Types of muscle

• This is always attached to the skeleton, and is under voluntary control via the motor neurones of the somatic nervous system. It can be subdivided into red (slow) muscle and white (fast) muscle.
• This is a special type of red skeletal muscle. It looks and works much like skeletal muscle, but is not attached to skeleton, and is not under voluntary control.
• This is found in internal body organs such as the wall of the gut, the uterus, blood arteries, the iris, and glandular ducts. It is under involuntary control via the autonomic nervous system or hormones. Smooth muscle usually forms a ring, which tightens when it contracts, so there is no need of a skeleton to pull against.
• Skeletal muscles cause the skeleton to move at joints.
• They are attached to the skeleton by tendons, which transmit the muscle force to the bone and can also change the direction of the force.
• Tendons are made of collagen fibers and are very strong and stiff (i.e. not elastic).
• The skeleton provides leverage, magnifying either the movement or the force.
• Muscles are either relaxed or contracted.
• In the relaxed state muscle can be stretched
• In the contracted state muscle exerts a pulling force.
• Since muscles can only pull (not push), they work in pairs called antagonistic muscles.
Antagonistic Muscles
Question
• How Does the role of tendons and ligaments differ?
• Why do muscles work in pairs?
Each muscle fibre is actually a single muscle cell about 100µm in diameter and a few cm long. These giant cells have many nuclei, as they were formed from the fusion of many smaller cells. Their cytoplasm is packed full of myofibrils, bundles of proteins filaments that cause contraction, and mitochondria to provide energy for contraction.
A single muscle (such as the biceps) contains around 1000 muscle fibers running...

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