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Muscle Tissue & Physiology
Salisbury University: Dr.Hogue - Ch.10
55
Anatomy
Undergraduate 2
10/30/2008

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Term
How are skeletal muscle fibers formed?
Definition
By the fussion of multiple myoblasts (mesodermal cells).
Term
What are the 3 levels of muscle organization?
Definition
Muscle, Fascicles, & Fibers
Term
What is the Epimysium
Definition
A dense connective tissue capsule that surrounds muscles.
Term
What is the Perimysium?
Definition
Connective tissue capsule surrounding the Fascicles in a muscle.
Term
What is the Endomysium?
Definition
Capsule that surrounds Fibers in a muscle.
Term
What do all 3 "mysiums" do at the end of a muscle?
Definition
Merge at the end to form tendons that attach to bones.
Term
What does T-Tubules stand for?
Definition
Transverse Tubules
Term
What are T-Tubules?
Definition
Tubular extensions of cell membrane into a cell.
Term
What are T-Tubules used for?
Definition
To transmit the Action Potential through the cell, and to allow the entire muscle fiber to contract simulataneously.
Term
What are Myofibrils?
Definition
Bundles of protein filaments that are responsible for muscle contraction.
Term
What are the 2 types of Filaments in Myofibrils?
Definition
Thin & Thick Filaments.
Term
What are Thin Filaments made of?
Definition
Actin
Term
What are the Thick Filaments made of?
Definition
Myosin
Term
What is the Sarcoplasmic Reticulumn?
Definition
A membrane bag that surrounds each myofibril.
Term
What is the Sarcoplasmic Reticulumn responsile for?
Definition
Releasing calcium in response to Action Potential in T-Tubules.
Term
What is the Sarcoplasmic Reticulumn responsile for?
Definition
Releasing calcium in response to Action Potential in T-Tubules.
Term
What happens once Calcium enters the Myofibril?
Definition
Muscle contractions initiate
Term
What are Myofibrils made up of?
Definition
Sarcomeres that are stacked end to end.
Term
What are Sarcomeres?
Definition
The basic contractile unit of muscles.
Term
What 5 things are Sarcomeres composed of?
Definition
Thin Filaments, Thick Filaments, Z-Line, M-Line, & Zone of Overlap
Term
What is the M-Line, and what does it do?
Definition
Midline of sarcomere and it connects adjacent thick filaments.
Term
What is the Z-Line, and what does it do?
Definition
Forms the end of sarcomeres and it connects adjacent thin filaments.
Term
What is the Zone of Overlap?
Definition
Where Thin & Thick Filaments meet. (dark area on micrograph)
Term
What are the Myosin Molecules on Thick Filamnts responsible for?
Definition
the head latches onto the thin filament and bends at the hinge to slide the thing filament towards the M-Line.
Term
What are Thin & Thick Filaments linked by?
Definition
Titan
Term
What binds to the Troponin Molecule?
Definition
Ca2 that is released by the Sarcoplasmic Reticulumn.
Term
What happens when the Active Site becomes exposed?
Definition
Myosin heads on the adjacent Thick Filaments bind to them.
Term
What is the Motor End Plate?
Definition
Place where tips of a motor neuron axon contact a muscle cell to stimulate muscle contraction.
Term
What is the Neuromuscular junction?
Definition
the actual contact between the axon tips and the muscle cell sarcolemma.
Term
What is Rigor Mortis?
Definition
A fixed muscular contraction after death.
Term
What causes Rigor Mortis?
Definition
When calcium builds up in the cytoplasm because it is no longer actively pumped back into sarcoplamic reticulum.
Term
What does Muscle Tension depend on?
Definition
the frequency of neural stimulation and, the fibers resting length at the time of stimulation. (the amount of overlap between thin & thick filaments)
Term
What happens when the Zone of Overlap is too small?
Definition
Tension is lowered because not all myosin heads can attach to the thin filaments
Term
What happens when the Zone of Overlap is too big?
Definition
creates resistance to filament sliding
Term
What is Muscle Recruitment?
Definition
activation and summation of multiple motor units
Term
What are the 3 types of muscle contractions?
Definition
Concentric, Eccentric, & Isometric
Term
What is a Concentric Contraction?
Definition
muscle tension > resistance, causing muscle to shorten
Term
What is an Eccentric Contraction?
Definition
muscle tension < resistance, causing muscle to lengthen
Term
What is an Isometric Contraction?
Definition
muscle tension = resistance, causing muscle to stay the same length
Term
What does ATP stand for?
Definition
Adenosine triphosphate
Term
What is ATP
Definition
the energy molecule necessary for contraction
Term
What is muscle fatigue?
Definition
When muscles can no longer perform a required activity
Term
What are the 3 characteristics of muscle fatigue?
Definition
Exhaustion of metabolic reserves,
High acidity from presence of lactic acid, and
Damage to cell membrane & sarcoplasmic reticulum
Term
What 2 things does the liver do to replenish energy precursors?
Definition
converts lactic acid to pyruvic acid for later conversion to ATP, and releases glucose to recharge muscle glycogen reserves, also for future ATP production
Term
What are the 3 types of Skeletal muscle fibers?
Definition
Fast, Slow, and Intermediate Fibers
Term
What color are pale muscles composed mostly of fast fibers (e.g., chicken breast)
Definition
white
Term
What color are dark muscles composed of mostly slow fibers (e.g., chicken legs)?
Definition
red
Term
What color are human muscles?
Definition
pink muscle composed of a mixture of fiber types
Term
What is Muscle Hypertrophy
Definition
growth from heavy training
Term
what does muscle hypertrophy involve?
Definition
increased diameter of muscle fibers,
increased number of myofibrils,
increased number of mitochondria & glycogen reserves, and increased power
Term
What is Muscle Atrophy?
Definition
muscle shrinkage due to lack of activity
Term
What does muscle atrophy involve?
Definition
reduced power
Term
What does aerobic endurance involve?
Definition
prolonged, aerobic activities (e.g., aerobic exercise)
Term
What does aerobic endurance emphasize?
Definition
slow twitch fibers
Term
How is aerobic endurance improved?
Definition
By building up cardiovascular fitness through repetitive training
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