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)