Kinesiology Unit 3

What are two common shapes of a whole muscle?

\-Fusiform

\-Pennate

In fusiform muscles the fibers run?

Parallel

What are examples of fusiform muscles?

Biceps, triceps, pectoralis

In pennate muscles the fibers do what?

Approach the central tendon obliquely

Pennate muscles form?

A common angle with the tendon

What are examples of pennate muscles?

Rectus femoris, deltoids, gastrocnemius

What is a pennation angle?

Refers to the angle of orientation between muscle fibers and tendon

If fibers are parallel to the tendon, what is the pennation angle?

0

If the pennation angle is greater than 0, what happens to the force transmitted to the tendon?

There is less force transmitted to the tendon

30 degrees transmits how much force transmitted to the tendon?

86%

In general, do fusiform or pennate muscles produce greater maximum force?

Pennate

Why does a pennate muscle produce greater maximal force than a fusiform muscle?

Oblique arrangement fits more fibers into a given length of muscle

What is the range of thickness for muscle fiber?

10 to 100 micrometers

What is the range in length of a muscle fiber?

1 to 50 cm

Each muscle fiber is a cell with?

Multiple nuclei

Connective tissue is within the muscles and consists of fibers embedded in what that provides shock absorption?

Ground substance

Most fibers for connective tissue are?

Collagen and the remaining are elastin

What are the three different connective tissues that occur in muscles?

\-Epimysium (On top)

\-Perimysium (Surrounding)

\-Endomysium (Within)

What is epimysium?

A tough structure that surrounds the entire muscle belly

Epimysium contains?

Collagen fibers

Epimysium is highly resistive to?

Stretch

Perimysium lies where?

Under the epimysium

Perimysium does what?

Divides the muscle into fascicles that provide a conduit for blood vessels and nerves

Perimysium is resistive to what?

Stretch, it is tough

Endomysium surrounds what?

Individual muscle fibers

Endomysium is composed of what?

Dense collagen fibrils that are partly connected to the perimysium

Endomysium does what?

Conveys the contractile force to the tendon

What is physiologic cross-sectional area (PCSA)?

Reflects the amount of contractile protein available to generate force

Cross sectional area of fusiform muscle is determined by what?

Dividing the muscle’s volume by its length

A fusiform muscle with thick fibers has what kind of cross sectional are?

Greater

Maximal force potential of a muscle is proportional to what?

The sum of the cross-sectional are of all the fibers

PSCA and length are proportional to?

Muscle strength

What is the most important characteristic of a muscle?

Its ability to develop tension and to exert force on the bony lever

Tension can be either?

Active or passive

The total tension that a muscle can develop includes?

Both active and passive components

Active tension is developed by?

The contractile elements of the muscle

Active tension is initiated by?

The cross bridge formation of movement of the actin and myosin

With active tension, tension may be increased by?

Increasing the firing of a motor unit or increasing the number of motor units that are firing

With Active Tension recruitment occurs when?

The muscle is stressed by increasing the load or speed requirements of a movement or when the muscle begins to tire

In active tension, why do muscle fibers of repeatedly recruited motor units hypertrophy?

In response to increased resistance or load, thereby increasing strength

Passive tension is developed in?

The non-contractile components of the muscle (connective tissues, tendons)

Connective tissues generate a resistive force when elongated why?

They are slightly elastic like a rubber band

What is parallel elastic component?

Connective tissues that surround or lie parallel to the contractile proteins that cause a muscle to contract

What is series elastic component?

Connective tissues within the tendon

Stretching of a muscle elongates both generating a spring like resistance. What tension is that resistance?

Passive

What is length tension?

Direct relationship between tension development in a muscle and the length of a muscle

What is the optimal length for developing tension?

Approximately the resting length of a muscle (length when detached from bone)

In the optimal length for developing tension, actin and myosin filaments are positioned so?

The maximum number of cross bridges can be formed

If the muscle is lengthened or shortened beyond optimal length, what happens to the amount of tension the muscle is able to generate?

It diminishes

The body unconsciously learns to place muscles at their optimal length for?

Maximum tension development

Muscles are able to generate moderate tension in what range?

Lengthened

Muscles are able to generate maximum tension in what range?

Middle of the contractile range

Muscles are able to generate minimal tension in what range?

Shortened range during a concentric or active shortening contraction

What is active insufficiency?

The diminished ability of a muscle to produce or maintain active tension (muscles cannot relax or shorten anymore)

What does it mean when a muscle is on slack?

The muscle is shortened to a point at which no further sliding of the filaments can take place

Muscles that cross more than one joint may reach what prior to attainment of full ROM at all of the joints crossed by the muscle?

Maximum elongation or shortening

Skeletal muscles contribute to what?

Mobility and stability

How can muscle forces have a rotary or mobility function?

By producing or controlling the movement of a bony lever around a joint axis

How can muscle forces have a stability function?

Through translatory movement of the bones in a joint which is joint compression or approximation and by resisting movement

Skeletal muscles help to move the joints into and out of?

Close-packed and loose-packed positions

When does a close-packed position happen?

At the end of range (elbow extension)

When does a loose packed position happen?

Somewhere along range of motion

When a joint is in a close-packed position, what happens to the stability role of the muscle?

It is decreased because the ligaments and joint capsule are tat and support the joint

When a joint is in a loose-packed position, the muscles have a larger role in providing what?

Stability because the passive supporting structures are slacker

What are the types of muscle action?

Concentric

Isometric

Eccentric

Isotonic

Isokinetic

What is concentric contraction?

Shortening contraction-the muscle pulls both ends, its attachments on the bones towards the center of the muscle belly.

What is isometric contraction?

Constant length, there is no visible change in the muscle length and no movement of either bony attachment.

Is there observable movement of the bones in isometric contraction?

No, because they are fixed in a still position but there is a crossbridge formation to produce tension in the muscle

What is isometric contraction known as?

Static contraction

What is eccentric contraction?

Lengthening of the muscle while it is active or tense

During eccentric contraction the muscle acts as a?

Brake and controls the movement of bones as the two attachments move further apart

What is isotonic contraction?

Same or constant tension throughout contraction

What do some researchers claim in regards to isotonic contraction?

An exact equality of tension can only occur in detached muscles, dissected out from the body, lifting vertically against gravity. It is un-psychological and does not occur in the live human body.

Clinically, the term isotonic contraction is used to mean what?

Any muscle contraction that produces movement

What is isokinetic contraction?

Same or constant velocity, occurs when the speed of movement of the bone is kept constant through the ROM by a mechanical device

Muscles are classified on?

Basis of function

What are the classifications of muscles?

Flexors

Extensors

Rotators

Abductors

Adductors

Muscles can be categorized according to?

The major role of the muscles in producing the movement

What are the three categorizations of muscles based on producing movement?

Agonist

Antagonist

Synergist

Define agonist?

Our main or primary mover, the muscle that tends to do most of the action, oftentimes the muscle that is concentrically contracting

Antagonists are the ones that have what kind of movement?

Opposite

What are synergists?

Muscles that do the same movement at the same time, usually working together

What is reciprocal inhibition?

When an agonist is performing a desired motion, the antagonist is relaxed or inhibited

What is co-contraction?

When the agonist and the antagonist contract simultaneously. This can help provide stability for the joint and is a type of synergy that is helpful in certain situations

What are the subtypes of synergists?

Neutralizing or counteracting synergists

Conjoint synergists

Stabilizing or fixating synergists

What is a neutralizing synergist?

Muscles that may contract to prevent unwanted movements produced by the prime mover

What is a conjoint synergist?

When two or more muscles work together to produce the desired movement, the muscle contracting alone would be unable to make the movement

What is a stabilizing synergist?

Muscles may stabilize or fix a joint proximal to the moving joint to provide a stable base from which the distal moving segment can work

What are muscle spindles?

Small, spindle shaped sensory organ that senses the changes in length of the muscle and rate of lengthening

Do muscle spindles contract?

Yes

What is the sense of muscle spindles?

The lengthening of the muscle and the rate of lengthening of the muscle

What is the protective function of muscle spindles?

Stretch reflex and reciprocal inhibition, protect muscles

What are muscle spindles composed of?

Differentiated muscle fibers that are enclosed in a spindle-shaped connective tissue sac

What is a golgi tendon?

A sensory organ in the muscle tendon unit that senses the changes in the muscle tension

Do golgi tendon organs contract?

No

What do golgi tendons sense?

Tension in the tendon

What is the protective function of the golgi tendon?

Autogenic inhibition

What are golgi tendons comprised of?

Braided strands of collagen which are encapsulated

What is autogenic inhibition?

The ability of a muscle to relax when it experiences a stretch or increased tension

In autogenic inhibition reflex relaxation occurs in?

The same muscle