Muscles

There are 3 major muscle types in human body:

1. Skeletal (Voluntary)- controls movement and posture.
2. Cardiac Muscle(Involuntary)- encompasses the heart.
3. Smooth Muscle(Involuntary)-located throughout the Gastrointestinal, Reproductive, Urinary, Vascular and Respiratory System.

Functions:

• A muscle in the human body, whether it is skeletal, cardiac, or smooth, functions to create force and movement.
• Muscles of the skeleton (Skeletal muscle) support the bones to maintain posture as well as control voluntary movement. Skeletal muscle also contributes to energy metabolism and storage.
• Cardiac muscle propels blood and leads to proper oxygenation and maintenance of each cell that comprises the human body.
• Smooth muscle is located throughout the body and uses contractile force to shorten and propel various contents across the lumen of the multiple organ systems in which it is involved.

We will see only Skeletal muscles in detail.

Skeletal Muscles:

• Approximately 40% of the total human body weight is of skeletal muscles.
• Skeletal muscle is group of many individual muscle fibers that are bundled together to form a muscle spindle and this is what it gives striated structure.
• Each muscle fiber has contractible filament which composed mostly by Actin and Myosin fiber and covered by cell membrane. This fiber is responsible for contraction and relaxation of Muscle. During contraction muscle fibers come to each other and overlap and during relaxation go away from each other.
• The energy required in muscle contraction is stored in muscle in very short amount.
• Muscles use Fatty acids for their energy during rest and use glucose after eating food and during exercise. When muscle contracts fast, Glucose is used without Oxygen
• Two major classifications of Skeletal Muscle:
• Type I (Slow Oxidative or Slow twitch fibers) - used during slow and sustained actions e.g. postural muscles which our body against the gravity.
• Type II (Fast twitch fibers) - used during fast and short actions e.g. 100 m running, Shot-put through.
• If we use muscle repeatedly, its strength increase and if we do not use our any particular muscle, its strength rapidly decreases or if skeletal remains in only 1 position, the concerned muscles will become short in length.
• And if we use muscle for a long time, its endurance or ability to work for long time will increases.
• There are 2 groups of muscles works together for action, 1 group is often stronger than other.
• The ideal exercise will be one which involves big muscles to maintain their strength, endurance and also maintain range of movement of most of the body joints. And takes care of cardio-pulmonary reserve.
• When Muscles are used during exercise following happens:
• Muscles need more blood(Glucose+O2) hence heart and lungs have to work more.
• The blood vessels in Muscles dilate I.e. increases its lumen size.
• The closed capillaries(extra dormant) opens.
• Blood glucose is utilized.
• HDL(good cholesterol) increases.