Muscle Action and Mechanics Overview

Questions and Answers

What action do the antagonist muscles of the gluteus medius produce and on which side of the hip joint are they located?

Hip adductors produce adduction and are located on the medial side of the hip joint.

What do the names of the muscles adductor brevis, quadriceps femoris, tibialis anterior, and iliacus indicate?

Adductor brevis is a small muscle for adduction; quadriceps femoris has four heads; tibialis anterior lies in front of the tibia; iliacus overlies the iliac bone.

How do you identify whether a muscle is convergent, circular, fusiform, parallel, or pennate?

Which of the three lever systems involved in muscle mechanics is the fastest?

Third-class levers are the fastest levers. Signup and view all the answers

When using a lever to pry an old fence post out of the ground, should the fulcrum be closer to you or the post?

The fulcrum should be closer to the post. Signup and view all the answers

What facial muscles did Mario use to raise his eyebrows and wink?

Mario used the frontal belly of his epicranius to raise his eyebrows and the orbicularis oculi muscle to wink. Signup and view all the answers

How can the deltoid muscles both extend and flex the arm?

The deltoid has a broad origin; its anterior fibers flex and medially rotate the arm, while the posterior fibers extend and laterally rotate it. Signup and view all the answers

Which thenar muscle does not have an insertion on the bones of the thumb?

The opponens pollicis does not have an insertion on the bones of the thumb. Signup and view all the answers

What muscles contract to make a 'sad clown's face'?

The platysma, depressor anguli oris, and depressor labii inferioris muscles. Signup and view all the answers

What are prime movers?

Muscles that provide the major force for producing a specific movement. Signup and view all the answers

What is an agonist?

A molecule that stimulates a response by binding to a receptor site. Signup and view all the answers

What is an antagonist?

A muscle that opposes or reverses a prime mover. Signup and view all the answers

What is a synergist?

A muscle that aids a prime mover in a movement and helps prevent rotation. Signup and view all the answers

What are fixators?

Synergists that immobilize a bone or muscle's origin. Signup and view all the answers

What is a power lever?

A lever that operates at a mechanical advantage. Signup and view all the answers

What is mechanical advantage?

The ratio of the output force exerted by a machine to the input force applied. Signup and view all the answers

What are speed levers?

Levers with mechanical disadvantage that allow a load to be moved rapidly over a large distance. Signup and view all the answers

What is mechanical disadvantage?

A condition where the load is farther from the fulcrum than effort is applied, requiring greater effort than the load to move it. Signup and view all the answers

What is a first-class lever?

A lever for which the muscle force and resistive force act on opposite sides of the fulcrum. Signup and view all the answers

What is a second-class lever?

A lever where the load is between the fulcrum and the input force, never changing the direction of the input force. Signup and view all the answers

What is a third-class lever?

A lever where the fulcrum is at one end of the bar and the effort is between the fulcrum and the resistance. Signup and view all the answers

Study Notes

Muscle Action and Antagonism

The gluteus medius, located laterally, abducts the thigh while its antagonists, the hip adductors, are positioned on the medial side to produce adduction.

Muscle Naming Criteria

Adductor brevis: Indicates a small muscle responsible for thigh adduction.
Quadriceps femoris: Named for its four heads, aligning with the femur.
Tibialis anterior: Located in front of the tibia.
Iliacus: Positioned above the iliac bone.

Muscle Identification Types

Understand the differences in muscle types: convergent, circular, fusiform, parallel, and pennate based on structure and function.

Lever Systems in Muscle Mechanics

Third-class levers operate the fastest among the three types—first, second, and third-class levers.

Lever and Mechanical Advantage

For prying an old fence post, position the fulcrum closer to the post for mechanical advantage, requiring less force to lift the load.

Facial Muscles in Expression

The frontal belly of the epicranius raises eyebrows; the orbicularis oculi is responsible for winking.

Deltoid Muscle Actions

The deltoid muscle can both flex and extend the arm due to its broad origin and distinct anterior and posterior fiber contractions.

Thenar Muscles

The opponens pollicis is the only thenar muscle that does not attach to the thumb bones.

Facial Expression Muscles

To create a "sad clown's face," engage the platysma, depressor anguli oris, and depressor labii inferioris.

Functional Muscle Roles

Prime movers: Major force producers for specific movements.
Agonist: Binds to receptors to stimulate a response.
Antagonist: Opposes or reverses a prime mover's action.
Synergist: Assists a prime mover while preventing unwanted motion.
Fixators: Stabilize bone or muscle origins during movement.

Lever Types and Mechanical Advantage

Power lever: Operates with mechanical advantage, requiring less effort to move a load.
Mechanical advantage: Output force to input force ratio in a machine.
Speed lever: Operates at mechanical disadvantage for rapid movement.
Mechanical disadvantage: The load is further from the fulcrum than the effort applied, necessitating greater effort to move the load.
First-class lever: Muscle and resistive forces act on opposite sides of the fulcrum.
Second-class lever: The load is positioned between the fulcrum and input force, not changing the input force's direction.
Third-class lever: The effort lies between the fulcrum and the resistance, providing quicker movements.

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Description

This quiz explores key concepts related to muscle action, naming criteria, types of muscle identification, and lever systems in muscle mechanics. Understand the roles of various muscles and how their functions relate to movement and mechanical advantage.