Muscular Tissue

skeletal, cardiac, and smooth

• autonomic (involuntary) division of the nervous system
• and by hormones released by endocrine glands

• producing body movements,
• stabilizing body positions,
• storing and moving substances within the body,
• generating heat.

As muscular tissue contracts, it produces heat

• Electrical excitability (action potentials)
• Contractility
• Exstendiblity
• Elasticity

a property of both muscle and nerve cells

• is the ability to respond to certain stimuli by producing electrical signals
• called action potentials.
• Action
• potentials can travel along a cell's plasma membrane due to the presence of
• specific voltage-gated channels.

• One is autorhythmic electrical signals arising in the muscular tissue itself, as in the heart's pacemaker.
• The other is chemical stimuli, such as neurotransmitters released by neurons, hormones distributed by the blood, or even local changes in pH.

• the ability of muscular tissue to contract forcefully when stimulated by an
• action potential

the ability of muscular tissue to stretch without being damaged

• ability of muscular tissue to return to its original length and shape after
• contraction or extension.

Perimysium bundles groups of muscle fibers into fascicles

• is composed of areolar connective tissue and adipose tissue
• It provides a pathway for nerves, blood vessels, and lymphatic vessels to enter and exit muscles.

• is a dense sheet or broad band of irregular connective tissue that lines the
• body wall and limbs and supports and surrounds muscles and other organs of the
• body.

• allows free movement of muscles,
• carries nerves, blood vessels, and lymphatic vessels,
• and fills spaces between muscles

• Epimysium
• Perimysium
• Endomysium

• Outermost layer
• encirculing the entire muscle

• surrounds groups of 10 to 100 or more muscle fibers, separating them into
• bundles called fascicles (FAS-i-kuls =
• little bundles).

• Penetrating the interior of each fascicle and separating individual muscle fibers from one another
• a thin sheath of areolar connective tissue.

• a cord of dense regular connective tissue composed of parallel bundles of
• collagen fibers that attach a muscle to the periosteum of a bone

• When the connective tissue elements extend as a broad, flat layer, the tendon
• ie the epicranial aponeurosis on top of the skull between the frontal and occipital
• bellies of the occipitofrontalis muscle

The neurons that stimulate skeletal muscle to contract

• bring in oxygen and nutrients
• and remove heat and the waste products of muscle
• metabolism

• each skeletal muscle fiber arises during embryonic development from the fusion
• of a hundred or more small mesodermal cells called myoblasts

The sarcoplasmic reticulum releases calcium ions to trigger muscle contraction

• the sarcolemma and through the T tubules, quickly spreading throughout the muscle fiber.
• This arrangement ensures that an action potential excites all parts of the muscle fiber at essentially the same instant.

• thick filaments
• and thin filaments

• thick filament, smallest
• myofibril,
• muscle fiber - largest

Sarcomeres are separated from one another by Z discs

• Narrow, plate-shaped regions of dense material that separate one sarcomere
• from the next.

• The dark, middle part of the sarcomere that extends the entire length of the thick filaments
• and also includes those parts of the thin filaments that overlap with the thick filaments.

• The lighter, less dense area of the sarcomere that contains the rest of the thin filaments but no thick filaments.
• A Z disc passes through the center of each I band

A narrow region in the center of each A band that contains thick filaments but no thin filaments.

A region in the center of the H zone that contains proteins that hold the thick filaments together at the center of the sarcomere.

• (1) contractile proteins, which generate force during contraction;
• (2) regulatory proteins, which help switch the contraction process on and off;
• (3) structural proteins, which keep the thick and thin filaments in the proper alignment, give the myofibril elasticity and extensibility, and link the
• myofibrils to the sarcolemma and extracellular matrix.

• myosin
• and actin

• functions as a motor protein in all
• three types of muscle tissue.

• Motor proteins push or pull various cellular structures to achieve movement by
• converting the chemical energy in ATP to the mechanical energy of motion or the
• production of force

• generate force during contraction;
  regulatory proteins (troponin and
  tropomyosin) help switch contraction on and off.
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  

  (a)	A thick filament contains about 300 myosin molecules, one of which is shown enlarged. The myosin tails form the shaft of the thick filament, and the myosin heads project outward toward the surrounding thin filaments.
  (b)	Thin filaments contain actin, troponin, and tropomyosin.

• Actin and titin anchor into the Z disc.
• A bands contain myosin, actin, troponin, tropomyosin, and titin;
• I bands contain actin, troponin, tropomyosin, and titin