Muscle Anatomy and Levers Quiz

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Questions and Answers

What is the primary function of the serratus anterior muscle?

Extends the arm

Adducts the scapula

Flexes the humerus

Abducts the scapula (correct)

Which of the following actions is performed by the trapezius muscle?

Flexion of the arm

Elevation of the ribs

Adduction of the scapula (correct)

Abduction of the humerus

What type of movement does the deltoid muscle primarily facilitate?

Abduction of the arm (correct)

Depression of the scapula

Rotation of the scapula

Elevation of the shoulder girdle

Which muscle assists in pushing and punching actions?

Serratus anterior Signup and view all the answers

What is the function of the muscles that move the pectoral girdle?

Move the clavicle and scapula Signup and view all the answers

What type of muscle is under voluntary control?

Skeletal muscle Signup and view all the answers

What is the role of muscle bellies in muscle anatomy?

They are the thickened portion between tendons. Signup and view all the answers

In muscle contractions, what happens to the origin and insertion during reverse muscle actions?

They are reversed. Signup and view all the answers

Which levers are the most common type found in the human body?

Third-class levers Signup and view all the answers

What mechanical advantage do second-class levers provide?

They require minimal effort. Signup and view all the answers

What is the primary effort involved when standing on your toes?

Gastrocnemius muscle Signup and view all the answers

In a third-class lever, where is the effort located?

Between the fulcrum and load Signup and view all the answers

Why are third-class levers used more commonly despite their mechanical disadvantage?

They can move the load faster. Signup and view all the answers

What is the role of the triceps brachii during flexion at the elbow joint?

It relaxes to allow movement. Signup and view all the answers

What muscles stabilize joints to allow for movement at only one joint?

Synergists Signup and view all the answers

Which muscle is responsible for elevating the mandible during chewing?

Masseter Signup and view all the answers

What is the function of the external obliques in the abdominal muscles?

To protect the abdominal viscera Signup and view all the answers

What does the term 'fixators' refer to in muscle action?

Muscles that stabilize one end of a bone Signup and view all the answers

What movement is produced when both biceps brachii and triceps brachii contract simultaneously?

Stabilization of the elbow joint Signup and view all the answers

Which of the following muscles runs parallel to the midline of the abdomen?

Rectus abdominis Signup and view all the answers

What is the primary action of the orbicularis oculi muscle?

Close the eyelid Signup and view all the answers

Which muscle is considered the deepest of the abdominal muscles?

Transversus abdominis Signup and view all the answers

What defines the '6–8 pack' in the rectus abdominis?

Tendinous intersections Signup and view all the answers

What describes the action of the sternocleidomastoid muscle during unilateral movement?

Rotates the head Signup and view all the answers

What does the diaphragm do during breathing?

Expands the thoracic cavity Signup and view all the answers

What muscle originates from the scapula and stabilizes it during shoulder movement?

Pectoralis minor Signup and view all the answers

Which compartment of muscles functions to flex the wrist?

Flexor compartment Signup and view all the answers

Study Notes

Skeletal Muscle

All skeletal muscles are under voluntary control
Functions of skeletal muscle:
- Support body movement
- Generate heat

Muscle Anatomy

Origin: End of a muscle attached to a stabilized bone (usually proximal)
Insertion: End of a muscle attached to a moving bone (usually distal)
Muscle belly is the thicker portion between tendons
Actions: The movements that are possible when a muscle contracts
Reverse muscle actions (RMAs) occur when the origin and insertion are reversed. This can happen in some muscles, but NOT when the muscle relaxes

Levers

Fulcrum: A fixed point that a lever rotates around
Lever: A rigid bar that pivots around a fulcrum
Load: Resistance against effort
Effort: Force required to move a load
Bones are levers that are moved by the effort of muscle action

Types of Levers

First-class lever: Fulcrum is between the effort and the load.
- Examples: Scissors, looking up at the ceiling
Second-class lever: The load is between the effort and the fulcrum.
- Examples: Wheelbarrow, standing on your toes.
- Produce a mechanical advantage
Third-class lever: The effort is between the fulcrum and the load.
- Examples: Forceps, bending your elbow
- Most common type in the body
- Always produce a mechanical disadvantage

Why so many third-class levers?

They allow for faster movement of the load.

Muscle Groups

Muscles usually work in opposing pairs

Agonist & Antagonist Muscles

Agonist: The muscle that contracts to produce a movement.
Antagonist: The muscle that opposes the agonist. It must relax to allow the agonist to move the bone.

Synergist Muscles

Synergist muscles stabilize joints when contracted to allow movement around only one joint.

Fixators

Fixator muscles stabilize the proximal end of the bone so the distal end can move.
Fixators often work with agonist muscles.

Compartments

Compartments are groups of skeletal muscles, nerves, and blood vessels that have specific functions.
Example: Flexor compartments of the upper limb are the anterior muscles

Naming Muscles

Muscles are named based on:
- Direction of muscle fibers
- Size
- Shape
- Action
- Number of origins
- Location
- Origin and insertion

Facial Muscles

Functions:
- Express emotions
- Speech and vocalization
- Chewing (mastication)

Muscles of the Eye and Mouth

Orbicularis oculi: Closes the eyelid
Orbicularis oris: Closes the lips and purses lips
Occipitofrontalis: Has two bellies:
- Frontal belly: Raises eyebrows and wrinkles the forehead.
- Occipital belly: Raises hair and pulls the scalp posteriorly.
- Connected by the epicranial aponeurosis

Muscles that Move the Mandible

Platysma: Pulls the corners of the mouth laterally and inferiorly; depresses the mandible.
Masseter and Temporalis: Elevate the mandible.
Masseter closes the jaw.

Muscles of the Neck

Sternocleidomastoid: Muscle on each side of the neck, rotates the head.
- Can also extend the head and elevate the sternum.
- Capable of RMAs

Muscles of the Abdomen

Funtions:
- Protect the abdominal viscera
- Move the vertebral column
External obliques: Most superficial layer
Internal obliques: Intermediate layer
Transversus abdominis: Deepest layer

Rectus Abdominis

Runs longitudinally along the anterior abdominal cavity
Divided by tendinous intersections

Diaphragm

Bound the thoracic cavity inferiorly
Insertions: Central tendon
Contracts during breathing

Muscles that Move the Pectoral Girdle

Functions:
- Move the clavicle and scapula
- Stabilize the scapula during movement of the humerus

Serratus Anterior

Fan-shaped muscle that abducts the scapula.
Assists in pushing and punching.

Trapezius

Muscle that originates on the occipital bone and inserts on the scapula.
Permits rotation, adduction, depression, and stabilization of the scapula

Muscles that Move the Upper Limb

Pectoralis major: Permits adduction, medial rotations, and flexion of the arm.

Deltoid

Wraps the shoulder posteriorly, laterally, and anteriorly.
Permits abduction, medial/lateral rotation, and flexion/extension of the arm.

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Description

Test your knowledge on skeletal muscle anatomy and the mechanics of levers in the human body. This quiz covers key concepts such as muscle actions, types of levers, and their functions. Perfect for students studying human anatomy or physiology.