Download the muscular system - Mr-Corrente

THE MUSCULAR SYSTEM
FUNCTIONS:
 Locomotion – All body movements and many body functions (arms,
heart, intestines…).
 Posture – Even when relaxed muscles are working to keep you upright
(neck, lower back…)
 Heat production – Body needs a basal temperature and muscles keep this
by releasing heat as a by-product of reactions.
There are 3 types of Muscle Tissue
1.
Smooth (visceral):
- usually found in hollow internal organs (stomach, intestines bladder)
- smooth muscle cannot be consciously contracted therefore it is said
to be an involuntary muscle
- smooth muscle lacks the appearance of striations
- smooth muscle cells are shorter than skeletal muscle cells
2.
Cardiac Muscle
-
3.
Occurs only in the heart
Controlled involuntarily
Can continue to function without nerve impulses
They are striated in appearance and the cells are joined end to end
Skeletal Muscle
-
Over 400
Contraction is voluntary
Striated in appearance (alternating dark and light bands)
When stimulated by a nerve fibre it contracts and relaxes
Includes both fast twitch and slow twitch fibers
They are attached to bones and are responsible for movement
Also used in talking, breathing, swallowing and singing.
Image Source: http://www.nytimes.com/imagepages/2007/08/01/health/adam/19841Typesofmuscletissue.html
ACTIONS OF THE MUSCULAR SYSTEM
Muscles that move in a specific manner are called agonists (prime movers)
whereas muscles that move opposite to the agonists are called antagonists.
Many muscles are paired in agonist – antagonist relations.
(Ex. Bicep and Tricep)
MUSCLE DEVELOPMENT
Most muscles have formed by the 8th week of pregnancy. Most women can
feel movement by the 17th week of pregnancy. At birth you have a fixed
amount of muscle fibers.
Growth of muscle cells depend on their use.
Atrophy – decrease in muscle cell diameter due to lack of contraction
demands
Hypertrophy – increase in muscle cell diameter due to increasing
contraction demands
HOW MUSCLE GROWS
Each muscle has a number of muscle fibers (c). This does not change in an
individual. Within each muscle fiber there are many myofibrils with protein
structures called actin and myosin. These structures pull on each other to
cause muscle contraction. When large demands are placed on the muscle,
the actin and myosin experience micro-tears. The body compensates by
healing these tears and adding new actin and myosin to the muscle fiber. As
more actin and myosin are added, the muscle fiber strengthens and grows.
TYPES OF MUSCLE CONTRACTION
1. Dynamic – Contraction with movement. Muscle shortens during
contraction. Movement at joint as a result of internal and external
force being unbalanced. Most of our muscle contraction is dynamic.
2. Static or Isometric - Internal and external force equal. No change
in muscle length during contraction.
No work is done (Work = FxD) but high amount of tension is
produced and muscle fatigue occurs quickly.
Examples: Gymnastics, wrestling, skiing, archery...