muscle tissue Flashcards
What are the 3 types of muscle tissue?
Skeletal, cardiac, smooth
Contractile tissues
muscle tissues are contractile tissues, they generate tension and movement
Skeletal muscle tissue
Most are attached to the bones of the skeleton by tendons, called muscle fibers, perform voluntary movements, multinucleate, and they are striated
Multinucleate
Each cell has more than one nucleus
Striations
Alternating light and dark bands that can be seen when muscle tissue is examined with a microscope
What are some functions of the skeletal muscle tissue?
Producing voluntary body movements, maintaining posture, breathing movements, and generating heat
Cardiac muscle tissue
Found only in the walls of the heart, responsible for the heartbeat, uninucleate, striated, action is involuntary, has intercalated discs
Uninucleate
One nucleus per muscle fiber
Involuntary actions
Contraction and relaxation is not consciously controlled
Autohythmicity
The built-in rhythm of the heart created by the pacemaker
Intercalated discs
Interlocking attachment sites between cardiac muscle fibers
Desmosomes
Cell junctions that firmly hold cardiac muscle cells together
Gap junction
Protein channels for electrochemical signals to pass from cell to cell stimulate the heartbeat
Smooth muscle tissue
Located on the walls of hollow internal structures, non-striated, spindle-shaped muscle fibers with one nucleus, involuntary control, move substances within the body, contraction of this muscle tissue can cause constriction and dilation
Peristalsis
the smooth muscle moves food through the gastrointestinal tract and produces a wave-like motion
Contraction of smooth muscles
causes constriction of blood vessels, which reduces blood flow and increases blood pressure
Relaxation of smooth muscle
walls dilate blood vessels, which increases blood flow and lowers blood pressure
Excitability
Ability to respond to nervous stimulation or electrical stimulation
Contractility
Ability to contract forcefully when stimulated. If enough tension is generated, the muscle tissue shortens and movement occurs
Extensibility
Ability to stretch without tearing
Elasticity
Ability to return to the muscle tissues’ original length after stretching or after contracting
What tissue types do skeletal muscles contain?
They contain all 4 primary tissue types.
Tendon
is a cord of dense regular connective tissue that attaches a muscle to the periosteum of the bone
Aponeurosis
is a broad, flattened tendon
Areolar connective tissue
Surrounds and protects individual muscle fibers
Dense irregular connective tissue
Surrounds bundles of muscle fibers called fascicles
Fascicle
A bundle of 10-100 muscle fibers within a muscle. Are held together by dense irregular connective tissue. Give muscle its “grain”
Deep fascia
Refers to the sheet of dense irregular connective tissue that surrounds groups of muscles and separates the muscles into functional compartments
Embryonic development
100 or more embryonic stem cells called myoblasts fuse to form a muscle fiber, making the muscle fiber multinucleate
Satellite cells
Adult stem cells that develop from myoblasts and remain in mature muscle tissue
Fibrosis
Replacing muscle tissue with scar tissue
Hypertrophy
an enlargement of existing muscle fibers that result in muscle growth
Sarcolemma
the plasma membrane of a muscle fiber
Transverse tubules
invaginations of the sarcolemma, tunnel in from the plasma membrane toward the center of the muscle fiber.
Sarcoplasm
is the cytoplasm of the muscle fiber
The sarcoplasmic reticulum
specialized smooth endoplasmic reticulum that encircles each myofibril
Mitochondria
organelles that use nutrients and O2 to produce ATP energy for the cell. Several mitochondria lie close to the myofibrils and provide ATP energy for muscle contraction
Sarcomer
the basic functional unit of a myofibril, extends from Z disc to Z disc
Z discs
protein structures that separate one sarcomere from its neighboring sarcomeres on either side
A band
the darker middle part of the sarcomere – thick filaments extend across the A bands
H zone
the center of each a band, contains only thick filaments and no thin filaments
M line
runs down the center of the H zone, the M line contains supporting proteins that hold the thick filaments in position in the H zone
I bands
lighter bands on each end of the sarcomere contains only thin filaments
Structural proteins
align the thick and thin filaments properly within a sarcomere, provide elasticity and extensibility for the muscle fiber, attach the myofibrils to the sarcolemma and connective tissue
Contractile proteins
generate force during contraction and create movement
Regulatory proteins
Switch the contraction process on and off
Titin protein
connects a Z disc with an M line, titin can stretch to 4 times its resting length, and then recoil back to normal, titin accounts for much of the extensibility and elasticity of myofibrils and muscle tissue
Dystrophin
a structural protein that attaches the myofibril to the sarcolemma and to the connective tissue around the cell
Muscular dystrophy
s recessive X-linked genetic disorder in which there is little or no dystrophin protein produced in the muscle fibers
Thick filaments
made of myosin protein
Thin filaments
Consists of primarily actin protein
Actin
Provides myosin-binding sites where myosin heads can attach
somatic motor neurons
nerve cells that stimulate skeletal muscle fibers to contract
Neuromuscular junction
a synapse between a motor neuron and a muscle fiber
synapse
a junction between neurons or between neurons and muscle fibers where a chemical signal is transmitted from neuron to neuron, or from motor neuron to a muscle fiber
Axons
motor neurons branch into many axon terminals, which form neuromuscular junctions with individual muscle fibers
Synaptic end bulb
the enlarged tip of the axon terminal of the neuron
The synaptic cleft
a fluid-filled gap in a neuromuscular junction between the synaptic end bulb of the motor neuron and the motor end plate of the muscle fiber
Acetylcholine
a neurotransmitter
Neurotransmitter
a chemical messenger released by the motor neuron into the synaptic cleft, released by somatic motor neurons is acetylcholine
Synaptic vesicles
membrane-bound sacs inside the synaptic end bulb, the synaptic vesicles contain molecules of the neurotransmitter acetylcholine
Motor end plate
the region of the muscle fiber’s sarcolemma opposite the synaptic end bulbs within a neuromuscular junction, contains acetylcholine receptors
Acetylcholine receptors
proteins embedded in the motor end plate, bind to acetylcholine
Excitation
contraction coupling refers to the connection between excitation by a motor neuron and the contraction of the muscle fiber
twitch contraction
a brief contraction of all muscle fibers in one motor unit in response to a single muscle action potential
myogram
a graphical record of muscle contraction in response to electrical stimulation of the motor unit
Latent period
a brief delay between stimulation by motor neurons and the beginning of the muscle fiber contraction
Wave summation
Muscle fibers in the motor unit are stimulated before the muscle is completely relaxed, this creates stronger and stronger contraction in the muscle fiber = summation of the force of contraction
Unfused tetanus
Muscle fibers are stimulated 20-30 times per second, partially relax between contractions, the result is a sustained but wavering contraction
Fused tetanus
Muscle fibers are stimulated 80-100 times per second, and do not relax at all, resulting in a sustained contraction called fused tetanus
