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Anat CH9


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What does skeletal muscle do?
Moves the body by pulling on the bones of the skeleton allowing the body to walk, dance, or play.
What are the four basic properties of muscle tissues?
What are the five functions of Skeletal muscles?
Produce skeletal movement.

Maintain posture and body positions.

Support soft tissues

Regulate entrance and exit of materials

Maintain body temperature
What are the three layers of muscle?
Epimysium- surrounds entire muscle, surrounds from other organs and tissue.

Perimysium-surrounds each muscle bundle (fascicle)

Endomysium-surrounds each muscle fiber
What is the function of a neuromuscular junction
It facilitates chemical communication between a neuron and a muscle fiber.
What is a sarcolemma?
The cell membrane of a skeletal muscle fiber that surrounds the cytoplasm, or sarcoplasm
What differenciates skeletal muscle fibers from other cells?
Skeletal muscle fibers are very large.

They are multinucleated.

Has deep indentations called transvers (T) tubles which carry electrical impulses that stimulate contractions.
What is a myofibril and what does it do?
A myofibril is a long cylindrical structure that runs the length of a cell. It is responsible for muscle contraction that shortens the cell.
What is a microfilament?
Microfilaments are protein filaments that consist of proteins called actin (thin filaments) and myocin (thick filaments)
What is a sacromere and what is its function?
Sacromeres are the smallest functional unit of the muscle fiber. They are composed of actin and myosin bands that slide over one another causing muscle contraction.
What are the functions of the proteins Troponin and Tropomyocin?
Tropomyosin molecules form a long chan that covers the active sites, preventing actin-myocin interaction. Troponin holds the tropomyosin strand in place. Before muscle contraction can take place toponin must change position which in turn moves the tropomyosin molecules and exposes theactive site so muscle contracton can occur.
What happens at the beginning of a muscle contraction?
An electrical event at the sacrolemmal surface triggers the release of calcium ions from the terminal cisternae which diffuse into the zone of overlap and bind to the troponon. The troponoin changes shape and alters the position of the tropomyocin strand and exposes the active site on the actin molecules allowing a muscle contraction to begin.
What happens at the end of a muscle contraction?
When the electrical stimulation ends the sarcoplasmic reticulum recaptures the calcium ions and the troponin-tropomyocin complex covers the active sites and the contraction ends.
What is the sliding filament theory?
The sliding filament theory explains the physical changes that occur between thick and thin filaments
Summarize what happens in a muscle contraction.
ACh release from synaptic vesicles--binding of ACh to the motor end plates--generation of an electrical impulse in the sarcolemma--conduction od the impulse along the T tubles--release of calcium ions by the SR--exposure of active sites on the thin filaments--cross-bridge formation and contraction.
What is ACh?
ACh is acetylcholine. It is a kind of neurotransmitter which is a chemical that is released by a neuron to communicate with another cell to initiate a contraction
What is AChE?
AChE is acetylcholinesterase which is an enzyme that breaks down ACh.
What is muscle tone?
Some of the motor units of muscles contract continuously producing a resting tension in skeletal muscles. Ex: muscles used in posture and balance produce enough tension to maintain body position.
What is Hypertrophy?
When muscles are repeatedly stimulated to produce near maximal tension causing an increase in mitochondria, glycolic enzymes and glycogen reserves. Ex: bodybuilders
What is Atrophy?
Reduction in muscle tone, power and size due to disuse of the muscle.
What are the three types of skeletal muscle fibers in the body?
Fast fibers (white fibers)
Slow fibers (red fibers)
Intermediate fibers
What are Fast Fibers?
Fast fibers (white)are large and contain densley packed microfibrils, large glycogen reserves, and relatively few mitochondria. They provide a fast burst of energy.
What are Slow Fibers?
Slow fibers (red) are smaller than fast fibers, they take three times as long to contract after stimulation, they have an extensive network of capillaries and many mitochondria. They provide long lasting energy as in long distance runners.
What are the four different patterns of fascicle arrangement?
Parallel muscle
Convergent muscle
Pennate muscle
Circular muscle
What are the characteristics of parallel muscles?
A parallel muscle has facicles that are parallel to the long axis of the muscle.Most of the muscles in the body are parallel. Ex: Biceps Brachii
What are the characteristics of convergent muscles?
Convergent muscles have muscle fibers that are based over a broad area, but all the fibers come together at a common attachment site. Ex: the pectoral muscles
What are the characterisicts of pennate muscles?
Pennate muscles have one or more tendons running thru the muscle, and the fascicles form an oblique angle to the tendon. Penate muscles can be unipennate, bipennate, or multipennate.
What are the characteristics of circular muscles?
Circular muscles, also called sphincter, have the fibers concentrically arranged around an opening or recess. Ex: Orbicularis oris (around the mouth)
What is muscle terminology?
Each muscle begins at an origin and ends at an insertion. Typically the origin remains stationary and the insertion moves.
What are the two methods of describing muscle actions?
The first refers to the bone region affected "flexion of the forearm". The second refers to the specific joint involved "flexion at the elbow"
What is a prime mover?
Prime movers are called agonists. They are responsible for producing a particular movement.
What is a Synergist?
A Synergist assists a prime mover in performing its action.
What is an antagonist?
An Antagonist is a muscle whose actions oppose those of the agonist.
What are the ways that muscles are named?
Muscles are named according to specific body parts, or by the shape of the muscle, or the orientation of the muscle, or for a special or unusual feature, ot it can be identified by its origin and insertion, or by its primary function, or in reference to its actions.
What are levers?
A lever is a rigid structure that moves on a fixed point called a fulcrum. In the body each bone is a lever and each joint is the fulcrum.
What do levers do?
Levers can change the direction of an applied force, or the distance and speed of movement produced by a force, and the stength of a force.
What are the classes of levers?
First class levers-fulcrum line is between the applied force and the resistance.
Second class levers-resistance is located between the applied force and the fulcrum.
Third class levers-force is applied betwen the resistance and the fulcrum. Third class levers are the most common.
What are the effects of aging on the muscular system?
Skeletal muscle fibers become smaller in diameter.

Skeletal muscles become smaller in diameter and less elastic.

Tolerance for exercise decreases.

Ability to recover from muscular injuries decreases.

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