S-Cool Revision Summary

S-Cool Revision Summary

Locomotion is generally brought about by a system of muscles in conjugation with a skeleton. The skeleton may be an endoskeleton, an exoskeleton or a hydrostatic skeleton. The support system will be adapted to methods of locomotion for a particular animal (e.g, flying, swimming, climbing, and walking).

It consists of bone, cartilage, tendons and ligaments.

Its functions are:

Support.

Protection of soft tissue.

Movement - a point of attachment for muscles.

Production of red blood cells and some white blood cells.

A source (sink) for calcium and phosphate.

Cartilage is firm but elastic. Cartilage cells are called chondrocytes. They secrete a hard, rubbery matrix around themselves.

They also secrete collagen fibres that become embedded in the matrix to strengthen it. The cells themselves live in small cavities in the matrix called lacunae.

Movement is made more flexible with joints. Here, ligaments hold bones together. They limit the movement thus preventing dislocation. The joints move due to the force of muscles acting on them.

Muscles are attached to bones by tendons that are made of collagen fibres. When a muscle contracts, the tendon and its attached bone are pulled towards the contracting muscle.

Each muscle is called a fibre. Each fibre made up of a bundle of myofibrils.

Each myofibril is made of myofilaments - actin and myosin.

The myofilaments are arranged so that each myosin is surrounded by 6 actins.

Actin: consists of 2 threads wrapped around each other. At each twist there is a binding site for myosin. In a relaxed state, a molecule called tropomyosin covers these sites.

Myosin: the filament consists of many myosin molecules. Each molecule has a tail and a double globular head.

Contraction occurs when an impulses from a motor neurone reaches the synapse at the junction with the muscle. If it is stronger than a threshold stimulus contraction will occur.