Chapter 12-muscles Flashcards
Extensor action
Increases the angle at a joint
Flexor action
Decreases the angle at a joint
Abductor action
Moves limb away from midline of body
Adductor action
Moves limb toward midline of body
Levator action
Moves insertion downward
Rotator action
Rotates a bone along its axis
Sphincter action
Constricts an opening
The prime mover of any skeletal movement is the
Agonist muscle. In flexing for example, the flexor is the agonist muscle
Flexors and extenders that act on the same joint to produce opposite actions are
Anatagonistic muscles
Epimysium is the
Fibrous connective tissue proteins within the tendons extend around the muscle in an irregular arrangement forming a sheath (epimysium)
Fascicles are
Inside the muscle epimysium divides muscle into columns called fasicles
Connective tissue around fascia is
perimysium
Plasma membrane of muscle is
sarcolemma
What are antagonist muscles?
muscles (flexors and extensors) that act on the same joint to produce opposite actions
What is a motor end plate?
Region on sarcolemma where the neuromuscular junction is the motor end plate
Which are considered the dark bands and light bands?
A bands are dark, I bands are light.
The motor neuron stimulates the muscle fiber to contract by _____________ at the neuromuscular junction
liberating acetylcholine
Where is the cell body of a somatic neuron located?
the ventral horn of the gray matter of spinal cord.
What is a motor unit?
Each somatic motor neuron together with all of the muscle fibers that it innervates.
What are graded concentrations?
Where contraction strength is varied.
What happens when a somatic motor neuron is activated?
All of the muscle fibers it innervates are stimulated to contract.
When contractions of greater strength are required, larger and larger motor units are activated in a process known as
recruitment of motor units
The light I band contains _____ filaments
thin
The dark A band contains ______ filaments
thick
Thick filaments are composed of the protein ______
myosin
The thin filaments are composed of the protein ______
actin
What is the central region of sarcomere?
H zone. Only contains thick filaments
What is titin?
A type of elastic protein that runs through the thick filaments from the M lines to the Z disc
Titin purpose
Contribute to elastic recoil of muscles that helps them to return to their resting length during muscle relaxation
As sarcomeres shorten in length… the _ bands do not ______, but move ______ together
A, shorten, closer
The I bands which represent the distance between A bands of successive sarcomeres _______ in length
decrease
The thin filaments composing the I band _______
do not shorten
During contraction, thick and thin filaments _______
remain the same length
Shortening of the sarcomeres is produced not by shortening of the filaments but rather by _______ of thin filaments over and between the thick filaments
sliding
The I bands (contain only thin filaments) and H bands (containing only thick filaments) get _______ during contraction
shorter
Describe steps of sliding filament theory of contraction
- A myofiber, along with all its myofibrils shorten by movement of the insertion toward the origin of the muscle.
- Shortening of the myofibrils is caused by shortening of the sarcomeres- the distance between Z lines is reduced.
- Shortening of the sarcomeres is done by sliding of the myofilaments-the length of each filament remains the same during contraction.
- Sliding of the filaments id produced by asychronous power strokes of myosin cross bridges, which pull the thin filaments (Actin) over the thick filaments (myosin)
- The A bands remain the same length during contraction, but are pulled toward the origin of the muscle.
- Adjacent A bands are pulled closer together as I bands between them shorten.
- The H bands shorten during contraction as the thin filaments on the sides of the sarcomeres are pulled toward the middle.
Muscle contracts because _____ get shorter
myofibrils
_____ filaments slide over and between _____ filaments towards the center
thin, thick
Sliding of filaments is produced by the action of numerous
cross bridges that extend out from myosin toward the actin.
Cross bridges are part of the _____ protein that extend from the axis of thick filaments to form “arms” that terminate in globular “heads”
myosin
Each myosin head contains an _____ binding site which functions as ______
ATP binding site and ATPase
Cross bridge power stroke steps
- Resting fiber, cross bridge is not attached to acin. ADP. Inorganic phosphate are attached,
- Cross bridge binds to actin
- Pi is released from myosin head, causing conformational change in myosin.
- Power stroke causes filaments to slide. ADP is released
- A new ATP bings to myosin head, allowing it to release from actin.
- ATP is hydrolyzed and phosphate binds to myosin, causing cross bridge to return to its orginal orientation.
Twitch is a ____ ________
single contraction
A single rapid contraction and relaxation of muscle fibers is a
twitch
Skeletal muscles can produce
graded contractions, the strength of which depends on the number of fibers stimulated rather than on the strength of the contractions of individual muscle fibers.
Imcomplete tetanus refers to
If muscle is stimulated by an increasing frequency of electrical shocks, its tension will increase to a maximum
Complete tetanus refers to
Contraction that is smooth and sustained as it is during normal muscle contracction within body.
Treppe (stair case effect) refers to
If cold muscle is repeatedly stimulated with maximum voltage to produce individual twitches, successive twitches get larger
Treppe is caused by
accumulation of intracellular Ca++
During isotonic contraction…
force remains constant throughout shortening process, length changes. (Lifting something off table)
During isometric contraction…
exerted force does not cause load to move and length of fibers remains constant (Lifting table, holding the weight)
