Workings of the Muscular System

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Muscular System Animations

1. How do nerve impulses cause muscle contraction?
Skeletal muscle is under voluntary control. Nerve impulses that originate in the central nervous system cause muscles to contract. Both neurons and muscle tissue conduct electrical current by moving ions across cellular membranes. A motor neuron ends in a synapse with a muscle fiber. The neuron releases acetylcholine and transfers the action potential to the muscle tissue. The signal will travel through the tissue and trigger the contraction of individual sarcomeres. One synapse generally controls an entire muscle fiber. One motor neuron usually controls several adjacent muscle fibers. A group of fibers under the control of a single motor neuron is known as a motor unit.

2. What is the pathway of energy transfer during muscle movement? The contraction of skeletal muscles is one of the most energetically expensive activities that the body does on a regular basis. Adenosine triphosphate (ATP) is split into adenosine diphosphate (ADP) and phosphate to supply the energy for muscle contraction. The free energy released by the ATP when the phosphate is split off is transferred to the heads on the myosin filaments. The heads move and store potential energy in their new position. When the heads interact with actin, the energy is used to slide the filaments past one another transferring the energy into movement (kinetic energy).

3. What are neurotransmitters?
Nervous impulses are electrical signals that travel along neurons. The electrical signals cannot travel from one neuron to the next directly. The signal crosses the gap, called a synapse, between cells in chemical form. One neuron releases chemicals in response to an action potential (nerve impulse). The chemicals travel across the synapse and stimulate an action potential in the next neuron. These chemicals are known as neurotransmitters. Neurotransmitters are stored in vesicles within a neuron and released through...
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