ANSC 30170 Muscle Tissue 1, 2 & 3

contractile, regulatory, structural

3 kinds of protein in muscle

myofiber

A single multinucleate muscle cell containing all the usual cell organelles plus many myofibrils

cramp

Abnormal contractions: Painful spasm

fasciculation

Abnormal contractions: involuntary brief twitch of a motor unit visible under the skin

spasm

Abnormal contractions: involuntary contraction of single muscle

Tic

Abnormal contractions: involuntary twitching of muscles (eyelid or facial)

tremor

Abnormal contractions: rhythmic, involuntary contractions of opposing muscle groups

striated, one central nucleus

Appearance of cardiac muscle

striated, multinucleated, fibers parallel

Appearance of skeletal muscle

skeletal muscle

Attached to bone, well developed cross striations, typically requires nervous stimulation, lacks anatomic and functional connections between individual fibers

myofibril

end to end arrays of identical sarcomeres

movement, holding in position, control organ volume, moving substances in body, heat production

functions of muscles (5)

purkinje fibers

modified myofibers that carry the impulse for contraction into the myocardium. Larger in diameter than myocytes. Can have two nuclei and relatively pale sarcoplasm

smooth

Muscle type: GI tract, uterus, eye, blood vessels. Functions in peristalsis, blood pressure, pupil size, erects hairs

cardiac

Muscle type: in heart, functions to pump blood continuously

skeletal

Muscle type: located in skeleton, functions in movement, heat and posture.

muscle

organized arrays of muscle fiber

contractility

property of muscle: activation of tension generating sites

Ca2+

Physiology of cardiac muscle: contracts without stimulation, contracts 75 times per min and needs lots of O2, extended contraction is due to slow ______ delivery

calmodulin

Physiology of smooth muscle: contraction starts slowly and lasts longer, ____ binds calcium ions in the cytosol. Actives the enzyme myosin light chain kinase

electrical excitability, contractility, extensibility, elasticity

Properties of Muscle tissue

electrical excitability

Property of muscle: respond to range of stimuli and produce action potentials

actin

Protein of Muscle. Thin filament protein. Has myosin binding site covered by tropomyosin in relaxed muscle

skeletal

Regeneration of muscle: ____muscle fibers cannot divide after 1st year, satellite cells and bone marrow produce some new cells, if too few fibrosis occurs

myocyte

Rod like, multinucleated cell composing muscles. Contains many myofibrils

Multiunit

Smooth muscle type: Fibres regulated individually. Innervated by a single nerve terminal. Never contract spontaneously

visceral, multiunit

Smooth muscle: two types

troponin and tropomyosin

regulatory proteins in muscle which turn contraction on and off

troponin

Thin myofilaments; ____ molecule at the end of each tropomyosin

tropomyosin

Thin myofilaments; ___molecules wrap around the actin chain

actin

Thin myofilaments; two chains that coil around each other

Fast Twitch (Type 2)

Type muscle fibers: Contract quickly and give sharp, powerful muscle contractions. Don't use oxygen. Suited to activities with bursts of strength and power. Tire quickly

Slow Twitch (Type 1)

Type muscle fibers: Take longer to contract, give long sustained muscle contractions. Not as powerful. Good oxygen supply. Suited to activities which require long term energy

slow twitch (type 1), fast twitch (type 2)

Types of Skeletal Muscle fibers

acetylcholine

WHat is released to begin muscle contraction

bladder, intestines, blood vessels

Where is smooth muscle found

smooth muscle

____ fibers cells can grow in size. New fibers can form from stem cells in blood vessel walls

cardiac

____muscle fibers cannot divide or regenerate, all healing is by fibrosis

nerve ending, neurotransmitter, muscle membrane, stored Ca2+, ATP, muscle proteins

BAsic structures in muscle contraction (6)

myosin light chain kinase

Calmodulin activates the enzyme____________ which facilitates myosin-actin binding and allows contraction to occur at a relatively slow rate

action potentials

Cardiac muscle contraction is initiated by

thin filament

Composed of a linear array of hundreds of globular, actin monomers in a double helical arrangement

thick filament

Composed of hundreds of long, contractile myosin molecules arranged in a staggered side by side complex.

fascia

Connective tissue components: communication system, transmission of force. Network of myofascia and CT

cardiac muscle

Differences of ____ from skeletal muscle: shorter, the striations not so obvious. sarcolemma is thinner. 1 nucleus. adjacent fibres branch but are linked to each other by muscle bridges. Spaces between individual fibres are filled with areolar connective tissue which contains blood capillaries to supply the tissue with the oxygen and nutrients

no striations, one central nucleus

appearance of smooth muscle

sarcomeres

Each myofibril in a myocyte contains many contractile units called

1 nerve, 1 artery, 2 veins

Each skeletal muscle is supplied by

cardiac muscle

Has cross striations. Functionally syncytial, also can be modulated via autonomic NS. Prolonged contractions. Can contract in absence of external innervation. Functionally connected to adjacent cells (Intercalated disks,Desmosomes)

gap junctions

In cardiac muscle contraction, electrical impulse is passed to adjacent cells via

Smooth muscle

Involuntary and non-striated¡ Slow but sustained contraction. Small tapered fibre with single centrally located nucleus. Lacks T-tubules, little SR for Ca2+ storage

myofibril

composed of cytoskeletal protein actin and contractile protein myosin

myosin and actin

contractile proteins in muscle

walls of hollow organs, sphincters

smooth muscle locations

rigor mortis

stage of muscular rigidity, 3-4 hours after death and lasts 24 hours. Ca2+ ions leak out of SR and myosin heads bind actin. Since ATP synthesis has ceased, crossbridges cannot detach from actin until proteolytic enzymes begin to digest the decomposing cells

sarcomere

the unit of contractile activity composed mainly of actin and myosin and extending from Z line to Z line in a myofibril

myosin

thick filaments are composed of the protein. Each molecule resembles two golf clubs twisted together, and the heads extend toward the thin filaments

actin, troponin, tropomyosin

thin filament proteins

cardiac, skeletal, smooth

three types of muscular tissue

I band

Sliding filament mechanism of contraction: thin filaments slide inward

Visceral (unitary)

Smooth muscle type: Few myocytes innervated. Cells connected by GAP jxns. Often autorhythmic. Contraction as a unit

ATP hydrolysis, attachment of myosin to actin to form crossbridges, power stroke, detachment of myosin from actin

4 steps of muscle contraction cycle

sarcomeres

Microscopic anatomy of smooth muscle: Thick and thin myofilaments lack ______

myosin head

Myosin: this has ATP binding sites, Actin binding sites, is hinged to thick myofilament allowing to swivel back and forth - the swiveling caused muscle contraction

M line

Sliding filament mechanism of contraction: Myosin cross bridges pull on thin filaments

Z discs

Sliding filament mechanism of contraction: ____come toward each other

sarcomeres

Sliding filament mechanism of contraction: ____shorten, muscle fiber shortens, muscle shortens

titin, myomesin, nebulin, dystrophin

Structural proteins which provide proper alignment, elasticity and extensibility