Jack Westin MCAT Podcast MCAT Biology: Step-by-Step Muscle Contraction (Neuromuscular Junction, Sarcomere & Rigor Mortis)
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Dec 9, 2025 Dive into the fascinating world of muscle contraction! Discover how signals travel from brain to bicep and the pivotal role calcium plays as the real puppet master. Unpack the differences among skeletal, cardiac, and smooth muscles. Enjoy a Romeo-and-Juliet analogy for troponin and tropomyosin's dramatic interaction. Learn about the crossbridge cycle and ATP's vital role in muscle action. Finally, uncover the mechanics behind rigor mortis and how it links to ATP absence after death.
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Classify Muscles By Striation And Control
- Memorize the three muscle types and their key visual/functional traits.
- Use 'striated vs non-striated' and 'voluntary vs involuntary' as quick identifiers for skeletal, cardiac, and smooth muscle.
Contraction Is A Multi-Chapter Story
- Muscle contraction is a multi-chapter story from motor neuron to sarcomere shortening.
- Acetylcholine and calcium are the core signals that bridge neuron firing to muscle force generation.
Neuron Uses Calcium To Release Acetylcholine
- Motor neurons deliver an action potential down long axons and trigger voltage-gated calcium entry at the axon terminal.
- That calcium causes acetylcholine vesicle release into the neuromuscular junction.