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96 Cards in this Set

  • Front
  • Back

What is another name for a muscle cell?

Muscle Fiber

What is a fascicle or fasicula?

A bundle of 6-12 muscle fibers

A. What CT surrounds a muscle fiber?


B. What CT surrounds a fascicle?


C. What CT surrounds the whole muscle?

A. Endomysium


B. Perimysium


C. Epimysium

Define Sarcomere

The smallest functional unit of muscle composed of repeating patterns of myofilaments: thin filaments (actin) and thick filaments (myosin).

A. Z Disc


B. H zone


C. Z Disc


D. I Band


E. A Band


F. Sarcomere


G. (not pictured): M line = center of H Zone

Which parts of the Sarcomere shorten during contraction and which are fixed?

The H zone and I band shortens (HI) and the Z disc and A bands are fixed.

What is a Myofibril?

A series of sarcomeres. Myofibrils make up a muscle fiber.

A. Define Motor Unit


B. How does it fire?

A. Each alpha motor neuron and all the skeletal muscle fibers it innervates.


B. Fire in a "all-or-none" fashion.

Length-Tension Relationship

Think of arm wrestling. 1.65um sarcomere is completely contracted (cannot contract further). 3.65um is completely extended (cross bridging cannot occur). The Ideal length for contraction is 2.25um.

Where are motor neurons located in the spinal cord?

Ventral Horn

Define Muscle Fatigue

a decrease in the muscle's ability to generate force. Fatigue is caused by a reversible depletion of the muscle's fuel supply. If certain waste products (metabolites) are not removed at an adequate rate, they accumulate and hasten the onset of fatigue.

What is asynchronous recruitment?
When the nervous system modulates the firing rates of motor neurons so that different motor units take turns maintaining muscle tension. The alteration of active motorunits allows some of the motor units to rest between contractions and prevents fatigue.

What are the 5 characteristics of muscle tissue?

Excitability, contractility, relaxation, extensibility, and elasticity?

In response to internal and external forces, skeletal muscles perform what three actions?

1. Generate movement


2. Arrest movement


3. Modify movement

Active vs. Passive Muscle Force

Active = muscles shorten and build up tension


Passive = muscles resist stretch

Rotary vs. translatory movements?

Rotary movements occur around an axis. Translatory movements occur when all parts move together from one place to another in a straight line.

Which C.T.'s surround the muscle tendon?

It receives contributions from all muscle C.T. layers (Endomysium, perimysium, and epimysium).

What type of tension is transmitted to muscles via tendons?

passive tension

What are the passive elastic components of muscle?

C.T., Tendons, sarcolemma, nerves, and blood vessels.

Tension is developed whenever ______ are formed

Crossbridges

What is spatially needed between the actin and myosin myofilaments for crossbridges to form?

overlap

When has a sarcomere achieved maximum crossbridges?

When there is maximum overlapping of the myofilaments

What movement happens between the actin and myosin during shortening contractions?

The actin is pulled towards the myosin into the H zone.

What movement happens between the actin and myosin during lengthening contractions?

The actin pulls away from the myosin out of the H zone.

What is the structure and function of a fusiform muscle? Give an example.

Muscle fibers are long and parallel which provides the greatest degree of shortening ability thus enabling quick movements and a wide range of motion. An example is the biceps brachii.

What is the structure and function of a penniform muscle? Give an example.

Muscle fibers are generally shorter and in an oblique (angled) arrangement which allows for greater force and a smaller range of motion. The rectus femoris is an example

What are other names for for Red (tonic) fibers?

Type I, slow oxidative, slow twitch

What are other names for for Pale (phasic) fibers?

Type IIa, IIb, fast twitch, glycolic

Which muscle fiber type has a lower nerve signal threshold? What does this mean?

Slow Oxidative or Red (tonic) fibers. They are used more frequently.

Where are SO or Red (tonic) fibers more prevalent?

Postural muscles

Consider the calf muscles. Which type of muscle fibers would be most prevalent in the soleus? Which type would be most prevalent in the gastrocnemius?

The soleus contains mostly SO/red (tonic)/type I fibers and is used for stability in the ankle. The gastrocnemius contains mostly FOG/pale (phasic)/type II fibers and is used in plantar flexion.

What determines the strength of a muscle twitch?

The size of a motor unit being stimulated.

What are the three periods of a muscle twitch?

1. Latent (impulse travels along sarcolemma, calcium is being released, no contraction has occurred)


2. Contraction (crossbridges form)


3. Relaxation (contractile force is no longer generated, muscle returns to its original length).

Are muscle fibers in a motor unit grouped or disbursed in a muscle?

Disbursed.

Motor units are made up of one or multiple muscle fiber types?

One type

What five features determine the magnitude of active tension?

1. Size of motor units firing


2. Number //


3. Frequency of their firing


4. Number of crossbridges occurring


5. Load on the muscle

Another name for proximal attachment is

Origin

Another name for distal attachment is

Insertion

What 3 things make up the line of pull?

1. The direction of the fibers

2. The proximal and distal attachments


3. The position of the muscle relative to the joint (i.e., anterior, posterior, etc.)

Muscle action

the development of tension (force) by a muscle

Functional Muscle Group

A group of muscles that are capable of causing a specific joint action (e.g., wrist radial deviators)

Motive force

Force causing the observed movement (agonists)

Resistive force

force opposing the observed movement (antagonists)

Agonist or prime mover

muscle or group of muscles that produces the desired motion

Accessory or assist (emergency muscle)

A muscle that assists the prime mover. It is less effective at this motion (e.g., biceps can help produce shoulder flexion but is not the prime mover of shoulder flexion).

Antagonist

Produces the opposite action of the prime mover

Stabilizer or fixator

Muscle contracts isometrically to hold a body part immobile or stable against the pull of another contracting muscle (e.g., quadriceps during knee extension and plantar flexion).

Neutralizer

A muscle contracts to prevent an unwanted movement component in another muscle (neutralizers cancel unwanted motions). Example: pronator teres neutralizes biceps brachii during flexion if no supination is wanted.

Spurt muscle

Rotary muscles. Proximal attachment is far from the joint axis. Distal attachment and muscle belly is close to the joint axis. Example: biceps brachii (elbow flexor).

Shunt Muscle

Stabilizing muscles (translatory component). Proximal attachment and muscle belly is close to the joint axis. Distal attachment is far from the joint axis. Example: brachioradialis (supinator).

Spurt-shunt muscle

Multi-joint muscles like the biceps brachii can act as a spurt muscle on one joint (elbow) but as a shunt muscle on another joint (shoulder).

Isometric Contraction

"Same length" contraction. Muscle is held in a shortened position.

Concentric contraction

muscle shortens and develops enough tension to overcome the resistance of the body part and gravity.

Eccentric

A lengthening contraction. From a shortened position, a muscle gradually returns to resting length. Often used to control movements against gravity.

Co-contraction

Agonist and antagonist muscles contract simultaneously to provide stability (as in holding your wrist in neutral position).

Reverse action of muscles

When the origin moves towards the insertion (often occurs when the distal segment is in a closed kinematic chain as in with the biceps while doing a chin-up).

Active insufficiency

Inability of a muscle to shorten enough to cause full range of motion

Passive insufficiency

Inability of the inactive components (passive tissue) in the antagonist to stretch enough to allow full range of motion at joints being moved the agonist.

Tenodesis

when the passive tension in a muscle contains enough passive insufficiency that it causes the tendon to exert pull on the bone. It usually occurs in the presence of active insufficiency.

What is the membrane called that surrounds a muscle cell?

Sarcolemma

What is the cytoplasm of a muscle fiber called?

Sarcoplasm

What are myofilaments?

Actin and myosin.

What is a myofibril?

A series of sarcomeres.

Periosteum

A highly vascularized C.T. that is the outer layer of the bone. Tendons and ligaments blind into it. It provides nourishment to the bone.


When does the passive elastic component contribute passive tension to a muscle?

When the muscle shortens and when it elongates.

Compare diameter and motor unit size for FG and SO fibers

FG motor unit and diameter is large. SO motor unit and diameter is small.

Exteroceptors

Sensory neurons that detect sensation from the surface of the body

Proprioceptors

Sensory neurons that detect location of the body through muscles (muscle spindle), tendons (golgi tendon organ), and the vestibular apparatus of the ear.

Interoceptors

Sensory neurons that detect sensation from the viscera of the body.

Which horn of the spinal cord are the sensory neurons located in?

The dorsal or posterior horn.

CNS Muscle Recruitment Strategies

1) Small cell bodies from small motor units are recruited first for less energy expenditure


2) Large size motor units are recuirted next


3) Other factors: habituation, magnitude of force needed, speed needed, type of muscle contraction needed, type of fibers needed.

Internal active tension

The tension created by the contractile elements of the muscle

Total tension

the combination of the contractile (active) tension and elastic (passive) tension structures.

Muscle synergy

Several muscles that are called upon to perform a joint motion (including the prime mover, emergency muscles, fixators, neutralizers, etc.). Synergistic muscles are also considered to produce similar joint activity.

Factors affecting muscle function

1. Anatomical structure of the joint over which the muscle passes


2. Location of the muscle relative to the joint


3. Point of attachment of the muscle in relationship to the joint


4. Opposing strength of agonists and antagonists


5. Single vs. multi-joint muscles


6. Efficiency Principle

What are multi-joint muscles?

Muscles that cross over two or more joints.

Which joints can a muscle produce movement in?

Every joint it passes

When the body of the muscle is proximal to a joint it moves it is what kind of muscle? What about when it is distal?

Spurt when it is proximal (biceps brachii), shunt when it is distal (brachioradialis).

The type of movement the muscle will produce at a particular joint is primarily dependent on what two things?

The type of joint and the muscle's position in relationship to that joint

What is a neuromusculoskeletal unit

the skeletal muscle, its motor unit, its bones and joints.

Postural movements

Holding still

Ballistic movements

movements with brief contraction times, high rates of force that, once initiated, the movement continues on its own momentum.

Tension movements

require constant muscular contraction throughout the range of movement. Include slow tension movements (e.g., singing your name) and fast tension movements (e.g., a boxing jab).

2 components of gradation of muscle contractions

1) Number of motor units contracting


2) (twitch) Summation

Contractile force is determined by which 2 features

1) size (cross-sectional measurement) of muscle


2) proportion of active fibers

Endurance is based on what 3 factors

1) contractile force (strength of muscle)


2) efficiency of the circulorespiratory system


3) nervous system

Anaerobic exercises leads to what modifications of muscle fibers?

Conversion to fast twitch (FG) fibers and longitudinal splitting

What type of exercises are isometric exercises?

Anaerobic

Muscles immobilized in a shortened or lengthened position experience fewer structural and functional changes?

lengthened position

What are the three effects of aging on muscles?

1) an increase in the concentration of C.T. within the muscle belly resulting in stiffness


2) Muscles are less able to respond to resistance training


3) There is a decrease in the number of Type II muscle fibers

Muscular dystrophy is what type of muscle disorder? What characterizes this disorder?

Disease of the skeletal muscles. Myopathic disorders that have in common the progressive degenration of muscle fibers. Neuronal innervations and sensation remain intact.

Guillian Barre Syndrome and Myasthenia Gravis are an example of what kind of disorder? What characterizes this disorder?

Neuromusclar disroder. They are a result of the interruption between the muscles and the nerves that innervate them at the myoneural junction or spinal nerve root.

Cerebral Palsy, cerebral vascular accident, multiple sclerosis, TBI are what kind of disroders? What characterizes this disorder?

Neurologic Disorders. They are rooted in pathology of the supraspinal structures, upper motor neurons, and the spinal cord. They result in paralysis and/or abnormal patterns of movement.

Systemic Lupus Erythematosus and Fibromyalgia are what type of disorder? What characterizes this disorder?

Diseases of the C.T. They effect the funcitoning of the muscle due to problems related to surrounding and parallel C.T. Other examples include sprains, bursitis and tendonitis.

Contracture

A pathological shortening of a muscle which may be functional or organic in genesis. As a result of the muscle being immobilized or unable to return to its full stretch, it assumes a new resting position. It often occurs due to imbalance between antagonistic muscle groups around a joint.

How is a contracture described?

It is described in terms of the direction of the shortened muscles (e.g., flexion contracture).