BIO 219: LAB 13.1 - Muscle Tissue

contractile; actively shorten and produce tension.

excitable; action potentials; activate contraction of the cell

movement, support, circulation of blood and heat generation

skeletal muscle, cardiac muscle and smooth muscle

• "voluntary" muscles associated with the skeletal system
• composed of long muscle fibers which are multi-nucleated cells with a high organized structure
• striated

• forms the heart muscle or myocardium
• straited
• each cell has a single nucleus and the cells branch to form connections with adjacent cardiac muscle cells
• connected by intercalated discs
• small in diameter than skeletal muscle

• involuntary muscle tissue of internal organs and blood vessels
• composed of spindle-shaped cells
• non-striated because no sarcomeres are present
• located in the walls of the digestive, respiratory, urinary, and reproductive tracts
• often arranged in distinct circular and longitudinal layers
• smooth muscle in the walls of blood vessels plays a major role in controlling blood flow to body organs and tissues

Skeletal muscle
• muscle fibers (multinucleated cells)
• striations
• nuclei located at the periphery of the cells

Cardiac muscle
• single nucleus, centrally located
• branching connections to adjacent cells
• intercalated discs
• striations

Smooth muscle
• small diameter
• spindle shaped
• single, centrally located nucleus
• circular layer (small intestine)
• longitudinal layer (small intestine)

bundles of muscle cells

multinucleated, elongated cell

bundle of overlapping myofilaments

protein filaments (thick & thin)

cell membrane of muscle cell

cytoplasm of the muscle fiber

narrow tubes continuous with sarcolemma that extend onto sarcoplasm and
• filled with extracellular fluid
• transmit action potentials through the cell to allow entire muscle fibers to contract simultaneously

helps transmit action potential to myofibril, forms expanded chambers
• terminal cisternae are attached to T-tubules

thick filaments, subunits twisted around filament

thin filaments, 2 twisted strands of globular polypeptide subunits

cell membrane of the muscle cell

cytoplasm of muscle fiber

narrow tubes continuous with sarcolemma that extend into sarcoplasm
• filled with extracellular fluid
• transmits action potentials through cell
• allow entire muscle fiber to contract simultaneously

helps transmit action potential to myofibril, forms expanded chambers, terminal cisternae are attached to T-tubules

thick filaments, subunits are twisted around filament

thin filaments, 2 twisted strands of globular polypeptide subunits and actin form long actin filaments F actin

dark, thick filament
• during muscle contraction, stays the same

light, thin filaments
• during muscle contraction - shortens

thick filaments, during contraction - shortens around M line

center of A band, connect with thick filaments

during contraction - they move closer together

strands of elastic protein
function: stabilize the filaments, recoils after stretching during muscle contraction

when myosin binds to active site on thin filament

double stranded, covers active sites on actin to prevent actin-myosin interaction

globular proteins, binds to tropomyosin to G actin controlled by Ca2+ via a Ca2+ binding site

tail: binds to other myosin molecules head: made of 2 globular protein subunits projects forward nearest the thin filament

free myosin head hydrolyzes ATP into ADP + Pi

a motor neuron and all muscle fibers it innervates

• contractile units of muscle
• structural units of myofibrils
• form visible patters within myofibrils

made up of protein myosin

made up of protein actin

where thick and thin filaments overlap

concentrated Ca2+ (via ion pumps)
• stored Ca2+ is released into sarcomeres to being muscle contraction