Anatomy Chapter 11 The Muscular System
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There are ______ Human skeletal muscles
What are the levels of the fascia?
- Covers whole muscle belly
- blends into connective tissue that separates muscles
- a slightly thicker layer of connective tissue
- surrounds a bundle of cells called a fascicle
- A thin layer of areolar tissue surrounding each cell
- allows room for capillaries and nerve fibers
Where is Deep Fascia found?
Between adjacent muscles
Where is Superficial Fasscia (Hypodermis) found?
- Between skin and muscle
- *contains adipose tissue*
Most skeletal muscles span _____ and are attached to bone in at least two places
When muscles contract the ______ bone, the muscle's insertion moves toward the _______ bone (The muscles origin)
Muscles attach in what two ways?
- Directly: epimysium of the muscle is fused to the periosteum of a bone
- Indirectly: connective tissue wrappings extend beyond the muscle as a tendon or aponeurosis
Each muscle is served by one ____, an _____, and one or more ______
Each skeletal muscle fiber is supplied with a _______ ending that controls _________
__________ require continuous delivery of oxygen and nutrients via arteries
Wastes must be removed via
Describe a muscle fiber
- A long, cylindrical cell with multiple nuclei just beneath the sarcolemma
- Fibers are 10 to 100 mm in diameter, and up to hundreds of centimeters long
Each cell is a _________ produced by fusion of embryonic cells
Sarcoplasm has numerous _________ and a unique oxygen-binding protein called ________
Muscle Fibers contain ______, ______, ___________, and _________
- sarcoplasmic reticulum
- T tubules
densly packed, rodlike contractile elements
______ make up most of the muscle volume
The arrangement of myofibrils within a fiber is such that a
perfectly aligned repeating series of dark A bands and light I bands is evident
What is the smallest contractile unit of a muscle
A Sarcomere is
the region of a myofibril between two successive Z discs
Sarcomeres are composed of
Thick and thin myofilaments made up of contractile protein
Thick myofilaments extend...
the entire length of an A band
Thin myofilaments extend..
across the I band and partway into the A band
What is a Z-disc?
a coin-shaped sheet of proteins (connectins) that anchors the thin filaments and connects myofibrils to one another
Thick filaments are composed of the protein ____
Each ___________ has a rodlike tail and two globular heads
two interwoven, heavy polypeptide chains
Two smaller, light polypeptide chains called cross bridges
Thin filaments are chiefly composed of the protein ____
Each _______ is a helical polymer of globular subunits called G actin
The subunits of actin molecule contain the active cites to which _______ attach during contraction
_________ and ________ are regulatory subunits bound to actin
Tropomyosin and troponin
Sarcoplasmic Reticulum is
an elaborate, smooth enodplasmic reticulum that mostly runs longitudinally and surrounds each myofibril
Sarcoplasmic Reticulum functions in the regulation of ____________ levels
Elongated tubes called _________ penatrate into the cell's interior at each A band-I band junction
_________ associate with the paired terminal cisternae to form _____
T Tubles are continuous with the ______
T Tubules conduct _____ to the deepest regions of the muscle
The impules conducted by T Tubules signal for the release of ______ from adjacent terminal cisternae
______ and __________ provide tightly linked signals for muscle conraction
A double zipper of ___________________ protrudes into the intermembrane space
integral membrane proteins
T tubule proteins act as __________
SR foot proteins are receptors that regulate ____ release from the SR cisternae
At low intracellular Ca2+ concentration:
- Tropomyosin blocks the binding sites on actin
- Myosin cross bridges cannot attach to binding sites on actin
- The relaxed state of the muscle is enforced
At higher intracellular Ca2+ concentrations
- Additional calcium binds to troponin ( inactive troponin binds two Ca2+)
- Calcium- activated troponin binds an additional two Ca2+ at a separate regulatory site
refers to the activation of mysoin's cross bridges (force- generating sites)
_______ occurs when the tension generated by the cross bridge exceeds forces opposing shortening
________ ends when cross bridges become inactive, the tension generated declines, and relaxation is induced
Contraction of ______-- and ___________ is similar
- mucle fibers (cells)
- muscles (organs)
Two types of muscle contractions are
- Isometric contraction
- Isotonic contraction
An isometric contraction is
increasing mucle tension (Muscle does not shorten during contraction)
Isotonic contraction is
decreaseing muscle length (muscle shortens during contraction
A motor unit is a __________ and all the muscle fibers it supplies
The number of muscle fibers per motor unit can vary from
four to several hundred
Muscles that control fine moevemnts (fingers, eyes) have
small motor units
Factors Affecting Muscle Tension
- Frequency of stimulation
- Length of fibers
- Number of fibers contracting
Amount of tension production by muscle fibers depends on
number of cross bridges formed
Skeletal muscle contracts most forcefully over
a narrow ranges of resting length
What is a twitch?
Cycle of contraction, relaxation produced by a single stimulus
What is a Treppe?
Repeated stimulation after relaxation phase has been completed
What is summation?
Repeated stimulation BEFORE relaxation phase has been completed
one twitch is added to another
muscle never relaxes completely
relaxation phase is eliminated
What is a Myogram?
The record of a muscle contraction
What are the 3 periods of a myogram?
Where is internal tension generated?
inside contracting muscle fibers
Where is external tension generated?
in extracellular fibers
Muscle tone _______ bones and joints
All the muscle fibers are ______ by one neuron
Precise control of movement is determined by ______ and ______ of motor unit
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