Properties of Muscle Tissue Excitability respond to stimuli

Properties of Muscle Tissue Excitability: respond to stimuli Conductivity: propagate signals over membrane Contractility: shorten and generate force Extensibility: stretch without damage Elasticity: return to their original length after being shortened or stretched

Functions of Muscular Tissue – Body Movements – – • Walking and running Stabilize Body Positions • Posture Support Soft Tissue Move Substances Within the Body • Blood (cardiac m. ) • Digestive tract (smooth m. ; sphincters and oropharynx skeletal m. ) Generate heat • Shivering: contraction of muscle produces heat (ATP)

Organization of Muscle Epimysium The outermost layer Separates 10 -100 muscle fibers into bundles called fascicles Perimysium Surrounds numerous bundles of fascicles Endomysium Separates individual muscle fibers (cells) from one another Epi-, Peri-, Endomysium converge into tendon CT that attaches a muscle to periosteum of bone Aponeurosis = Broad, flattened tendon

Functional Organization Muscle Fascicle Myofiber Myofibril Sarcomere Myofilaments

Sarcomere From Z to Z is a functional unit: the sarcomere

Motor Neuron Motor neuron Neuromuscular junction Skeletal muscle cells Motor unit

Neuromuscular Junction (Motor End Plate) Each myofiber receives a single axon terminal Neuromuscular junction (a. k. a. motor end plate) Specialized region of sarcolemma Neurotransmitter: Acetylcholine

SR and T Tubules: Excitation Contraction Coupling Sarcoplasmic reticulum (SR) Terminal cisternae Ca 2+ is normally sequestered in the SR; released by stimulation from the motor end plate transferred from T Tubules Indentations of sarcolemma to transfer depolarization from motor end plate Triads

Nerve and Blood Supply Nerves ▪ Neurons stimulate skeletal muscle to contract ▪ Neuromuscular junction ▪ The axon of a somatic motor neuron typically branches many times ▪ Each branch extends to a different skeletal muscle fiber Blood Supply ▪ Each muscle fiber is in close contact with one or more capillaries

Organization of Muscle Fibers Power, range of movement, and speed of contraction all vary with the arrangement of fascicles in a muscle Four different arrangements Parallel Convergent Pennate Circular

Actions of Muscles Review movement of joints Prime mover (agonist) Contraction of the muscle is the main reason for producing a movement Synergist Assists prime mover Antagonist Act in opposition to the prime mover Fixator Immobilize origin of prime mover

Muscle Nomenclature Directions: Rectus (straight), Transversus (across), Oblique (at an angle) Number of heads: Biceps (2 origins), Triceps (3 origins), Quadriceps (4 origins) Shapes: trapezoid, deltoid, rhomboid, orbicular Length: Longus or longissimus (long), teres (long and round), brevis (short) Size: magnus (big), major (bigger), maximus (biggest), minor (smaller), minimus (smallest) Externus (superficialis) vs. Internus (profundus) Extrinsic (outside) vs. Intrinsic (inside) Origins and insertions (first name is origin, second insertion) Primary function: flexor, extensor, retractor