The muscular system is the anatomical system of a species that allows it to move. The muscular system in vertebrates is controlled through the nervous system, although some muscles (such as the cardiac muscle) can be completely autonomous.There are three distinct types of muscles: skeletal muscles, cardiac or heart muscles, and smooth muscles.Muscles provide strength, posture balance, movement and muscles provide heat for the body to keep warm.
[edit] Skeletal muscle
Main article: Skeletal muscle
Skeletal muscle fibers 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 tendons. The fiber is one long continuous string-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 each 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 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.
[edit] Anatomy
Main article: Table of muscles of the human body
There are approximately 639 skeletal muscles in the human body.
The following are some major muscles[1] and their basic features:
Muscle
Origin
Insertion
Artery
Nerve
Action
Antagonist
gastrocnemius
femur
calcaneus
sural arteries
tibial nerve
plantarflexion, flexion of knee (minor)key
Tibialis anterior muscle
tibialis posterior
tibia, fibula
Foot
posterior tibial artery
tibial nerve
inversion of the foot, plantar flexion of the foot at the ankle
Tibialis anterior muscle
soleus
fibula, medial border of tibia
calcaneus
sural arteries
tibial nerve
plantarflexion
Tibialis anterior muscle
tibialis anterior
tibia
foot
anterior tibial artery
Fibular nerve
dorsiflex and invert the foot
Fibularis longus, Gastrocnemius, Soleus, Plantaris, Tibialis posterior
longus
fibula
Foot
fibular artery
Superficial fibular nerve
plantarflexion, eversion
Tibialis anterior muscle
brevis
fibula
Foot, eversion
peroneal artery
superficial peroneal nerve
gluteus maximus muscle
ilium, sacrum, sacrotuberous ligament
Gluteal tuberosity of the femur
gluteal arteries
inferior gluteal nerve
external rotation and extension of the hip joint
Iliacus, Psoas major, Psoas minor
biceps femoris
ischium, femur
fibula
inferior gluteal artery, popliteal artery
tibial nerve, common peroneal nerve
flexes and laterally rotates knee joint, extends hip joint
Quadriceps muscle
semitendinosus
ischium
tibia
inferior gluteal artery
sciatic
flex knee, extend hip joint
Quadriceps muscle
semimembranosus
ischium
tibia
profunda femoris, gluteal artery
sciatic nerve
Hip extension, Knee flexion
Quadriceps muscle
Iliopsoas
ilium
femur
medial femoral circumflex artery, iliolumbar artery
femoral nerve, lumbar nerves
flexion of hip
Gluteus maximus, posterior compartment of thigh
quadriceps femoriss
combined rectus femoris and vastus muscles
femoral artery
Femoral nerve
Knee extension; Hip flexion
Hamstring
adductor muscles of the hip
pubis
femur, tibia
obturator nerve
adduction of hip
levator scapulae
vertebral column
scapula
dorsal scapular artery
cervical nerve, dorsal scapular nerve
Elevates scapula, tilts its glenoid cavity inferiorly
trapezius
the rear of the skull, vertebral column
clavicle, scapula
cranial nerve XI, cervical nerves
retraction of scapula
Serratus anterior muscle
rectus abdominis
pubis
Costal cartilage of ribs 5-7, sternum
inferior epigastric artery
segmentally by thoraco-abdominal nerves
flexion of trunk/lumbar vertebrae
Erector spinae
transversus abdominis
ribs, ilium
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
clavicle, sternum, costal cartilages
humerus
thoracoacromial trunk
lateral pectoral nerve and medial pectoral nerve
Clavicular head: flexes the humerusSternocostal head: extends the humerusAs a whole, adducts and medially rotates the humerus. It also draws the scapula anteriorly and inferiorly.
biceps brachii
scapula
radius
brachial artery
Musculocutaneous nerve
flexes elbow and supinates forearm
Triceps brachii muscle
triceps brachii
scapula and humerus
ulna
deep brachial artery
radial nerve
extends forearm, caput longum adducts shoulder
Biceps brachii muscle
brachialis
humerus
ulna
radial recurrent artery
musculocutaneous nerve
flexion at elbow joint
pronator teres
humerus, ulna
radius
ulnar artery and radial artery
median nerve
pronation of forearm, flexes elbow
Supinator muscle
brachioradialis
humerus
radius
radial recurrent artery
radial nerve
Flexion of forearm
rhomboids
nuchal ligaments, spinous processes of the C7 to T5 vertebrae
scapula
dorsal scapular artery
dorsal scapular nerve
Retracts the scapula and rotates it to depress the glenoid cavity. fixes the scapula to the thoracic wall.
Serratus anterior muscle
deltoid
clavicle, acromion, scapula
deltoid tuberosity of humerus
primarily posterior circumflex humeral artery
Axillary nerve
shoulder abduction, flexion and extension
Latissimus dorsi
latissimus dorsi
vertebral column, ilium and inferior 3 or 4 ribs
humerus
subscapular artery, dorsal scapular artery
thoracodorsal nerve
pulls the forelimb dorsally and caudally
deltoid, trapezius
Rotator cuff
scapula
humerus
lateral rotation, medial rotation, abduction
[edit] Aerobic and anaerobic muscle activity
This article needs additional citations for verification. Please help improve this article by adding reliable references. Unsourced material may be challenged and removed. (July 2007)
At rest, the body produces the majority of its ATP aerobically in the mitochondria[2] without producing lactic acid or other fatiguing byproducts.[3] 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 carbohydrates and fats 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 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.[3] 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.[3] 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.[3]
[edit] Cardiac Muscle
Main article: 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 controlling themselves. Heart muscles are controlled by the sinus node influenced by the autonomic nervous system.
[edit] Smooth muscle
Main article: 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.
[edit] 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 units, each of which involves a motor neuron, attached by a series of thin finger-like structures called 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.
[edit] Skeletal muscle
Main article: Skeletal muscle
Skeletal muscle fibers 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 tendons. The fiber is one long continuous string-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 each 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 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.
[edit] Anatomy
Main article: Table of muscles of the human body
There are approximately 639 skeletal muscles in the human body.
The following are some major muscles[1] and their basic features:
Muscle
Origin
Insertion
Artery
Nerve
Action
Antagonist
gastrocnemius
femur
calcaneus
sural arteries
tibial nerve
plantarflexion, flexion of knee (minor)key
Tibialis anterior muscle
tibialis posterior
tibia, fibula
Foot
posterior tibial artery
tibial nerve
inversion of the foot, plantar flexion of the foot at the ankle
Tibialis anterior muscle
soleus
fibula, medial border of tibia
calcaneus
sural arteries
tibial nerve
plantarflexion
Tibialis anterior muscle
tibialis anterior
tibia
foot
anterior tibial artery
Fibular nerve
dorsiflex and invert the foot
Fibularis longus, Gastrocnemius, Soleus, Plantaris, Tibialis posterior
longus
fibula
Foot
fibular artery
Superficial fibular nerve
plantarflexion, eversion
Tibialis anterior muscle
brevis
fibula
Foot, eversion
peroneal artery
superficial peroneal nerve
gluteus maximus muscle
ilium, sacrum, sacrotuberous ligament
Gluteal tuberosity of the femur
gluteal arteries
inferior gluteal nerve
external rotation and extension of the hip joint
Iliacus, Psoas major, Psoas minor
biceps femoris
ischium, femur
fibula
inferior gluteal artery, popliteal artery
tibial nerve, common peroneal nerve
flexes and laterally rotates knee joint, extends hip joint
Quadriceps muscle
semitendinosus
ischium
tibia
inferior gluteal artery
sciatic
flex knee, extend hip joint
Quadriceps muscle
semimembranosus
ischium
tibia
profunda femoris, gluteal artery
sciatic nerve
Hip extension, Knee flexion
Quadriceps muscle
Iliopsoas
ilium
femur
medial femoral circumflex artery, iliolumbar artery
femoral nerve, lumbar nerves
flexion of hip
Gluteus maximus, posterior compartment of thigh
quadriceps femoriss
combined rectus femoris and vastus muscles
femoral artery
Femoral nerve
Knee extension; Hip flexion
Hamstring
adductor muscles of the hip
pubis
femur, tibia
obturator nerve
adduction of hip
levator scapulae
vertebral column
scapula
dorsal scapular artery
cervical nerve, dorsal scapular nerve
Elevates scapula, tilts its glenoid cavity inferiorly
trapezius
the rear of the skull, vertebral column
clavicle, scapula
cranial nerve XI, cervical nerves
retraction of scapula
Serratus anterior muscle
rectus abdominis
pubis
Costal cartilage of ribs 5-7, sternum
inferior epigastric artery
segmentally by thoraco-abdominal nerves
flexion of trunk/lumbar vertebrae
Erector spinae
transversus abdominis
ribs, ilium
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
clavicle, sternum, costal cartilages
humerus
thoracoacromial trunk
lateral pectoral nerve and medial pectoral nerve
Clavicular head: flexes the humerusSternocostal head: extends the humerusAs a whole, adducts and medially rotates the humerus. It also draws the scapula anteriorly and inferiorly.
biceps brachii
scapula
radius
brachial artery
Musculocutaneous nerve
flexes elbow and supinates forearm
Triceps brachii muscle
triceps brachii
scapula and humerus
ulna
deep brachial artery
radial nerve
extends forearm, caput longum adducts shoulder
Biceps brachii muscle
brachialis
humerus
ulna
radial recurrent artery
musculocutaneous nerve
flexion at elbow joint
pronator teres
humerus, ulna
radius
ulnar artery and radial artery
median nerve
pronation of forearm, flexes elbow
Supinator muscle
brachioradialis
humerus
radius
radial recurrent artery
radial nerve
Flexion of forearm
rhomboids
nuchal ligaments, spinous processes of the C7 to T5 vertebrae
scapula
dorsal scapular artery
dorsal scapular nerve
Retracts the scapula and rotates it to depress the glenoid cavity. fixes the scapula to the thoracic wall.
Serratus anterior muscle
deltoid
clavicle, acromion, scapula
deltoid tuberosity of humerus
primarily posterior circumflex humeral artery
Axillary nerve
shoulder abduction, flexion and extension
Latissimus dorsi
latissimus dorsi
vertebral column, ilium and inferior 3 or 4 ribs
humerus
subscapular artery, dorsal scapular artery
thoracodorsal nerve
pulls the forelimb dorsally and caudally
deltoid, trapezius
Rotator cuff
scapula
humerus
lateral rotation, medial rotation, abduction
[edit] Aerobic and anaerobic muscle activity
This article needs additional citations for verification. Please help improve this article by adding reliable references. Unsourced material may be challenged and removed. (July 2007)
At rest, the body produces the majority of its ATP aerobically in the mitochondria[2] without producing lactic acid or other fatiguing byproducts.[3] 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 carbohydrates and fats 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 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.[3] 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.[3] 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.[3]
[edit] Cardiac Muscle
Main article: 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 controlling themselves. Heart muscles are controlled by the sinus node influenced by the autonomic nervous system.
[edit] Smooth muscle
Main article: 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.
[edit] 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 units, each of which involves a motor neuron, attached by a series of thin finger-like structures called 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.
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