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

2 MUSCLE TISSUE IS THE ONLY TISSUE IN THE BODY THAT IS SPECIALIZED FOR CONTRACTION. IS THE ONLY TISSUE IN THE BODY THAT IS SPECIALIZED FOR CONTRACTION. MUSCLE CONTRACTION ALLOW BODY PARTS MOVEMENT. MUSCLE CONTRACTION ALLOW BODY PARTS MOVEMENT. THE BODY CONTAIN THREE TYPES OF MUSCLE TISSUE:- THE BODY CONTAIN THREE TYPES OF MUSCLE TISSUE:- SKELETAL – SMOOTH –CARDIAC. SKELETAL – SMOOTH –CARDIAC.

3 SKELETAL MUSCLE STRUCTURE SKELETAL MUSCLES ARE ATTACHED TO BONES BY TENDONS. SKELETAL MUSCLES ARE ATTACHED TO BONES BY TENDONS. MUSCLES ARE ATTACHED TO EACH OTHER BY LIGAMENTS OR APONEUROSIS MUSCLES ARE ATTACHED TO EACH OTHER BY LIGAMENTS OR APONEUROSIS MUSCLES ARE MADE OF FASCICLES > FIBERS > MYOFIBRILES > FILAMENTS. MUSCLES ARE MADE OF FASCICLES > FIBERS > MYOFIBRILES > FILAMENTS. DENSE CONNECTIVE TISSUE SURROUND EACH FIBER, EACH FASCICLE AND THE ENTIRE MUSCLE. DENSE CONNECTIVE TISSUE SURROUND EACH FIBER, EACH FASCICLE AND THE ENTIRE MUSCLE.

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5 THE MUSCLE FIBER A MUSCLE FIBER IS A MULTINUCLEATED LONG, THIN MUSCLE CELL THAT EXTEND THE FULL LENGTH OF THE MUSCLE. 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 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. EACH MUSCLE FIBER IS MADE OF MANY THIN THREADS CALLED MYOFIBRILS.

6 THE MYOFIBRIL MYOFIBRILS ARE THE CONTRACTILE ELEMENTS OF EACH MUSCLE FIBER. MYOFIBRILS ARE THE CONTRACTILE ELEMENTS OF EACH MUSCLE FIBER. A MYOFIBRIL IS MADE FROM TWO TYPES OF PROTEIN FILAMENTS:- A MYOFIBRIL IS MADE FROM TWO TYPES OF PROTEIN FILAMENTS:- ACTIN FILAMENTS:- THIN FILAMENTS. ACTIN FILAMENTS:- THIN FILAMENTS. MYOSIN FILAMENTS:- THICK FILAMENTS. MYOSIN FILAMENTS:- THICK FILAMENTS. THE ARRANGEMENT OF ACTIN & MYOSIN FILAMENTS WITHIN A MUSCLE FIBER PRODUCE THE MUSCLE STRIATIONS. THE ARRANGEMENT OF ACTIN & MYOSIN FILAMENTS WITHIN A MUSCLE FIBER PRODUCE THE MUSCLE STRIATIONS.

7 THE SARCOMERE A SARCOMERE IS THE SMALLEST PART OF A MYOFIBRIL THAT IS CAPABLE OF CONTRACTION. 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. 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. THE ACTIN FILAMENTS ARE ATTACHED TO THE ‘Z’ LINES WHILE THE MYOSIN FILAMENTS EXTEND INBETWEEN THE ACTIN FILAMENTS.

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9 MUSCLE EXCITATION IN ORDER FOR MUSCLES TO CONTRACT THEY MUST BE STIMULATED BY NERVE SIGNALS FROM EITHER THE BRAIN OR THE SPINAL CORD. 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. 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. ONE MOTOR NEURON PLUS ALL THE MUSCLE FIBERS TO WHICH THE NEURON IS ATTACHED FORM A MOTOR UNIT.

10 A MOTOR UNIT

11 THE NEUROMUSCULAR JUNCTION THE TERMINAL PART OF A MOTOR NEURON THAT LEADS TO A MUSCLE FIBER IS CALLED THE AXON. 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. 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. AXON TIPS CONTAIN VESICLES OF THE NEUROTRANSMITTER ACETYLCHOLINE.

12 THE NEUROMUSCULAR JUNCTION

13 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. 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. THE ATTACHMENT OF ACETYLCHOLINE TO THE SARCOLEMMA WILL TRIGER A SERIES OF REACTIONS THAT CAUSES THE MUSCLE FIBER SARCOMERES TO CONTRACT. {SLIDING FILAMENTS THEORY} {SLIDING FILAMENTS THEORY}

14 CONTRACTION OF SARCOMERES

15 ENERGY FOR CONTRACTION

16 MUSCLE CONTRACTION MUSCLE TWITCH:- A SINGLE MUSCLE CONTRACTION IN RESPONSE TO A SINGLE STIMULUS OR NERVE SIGNAL. 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. GRADED RESPONSE:- AS THE STIMULUS STRENGTH INCREASES, CONTRACTIONS GET STRONGER AND STRONGER. TETANIC CONTRACTIONS:- CONTINUOUS CONTRACTIONS WITHOUT RELAXATIONS TETANIC CONTRACTIONS:- CONTINUOUS CONTRACTIONS WITHOUT RELAXATIONS

17 A MUSCLE TWITCH

18 Figure 07.09

19 ORIGIN AND INSERTION ORIGIN:- THE MUSCLE POINT OF ATTACHMENT TO AN IMMOVABLE BONE. ORIGIN:- THE MUSCLE POINT OF ATTACHMENT TO AN IMMOVABLE BONE. INSERTION:- THE MUSCLE POINT OF ATTACHMENT TO A MOVABLE 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. WHEN A MUSCLE CONTRACTES, THE INSERTION BONE IS PULLED TO WARDS THE ORIGIN BONE.

20 Figure 07.10

21 SUPERFICIAL MUSCLES

22 MUSCLES OF FACIAL EXPRESSION