Lab #10 Microscopic Anatomy of Skeletal Muscle

Key terms

3 Types of muscle tissue

Skeletal, Cardiac, and Smooth

Prefixes for muscle

-myo, -mys, and -sarco

Excitability

(responsiveness or irritability): ability to receive and respond to stimuli

Contractability

Ability to shorten forcibly when stimulated

Extensibility

Ability to be stretched

Elasticity

Ability to recoil to resting length

4 important muscle functions

Movement of bones or fluids, maintaining posture and body position, stabilizing joints, and heat generation

Epimysium

Connective tissue surrounding entire muscle

Perimysium

Connective tissue surrounding fascicles

Fascicle

Groups of muscle fibers

Endomysium

Connective tissue surrounding each muscle fiber

Insertion

Movable bone

Origin

Immovable or less movable bone

Steps to muscle contraction (1/9)

Nerve impulse reaches Axon

Steps to muscle contraction (2/9)

ACH is released from the axon and travels across the synaptic cleft

Steps to muscle contraction (3/9)

ACH binds to the Sarcolemma of the muscle cell

Steps to muscle contraction (4/9)

Causes Na/K pumps to activate causing a change in membrane potential (charge)

Steps to muscle contraction (5/9)

Action potential is reached

Steps to muscle contraction (6/9)

When the charge reaches the threshold/action potential, the sarcoplasmic reticulum floods the cell with Ca

Steps to muscle contraction (7/9)

Ca binds to troponin

Steps to muscle contraction (8/9)

Troponin changes shape and moves tripomyosin off of actin’s active sites

Steps to muscle contraction (9/9)

Myosin can now create cross bridges with acting and a contraction occurs

How long is a muscle fiber?

10 to 100 µm in diameter; up to 30 cm long

Sarcolemma

Plasma membrane

Sarcoplasmic reticulum

ER that stores and releases calcium

Myofibrils

Long filamentous organelle made of myofilaments

Myofilaments

Myosin and Actin proteins

Sarcomeres

Contractile units (Contain actin and myosin)

Actin myofilaments

Thin filaments

Myosin myofilaments

thick filaments

Tropomyosin and Troponin

Regulatory proteins bound to actin

Sarcoplasmic Reticulum

Network of smooth ER surrounding each myofibril, stores and releases Ca²+

Cross bridges

When myosin heads bind to actin

Synaptic cleft

Seperates the axon terminal and muscle fiber by a gel filled space

Depolarization

Na+ influx decreases the membrane voltage

Repolarization

Restoring electrical conditions