Muscle Actions and Functions
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Questions and Answers

A muscle that spans two joints is assisted by synergistic muscles in what capacity?

  • By adding extra force and modifying the direction or reducing undesirable movement. (correct)
  • By opposing the primary movement, ensuring smooth action.
  • By stabilizing the bone to which the agonist is attached, allowing for more effective movement.
  • By acting as the primary mover while the main muscle crosses the second joint.

During a bicep curl, the biceps brachii acts as the agonist. What role does the triceps brachii play in this movement, and why is this role important?

  • An antagonist, opposing the biceps action to control the speed and prevent overextension. (correct)
  • A fixator, stabilizing the shoulder joint to provide a stable base for the biceps action.
  • A synergist, assisting the biceps in flexing the forearm for increased power.
  • An agonist, working with the biceps to maximize the force generated during the curl.

Which architectural arrangement of skeletal muscle fascicles maximizes force production, particularly important in muscles requiring high power output?

  • Convergent, since the broad attachment allows for versatile movement.
  • Fusiform, because the spindle shape concentrates force at the belly.
  • Parallel, as the fascicles run along the long axis, allowing for maximum shortening.
  • Pennate, due to the feather-like arrangement that packs more fascicles into a smaller area. (correct)

A muscle with a broad attachment converging to a single tendon allows for versatile movement. Which muscle architecture is best described here?

<p>Convergent (D)</p> Signup and view all the answers

The point of muscle attachment to the more stationary bone is known as the origin. How does understanding the origin and insertion points aid in predicting a muscle's action?

<p>It reveals the direction of muscle contraction and the resultant movement at the joint. (B)</p> Signup and view all the answers

Damage to the genioglossus muscle would most significantly impair which function?

<p>Movement of the tongue, affecting speech and swallowing. (C)</p> Signup and view all the answers

Which of the following scenarios would be most directly affected by dysfunction of the intrinsic muscles of the tongue?

<p>Changing the shape of the tongue during speech. (D)</p> Signup and view all the answers

A patient presents with difficulty flexing their neck and drawing their head to the right. Which muscle is most likely affected?

<p>Sternocleidomastoid on the right side. (C)</p> Signup and view all the answers

Following a whiplash injury, a patient experiences difficulty with lateral flexion of the neck. Which group of muscles is most likely to be involved?

<p>Scalene muscles. (C)</p> Signup and view all the answers

What would be the most likely result of bilateral damage to the sternocleidomastoid muscles?

<p>Difficulty in flexing the neck. (C)</p> Signup and view all the answers

Which of the following muscles plays a crucial role in depressing the hyoid bone after it has been elevated during swallowing?

<p>Omohyoid. (D)</p> Signup and view all the answers

A person has suffered trauma that impairs their ability to maintain posture and move their vertebral column. Which group of muscles has most likely been affected?

<p>Intrinsic muscles of the back. (C)</p> Signup and view all the answers

Damage to which of the following muscles would most directly affect the raising of the hyoid bone during swallowing?

<p>Mylohyoid. (A)</p> Signup and view all the answers

Damage to the multifidus muscle would MOST directly impact which region of the vertebral column?

<p>Lumbar (D)</p> Signup and view all the answers

If a patient is experiencing difficulty with lateral flexion and rotation of the vertebral column, which group of abdominal muscles is MOST likely affected?

<p>A combination of flat and vertical abdominal muscles (B)</p> Signup and view all the answers

A surgeon is performing a procedure that requires accessing the space between the external and innermost intercostal muscles. Which of the following structures will the surgeon encounter?

<p>Internal intercostal muscles (C)</p> Signup and view all the answers

During a deep exhalation, which action is LEAST likely to occur due to the contraction of abdominal muscles?

<p>Increase in thoracic cavity volume (B)</p> Signup and view all the answers

A patient reports experiencing pain along the lateral aspect of their spine. Which of the Erector Spinae muscle groups is MOST likely involved?

<p>Iliocostalis (lateral column) (D)</p> Signup and view all the answers

Which of the following muscles assists in rotating the vertebral column to the OPPOSITE side?

<p>External oblique (D)</p> Signup and view all the answers

During inspiration, which of the following events does NOT directly contribute to increasing the volume of the thoracic cavity?

<p>Relaxation of the diaphragm (D)</p> Signup and view all the answers

A stab wound penetrates through the anterior abdominal wall, passing through three layers of flat muscles. In what order would the instrument pass through these muscles from superficial to deep?

<p>External oblique, internal oblique, transverse abdominis (A)</p> Signup and view all the answers

Which characteristic is LEAST likely to be associated with cardiac muscle tissue?

<p>Voluntary control enables conscious regulation of heart rate. (B)</p> Signup and view all the answers

How does smooth muscle contraction differ fundamentally from skeletal muscle contraction regarding initiation?

<p>Smooth muscle can contract spontaneously without external stimulation, whereas skeletal muscle requires a stimulus. (B)</p> Signup and view all the answers

Why is the arrangement of myofilaments within myofibrils significant in skeletal muscle tissue?

<p>It produces the striated appearance characteristic of skeletal muscle. (A)</p> Signup and view all the answers

What is the functional consequence of the epimysium's direct continuity with the periosteum in muscles exhibiting direct attachment?

<p>It directly transmits contractile forces from the muscle to the bone. (D)</p> Signup and view all the answers

How does the structural arrangement of connective tissues (endomysium, perimysium, epimysium) contribute to the overall function of skeletal muscle?

<p>It compartmentalizes muscle fibers, distributes forces, and provides structural integrity. (C)</p> Signup and view all the answers

Why might a muscle with an indirect attachment (via a tendon) be advantageous compared to a direct attachment in certain anatomical locations?

<p>Indirect attachments can focus the force of muscle contraction onto a smaller area of bone. (B)</p> Signup and view all the answers

Which structural feature is MOST responsible for the ability of cardiac muscle to function as a coordinated syncytium?

<p>Presence of gap junctions within intercalated discs. (B)</p> Signup and view all the answers

Given its function in the walls of blood vessels, what adaptation is MOST crucial for smooth muscle to maintain vascular tone over extended periods?

<p>Resistance to fatigue. (B)</p> Signup and view all the answers

Which structural component facilitates the quadriceps' ability to extend the leg at the knee joint?

<p>The patellar ligament. (C)</p> Signup and view all the answers

During activities such as climbing and running, what is the integrated action of the quadriceps femoris that enables these movements?

<p>Simultaneous flexion of the hip and extension of the knee. (C)</p> Signup and view all the answers

Damage to the ischial tuberosity would directly affect the function of which muscle group?

<p>Hamstring muscles. (C)</p> Signup and view all the answers

What is the functional consequence of the unique, straight-down orientation of the deep fibers within the rectus femoris?

<p>Effective force transmission for hip flexion and knee extension. (C)</p> Signup and view all the answers

If a patient has difficulty adducting their thigh, which of the following muscles is LEAST likely to be involved?

<p>Gluteus minimus. (C)</p> Signup and view all the answers

Which muscle is primarily responsible for resisting increases in intra-abdominal pressure and supporting pelvic viscera?

<p>Coccygeus (B)</p> Signup and view all the answers

A patient experiences a compromised ability to control urination. Dysfunction in which muscle of the urogenital diaphragm is the MOST likely cause?

<p>External urethral sphincter (B)</p> Signup and view all the answers

Following a perineal injury, a male patient reports difficulty achieving and maintaining an erection. Which muscle, when damaged, MOST likely contributes to this condition?

<p>Ischiocavernosus (A)</p> Signup and view all the answers

A surgeon is performing a complex pelvic reconstruction. To minimize damage, understanding the anatomical layers is critical. What is the correct order of the pelvic floor compartments from deepest to superficial?

<p>Pelvic diaphragm, urogenital diaphragm, superficial perineal space (D)</p> Signup and view all the answers

Damage to the levator ani muscle group is MOST likely to result in which of the following?

<p>All of the above (D)</p> Signup and view all the answers

Which statement accurately describes the anatomical location of the perineum in relation to the pelvic diaphragm?

<p>The perineum is inferior to the pelvic diaphragm. (C)</p> Signup and view all the answers

Which BEST describes the combined function of the pubococcygeus and iliococcygeus muscles?

<p>Support pelvic viscera, resist intra-abdominal pressure, and form anal/vaginal sphincters (D)</p> Signup and view all the answers

A patient reports pain along the ischial spine radiating to the coccyx. Palpation reveals tightness in the affected area. Which muscle is MOST likely involved?

<p>Coccygeus (A)</p> Signup and view all the answers

Flashcards

Muscle Origin

The end of a muscle attached to the less movable bone.

Muscle Insertion

The end of a muscle attached to the most movable bone.

Muscle Belly

The thicker middle region between the origin and insertion of a muscle.

Agonist Muscle

The primary mover that produces the most force during a joint action.

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Antagonist Muscle

A muscle that opposes agonistic movement or prevents overshooting.

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Cardiac Muscle

Type of muscle with short fibres, striated, single nucleus, branched, high aerobic capacity.

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Smooth Muscle

Muscle found in internal organs, unstriated, spindle-shaped, involuntary control, does not tire.

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Skeletal Muscle

Voluntary muscle, attached to bones, long cylindrical cells, has multiple nuclei, striated appearance.

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Myofibrils

Structures in muscle cells made of sarcomeres containing actin and myosin filaments; appear striped.

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Endomysium

Loose connective tissue surrounding each muscle fibre, contains capillaries for blood supply.

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Perimysium

Connective tissue that surrounds bundles of muscle fibres (fasciculae).

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Epimysium

Dense connective tissue that surrounds the entire muscle, binding multiple fasciculae.

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Voluntary Control

Type of control of skeletal muscles, enabling conscious movement, unlike smooth muscles.

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Extrinsic tongue muscles

Muscles that move the tongue during actions like speaking and chewing.

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Intrinsic tongue muscles

Muscles that alter the shape of the tongue for articulation and manipulation of food.

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Genioglossus

A muscle that helps protrude the tongue and depress its center.

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Suprahyoid muscles

Muscles located above the hyoid bone that help raise it during swallowing.

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Infrahyoid muscles

Muscles located below the hyoid bone that return it to its resting position post-swallowing.

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Sternocleidomastoid (SCM)

A muscle that flexes the neck and rotates the head.

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Extrinsic back muscles

Superficial muscles that control limb movement and stabilize the back.

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Intrinsic back muscles

Deep muscles that act on the vertebral column to maintain posture and facilitate movement.

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Quadriceps Femoris

A large muscle group on the front of the thigh composed of four parts that extend the knee and flex the hip.

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Conjoined tendon

The structure formed by the union of quadriceps muscles' tendons that attaches to the patella.

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Patellar ligament

The continuation of the quadriceps tendon that connects the patella to the tibia's tuberosity.

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Hamstring muscles

A group of three muscles located at the back of the thigh responsible for knee flexion and hip extension.

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Medial compartment muscles

Muscles situated on the inside of the thigh that are responsible for adducting the leg.

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Splenius Capitis

A muscle of the superficial group that extends the head and neck.

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Splenius Cervicis

A muscle of the superficial group that acts on the neck, specifically the cervical area.

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Iliocostalis

Lateral column of the Intermediate (Erector Spinae) group of muscles in the back.

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Longissimus

Intermediate column muscle of the Erector Spinae group that extends the back.

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Semispinalis

A muscle of the Deep (Transversospinal) group involved in rotating and extending the vertebral column.

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Diaphragm

A dome-shaped muscle that separates thoracic and abdominal cavities, crucial for respiration.

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External Intercostals

Muscles between the ribs that aid in inhalation by raising the ribs.

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Rectus Abdominis

Vertical muscle of the abdomen known as the 'six-pack', involved in flexing the spine.

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Pelvic Floor Muscles

Muscles that support pelvic viscera and resist intra-abdominal pressure.

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Pelvic Diaphragm

The deepest layer of the pelvic floor, consisting of levator ani and coccygeus muscles.

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Levator Ani

A muscle group in the pelvic diaphragm that supports pelvic organs.

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Coccygeus

Muscle that supports the pelvic floor and connects to the coccyx.

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Urogenital Diaphragm

Middle layer of pelvic floor muscles, includes the external urethral and anal sphincters.

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Superficial Perineal Space

Top layer of pelvic floor muscles, lies beneath the skin.

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Ischiocavernosus

Muscle in the superficial perineal space that aids in erection.

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Perineum

Diamond-shaped area between the thighs that houses pelvic structures.

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Study Notes

Anatomy of the Muscular System

  • The muscular system is composed of cells that contract to cause movement.
  • Muscles produce movement, allow breathing, transport materials, and circulate blood.
  • Muscles maintain posture and body position by resisting gravity and preventing unwanted movements.
  • They hold some articulating bones in place by maintaining tension on the tendons.
  • Ring-like sphincter muscles control the admission of light, food, and drink.
  • Urethral and anal orifices control waste elimination; other sphincters control the movement of food, bile, and other materials through the body.
  • Skeletal muscles produce approximately 85% of body heat, essential for enzyme function and metabolism
  • Three types of muscle tissue exist:
    • Cardiac muscle: Forms the heart wall; involuntary.
    • Smooth muscle: Found in structures like blood vessels, stomach, and intestines; involuntary.
    • Skeletal muscle: Attached to skeletons; voluntary.

Muscle Structure

  • Skeletal muscle is made up of individual muscle fibers (cells).
  • Muscle fibers contain multiple nuclei near the surface of the cell.
  • Two types of myofilaments (actin and myosin) are organized in units called sarcomeres within myofibrils.
  • The arrangement of myofilaments within myofibrils causes the striated appearance of skeletal muscle.

Connective Tissues in Skeletal Muscle

  • Endomysium: A loose connective tissue surrounding individual muscle fibers.
  • Fascicles: Bundles of muscle fibers grouped together by endomysium.
  • Perimysium: A strong connective tissue surrounding fascicles.
  • Epimysium: A dense connective tissue surrounding the entire muscle.
  • Tendons: Connective tissue that attaches muscles to bones.
  • These connective tissue components support and organize the muscle fibers and help transfer forces generated by muscle contractions to the skeletal system.

Attachment of Skeletal Muscles to Bone

  • Direct attachment: Epimysium of muscle fibers directly merges with the periosteum of the bone

  • Indirect attachment: Muscles attach to bones via tendons.

  • Indirect attachments often leave bony markings which include tubercles, crests, or ridges on bone.

Shape and Architecture of Skeletal Muscles

  • Pennate: Feather-like arrangement of fascicles (e.g., deltoid muscle)
  • Fusiform: Spindle-shaped (e.g., biceps brachii)
  • Parallel: Fascicles lie parallel to the long axis of the muscle.
  • Convergent: Fascicles converge to a single tendon from a broad attachment point.
  • Circular: Surround body openings or orifices.

Muscle Groups in Action

  • Agonists: Primary movers during a joint action.
  • Synergists: Assist agonists.
  • Antagonists: Oppose the action of agonists.
  • Fixators: Stabilize the bone.

Blood and Nerve Supply

  • Blood vessels: Provide nutrients and oxygen for contraction; Each muscle fiber is in contact with one or more capillaries
  • Motor neurons: Convey impulses for muscular contraction; Each motor axon branches to innervate a number of muscle fibers at a neuromuscular junction.

Naming of Skeletal Muscles

  • Named based on location, shape, size, direction of fascicles, location of attachment, number of origins, and action.

Classification of Skeletal Muscles

  • Axial muscles: Attached to the axial skeleton (head, neck, trunk).
  • Appendicular muscles: Attached to the appendicular skeleton (limbs).

Muscles of Facial Expression

  • Originate on skull bones or fascia.
  • Insert into the skin of the face.
  • Movements of these muscles create facial expressions.

Muscles that Move the Eyeball (Extrinsic Eye Muscles)

  • Six pairs of muscles that control precise eye movements.

Muscles of Mastication (Chewing)

  • Strong muscles responsible for opening and closing the jaw.

  • Masseter, Temporalis medial and lateral pterygoids, are the main muscles.

Muscles of the Tongue

  • Responsible for swallowing, speech, and mastication.

Muscles of the Neck

  • Lateral cervical muscles: Support and move the head and/or neck.
  • Sternocleidomastoid, splenius, scalenes are the most important.

Muscles of the Trunk

  • Support and protect viscera, help in respiration and other movements.

Muscles of the Abdomen

  • Five muscles maintain abdominal posture and support viscera.

Muscles of the Pelvis (Pelvic Floor Muscles)

  • Pelvic diaphragm, Urogenital diaphragm, and superficial perineal space are the main muscles for supporting the pelvic viscera and urinary bladder/rectum.
  • They assist in different bodily functions

Muscles of the Upper Limb

  • Stabilize the pelvic and pectoral girdle and moves the upper and lower limbs
  • Muscles of pectoral girdles, upper limb, and pelvic girdles, lower limb.
  • Muscles of the upper limb involve shoulder movements.

Muscles of the Lower Limb

  • Support and move the lower limbs, with particular emphasis on locomotion and posture and stability.
  • Hip, femurs, knee, and foot are the main parts to support these movements

Muscles of the Thorax/Respiration

  • The primary muscles include the external intercostals, internal intercostals, and innermost intercostals. These aid in breathing.

  • The diaphragm separates the thoracic and abdominal cavities

  • Diaphragm is also important from the standpoint of respiration, urination, defecation, vomiting, and childbirth. It also plays a vital role in protecting and supporting the viscera in these situations.

Muscles of the Back

  • These muscles act on the vertebral column and produce posture and maintain various movements.

Muscles of the Wrist, Hand, and Fingers

  • These muscles are responsible for wrist, hand, and finger movements for different functions.
  • Forearm flexors and extensors aid in hand movements.

Intrinsic Muscles of the Hand

  • Located in the hand itself; They control finer movements within the wrist, fingers, and thumb

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Anatomy of MUSCULAR SYSTEM PDF

Description

Explore muscle actions, joint assistance by synergistic muscles, and the roles of agonist/antagonist pairs like biceps and triceps. Understand muscle architecture for force production and muscle attachments on bone. Consider the impact of muscle damage on genioglossus or intrinsic ones.

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