Muscular

• MUSCULAR SYSTEM

  The body’s muscular system is responsible for the body’s movement, making muscle

  contractions; this movement includes heartbeat, running, talking, and swallowing foods into the intestines.

  The hierarchy of organization of the skeletal muscle illustrates the anatomical components that form the

  whole muscle in the body, starting from the tendon to the muscle to the fascicles up to the fibrils and

  sarcolemma of the muscle fibers.
• Skeletal Muscle

  The skeletal muscle is a voluntary muscle comprising up to 40% of the body’s weight, usually

  attached to the bones, and responsible for major body movements such as doing physical activities like

  running and jogging and keeping posture, which keeps us sitting or standing erect. Skeletal muscles are

  also involved in all aspects of communication, including speaking, writing, typing, gesturing, smiling, and

  frowning
• Smooth Muscle

  The smooth muscle is an involuntary muscle and the most widely distributed type of muscle in the

  body, usually found in the walls of hollow organs, blood vessels, eyes, and glands. The contraction of

  smooth muscle within the walls of internal organs and vessels causes these structures to constrict—they

  help the body organs to regulate properly.
• Cardiac Muscle

  The cardiac muscle is an involuntary muscle found in the heart responsible for the blood-pumping

  function. The construction of cardiac muscle causes the heart to beat, propelling blood to all parts of the

  body.
• Contractility - refers to the ability of the muscle to shorten forcefully or contract. For example,

  lifting a barbell in a gym requires your muscles to contract.
• Excitability - refers to the capacity of the muscle to respond to an electrical stimulus. Normally,

  the stimulus is from the nerves that we consciously control. For instance, taking a camera out for

  a picture will instantly allow your muscle to make a post for the photo; this decision of your body

  is sent via nerves.
• Extensibility - refers to a muscle that can be stretched beyond its normal resting length and still

  be able to contract. The lack of extensibility is known as spasticity. For example, reaching to get a

  book placed on a higher shelf allows your arm to stretch, making your muscles longer than they

  are normally, but you can still retrieve the book
• Elasticity - refers to the ability of the muscle to spring back to its original resting length after it

  has been stretched. For example, taking a deep breath demonstrates elasticity as exhalation

  allows the respiratory muscle to return to its resting position.
• NECK MUSCLES

  The muscles that move the head and neck are primarily responsible for lateral head

  movement, with most flexors located deep within the neck along the vertebrae. Neck extension is

  achieved by posterior muscles attached to the occipital bone and mastoid process. The lateral muscles

  of the neck primarily contribute to lateral flexion, or side-to-side movement of the head and neck.
• Trapezius - Originates from the occipital protuberance, nuchal

  ligament, and the spinous processes of C7–T12 vertebrae. It

  inserts into the clavicle, acromion process, and scapular spine
• Longissimus Capitis - Originates from the upper thoracic and

  lower cervical vertebrae and inserts into the mastoid process of

  the temporal bone. It is innervated by the dorsal rami of the

  cervical nerves. This muscle extends, rotates, and laterally flexes

  the neck.
• Oblique Capitis Superior - Originates from the atlas (C1) and

  inserts into the occipital bone (inferior nuchal line). It is innervated

  by the dorsal ramus of the C1 nerve. The oblique capitis superior

  extends and laterally flexes the neck and assists in turning the

  head.
• Rectus Capitis Posterior - Has two parts: the rectus capitis posterior major, originating from the

  axis (C2), and the rectus capitis posterior minor, originating from the atlas (C1). Both insert into

  the occipital bone. They are innervated by the dorsal ramus of the C1 nerve. These muscles

  extend and rotate the neck, as well as help turn the head.
• Semispinalis Capitis - Originates from the transverse processes of

  C4–T6 vertebrae and inserts into the occipital bone. It is innervated

  by the dorsal rami of the cervical nerves. The semispinalis capitis

  extends and rotates the neck.
• Splenius Capitis - Originates from the spinous processes of C4–T6

  vertebrae and inserts into the superior nuchal line and mastoid

  process. It is innervated by the dorsal rami of the cervical nerves.

  This muscle extends, rotates, and laterally flexes the neck.
• Sternocleidomastoid - Originates from the manubrium and medial

  clavicle and inserts into the mastoid process and superior nuchal

  line. It is innervated by the accessory nerve (cranial nerve XI). When

  one side contracts, it laterally flexes the head and neck to the same

  side and rotates the head to the opposite side. When both sides

  contract together, it flexes the neck.
• Scalene Muscles - (anterior, middle, and posterior) originate from the transverse processes of

  the cervical vertebrae (C2–C6) and insert into the first and second ribs. They are innervated by

  the cervical and brachial plexuses. These muscles flex the neck, laterally flex the neck, and assist

  in rotating the neck.