Muscular Tissue Suzanne DAnna 1 Types of Muscle

Muscular Tissue Suzanne D'Anna 1

Types of Muscle Tissue skeletal l cardiac l smooth l Suzanne D'Anna 2

Skeletal 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 l Suzanne D'Anna 3

Skeletal Muscle Nuclei Striation Suzanne D'Anna 4

Cardiac 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 l Suzanne D'Anna 5

Cardiac Muscle intercalated disc Suzanne D'Anna 6

Smooth located in hollow organs, skin attached to hair follicles, etc. l no striations, single nucleus, spindleshaped fibers l involuntary control by autonomic nervous system l some regeneration l Suzanne D'Anna 7

Functions of Smooth Muscles 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 l Suzanne D'Anna 8

Types of Smooth Muscles Suzanne D'Anna 9

Multiunit Smooth muscle fibers are not well organized l occur as separate fibers rather than sheets l found in irises of eye, walls of blood vessels l Suzanne D'Anna 10

Visceral Smooth 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 l Suzanne D'Anna 11

Peristalsis wavelike motion l occurs in various tubular organs l helps force contents of these organs along their lengths l Suzanne D'Anna 12

Contraction of Smooth Muscles 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 l Suzanne D'Anna 13

Smooth Muscle Suzanne D'Anna 14

Muscle Fibers 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 (10 -100 fibers) l Suzanne D'Anna 15

Muscle Fibers (cont. ) many fascicles are joined together by even tougher covering called epimysium l fascia covers entire muscles which lead into tendons which attach to bones l Suzanne D'Anna 16

Individual Muscle Fiber (single cell) sarcolemma - plasma membrane covering of muscle cell l sarcoplasm - cytoplasm of a skeletal muscle cell l Suzanne D'Anna 17

Individual Muscle Fiber l (cont. ) 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'Anna 18

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'Anna 19

Individual Muscle Fiber l (cont. ) cisternae - enlarged portions of sarcoplasmic reticulum - lie on either side of transverse tubules - near region where actin and myosin overlap Suzanne D'Anna 20

Individual Muscle Fiber (cont. ) 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) l Suzanne D'Anna 21

Actin and Myosin 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 l Suzanne D'Anna 22

Myosin l located within the dark portions of the striations (A bands) Suzanne D'Anna 23

Actin 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 l Suzanne D'Anna 24

Sarcomeres repeating units composed of filaments inside myofibrils l do not extend the entire length of the muscle fiber l Suzanne D'Anna 25

Muscle Activity Suzanne D'Anna 26

Characteristics of Muscle Tissue excitability l contractility l extensibility l elasticity l Suzanne D'Anna 27

Excitability (irritability) 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 l Suzanne D'Anna 28

Contractility ability to contract and shorten to generate a force l muscles contract in response to action potentials l Suzanne D'Anna 29

Extensibility 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 l Suzanne D'Anna 30

Elasticity l ability to return to original shape after contraction or extension Suzanne D'Anna 31