BIOLOGY OCR ADDITIONAL

JOINTS AND MUSCLES

• Ligaments have good tensile strength.
• Cartilage acts as shock absorber
• Synovial membranes release oily synovial fluid to lubricate joints
• Muscles work in antagonistic pairs
• Joints act like pivots and long bones like levers

Artificial joint replacement can have disadvantages: 

• Body can react to the foreign body and the site can become inflamed and painful.
• Risk of dislocation
• Risk blood clots
• If hip replacement, length of legs can change, cause difficulty walking
• Not permanent, need replacing after 12-15 years

THE HEART

The double circulatory system

• Blood loses pressure as travels through body
• Blood pressure is systolic (when heart contracts) over diastolic (when heart relaxed
• If only 2 chambered heart, single circulatory system, eg. fish
• Humans have double circulatory system
• Blood supply to organs alters to fit requirements

Cardiac cycle (sequence of events in 1 whole heartbeat) 1. Blood into atria through Vena cava and Pulmonary vein 2. SAN-Atria contract, blood to ventricles 3.AVN- Ventricles contract, blood out through Aorta and Pulmonary artery

• Galen- thought: heart sucked not pumped, arterial blood made by heart…