Muscular Tissue

Basic function of muscular tissue

• movement of joint

• food in stomach

• blood in artery

• sweat out of gland

Ability of muscular tissue

• can contract (shorten) on demand when excited by stimulus

What is skeletal muscle surrounded by

• fascia (irregular CT)

• exists in relationship with CT

4 Functions

1. produce body movement

2. stabilizing body positions

3. storing and moving substances in the body

4. generating heat

4 properties

1. electrical excitability

2. contractility

3. extensibility

4. elasticity

What separates muscles from skin

subcutaneous tissue (hypodermis)

• composed of areolar CT and adipose tissue

• provides pathway for nerves, blood vessels and lymphatic vessels

• fascia holds muscles w similar functions together

3 layers of fascia

• epimysium

• perimysium

• endomysium

Epimysium

• outer layer of fascia

• surrounds entire muscle

• gives capsule that slides against other body structures as it changes shape

Perimysium

• surrounds groups of 10-100 muscle fibers

• separates into muscle fascicles

• “grain” in piece of meat

Endomysium

• penetrates interior of each muscle fascicle and separates individual muscle fibers from one another

• mostly reticular fibers

Tendon

• connects muscle to bone that anchors and bone that moves

Ligament

Connect bone to bone

What are muscle cells made of

Microfibrils (long tubes)

What are microfibrils made of

Sarcomeres

Sarcomere

• basic functional unit of muscle cell

  • generating force

What are sarcomeres made of

Actin and myosin

• slide past each other, becoming shorter

Actin

Makes up thin filaments

Myosin

Makes up thick filaments

• has heads bound to ATP

• hydrolyzes

• ADP & phosphate

Sliding filament mechanism

1. ATP hydrolyzes and becomes ADP & phosphate

2. binds to actin (cross-bridge)

3. myosin head performs power stroke (release of ADP & phosphate)

4. thin filament slides to sarcomere center

5. new ATP binds myosin head and lets it detach

Rigor mortis

Without ATP, myosin head would not detach

What does actin have

Tropomyosin, a regulatory protein that blocks myosin binding sites

• also has troponin

When neuron stimulates muscle, releases calcium which binds to troponin

Muscle regulation

Aging and muscle tissue

• between ages 30-50, undergo slow loss of skeletal muscle mass

• replaced by fibrous CT and adipose tissue

• relative number of slow oxidative fibers increase

• change in fiber type, causes slower and weaker