Question

Muscle/Neural Tissue Worksheet Ex.

1. What is the specific function of calcium in a muscle cell?

2.Once calcium has done it's job in the muscle cell, myosin is able to bind to actin's _________ creating ________ .

3. List 3 places in a muscle cell where ATP energy would be used.

4. Describe one way you could cause flaccid paralysis at the neuromuscular junction.

Answer 1

1. The role of Ca²⁺ in the muscle fibres is of regulatory and signaling molecule (as a secondary messenger) as the contractile functions of the fibres are dependent on the variable expression Ca²⁺ signaling and handling proteins namely the ryanodine receptor (sarcoplasmic reticulum Ca²⁺ release channel), the troponin complex (mediates the Ca²⁺ effect to the myofibrillar structure for the muscle contraction), calsequestrin, the (Ca²⁺storage protein in the SR) and the Ca²⁺pump (protein responsible for the Ca²⁺ reuptake into the SR).
   The mechanism of control of contraction and relaxation of the muscle fibre regulated by Ca²⁺ is as follows:

1. troponin-tropomyosin system associated with the actin filaments, found in skeletal and cardiac muscles.
2. The calmodulin system where the calmodulin (CaM) with the calcium ion, activates myosin light-chain kinase resulting the phosphorylation of the myosin light chains which initiates muscle contraction, found in the smooth muscles
3. Direct binding of Ca²⁺ to myosin to regulate the contraction of the muscle fibres, found in lower vertebrates

2. Once calcium has done it's job in the muscle cell, myosin is able to bind to actin's filament creating a crossbridge
3. The energy required for the motion of muscle shortening occurs as myosin heads bind to actin and pull the actin inward is provided by ATP.
4. Curare acts as a neuromuscular junction blocking agent and can be used to induce a flaccid paralysis