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Muscular System

Types of Muscle:

  • Skeletal

  • Smooth

  • 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:

  • Gastrocnemius; origin femur, insertion calcaneus. Function: (plantar flexion, flexion of the knee (minor) key.

  • Tibialis Posterior; origin tibia, fibula, insertion foot. Function: (inversion of the foot, plantar flexion of foot and ankle).

  • 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).

Types of Muscle:

  • Skeletal

  • Smooth

  • 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:

  • Gastrocnemius; origin femur, insertion calcaneus. Function: (plantar flexion, flexion of the knee (minor) key.

  • Tibialis Posterior; origin tibia, fibula, insertion foot. Function: (inversion of the foot, plantar flexion of foot and ankle).

  • 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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