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Muscular:Jocelyn Gracia P.5 Anatomy - Coggle Diagram
Muscular:Jocelyn Gracia P.5 Anatomy
Sarcomere
extends from one Z line to the next
Striations consists of an alternating pattern of light & dark bands
I bands (light bands) made up of actin filaments, anchored to Z lines
A bands(dark bands) made up of overlapping thick & 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 H zone, consists of proteins that hold the Myosin filaments in place
Neuromuscular Junction
a synapse between a motor neuron & a muscle fiber that regulates
Muscle fiber membrane contains a motor end plate, in which the sarcolemma is tightly folded
The motor end plate contains specific receptors of the neurotransmitter
When an electrical impulse reaches the end of the axon of a motor neuron, synaptic vesicles release neurotransmitter into the snaptic cleft, the gap between the membranes of the neuron & muscle fiber
Neurotransmitters diffuse across the cleft, bind to the motor end plate, and stimulate the muscle fiber to contract
Sliding Filament Theory
A muscle contraction starts in the brain, where signals are sent along the motor neuron. Acetylcholine reaches the receptors on the muscle sarcolemma which causes and impulse.
The impulse travels down the membrane and into the tranverse tubules where it causes calcium to be released from the sarcoplasmic reticulum.
Calcium binds to a stucture on the actin that causes it to change shape
The change in shape allows myosin heads to form cross-bridges between the actin and the myosin.
Energy from the ATP is used to create a "power stroke" between the two filaments. The actin filament then slides inward and shortens, or contracts, the whole muscle.
Muscle Coverings
(Connective Tissue)
Fascia blends with the epimysium, the layer of connective tissue around each skeletal muscle
Perimysium extends inward from the epimysium;surrounds bundles of skeletal muscle fibers called fascicles
Each muscle cell is covered by a connective tissue layer called endomysium
Skeletal Muscles
Biceps Brachii:(attachments, location) has 2 origins, found in arm(brachium)
Pectoralis major:(action) extends digits(finger, toes)
Sternocleidomastoid: attaches to sternum, clavicle, and mastoid process
External Oblique:(location, direction)located near outside of body, and fibers run at a slant
Facial Muscles
Temporalis:elevation and retraction of mandible
Frontalis: raises eyebrows and forehead wrinkles
Orbicularis oculi: closure of the eyelid: winking, forced squeezing
Orbicularis oris: puckering the lips
Masseter: chewing; causing the mandible to lift causing the mouth to close
Platysma: widens the corner of the mouth, and draws the skin of the neck superiorly when the teeth are clenched
Zygomaticus: pulls the corner of the mouth upward& backward when smiling or laughing
Bucchanator: compresses the teeth against the cheeks
Muscles and their Functions
Smooth Muscle
Walls of hollow viscera, blood vessels; movement of viscera, peristalsis, vasoconstriction
single nucleus; lacks transverse tubules
Involuntary; contracts and relaxes slowly; single unit type is self-exciting; rhythmic
Cardiac Muscle
Wall of the heart; pumping action of the heart
single nucleus; well-developed transverse tubule system; intercalated discs separating adjacent cells
Involuntary; Network of cells contracts as a unit; self-exciting; rhythmic
Skeletal Muscle
Movement of bones at joints, maintenance of posture
many nuclei; well-developed transverse tubule system
Voluntary; Contracts and relaxes rapidly when stimulated by a motor neuron