Muscular System

http://www.human-body-facts.com/muscular-system.html

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The muscular system makes up nearly half the weight of the human body, this is why when we train we sometimes put on weight instead of losing it. We put on muscle weight.

The muscles provide the forces that enable the body to move.

The muscular system

http://www.biology4kids.com/files/systems_muscular.html

The big purpose of the muscles found in your body is movement. We could be talking about the movement of your legs while you walk. We could be talking about the beating of your heart. We could also be talking about the contraction of a very small blood vessel in your brain. 

WHAT DOES THIS SYSTEM DO?

The main parts of your voluntary muscular system include the muscles, and tendons. The muscle is called the meatus. The bicep is the meat that connect to the bones so that you can move. Tendons connect your muscles to your bone at insertion points. 

MUSCLES HELP YOU MOVE

You have no control over most of the muscular system. You do control the voluntary muscle in your arms, legs, neck, and torso. You have little or no control over the heart or smooth muscle. Those other muscles are under the control of the autonomic nervous system (ANS). 

The muscular system is closely connected to the nervous system. You usually have to think before you can move. Even though thinking is not always involved, the neurons of the nervous system are connected to most of the cells in your muscular system.

INTERACTING WITH OTHER SYSTEMS

Muscles stretch across joints to link one bone with another and work in groups to respond to nerve impulses.

There are three types of muscle:

Our muscle structure consists of densely packed groups of elongated cells known as muscle fibres.

Skeletal muscle is composed of bundles of long striated fibres.

Muscle Structure

Smooth muscle which is found in the walls of internal organs such as intestines is made of short spindle-shaped fibres packed together in layers.

Cardiac muscle found only in the heart has short interconnecting fibres.

There are nearly 650 skeletal muscles in the human body! Skeletal muscles are attached to the skeleton. They work in pairs: one muscle moves the bone in one direction and the other moves it back again.

Skeletal muscle

Skeletal muscles are voluntary muscles - in other words we think about what movements we want to make (at least, usually!) and send messages via our nervous system to tell the appropriate muscle(s) to contract. 

Muscle contractions can be short, single contractions or longer ones.  

Skeletal muscle carries out voluntary movements, and is what we use for movement in daily life and during exercise.  The human body has more than 650 muscles, the body's most abundant tissue, comprising about 23% of a woman's body weight and about 40% of a man's body weight.

Smooth muscle is found in our internal organs: in our digestive system, our blood vessels, our bladder, our respiratory organs and, in a female, the uterus.

Smooth muscle can stretch andmaintain tension over extended periods.

Smooth muscle 

These fibres are held together by fibrous connective tissue.

Capillaries penetrate this tissue to keep the muscles supplied with oxygen and nutrients that are needed to fuel contraction.

In a relaxed muscle the thick and thin threads within a muscle fibre overlap a little.

When a muscle contracts, the thick filaments slide further in between the thin filaments like interlacing fingers. This action shortens the entire fibre.

Cardiac muscle is found only in the heart. It can stretch, just like smooth muscle, and contract like skeletal muscle.

It is a twitch muscle - it only does short single contractions.

Like smooth muscle, cardiac muscle is involuntary.

Cardiac muscle

Smooth muscles are involuntary muscles - in other words we do not have to think about contracting them because they are controlled automatically by the nervous system.

Smooth muscle surrounds or is part of the internal organs.  Smooth muscle is found in the digestive system, blood vessels, bladder, airways and, in a female, the uterus.  It has the ability to stretch and maintain tension for long periods of time.  Both cardiac and smooth muscles are called involuntary muscles, because they cannot be consciously controlled. 

You have smooth muscles that line your digestive system and help move food through your intestines. Smooth muscle also surrounds your circulatory system and lymph system. Those muscle tissues are spread throughout your body and are even involved in controlling the temperature of your body. 

The stomach is an organ of the alimentary canal, a muscular tube that forms part of the digestive system.  

The wall of the stomach contains smooth muscle tissue.  

 Contractions of the smooth muscles of the alimentary canal serve to mix food with digestive juices, and to move the resulting mixture further along (peristalsis).  Smooth muscles are called involuntary muscles, because they cannot be consciously controlled.

 Skeletal muscles can do a short, single contraction (twitch) or a long, sustained contraction (tetanus), and might ache after strenuous exercise. A skeletal muscle is composed of skeletal muscle tissue, nervous tissue, blood, and connective tissues.  Fascia covers the surface of the muscle and also forms the cordlike tendons which attach the muscle to the bone.

 Epimysium lies beneath the fascia, and perimysium extends into the structure of the muscle, where it separates muscle tissue into small compartments of bundles of skeletal muscle fibers called fascicles.  Endomysium separates individual muscle fibers within those fascicles.

Anatomy of Skeletal Muscle

According to the sliding filament theory, myosin cross-bridges attach to a binding site on the actin filament and bend slightly, thus pulling on the actin filament. The filaments slide past one another, thus shortening the sarcomeres, thus shortening the myofibrils, thus shortening the muscle fiber.  

Then the head of the myosin cross-bridge can release, straighten, combine with another binding site further down the actin filament, and pull again, thus shortening the sarcomere, (myofibril and muscle fiber) more.  

The actions of the myosin molecules are not synchronized - at any given moment, some myosins are attaching to the actin filament, others are creating force (pulling) and others are releasing the actin filament).  This process can be repeated for as long as the muscle fiber is stimulated, or until the point of maximal shortening of the sarcomere.

 When the muscle fiber is no longer stimulated, the cross-bridges break down, and the muscle fiber relaxes.

Blood vessels and axons of nerve cells lie within those connective tissues. A skeletal muscle fiber is a single, thin, long cell that may extend the full length of the muscle.  Just beneath its cell membrane (sarcolemma), the cytoplasm (sarcoplasm) of the fiber contains many threadlike myofibrils that lie parallel to one another.  

Each myofibril consists of repeating units called sarcomeres.  The characteristic dark and light striations of a sarcomere are due to the arrangement of two kinds of protein filaments: thick filaments composed of the protein myosin and thin ones mainly composed of the protein actin.  

•The contraction of a muscle does not necessarily mean that the muscle shortens; it only means that tension has been generated.  When muscles do cause a limb to move through the joint's range of motion, they usually act in the following cooperating groups: Agonists cause the movement to occur.  They create the normal range of movement in a joint by contracting.  

•Agonists are also referred to as prime movers since they are the muscles that are primarily responsible for generating the movement.•Antagonists act in opposition to the movement generated by the agonists and are responsible for returning a limb to its initial position.

•Synergists assist the agonist and make its action more effective by helping to hold the joint steady and keeping the two bones around the joint aligned.  Synergists are also sometimes called stabilizers.

Primary opposing muscle groups: 1. calves/tibialis anterior, 2. quadriceps/hamstrings,  3. hip flexors/gluteals, 4. erector spinae/abdominals,  5. pectorals/upper back,  6. latissimus dorsi/deltoids,  7. biceps/triceps.

A skeletal muscle fiber is a single, thin, long cell that may extend the full length of the muscle.  Just beneath its cell membrane (sarcolemma), the cytoplasm (sarcoplasm) of the fiber contains many threadlike myofibrils that lie parallel to one another.  Each myofibril consists of repeating units called sarcomeres.  

The characteristic dark and light striations of a sarcomere are due to the arrangement of two kinds of protein filaments: thick filaments composed of the protein myosin and thin ones mainly composed of the protein actin.  A muscle fiber contraction is a complex interaction of molecules, resulting in a movement within the myofibrils in which the myosin and actin filaments slide past one another.

As the intensity of stimulation increases, recruitment of motor units continues until, finally, all possible motor units in that muscle are activated and the muscle contracts with maximal tension.

A single stimulus of threshold strength activates some of a muscle’s motor units, which makes the muscle contract and then relax.  This action lasts only a fraction of a second and is called a twitch.

A whole muscle is composed of many motor units controlled by different motor neurons, which respond to different thresholds  of stimulation.  If only the motor neurons with low thresholds are stimulated, few motor units contract, and the muscle contracts with minimal tension.  

 At higher intensities of stimulation, additional motor neurons respond, and more motor units are activated, which produces a stronger muscle contraction.  Such an increase in the number of motor units being activated is called recruitment.  

When the muscle is stretched, so is the muscle spindle, which records the change in length (and how fast) and sends signals to the spine which convey this information.

This triggers the stretch reflex which attempts to resist the change in muscle length by causing the stretched muscle to contract.  The more sudden the change in muscle length, the stronger the muscle contractions will be (plyometric, or "jump", training is based on this fact).  

This basic function of the muscle spindle helps to maintain muscle tone and to protect the body from injury.  However, ballistic stretching may cause a muscle contraction so strong it tears the muscle fibers or tendons, causing injury.  

 One of the reasons for holding a stretch for a prolonged period of time (static stretching) is that as the muscle is held in a stretched position, the muscle spindle becomes accustomed to the new length and reduces its signaling.  Gradually, you can train your stretch receptors to allow greater lengthening of the muscles.

A muscle fiber contracts only when stimulated by its nerve, the motor neuron.  A nerve impulse from the motor neuron translates into a muscle impulse that affects the whole muscle fiber at once, for as long as the stimulation continues.  A stimulated skeletal muscle fiber responds to its fullest extend, i.e., it has an all-or-none response.

Physiology of Skeletal Muscle

 While each muscle fiber is connected to only one axon of a motor neuron, a motor neuron may have many densely branched axons, connecting to many muscle fibers, constituting a motor unit.

When muscles contract (possibly due to the stretch reflex), they produce tension at the point where the muscle is connected to the tendon, where the golgi tendon organ is located.  The Golgi tendon organ records the change in tension, and the rate of change of the tension, and sends signals to the spine to convey this information.  

When this tension exceeds a certain threshold, it triggers the lengthening reaction which inhibits the muscles from contracting and causes them to relax.  

Another reason for holding a stretch for a prolonged period of time is to allow this lengthening reaction to occur, thus helping the stretched muscles to relax.  It is easier and more beneficial to stretch, or lengthen, a muscle when it is not trying to contract.

Skeletal Muscle Action

This basic function of the golgi tendon organ helps to protect the muscles, tendons, and ligaments from injury.  The lengthening reaction is possible only because the signaling of golgi tendon organ to the spinal cord is powerful enough to overcome the signaling of the muscle spindles telling the muscle to contract.  

The response time betweenstimulation and muscle reaction determines the classification into fast twitch or slow twitch fibers.  Fast-twitch fibers are capable of developing greater forces, contracting faster to produce bursts of power and have greater anaerobic capacity.

In contrast, slow-twitch fibers develop force slowly, can maintain contractions longer, have greater endurance and higher aerobic capacity.  

The skeletal muscles of an average person contain about half fast twitch and half slow twitch muscle fibers.  Certain athletic activities promote increased percentage of fast twitch muscle fibers (Olympic sprinter), or slow twitch muscle fibers (Olympic marathoner).

A muscle fiber exposed to a series of stimuli of increasing frequency reaches a point when it is unable to completely relax before the next stimulus in the series arrives.  When this happens, the force of individual twitches combines, a process called summation.  

 When the resulting forceful, sustained contraction lacks even partial relaxation, it is called a tetanic contraction (tetanus).  

 As we have no control over the smooth muscle tissue of the stomach, we cannot consciously contract it, or “exercise” it.  Thus, there are no “exercises to strengthen the stomach” or “using the stomach to move the spine”.  The term "stomach" therefore does not belong into Pilates class.

A muscle fiber contraction is a complex interaction of molecules, resulting in a movement within the myofibrils in which the myosin and actin filaments slide past one another (sliding filament theory).

Along side (in parallel) with the regular muscle fibers are muscle spindles or stretch receptors, the primary proprioceptors  in the muscle.  

They undergo the same length changes as the rest of the muscle and thus measure the change in muscle length and the rate of change in muscle length.  In the tendon of the muscle is located the Golgi tendon organ.  It is sensitive to the change in tension and the rate of change of the tension, i.e., force the muscle exerts.

Summation and recruitment together can produce a sustained contraction of increasing strength.  Although twitches may occasionally occur in skeletal muscles (e.g., eyelid twitch), such contractions are of limited use.  More commonly muscular contractions are sustained.  

Even when a muscle appears to be at rest, a certain amount of sustained contraction is occurring in a small fraction of the total number of its fibers.  This muscle tone is important particularly in maintaining posture, and also enables the muscle to resist passive elongation or stretch.

They undergo the same length changes as the rest of the muscle and thus measure the change in muscle length and the rate of change in muscle length.  In the tendon of the muscle is located the Golgi tendon organ.  It is sensitive to the change in tension and the rate of change of the tension, i.e., force the muscle exerts.

When the actin and myosin contract in the muscles, the muscle shortens and the bones are pulled closer together.

Muscles called flexors force your joints to bend.

Muscles called extensors cause your limbs to straighten. A bicep is a flexor and the triceps are extensors. You may have also heard of ligaments. They are batches of connective tissue that bind bones to each other. Muscles, tendons, and ligaments can been found working together in almost all of your joints.

• Masseter• Temporalis• Lateral Pterygoid• Medial Pterygoid

Muscles for Mastication:

• Frontalis• Orbicularis oculi (planned)• Nasalis (planned)• Orbicularis oris (planned)• Levator labii superioris (planned)• Levator anguli oris (planned)• Zygomaticus major (planned)• Zygomaticus minor (planned)• Risorius (planned)• Depressor anguli oris (planned)• Depressor labii inferioris (planned)• Mentalis (planned)

Muscles for Facial Expression:

• Splenius capiitis• Splenius cervicis• Semispinalis capiitis• Semispinalis cervicis• Semispinalis thoracis• Trapezius• Suboccipital muscles

Posterior Neck Muscles :

•Sternocleidomastoid• Scalenes

Anterior Neck Muscles :

• Iliocostalis Thoracis• Iliocostalis Lumborum• Longissimus Capitis• Longissimus Cervicis• Longissimus Thoracis• Spinalis Cervicis• Spinalis Thoracis

Erector Spinal Muscles :

• Multifidus• Rotators (planned)

Transversospinal Muscles:

• Deltoid (anterior & middle)• Pectoralis major• Biceps brachii• Coracobrachialis• Subscapularis• Teres major (from the back)• Latissimus dorsai (from the back)

Muscles That Act On Anterior Arm:

• Deltoid (posterior and middle)• Supraspinatus• Infraspinatus• Teres minor• Triceps brachii: long head

http://www.getbodysmart.com/ap/muscularsystem/armmuscles/menu/menu.html

Muscles That Act On Posterior Arm:

• Serratus Anterior• Pectoralis Minor

Muscles That Act On Anterior Shoulder:

• Levator Scapulae• Trapezius• Rhomboid Major• Rhomboid Minor

Muscle That Act On Posterior Shoulder:

• Biceps Brachii• Brachialis• Brachioradialis• Pronator teres

Muscles That Act On Anterior Forearm:

• External oblique• Internal oblique• Transversus abdominus• Rectus abdominusk

Muscles of the Abdomen:

• Triceps brachii: long head• Triceps brachii: medial head• Triceps brachii: lateral head• Anconeus

Muscle That Act On Posterior Forearm:

• Flexor carpi radialis• Palmaris longus• Flexor carpi ulnaris• Flexor digitorum superficialis

Muscles That Act On Anterior Wrist/Hand:

• Extensor carpi radialis longus• Extensor carpi radialis brevis• Extensor digitorum• Extensor carpi ulnaris

Muscle That Act On Posterior Wrist/Hand:

• Iliacus• Psoas major• Tensor fasciae latae• Sartorius• Rectus femoris• Pectineus• Adductor longus• Adductor brevis• Adductor magnus• Gracilis

Muscles of the Legs (Front)

• Gluteus maximus• Gluteus medius• Gluteus minimus• Piriformis• Quadratus femoris• Biceps femoris - long head• Semimembranosus• Semitendinosus

Muscles of the Legs (Back):

 Rectus femoris• Sartorius• Gracilis• Vastus lateralis• Vastus medialis• Vastus intermedius

Muscles That Act On Anterior Leg:

• Semimembranosus• Semitendinosus• Biceps femoris - long head• Biceps femoris - short head• Gastrocnemius• Plantaris• Popliteus

Muscle That Act On Posterior Leg:

• Tibialis anterior• Extensor digitorum longus• Extensor hallucis longus• Fibularis (peroneus) tertius longus

Anterior Leg Compartment Muscles:

• Gastrocneumius• Soleus• Plantaris• Flexor hallucis longus• Flexor digitorum longus• Tibialis anterior

Posterior Leg Compartment Muscles:

• Fibularis (peroneus) longus• Fibularis (peroneus) brevis

Lateral Leg Compartment Muscles:

Several Conditions are referred to as repetitive strain injury. These are conditions caused by the constant repetition of a particular movement. Irritation of the flexor and extensor tendons in the wrist and hand is a common injury that often affects keyboard operators causing pain when the fingers are moved.

Repetitive Strain Injury

It is also a condition suffered by body builders and weight trainers who constantly put strain on the same muscles.

The symptoms of RSI include pain, aching and tingling. Sometimes restricted movement or weakness.RSI can also lead to another disorder called carpal tunnel syndrome.

This is due to pressure on the median nerve as it passes through a gap under a ligament at the front of the wrist. This disorder is characterized by numbness and pain in the thumb and middle fingers. The condition is caused by pressure on the median nerve. 

Activity

Prepare a dance demo for each group with the dance routine and music of your choice.

This dance demo will be presented inside the classroom on December 5, 2012.

I would like to thank the following:

http://www.human-body-facts.com/muscular-system.html

http://www.biology4kids.com/files/systems_muscular.html

Prepared by: Arlene G. Salustiano