CHAPTER 7 MUSCULAR SYSTEM Copyright The McGraw-Hill Companies,

CHAPTER 7 MUSCULAR SYSTEM Copyright  The McGraw-Hill Companies,

CHAPTER 7 MUSCULAR SYSTEM Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 1 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. 2

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. 3 4

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. 5 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. 6

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. 7 8 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.

9 A MOTOR UNIT 10 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 12 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} 13 CONTRACTION OF SARCOMERES 14

ENERGY FOR CONTRACTION 15 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 16 A MUSCLE TWITCH

17 Figure 07.09 18 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. 19

Figure 07.10 20 SUPERFICIAL MUSCLES 21

MUSCLES OF FACIAL EXPRESSION 22

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