Mayur Deshpande
  Personal trainer in Mumbai
Learn Human Body Human Muscular System

Learn Human Body

Human Muscular System


The anatomical system most directly affected by exercise is the muscular system.Human muscular system includes skeletal,cardiac and smooth muscle.Muscles are connective tissue. There are more than 600 muscles in human body in different shapes and sizes. There are three types of muscle tissues ;skeletal,cardiac(heart) and visceral.Out of which,the skeletal muscular system is controlled through the nervous system, contraction of other two muscles (viscrea & cardiac muscle) is completely autonomous.
The skeletal muscular system is capable of contracting longitudinally in response to nervous stimulation. The muscle cells contain small contractile strands of protein (so-called myofibrils). They contract when stimulated, returning to their original state as soon as nervous stimulation ceases. Fro a functional prospective ,it is important to understand that most muscles of the trunk & extremities are arranged in opposing muscles.That is ,when one muscle(prime mover/agonist) is contracting to achieve a desired movement,its opposite muscle(the antagonist) is being stretched,during this process synergist(assisting) muscles assists the prime movers to achieve a desired movement.


Types of muscle tissue.

Types of muscle contraction.

Classification of muscle fibers


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Types of muscle tissue.

Smooth/Visceral muscles- The smooth muscle is found in the walls of inetrnal organs such as the stomach,reproductive organs,respiratory tract, intestines and in the blood vessels.The smooth muscles consist of smooth muscle fibers. The smooth muscles carry out the involuntary movements of the inner organs, e.g. the (peristaltic) bowel movement. The cells that compose smooth muscle generally have single nuclei. The nerves are supplied exclusively by the vegetative (autonomous) nervous system.
Cardiac muscle- cardiac muscle tissue forms the wall of the heart and it is involuntary by nature. Cardiac muscle is adapted to be highly resistant to fatigue: it has a large number of mitochondria enabling continuous aerobic respiration; numerous myoglobins (oxygen storing pigment); and a good blood supply, which provides metabolic substrate and oxygen. In contrast to skeletal muscle, cardiac muscle cannot contract in the absence of extracellular calcium ions as well as extracellular potassium ions.
Skeletal muscle- Skeletal muscle is a type of striated muscle, attached to the skeleton. Skeletal muscles are used to facilitate movement, by applying force to bones and joints; via contraction. They generally contract voluntarily (via nerve stimulation), although they can contract involuntarily.


Types of muscle contraction.

A muscle contraction (also known as a muscle twitch or simply twitch) occurs when a muscle cell (called a muscle fiber) lengthens or shortens. Locomotion in most higher animals is possible only through the repeated contraction of many muscles at the correct times. Contraction is controlled by the central nervous system comprised of brain and spinal cord. The brain controls voluntary muscle contractions, while the spine controls involuntary reflexes.Following are the types of exercised related muscle contraction.

Concentric contraction- A concentric contraction is a type of muscle contraction in which the muscles generates enough force to overcome the resistance to joint movement so it shortens (decrease the angle at joint) as it contracts. During a concentric contraction, a muscle is stimulated to contract according to the sliding filament mechanism. This occurs throughout the length of the muscle, generating force at the musculo-tendinous junction, causing the muscle to shorten and changing the angle of the joint. In relation to the elbow and bicep, the contraction of the bicep would cause the hand to move from the leg and close to the shoulder.

Eccentric contraction- An eccentric contraction is a type of muscle contraction in which the resistance (such as a weight carried in the hand) is greater than the force applied by the muscle so that the muscle lengthens as it contracts. Eccentric contractions also occur when the muscular force is used to brake or slow the opening of a joint. In terms of a bicep curl, during a complete concentric contraction the biceps shorten and elbow goes from fully straight (hand at mid-thigh) to completely bent (hand at the shoulder). In contrast, during an eccentric contraction the muscle lengthens, the hand moving from shoulder to thigh and the elbow straightening. Because the contraction works in the opposite direction the muscles are generally supposed to move (i.e. muscles can only shorten, never lengthen), muscles undergoing heavy eccentric loading suffer greater damage when overloaded (such as during muscle building or strength training exercise) as compared to concentric loading. Exercise that incorporates both eccentric and concentric muscular contractions can produce greater gains in strength and toughness than concentric contractions alone.

Isometric contraction- Isometric exercise or 'isometrics' are a type of strength training in which the joint angle and muscle length do not change during contraction (compared to concentric or eccentric contractions, called isotonic movements). Isometrics are done in static positions, rather than being dynamic through a range of motion. The joint and muscle are either worked against an immovable force or are held in a static position while opposed by resistance.


Classification of muscle fibers

Muscle fibers can be classified broadly as 1) Fast-twitch 2) Slow twitch with differing functional and metabolic characteristic. The type of muscle fiber recruited to perform a specific activity depends on intensity and duration of exercise. Most muscle contains contain both fast-twitch and slow twitch muscle fiber, However the ratio of fast-twitch to slow twitch muscle fiber varies in an individual. The ratio also differs within the same muscle from one individual to another.
Fast twitch (type-2)fibers-
Fast twitch muscle fibers are recruited when a person is performing high intencsity activities.These fibers can contract faster than slow twitch muscle fibers,but the accumulation of lactic acid & hydrogen ion concentration from anaerobic glycolysis causes them to fatigue quickly.Fast twitch muscle fibers are subdivided into fast-twitch oxidative type-2a and fast twitch glycolytic type-2b.
Slow twitch(type-1) fibers
Slow twitch muscle fibers are recruited when a person is performing low intencsity activities.aerobic capacity of slow twitch muscle fibers is better than fast twitch fibers.

Metabolic characteristics of both,fast twitch and slow twicth muscle fibers //