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Muscle Contractions

Muscle Contractions. Goal: . I will be able to explain how electrochemical impulses are brought to my skeletal muscles. Electrochemical Impulses. Electrochemical impulses are sent from the Central Nervous System (brain and spinal cord) to muscles causing contractions called a muscle twitch .

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Muscle Contractions

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  1. Muscle Contractions

  2. Goal: • I will be able to explain how electrochemical impulses are brought to my skeletal muscles.

  3. Electrochemical Impulses • Electrochemical impulses are sent from the Central Nervous System (brain and spinal cord) to muscles causing contractions called a muscle twitch. • The nervous system consists of nerve cells called neurons. • Nervous system

  4. Nerve Cell – motor neuron

  5. Motor Neurons • All animal cells have a separation of positive and negative charges across the plasma membrane called a membrane potential. • Motor neurons have a resting potential (-70 mV) and when excited undergo depolarization which creates an action potential (+40mV). • Depolarization occurs because there is an influx of sodium ions (Na+) into the cell. • An action potential reaches the axon terminal causing Ca2+ to enter the cell. • This causes the neurotransmitter acetylcholine to be released allowing the action potential to continue to the next motor neuron.

  6. The process continues until the impulse reaches a muscle. • Electrical energy is converted into chemical energy and then mechanical energy causing the muscle to move.

  7. Neurons • Neural Impulse Animation • Chemical Signals

  8. Motor Unit (Fig. 3.3 on page 35)

  9. Motor Units • Motor units are considered either small or large depending on the number of muscle fibers it stimulates. • Large muscles usually have large motor units.

  10. All or None Principle • A motor unit that is stimulated to contract , will do so to its fullest potential. • This is referred to as the all-or-none principle.

  11. Work • Read pages 34 - 35

  12. In this synapse, which structure represents the synaptic cleft? • In this synapse, which structure represents the axon terminal of a presynaptic cell? • What is happening in structure B. • In structure D, neurotransmitter molecules diffuse across the cleft and bind to receptors in the plasma membrane of the postsynaptic cell. What happens next.

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