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MUSCLE TISSUE
• IS THE ONLY TISSUE IN THE BODY THAT
IS SPECIALIZED FOR CONTRACTION.
• MUSCLE CONTRACTION ALLOW BODY
PARTS MOVEMENT.
• THE BODY CONTAIN THREE TYPES OF
MUSCLE TISSUE:• SKELETAL – SMOOTH –CARDIAC.
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SKELETAL MUSCLE STRUCTURE
• SKELETAL MUSCLES ARE ATTACHED TO
BONES BY TENDONS.
• MUSCLES ARE ATTACHED TO EACH
OTHER BY LIGAMENTS OR APONEUROSIS
• MUSCLES ARE MADE OF FASCICLES >
FIBERS > MYOFIBRILES > FILAMENTS.
• DENSE CONNECTIVE TISSUE SURROUND
EACH FIBER, EACH FASCICLE AND THE
ENTIRE MUSCLE.
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THE MUSCLE FIBER
• A MUSCLE FIBER IS A MULTINUCLEATED
LONG, THIN MUSCLE CELL THAT EXTEND
THE FULL LENGTH OF THE MUSCLE.
• THE CELL MEMBRANE OF THE MUSCLE
FIBER IS CALLED THE SARCOLEMMA AND
ITS CYTOPLASM IS CALLED SARCOPLASM
• EACH MUSCLE FIBER IS MADE OF MANY
THIN THREADS CALLED MYOFIBRILS.
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THE MYOFIBRIL
• MYOFIBRILS ARE THE CONTRACTILE
ELEMENTS OF EACH MUSCLE FIBER.
• A MYOFIBRIL IS MADE FROM TWO TYPES
OF PROTEIN FILAMENTS:• ACTIN FILAMENTS:- THIN FILAMENTS.
• MYOSIN FILAMENTS:- THICK FILAMENTS.
• THE ARRANGEMENT OF ACTIN & MYOSIN
FILAMENTS WITHIN A MUSCLE FIBER
PRODUCE THE MUSCLE STRIATIONS.
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THE SARCOMERE
• A SARCOMERE IS THE SMALLEST PART
OF A MYOFIBRIL THAT IS CAPABLE OF
CONTRACTION.
• EACH SARCOMERE EXTEND FROM ONE ‘Z’
LINE TO THE NEXT ‘Z’ LINE.
• THE ACTIN FILAMENTS ARE ATTACHED
TO THE ‘Z’ LINES WHILE THE MYOSIN
FILAMENTS EXTEND INBETWEEN THE
ACTIN FILAMENTS.
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MUSCLE EXCITATION
• IN ORDER FOR MUSCLES TO CONTRACT
THEY MUST BE STIMULATED BY NERVE
SIGNALS FROM EITHER THE BRAIN OR
THE SPINAL CORD.
• NERVE SIGNALS ARE CARRIED BY MOTOR
NEURONS TO EACH MUSCLE FIBER.
• ONE MOTOR NEURON PLUS ALL THE
MUSCLE FIBERS TO WHICH THE NEURON
IS ATTACHED FORM A MOTOR UNIT.
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A MOTOR UNIT
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THE NEUROMUSCULAR JUNCTION
• THE TERMINAL PART OF A MOTOR
NEURON THAT LEADS TO A MUSCLE
FIBER IS CALLED THE AXON.
• THE NEUROMUSCULAR JUNCTION IS THE
POINT OF CONNECTION BETWEEN AN
AXON TERMINAL AND THE SARCOLEMMA
OF THE MUSCLE FIBER.
• AXON TIPS CONTAIN VESICLES OF THE
NEUROTRANSMITTER ACETYLCHOLINE. 11
THE NEUROMUSCULAR JUNCTION
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MUSCLE EXCITATION AND
CONTRACTION
• WHEN A NERVE SIGNAL CARRIED BY A
MOTOR NEURON REACH THE AXON TIP,
ACETYLCHOLINE IS RELEASED TO
STIMULATE THE MUSCLE FIBER.
• THE ATTACHMENT OF ACETYLCHOLINE
TO THE SARCOLEMMA WILL TRIGER A
SERIES OF REACTIONS THAT CAUSES
THE MUSCLE FIBER SARCOMERES TO
CONTRACT.
• {SLIDING FILAMENTS THEORY}
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CONTRACTION OF SARCOMERES
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ENERGY FOR CONTRACTION
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MUSCLE CONTRACTION
• MUSCLE TWITCH:- A SINGLE MUSCLE
CONTRACTION IN RESPONSE TO A
SINGLE STIMULUS OR NERVE SIGNAL.
• GRADED RESPONSE:- AS THE STIMULUS
STRENGTH INCREASES, CONTRACTIONS
GET STRONGER AND STRONGER.
• TETANIC CONTRACTIONS:- CONTINUOUS
CONTRACTIONS WITHOUT RELAXATIONS
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A MUSCLE TWITCH
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Figure 07.09
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ORIGIN AND INSERTION
• ORIGIN:- THE MUSCLE POINT OF
ATTACHMENT TO AN IMMOVABLE BONE.
• INSERTION:- THE MUSCLE POINT OF
ATTACHMENT TO A MOVABLE BONE.
• WHEN A MUSCLE CONTRACTES, THE
INSERTION BONE IS PULLED TO WARDS
THE ORIGIN BONE.
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Figure 07.10
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SUPERFICIAL MUSCLES
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MUSCLES OF FACIAL EXPRESSION
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