Muscular system
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2008-07-15T18:51:02Z
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/* Skeletal muscle */ removed obviously untrue and obscene material
The '''muscular system''' is the anatomical system of a species that allows it to move. The muscular system in [[vertebrate]]s is controlled through the [[nervous system]], although some [[muscle]]s (such as the [[cardiac muscle]]) can be completely autonomous.
== Muscles ==
{{Main|Muscle}}
There are three distinct types of muscles: skeletal muscles, cardiac muscles, and smooth muscles.
===Skeletal muscle ===
{{Main|Skeletal muscle}}
Skeletal muscle fibres are also multinucleated, with the cell's nuclei located just beneath the plasma membrane. The cell comprises a series of striped or striated, thread-like [[myofibrils]]. Within each myofibril there are protein filaments that are anchored by dark Z lin. The fiber is one long continuous thread-like structure. The smallest cross section of skeletal muscle is called a [[sarcomere]] which is the functional unit within the cell. It extends from one Z line to the next attached Z line. The individual sarcomere has alternating thick [[myosin]] and thin [[actin]] protein filaments. Myosin forms the center or middle of eache M line. Thinner actin filaments form a zig zag pattern along the anchor points or Z line.
Upon stimulation by an [[action potential]], skeletal muscles perform a coordinated contraction by shortening each sarcomere. The best proposed model for understanding contraction is the [[sliding filament model]] of muscle contraction. Actin and myosin fibers overlap in a contractile motion towards each other. Myosin filaments have club-shaped heads that project toward the actin filaments.
Larger structures along the myosin filament called [[Myosin|myosin heads]] are used to provide attachment points on binding sites for the actin filaments. The myosin heads move in a coordinated style, they swivel toward the center of the sarcomere, detach and then reattach to the nearest active site of the actin filament. This is called a rachet type drive system. This process consumes large amounts of [[adenosine triphosphate]] (ATP).
Energy for this comes from ATP, the energy source of the cell. ATP binds to the cross bridges between myosin heads and actin filaments. The release of energy powers the swiveling of the myosin head. Muscles store little ATP and so must continuously recycle the discharged [[adenosine diphosphate]] molecule (ADP) into ATP rapidly. Muscle tissue also contains a stored supply of a fast acting recharge chemical, [[creatine phosphate]] which can assist initially producing the rapid regeneration of ADP into ATP.
[[Calcium ions]] are required for each cycle of the sarcomere. Calcium is released from the [[sarcoplasmic reticulum]] into the [[sarcomere]] when a muscle is stimulated to contract. This calcium uncovers the actin binding sites. When the muscle no longer needs to contract, the calcium ions are pumped from the sarcomere and back into storage in the [[sarcoplasmic reticulum]].
====Anatomy====
{{Main|Table of muscles of the human body}}
There are approximately 639 skeletal muscles in the human body.
The following are some major muscles<ref> [http://www.cylive.com/viewContent.do?id=192&vt=pub List of major muscles of the human body] </ref> and their basic features:
{| class="wikitable" width="100%"
| '''Muscle''' || '''Origin''' || '''Insertion''' || '''Artery''' || '''Nerve''' || '''Action''' || '''Antagonist'''
|-
| [[gastrocnemius muscle|gastrocnemius]] || [[femur]] || [[calcaneus]] || [[sural arteries]] || [[tibial nerve]]|| [[plantarflexion]], [[flexion]] of [[knee]] (minor)key || [[Tibialis anterior muscle]]
|-
| [[tibialis posterior muscle|tibialis posterior]] || [[tibia]], [[fibula]] || [[Foot]] || [[posterior tibial artery]] || [[tibial nerve]] || [[Inversion (kinesiology)|inversion of the foot]], [[plantar flexion]] of the [[foot]] at the [[ankle]] || [[Tibialis anterior muscle]]
|-
| [[soleus muscle|soleus]] || [[fibula]], medial border of [[tibia]]|| [[calcaneus]] ||[[sural arteries]] || [[tibial nerve]] || [[plantarflexion]] || [[Tibialis anterior muscle]]
|-
| [[tibialis anterior muscle|tibialis anterior]] || [[tibia]] || [[foot]] || [[anterior tibial artery]] || [[Deep fibular nerve| Fibular nerve]] || [[dorsiflexion|dorsiflex]] and [[Inversion (kinesiology)|invert]] the foot || [[Fibularis longus]], [[Gastrocnemius muscle|Gastrocnemius]], [[Soleus muscle|Soleus]], [[Plantaris muscle|Plantaris]], [[Tibialis posterior muscle|Tibialis posterior]]
|-
| [[Peroneus longus|longus]] || [[fibula]] || [[Foot]] || [[fibular artery|fibular artery]] || [[Superficial fibular nerve|Superficial fibular nerve]] || [[plantarflexion]], [[Eversion (kinesiology)|eversion]] || [[Tibialis anterior muscle]]
|-
| [[Peroneus brevis|brevis]] || [[fibula]] || [[Foot]], [[Eversion (kinesiology)|eversion]] || [[peroneal artery]] || [[superficial peroneal nerve]] ||
|-
| [[gluteus maximus muscle]] || [[ilium (bone)|ilium]], [[sacrum]], [[sacrotuberous ligament]] || [[Gluteal tuberosity]] of the [[femur]] || [[gluteal arteries]] || [[inferior gluteal nerve]] || [[external rotation]] and [[Extension (kinesiology)|extension]] of the [[hip joint]] || [[Iliacus muscle|Iliacus]], [[Psoas major muscle|Psoas major]], [[Psoas minor]]
|-
| [[biceps femoris muscle|biceps femoris]] || [[ischium]], [[femur]] || [[fibula]] || [[inferior gluteal artery]], [[popliteal artery]] || [[tibial nerve]], [[common peroneal nerve]] || [[Flexion|flexes]] and [[laterally rotates]] [[knee joint]], [[Extension (kinesiology)|extends]] [[hip joint]] || [[Quadriceps muscle]]
|-
| [[semitendinosus muscle|semitendinosus]] || [[ischium]] || [[tibia]] || [[inferior gluteal artery]] || [[sciatic nerve|sciatic]] || [[Flexion|flex]] [[knee]], [[Extension (kinesiology)|extend]] [[hip joint]] || [[Quadriceps muscle]]
|-
| [[semimembranosus muscle|semimembranosus]] || [[ischium]] || [[tibia]] || [[profunda femoris]], [[gluteal artery]] || [[sciatic nerve]] || [[Hip]] [[Extension (kinesiology)|extension]], [[Knee]] [[flexion]] || [[Quadriceps muscle]]
|-
| Iliopsoas || [[ilium (bone)|ilium]] || [[femur]] || [[medial femoral circumflex artery]], [[iliolumbar artery]] || [[femoral nerve]], [[lumbar nerves]] || [[flexion]] of [[hip]] || [[Gluteus maximus]], [[posterior compartment of thigh]]
|-
| [[quadriceps femoris muscle|quadriceps femoris]]s || combined [[rectus femoris]] and [[vastus]] muscles || ||[[femoral artery]] || [[Femoral nerve]] || [[Knee]] [[Extension (kinesiology)|extension]]; [[Hip]] [[flexion]] || [[Hamstring]]
|-
|[[adductor muscles of the hip]] || [[Pubis (bone)|pubis]] || [[femur]], [[tibia]] || || [[obturator nerve]] || [[adduction]] of [[hip]] ||
|-
| [[levator scapulae muscle|levator scapulae]] || [[vertebral column]] || [[scapula]] || [[dorsal scapular artery]] || [[cervical nerve]], [[dorsal scapular nerve]] || [[Elevation (kinesiology)|Elevates]] [[scapula]], tilts its [[glenoid cavity]] inferiorly ||
|-
| [[Trapezius muscle|trapezius]] || the rear of the skull, [[vertebral column]] || [[clavicle]], [[scapula]] || || [[Accessory nerve|cranial nerve XI]], [[cervical]] [[nerve]]s || [[Retraction (kinesiology)|retraction]] of [[scapula]] || [[Serratus anterior muscle]]
|-
| [[Rectus abdominis muscle|rectus abdominis]] || [[pubis (bone)|pubis]] || [[Costal cartilage]] of [[ribs]] 5-7, [[sternum]] || [[inferior epigastric artery]] || segmentally by [[thoraco-abdominal nerves]] || [[flexion]] of [[torso|trunk]]/[[lumbar vertebrae]] || [[Erector spinae]]
|-
| [[Transversus abdominis muscle|transversus abdominis]] || [[ribs]], [[ilium (bone)|ilium]] || [[pubis (bone)|pubic tubercle]] || || lower intercostal nerves, [[iliohypogastric nerve]] and the [[ilioinguinal nerve]] || compress the ribs and viscera, thoracic and pelvic stability ||
|-
| [[Abdominal external oblique muscle]] || Lower 8 [[costae]] || [[Crista iliaca]], [[ligamentum inguinale]] || || lower 6 [[intercostal nerve]], [[subcostal nerve]] || Rotates [[torso]] ||
|-
| [[Abdominal internal oblique muscle]] || [[Inguinal ligament]], [[Iliac crest]] and the [[Lumbodorsal fascia]] || [[Linea alba]], [[sternum]] and the inferior ribs. || || || Compresses abdomen and rotates vertebral column. ||
|-
| [[erector spinae]] || on the spines of the last four [[thoracic vertebræ]] || both the spines of the most cranial [[thoracic vertebrae]] and the [[cervical vertebrae]] || [[lateral sacral artery]] || [[posterior branch of spinal nerve]] ||extends the [[vertebral column]] || [[Rectus abdominis muscle]]
|-
| [[pectoralis major muscle|pectoralis major]] || [[clavicle]], [[sternum]], [[costal cartilages]] || [[humerus]] || [[thoracoacromial trunk]] || [[lateral pectoral nerve]] and [[medial pectoral nerve]] || '''Clavicular head''': [[flexes]] the [[humerus]]<BR>'''Sternocostal head''': [[extends]] the humerus <BR> As a whole, [[adducts]] and [[medially rotates]] the [[humerus]]. It also draws the [[scapula]] anteriorly and inferiorly. ||
|-
| [[biceps brachii muscle|biceps brachii]] || [[scapula]] || [[radius (bone)|radius]] || [[brachial artery]] || [[Musculocutaneous nerve]] || [[flexes]] [[Elbow-joint|elbow]] and [[supinates]] [[forearm]] || [[Triceps brachii muscle]]
|-
| [[triceps brachii muscle|triceps brachii]] || [[scapula]] and [[humerus]] || [[ulna]] || [[deep brachial artery]] || [[radial nerve]] || [[extends]] [[forearm]], caput longum [[adducts]] [[shoulder]] || [[Biceps brachii muscle]]
|-
| [[brachialis muscle|brachialis]] || [[humerus]] || [[ulna]] || [[radial recurrent artery]] || [[musculocutaneous nerve]] || [[flexion]] at [[elbow|elbow joint]] ||
|-
| [[pronator teres muscle|pronator teres]] || [[humerus]], [[ulna]] || [[radius (bone)|radius]] || [[ulnar artery]] and [[radial artery]] || [[median nerve]] || [[pronation]] of [[forearm]], [[flexes]] [[Elbow-joint|elbow]] || [[Supinator muscle]]
|-
| [[brachioradialis]] || [[humerus]] || [[radius (bone)|radius]] || [[radial recurrent artery]] || [[radial nerve]] || [[Flexion]] of [[forearm]] ||
|-
| [[rhomboid muscle|rhomboid]]s || [[nuchal ligaments]], [[spinous processes]] of the C7 to T5 [[vertebrae]] || [[scapula]] || [[dorsal scapular artery]] || [[dorsal scapular nerve]] || [[Retraction (kinesiology)|Retracts]] the [[scapula]] and rotates it to [[Depression (kinesiology)|depress]] the [[glenoid cavity]]. fixes the scapula to the [[thoracic wall]]. || [[Serratus anterior muscle]]
|-
| [[deltoid muscle|deltoid]] || [[clavicle]], [[acromion]], [[scapula]] || [[deltoid tuberosity]] of [[humerus]] || primarily [[posterior circumflex humeral artery]] || [[Axillary nerve]] || [[shoulder]] [[Abduction (kinesiology)|abduction]], [[flexion]] and [[Extension (kinesiology)|extension]] || [[Latissimus dorsi]]
|-
| [[Latissimus dorsi muscle|latissimus dorsi]] || [[vertebral column]], [[ilium (bone)|ilium]] and inferior 3 or 4 ribs || [[humerus]] || [[subscapular artery]], [[dorsal scapular artery]] || [[thoracodorsal nerve]] || pulls the [[forelimb]] [[dorsally]] and [[caudally]] || [[Deltoid muscle|deltoid]], [[Trapezius muscle|trapezius]]
|-
| [[Rotator cuff]] || [[scapula]] || [[humerus]] || || || lateral rotation, medial rotation, abduction ||
|- yes
|}
====Aerobic and anaerobic muscle activity====
{{Refimprove|date=July 2007}}
At rest, the body produces the majority of its [[Adenosine triphosphate|ATP]] aerobically in the [[mitochondria]]<ref>ABERCROMBIE M; HICKMAN C.J; JOHNSON M.L, 1973, A Dictionary of Biology, Page 179, Middlesex (England), Baltimore (U.S.A), Ringwood (Australia): Penguin Books</ref> without producing [[lactic acid]] or other fatiguing byproducts.<ref name = ppt>{{cite web | url = http://intranet.spc.sa.edu.au/usermedia/curr/pe/ep5.ppt | accessdate = 2007-10-16 | title = St Paul’s College Stage 2 EXERCISE PHYSIOLOGY Energy Systems Part 5 | format = ppt }}</ref> During exercise, the method of ATP production varies depending on the fitness of the individual as well as the duration, and intensity of exercise. At lower activity levels, when exercise continues for a long duration (several minutes or longer), energy is produced aerobically by combining oxygen with [[carbohydrate]]s and [[fat]]s stored in the body. Activity that is higher in intensity, with possible duration decreasing as intensity increases, ATP production can switch to anaerobic pathways, such as the use of the [[Phosphocreatine|creatine phosphate]] and the phosphagen system or anaerobic [[glycolysis]]. Aerobic ATP production is biochemically much slower and can only be used for long-duration, low intensity exercise, but produces no fatiguing waste products that can not be removed immediately from [[sarcomere]] and body and results in a much greater number of ATP molecules per fat or carbohydrate molecule. Aerobic training allows the oxygen delivery system to be more efficient, allowing aerobic metabolism to being more quickly.<ref name = ppt/> Anaerobic ATP production produces ATP much faster and allows near-maximal intensity exercise, but also produces significant amounts of [[lactic acid]] which render high intensity exercise unsustainable for greater than several minutes.<ref name = ppt/> The phosphagen system is also anaerobic, allows for the highest levels of exercise intensity, but intramuscular stores of [[phosphocreatine]] are very limited and can only provide energy for exercises lasting up to ten seconds. Recovery is very quick, with full creatine stores regenerated within five minutes.<ref name = ppt/>
===Cardiac Muscle===
{{Main|Heart muscle}}
Heart muscles are distinct from skeletal muscles because the [[muscle fibers]] are laterally connected to each other. Furthermore, just as with smooth muscles, they are not controlled by will. Heart muscles are controlled by the [[sinus node]], which, in turn, is influenced by the [[autonomic nervous system]].
===Smooth muscle===
{{Main|Smooth muscle}}
Smooth muscles are controlled directly by the [[autonomic nervous system]] and are involuntary, meaning that they are incapable of being moved by conscious thought. Functions such as heart beat and lungs (which are capable of being willingly controlled, be it to a limited extent though) are involuntary muscles but are not smooth muscles.
==Control of muscle contraction==
[[Neuromuscular junctions]] are the focal point where a [[motor neuron]] attaches to a muscle. Acetylcholine, (a [[neurotransmitter]] used in skeletal muscle contraction) is released from the axon terminal of the nerve cell when an action potential reaches the microscopic junction, called a [[synapse]]. A group of chemical messengers cross the synapse and stimulate the formation of electrical changes, which are produced in the muscle cell when the acetylcholine binds to receptors on its surface. Calcium is released from its storage area in the cell's sarcoplasmic reticulum. An impulse from a nerve cell causes calcium release and brings about a single, short [[muscle contraction]] called a [[muscle twitch]]. If there is a problem at the neuromuscular junction, a very prolonged contraction may occur, [[tetanus]]. Also, a loss of function at the junction can produce [[paralysis]].
Skeletal muscles are organized into hundreds of [[motor unit]]s, each of which involves a motor neuron, attached by a series of thin finger-like structures called [[Chemical synapse#Anatomy and physiology|axon terminals]]. These attach to and control discrete bundles of muscle fibers. A coordinated and fine tuned response to a specific circumstance will involve controlling the precise number of motor units used. While individual muscle units contract as a unit, the entire muscle can contract on a predetermined basis due to the structure of the motor unit. Motor unit coordination, balance, and control frequently come under the direction of the [[cerebellum]] of the brain. This allows for complex muscular coordination with little conscious effort, such as when one drives a car without thinking about the process.
==See also==
* [[Major systems of the human body]]
==Notes==
{{reflist}}
==References==
*[http://www.emc.maricopa.edu/faculty/farabee/BIOBK/BioBookMUSSKEL.html Online Muscle Tutorial]
==External links==
*[http://www.getbodysmart.com/ap/muscularsystem/menu/menu.html GetBody Smart] Muscle system tutorials and quizzes
*[http://www.medbio.info/Horn/Time%206/muscle_metabolism_march_2007.htm MedBio.info] Use and formation of ATP in muscle
{{muscular system}}
{{organ systems}}
[[Category:Muscular system| ]]
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[[es:Sistema muscular (anatomía humana)]]
[[fr:Système musculaire]]
[[it:Sistema muscolare]]
[[he:מערכת השרירים]]
[[pl:Układ mięśniowy]]
[[pt:Sistema muscular]]
[[ro:Sistemul muscular]]
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