrane junctions, called intercalated discs, join cells and transmit the force of contraction from one cell to the next
Smooth Muscle:
Reaction between actin and myosin
Stimulated by membrane impulses
Hormones can stimulate
Skeletal Muscle:
Muscles contraction involves several events that result in the shortening of sarcomeres and the pulling of the muscle against its attatchements
Major Skeletal Muscles
Pectoralis Major
Deltoid
Extensor Digitorum
Biceps Brachaii
Sternocleidomastoid
External Oblique
Sarcomere
Myofibrils are made up of many units called sarcomeres, joined end-to-end
A sarcomere extends from one Z-line to the next
Striations consist of an alternating pattern of light and dark band
I-bands are made up of actin filaments which are anchored to the Z-lines
A-bands are made up of overlapping thick and thin filaments
In the center of the A-band is the H-zone, which consists of myosin filaments only
The M-line, in the center of the H-zone, consist of proteins that hold the myosin filaments in place
Neuromuscular Junction
Skeletal muscle fibers contract only when stimulated by a motor neuron
Each skeletal muscle fiber (cell) is functionally connected to the axon of a motor neuron, creating a synapse
The neuron communicates with the muscle fiber by way of chemicals called neurotransmitters, which are released at the synapse
The cytoplasm of the distal end of the motor neuron contains numerous mitochondria and synaptic vesicles storing neurotransmitters
The muscle fiber membrane in this area contain a specialized region called the motor end plate, in which the sarcolemma is tightly folded
The motor end plate contains specific receptors for the neurotransmitter
When an electrical impulse reaches the end of the axon of a motor neuron, synaptic vesicles release neurotransmitters into synaptic cleft, the gap between membranes of the neuron and muscle fiber
The neurotransmitters diffuse across the cleft, bind to the motor end plate, and stimulate the muscle fiber to contract
Sliding Filament Theory of Muscle Contraction
The brain or spinal cord sends an impulse to the muscle. The impulse travels down the motor neuron and reaches a neuromuscular junction where it releases acetylcholine, which triggers the impulse in the muscle
The impulse travels through the plasma membrane (sarcolemma) and down T tubules surrounding the myofibrils. As the impulse passes through the T tubules, it causes the sarcoplasmic reticulum surrounding the T tubule to release calcium ions into the sarcoplasm, eventually reaching the sarcomere.
The calcium binds to troponin located on the actin filament, causing tropomysion to move and expose bidning sites for mysion.
ADP and P, are released from myosin, which causes the mysion to move. This movement is called the power stroke.
The myosin head now binds to actin and forms a crossbridge
ATP binds to myosin causing it to release the actin and reverting ATP into ADP and P. The myosin is now ready to form another crossbridge and the cycle of contraction will continue until the impulse stops.
Once the impulse stops, Calcium is released from troponin causing tropomyosin to cover the binding sites and prevent contraction, Calcium returns to the SR and waits for another impulse. This is relaxation.
Muscle Coverings
Fascia
: Layers of dense connective tissue, surround and separate each muscle
Aponeuroses
: Sometimes muscles are connected to each other by broad sheets of this tissue
Epimysium
: Layer of connective tissue around each skeletal muscle
Muscle Disorders
Myositis
:
Description: Inflammation of the muscle
Causes or Risk Factors: Infection, muscle trauma, medication induced
Symptoms: Muscle weakness, myalgia, rash
Treatments: Medication, antibiotics, reduce inflammation
Fibromyalgia:
Description: Muscle pain
Causes or Risk Factors: Cause unknown, physical trauma, infection
Symptoms: Tender points, fatigue, depression
Treatments: Physical therapy, massage, medication
Muscular Dystrophy:
Description: Muscle weakness and atrophy
Causes or Risk factors: Genetic, Myotonic, Duchenne
Symptoms: Mental Retardation, Eyelid drooping, delayed motor skills
Treatment: No cure, Physical Therapy, Medication