Homework 1: Motility
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Questions and Answers

The medial nuclei of CN III innervates which of the following?

  • Superior Rectus (correct)
  • Medial Rectus
  • Inferior Rectus
  • Inferior Oblique

    • What does the size principle in the process of activation of skeletal muscles state?

  • The muscles controlled by the smallest, most highly excitable motor neurons are recruited first.
  • The motor units with the smallest muscle fibers are activated first because they are controlled by the smallest, and least excitable motor neurons.
  • The motor units with the smallest muscle fibers are activated first because they are controlled by the smallest, most highly excitable motor neurons. (correct)
  • The motor units with the largest muscle fibers are activated first because they are controlled by the largest, most highly excitable motor neurons.

    • Which of the following is not used for gaze holding?

  • Slow vergence (correct)
  • Pursuit
  • Optokinetic reflex
  • Saccades
  • Vestibulo-Ocular reflex

    • What is the time response of extraocular muscles?

    <p>Shorter than most of the other muscle groups in the human body</p> Signup and view all the answers

    A patient with a left orbital fracture blocking the superior division of CN III will:

    <p>Elevate their chin, tend to tilt the head to the right, and rotate their neck towards the right</p> Signup and view all the answers

    What surrounds a muscle fiber?

    <p>Endomysium</p> Signup and view all the answers

    What is a Duction?

    <p>A movement of one eye</p> Signup and view all the answers

    Which of the following muscles have contralateral innervation?

    <p>Inferior Oblique</p> Signup and view all the answers

    Which statement about saccades is true?

    <p>Visually driven eye movement that stabilizes the retinal image during large-field motion</p> Signup and view all the answers

    Which ocular muscle is innervated by the trochlear nerve?

    <p>Superior Oblique</p> Signup and view all the answers

    What is the primary benefit of the size principle in motor unit recruitment?

    <p>Optimizes the recruitment of tension</p> Signup and view all the answers

    Which of the following reflexes is responsible for gaze holding during head rotations?

    <p>Vestibulo-Ocular reflex</p> Signup and view all the answers

    What is a characteristic time response of extraocular muscles?

    <p>Lack of a relaxation period</p> Signup and view all the answers

    Which nucleus of CN III innervates the superior rectus muscle?

    <p>Medial nucleus</p> Signup and view all the answers

    What is the primary function of the slow vergence system?

    <p>Disconjugate gaze shifts during binocular viewing</p> Signup and view all the answers

    Which of the following statements is true about motor unit recruitment?

    <p>The size principle optimizes motor unit recruitment</p> Signup and view all the answers

    What is the primary purpose of the optokinetic reflex?

    <p>Stabilizing gaze during large field motion</p> Signup and view all the answers

    What would be the likely movement of the head and neck in a patient with a right orbital fracture that is blocking the inferior division of CN III?

    <p>Move their chin down, tend to tilt the head to the left, and rotate their neck towards the right</p> Signup and view all the answers

    Which of the following muscle groups has the longest contraction period?

    <p>Extraocular muscles</p> Signup and view all the answers

    What surrounds a group of muscle fibers?

    <p>Perimysium</p> Signup and view all the answers

    Which of the following eye movements is NOT visually driven?

    <p>Vestibulo-ocular reflex</p> Signup and view all the answers

    Which of the following muscles has ipsilateral innervation?

    <p>Medial Rectus</p> Signup and view all the answers

    What is the primary function of saccades?

    <p>To shift gaze between fixation points</p> Signup and view all the answers

    Which of the following statements about saccades is FALSE?

    <p>Saccades are mediated by the semicircular canals</p> Signup and view all the answers

    What is the term for the movement of one eye?

    <p>Duction</p> Signup and view all the answers

    Which of the following muscles is NOT innervated by the medial nuclei of CN III?

    <p>Lateral Rectus</p> Signup and view all the answers

    What is the primary mechanism underlying the size principle in motor unit recruitment?

    <p>The smallest motor neurons have the lowest threshold for activation</p> Signup and view all the answers

    Which of the following reflexes is responsible for gaze holding during rotations of the head?

    <p>Vestibulo-Ocular reflex</p> Signup and view all the answers

    What is the characteristic time response of extraocular muscles?

    <p>Fast and brief, with a rapid relaxation period</p> Signup and view all the answers

    Which of the following statements about motor unit recruitment is FALSE?

    <p>Motor units with larger muscle fibers are recruited first</p> Signup and view all the answers

    Which of the following eye movements is visually driven?

    <p>Pursuit system</p> Signup and view all the answers

    What is the primary function of the slow vergence system?

    <p>To converge or diverge the eyes</p> Signup and view all the answers

    What is the characteristic of muscle groups that lack a contraction period?

    <p>They are longer than most of the other muscle groups in the human body</p> Signup and view all the answers

    A patient with a right orbital fracture that is blocking the inferior division of CN III will:

    <p>Move their chin down, tend to tilt the head to the right, and rotate their neck towards the left</p> Signup and view all the answers

    Which of the following is NOT a type of muscle tissue?

    <p>Sarcolemma</p> Signup and view all the answers

    What is the main function of conjugate movements of the eyes?

    <p>To move both eyes in the same direction</p> Signup and view all the answers

    Which muscle has contralateral innervation?

    <p>Superior Rectus</p> Signup and view all the answers

    What is the approximate speed of saccades?

    <p>800 deg/sec</p> Signup and view all the answers

    What is the primary function of the Medial Rectus muscle?

    <p>To adduct the eye</p> Signup and view all the answers

    Which of the following muscles is NOT responsible for eye movement?

    <p>Soleus</p> Signup and view all the answers

    Which of the following muscles is innervated by the trochlear nerve?

    <p>Inferior Oblique</p> Signup and view all the answers

    What is the primary benefit of the size principle in motor unit recruitment?

    <p>It optimizes the recruitment of tension</p> Signup and view all the answers

    Which of the following is responsible for gaze holding during rotations of the head?

    <p>Vestibulo-Ocular reflex</p> Signup and view all the answers

    What is the characteristic time response of extraocular muscles?

    <p>Shorter than most other muscle groups</p> Signup and view all the answers

    Which of the following statements about motor unit recruitment is true?

    <p>Smaller motor units are recruited first</p> Signup and view all the answers

    What is the primary mechanism underlying the movement of a patient with a left orbital fracture that is blocking the superior division of CN III?

    <p>Innervation of the superior rectus muscle</p> Signup and view all the answers

    Which muscle group lacks a contraction period?

    <p>None of the above</p> Signup and view all the answers

    What is the primary function of the slow vergence system?

    <p>None of the above</p> Signup and view all the answers

    Which of the following muscles is innervated by the trochlear nerve?

    <p>Superior oblique muscle</p> Signup and view all the answers

    What is the characteristic time response of extraocular muscles?

    <p>Rapid contraction and rapid relaxation</p> Signup and view all the answers

    What is the primary function of the motor units with the smallest muscle fibers?

    <p>To optimize the recruitment of tension</p> Signup and view all the answers

    Which of the following reflexes is responsible for gaze holding during head rotations?

    <p>Vestibulo-ocular reflex</p> Signup and view all the answers

    What is the characteristic time response of extraocular muscles?

    <p>Shorter than most other muscle groups in the human body</p> Signup and view all the answers

    Which of the following muscles is innervated by the trochlear nerve?

    <p>Superior Oblique</p> Signup and view all the answers

    What is the primary benefit of the size principle in motor unit recruitment?

    <p>To optimize the recruitment of tension</p> Signup and view all the answers

    Which of the following is not used for gaze holding?

    <p>Saccades</p> Signup and view all the answers

    Which of the following muscles has contralateral innervation?

    <p>Lateral Rectus</p> Signup and view all the answers

    What is the primary function of the slow vergence system?

    <p>To facilitate gaze holding during head rotations</p> Signup and view all the answers

    Which of the following nuclei of CN III innervates the inferior rectus muscle?

    <p>Medial nuclei</p> Signup and view all the answers

    What is the primary mechanism underlying the size principle in motor unit recruitment?

    <p>The motor units with the smallest muscle fibers are recruited first</p> Signup and view all the answers

    Which muscle group has the longest contraction period in the human body?

    <p>Core muscles</p> Signup and view all the answers

    A patient with a right orbital fracture that is blocking the inferior division of CN III will:

    <p>Elevate their chin, tend to tilt the head to the right, and rotate their neck towards the right</p> Signup and view all the answers

    What is the primary function of conjugate movements of the eyes?

    <p>To track a moving object</p> Signup and view all the answers

    Which muscle has ipsilateral innervation?

    <p>Lateral Rectus</p> Signup and view all the answers

    What is the primary mechanism underlying the size principle in motor unit recruitment?

    <p>The smallest motor units are recruited first</p> Signup and view all the answers

    Which of the following eye movements is NOT visually driven?

    <p>Vestibular-ocular reflex</p> Signup and view all the answers

    What is the primary function of the slow vergence system?

    <p>To focus on a single point</p> Signup and view all the answers

    Which muscle group lacks a contraction period?

    <p>Extraocular muscles</p> Signup and view all the answers

    What is the primary benefit of the size principle in motor unit recruitment?

    <p>Increased precision</p> Signup and view all the answers

    What is the characteristic time response of extraocular muscles?

    <p>Fast twitch, short duration</p> Signup and view all the answers

    Study Notes

    Oculomotor Nerve (CN III)

    • Medial nuclei of CN III innervate the medial rectus muscle.
    • Inferior oblique muscle is innervated by the trochlear nerve (CN IV).

    Size Principle in Skeletal Muscle Activation

    • The size principle states that motor units with the smallest muscle fibers are activated first because they are controlled by the smallest, most highly excitable motor neurons.
    • This principle optimizes the recruitment of tension in skeletal muscles.

    Gaze Holding

    • Gaze holding is achieved through slow vergence, optokinetic reflex, vestibulo-ocular reflex, and pursuit.
    • Saccades are not used for gaze holding, but rather for shifting gaze.

    Extraocular Muscles

    • The time response of extraocular muscles is shorter than most other muscle groups in the human body, with a response time of around 0.2 seconds.
    • Extraocular muscles lack a relaxation period.

    Effects of CN III Damage

    • A patient with a left orbital fracture that blocks the superior division of CN III will elevate their chin, tend to tilt the head to the right, and rotate their neck towards the left.

    Muscle Fiber Anatomy

    • A muscle fiber is surrounded by endomysium.

    Eye Movements

    • A duction is a movement of one eye.
    • Conjugate movements involve the simultaneous movement of both eyes in the same direction.

    Innervation of Extraocular Muscles

    • The superior rectus muscle has contralateral innervation.
    • The lateral rectus muscle has ipsilateral innervation.

    Saccades

    • Saccades are rapid eye movements that can reach speeds of up to 800 deg/sec.
    • They have a latency of around 90 deg/sec and are visually driven to stabilize the retinal image during large-field motion.

    Oculomotor Nerve (CN III)

    • Medial nuclei of CN III innervate the medial rectus muscle.
    • Inferior oblique muscle is innervated by the trochlear nerve (CN IV).

    Size Principle in Skeletal Muscle Activation

    • The size principle states that motor units with the smallest muscle fibers are activated first because they are controlled by the smallest, most highly excitable motor neurons.
    • This principle optimizes the recruitment of tension in skeletal muscles.

    Gaze Holding

    • Gaze holding is achieved through slow vergence, optokinetic reflex, vestibulo-ocular reflex, and pursuit.
    • Saccades are not used for gaze holding, but rather for shifting gaze.

    Extraocular Muscles

    • The time response of extraocular muscles is shorter than most other muscle groups in the human body, with a response time of around 0.2 seconds.
    • Extraocular muscles lack a relaxation period.

    Effects of CN III Damage

    • A patient with a left orbital fracture that blocks the superior division of CN III will elevate their chin, tend to tilt the head to the right, and rotate their neck towards the left.

    Muscle Fiber Anatomy

    • A muscle fiber is surrounded by endomysium.

    Eye Movements

    • A duction is a movement of one eye.
    • Conjugate movements involve the simultaneous movement of both eyes in the same direction.

    Innervation of Extraocular Muscles

    • The superior rectus muscle has contralateral innervation.
    • The lateral rectus muscle has ipsilateral innervation.

    Saccades

    • Saccades are rapid eye movements that can reach speeds of up to 800 deg/sec.
    • They have a latency of around 90 deg/sec and are visually driven to stabilize the retinal image during large-field motion.

    Oculomotor Nerve (CN III)

    • Medial nuclei of CN III innervate the medial rectus muscle.
    • Inferior oblique muscle is innervated by the trochlear nerve (CN IV).

    Size Principle in Skeletal Muscle Activation

    • The size principle states that motor units with the smallest muscle fibers are activated first because they are controlled by the smallest, most highly excitable motor neurons.
    • This principle optimizes the recruitment of tension in skeletal muscles.

    Gaze Holding

    • Gaze holding is achieved through slow vergence, optokinetic reflex, vestibulo-ocular reflex, and pursuit.
    • Saccades are not used for gaze holding, but rather for shifting gaze.

    Extraocular Muscles

    • The time response of extraocular muscles is shorter than most other muscle groups in the human body, with a response time of around 0.2 seconds.
    • Extraocular muscles lack a relaxation period.

    Effects of CN III Damage

    • A patient with a left orbital fracture that blocks the superior division of CN III will elevate their chin, tend to tilt the head to the right, and rotate their neck towards the left.

    Muscle Fiber Anatomy

    • A muscle fiber is surrounded by endomysium.

    Eye Movements

    • A duction is a movement of one eye.
    • Conjugate movements involve the simultaneous movement of both eyes in the same direction.

    Innervation of Extraocular Muscles

    • The superior rectus muscle has contralateral innervation.
    • The lateral rectus muscle has ipsilateral innervation.

    Saccades

    • Saccades are rapid eye movements that can reach speeds of up to 800 deg/sec.
    • They have a latency of around 90 deg/sec and are visually driven to stabilize the retinal image during large-field motion.

    Oculomotor Nerve (CN III)

    • Medial nuclei of CN III innervate the medial rectus muscle.
    • Inferior oblique muscle is innervated by the trochlear nerve (CN IV).

    Size Principle in Skeletal Muscle Activation

    • The size principle states that motor units with the smallest muscle fibers are activated first because they are controlled by the smallest, most highly excitable motor neurons.
    • This principle optimizes the recruitment of tension in skeletal muscles.

    Gaze Holding

    • Gaze holding is achieved through slow vergence, optokinetic reflex, vestibulo-ocular reflex, and pursuit.
    • Saccades are not used for gaze holding, but rather for shifting gaze.

    Extraocular Muscles

    • The time response of extraocular muscles is shorter than most other muscle groups in the human body, with a response time of around 0.2 seconds.
    • Extraocular muscles lack a relaxation period.

    Effects of CN III Damage

    • A patient with a left orbital fracture that blocks the superior division of CN III will elevate their chin, tend to tilt the head to the right, and rotate their neck towards the left.

    Muscle Fiber Anatomy

    • A muscle fiber is surrounded by endomysium.

    Eye Movements

    • A duction is a movement of one eye.
    • Conjugate movements involve the simultaneous movement of both eyes in the same direction.

    Innervation of Extraocular Muscles

    • The superior rectus muscle has contralateral innervation.
    • The lateral rectus muscle has ipsilateral innervation.

    Saccades

    • Saccades are rapid eye movements that can reach speeds of up to 800 deg/sec.
    • They have a latency of around 90 deg/sec and are visually driven to stabilize the retinal image during large-field motion.

    Oculomotor Nerve (CN III)

    • Medial nuclei of CN III innervate the medial rectus muscle.
    • Inferior oblique muscle is innervated by the trochlear nerve (CN IV).

    Size Principle in Skeletal Muscle Activation

    • The size principle states that motor units with the smallest muscle fibers are activated first because they are controlled by the smallest, most highly excitable motor neurons.
    • This principle optimizes the recruitment of tension in skeletal muscles.

    Gaze Holding

    • Gaze holding is achieved through slow vergence, optokinetic reflex, vestibulo-ocular reflex, and pursuit.
    • Saccades are not used for gaze holding, but rather for shifting gaze.

    Extraocular Muscles

    • The time response of extraocular muscles is shorter than most other muscle groups in the human body, with a response time of around 0.2 seconds.
    • Extraocular muscles lack a relaxation period.

    Effects of CN III Damage

    • A patient with a left orbital fracture that blocks the superior division of CN III will elevate their chin, tend to tilt the head to the right, and rotate their neck towards the left.

    Muscle Fiber Anatomy

    • A muscle fiber is surrounded by endomysium.

    Eye Movements

    • A duction is a movement of one eye.
    • Conjugate movements involve the simultaneous movement of both eyes in the same direction.

    Innervation of Extraocular Muscles

    • The superior rectus muscle has contralateral innervation.
    • The lateral rectus muscle has ipsilateral innervation.

    Saccades

    • Saccades are rapid eye movements that can reach speeds of up to 800 deg/sec.
    • They have a latency of around 90 deg/sec and are visually driven to stabilize the retinal image during large-field motion.

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