FUNCTIONS
• Produce movement
• Maintain posture
• Respiration
• Production of body heat - release excess heat
• Communication
• Constriction of organs and vessels
• Contraction of heart
TYPES OF MUSCLE
1. Skeletal Muscle
2. Cardiac Muscle
3. Smooth Muscle
FOUR MAJOR FUNCTIONAL CHARACTERISTICS
1. Contractility
> ability of muscle to shorten
2. Excitability
> capacity of muscle to respond
3. Extensibility
> stretched beyond its normal resting length
4. Elasticity
> ability of muscle to recoil
SKELETAL MUSCLE
• Attached by tendon to bones
• Cells are multinucleated
* Striated
> have visible banding
* Voluntary
> subject to conscious control
• Cells are surrounded and bundled by connective tissue
• Consists of skeletal muscle tissue, nervous tissue, connective tissue and adipose tissue
CONNECTIVE TISSUE COVERINGS
1. Epimysium
> Skeletal muscle
2. Perimysium
> muscle fascicles
3. Endomysium
> Muscle fiber
4. Fascia
> Outside epimysium (muscle to muscle)
ATTACHMENTS
• Tendon
> cord-like structure
• Aponeuroses
> sheet-like structure
Sites of Muscle Attachment
* Bones
* Cartilages
* Connective Tissue Coverings
MUSCLE FIBER STRUCTURE
• Sarcolemma
> plasma membranes
• Transverse Tubules (T-Tubules)
> tubelike inward folds
• Sarcoplasmic Reticulum
> specialized smooth endoplasmic reticulum
• Terminal Cisternae
> enlarged portions (SER)
• Sarcoplasm
> cytoplasm
> contains bumdles of protein filaments
• Myofibril
> bundles of myofilament
• Sarcomere
> contractile unit of muscle fiber
• Z disks
> separates sarcomere to another sarcomere
> network of protein fibers
• Thick Filaments (Myosin)
> composed of protein myosin
• Thin Filaments (Actin)
> protein actin
• I - Band
> light - staining bands
> consist only actin myofilament
• A - Band
> dark - staining bands
> extends the length of myosin myofilaments within sarcomere
ACTIN MYOFILAMENTS
1. Actin
> attachment sites for myosin myofilaments
> resemble strands of pearls twisted together
2. Troponin
> molecules that have binding sites for Ca
3. Tropomyosin
> block the myosin myofilaments
MYOSIN MYOFILAMENTS
• Myosin Heads
> resemble golf club heads
PROPERTIES OF SKELETAL MUSCLE ACTIVITY
1. Irritability
> receive and respond to stimulus
2. Contractility
> shorten
GRADED RESPONSES
• different degrees of skeletal muscle shortening
TYPES OF GRADED RESPONSES
1. Twitch
> single , brief contraction
Three Phases of Twitch:
• Lag Phase (Latent Phase)
> application of stimulus
> beginning of contraction
• Contraction Phase
> muscle contracts
• Relaxation Phase
> muscle relaxes
2. Tetanus
> does not return to resting state
3. Unfused (Incomplete) Tetanus
> relaxation occurs between contractions (ATP)
4. Fused (Complete) Tetanus
> no evidence of relaxation
> sustained muscle contraction
