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Muscle Contractions • NMJ • Skeletal Muscles Cheat Sheet (DRAFT) by

A comprehensive study guide for A&P OpenStax covering the muscular system (Chapters 9–11). This includes muscle tissue types, neuromuscular junctions, sliding filament theory, ATP and calcium roles, and major muscle groupings. Perfect for a quiz and test review.

This is a draft cheat sheet. It is a work in progress and is not finished yet.

NMJ Activation

 
Muscle contra­ction begins when a motor neuron releases acetyl­choline (ACh) at the neurom­uscular junction (NMJ). This causes depola­riz­ation of the sarcolemma and triggers an action potential that travels along the T-tubules.

Calcium Release

 
The action potential stimulates the sarcop­lasmic reticulum (SR) to release calcium ions (Ca²⁺). These ions bind to troponin, causing tropom­yosin to move and expose myosin­-bi­nding sites on actin.

Cross-­Bridge & Relaxation

 
Myosin heads bind to actin, perform the power stroke, and shorten the sarcomere. ATP allows detachment and re-coc­king. When the signal stops, Ca²⁺ is reabsorbed and the muscle fiber relaxes.
  

Muscle Contra­ction Overview

Muscle Relaxation Overview