Week 10 - Muscle Contraction Review: Explain 1

 Week 10 - Muscle Contraction Review: Explain 1

From Muscle Excitation to Contraction: A Review

Please review the following information to help us remember how muscle cells generate contraction:

A motor unit is a single motor neuron comprised of an “upper-motor neuron” and “lower-motor neuron”. When your brain decides to move a muscle 

• (1), “upper motor neurons” from your motor cortex send a message down your spinal cord
• (2), where they synapse with "lower motor neurons"
• (3). These motor neurons then synapse with muscle fibers 
• (4), and releaser ACh across the neuromuscular junction 
• (5). Each muscle fiber contains myofibrils. Each myofibril within a muscle fiber contains sarcomeres, comprised of actin and myosin contractile proteins. 
• (6a), that allow for contraction.
• (6b), via myosin/actin chains sliding across each other.
• (6c). This is the final step in the contraction cycle that causes muscles to physically shorten and contract.

1. But what exactly happens after ACh is released from the neuromuscular junction that allows actin and myosin to pull on each other?
2.  Does it require energy? If so, where does that energy come from? Let's explore a bit more!