C motor system
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Questions and Answers

Which of the following is NOT a function of the cerebellum?

  • Coordination of voluntary movements
  • Regulation of balance and posture
  • Sensory input processing
  • Initiation of motor movements (correct)

    • The cerebellum is located:

  • Anterior to the brainstem
  • Posterior to the brainstem (correct)
  • Lateral to the thalamus
  • Superior to the corpus callosum

    • Which of the following best describes the functional role of Purkinje cells in the cerebellum?

  • They excite motor neurons directly.
  • They provide inhibitory output to deep cerebellar nuclei. (correct)
  • They process sensory input from the spinal cord.
  • They send excitatory signals to the thalamus.

    • What structure divides the brain's left and right hemispheres?

    <p>Longitudinal cerebral fissure</p> Signup and view all the answers

    Which type of pathway carries sensory information from the body to the brain?

    <p>Afferent pathway</p> Signup and view all the answers

    The primary motor cortex is located in the:

    <p>Precentral gyrus</p> Signup and view all the answers

    Which of the following statements about efferent pathways is true?

    <p>They carry motor commands from the brain to the body.</p> Signup and view all the answers

    Which part of the brain contains the primary somatosensory cortex?

    <p>Postcentral gyrus</p> Signup and view all the answers

    In a reflex arc, which neuron carries the message from the sensory receptor to the spinal cord?

    <p>Afferent (sensory) neuron</p> Signup and view all the answers

    How many neurons typically carry sensory (afferent) information from the body to the brain?

    <p>3 neurons</p> Signup and view all the answers

    How many neurons are generally involved in transmitting motor (efferent) signals from the brain to the muscles?

    <p>2 neurons</p> Signup and view all the answers

    Which part of the brainstem contains the 'pyramids'?

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

    The "olives" are anatomical structures found in which part of the brainstem?

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

    The cerebral peduncles are found in which region of the brainstem?

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

    Which part of the brainstem is located directly superior to the medulla and inferior to the midbrain?

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

    The pyramids on the medulla are primarily located on which surface?

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

    The "cerebral peduncles" connect which of the following to the brainstem?

    <p>Cerebral cortex</p> Signup and view all the answers

    Which structure in the midline sagittal section is primarily responsible for relaying sensory information to the cerebral cortex?

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

    Which of the following structures lies directly anterior to the central sulcus?

    <p>Pre-central gyrus</p> Signup and view all the answers

    The lateral ventricle, visible in the midline sagittal section, is primarily associated with which part of the brain?

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

    Which structure in a midline sagittal section lies directly inferior to the pons?

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

    Which structure, seen in a coronal section, forms part of the basal ganglia and is located in the lateral wall of the lateral ventricle?

    <p>Head of the caudate nucleus</p> Signup and view all the answers

    The lentiform nucleus, seen in a coronal section, is composed of which of the following structures?

    <p>Putamen and globus pallidus</p> Signup and view all the answers

    What is the main purpose of the internal capsule in the pyramidal system?

    <p>To organize motor fibers for efficient transmission</p> Signup and view all the answers

    Which statement correctly describes the corticospinal tract's pathway?

    <p>It forms pyramids in the medulla and decussates at that level</p> Signup and view all the answers

    What is the role of the corticobulbar tract?

    <p>To synapse with cranial nerve motor nuclei for head and facial movements</p> Signup and view all the answers

    Which tract plays a significant role in controlling fine motor skills of the hands and fingers?

    <p>Lateral Corticospinal Tract</p> Signup and view all the answers

    What is the consequence of the decussation of fibers in the medulla concerning the pyramidal system?

    <p>It ensures contralateral control from each brain hemisphere</p> Signup and view all the answers

    In which part of the brain does the corticobulbar tract primarily synapse to control facial movements?

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

    Which structure allows both the corticobulbar and corticospinal tracts to intermingle before reaching their targets?

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

    What percentage of fibers from the corticospinal tract decussate in the medulla?

    <p>85%</p> Signup and view all the answers

    What is the primary function of the genioglossus muscle?

    <p>Protruding the tongue</p> Signup and view all the answers

    In the event of an upper motor neuron (UMN) lesion affecting the hypoglossal nerve (CN XII), how does the tongue typically deviate when protruded?

    <p>Away from the affected side</p> Signup and view all the answers

    Which pathway is responsible for voluntary muscle control and originates from the cortex?

    <p>Pyramidal pathway</p> Signup and view all the answers

    What is the primary function of the vestibulospinal tract?

    <p>Controlling extensor muscle tone</p> Signup and view all the answers

    Which of the following best describes the function of the rubrospinal pathway?

    <p>Influences flexor muscle tone</p> Signup and view all the answers

    Which condition results in weakness on the same side of the tongue when the genioglossus muscle is involved?

    <p>LMN lesion</p> Signup and view all the answers

    What behavioral response is primarily controlled by the tectospinal tract?

    <p>Reflexive head and neck movements</p> Signup and view all the answers

    In which of the following regions does the reticulospinal pathway originate?

    <p>Reticular nuclei in the pons and medulla</p> Signup and view all the answers

    What is a key function of the extrapyramidal system in muscle control?

    <p>Regulating involuntary muscle tone and posture</p> Signup and view all the answers

    How does bilateral innervation affect the upper face in the event of a UMN lesion?

    <p>Upper face remains mostly unaffected</p> Signup and view all the answers

    Which of the following statements accurately describes the afferent pathways in the nervous system?

    <p>They transmit sensory information to the brain and consist of three neurons.</p> Signup and view all the answers

    Which of the following structures is NOT typically found in the midline sagittal section of the brain?

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

    The medulla is primarily responsible for:

    <p>Regulation of autonomic functions such as heart rate and breathing.</p> Signup and view all the answers

    The thalamus serves as:

    <p>A major relay station for sensory information before it reaches the cerebral cortex.</p> Signup and view all the answers

    The primary function of the cerebellum is to:

    <p>Coordinate voluntary muscle movements and maintain posture.</p> Signup and view all the answers

    The corpus callosum is best described as:

    <p>A bridge of nerve fibers connecting the two cerebral hemispheres.</p> Signup and view all the answers

    Which of the following correctly identifies the components of the basal nuclei?

    <p>Lentiform nucleus, caudate nucleus, and substantia nigra</p> Signup and view all the answers

    The lentiform nucleus consists of which two parts? A) Globus pallidus and putamen B) Caudate nucleus and substantia nigra C) Thalamus and putamen D) Globus pallidus and head of caudate nucleus

    <p>Globus pallidus and putamen</p> Signup and view all the answers

    The substantia nigra is primarily involved in:

    <p>Regulation of motor control and coordination.</p> Signup and view all the answers

    Which of the following statements distinguishes between the pyramidal and extrapyramidal systems?

    <p>The pyramidal system primarily controls voluntary movements, while the extrapyramidal system regulates involuntary movements and reflexes.</p> Signup and view all the answers

    The superior colliculus is primarily involved in: A) Auditory reflexes. B) Visual reflex movements. C) Regulation of autonomic functions. D) Coordination of motor activities.

    <p>Visual reflex movements.</p> Signup and view all the answers

    The inferior colliculus is associated with:

    <p>Auditory reflex movements.</p> Signup and view all the answers

    Which of the following structures is NOT part of the brainstem?

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

    The red nuclei are involved in:

    <p>Coordination of voluntary movements and posture.</p> Signup and view all the answers

    The tectum and tegmentum are components of which part of the brain?

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

    The cerebral aqueduct connects which two structures?

    <p>Third ventricle and fourth ventricle</p> Signup and view all the answers

    The fourth ventricle is located:

    <p>Between the cerebellum and the brainstem.</p> Signup and view all the answers

    The tegmentum is found in which regions of the brainstem?

    <p>Midbrain, pons, and medulla</p> Signup and view all the answers

    The primary function of the pyramidal system is to:

    <p>Control conscious movements.</p> Signup and view all the answers

    Where do the upper motor neurons of the pyramidal system originate?

    <p>Cerebral cortex (pre-central gyrus)</p> Signup and view all the answers

    The upper motor neurons of the pyramidal system pass through which structure in the medulla?

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

    The corticobulbar tracts primarily innervate: A) The spinal cord B) The brainstem C) The cerebellum D) The thalamus

    <p>The brainstem</p> Signup and view all the answers

    The corticospinal tracts are responsible for:

    <p>Controlling voluntary movements of the limbs and trunk.</p> Signup and view all the answers

    The extrapyramidal system is involved in:

    <p>Fine-tuning of movement and coordination.</p> Signup and view all the answers

    Where do the neurons of the extrapyramidal system originate?

    <p>Basal ganglia and other brain centers</p> Signup and view all the answers

    Extrapyramidal system neurons:

    <p>Do not pass through the pyramids of the medulla.</p> Signup and view all the answers

    The upper motor neurons of the pyramidal system originate in which part of the brain?

    <p>Cerebral cortex (pre-central gyrus)</p> Signup and view all the answers

    Upper motor neurons in the pyramidal system pass through which anatomical structure in the medulla?

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

    How many neurons are involved in the pyramidal system?

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

    What are the corticobulbar tracts responsible for innervating?

    <p>Cranial nerve motor nuclei in the brainstem</p> Signup and view all the answers

    The corticospinal tracts carry upper motor neuron signals from the cerebral cortex to which structure?

    <p>The spinal cord</p> Signup and view all the answers

    Lower motor neurons in the pyramidal system:

    <p>Connect to muscles.</p> Signup and view all the answers

    The corticospinal tract sends lower motor neurons from:

    <p>The cerebral cortex to the spinal cord.</p> Signup and view all the answers

    Where do the lower motor neurons of the corticobulbar tract originate?

    <p>The brainstem cranial nerve motor nuclei</p> Signup and view all the answers

    Where do upper motor neurons of the pyramidal system originate?

    <p>Cerebral cortex (pre-central gyrus)</p> Signup and view all the answers

    Upper motor neurons in the pyramidal system pass through which structure in the medulla?

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

    Upper motor neurons send signals to which of the following? A) Muscles directly B) Spinal cord or brainstem (cranial nerve) C) Sensory receptors D) Cerebellum

    <p>Spinal cord or brainstem (cranial nerve)</p> Signup and view all the answers

    Where do lower motor neurons of the pyramidal system originate?

    <p>Brainstem cranial nerve motor nuclei or anterior horn of the spinal cord</p> Signup and view all the answers

    What is the primary function of lower motor neurons in the pyramidal system?

    <p>To convey signals to skeletal muscles</p> Signup and view all the answers

    Which of the following statements is true regarding the pyramidal system?

    <p>It consists of upper and lower motor neurons.</p> Signup and view all the answers

    The pyramidal system includes which of the following tracts?

    <p>Corticobulbar and corticospinal tracts</p> Signup and view all the answers

    The final destination of lower motor neurons in the pyramidal system is:

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

    Where do both the corticobulbar and corticospinal tracts originate?

    <p>Primary motor cortex (pre-central gyrus) in the frontal lobe</p> Signup and view all the answers

    What is the primary purpose of the corticobulbar and corticospinal tracts?

    <p>To initiate motor signals for voluntary movements</p> Signup and view all the answers

    In which part of the brain do the corticobulbar and corticospinal tracts converge?

    <p>Internal capsule</p> Signup and view all the answers

    The corticobulbar tract passes through which part of the internal capsule?

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

    Through which structure do both tracts pass in the midbrain?

    <p>Cerebral peduncles</p> Signup and view all the answers

    What percentage of corticospinal fibers decussate in the medulla?

    <p>85%</p> Signup and view all the answers

    What is the primary function of the corticobulbar tract?

    <p>Control facial, jaw, and neck muscles for head and face movements</p> Signup and view all the answers

    Where does the lateral corticospinal tract synapse?

    <p>With lower motor neurons in the anterior horn of the spinal cord</p> Signup and view all the answers

    How is the body represented on the motor cortex?

    <p>In an inverted manner</p> Signup and view all the answers

    What is the term used to describe the distorted drawing of a human on the motor cortex?

    <p>Motor homunculus</p> Signup and view all the answers

    Which of the following structures is NOT part of the pyramidal motor pathway?

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

    In the internal capsule, where do the corticobulbar and corticospinal tracts pass through?

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

    Which part of the internal capsule is associated with the corticobulbar tract?

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

    The corticospinal and corticobulbar tracts pass through which structure in the midbrain?

    <p>Cerebral peduncles</p> Signup and view all the answers

    Where are the pyramids located within the brain?

    <p>In the medulla</p> Signup and view all the answers

    In the case of unilateral damage to the cerebral hemisphere, the resulting weakness or paralysis will be:

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

    If there is damage to the spinal cord, the resulting weakness or paralysis will be:

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

    What is one of the initial symptoms of an upper motor neuron lesion?

    <p>Weakness/paralysis</p> Signup and view all the answers

    Spasticity is characterized by:

    <p>Increased resistance to passive stretching</p> Signup and view all the answers

    What term describes the condition of overactive reflexes seen in upper motor neuron lesions?

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

    Clonus is most commonly elicited at which anatomical location?

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

    What does Babinski's sign indicate?

    <p>Upper motor neuron lesion</p> Signup and view all the answers

    Which of the following symptoms is characteristic of a lower motor neuron lesion?

    <p>Muscle wasting</p> Signup and view all the answers

    Fasciculations are defined as:

    <p>Involuntary, visible muscle contractions</p> Signup and view all the answers

    Which cranial nerve is the olfactory nerve?

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

    What is the number associated with the optic nerve?

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

    The oculomotor nerve is which cranial nerve number?

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

    The trochlear nerve is designated as which Roman numeral?

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

    The abducens nerve is which number in the cranial nerve sequence?

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

    The trigeminal nerve is which cranial nerve number?

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

    What is the cranial nerve number for the facial nerve?

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

    The vestibulocochlear nerve corresponds to which cranial nerve number?

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

    The glossopharyngeal nerve is which cranial nerve number?

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

    The vagus nerve is designated as which cranial nerve?

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

    The accessory nerve is which cranial nerve number?

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

    The hypoglossal nerve is designated as:

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

    Which cranial nerve is primarily responsible for motor control and also has parasympathetic functions?

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

    The trochlear nerve (IV) is classified as:

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

    The trigeminal nerve (V) is classified as:

    <p>Mixed (motor + sensory)</p> Signup and view all the answers

    The abducens nerve (VI) is which type of nerve?

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

    The facial nerve (VII) is classified as:

    <p>Mixed (motor + sensory + parasympathetic)</p> Signup and view all the answers

    The glossopharyngeal nerve (IX) is classified as:

    <p>Mixed (motor + sensory + parasympathetic)</p> Signup and view all the answers

    The vagus nerve (X) is classified as:

    <p>Mixed (motor + sensory + parasympathetic)</p> Signup and view all the answers

    The accessory nerve (XI) is classified as:

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

    In the corticobulbar tracts, lower motor neurons in their nuclei receive which type of innervation?

    <p>Bilateral innervation</p> Signup and view all the answers

    Lower motor neurons in the corticobulbar tracts receive axons from which of the following?

    <p>Both the opposite side and the same side</p> Signup and view all the answers

    All cranial nerves, except which of the following, receive bilateral innervation?

    <p>VII (Facial)</p> Signup and view all the answers

    In the case of an upper motor neuron injury to the facial nerve (CN VII), which of the following is true?

    <p>The face droops below the eye</p> Signup and view all the answers

    Lower motor neuron injury to the facial nerve (CN VII) results in:

    <p>Facial muscles damaged both above and below the eyes</p> Signup and view all the answers

    An LMN lesion can occur at which of the following locations?

    <p>Anywhere from the cell body to the axon terminals</p> Signup and view all the answers

    The hypoglossal nerve (CN XII) has which type of innervation?

    <p>Contralateral innervation only</p> Signup and view all the answers

    The genioglossus muscle is primarily innervated by which nerve?

    <p>Hypoglossal nerve (CN XII)</p> Signup and view all the answers

    Which part of the facial nerve receives bilateral innervation?

    <p>Muscles of the upper face</p> Signup and view all the answers

    The hypoglossal nerve (CN XII) provides what type of innervation?

    <p>Contralateral innervation only</p> Signup and view all the answers

    An upper motor neuron (UMN) lesion affecting the hypoglossal nerve would cause:

    <p>Weakness on the contralateral side of the tongue</p> Signup and view all the answers

    A lower motor neuron (LMN) lesion of the hypoglossal nerve would cause:

    <p>Weakness on the ipsilateral side of the tongue</p> Signup and view all the answers

    In the event of an upper motor neuron (UMN) lesion affecting other motor cranial nerves (excluding CN VII & XII), what is the expected outcome?

    <p>Minimal impact due to bilateral innervation</p> Signup and view all the answers

    A lower motor neuron (LMN) lesion will cause weakness in which manner for other motor cranial nerves (excluding CN VII & XII)?

    <p>Weakness on the affected side</p> Signup and view all the answers

    In the case of an upper motor neuron (UMN) lesion affecting the facial nerve (CN VII), which statement is true?

    <p>The upper face is mostly unaffected.</p> Signup and view all the answers

    Which of the following accurately describes the medullary (lateral) reticulospinal tract?

    <p>Arises from the nuclei of the reticular formation in the medulla</p> Signup and view all the answers

    What is the main function of the pontine (medial) reticulospinal tract?

    <p>Facilitates contraction and increases muscle tone</p> Signup and view all the answers

    The reticular nuclei in the pons and medulla are primarily responsible for:

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

    Which statement is true regarding the rubrospinal pathway?

    <p>It receives inputs from the cerebellum and cerebral cortex.</p> Signup and view all the answers

    The tectospinal tract is primarily involved in:

    <p>Reflex movements in response to visual stimuli</p> Signup and view all the answers

    What is the primary function of the vestibulospinal tract?

    <p>Maintaining posture and controlling extensor muscle tone</p> Signup and view all the answers

    The fibers of the vestibulospinal tract primarily descend:

    <p>Ipsilaterally in the spinal cord</p> Signup and view all the answers

    What is the primary role of the red nucleus in the rubrospinal pathway?

    <p>Facilitating contraction of flexor muscles</p> Signup and view all the answers

    Which of the following best describes the overall importance of extrapyramidal pathways?

    <p>They control involuntary movements and maintain posture.</p> Signup and view all the answers

    What is the likely neurological condition if a patient exhibits hyperreflexia?

    <p>Upper motor neuron lesion</p> Signup and view all the answers

    Which reflex response is the patellar tendon tap primarily assessing?

    <p>Quadriceps reflex</p> Signup and view all the answers

    What characterizes a lower motor neuron (LMN) lesion?

    <p>Diminished reflex response</p> Signup and view all the answers

    In the context of neurological conditions, what does 'paresis' refer to?

    <p>Partial weakness or motor impairment</p> Signup and view all the answers

    Which condition typically manifests with both upper and lower motor neuron injury presentations?

    <p>Multiple sclerosis</p> Signup and view all the answers

    What is the primary function of the pontine (medial) reticulospinal tract?

    <p>Facilitates contraction and increases muscle tone</p> Signup and view all the answers

    Which pathway primarily controls the tone of flexor muscles in the limbs?

    <p>Rubrospinal pathway</p> Signup and view all the answers

    What is the role of the vestibulospinal tract?

    <p>Controls posture by regulating extensor muscle tone</p> Signup and view all the answers

    Which tract is responsible for reflex movements in response to visual stimuli?

    <p>Tectospinal tract</p> Signup and view all the answers

    The medullary (lateral) reticulospinal tract serves to:

    <p>Inhibit contraction and decrease muscle tone</p> Signup and view all the answers

    Study Notes

    Pyramidal System

    • Controls voluntary motor functions
    • Divided into two tracts: corticobulbar and corticospinal
    • Both originate in the cortex and project to motor neurons
    • Corticobulbar Tract: Controls facial, jaw, and neck muscles for head and face movements
    • Corticospinal Tract: Controls voluntary movements of the body, especially fine motor skills in the limbs
    • Origin in the Cortex: Both tracts initiate motor signals for voluntary movements
    • Internal Capsule: Acts as a conduit, organizing motor fibers for efficient transmission
      • Corticobulbar Tract: Passes through the genu (bend) of the internal capsule
      • Corticospinal Tract: Passes through the posterior limb of the internal capsule
    • Midbrain (Cerebral Peduncles): Directs the tracts downward toward their respective targets
    • Pons: Ensures the continued organization of signals en route to their specific targets
    • Medulla:
      • Corticobulbar Tract: Ends in the brainstem, synapsing with cranial nerve motor nuclei
      • Corticospinal Tract: Forms the pyramids of the medulla, where 85% of fibers decussate
        • The remaining 15% continue as the anterior corticospinal tract
    • Spinal Cord (Corticospinal Tract): The lateral corticospinal tract descends the spinal cord to synapse with lower motor neurons in the anterior horn

    Cranial Nerve Innervation

    • Hypoglossal Nerve (CN XII): Contralateral innervation only
      • (UMN Lesion): Weakness on the contralateral side of the tongue; tongue deviates toward the opposite side of the lesion when protruded
      • (LMN Lesion): Weakness on the ipsilateral side of the tongue; tongue deviates towards the same side as the lesion when protruded
    • Other Motor Cranial Nerves (Except CN VII & CN XII): Bilateral innervation from both left and right motor cortices
      • (UMN Lesion): Minimal impact due to bilateral innervation
      • (LMN Lesion): Weakness on the affected side of the face/body region innervated
    • Facial Nerve (CN VII):
      • Upper Face Innervation: Bilateral innervation
      • Lower Face Innervation: Contralateral innervation only
      • (UMN Lesion):
        • Upper Face: Remains mostly unaffected
        • Lower Face: Weakness on the contralateral side
      • (LMN Lesion): Causes weakness on the ipsilateral side for both upper and lower face

    Extrapyramidal System

    • Involved in the involuntary control of muscle tone, posture, and coordination
    • Key pathways: reticulospinal, rubrospinal, tectospinal, and vestibulospinal tracts
    • Reticulospinal Pathway:
      • Origin: Reticular nuclei in the pons and medulla
      • Pontine (Medial) Reticulospinal Tract: Facilitates muscle contraction and increases muscle tone
      • Medullary (Lateral) Reticulospinal Tract: Inhibits muscle contraction, decreasing muscle tone
    • Rubrospinal Pathway:
      • Origin: Red nucleus in the midbrain
      • Influences the tone of flexor muscles in the limbs
    • Tectospinal Tract:
      • Origin: Superior colliculi in the midbrain
      • Controls reflexive head and neck movements in response to visual stimuli
    • Vestibulospinal Tract:
      • Origin: Vestibular nuclei in the pons and medulla
      • Controls extensor muscle tone
      • Activates antigravity muscles (e.g., leg and trunk muscles) to support posture and balance

    Extrapyramidal Functions Summary

    • Reticulospinal: Adjusts muscle tone and posture
    • Rubrospinal: Controls flexor tone in the limbs
    • Tectospinal: Enables reflexive head and neck movements in response to visual cues
    • Vestibulospinal: Supports postural stability and balance via extensor muscle activation

    Spinal Reflexes

    • Spinal reflexes testing integrity of sensory, CNS and motor reflex arc
    • Patellar tendon tap used to assess reflexes (others include ankle jerk, biceps, triceps)
    • Tap causes brief stretch of muscle spindle, increasing firing of 1a sensory afferent
    • This monosynaptically activates motor nerve supplying that muscle
    • A second branch of the afferent activated an inhibitory interneurone in the spinal cord, which inhibits the motor nerve supplying the antagonist muscle
    • Diminished response (hypo-reflexia) possible in someone with a lower motor neuron lesion
    • Hyperreflexia is more likely if it is an upper motor neurone lesion

    Neurological Conditions and Terminology

    • Stroke: Upper motor neuron (UMN) presentation
    • Polio: Virus that typically affects anterior horn cells causing lower motor neuron (LMN) injury presentation in spinal nerves
    • Multiple Sclerosis: Affects the myelin coating on neurons (UMN and LMN), which damages the conduction of signals along nerves
    • Motor Neuron Disease: Group of diseases that affect motor neurons: UMN, LMN or both

    Neurological Terminology

    • Palsy: Paralysis
    • Paralysis: Loss/ impairment of motor function
    • Paresis: As paralysis but not as severe
    • Paraplegia: Paralysis of lower limbs
    • Hemiplegia: Paralysis of one side of body
    • Monoplegia: Paralysis restricted to one limb or region

    Reticulospinal Pathway

    • Origin: Reticular nuclei in the pons and medulla.
    • Tracts:
      • Pontine (Medial) Reticulospinal Tract: Arises from the pons. Facilitates muscle contraction and increases muscle tone.
      • Medullary (Lateral) Reticulospinal Tract: Arises from the medulla. Inhibits muscle contraction and decreases muscle tone.
    • Function:
      • Most important extrapyramidal pathway.
      • Controls the activity of lower motor neurons.
      • Regulates postural control, initiation, and locomotion.
      • Controls proximal limb movements.

    Rubrospinal Pathway

    • Origin: Red nucleus in the midbrain.
    • Inputs: Cerebellum and cerebral cortex.
    • Projection: Interneurons in the spinal cord.
    • Function: Controls tone of flexor muscles in limbs.

    Other Extrapyramidal Tracts

    • Tectospinal Tract:

      • Origin: Superior colliculi in the midbrain.
      • Projection: Cervical spinal cord.
      • Function: Reflex movements in response to visual stimuli.

    • Vestibulospinal Tract:

      • Origin: Vestibular nuclei in the medulla and pons.
      • Tracts: Medial and Lateral Vestibulospinal tracts.
      • Projection: Spinal cord (ipsilaterally).
      • Synapse: Anterior horn cells.
      • Function:
        • Medial vestibulospinal tract: Maintains posture (antigravity).
        • Lateral vestibulospinal tract: Controls the tone of extensor muscles, increasing limb angle.

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    Test your knowledge about the functions of the cerebellum with this quiz. Identify which of the following options does not pertain to the role of the cerebellum in the nervous system. Challenge yourself and learn more about this crucial part of the brain.

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