IB HL SEHS Notes

Summary:

The skeletal system comprises the axial and appendicular skeleton. The axial skeleton forms the central body axis and includes the cranium, ribs, vertebral column, and more. The appendicular skeleton is vital for movement and consists of bones like the limbs, scapulae, and clavicles. The axial skeleton protects organs, supports posture, and stores minerals, while the appendicular skeleton provides attachment points for muscles and enables movement. Bones are classified into four types: long bones (e.g., femur), short bones (e.g., carpals), flat bones (e.g., scapulae), and irregular bones (e.g., vertebrae).

Connective tissues like cartilage, ligaments, and tendons provide support and stability in joints. Joints are points where bones articulate and can be fibrous (limited movement), cartilaginous (limited movement, often with cartilage), or synovial (greater range of movement with synovial fluid). Synovial joints have features like synovial membrane, articular capsule, cartilage, and synovial fluid. They come in various types: hinge (e.g., elbows), ball and socket (e.g., shoulders), condyloid (e.g., hand), pivot (e.g., neck), gliding (e.g., ankle), and saddle (e.g., thumb).

Excerpt:

IB HL SEHS Notes

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1.2 THE MUSCULAR SYSTEM

1.2.1 Outline the general characteristics common to muscle tissue

• Contractility – the ability of muscle cells to actively generate force, to undergo shortening for movements to bring about dynamic movements
• Extensibility – the ability of a muscle to stretch without damage within the permitted rage of movement; allows quick changes in the range of movement (ROM)
• Elasticity – the ability of muscle tissue to return to its original shape after a contraction/extension; helps store energy for movement
• Atrophy – the ability of muscles to waste away when not being utilized; there is a decrease in the size of muscle fibre diameter
• Hypertrophy – the ability of a muscle to grow in size, generally by increasing the size of muscle cells without division
• Excitability – the ability to quickly respond to stimuli
• Controlled by nerve stimuli – the ability of the muscle tissue to be stimulated by electrical impulses/excitability/conductivity; muscles work in pairs through reciprocal inhibition
• Feb by capillaries – the capillaries supply the muscle with oxygen and nutrients/remove waste products; there may be a small amount of hypertrophy due to blood moving into the muscle