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Questions and Answers
Which facial muscle is responsible for closing the eyes?
Which facial muscle is responsible for closing the eyes?
What is the action of the masseter muscle during mastication?
What is the action of the masseter muscle during mastication?
Which muscle is responsible for raising the eyebrows and wrinkling the forehead?
Which muscle is responsible for raising the eyebrows and wrinkling the forehead?
Which muscle aids in the elevation of the sternum?
Which muscle aids in the elevation of the sternum?
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What role do the external intercostals play during breathing?
What role do the external intercostals play during breathing?
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What is the primary function of the orbicularis oris?
What is the primary function of the orbicularis oris?
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Which muscle is involved in flexing and laterally flexing the neck?
Which muscle is involved in flexing and laterally flexing the neck?
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What is the primary action of the supraspinatus muscle?
What is the primary action of the supraspinatus muscle?
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Which muscle functions as a synergist to assist in arm movement?
Which muscle functions as a synergist to assist in arm movement?
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The internal intercostals are primarily responsible for which aspect of respiration?
The internal intercostals are primarily responsible for which aspect of respiration?
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What action is primarily performed by the biceps brachii?
What action is primarily performed by the biceps brachii?
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Which of the following muscles extends the fingers?
Which of the following muscles extends the fingers?
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Which muscle is responsible for rotating the arm laterally?
Which muscle is responsible for rotating the arm laterally?
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What is a function of the flexor carpi radialis?
What is a function of the flexor carpi radialis?
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Which muscle extends and adducts the arm?
Which muscle extends and adducts the arm?
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What role do the rotator cuff muscles serve in relation to the shoulder joint?
What role do the rotator cuff muscles serve in relation to the shoulder joint?
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What is the main advantage of using a power lever?
What is the main advantage of using a power lever?
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In a third-class lever, where is the effort applied in relation to the load and fulcrum?
In a third-class lever, where is the effort applied in relation to the load and fulcrum?
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Which of the following statements is true regarding levers operating at mechanical disadvantage?
Which of the following statements is true regarding levers operating at mechanical disadvantage?
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What characterizes a second-class lever?
What characterizes a second-class lever?
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How does fiber length influence range of motion (ROM) in muscles?
How does fiber length influence range of motion (ROM) in muscles?
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What does a greater cross-sectional area of a muscle primarily affect?
What does a greater cross-sectional area of a muscle primarily affect?
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What type of lever is a seesaw typically classified as?
What type of lever is a seesaw typically classified as?
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Which of the following is a characteristic of speed levers?
Which of the following is a characteristic of speed levers?
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What is the primary role of the prime mover in muscle action?
What is the primary role of the prime mover in muscle action?
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What is the function of a synergist muscle?
What is the function of a synergist muscle?
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In the context of muscle attachments, what is the origin?
In the context of muscle attachments, what is the origin?
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Which of the following best describes the role of an antagonist muscle?
Which of the following best describes the role of an antagonist muscle?
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What is the role of the fulcrum in a lever system?
What is the role of the fulcrum in a lever system?
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Which of the following components is considered the 'load' in a lever system?
Which of the following components is considered the 'load' in a lever system?
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Which of the following muscle types would most likely act as a fixator?
Which of the following muscle types would most likely act as a fixator?
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Which statement accurately describes the relationship between prime movers and antagonists?
Which statement accurately describes the relationship between prime movers and antagonists?
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Which muscle group is primarily responsible for extending the knee?
Which muscle group is primarily responsible for extending the knee?
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What is the primary function of the iliopsoas muscle group?
What is the primary function of the iliopsoas muscle group?
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Which muscles are included in the erector spinae group?
Which muscles are included in the erector spinae group?
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Which of the following muscles is an adductor that also extends and flexes the thigh?
Which of the following muscles is an adductor that also extends and flexes the thigh?
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What is the primary role of gluteus medius in thigh movement?
What is the primary role of gluteus medius in thigh movement?
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Which muscle is NOT considered part of the quadriceps group?
Which muscle is NOT considered part of the quadriceps group?
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What common issue arises from overstretched thigh muscles?
What common issue arises from overstretched thigh muscles?
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Which of the following muscles is involved in flexing both the thigh and knee?
Which of the following muscles is involved in flexing both the thigh and knee?
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Study Notes
Levers and Mechanical Advantage
- Levers allow the effort to move heavier loads or move the load faster or farther, depending on the fulcrum position relative to the load and effort.
- Mechanical advantage (power lever): load is close to the fulcrum with effort farther away, allowing a smaller effort to move a larger load.
- Mechanical disadvantage (speed lever): load is far from the fulcrum with effort close by, allows the load to move rapidly over a large distance, offering a wider range of motion.
Classes of Levers
- First-class lever: Fulcrum is between the load and effort. Examples: seesaw, scissors.
- Second-class lever: Load is between the fulcrum and effort. Examples: wheelbarrow, standing on toes.
- Third-class lever: Effort is applied between the fulcrum and load. Examples: tweezers, forceps, most skeletal muscles.
Lever Systems
- Systems operating under mechanical disadvantage lose force but gain speed and range of movement.
- Systems operating under mechanical advantage are slower but offer more stability.
Muscle Actions and Interactions
- Muscles can only pull, they cannot push.
- Prime mover (agonist): Has primary responsibility for a movement.
- Antagonist: Opposes or reverses a particular movement.
- Synergist: Helps prime movers, adds extra force to movement, reduces undesirable movement.
- Fixator: Type of synergist that immobilizes bone or a muscle’s origin to give the prime mover a stable base to work on.
Muscle Actions and Interactions
- Origin: Stationary end of the muscle.
- Insertion: Movable end of the muscle.
- Action: Movement that occurs when the muscle contracts, the insertion is usually pulled towards the origin.
Leverage Systems
- Most skeletal muscles move using leverage.
- Lever: Rigid bar (bone) that moves on a fixed point called the fulcrum (joint).
- Effort: Force (supplied by muscle contraction) applied to the lever to move the resistance (load).
- Load: Resistance (bone + tissues + any added weight) moved by the effort.
Muscles of the Head: Facial Expression
- Facial expression muscles are different because they insert onto skin rather than bone.
- Occipitofrontalis (Epicranium): Raises eyebrows, wrinkles forehead.
- Orbicularis oculi: Closes eyes (blink).
- Orbicularis oris: Purses lips (kiss).
- Zygomaticus major and minor: Raises corner of mouth (smile).
- Platysma: Draws angle of mouth downward (pout)
- Nasalis: Flares nose.
Muscles of the Head: Mastication
- Masseter: Elevates and protracts mandible.
- Temporalis: Elevates and retracts mandible.
- Buccinator: Compresses cheeks.
- Medial pterygoid: Elevates mandible, moves mandible side to side.
- Lateral pterygoid: Depresses and protracts mandible (pulls on mandibular condyle), moves mandible side to side.
Muscles of the Neck: Head movement
- Sternocleidomastoid: Rotates the head, flexes and laterally flexes the neck, elevates the sternum (aids in inhalation).
- Splenius capitis: Rotates the head, extends and laterally flexes the neck.
Deep Muscles of the Thorax: Breathing
- Inspiration (inhaling): Diaphragm and external intercostals contract to enlarge the rib cage.
- Expiration (exhaling): Relaxation of inspiratory muscles decreases the size of the rib cage.
Muscles Crossing the Shoulder Joint: Movements of the Arm (Humerus)
-
Rotator cuff muscles: Act as synergists and fixators, originate on the scapula, reinforce the shoulder capsule, prevent dislocation.
- Supraspinatus: Abducts arm
- Infraspinatus: Rotates arm laterally
- Teres minor: Rotates arm laterally
- Subscapularis: Rotates arm medially
- Coracobrachialis and teres major: Synergists (assist).
Muscles Crossing the Shoulder and Elbow Joints: Movements of the Radius and Ulna
- Biceps brachii: Flexes elbow, flexes and abducts the arm, supinates the radioulnar joint.
- Triceps brachii: Extends elbow, extends and adducts the arm.
Muscles of the Forearm: Movements of the Wrist, Hand, and Fingers
- Extrinsic muscles of the hand: Originate outside the hand and insert within it.
- Tendons entering the hand: Held close to the bones by fascial bands (flexor and extensor retinaculum).
-
Anterior compartment (Flexors)
- Flexor carpi radialis: Flexes and abducts wrist
- Flexor carpi ulnaris: Flexes and adducts wrist
- Flexor digitorum superficialis: Flexes fingers (digits 2-5) and wrist
- Flexor digitorum profundus: Flexes distal finger joints
-
Posterior compartment (Extensors)
- Extensor carpi radialis longus: Extends and abducts wrist
- Extensor carpi ulnaris: Extends and adducts wrist
- Extensor digitorum: Extends fingers.
Muscles of the Neck and Vertebral Column That Move the Head and Trunk
-
Extensors:
- Erector spinae muscles: Extend spine and influence flexion, lateral flexion, rotation (iliocostalis, longissimus, spinalis)
- Splenius muscles: Extend cervical spine, laterally flex cervical spine, rotate head.
Muscles Crossing the Hip and Knee Joints: Movements of the Thigh
-
Thigh flexors: Pass in front of the hip joint
- Iliopsoas (iliacus and psoas major): Flex thigh
- Gluteus maximus: Extends thigh
- Gluteus medius: Abducts and rotates thigh medially
- Tensor fasciae latae: Abducts, flexes, and rotates thigh medially.
-
Adductors (also medially rotate thigh): Used in movements that press thighs together.
- Adductor magnus: Adducts thigh, extends and flexes thigh
- Adductor longus: Adducts, flexes, and rotates thigh laterally
- Adductor brevis: Adducts, flexes, and rotates thigh laterally
- Gracilis: Adducts thigh, flexes knee.
Muscles Crossing the Hip and Knee Joints: Movements of the Leg
-
Quadriceps group (anterior thigh muscles): All insert on or near the quadriceps tendon.
- Rectus femoris: Extends knee, flexes thigh
- Vastus lateralis, vastus medialis, and vastus intermedius: Extend knee
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Description
Test your understanding of levers and their mechanical advantage with this quiz. Explore different classes of levers and how their setup affects load movement and efficiency. Learn about first, second, and third-class levers through examples and applications.
