Norah Carr
Co-ordination and movement
Lo3.
March 2012.

3:1 eplain the sliding filament theory of muscle contraction with reference to the antagonistic muscles of the upper arm.

3:2. Draw and label a diagram of a synovial joint, explaining the functions of each structure.

3:3. Distinguish between a hinge, pivot and a ball and socket joint with reference to named examples, shapes of bones and the ranges of movement possible.

To understand the sliding filament theory, one should first look at the muscles. All movement through the body is created and stopped by muscles. Muscles work in antagonistic pairs, that means that when one muscle relaxes, it antagonistic pair will contract and vice versa. Muscle fibres are found in bundles wasting very little space. The muscle fibres which have bunches of myofibrils, which house myofilaments within.(thick myosin and thin actin filaments).
Once the brain decides it wants to contract a muscle, it sends a series of electrical impulses via chemical reactions called Action potentials, down to motor neurons which innervate muscle fibres. through a process called 'lateral inhibition' the brain will send an exictatory (contract) signal to one motor neuron and an inhibitory (relax) signal to the other.
Once the 'signal' (action potential) reaches the muscle fibre a series of events takes place, and very quickly: The Action potential travels along the axon of the motor neuron to the synaptic end bulb. This is an area of the neuron that contains vesicles of neurotransmitter. In this case the neurotransmitter is acetylcholine(ACH). Once the Action potential reaches the bulb, it opens voltage-gated calcium(Ca2+) channels on the bulb, and allows Calcium to enter the synaptic end bulb. When calcium is present, these vesicles filled with ACH bind to the membrane and are released into the synaptic cleft (junction between