Structural kinesiology Quiz 2

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Aggregate Muscle Action

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Aggregate Muscle Action

Muscles work in groups rather than independently to achieve a given joint motion.

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Skeletal Muscles

two types: Parallel & Pennate

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Parallel Muscles

Fibers arranged parallel to length of muscles will produce a greater range of movement than similar-size muscles with a pennate arrangement.

Five types: Flat, Fusciform, Strap, Radiate, Sphincter


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Flat Muscles

Usually thin & broad, originating from broad, fibrous, sheet-like aponeuroses

allows them to spread their forces over a broad area.

Ex. rectus abdominus & external oblique

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Fusiform Muscles

Spindle-shaped with a central belly that tapers to tendons on each end; this allows them to focus their power on small, bony targets.

Ex. brachialis & brachioradialis

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Strap Muscles

More uniform in diameter with essentially all fibers arranged in a long parallel manner. This also enables a focusing of power onto small, bony targets.

Ex. sartorius

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Radiate Muscles

Also described sometimes as being triangular, fan-shaped or convergent

have combined arrangement of flat & fusiform muscles, in that they originate on broad aponeuroses & converge onto a tendon.

Ex. pectoralis major & trapezius

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Sphincter (Circular) Muscles

Technically endless strap muscles that surround openings & function to close them upon contraction.

Ex. orbicularis oris (surrounding the mouth)

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Pennate Muscles

Have shorter fibers

arranged obliquely to their tendons in a structure similar to a feather. This arrangement increases the cross-sectional area of the muscle, thereby increasing its force production capability.

three types: Unipennate, Bipennate, Multipennate


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Unipennate Muscle Fibers

Fibers run obliquely from a tendon on one side only.

Ex. biceps femoris, extensor digitorum longus, & tibialis posterior

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Bipennate Muscle Fibers

Fibers run obliquely from a central tendon on both sides.

Ex. rectus femoris & flexor hallucis longus

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Multipennate Muscles

Several tendons with fibers running diagonally between them.

Ex. deltoid

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Skeletal Muscle Tissue

Its ability to produce force effecting movement about joints.

four types: Irritability or Excitability, Contractility, Extensibility, Elasticity

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Irritability or Excitability

The muscle property of being sensitive or responsive to chemical, electrical, or mechanical stimuli.

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The ability of muscle to contract & develop tension or internal force against resistance when stimulated.

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The ability of muscle to be passively stretched beyond its normal resting length.

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The ability of muscle to return to its original length following stretching.

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Muscle Terminology - Intrinsic

Pertaining usually to muscles within or belonging solely to the body part upon which they act.

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Muscle Terminology - Extrinsic

Pertaining usually to muscles that arise or originate outside of (proximal to) the body part on which they act.

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Muscle Terminology - Action

The specific movement of joint resulting from a concentric contraction of a muscle that crosses the joint.

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Muscle Terminology - Innervation

Occurs in the segment of the nervous system responsible for providing a stimulus to muscle fibers within a specific muscle or portion of a muscle.

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Muscle Terminology - Amplitude

The range of muscle fiber length between maximal & minimal lengthening.

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Muscle Terminology - Gaster (Belly or Body)

The central, fleshy portion of the muscle. This contractile portion of the muscle generally increases in diameter as the muscle contracts.

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Muscle Terminology - Tendon

Tough, yet flexible bands of fibrous connective tissue, often cordlike in appearance, that connect muscles to bones & other structures. By providing this connection, tendons transmit the force generated by the contracting muscle to the bone.

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Muscle Terminology - Aponeurosis

A tendinous expansion of dense fibrous connective tissue that is sheet- or ribbon-like in appearance and resembles a flattened tendon.

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Muscle Terminology - Fascia

A sheet or band of fibrous connective tissue that envelopes, separates, or binds together parts of the body such as muscles, organs, and other soft tissue structures of the body.

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Muscle Terminology - Retinaculum

A connective tissue band that tendons from separate muscles pass under in facial tissue.

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Muscle Terminology - Origin

The proximal attachment of a muscle or the part that attaches closest to the midline or center of the body.

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Muscle Terminology - Insertion

The distal attachment, or the part that attaches farthest from the midline or center of the body.

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Muscle Contractions (Action)

When tension is developed in a muscle as a result of a stimulus, it is known as a contraction. Can be used to cause, control, or prevent joint movement.

two types: Isometric Contractions & Isotonic Contractions

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Isometric Contractions

occurs when tension is developed within the muscle but the joint angles remain constant.

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Static Contractions

Isometric contractions (no movement)

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Isotonic Contractions

Involve the muscle developing tension to either cause or control joint movement.

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Dynamic Contractions

Isotonic contractions (movement)

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Muscle Contractions - Concentric Contraction

Involve the muscle developing active tension as it shortens & occur when the muscle develops enough force to overcome the applied resistance.

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Muscle Contractions - Eccentric Contraction (Muscle Action)

Involve the muscle lengthening under active tension and occur when the muscle gradually lessens in tension to control the descent of the resistance.

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Muscle Contractions - Movement Differentiation

Joint movement may occur with muscle groups on either or both sides of the joint actively contracting or even without any muscles contracting.

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Development of exercise machines has resulted in another type of muscle exercise.

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Role of Muscles - Agonist

When contracting concentrically, they cause joint motion through a specified plane of motion.

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Primary Movers

Muscles most involved

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Role of Muscles - Antagonist (Contralateral Muscles)

They work in cooperation with agonist muscles by relaxing & allowing movement; but when contracting concentrically, they preform the joint motion opposite to that of the agonist.

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Role of Muscles - Stabilizers (Fixators)

They surround the joint or body part & contract to fixate or stabilize the area to enable another limb or body segment to exert force & move.

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Role of Muscles - Synergist (Gliding Muscles)

Muscles that assist in the action of an agonist, but are not necessarily prime movers for the action, assist in refined movement & rule out undesired motion.

two types: Helping Synergists & True Synergists

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Helping Synergists

They help another muscle move the joint in the desired manner and simultaneously prevent undesired actions.

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True Synergists

They contract to prevent an undesired joint action of the agonist and have no direct effect on the agonist action.

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Role of Muscles - Neutralizers

They counteract or neutralize the action of other muscles to prevent undesirable movements such as inappropriate muscle substitutions. They contract to resist specific actions of other muscles.

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Role of Muscles - Force Couples

They occur when two or more forces are pulling in different directions on an object, causing the object to rotate about its axis.

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Reversal of Muscle Function

A muscle group described to perform a given function can contract to control the exact opposite motion.

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Determination of Muscle Action

Consideration of anatomical lines of pull, anatomical dissection, palpation, models, electromyography, & electrical stimulation.

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Muscle Action - Anatomical Lines of Pull

Description of force exerted by a muscle.

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Muscle Action - Anatomical Dissection

Looking at the muscle structures: determining their structural influence.

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Muscle Action - Palpation

A very useful way to determine muscle action; it is done through using the sense of touch to feel or examine a muscle as it contracts.

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Muscle Action - Models

Used to facilitate understanding of lines of pull & to stimulate muscle lengthening or shortening as joints move through various ranges of motion.

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Muscle Action - Electromyography (EMG)

Utilizes either surface electrodes that are placed over muscle or fine wire/needle electrodes placed into the muscle.

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Muscle Action - Electrical Stimulation

A reverse approach of electromyography; instead of electricity being used to detect muscle action, it is used to cause muscle activity.

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Lines of Pull

Combining the knowledge of a particular joint's functional design & diarthrodial classification with an understanding of the specific location of a musculotendinous unit as it crosses a joint is extremely helpful in understanding its action on the joint.

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Neural Control of Voluntary Movement

A result of the muscular & nervous systems working together.

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Central Nervous System (CNS)

Consists of the brain and spinal cord; may be divided into five levels of control.

five levels: the Cerebral Cortex, the Basal Ganglia, the Cerebellum, the Brain Stem, & the Spinal Cord

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CNS - The Cerebral Cortex

The highest level of control, provides for the creation of voluntary movement as aggregate muscle action but not as specific muscle activity.

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CNS - Basal Ganglia

Controls the maintenance of postures & equilibrium & learned movements; sensory integration for balance & rhythmic activities is controlled here.

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CNS - Cerebellum

A major integrator of sensory impulses & provides feedback relative to motion. It controls the timing & intensity of muscle activity to assist in the refinement of movements.

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CNS - Brain Stem

Integrates all CNS activity through excitation & inhibition of desired neuromuscular actions & funstions in arousal or maintaining a wakeful state.

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CNS - Spinal Cord

The common pathway between the CNS & the PNS. It has the most specific control & integrates various simple & complex spinal reflexes, as well as cortical & basal ganglia activity.

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Peripheral Nervous System (PNS)

Connects the brain and spinal cord to the muscles, organs, and senses in the periphery of the body; can be divided into two levels.

two levels: Sensory & Motor Divisions

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PNS - Sensory or __Afferent__Nerves

Bring impulses from receptors in the skin, joints, muscles, & other peripheral aspects of the body to the CNS.

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PNS - Motor or Efferent Nerves

Carry impulses to the outlying regions of the body.

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Spinal Nerves

Also provide both motor & sensory function for their respective portions of the body & are named for the locations from which they exit the vertebral column.

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A defined area of skin supplied by a specific spinal nerve.

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Muscle or group of muscles supplied by a specific spinal nerve.

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The basic units of the nervous system responsible for generating & transmitting impulses are nerve cells.

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Neuron Cell Body

Neurons consist of one or more branching projections.

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Transmit impulses to the neuron & cell body.

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An elongated projection that transmits impulses away form neuron cell bodies.

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Sensory (Afferent) Neurons

Transmit impulses to the spinal cord & brain from all parts of the body.

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Motor (Efferent) Neurons

Transmit impulses away from the brain and spinal cord to muscle and glandular tissue.

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Interneurons (Association Neurons)

Central or connecting neurons that conduct impulses from sensory neurons to motor neurons.

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Cervical Plexus


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Brachial Plexus


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Thoracic Plexus


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Lumbosacral Plexus


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Coccygeal Plexus


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Internal receptors located in the skin, joints, muscles, & tendons that provide feedback relative to the tension, length & contraction state of muscle, the position of the body & limbs, & movement of joints.

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The conscious awareness of the position & movement of the body in space.

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The subconscious mechanism by which body is able to regulate posture & movement by responding to stimuli originating in the proprioceptors embedded in the joints, tendons, muscles, & inner ear.

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Muscle Spindles

Sensitive to stretch & rate of stretch. Concentrated primarily in the muscle belly between the fibers.

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Myotatic or Stretch Reflex

When rapid muscle stretch occurs, an impulse is sent to the CNS & then the CNS activates motor neurons of muscle & causes it to contract.

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The Golgi Tendon Organs (GTO)

Continuously sensitive to muscle tension & active contraction. Located in the tendon close to the muscle-tendon junction.

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Pacinian Corpuscles

Ligaments & tendon sheaths & beneath the skin, are activated by rapid changes in the joint angle & by pressure changes affecting the capsule. Concentrated around joint capsules.

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Ruffini's Corpuscles

Activated by strong & sudden joint movements as well as pressure changes. Located in deep layers of the skin & the joint capsule.

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Meissner's Corpuscles & Krause's End-Bulbs

Receives stimuli from touch. Located in the skin & in subcutaneous tissues.

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Proprioceptive Feedback

The quality of movement & how we react to position change are significantly dependent upon this from the muscles & joints.

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Neuromuscular Junction (NMJ)

Synapse between the axon terminal of a motor neuron & the section of the membrane of a muscle fiber with receptors for the acetylcholine released by the terminal.

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Motor Unit

Consists of a single motor neuron & all the muscle fibers it innervates.

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All-or-None Principle

The individual muscle fibers within a given motor unit will fire & contract either maximally or not at all.

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Muscle Fiber Types

two catagories: Fast Fibers & Slow Fibers

three types: Type IIa & Type IIb, which are fast fibers, & Type I, which is a slow fiber

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Fast Fibers

Can produce greater forces due to a greater shortening velocity but fatigue more quickly.

two types: Type IIa & Type IIb

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Slow Fibers

Has a greater resistance to fatigue, but generally produce less tension.

one type: Type I

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Action Potential (AP)

For the muscle fibers in a particular motor unit to contract, the motor unit must first receive a stimulus via an electrical signal.

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Subthreshold Stimulus

If the stimulus is not strong enough to cause an action potential.

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Threshold Stimulus

When the stimulus becomes strong enough to produce an action potential in a single motor unit axon.

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