Chapter 2 Kinesiology

myotome

a muscle or group of muscles supplied by a specific spinal nerve

axon

an elongated projection that transmits impulses away from neuron cell bodies

Interneurons

are central or connecting neurons that conduct impulses from sensory neurons to motor neurons

Sphincter or circular muscles

are technically endless strap muscles that surround openings and function to close them upon contraction. An example is the orbicularis oris, surrounding the mouth.

dermatome

defined area of skin supplied by a specific spinal nerve

brain stem

integrates all central nervous system activity through excitation and inhibition of desired neuromuscular actions and functions in arousal or maintaining a wakeful state.

Concentric contractions

involve the muscle developing active tension as it shortens, whereas eccentric contractions involve the muscle lengthening under active tension

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

Spinal nerves

provide both motor and sensory function for their respective portions of the body and are named for the locations from which they exit the vertebral column. From each side of the spinal column, there are 8 cervical nerves, 12 thoracic nerves, 5 lumbar nerves, 5 sacral nerves, and 1 coccygeal nerve

Location

rectus femoris, palmaris longus, shoulder girdle

Fascia

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

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. Examples are the brachialis and the brachioradialis.

cervical plexus

supplies motor innervation to several muscles of the neck

Extensibility

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

Contractility

the ability of muscle to contract and develop tension or internal force against resistance when stimulated.

Elasticity

the ability of muscle to return to its original resting length following stretching.

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. When a particular muscle contracts, it tends to pull both ends toward the gaster, or middle, of the muscle.

spinal cord

the common pathway between the CNS and the peripheral nervous system (PNS)

Kinethesis

the conscious awareness of the position and movement of the body in space. ex. kicking a ball

cerebral cortex

the highest level of control, provides for the creation of voluntary movement as aggregate muscle action but not as specific muscle activity. Sensory stimuli from the body also are interpreted here, to a degree, for the determination of needed responses

Irritability or excitability

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

biarticular

those that cross and act directly on two different joints.

uniarticular

those that cross and act directly only on the joint that they cross (brachialis of the elbow pulling humerus concentric)

motor neurons

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

Sensory neurons

transmit impulses to the spinal cord and brain from all parts of the body

Radiate muscles

triangular, fan-shaped, or convergent. They have the combined arrangement of flat and fusiform muscles, in that they originate on a broad surface or an aponeurosis and converge onto a tendon. Examples include the pectoralis major and trapezius.

Number of divisions

triceps brachii, QUADRICEPS

Flat muscles

usually thin and broad, originating from broad, fibrous, sheetlike aponeuroses that allow them to spread their forces over a broad area. Examples include the rectus abdominis and external oblique.

Action

Action is the specific movement of the joint resulting from a concentric contraction of a muscle that crosses the joint. An example is the biceps brachii, which has the action of flexion at the elbow.

Agonist

Agonist muscles, when contracting concentrically, cause joint motion through a specified plane of motion. Any concentrically contracting muscle that causes the same joint motion is an agonist for the motion

muscle actions

All muscle contractions or actions can be classified as either isometric or isotonic

Other nerves (not cervical or thoracic)

All of the lumbar, sacral, and coccygeal nerves form the lumbosacral plexus, which supplies sensation and motor function to the lower trunk and the entire lower extremity and perineum.

Isokinetics

Isokinetics is not another type of contraction, as some authorities have mistakenly described; rather, it is a specific technique that may use any or all of the different types of contractions. Isokinetics is a type of dynamic exercise usually using concentric and/or eccentric muscle contractions in which the speed (or velocity) of movement is constant and muscular contraction (ideally, maximum contraction) occurs throughout the movement

Concurrent

Movement pattern allowing the involved biarticular muscle to maintain a relatively consistent length because of the same action at both of its joints.

Synergist

Muscles that assist in the action of an agonist but are not necessarily prime movers for the action, known as guiding muscles, assist in refined movement and rule out undesired motion. Synergist muscles may be either helping synergists or true synergists.

the motor or efferent nerves

Nerves that carry impulses to the outlying regions of the body from the central nervous system.

dendrites

Neurons consist of a neuron cell body; one or more branching projections known as dendrites, which transmit impulses to the neuron and cell body

Neutralizers

Neutralizers 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. As an example, when only the supination action of the biceps brachii is desired, the triceps brachii contracts to neutralize the flexion action of the biceps brachii.

Stabilizers

Stabilizers surround the joint or body part and contract to fixate or stabilize the area to enable another limb or body segment to exert force and move; essential in establishing a relatively firm base for the more distal joints to work from when carrying out movements

passive insufficiency

State reached when an opposing muscle becomes stretched to the point where it can no longer lengthen and allow movement.

subthreshold stimulus

Stimulus not strong enough to cause an action potential and therefore does not result in a contraction.

Insertion

Structurally, the distal attachment, or the part that attaches farthest from the midline or center of the body, is considered the insertion. Functionally and historically, the most movable part is generally considered the insertion.

neuromuscular junction

connection between the nervous system and the muscular system via synapses between efferent nerve fibers and muscle fibers

motor unit

consists of a single motor neuron and all the muscle fibers it innervates but it functions as a single unit

basal ganglia

control the maintenance of postures and equilibrium and learned movements such as driving a car. Sensory integration for balance and rhythmic activities is controlled here.

Shape

deltoid, rhomboid HAMSTRINGS

Action

erector spinae, HIP FLEXOR, ROTATOR CUFF

Point of attachment

extensor hallucis longus

Direction of fibers

external abdominal oblique

Bipennate muscle

fibers run obliquely from a central tendon on both sides, as in the rectus femoris and flexor hallucis longus. (strongest contractions)

Unipennate muscle

fibers run obliquely from a tendon on one side only. Examples are seen in the biceps femoris, extensor digitorum longus, and tibialis posterior.

Cervical nerves 5 through 8, along with thoracic nerve 1

form the brachial plexus, which supplies motor and sensory function to the upper extremity and most of the scapula.

Cervical nerves 1-4

form the cervical plexus, which is generally responsible for sensation from the upper part of the shoulders to the back of the head and front of the neck.

Size

gluteus maximus, teres minor

Pennate muscles

have shorter fibers that are arranged obliquely to their tendons in a structure similar to that of a feather. This arrangement increases the cross-sectional area of the muscle, thereby increasing its force production capability. Pennate muscles are categorized on the basis of the exact arrangement between the fibers and the tendon

Parallel muscles

have their fibers arranged parallel to the length of the muscle, will produce a greater range of movement than similar-size muscles with a pennate arrangement

angle of pull at 90 degrees

100% of the force is contributing to the movement

Isometric

An isometric contraction occurs when tension is developed within the muscle but the joint angles remain constant. Isometric contractions may be thought of as static contractions, because a significant amount of active tension may be developed in the muscle to maintain the joint angle in a relatively static or stable position. Isometric contractions may be used to stabilize a body segment to prevent it from being moved by external forces. Isotonic contractions involve the muscle developing tension to either cause or control joint movement. The isotonic type of muscle contraction is classified further as either concentric or eccentric on the basis of whether shortening or lengthening occurs.

Antagonist

Antagonist muscles have the opposite concentric action from agonists. Referred to as contralateral muscles, antagonists are located on the opposite side of the joint from the agonist and work in cooperation with agonist muscles by relaxing and allowing movement

Eccentric contraction (muscle action)

Eccentric contractions involve the muscle lengthening under active tension and occur when the muscle gradually lessens in tension to control the descent of the resistance. The weight or resistance may be thought of as overcoming the muscle contraction, but not to the point that the muscle cannot control the descending movement.

action potential

Electrical signal transmitted from the brain and spinal cord through axons to the muscle fibers in a particular motor unit providing the stimulus to contract.

Proprioception

Feedback relative to the tension, length, and contraction state of muscle, the position of the body and limbs, and movements of the joints provided by internal receptors located int he skin, joints, muscles and tendons

Force couples

Force couples occur when two or more forces are pulling in different directions on an object, causing the object to rotate about its axis. Fig. 2.4, A depicts a force couple consisting of one hand on each side of a steering wheel. One hand pulls the wheel up and to the right, and the other hand pulls it down and to the left.

Origin

From a structural perspective, the proximal attachment of a muscle or the part that attaches closest to the midline or center of the body is usually considered to be the origin. From a functional and historical perspective, the least movable part or attachment of the muscle has generally been considered to be the origin.

Helping synergists

Helping synergists have an action in common but also have actions antagonistic to each other. They help another muscle move the joint in the desired manner and simultaneously prevent undesired actions. An example involves the anterior and posterior deltoid. The anterior deltoid acts as an agonist in glenohumeral flexion, while the posterior deltoid acts as an extensor. Helping each other, they work in synergy with the middle deltoid to accomplish abduction.

Retinaculum

In certain places throughout the body, such as around joints like the wrist and ankle, fascial tissue forms a retinaculum to retain tendons close to the body.

Extrinsic

Pertaining usually to muscles that arise or originate outside of (proximal to) the body part on which they act. The forearm muscles that attach proximally on the distal humerus and insert on the fingers are examples of extrinsic muscles of the hand.

Intrinsic

Pertaining usually to muscles within or belonging solely to the body part on which they act. The small intrinsic muscles found entirely within the hand are examples

active insufficiency

Point reached when a muscle becomes shortened to the point that it cannot generate or maintain active tension.

peripheral nervous system (PNS)

Portion of the nervous system containing the sensory and motor divisions of all the nerves throughout the body except those found in the central nervous system.

all or none principle

Regardless of the number involved, the individual muscle fibers within a given motor unit will fire and contract either maximally or not at all.

passive tension

Tension in muscles that is due to externally applied forces and is developed as a muscle is stretched beyond its normal resting length.

Active tension

Tension in muscles that is generated via an active contraction of the respective muscle fibers in that muscle.

Amplitude

The amplitude is the range of muscle fiber length between maximal and minimal lengthening.

central nervous system (CNS)

The cerebral cortex, basal ganglia, cerebellum, brain stem, and spinal cord.

Myotatic or stretch reflex

The reflexive contraction that occurs as a result of the motor neurons of a muscle being activated from the CNS secondarily to a rapid stretch occurring in the same muscles; the knee jerk

True synergists

True synergists contract to prevent an undesired joint action of the agonist and have no direct effect on the agonist action. The finger flexors are provided true synergy by the wrist extensors when one is grasping an object. The finger flexors originating on the forearm and humerus are agonists in both wrist flexion and finger flexion. The wrist extensors contract to prevent wrist flexion by the finger flexors. This allows the finger flexors to maintain more of their length and therefore utilize more of their force in flexing the fingers.

muscle fibers

When a particular muscle contracts, the contraction actually occurs at the muscle fiber level within a particular motor unit

threshold stimulus

When the stimulus is strong enough to produce an action potential in a single motor unit axon and all of the muscle fibers in the motor unit contract.

cerebellum

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

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

Tendon

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

The sensory or afferent nerves

bring impulses from receptors in the skin, joints, muscles, and other peripheral aspects of the body to the CNS

strap muscles

more uniform in diameter with essentially all their fibers arranged in a long parallel manner. This also enables a focusing of power on small, bony targets. The sartorius is an example

Treppe

muscle contraction that occurs when multiple maximal stimuli are provided to a rested muscle at a low enough freq to allow relax between

Multipennate muscle

muscles have several tendons with fibers running diagonally between them, as in the deltoid. (strongest contractions)

Primary movers

muscles that contribute significantly more to the joint movement than other agonists

Aggregate muscle action

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