Chapter 10: Muscle Tissue

Myofibrils built from 3 kinds of proteins

-contractile proteins -regulatory proteins -structural proteins

functions of muscular tissue

-producing body movements -stabilizing body positions -storing and moving substances within the body -generating heat

The elastic components of muscle consist of which elements?

-titin molecules -connective tissue around the muscle fibers -tendons that attach muscle to bone

contraction period

Ca2+ binds to troponin, myosin-binding sites on tin are exposed, and cross-bridges form

relaxation phase

Ca2+ is actively transported back into the SR, myosin-binding sites are covered by tropomyosin, myosin heads detach from actin, tension in the fiber decreases

tendons

Connect muscle to bone

muscular atrophy

a decrease in the size of individual muscle fibers as a result of progressive loss of myofibrils

myopathy

a disease or disorder of the skeletal muscle tissue itself

muscular dystrophy

a group of inherited muscle-destroying diseases that causes progressive degeneration of skeletal muscle fibers

perimysium

a layer of dense irregular connective tissue, surrounds groups of 10 to 100 or more muscle fibers separating them into bundles or muscle fascicles

I band

a lighter area that contains the rest of the thin filament but no thick filaments

nebulin

a long, non-elastic protein that wraps around the entire length of the thin filament during development

somatic motor neuron

a neuron that stimulates skeletal muscle fibers to contract

synapse

a region where communication occurs between two neurons, or between a neuron and a target cell

muscle tone

a small amount of tautness or tension in muscle due to weak, involuntary contraction of its motor units

motor unit

a somatic motor neuron plus all the skeletal muscle fibers it stimulates

fibrillation

a spontaneous contraction of a single muscle fiber that is not visible under the skin but can be recorded by electromyography

fused tetanus

a sustained contraction in which individual twitches cannot be detected

Electromyography (EMG)

a thin needle, recording device, is placed through the skin into a muscle. the needed is connected by a wire to a screen

interval traning

a workout regiment that incorporates both types of training

dystrophin

Links thin filaments to proteins of sarcolemma to integral membrane proteins of the sarcolemma, which are attached to proteins in the connective tissue extracellular matrix that surrounds muscle fibers

anaerobic training

activities stimulate synthesis of muscle proteins and result in increased muscle size

rigor mortis

after death, cellular membranes become leaky

exercise-induced muscle damage

after intense exercise, damage can include torn sarcolemmas, damaged myofibrils, distributed Z discs

fasciculation

an involuntary, brief twitch of an entire motor unit that is visible under the skin

slow oxidative fibers

appear dark red due to large amounts of myoglobin and many blood capillaries

detachment of myosin from actin

at the end of the power stroke, the cross-bridge remains attached until it binds to another ATP molecule

M line

at the middle of the sarcomere

myasthenia gravis

autoimmune disease that causes chronic, progressive damage of the NMJ

sarcomeres

basic functional unit of a myofibril

recovery oxygen uptake

better term for oxygen debt after exercise

Cl-actinin

bind to each actin molecule of the thin filament and to the titin

twitch contraction

brief contraction of all muscle fibers in a motor unit in response to a single action potential

aerobic training

builds endurance for prolonged activities

central fatigue

caused by changes in the central nervous system

H band

center of each A band that contains thick filaments but no thin filaments

spastic paralysis

certain disorders of the nervous system and electrolyte disturbances in which partial paralysis in which the muscle exhibits spasticity

fibromyaglia

chronic, painful, nonarticular rheumatic disorder that affects the fibrous connective tissue components of muscles, tendons, and ligaments

thin filaments

composed of actin

thick filaments

composed of myosin

hypotonia

decreased or lost muscle tone

junctional folds

deep grooves in the motor end plate that provide a large surface area for ACh

electrodiagnostic medicine

diagnosis of neuromuscular disorders

terminal cisterns

dilated end sacs of the sarcoplasmic reticulum that butt against the T tubules from both sides

attachment of myosin to actin

energized myosin head attaches to the myosin-binding site on actin and releases the previously hydrolyzed phosphate group

hypertrophy

enlargement of existing cells

A band

extends the entire length of the thick filament

sarcoplasmic reticulum

fluid-filled system of membranous sacs that encircle each myofibril

myomesin

form the M line, binds to titan and connects adjacent thick filaments to one another

cardiac muscle

forms most of the walls of the heart -involuntary

dermatomal mesenchyme

forms the connective tissues,, including the dermis of the skin and subcutaneous tissue

visceral smooth muscle tissue

found in skin and tubular arrangements that form part of the walls of small arteries, veins, and hollow organs: stomach, intestines, uterus, urinary bladder.

contractile proteins

generate force during contraction

thermogenesis

generation of heat, maintains body temperature

sclerotome

gives rise to the vertebrae and ribs

muscle fibers (myocytes)

has connective tissue surrounding muscle fibers, blood vessels, and nerves

regulatory proteins

help switch the contraction process on and off

hyperplasia

increase in the number of fibers

spasticity

increased muscle tone associated with an increase in tendon reflexes and pathological reflexes

rigidity

increased muscle tone where reflexes are not affected

hypertonia

increased muscle tone, expressed in spasticity and rigidity

Multi-unit smooth muscle tissue

individual fibers with its own motor neuron terminal and few gap junctions between neighboring fibers

structural proteins

keep the thick and thin filaments in proper alignment

smooth muscle tissue

located in the walls of hollow internal structures -involuntary

flaccid paralysis

loss of muscle tone due to disruptions in the balance of electrolytes here a loss of muscle tone, loss or reduction of tendon reflexes, atrophy and degeneration of muscles

fast glycolytic fibers

low myoglobin content, few blood capillaries, appear more white in color

nerve conduction velocity (NCV) tests

measure the speed of nerve impulses conducted through nerves outside the brain and spinal cord

synaptic vesicles

membrane enclosed sacs

where do muscles come from?

mesoderm

skeletal muscle tissue

most skeletal muscles move the bones of the skeleton

muscle proteins

muscle contains dozens of structural proteins to help with alignment, stability, elasticity, and extensibility of myofibrils

muscular hypertrophy

muscle growth after birth that occurs by enlargement of existing muscle fibers

ATP hydrolysis

myosin head includes an ATP-binding site that functions as an ATPase

power stroke

myosin head pivots, changing position as it pulls the thin filament past the thick filament toward the center of the sarcomere, generating tension

acetylcholine (ACh)

neurotransmitter in the synaptic vesicles that is released at the NMJ

epimysium

outer layer, encircling the entire muscle, dense irregular connective tissue

cramp

painful spasmodic contraction

endomysium

penetrates the interior of each fascicle and separates individual muscle fibers from one another, mostly reticular fibers

sarcolemma

plasma membrane of a muscle fiber, thousands of tiny tube shaped invaginations of the sarcolemma, T tubules, tunnel in from the surface toward the center of each muscle fiber

neuromuscular disease

problems with somatic motor neurons, neuromuscular junctions, and muscle fibers

motor proteins

pull various cellular structures to achieve movement by ATP

glycolysis

quickly breaks down each glucose molecule into two pyruvic acid

myogram

record of a smooth twitch

myoglobin

red-colored protein, only found in muscle, binds oxygen when needed by the mitochondria for ATP production

motor end plates

region of the sarcolemma opposite the synaptic end bulbs

tropomyosin and troponin

regulatory proteins that are part of the thin filaments

the contraction cycle

repeats as the myosin ATPase hydrolyzes newly bound molecules of ATP

tremor

rhythmic, involuntary, purposeless contraction that produces quivering or shaking movements

z disc

separates one sarcomere from the next, passes through the center of each I band

synaptic cleft

separates two cells by a small gap

myotome

skeletal muscles of the trunk and limbs

filaments

smaller protein structures within the myofibrils

tic

spasmodic twitching made involuntary by muscles that are ordinarily under voluntary control

delayed onset muscle soreness (doms)

stiffness, tenderness and swelling -from 12-48 hours. after a period of strenuous exercise

wave summation

stiumuli arriving at different times causing a larger contraction

aponeurosis

strong sheet of tissue that acts as a tendon to attach muscles to bone

connective tissue components

subcutaneous tissue and fascia

spasm

sudden involuntary contraction of a single muscle in a large group of muscles

unfused tetanus

sustained but wavering contraction

anabolic steroids

synthetic variations of testosterone

isotonic contraction

tension developed in the muscle remains almost constant while the muscle changes its length

isometric contraction

tension generated is not enough to exceed the resistance of the object being moved, the muscle doesn't change its length

concentric isotonic contractions

tension is great enough to overcome the resistance of the object to be moved

elasticity

the ability of muscular tissue to return to its original length and shape after contraction of extension

contractility

the ability to contract forcefully when stimulated by a nerve impulse

oxygen debt

the added oxygen, over and above the resting oxygen consumption that the body needs after exercise

latent period

the brief delay between the application of the stimulus and the beginning of a contraction

neurotransmitter

the chemical messenger that allows one cell to communicate with the next cell

myofibrils

the contractile organelles of skeletal muscle, gives skeletal muscle their striated appearance

sarcoplasm

the cytoplasm of a muscle fiber that contains a large amount of glycogen

axon terminal

the end of the motor neuron

muscle fatigue

the inability of a muscle to maintain force of contraction after prolonged activity

fast oxidative-glycolytic fibers

the largest fibers

synaptic end bulbs

the neural part of the NMJ

Motor Unit Requirement

the number of active motor units increases

strength training

the process of exercising with progressively heavier resistance for the purpose of strengthening the MSK system

neuromuscular junction (NMJ)

the synapse between a somatic motor neuron and a skeletal muscle fiber

eccentric isotonic contraction

the tension exerted by the myosin cross bridges resists movement of a load and slows the lengthening process

myosin

thick filaments and function as motor protein in all three types of muscle tissue

titin

third most plentiful protein in skeletal muscle

refractory period

when a muscle temporarily loses their excitability and cannot respond for a time

frequency of stimulation

when a second stimulus occurs after the refractory period, but before the skeletal muscle has relaxed, the second contraction will actually be stronger than the first

aerobic respiration

when enough oxygen is present, pyruvic acid is formed by glycolysis entering the mitochondria to undergo this process that produce ATP, carbon dioxide, water and heat -Krebs cycle and the electron transport chain

anaerobic glycolysis

when muscle activity continues and the supply of creatine phosphate is depleted, we use glucose in muscle to make ATP

acetylcholine receptors

within the motor end plate, where transmembrane proteins with ACh specifically bind

sliding filament mechanism

The explanation of how thick and thin filaments slide relative to one another during striated muscle contraction to decrease sarcomere length

extensibility

ability of muscular tissue to stretch, within limits, without being damaged

electrical excitability

ability to respond to certain stimuli by producing electrical signals (action potential)