Muscular and Skeletal System
Muscular System
- Types of muscle: There are three types of muscle in the human body: the skeletal, which is associated with the bony structure; the cardiac in the heart and the smooth, located in the walls of organs and structures such as the esophagus, stomach, intestines, bronchi, uterus, urethra, and blood vessels.
- Muscle contraction: refers to the process where muscles become shorter and tighter. The motor neuron sends a signal to the muscle cells which triggers calcium to be released. This starts a chain reaction resulting in muscle contraction.
- Fast and slow-twitch fibres: muscles have two types of fibres. Slow-twitch fibres (type I) are aerobic, have slow speed of contraction but are resistant to fatigue. Fast-twitch fibres (type II) are anaerobic, have high speed of contraction and tire easily.
Skeletal System
- Functions of the skeleton: The skeleton has five main functions: providing support to the body, aiding movement, protecting internal organs, producing blood cells and storing minerals.
- Types of bone: There are five categories: long bones, such as the femur; short bones, found in the wrist and ankle; flat bones, like the scapula; irregular bones, including the vertebrae; and sesamoid bones, like the patella.
- Bone structure: A typical long bone has two parts: the diaphysis (the shaft) and the epiphysis (the two ends). Between these is the epiphyseal plate, where growth in bone length occurs in children and adolescents.
- Joints: the point at which two or more bones meet. They can be categorised into three main types - fibrous joint (immovable, e.g. skull plates), cartilaginous joint (slightly movable, e.g. spinal vertebrae), and synovial joint (freely movable, e.g. knees and wrist).
Interaction of Muscular and Skeletal Systems
- Functioning together: Muscles are attached to bones by tendons. When muscles contract, they pull on the bones causing them to move. This coordinated action is what allows us to move.
- Muscle groups: Muscles work in pairs, an agonist and an antagonist. When one muscle in the pair (the agonist) contracts, the other muscle (the antagonist) relaxes. This allows fine control of movement.
- Lever systems: Muscles and bones interact to form lever systems. The muscle acts as the effort, the joint serves as the fulcrum, and the bone that is moving acts as the lever.