Sistema Muscular: Ação dos músculos (macete fácil de aprender) - Anatomia Humana - VideoAula 023

Key Concepts

Muscle contraction, articulation movement, flexion, extension, abduction, adduction, lateral inclination, agonist muscle, antagonist muscle, anterior, posterior, lateral, medial, knee exception, plantar flexion, dorsiflexion.

Muscle Actions: A Simple Guide

Introduction

The video addresses the common difficulty students face in understanding muscle actions, particularly concerning origin, insertion, and action. It presents a simplified rule to easily determine muscle actions based on their position relative to articulations.

Muscle Structure and Function

Muscles are designed to contract, which results in movement at articulations. The speaker uses a diagram with two bones, an articulation, and a "wire" representing a muscle to illustrate this. When the muscle contracts, it moves the articulation. Each articulation has specific degrees of movement, with some having restrictions (e.g., shoulder vs. elbow).

Determining Muscle Actions: The General Rule

The key to understanding muscle actions lies in identifying where the muscle crosses an articulation (anterior, posterior, lateral, or medial). To visualize this, the speaker uses the example of cutting the arm transversely between the elbow and shoulder, creating four compartments: anterior, posterior, lateral, and medial.

Flexion and Extension

• Flexion: Muscles crossing the anterior part of an articulation generally cause flexion (movement forward). Examples include:
  • Shoulder flexion: Muscles in front of the shoulder move it forward.
  • Elbow flexion: Muscles in front of the elbow bend it.
  • Wrist flexion: Muscles in front of the wrist bend it forward.
  • Finger flexion: Muscles in front of the fingers bend them.
  • Neck flexion: Muscles in front of the neck move it forward.
  • Trunk flexion: Abdominal muscles move the trunk forward.
• Extension: Muscles crossing the posterior part of an articulation generally cause extension (movement backward or straightening). Examples include:
  • Shoulder extension: Muscles behind the shoulder move it backward.
  • Elbow extension: Muscles behind the elbow straighten it.
  • Wrist extension: Muscles behind the wrist bend it backward.
  • Finger extension: Muscles behind the fingers straighten them.
  • Neck extension: Muscles behind the neck allow looking up.
  • Trunk extension: Muscles in the posterior lumbar spine straighten the trunk.

The speaker emphasizes the concept of agonist and antagonist muscles, where the agonist is the primary mover and the antagonist opposes that movement.

Example: The brachialis and biceps muscles (anterior elbow) cause elbow flexion, while the triceps (posterior elbow) causes elbow extension.

Abduction, Adduction, and Lateral Inclination

• Abduction: Muscles on the lateral side of a limb generally cause abduction (movement away from the midline).
  • Example: Shoulder abduction (raising the arm to the side).
• Adduction: Muscles on the medial side of a limb generally cause adduction (movement towards the midline).
  • Example: Shoulder adduction (lowering the arm to the side).
• Lateral Inclination: For the neck and trunk, lateral movements are called lateral inclination. Muscles on the lateral side of the trunk or neck cause inclination to that side.

The Knee: Exception to the Rule

The knee is presented as the primary exception to the general rule. Muscles crossing the anterior part of the knee (quadriceps) cause extension, while muscles crossing the posterior part (hamstrings) cause flexion. This is the opposite of the general rule. The speaker explains that the knee's articulation is similar to the elbow, but its movement is inverted.

Other Articulation-Specific Terminology

The speaker mentions that some articulations have specific terms for flexion and extension. For example, in the foot:

• Plantar flexion: Moving the foot downwards.
• Dorsiflexion: Moving the foot upwards.

Future Topics

The next video will focus on the muscles of the upper limbs (shoulder, elbow, wrist, and fingers) and how the presented rule applies to them.

Conclusion

The video provides a simplified method for understanding muscle actions based on their position relative to articulations. By understanding the general rule and the exception of the knee, students can more easily determine the actions of various muscles. The speaker encourages viewers to like, favorite, and subscribe for more content.