Chapter 11: The Muscular System Flashcards
What are the main contributions of the muscular system to homeostasis?
The muscular system stabilizes body position, produces movement, regulates organ volume, moves substances within the body, and generates heat.
What is the general function of most skeletal muscles?
Most skeletal muscles produce movement by exerting force on tendons, which pull on bones or other structures.
What are the attachment sites of a skeletal muscle called?
The attachment sites are called the origin (stationary bone) and the insertion (movable bone).
What is the term for the fleshy portion of a muscle between its tendons?
The fleshy portion is called the belly or body of the muscle.
What is reverse muscle action (RMA)?
Reverse muscle action occurs when the origin and insertion of a muscle switch during specific movements, reversing the muscle’s action.
What are the components of a lever system in the context of muscle movement?
In a lever system, bones act as levers, joints serve as fulcrums, and muscles provide the effort to move the load.
What are the types of levers and their characteristics?
- First-class levers: Fulcrum between effort and load (e.g., head on the spine). 2. Second-class levers: Load between fulcrum and effort (e.g., standing on toes). 3. Third-class levers: Effort between fulcrum and load (e.g., forearm flexion).
What is the difference between mechanical advantage and mechanical disadvantage in levers?
- Mechanical Advantage: Less effort is needed to move a heavy load over a short distance.
- Mechanical Disadvantage: More effort is needed to move a lighter load, but it moves faster.
How are muscle fibers arranged in different muscle types?
- Parallel: Fibers run parallel to the muscle’s length.
- Fusiform: Fibers run parallel but narrow at the ends.
- Circular: Fibers form sphincter muscles.
- Triangular: Fibers spread out and converge at a central tendon.
- Pennate: Fibers attach at an angle to the tendon (unipennate, bipennate, multipennate).
How does muscle fascicle arrangement affect muscle function?
The arrangement impacts the muscle’s power and range of motion (ROM). Pennate muscles are stronger but less flexible, while parallel muscles have more ROM but less strength.
What roles do muscles play in coordination during movement?
Muscles work in pairs: one muscle (the prime mover) contracts to produce movement, while the opposing muscle (the antagonist) stretches. Synergists assist, and fixators stabilize the origin of the prime mover.
What are the different types of muscles based on their role in movement?
- Prime Mover (Agonist): The main muscle producing movement. - Antagonist: The muscle that opposes the prime mover. - Synergist: Assists the prime mover in its action. - Fixator: Stabilizes the origin of the prime mover.
How are muscles grouped in muscle compartments?
Muscle compartments are groups of muscles, blood vessels, and nerves that share a common function. In the upper limbs, flexor muscles are on the front, and extensor muscles are on the back.
What does the frontal belly of the occipitofrontalis muscle do?
The frontal belly draws the scalp anteriorly, raises the eyebrows, and wrinkles the skin of the forehead horizontally, often creating a look of surprise.
What action does the zygomaticus major muscle facilitate?
The zygomaticus major draws the angle of the mouth superiorly and laterally, helping create a smiling expression.
What is the function of the orbicularis oris muscle?
The orbicularis oris is a circular muscle that closes and protrudes the lips, shapes lips during speech, and compresses them against the teeth (e.g., kissing).
What actions does the buccinator muscle assist with?
The buccinator presses the cheeks against the teeth and lips, helps with whistling, blowing, sucking, and keeps food between the teeth during mastication.
What does the orbicularis oculi muscle do?
The orbicularis oculi is a circular muscle that closes the eye.
What are the extrinsic eye muscles responsible for?
The extrinsic eye muscles control the movement of the eyeballs and upper eyelid and are known for their fast contractions and precise control.
What are the muscles that move the mandible and assist in mastication?
These muscles are known as muscles of mastication. They include the masseter, temporalis, medial pterygoid, and lateral pterygoid, which control movements of the jaw for chewing and speaking.
What is the function of the masseter muscle?
The masseter elevates the mandible (closes the mouth). It is the strongest muscle responsible for chewing.
What is the function of the temporalis muscle?
The temporalis elevates and retracts the mandible (pulls the jaw backward).
What action do the medial and lateral pterygoid muscles assist with?
The medial and lateral pterygoid muscles help move the jaw side to side for grinding food. The lateral pterygoid also moves the jaw forward.
What is the function of the suprahyoid muscles?
The suprahyoid muscles elevate the hyoid bone, the floor of the oral cavity, and the tongue during swallowing, aiding in deglutition (swallowing) and speech.
What is the origin and action of the sternocleidomastoid muscle?
The sternocleidomastoid originates at the manubrium of the sternum (sternal head) and the medial third of the clavicle (clavicular head), and inserts at the mastoid process of the temporal bone and lateral half of the superior nuchal line of the occipital bone. It flexes the cervical vertebral column and extends the head at the atlanto-occipital joint.
What does the sternocleidomastoid muscle do when it contracts unilaterally?
Unilaterally, the sternocleidomastoid laterally flexes the neck and head to the same side and rotates the head to the opposite side. Posterior fibers also assist in head extension.
What is the action of the rectus abdominis?
The rectus abdominis flexes the vertebral column and compresses the abdomen for actions like defecation, urination, forced exhalation, and childbirth. It also flexes the pelvis on the vertebral column.
What is the origin and action of the external abdominal oblique?
The external abdominal oblique originates from the lower ribs and inserts at the iliac crest and linea alba. It bilaterally compresses the abdomen and flexes the vertebral column; unilaterally, it laterally flexes and rotates the vertebral column.
What does the internal abdominal oblique muscle do?
The internal abdominal oblique also compresses the abdomen and flexes the vertebral column bilaterally. Unilaterally, it laterally flexes and rotates the vertebral column.
What is the function of the transversus abdominis?
The transversus abdominis compresses the abdomen.
What do the aponeuroses of the external oblique, internal oblique, and transversus abdominis form?
These muscles form the rectus sheaths, which enclose the rectus abdominis. The sheaths meet at the midline to form the linea alba, which stretches during pregnancy.
What is the primary muscle for breathing?
The diaphragm is the primary muscle for breathing. It separates the thoracic cavity from the abdominal cavity and helps control the size of the thoracic cavity for inhalation and exhalation.
What happens when the diaphragm contracts?
Contraction of the diaphragm causes it to depress, increasing the vertical dimension of the thoracic cavity, resulting in inhalation.
What is the action of the external intercostals?
The external intercostals elevate the ribs during inhalation, increasing the anteroposterior and lateral dimensions of the thoracic cavity. When they relax, they depress the ribs during exhalation.
What is the function of the internal intercostals?
The internal intercostals draw adjacent ribs together during forced exhalation, decreasing the anteroposterior and lateral dimensions of the thoracic cavity.
What is the function of the muscles of the pelvic floor?
The pelvic floor muscles support the pelvic viscera, resist intra-abdominal pressure, and function as sphincters. They also assist in urination and play a role in ejaculation.
What is the action of the Pectoralis minor?
Abducts scapula and rotates it downward. RMA: Elevates ribs 3–5 in forced inhalation when scapula is fixed.
What is the origin and insertion of the Serratus anterior?
Origin: Ribs 1-8 or 9. Insertion: Vertebral border and inferior angle of scapula.
