Human Body System project

Muscular System Created By: Michael Marbry

Function of the Muscular System

The 650 muscles in the body not only support movement controlling walking, talking, sitting, standing, eating and other daily functions that people consciously perform but also help to maintain posture and circulate blood and other substances throughout the body, among other functions.

Types of muscle tissue

Skeletal muscles are the only voluntary muscle tissue in the human body and control every action that a person consciously performs. Most skeletal muscles are attached to two bones across a joint, so the muscle serves to move parts of those bones closer to each other, according to the Merck Manual.

Visceral, or smooth, muscle is found inside organs such as the stomach and intestines, as well as in blood vessels. It is called a smooth muscle because, unlike skeletal muscle, it does not have the banded appearance of skeletal or cardiac muscle. The weakest of all muscle tissues, visceral muscles contract to move substances through the organ, according to The Merck Manual. Because visceral muscle is controlled by the unconscious part of the brain, it is known as involuntary muscle, as it cannot be controlled by the conscious mind.

The cardiac muscle is an involuntary muscle responsible for pumping blood throughout the body, according to The Merck Manual. The heart's natural pacemaker is made of cardiac muscle that signals other cardiac muscles to contract. Like visceral muscles, cardiac muscle tissue is controlled involuntarily. While hormones and signals from the brain adjust the rate of contraction, cardiac muscle stimulates itself to contract.

Explain how skeletal muscle contracts, including the release of calcium ions from thesarcoplasmic reticulum, the formation of cross-bridges, the sliding of actin and myosin filaments and the use of ATP.

  1. An action potential from a motor neuron triggers the release of Ca2+ ions from the sarcoplasmic reticulum
  2. Calcium ions expose the myosin heads by binding to a blocking molecule (troponin complexed with tropomyosin) and causing it to move
  3. The myosin heads form a cross-bridge with actin binding sites
  4. ATP binds to the myosin heads and breaks the cross-bridge
  5. The hydrolysis of ATP causes the myosin heads to change shape and swivel - this moves them towards the next actin binding site
  6. The movement of the myosin heads cause the actin filaments to slide over the myosin filaments, shortening the length of the sarcomere
  7. Via the repeated hydrolysis of ATP, the skeletal muscle will contract


Muscular Dystrophy - Muscular Dystrophy is a sex-linked genetic disorder of the muscles that causes muscles to weaken slowly due to a lack of the protein dystrophin which holds the skeletal muscle cells together. When a person has this disease, their muscle tissues are replaced by fatty deposits

Symptoms - waddling when walking, difficulty climbing stairs, trouble standing up or sitting down, repeated falling, eventual loss of strength, increasing disability, possible deformity

Common - Muscular dystrophy is the most common and the most severe form of MD. It affects about 1 out of every 3,500 boys.

Treatment - Physical Therapy, Bracing, Spinal Fusion, Respiratory care

Myopathy - Myopathy is a disease that causes the skeletal or voluntary muscles to become weak or wasted. Myopathies sometimes occur as a result of drug side effects, chemical poisoning, or a chronic disorder of the immune system.

Symptoms - Aching, Cramping, Pain, Stiffness, Tenderness. Tightness

Common - This can effect anyone but the main people who get effected are children and young adults.

Treatment - Drug therapy, Physical therapy, Bracing, Surgery