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CH10A&PMuscle tissue

TermDefinition
The primary function of muscle is to change chemical energy into mechanical energy to produce body movement.
The three types of muscle tissue are skeletal cardiac smooth
Skeletal muscle tissue is striated, under voluntary control, and functions to move bones of the skeleton
Cardiac muscle tissue is s striated, under involuntary control, has autorhythmicity, and is found only in the heart.
Smooth muscle tissue is nonstriated, under involuntary control, and is located in the walls of hollow internal structures.
Muscle tissue has four important functions : producing body movements, stabilizing body positions, moving substances within the body, and producing heat.
Muscle tissue has four special properties electrical excitability, contractility, extensibility, and elasticity.
A skeletal muscle is an organ composed of elongated muscle fibers plus associated nerves, blood vessels, and connective tissues.
Hypodermis separates muscle from skin
Fascia unites muscles with similar functions, carries nerves and vessels, and fills spaces between muscles
3 layers of connective tissue epimysium perimysium endomysium protect and strengthen skeletal muscle: These three layers may extend beyond the muscle to form a tendon, or a broad flat aponeurosis
epimysium the outermost layer encircles the muscle
perimysium bundles together groups of muscle fibers into fascicles
endomysium the innermost layer, surrounds each muscle fiber
Tendons and aponeuroses attach a muscle to bone
One artery and one or two veins supply each skeletal muscle
Motor ________stimulate muscle fibers through processes called _______. neurons, axons
Skeletal, cardiac, and smooth muscle tissues differ in location, structure, and function
skeletal muscles are? surrounded by connective tissues and are well supplied with nerves and blood vessels
Each skeletal muscle fiber is covered by? a sarcolemma; each of its myofibrils is surrounded by sarcoplasmic reticulum and contains sarcomeres
Embryonic development of skeletal muscle fibers arises from? fusion of myoblasts into one elongated, multinucleate, amitotic muscle fiber
Some myoblasts persist as satellite cells in mature skeletal muscle that can fuse and regenerate muscle fibers in damaged tissue. Extensive damage involves fibrosis
fibrosis the replacement of muscle fibers with scar tissue.
Aƞer birth, muscle growth occurs from enlargement of existing muscle fibers, termed hypertrophy, stimulated by human growth hormone, testosterone, and other hormones.
hypertrophy the enlargement of existing muscle fibers
The sarcolemma has many invaginated, tunnel-like extensions called sverse (T) tubules that are also open to the cell’s exterior.
The sarcoplasm contains glycogen, and a red protein, called myoglobin, that binds oxygen molecules for use in ATP synthesis
The sarcoplasm is full of long contractile elements, called myofibrils, which give the fiber its striated appearance
sarcoplasmic reticulum (SR) wraps around each myofibril. The SR stores and releases Ca . The dilated end sacs of the SR, called terminal cisterns, lie on each side of one T tubule, forming a triad.
terminal cysterns dilated end sacs of the SR, lie on each side of one T tubule, forming a triad.
Myofibrils contain thin filaments and thick filaments arranged in basic functional units called sarcomeres
Sarcomeres in a myofibril are separated from one another by Z discs
A darker middle part of the sarcomere containing thick and thin overlapping filaments is the A band
at the center of A band is a narrow H zone containing only thick myofilaments.
I bands contain only thin filaments and are located near the Z discs at the ends of a sarcomere
The contractile proteins, myosin and actin, are located inside myofibrils
Myosin the main component of thick filaments, converts chemical energy in ATP to the mechanical energy of motion.
Actin has a myosin-binding site where the myosin head can attach.
Two regulatory proteins, are also part of the thin filament, and help switch contraction on and off. tropomyosin and troponin
In addition to contractile and regulatory proteins, muscle contains structural proteins such as titin and dystrophin
titin helps anchor a Z disc to the M line
dysrophin links thin filaments of the sarcomere to the sarcolemma.
The neuromuscular junction is where a muscle action potential is initiated
Muscle action potentials arise at the________ , the _______between a motor neuron and a skeletal muscle fiber. neuromuscular junction, synapse
The synaptic end bulbs have synaptic vesicles containing the neurotransmitter acetylcholine (ACh).
The motor neuron releases ______ into the synaptic cleft; ACh binds to___________on the motor end plate region of the sarcolemma of the muscle fiber ACh, acetylcholine receptors 2+
Events in the excitation of a skeletal muscle fiber include the following release of acetylcholine as an impulse from the brain or spinal cord reaches the synaptic end bulbs; activation of ACh receptors when ACh binds to a motor end plate ACh receptor, which opens ion channels; generation of a muscle action potential that stim
An action potential releases calcium ions that allow thick filaments to bind to and pull thin filaments toward the center of the sarcomere
An action potential releases ______ that allow thick filaments to bind to and pull thin filaments toward the center of the_________ calcium ions, sarcomere
The sliding filament mechanism of muscle contraction involves thin filaments at both ends of the sarcomere being pulled to the center of the sarcomere by myosin head activity. Z discs come closer together and the sarcomere shortens
When a muscle action potential propagates along the sarcolemma and T tubules, it opens Ca2+ release channels in the SR membrane
Ca flows into the sarcoplasm and combines with troponin, moving the troponin–tropomyosin complex away from myosin-binding sites on actin
Myosin heads then bind to actin.
The contraction cycle consists of four steps. 1st step ATP splits on the myosin head to reorient and energize it
The contraction cycle consists of four steps, 2nd step myosin attaches to actin when the energized myosin head attaches to the myosin-binding site on actin
The contraction cycle consists of four steps 3rd step myosin attaches to actin when the energized myosin head attaches to the myosin-binding site onactin; the power stroke occurs when the energized myosin head releases the phosphate group, triggering ADP release and myosin rotation, which slides the thin fil
The contraction cycle consists of four steps 4th step myosin detaches from actin as ATP binds to the myosin head. ATPase splits ATP on the myosin head, and energy is transferred to the myosin head as it is energized and reoriented in position
The contraction cycle repeats as successive power strokes result in shortening of the sarcomeres
As Z discs pull on adjacent sarcomeres, the whole muscle fiber shortens, and, ultimately, the entire muscle shortens
Cessation of impulses in the motor neuron stops ACh release
AChE breaks down any ACh in the synaptic cleft
Ion channels close, action potentials stop, and Ca active transport pumps use ATP to move Ca back into the SR
The troponin–tropomyosin complexes slide back to cover myosinbinding sites of actin, and thin filaments return to their relaxed positions.
Muscle tension is controlled by stimulation frequency and motor unit recruitment
A single impulse in a motor neuron elicits a single muscle twitch contraction in all muscle fibers that it innervates.
The frequency of stimulation governs the total tension that can be produced by a single muscle fiber.
The total tension produced in a whole muscle depends on the number of fibers contracting in unison.
motor unit is one motor neuron and all skeletal muscle fibers the motor neuron stimulates.
Muscles controlling small, precise movements are innervated by many small motor units
muscles controlling large, powerful movements have fewer, large motor units
The size of a muscle’s motor units and the number of motor units activated contribute to the contraction strength.
The response of a motor unit to a single impulse in its motor neuron is a twitch contraction
. The three phases of a twitch contraction are latent contraction relaxation
latent period cell events leading up to contraction
contraction period power strokes generating tension
relaxation period the muscle is allowed to resume its original length
Multiple stimuli that arrive before the muscle fiber has fully relaxed lead to wave summation
When the frequency of stimulation allows partial relaxation it is called______ or ________. unfused tetanus, incomplete tetanus
rapid frequency of stimulation and sustained contraction is called ________or_____________. fused tetanus, complete tetanus
Motor unit recruitment is the process of increasing the number of contracting motor units.
A muscle at rest exhibits________, a small amount of tension due to involuntary alternating contractions of a small number of its motor units that do not produce movement muscle tone
Damaged motor neurons that cannot maintain muscle tone cause a muscle to become flaccid
Isotonic contractions involve a change in muscle length without a change in its tension.
There are two types of Isotonic contractions concentric isotonic contractions eccentric isotonic contractions
concentric isotonic contractions occur when the muscle shortens
eccentric isotonic contractions occur when the muscle lengthens
isometric contraction occurs when the load equals or exceeds the muscle tension, and the muscle does not lengthen or shorten
is the only direct source of energy for muscle contraction ATP
Muscle fibers have three ways to produce ATP: from creatine phosphate, by anaerobic glycolysis, and by aerobic respiration
Muscle fibers break down excess ATP and transfer a phosphate group to creatine, forming creatine phosphate and ADP
During contraction, muscle fibers transfer the phosphate group from creatine phosphate to ADP, forming ATP
A muscle at peak activity quickly depletes available ATP and creatine phosphate, and it will then catabolize glucose molecules from glycogen
is the initial pathway in glucose breakdown and yields two ATP molecules and two pyruvic acid molecules Glycolysis
When oxygen is unavailable, anaerobic reactions convert pyruvic acid to lactic acid
Blood removes lactic acid from skeletal muscle and carries much of it to the liver for reconversion to glucose.
When oxygen is available, the pyruvic acid molecules from glycolysis enter the ___________ , where aerobic respiration completely oxidizes each molecule of glucose to generate ________ATP molecules. mitochondria, 30 or 32
the inability of muscle to contract forcefully after prolonged activity. Muscle fatigue
Heavy breathing after prolonged muscle activity helps to repay the oxygen debt, more accurately referred to as recovery oxygen uptake
This increased oxygen intake helps to restore metabolic This increased oxygen intake helps to restore metabolic conditions to the resting level by conversion of lactic acid to glycogen, resynthesis of creatine phosphate and ATP, and replacement of oxygen in muscle fibers.
1. Skeletal muscle fibers with low myoglobin content appear pale and are called white muscle fibers
skeletal muscle fibers with high myoglobin content have a dark, reddish appearance and are called red muscle fibers
Skeletal muscle fibers are classified as slow oxidative, fast oxidative–glycolytic, and fast glycolytic.
Slow oxidative fibers use aerobic respiration, have a slow speed of contraction, and are fatigue resistant. These fibers are beneficial for posture and endurance activities.
Fast oxidative–glycolytic fibers use aerobic respiration and glycolysis, have fast speeds of contraction, and are moderately fatigue-resistant. These fibers are used for walking and sprinting.
. Fast glycolytic fibers mainly use glycolysis, contract strongly and rapidly, and are adapted for intense bursts of anaerobic movements, but they fatigue rapidly.
Most skeletal muscles in the body are a mixture of all three types of muscle fibers
Training, genetics, and muscle action can slightly alter proportions of the fiber types.
Cardiac muscle tissue is found in the wall of the heart
Cardiac muscle fibers have one nucleus and are branched and striated
Cardiac muscle fibers interconnect by intercalated discs containing desmosomes and gap junctions
Long, sustained contractions are supported by inflow of Ca2+ into the sarcoplasm
Specialized cardiac muscle fibers have autorhythmicity
is needed for the continuous contraction–relaxation cycle that occurs in cardiac muscle fibers. A constant supply of oxygen and nutrients
There are two types of smooth muscle tissue (1) visceral (single-unit) smooth muscle tissue (2) multiunit smooth muscle tissue
visceral (single-unit) smooth muscle tissue is autorhythmic, and the fibers are connected by gap junctions allowing action potentials to spread throughout the network so that cells contract as a single unit
multiunit smooth muscle tissue acts independently, has few gap junctions, and lacks autorhythmicity.
Smooth muscle fibers have tapered ends, one central nucleus, are nonstriated, and lack sarcomeres. Intermediate filaments form bundles that stretch between dense bodies
Thin and thick filaments of smooth muscle have a sliding mechanism that generates tension, resulting in lengthwise shortening of the fiber
Smooth muscle contraction starts slowly and lasts an extended time.
Smooth muscle is involuntary and responds to autonomic nervous system impulses, hormones, and local factors
Created by: fieldslady80