Suzanne D'Anna1 Muscular Tissue

Suzanne D'Anna2 Types of Muscle Tissue l skeletal l cardiac l smooth

Suzanne D'Anna3 Skeletal l attached to bones, skin, deep fascia, or other muscles l voluntary control l striated, alternating light and dark bands along length of myofibrils l many nuclei l Functions: - movement - posture - respiration

Suzanne D'Anna4 Skeletal Muscle Nuclei Striation

Suzanne D'Anna5 Cardiac l located only in the heart l striated, single nucleus, branched fibers with intercalated discs l involuntary control by autonomic nervous system l regulation of heart rate is primarily due to hormones and neurotransmitters l no regeneration capability l propels blood through blood vessels

Suzanne D'Anna6 Cardiac Muscle intercalated disc

Suzanne D'Anna7 Smooth l located in hollow organs, skin attached to hair follicles, etc. l no striations, single nucleus, spindle- shaped fibers l involuntary control by autonomic nervous system l some regeneration

Suzanne D'Anna8 Functions of Smooth Muscles l mix and propel food though GI tract l regulate flow of blood by changing diameter of lumen l contraction of urinary bladder, gallbladder, and spleen, expels urine, bile and blood l control sphincter muscles l control muscles of eye l contraction of arrector pili muscles

Suzanne D'Anna9 Types of Smooth Muscles

Suzanne D'Anna10 Multiunit Smooth l muscle fibers are not well organized l occur as separate fibers rather than sheets l found in irises of eye, walls of blood vessels

Suzanne D'Anna11 Visceral Smooth l composed of sheets of spindle-shaped cells l in contact with one another l more common type l found in hollow visceral organs l capable of stimulating each other l display rhythmicity due to self-exciting fibers - responsible for peristalsis

Suzanne D'Anna12 Peristalsis l wavelike motion l occurs in various tubular organs l helps force contents of these organs along their lengths

Suzanne D'Anna13 Contraction of Smooth Muscles l acetylcholine and norepinephrine l also affected by hormones l slower to contract - slower to relax l can maintain a forceful contraction longer than skeletal with same amount of ATP l can change length without changing tautness

Suzanne D'Anna14 Smooth Muscle

Suzanne D'Anna15 Muscle Fibers l many muscle fibers are enclosed in a delicate connective tissue sheath called endomysium l several sheathed fibers are wrapped in perimysium in bundles called fascicles ( fibers)

Suzanne D'Anna16 Muscle Fibers (cont.) l many fascicles are joined together by even tougher covering called epimysium l fascia covers entire muscles which lead into tendons which attach to bones

Suzanne D'Anna17 Individual Muscle Fiber (single cell) l sarcolemma - plasma membrane covering of muscle cell l sarcoplasm - cytoplasm of a skeletal muscle cell

Suzanne D'Anna18 Individual Muscle Fiber (cont.) l sarcoplasmic reticulum - network of membranous channels - within sarcoplasm (corresponds to endoplasmic reticulum) - surrounds each myofibril - channels run parallel to myofibril - stores calcium which is necessary for muscle contraction

Suzanne D'Anna19 Individual Muscle Fiber (cont.) l transverse tubules - fingerlike inward invaginations or channels of sarcolemma - extend from membrane and pass through the fiber - open to outside of the muscle fiber - contain extracellular fluid - carry action potentials to sarcoplasmic reticulum

Suzanne D'Anna20 Individual Muscle Fiber (cont.) l cisternae - enlarged portions of sarcoplasmic reticulum - lie on either side of transverse tubules - near region where actin and myosin overlap

Suzanne D'Anna21 Individual Muscle Fiber (cont.) l myofibrils - long ribbon-like organelles - lie parallel to one another l myofilaments - thread-like structures within myofibrils (contain two types of protein filaments) l actin (thin & light) and myocin (thick & dark)

Suzanne D'Anna22 Actin and Myosin l appear as light (thin) and dark (thick) bands l arrangement of these fibers produces the characteristic striations of a skeletal muscle fiber l slide past each other causing muscle cells to contract

Suzanne D'Anna23 Myosin l located within the dark portions of the striations (A bands)

Suzanne D'Anna24 Actin l located primarily within light areas (I bands) l during muscle contraction actin filaments slide farther into A bands l attached to the Z lines at end of I bands l Z lines extend across muscle fiber enabling adjacent myofibrils to lie side by side l segment between two Z lines is called a sarcomere

Suzanne D'Anna25 Sarcomeres l repeating units composed of filaments inside myofibrils l do not extend the entire length of the muscle fiber

Suzanne D'Anna26 Muscle Activity

Suzanne D'Anna27 Characteristics of Muscle Tissue l excitability l contractility l extensibility l elasticity

Suzanne D'Anna28 Excitability (irritability) l ability to respond to stimuli l generate action potentials or impulses l stimuli that initiate action potentials in muscles are neurotransmitters l neurotransmitters are released by axon terminals of neurons

Suzanne D'Anna29 Contractility l ability to contract and shorten to generate a force l muscles contract in response to action potentials

Suzanne D'Anna30 Extensibility l ability to be stretched or extended when pulled l with pairs of skeletal muscles - one muscle is contracted while the opposing one is usually stretched

Suzanne D'Anna31 Elasticity l ability to return to original shape after contraction or extension