The Muscular System

Sliding Filam Ent Theo
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Who discovered the sliding filament theory?
Hugh Huxley in 1969
What are the 4 purposes of muscles?

Maintain vertical posture in space - tonus
Heat through shivering
External mobility - skeletal
Internal movility - cardiac, smooth
A muscle is referred to as ___ ____s because of their threadlike, slender shape.
Muscle fibers
Each muscle fiber is made up of a bunch of ________________, very fine, longitudinal fibers, consisting of thick and thin myofilaments.
A connective tissue called the __________ covers the muscle fibers.
Groups of muscle fibers are called __________ and are bound together by the perimysium.
From macroscopic to microscopic: Muscle > _____ > muscle fiber (cell) > myofibril > __________ .

What anchors the muscle to the bone?
A broad flat tendon
Aponeurosis. Tendons are more like cords, whereas aponeuroses are more sheetlike.
What is a tendon sheath?
Tubular structures that wrap tendons as they cross multiple joints, as in the hands and feet.
What is retinacula?
Bandagelike retaining bands of connective tissue, found primarily in the elbows, knees and wrists, to keep tendons and tendon sheeths in place.
What is sarcolemma?
The cell membrane of a muscular cell.
In a muscular cell, what is the cytoplasm called?
Whatr do you call many muscle fibers bound up together?
Explain the muscle cell version of the endoplasmic reticulum?
Sarcoplasmic reticulum is a system of cavities that contain sarcomeres. It holds and releases calcium ions.

Connective tissue coverings from macroscopic to microscopic:
____ ______ (wraps around muscle groups) > Epimysium (wraps around ________ _________) > Perimysium (wraps around __________) > _____________ (wraps around muscle fibers)

Deep fascia
entire muscle
______________ spread the nerve impulse by transporting stored ions into and out of the cell.
Transverse tubules (T Tubules)
What are the 5 types of muscle fiber arrangements and give an example of each:

Circular (mouth);
pennate (quads) ;
parallel (romboids);
convergent (trapezoid),
Fusiform (calf)
The muscle responsible for causing a specific or desired reaction.
Agonist (or primary mover)
Opposing muscle to the agonist, must relax and lengthen
What is the part of the skeletal muscle that is the tendinous attachment closest to the axillary skeleton?
What is a muscle called that crosses two joints?
What does multiarticular mean?
A muscle that crosses more than two joints
What is the opposite of muscular contraction?
Muscular stretching
What is tonus?
Ability of the body to hold itself upright in space
What are troponin and tropomyosin?
Proteins. Troponin is attached to actin and holds the tropomyosin on the myosin. In muscle contraction, calcium moves them off, exposing the binding sites for the myosin to grab onto.
What is concentric contraction?
An isotonic contraction of the muscle that shortens it.
Compare the origin and insertion of a muscle.
The origin is the attaching point on the part of the skeleton with the least movement. Insertion is the attachment place that is less stationary.
Explain muscle spindles and golgi tendon organs.
Both proprioreceptors, muscle spindles are located in the belly of the muscle and are stimulated by rapid movement. They contract to protect the muscle. Golgi tendon organs are stimulated by slow, static stretch. They stretch to protect the muscle.
What is a motor unit?
A single motor neuron plus all its muscle fibers.
What are the four roles a muscle might take when coordinating with other muscles?

Agonist - primary mover
Antagonist - relaxes to assist agonist
Synergist - works along with agonist to assist
Fixator - specialized synergist that provide stabilization
What is the difference between a fast twitch, slow twitch and intermediate twitch?

Fast twitch is white muscle that fatigues easily. Slow twitch is red muscle that has endurance.
Intermediate is pink and can go either way as needed.
What is recruitment?
Motor unit activation based on need.
What is extensibility?
Ability of muscle fibers to lengthen
What are motor end plates?
Fold in the sarcomere where motor neurons connect.
What does myofascial refer to?
Skeletal muscles and their related fascia in the muscular system.
What is aponeurosis?
A broad, flat tendon
What are fasciculi?
Bundles of muscle fibers held together by perimysium.
What is myosin?
A thick protein filament in myofibrils that works with actin to create a sliding filament.
What is retinacula?
Retaining bands of connective tissue that cover tendons in wrists, hands, knees
What structure releases calcium?
Sarcoplasmic reticulum
What purposes does the muscular system serve?

Provide heaI through shivering
Enable upright posture
Internal movement
External movement
Explain the sliding filament theory.
Brain releases a motor neuron that travels to muscle cell. It releases a nerve impulse that strikes the sarcolemma at the motor end plate, creating a neuromuscular junction. The space occupying the junction is a synapse where chemical messengers like ACh diffuse. When ACh crosses the synaptic cleft to the sarcolemma, it binds with receptor sites on the motor end plate, similar to a key in a lock. The impulse travels across the sarcolemma to the T Tubules where it is carried into the cell. This triggers the release of calcium, which makes the troponin and tropomyosin slide off the actin and so the myosin head can attach to the actin. After the power stroke, the SR starts pulling back the calcium ions. ATP becomes ADP and is now junk. The troponin slides back the binding sites on the actin and the myosin heads come loose.

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