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How Muscular Contraction Causes Articulation: Definition & Types

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  • 0:06 Muscles Cause Movements
  • 1:07 Origin and Insertion
  • 1:26 Types of Articulation
  • 3:14 Rotational Articulation
  • 4:12 Special Articulation
  • 5:49 Lesson Summary
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Lesson Transcript
Instructor: John Simmons

John has taught college science courses face-to-face and online since 1994 and has a doctorate in physiology.

Skeletal muscle contraction causes all types of movement. Movement at our joints is referred to as articulation. All articulation is described in reference to the anatomical position, and most articulations are identified in opposite pairs. This lesson identifies and describes the major articulations of the human body.

Muscles Cause Movement

We all know that our body parts move due to muscular contraction. To describe the type of movement, on the other hand, is not so simple. Using words such as bend, raise, or lower don't help as much, as the observer's frame of reference can change and, therefore, change the meaning of a term. For example, raising your hand is a different movement if you are sitting in a classroom compared with lying down in bed.

Therefore, we have come up with terms to describe specific movements. All movement is described in reference to the anatomical position, in which a person is standing up straight with the palms of their hands and the toes of their feet pointing forward. Muscular contraction produces an articulation, or a movement, at a joint. We will use examples to describe various types of articulation caused by muscular contraction.

Origin and Insertion

Muscle contraction results in different types of movement. The particular movement is a direct result of the bones to which the muscle is attached. The origin is the point of attachment to bone that doesn't move, while insertion moves the bone during contraction.

Types of Articulation

Flexion and extension are opposite movements of a limb.
Flexion Extension of Limbs

The human body has well over 500 muscles responsible for all kinds of movement. Flexion and extension describe opposite movement of a limb. Keep in mind, these movements are all described relative to the anatomical position. Flexion is movement that decreases the angle between the articulating parts. In forearm flexion, the angle is decreased between the arm and the forearm. Conversely, the same angle is increased during forearm extension.

Hyperextension occurs when extension simply continues past the anatomical position. For example, you hyperextend your neck when you look up at the stars.

Abduction and adduction describe opposite articulations as well. Abduction is the movement of an appendage to the side and away from the midline of the body. A person abducts their arm when they reach out to hold someone's hand. Likewise, when somebody is abducted, they are taken away, just as abduction moves an appendage away from the body.

Spreading your toes is an example of abduction.
Abduction Spreading Toes

Let's look at the opposite - adduction. Adduction is just the opposite of abduction. It's the movement of an appendage towards the body's midline. Additionally, spreading your fingers and spreading your toes is abduction, while drawing them together is adduction. During adduction, the appendage is added or drawn to the body - that'll help you remember that term.

Rotational Articulation

Rotating your arm or leg in circles is called circumduction.
Circumduction Example

A number of articulations involve circular movements. For example, circumduction describes the movement of an appendage in a loop or a circle. Making small circles with your arms, your legs, or head are all examples of circumduction.

Furthermore, we use rotation to gesture a negative response with our head as we rotate it back and forth or side to side to say 'no.' We can rotate our shoulders and, to a lesser degree, our hips as well.

We have special names for rotation of the hands and wrists without rotating the shoulder. If we rotate the hand or wrist so the palm faces behind us, we say we are performing pronation. Rotating the hand back to the anatomical position is supination.

Special Articulations

We have some special names for articulation of some joints. For example, inversion is the twisting of the foot that turns the soles towards the midline, whereas eversion, the opposite, moves the sole away from the midline. Dorsiflexion is flexion of the ankle that elevates the sole, whereas plantar flexion is the opposite and is flexion of the ankle that elevates the heel. As the angles of the body parts described above are both decreased, they are both flexion.

Opposition is the movement of the thumb towards the palm. This is a special articulation that makes primates unique among other animals and allows us to grasp things in our hands, such as hammers and other tools.

Protraction occurs when you lean your head forward.
Protraction Example

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