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Muscular System
Your muscular system in conjunction with the skeletal system provide a supportive framework for the body which is capable of an enormous range of motion by using muscles in coordinated teamwork.
Your muscular system also powers internal process’s such as:
- Heartbeat.
- Movement of foodstuffs through the intestines.
- Eye focusing.
- Adjustment of artery diameters.
Your muscular system and skeletal system interact with other body systems especially the nervous system without which they could not function. It is your nervous system which stimulates their activities.
Even when the body sleeps your muscular system is never still:
- Breathing continues.
- The heart beats.
- Skeletal muscles contract occasionally.
- Intestinal muscles contract.
There are three types of muscle:
Skeletal muscle (voluntary muscle) which is anchored by tendons to bone and is used to effect skeletal movement such as:
- Locomotion.
- Maintaining posture.
Though this postural control is generally maintained as a subconscious reflex muscles also react to conscious control.
Smooth muscle (involuntary muscle) is found within the walls of organs and structures such as:
- The oesophagus.
- Stomach.
- Intestines.
- Bronchi.
- Uterus.
- Urethra.
- Bladder.
- Blood vessels.
- the arrector pili in the skin (which controls erection of body hair).
Unlike skeletal muscle, smooth muscle is not under conscious control.
Cardiac muscle
- involuntary muscle -
found only in the heart.
Muscles can only contract (shorten) in other words they have the ability to pull and are unable to push. Therefore, they are arranged in pairs.
- The contracting muscle is known as the agonist.
- The opposite muscle of the pair is known as the antagonist.
When a muscle is in its relaxing mode it maintains varying degrees of tension ensuring
that any movement occurs in a controlled motion. Few movements are achieved from
a single pair of muscles, usually a team of muscles act as agonists to produce the
required degree and direction of movement while the antagonists exert a degree of
tension to prevent the movement over - extending.
- Skeletal muscle whose contraction bends a joint, decreasing the angle between components of a limb, such as bending the knee or elbow is called a flexor muscle and the action is known as flexion.
- Skeletal muscle whose contraction opens a joint, increasing the angle between components of a limb, such as straightening the knee or elbow is called an extensor muscle and the action is known as extension.
Positional Sense
Muscle contain numerous sensors known as neuromuscular spindles (modified muscle fibre ). Sensory nerve fibres wrapped around the modified muscle fibre send information to the brain about muscle length and tension as the muscle stretches. Other receptors are found in ligaments and tendons and together they create the body’s sense of of its own position and posture. This is known as proprioception.
The typical body contains 640 muscles An average adult male is made up of 42% of skeletal muscle and an average adult female is made up of 36% (as a percentage of body mass).[1]
1. Marieb, Elaine; Katja Hoehn (2007). Human Anatomy & Physiology (7th ed.). Pearson Benjamin Cummings. p. 317.