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three types of muscular tissue
skeletal, cardiac, and smooth
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cardiac muscle and smooth muscle are regulated by neurons that are part of the
- autonomic (involuntary) division of the nervous system
- and by hormones released by endocrine glands
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Muscular tissue has four key functions
- producing body movements,
- stabilizing body positions,
- storing and moving substances within the body,
- generating heat.
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thermogenesis is
As muscular tissue contracts, it produces heat
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Properties of Muscular Tissue
- Electrical excitability (action potentials)
- Contractility
- Exstendiblity
- Elasticity
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Electrical excitability
a property of both muscle and nerve cells
- is the ability to respond to certain stimuli by producing electrical signals
- called action potentials.
- Action
- potentials can travel along a cell's plasma membrane due to the presence of
- specific voltage-gated channels.
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muscle cells, two main types of stimuli trigger action potentials.
- One is autorhythmic electrical signals arising in the muscular tissue itself, as in the heart's pacemaker.
- The other is chemical stimuli, such as neurotransmitters released by neurons, hormones distributed by the blood, or even local changes in pH.
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Contractility
- the ability of muscular tissue to contract forcefully when stimulated by an
- action potential
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Extensibility
the ability of muscular tissue to stretch without being damaged
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Elasticity
- ability of muscular tissue to return to its original length and shape after
- contraction or extension.
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Which connective tissue coat surrounds groups of
muscle fibers, separating them into fascicles
Perimysium bundles groups of muscle fibers into fascicles
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The subcutaneous layer or hypodermis
- is composed of areolar connective tissue and adipose tissue
- It provides a pathway for nerves, blood vessels, and lymphatic vessels to enter and exit muscles.
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. Fascia (FASH-ē-a = bandage) what is it?
- is a dense sheet or broad band of irregular connective tissue that lines the
- body wall and limbs and supports and surrounds muscles and other organs of the
- body.
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Fascia - what does it do?
- allows free movement of muscles,
- carries nerves, blood vessels, and lymphatic vessels,
- and fills spaces between muscles
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Three layers of connective tissue extend from the fascia to protect and
strengthen skeletal muscle
- Epimysium
- Perimysium
- Endomysium
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Epimysium
- Outermost layer
- encirculing the entire muscle
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Perimysium
- surrounds groups of 10 to 100 or more muscle fibers, separating them into
- bundles called fascicles (FAS-i-kuls =
- little bundles).
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Endomysium
- Penetrating the interior of each fascicle and separating individual muscle fibers from one another
- a thin sheath of areolar connective tissue.
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Definition of a tendon:
- a cord of dense regular connective tissue composed of parallel bundles of
- collagen fibers that attach a muscle to the periosteum of a bone
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what is aponeurosis
- When the connective tissue elements extend as a broad, flat layer, the tendon
- ie the epicranial aponeurosis on top of the skull between the frontal and occipital
- bellies of the occipitofrontalis muscle
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what are somatic motor neurons
The neurons that stimulate skeletal muscle to contract
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capillaries
- bring in oxygen and nutrients
- and remove heat and the waste products of muscle
- metabolism
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myoblasts
- each skeletal muscle fiber arises during embryonic development from the fusion
- of a hundred or more small mesodermal cells called myoblasts
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Which structure shown here releases calcium ions
to trigger muscle contraction
The sarcoplasmic reticulum releases calcium ions to trigger muscle contraction
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Muscle action potentials travel along the:
- the sarcolemma and through the T tubules, quickly spreading throughout the muscle fiber.
- This arrangement ensures that an action potential excites all parts of the muscle fiber at essentially the same instant.
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Myofibrils contain two types of filaments:
- thick filaments
- and thin filaments
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Which of the following is the smallest: muscle
fiber, thick filament, or myofibril? Which is largest
- thick filament, smallest
- myofibril,
- muscle fiber - largest
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How are sarcomeres separated from one another
Sarcomeres are separated from one another by Z discs
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Z discs
- Narrow, plate-shaped regions of dense material that separate one sarcomere
- from the next.
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A band
- The dark, middle part of the sarcomere that extends the entire length of the thick filaments
- and also includes those parts of the thin filaments that overlap with the thick filaments.
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I band
- The lighter, less dense area of the sarcomere that contains the rest of the thin filaments but no thick filaments.
- A Z disc passes through the center of each I band
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H zone
A narrow region in the center of each A band that contains thick filaments but no thin filaments.
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M line
A region in the center of the H zone that contains proteins that hold the thick filaments together at the center of the sarcomere.
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Myofibrils are built from three kinds of proteins:
- (1) contractile proteins, which generate force during contraction;
- (2) regulatory proteins, which help switch the contraction process on and off;
- (3) structural proteins, which 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.
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two contractile proteins in muscle
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Myosin
- functions as a motor protein in all
- three types of muscle tissue.
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What do Motor Protiens do?
- Motor proteins push or pull various cellular structures to achieve movement by
- converting the chemical energy in ATP to the mechanical energy of motion or the
- production of force
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Contractile proteins (myosin and actin)
what do they do?
- generate force during contraction;
- regulatory proteins (troponin and
- tropomyosin) help switch contraction on and off.
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- A thick filament contains about 300 myosin molecules, one of which is shown
- enlarged. The myosin tails form the shaft of the thick filament, and the myosin
- heads project outward toward the surrounding thin filaments.
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Which proteins connect into the Z disc? Which
proteins are present in the A band? In the I band?
- Actin and titin anchor into the Z disc.
- A bands contain myosin, actin, troponin, tropomyosin, and titin;
- I bands contain actin, troponin, tropomyosin, and titin
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