A&P Chapter 10 Flashcards
Functions of muscular tissue
- Producing body movements
- Stabilizing body position
- Storing and moving substances within the body
- Generating heat
Properties of muscular tissue
- Electrical excitability (action potentials/impulses)
- Contractility
- Extensibility
- Elasticity
Epimysium
Outermost layer of dense, irregular connective tissue, encircling the entire muscle
Perimysium
Dense, irregular connective tissue that surrounds groups of 10 to 100 or more muscle fibers
Fascicles
Bundles of 10 to 100 or more muscle fibers
Endomysium
Penetrates the interior of each fascicle and separates individual muscle fibers from one another. Mostly reticular fibers.
Aponeurosis
When the connective tissue elements extend as a broad, flat sheet
Somatic motor neurons
Neurons that stimulate skeletal muscle to contract
Sarcolemma
Plasma membrane of a muscle cell
Transverse (T) tubules
Tiny invaginations of the sarcolemma that tunnel in from the surface toward the center of each muscle fiber.
Sarcoplasm
Cytoplasm of a muscle fiber (within the sarcolemma)
Myoglobin
Red-colored protein found only in muscle. Binds oxygen molecules that diffuse into muscle fibers from interstitial fluid.
Myofibrils
Contractile organelles of skeletal muscle. Their prominent striations make the entire skeletal muscle appear striped (striated).
Sarcoplasmic Reticulum (SR)
Fluid-filled system of membranous sacs that encircle each myofibril. Similar to Smooth ER in non-muscular cells.
Terminal cisterns
Dilated end sacs of the SR.
Triad
Formed by a transverse tubule and the two terminal cisterns on either side of it.
Filaments or Myofilaments
Smaller protein structures within myofibrils
Sarcomeres
Compartments that hold the filaments inside a myofibril. The basic functional units of a myofibril
Z discs
Narrow, plate-shaped regions of dense protein material that separate one sarcomere from the next.
A band
Darker middle part of the sarcomere. Extends the entire length of the thick filaments.
I band
Lighter, less dense area that contains the rest of thin filaments but no thick filaments. A Z disc passes through the center of each I band.
H zone
In the center of each A band. Contains thick but not thin filaments.
M line
Formed by supporting proteins that hold the thick filaments together at the center of the H zone. At the middle of the sarcomere.
Three kinds of proteins that build myofibrils
- Contractile: generate force during contraction
- Regulatory: help switch the contraction process on and off
- Structural: Keep the thick and thin filaments in the proper alignment, give the myofibril elasticity and extensibility, and link the myofibrils to the sarcolemma and extracellular matrix
Two contractile proteins in muscle
Myosin and actin
Myosin
Main component of thick filaments and functions as a motor protein in all three types of muscle tissue.
Actin
Main component of thin filaments which are anchored to Z discs. Individual actin molecules join to form an actin filament that is twisted into a helix.
Titin
Third most plentiful protein in skeletal muscle.
Actinin
molecules which bind to actin molecules of the thin filament and to titin.
Myomesin
Protein molecules that form the M line. Bind to titian and connect adjacent thick filaments to one another.
Nebulin
A long, nonelastic protein wrapped around the entire length of each thin filament. Helps anchor thin filaments to the Z discs and regulates the length of thin filaments during development.
Dystrophin
Links thin filaments of the sarcomere to integral membrane proteins of the sarcolemma, which are attached in turn to proteins in the connective tissue extracellular matrix that surrounds muscle fibers.
Contraction cycle
Repeating sequence of events that causes the filaments to slide
Four steps of contraction cycle
- ATP hydrolysis: Myosin heads hydrolyze ATP and become reoriented and energized.
- Attachment of myosin to actin to form cross-bridges.
- Power stroke: Myosin cross-bridges rotate toward center of sarcomere.
- Detachment of myosin from actin.
Neuromuscular Junction (NMJ)
The synapse between two neurons, or between a neuron and a target cell - in this case, between a somatic motor neuron and a muscle fiber.
Synaptic cleft
Small gap that separates the two cells
Axon terminal
End of the motor neuron.
Synaptic end bulbs
Neural part of the NMJ
Synaptic vesicles
Membrane-enclosed sacs suspended in the cytosol within each synaptic end bulb
Acetylcholine (ACh)
Molecules of the neurotransmitter inside each synaptic vesicle released at the NMJ.
Motor end plate
Region of the sarcolemma opposite the synaptic end bulbs
Acetylcholine receptors
Integral transmembrane proteins to which ACh specifically binds
Junctional folds
Deep grooves in the motor end plate that provide a large surface area for ACh
Nerve impulse (nerve action potential) elicits a muscle action in the following way:
- Release of acetylcholine
- Activation of ACh receptors
- Production of muscle action potential
- Termination of ACh activity
Three ways muscle fibers produce ATP
- From creatine phosphate
- By anaerobic cellular respiration
- By aerobic cellular respiration
Creatine phosphate
An energy rich molecule that is found in muscle fibers.
Creatine
Small, amino acid-like molecule that is synthesized in the liver, kidneys, and pancreas and then transported to muscle fibers.
Anaerobic cellular respiration
A series of ATP-producing reactions that do not require oxygen
Aerobic cellular respiration
A series of ATP-producing reactions that require oxygen
Muscle fatigue
The inability of a muscle to maintain force of contraction after prolonged activity
Oxygen debt/Recovery oxygen uptake
Added oxygen, over and above the resting oxygen consumption, that is taken into the body after exercise.
Motor unit
A somatic motor neuron plus all the skeletal muscle fibers it stimulates
Twitch contraction
Brief contraction of all the muscle fibers in a motor unit in response to a single action potential in its motor neuron
Myogram
Record of a muscle contraction
