Question

Pick a simple movement you perform everyday such as, sitting in a chair, drinking from a glass, etc. Explain how the movement occurs, including nerve roots, muscle contractions, angle of pull, etc. How would the movement change when various forces are applied to the movement (i.e. – drinking from a full glass versus an almost empty glass)?

Answer 1

For performing any function, there has to be a signal which should come from the nervous system and this signal will trigger muscles to do some movement. This pathway is called neuromuscular transmission. It is transfer of information from the motor nerve ending to the muscle fibre through neuromuscular junction. It is mechanism by which the motor nerve impulses initiate muscle contraction.

Taking example of picking a glass of water. Firstly , the impulse will be generated in the spinal cord which will activate the motor nerve which supplies the muscle of the hand and the digits.

This motor Nerve travels form the spinal cord and innervate the muscles of the arm like biceps, and the muscles of palm.

When action potential reaches the muscles, it cause generation of potential inside muscles which initiates the contraction of muscles.

Coordinates contraction of different muscles will eventually help in lifting the glass of water.

When the weight increase, the lifting power of the muscles will also increase. This can be proven by Frank starling law. It states that force of contraction of muscles is directly proportional to initial length of muscle fibres. So when more weight has to be lifted, more length of muscle will get activated.