Muscular System
The muscular system is an organ system that is controlled through the nervous system. There are muscles which are made up of three different muscle fibers, skeletal, cardiac, and smooth muscles. The function of the muscular system is to permit
movement of the body, maintain the posture of the body, and to circulate blood throughout the body. When combined with
the skeletal system it becomes the musculoskeletal system, which is the system used to allow movement of the body. Smooth muscle is not striated, skeletal muscles often attach to bone with tendons, the cardiac muscle is often autonomous and does not rely on the nervous system to function.
Pectoralis Major Muscle Deltoid Muscle Gastrocnemius MuscleSerratus Anterior Muscles External Oblique Muscle Rectus Abdominis Frontalis Muscle Laterally Temporal Muscle Laterally Occipitalis Muscle Laterally Splenius Capitis Muscle LaterallyLevator Scapulae Muscle LaterallyTrapezius Muscle Laterally Sternomastoid Muscle Laterally Masseter Muscle Laterally Buccinator Muscle Laterally Orbicularis Oris LaterallyVastus Medialis Muscle Extensor Carpi Radialis Longus Muscle Biceps Brachii Muscle Brachialis MuscleDorsal Interossei Muscle Extensor Digitorum Communis Muscle Pectineus Muscle Triceps Brachii MusclesTensor Fasciae Latae Muscle Brachioradialis MuscleDeltoid Muscle of Arm Gracilis Muscle Rectus Abdominus Extensor RetinaculumBrachioradialis Muscle Posterior Palmaris Longus Muscle Adductor Longus Muscle Orbicularis Oculi Muscle Laterally Vastus Lateralis Muscle Tibialis Anterior Muscle Sartorius Muscle
Muscular System
Types of Muscle:
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Skeletal
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Smooth
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Cardiac
There are about 639 skeletal muscles in the human body. Skeletal muscles are combined into hundreds of motor units. All these are attached to a motor nerve which acts to stimulate the movement of the muscle from a series of axon terminals. These axon terminals are finger-like structures which attach to and control the bundles of muscle fibers. A response to a certain circumstance sends into action the precise number of motor units used to allow the muscle to contract as a unit.
The entire muscle can contract on a pre-determined basis based on the structure of the motor unit. Motor unit coordination, balance and control frequency come under the direction of the cerebellum of the brain. This allows for complex muscular coordination without much conscious effort such as when riding a bicycle or driving a car without thinking about the process.
Smooth muscles are controlled by the autonomic nervous system and are involuntary and do not rely on conscious thought to be carried out. These include functions such as the heartbeat and breathing through the lungs but are not made of smooth muscles.
The heart muscles are distinctly different from skeletal muscles because the muscle fibers are laterally connected to each other. Just as with smooth muscles they are not controlled by themselves. Heart muscles are controlled by the sinus node influenced by the autonomic nervous system. There are many elements that go into the control of a muscle contraction which is what releases the energy to the muscle to perform before relaxing. Neuromuscular junctions are the focal point where a motor neuron attaches to a muscle. A loss of function at the junction can result in paralysis.
A few of the major muscles, their insertion, and attachments with their function follows.
Major Muscles and Basic Function:
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Gastrocnemius; origin femur, insertion calcaneus. Function: (plantar flexion, flexion of the knee (minor) key.
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Tibialis Posterior; origin tibia, fibula, insertion foot. Function: (inversion of the foot, plantar flexion of foot and ankle).
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Gluteus Maximus; origin ilium, sacrum, sacrotuberous ligament, insertion Gluteal tuberosity of the femur. Function: (external rotation and extension of the hip joint).
- Pectoralis Major; origin clavicle, sternum, costal cartilage. Function: (Clavicular head: flexes the humerus. Sternocostal head:extends the humerus. As it also adducts and medially rotates the humerus. It also draws the scapula anteriorly and inferiorly).
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