Neuroscience Chapter 4 Quiz
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Questions and Answers

What structure is primarily known for connecting the upper motor neurons to the lower motor neurons?

  • Internal capsule (correct)
  • Ventricles
  • Thalamus
  • Cerebellum

    • Which statement best describes the relationship between the basal nuclei and basal ganglia?

  • Basal nuclei can sometimes be referred to as basal ganglia. (correct)
  • Basal nuclei are exclusively referred to as basal ganglia in the periphery.
  • Basal nuclei and basal ganglia are two entirely different structures.
  • Basal ganglia are only found in the brainstem.

    • What anatomical structure runs through the midbrain and connects the third and fourth ventricles?

  • Anterior commissure
  • Optic chiasm
  • Cerebral aqueduct (correct)
  • Hypothalamus

    • Which region of the brain is located anterior to the third ventricle?

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

    What role do the ventricles play in relation to basal nuclei and white matter tracts?

    <p>They provide useful indicators of the positions of basal nuclei and white matter tracts.</p> Signup and view all the answers

    Which of the following best defines the term 'nuclei' in the context of the brain?

    <p>A cluster of neurons surrounded by white matter.</p> Signup and view all the answers

    What structure is associated with the posterior side of the brainstem and is linked to the fourth ventricle?

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

    Which of the following correctly describes the shape of lateral ventricles as one moves posteriorly through the brain?

    <p>The lateral ventricles change shape as they separate.</p> Signup and view all the answers

    What is the primary effect of dopamine released from the substantia nigra pars compacta on the indirect pathway?

    <p>It promotes thalamic output</p> Signup and view all the answers

    What happens to thalamic output when the indirect pathway is inhibited?

    <p>Thalamic output increases</p> Signup and view all the answers

    What percentage of dopaminergic neurons are typically lost by the time symptoms of Parkinson's disease become apparent?

    <p>70%</p> Signup and view all the answers

    What is a hallmark feature commonly associated with Parkinson's disease?

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

    What is the effect of increased output from the substantia nigra pars compacta on thalamic output?

    <p>It results in increased thalamic output</p> Signup and view all the answers

    Which receptors in the indirect pathway are affected by dopamine from the substantia nigra pars compacta?

    <p>D2 receptors</p> Signup and view all the answers

    How does the direct pathway influence thalamic output when activated?

    <p>It promotes thalamic output</p> Signup and view all the answers

    What can result from the improper functioning of the basal ganglia loops in relation to movement?

    <p>Involuntary movements or tremors</p> Signup and view all the answers

    What structure is located lateral to the lateral ventricle and hugs its surface?

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

    Which of the following statements describes the relationship between the caudate nucleus and putamen?

    <p>They are developmentally considered one structure.</p> Signup and view all the answers

    What term is used to collectively refer to the caudate nucleus, putamen, and nucleus accumbens?

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

    Where is the globus pallidus located in relation to the internal capsule?

    <p>Lateral to the internal capsule</p> Signup and view all the answers

    What important white matter tract passes through the middle of the striatum?

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

    Which structure is typically seen inferior to the third ventricle?

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

    What is the primary function of the corticobulbar tract?

    <p>Communication between upper and lower motor neurons</p> Signup and view all the answers

    Which cranial nerve nuclei receive contralateral inputs according to the corticobulbar tract?

    <p>Trochlear nerve (CN IV)</p> Signup and view all the answers

    In a case of a middle cerebral artery stroke, which facial muscle's inability to contract would be most evident?

    <p>Levator anguli oris</p> Signup and view all the answers

    Where is the subthalamic nucleus typically found?

    <p>Caudal to the thalamus</p> Signup and view all the answers

    What structure is located between the globus pallidus and the thalamus?

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

    What happens to the input of the lower half of the facial nerve motor nucleus during a neurological event?

    <p>Only receives contralateral input</p> Signup and view all the answers

    What is the primary role of the thalamus in the brain?

    <p>Relay sensory information to the cerebral cortex</p> Signup and view all the answers

    What marks the end of the nucleus accumbens?

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

    What is the primary consequence of a distal middle cerebral artery occlusion?

    <p>Mainly upper limb issues</p> Signup and view all the answers

    What area is primarily affected in proximal middle cerebral artery occlusions?

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

    How does the cerebellum modify complex movements?

    <p>By integrating sensory information and sending it back to the thalamus</p> Signup and view all the answers

    Which structure primarily provides blood supply to the internal capsule?

    <p>Middle cerebral artery</p> Signup and view all the answers

    What happens when the internal capsule is damaged?

    <p>Widespread and dispersed deficits can arise</p> Signup and view all the answers

    What is the role of the basal ganglia in motor control?

    <p>To integrate cortical inputs and influence motor plans</p> Signup and view all the answers

    What is the primary output center of the basal ganglia?

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

    Which pathway of the basal ganglia promotes cortical activity?

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

    What is the main effect of the indirect pathway in the basal ganglia?

    <p>Inhibits thalamic output to the cortex</p> Signup and view all the answers

    What type of inputs do corticostriate neurons provide to the basal ganglia?

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

    Which component of the basal ganglia has an excitatory influence on inhibitory neurons?

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

    Which nuclei are primarily responsible for output in the basal ganglia?

    <p>Globus pallidus internus and substantia nigra pars reticularis</p> Signup and view all the answers

    How does the thalamus influence the cortex in relation to the basal ganglia?

    <p>By increasing motor program outputs to the cortex</p> Signup and view all the answers

    What is the dominant side of innervation for the genioglossus muscle?

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

    If there is a lesion on the left side affecting the tongue, which way will the tongue deviate?

    <p>To the right</p> Signup and view all the answers

    What role does the medial longitudinal fasciculus play in eye movements?

    <p>It relays signals between eye movement nuclei</p> Signup and view all the answers

    What effect would damage to the left eye field have on eye movement?

    <p>Eye will not be able to move to the left</p> Signup and view all the answers

    What type of fibres are commissural fibres?

    <p>Fibres connecting the two hemispheres</p> Signup and view all the answers

    Which structure carries information from the cortex down to the spinal cord?

    <p>Projection fibres</p> Signup and view all the answers

    How does the cerebellum contribute to eye movement control?

    <p>It facilitates non-conscious control during head position changes</p> Signup and view all the answers

    What happens to the left eye following damage to the left cortex?

    <p>It drifts towards the left</p> Signup and view all the answers

    Which brain structures are primarily involved in regulating eye movements?

    <p>Basal nuclei and cerebellum</p> Signup and view all the answers

    Why is the internal capsule significant in brain structure?

    <p>It contains major projections of fibres to and from the cortex</p> Signup and view all the answers

    Which eye muscle is primarily responsible for abduction?

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

    What is the primary pathway for eye saccades regulation?

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

    Which of the following correctly describes association fibres?

    <p>They run within the same hemisphere</p> Signup and view all the answers

    After a stroke affecting the contralateral muscles, which of the following would be a likely outcome?

    <p>Difficulty in protruding the tongue</p> Signup and view all the answers

    What effect does a disruption to the anterior spinal network typically have on pain and temperature sensation?

    <p>Bilateral loss of sensation below the level of the bleed</p> Signup and view all the answers

    Which pathway continues to function in cases of inflammation affecting the anterior spinal cord?

    <p>Dorsal columns</p> Signup and view all the answers

    In the case of a bleed affecting the anterior spinal cord, which combination of symptoms would be expected?

    <p>Bilateral issues with motor control and pain/temperature sensation</p> Signup and view all the answers

    What occurs in cases of inflammation in the anterior spinal cord compared to a complete transection?

    <p>Selective preservation of specific sensory modalities</p> Signup and view all the answers

    What is a significant symptom of anterior spinal cord injury affecting the interossei muscles?

    <p>Bilateral weakness in motor control</p> Signup and view all the answers

    What is the primary function of the basal plate in the nervous system structure?

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

    What visual field defect is expected from a lesion in the left optic nerve?

    <p>Monocular vision loss in the left eye</p> Signup and view all the answers

    Which symptom is NOT associated with a unilateral infarct at the cerebellar pontine angle?

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

    Which cranial nerve is primarily responsible for the corneal reflex?

    <p>Trigeminal nerve</p> Signup and view all the answers

    How is the visual field affected by injury to the optic radiation passing through the temporal lobe?

    <p>Inferior visual field defect</p> Signup and view all the answers

    What is the pathway for the pupillary light reflex?

    <p>Afferent via optic nerve, efferent via oculomotor nerve</p> Signup and view all the answers

    What happens to the lens of the eye when focusing on a distant object?

    <p>The lens flattens</p> Signup and view all the answers

    Which statement is true regarding macular sparing in visual deficits?

    <p>It is more commonly associated with posterior lesions</p> Signup and view all the answers

    Which layer of the meninges do the cisterns reside between?

    <p>Arachnoid and pia mater</p> Signup and view all the answers

    Increased intracranial pressure can cause which of the following findings?

    <p>Effacement of the sulci</p> Signup and view all the answers

    Which feature is NOT commonly observed in individuals with Parkinson's disease?

    <p>Involuntary jerking movements</p> Signup and view all the answers

    What is the primary cause of movement disorders in Huntington's disease?

    <p>Mutation in the Huntington gene</p> Signup and view all the answers

    What symptom is commonly associated with Parkinson's disease but is less prevalent in Huntington's disease?

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

    Which of the following accurately describes bradykinesia in patients with Parkinson's disease?

    <p>Inability to sustain fast movements</p> Signup and view all the answers

    Which type of tremor is most commonly associated with Parkinson's disease?

    <p>Resting tremor</p> Signup and view all the answers

    What is a consequence of Levodopa therapy in patients with Parkinson's disease?

    <p>Development of dyskinesia</p> Signup and view all the answers

    What cognitive symptom is commonly observed in both Parkinson's and Huntington's diseases?

    <p>Difficulty organizing tasks</p> Signup and view all the answers

    Which of the following psychiatric disorders is especially prevalent in Huntington's disease?

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

    How does Huntington's disease primarily affect the brain's structures?

    <p>Damage to the basal nuclei</p> Signup and view all the answers

    Which symptom is most indicative of cognitive decline in patients with Huntington's disease?

    <p>Difficulty with impulse control</p> Signup and view all the answers

    Which feature reflects the impact of basal ganglia on motor control?

    <p>Shuffling gait due to Parkinson's.</p> Signup and view all the answers

    What is the expected gait pattern in a patient with Parkinson's disease?

    <p>Short-stepped, shuffling gait</p> Signup and view all the answers

    What condition may result from an occlusion of the middle cerebral artery (MCA)?

    <p>Global aphasia</p> Signup and view all the answers

    What type of tremor is typically observed while a patient with Parkinson's is at rest?

    <p>Resting tremor</p> Signup and view all the answers

    Which sensory pathway is responsible for transmitting pain and temperature sensations?

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

    Which characterizes the cognitive decline observed in Huntington's disease?

    <p>Struggles with initiating tasks and attention</p> Signup and view all the answers

    What is likely affected in a patient with PCA occlusion presenting with face recognition difficulties?

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

    What happens to sensory pathways originating from the lower limbs in the dorsal column-medial lemniscus pathway?

    <p>They synapse in the gracile nucleus.</p> Signup and view all the answers

    What results from a right-sided MCA occlusion regarding neglect syndrome?

    <p>Unilateral spatial neglect on the left side</p> Signup and view all the answers

    What is the clinical significance of the anterior spinal artery in spinal cord blood supply?

    <p>It supplies the ventral two-thirds of the spinal cord.</p> Signup and view all the answers

    Which of the following symptoms is associated with thalamic syndrome?

    <p>Loss of proprioception</p> Signup and view all the answers

    What type of sensory loss is associated with alexia without agraphia from PCA occlusion?

    <p>Inability to read but can write</p> Signup and view all the answers

    What is a common effect of demyelination in diseases like multiple sclerosis?

    <p>Signal blockade due to lack of myelination</p> Signup and view all the answers

    What is the primary consequence of cerebellar tonsil herniation through the foramen magnum?

    <p>Injury to the lower brainstem</p> Signup and view all the answers

    Which type of herniation is characterized by symmetrical herniation through the tentorial notch?

    <p>Axial herniation</p> Signup and view all the answers

    What is the result of unilateral mass effect causing lateral herniation?

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

    Which of the following is a consequence of occlusion of the anterior cerebral artery?

    <p>Contralateral lower limb weakness</p> Signup and view all the answers

    What is the characteristic presentation of a middle cerebral artery infarct?

    <p>Contralateral facial and arm weakness</p> Signup and view all the answers

    Which statement accurately describes the results of degeneration in the substantia nigra?

    <p>Reduction of cognitive functions occurs</p> Signup and view all the answers

    Which artery is involved in supplying the occipital lobe?

    <p>Posterior cerebral artery</p> Signup and view all the answers

    What is the function of the anterior commissure in the brain?

    <p>Connects the two hemispheres</p> Signup and view all the answers

    Which pathway is responsible for maintaining tone in flexor compartments?

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

    What type of brain tissue is primarily connected to the cerebral cortex and subcortical regions?

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

    Which anatomical structure is involved in eye movements and is located posterior to the third ventricle?

    <p>Posterior commissure</p> Signup and view all the answers

    What is the primary origin of the tectospinal tract?

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

    What leads to bradykinesia in patients with substantia nigra degeneration?

    <p>Insufficient dopamine production</p> Signup and view all the answers

    What is the function of the reticulospinal tract?

    <p>Control of posture and balance</p> Signup and view all the answers

    Which type of reflex is associated with the rubrospinal pathway?

    <p>Complex limb reflexes</p> Signup and view all the answers

    What does the absence of a hyperdense middle cerebral artery indicate in a CT scan?

    <p>Could still indicate an MCA stroke</p> Signup and view all the answers

    Which of the following structures does NOT contribute to the growth of the basilar artery?

    <p>Internal carotid artery</p> Signup and view all the answers

    What posture is associated with injury at or above the red nucleus?

    <p>Decorticate positioning</p> Signup and view all the answers

    What area is primarily affected by an infarct in the anterior cerebral artery region?

    <p>Medial aspect of frontal lobe</p> Signup and view all the answers

    Where do 75% of the fibers decussate in the pyramidal system?

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

    What is the primary role of the cerebellum in motor control?

    <p>Coordination of posture and balance</p> Signup and view all the answers

    Which of the following statements about the reticulospinal tract is true?

    <p>It is important for both autonomic and motor control.</p> Signup and view all the answers

    The decerebrate posture is characterized by which of the following?

    <p>Internally rotated arms and extended legs</p> Signup and view all the answers

    The rubrospinal pathway is primarily received inputs from which structure?

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

    Which tract primarily innervates muscles to maintain posture in response to visual stimuli?

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

    Which pathway primarily involves voluntary movements initiated by upper motor neurons?

    <p>Lateral corticospinal tract</p> Signup and view all the answers

    What characterizes the reticulospinal tract's contribution to lower motor neuron function?

    <p>Excitation and inhibition via interneurons</p> Signup and view all the answers

    What is currently understood about the primary immune cells present in most affected tissues in multiple sclerosis?

    <p>Macrophages are the main immune cells present.</p> Signup and view all the answers

    In the case of a central spinal cord lesion at C5-C6, which sensory loss is expected below the lesion level?

    <p>Loss of pain and temperature sensation.</p> Signup and view all the answers

    Which component of the Glasgow Coma Scale assesses the patient's ability to respond appropriately to verbal stimuli?

    <p>Verbal response.</p> Signup and view all the answers

    What is a common outcome when there is a middle cerebral artery (MCA) infarction?

    <p>Severe motor and sensory deficits in the face and arm.</p> Signup and view all the answers

    What type of tremor is most commonly associated with Parkinson's disease?

    <p>Resting tremor.</p> Signup and view all the answers

    What is the main purpose of synthetic glucocorticoids in treating demyelinating conditions?

    <p>To regulate the immune response and inflammation.</p> Signup and view all the answers

    Which imaging method is most appropriate for visualizing the extent of a lesion in the brain?

    <p>MRI.</p> Signup and view all the answers

    What are the primary components of the internal capsule?

    <p>Corticospinal tracts and cranial nerve pathways.</p> Signup and view all the answers

    In the context of multiple sclerosis treatments, what type of approach aims to decrease the immune response to the disease?

    <p>Disease modifying therapeutics.</p> Signup and view all the answers

    What anatomical change occurs during subfalcine herniation?

    <p>Shift of brain tissue across the midline.</p> Signup and view all the answers

    Which type of tremor is characteristic of cerebellar dysfunction?

    <p>Action tremor.</p> Signup and view all the answers

    What additional benefit does the use of levodopa and carbidopa provide in treating Parkinson's disease?

    <p>They prevent the breakdown of levodopa in peripheral tissues.</p> Signup and view all the answers

    Which artery supplies the largest area of the brain, excluding the outer layers?

    <p>Middle cerebral artery.</p> Signup and view all the answers

    What is the primary function of the vestibular nuclei?

    <p>To relay information about head position from the inner ear</p> Signup and view all the answers

    How do the vestibular nuclei affect eye movements?

    <p>They project through the medial longitudinal fasciculus to mediate reflex eye movements.</p> Signup and view all the answers

    What is a likely consequence of damage to the vestibular nucleus?

    <p>Deterioration in eye movement coordination</p> Signup and view all the answers

    Which artery is primarily associated with speech issues in the context of the provided case?

    <p>Middle cerebral artery</p> Signup and view all the answers

    What could explain Rachael's temporary loss of vision in her left eye?

    <p>Occlusion in the left ophthalmic artery</p> Signup and view all the answers

    What is the likely source of Rachael's clumsiness based on the case description?

    <p>Anterior cerebral artery involvement</p> Signup and view all the answers

    What is Horner’s syndrome characterized by?

    <p>Partial ptosis and miosis</p> Signup and view all the answers

    In the context of multiple sclerosis, what is primarily attacked by immune cells?

    <p>Myelin sheaths produced by oligodendrocytes</p> Signup and view all the answers

    What role does the vestibulospinal tract play in maintaining posture?

    <p>It drives tone in antigravity muscles.</p> Signup and view all the answers

    How do the different branches of the internal carotid artery contribute to Rachael's symptoms?

    <p>They supply the optic nerve head and anterior brain regions.</p> Signup and view all the answers

    What effect does vestibular input have on eye position adjustment?

    <p>It combines visual information and head position data.</p> Signup and view all the answers

    What may contribute to Rachael's transient ischemic attack (TIA) diagnosis?

    <p>Emboli affecting retinal blood supply</p> Signup and view all the answers

    What central area could be impacted by posterior choroidal artery issues?

    <p>Optic nerve head</p> Signup and view all the answers

    What anatomical structure assists in integrating eye movements with head position adjustments?

    <p>Medial longitudinal fasciculus</p> Signup and view all the answers

    Which area is most likely affected if there are motor symptoms present on the right side of the body?

    <p>Left frontal lobe, anterior cerebral artery territory</p> Signup and view all the answers

    Study Notes

    Ventricles and Basal Ganglia

    • Ventricles are cavities in the brain filled with cerebrospinal fluid.
    • They provide a useful landmark for identifying the position of basal nuclei and white matter tracts.
    • The ventricle system is composed of the lateral ventricles, the third ventricle, the cerebral aqueduct, and the fourth ventricle.
    • The lateral ventricles are the largest and extend into all lobes of the cerebrum: frontal, parietal, occipital, and temporal.
    • The third ventricle is located in the diencephalon and connects to the lateral ventricles via the interventricular foramina.
    • The cerebral aqueduct connects the third ventricle to the fourth ventricle.
    • The fourth ventricle is located in the brainstem and connects to the subarachnoid space via the lateral apertures and the median aperture.

    Basal Nuclei

    • Basal nuclei are clusters of neuronal cell bodies located in the deep brain regions, involved in motor control, learning, and cognition.
    • The caudate nucleus and putamen are collectively referred to as the striatum, which is primarily involved in receiving input from the cortex and sending projections to the globus pallidus.
    • The globus pallidus is a nucleus located medial to the putamen, responsible for output projections to the thalamus and brainstem.
    • The subthalamic nucleus, located ventral to the thalamus near the cerebral peduncle, plays a role in regulating basal ganglia activity.
    • The substantia nigra, also located in the midbrain, is involved in movement control and is associated with dopamine production.
    • The two parts of the substantia nigra are the pars compacta and the pars reticularis.
    • The internal capsule, a large white matter tract, runs between the caudate nucleus, putamen and thalamus.
    • The internal capsule carries important motor pathways from the cortex to the brainstem and spinal cord, including the corticospinal tract and corticobulbar tract.

    Blood Supply of the Internal Capsule

    • The internal capsule is primarily supplied by the middle cerebral artery (MCA) and its perforating branches.
    • Blockage of the MCA or its perforating branches can lead to a stroke that affects a large area of the internal capsule, potentially resulting in significant motor deficits due to damage to the corticospinal and corticobulbar tracts.

    Corticobulbar Tract and Cranial Nerve Nuclei

    • The corticobulbar tract connects the cerebral cortex (upper motor neurons) to the cranial nerve nuclei (lower motor neurons) in the brainstem.
    • This pathway controls the muscles of the face, tongue, and neck, mediating voluntary movements of these structures.
    • Cranial nerve nuclei receive both ipsilateral and contralateral input, allowing for some compensation in case of injury to one side of the brain.
    • Exceptions to this bilateral innervation rule involve the facial nerve (CNVII) and hypoglossal nerve (CNXII).
    • The facial nerve nucleus has a superior part that receives input from both sides of the brain and an inferior part that receives input only from the contralateral side.
    • Damage to the dominant side of the brain can result in facial droop and weakness on the contralateral side of the face.
    • The hypoglossal nerve (CNXII), which controls tongue movements, also has a superior part receiving bilateral input and an inferior part (genioglossus) receiving primarily contralateral input.
    • A lesion on one side of the brain can cause the tongue to deviate towards the weakened side when protruded.

    Organisation of White Matter in the Cortex

    • The white matter of the brain is organized into three types of fibers: association fibers, projection fibers, and commissural fibers.
    • Association fibers connect different regions within the same hemisphere of the brain.
    • Projection fibers transmit information between the cerebral cortex and other brain regions or the spinal cord.
    • Commissural fibers connect corresponding regions of the two hemispheres.
    • The internal capsule is a major pathway for projection fibers; it carries motor, sensory, and other signals between the cortex and lower brain structures.

    Basal Nuclei and Eye Movements

    • Eye movements are regulated by specialized brain areas, including frontal eye fields, supplementary eye fields, and parietal eye fields.
    • These eye fields contribute to planning and executing eye movements, and they pass through the basal nuclei pathways.
    • The basal nuclei can modify and adjust these eye movements based on input from the cortical regions.
    • Damage to the cortical eye fields can cause strabismus (deviation of eye gaze) toward the affected side.

    Basal Nuclei and Motor Control

    • Basal nuclei play a crucial role in controlling and refining motor activity, working in conjunction with the motor cortex and other brain regions.
    • They receive input from the cortex, process this information, and send signals to the thalamus and brainstem, which influence motor function and movement planning.
    • The two main pathways within the basal nuclei are direct and indirect.
    • The direct pathway enhances motor activity, while the indirect pathway inhibits motor activity.
    • Both pathways involve a series of interconnected neurons within the basal nuclei, leading to a delicate balance between excitation and inhibition.

    Parkinson's Disease

    • Parkinson's disease is a neurodegenerative disorder characterized by tremors, muscle rigidity, slow movements (bradykinesia), and postural instability.
    • It is associated with the loss of dopamine-producing neurons in the substantia nigra pars compacta, leading to an imbalance in the basal ganglia circuits and a reduction in dopamine signaling.

    Huntington's Disease

    • Huntington's disease is a neurodegenerative disorder caused by a genetic mutation responsible for the production of an abnormal protein that accumulates in the brain.
    • It primarily affects the striatum and other basal ganglia structures, leading to uncontrolled movements (chorea), cognitive decline, and behavioral changes.

    Basal Ganglia: Indirect Pathway

    • The indirect pathway inhibits thalamic output, modulating cortical activity.
    • This applies to both the thalamus and brainstem.
    • The direct and indirect pathways work in parallel to refine and select cortical programs.

    Substantia Nigra Pars Compacta (SNc)

    • The SNc contains dopaminergic neurons that modulate the basal ganglia.
    • Dopamine has different effects on inhibitory neurons depending on the receptors expressed.
    • Dopamine inhibits the indirect pathway (D2 receptors) and stimulates the direct pathway (D1 receptors).
    • This ultimately increases thalamic output by reducing inhibition on the indirect pathway and stimulating the direct pathway.

    Parkinson's Disease

    • Parkinson's disease results from the loss of dopaminergic neurons in the SNc.
    • By the time symptoms appear, approximately 70% of these neurons are lost.
    • This leads to decreased thalamic output, causing bradykinesia (slowing of movements).
    • The loss of function in these loops can also result in tremor and involuntary movements.

    Parkinson's Disease: Diagnosis

    • Clinical Inspection:
      • Reduced spontaneous movements, including hand gestures and eye blinking.
      • Resting tremor.
      • Fidgeting and crossing/uncrossing legs (dyskinesia), a complication of long-term Levodopa therapy.
    • Tests:
      • Bradykinesia: Assess rapid alternating movements (e.g., hand flipping, finger pinching).
      • Rigidity: Passive manipulation of limbs, particularly the wrist or elbow.
      • Tremor: Resting, postural, and kinetic.
      • Gait and Balance: Reduced step length, shuffling gait, loss of balance during turns, and loss of heel strike.

    Huntington's Disease

    • Huntington's disease is caused by a mutation in the Huntington gene.
    • It leads to atrophy of the putamen, caudate, and other basal nuclei.
    • This results in movement disorders, cognitive deficits, and psychiatric problems.

    Huntington's Disease: Symptoms

    • Movement Disorders:
      • Chorea: Involuntary jerking movements.
      • Rigidity and dystonia: Similar to upper motor neuron lesions.
      • Abnormal eye movements: Difficulty initiating movements.
      • Impaired gait, posture, and balance.
      • Difficulty with speech and swallowing.
    • Cognitive Disorders:
      • Difficulty organizing, prioritizing, and focusing.
      • Perseveration: Difficulty shifting thoughts, behaviors, or actions.
      • Lack of impulse control.
      • Lack of awareness of one's behaviors and abilities.
      • Slowness in processing thoughts and finding words.
      • Difficulty learning new information.
    • Psychiatric Disorders:
      • Depression: Feelings of sadness, apathy, irritability, and social withdrawal.
      • Obsessive Compulsive Disorder.
      • Mania: Overactive mood with elevated self-esteem.
      • Bipolar Disorder.

    Basal Nuclei Topography

    • Caudate Nucleus: Associated with association cortices, including the prefrontal and temporal lobes.
    • Putamen: Primarily associated with motor and sensory functions.
    • Nucleus Accumbens: Involved in the limbic system, contributing to neuropsychiatric symptoms.

    Midbrain, Pons, and Medulla Reflexes

    • Midbrain Rostral/Caudal:
      • Pupillary Light Reflex: Constriction of both pupils, afferent via optic nerve, efferent via oculomotor nerve.
      • Pretectal Nucleus: Receives afferent fibers for the pupillary light reflex.
    • Pons Rostral/Caudal:
      • Corneal Reflex: Afferent via trigeminal nerve, efferent via facial nerve.
      • Jaw Jerk Reflex: Afferent via trigeminal nerve, efferent via ?
    • Medulla Rostral/Caudal:
      • Salivation and Gag Reflex: Afferent and efferent via cranial nerves IX and X.
      • Vestibulo-ocular Reflex: Reflexive eye movements in response to head movement.

    Mapping Visual Field Defects

    • Left Optic Nerve Lesion: Monocular vision loss in the left eye.
    • Left Optic Radiation Lesion:
      • Anterior Bundle (Meyer's Loop): Affects the inferior retinal quadrant, causing a superior visual field defect.
      • Superior Bundle: Affects the superior retinal quadrant, causing an inferior visual field defect.
      • Macular Sparing: Suggests a more anterior lesion.

    Cerebellar Pontine Angle Infarct

    • Result in ipsilateral cerebellar dysfunction, cranial nerve deficits, and potentially lateral medullary symptoms if the infarct extends.
    • Ipsilateral Cerebellar Dysfunction:
      • Impaired coordination of voluntary movements.
      • Dysmetria: Difficulty judging distance and range of motion.
      • Dysdiadochokinesis: Difficulty performing rapid alternating movements.
      • Intention tremor: Worsening tremor as the limb approaches its target.
      • Hypotonia: Decreased muscle tone.
    • Cranial Nerve Deficits:
      • Facial nerve palsy: Weakness or paralysis of facial muscles.
      • Vestibulocochlear nerve: Hearing loss, tinnitus, and vertigo.
      • Trigeminal nerve: Sensory impairment of the face.
      • Abducens nerve: Lateral gaze paralysis.

    Imaging Quizzes Week 12 Anatomy

    • Station 1:
      • CT Brain: Identify structures like the left ventricle, choroid plexus, and cerebral aqueduct.
      • CSF Flow: Understand how CSF circulates from the cerebral aqueduct to the subarachnoid space.
    • Station 2:
      • CT Brain: Recognize subdural hematomas, midline shift (e.g., of the septum pellucidum), sulci effacement, and cerebral/cerebellar herniation.
      • Types of Herniation: Understand the different types of herniation (subfalcine, transtentorial, cerebellar tonsil, axial, lateral).
    • Station 3:
      • CT Brain: Label the major arteries supplying the brain (e.g., anterior cerebral artery, middle cerebral artery, posterior cerebral artery, basilar artery, vertebral artery).
    • Station 4:
      • CT Brain: Identify the hyperdense middle cerebral artery (MCA) as a sign of MCA infarct.
      • Basal Ganglia: Label the caudate nucleus, putamen, globus pallidus, and internal capsule.

    Week 12 Anatomy Pre-Lab Questions

    • Labeling the Ventricular System: Locate the anterior, superior, inferior, and posterior horns of the lateral ventricles, the third ventricle, the cerebral aqueduct of Sylvius, and the fourth ventricle.
    • Labeling Axial Images: Identify the position of structures in axial images, from rostral to caudal, including the lateral ventricles, caudate nucleus, temporal lobes, and occipital lobes.
    • Fiber Types: Categorize fibers as commissural, projection, or association based on their location and function.
    • Basal Ganglia Structures: Label the caudate nucleus, putamen, globus pallidus externa/interna, subthalamic nucleus, and substantia nigra on an axial image.
    • Blood Supply of the Brain: Label the main arteries supplying the brain, including the anterior cerebral artery, anterior communicating artery, internal carotid artery, middle cerebral artery, posterior communicating artery, posterior cerebral artery, superior cerebellar artery, basilar artery, posterior inferior cerebellar artery, anterior spinal artery, and vertebral artery.

    Specimen Notes Week 12

    • Claustrum: A thin sheet of neurons and glial cells that connects to the cerebral cortex and subcortical regions.
    • Substantia Nigra Degeneration (Parkinson's Disease):
      • Effects: Reduction in dopamine production, leading to motor (tremor, rigidity, bradykinesia, postural instability) and non-motor (cognitive impairment, depression, anxiety, REM sleep disorder) symptoms.
    • Cerebral Vascular Accidents (CVAs):
      • Anterior Cerebral Artery (ACA) Occlusion: Symptoms include contralateral lower limb weakness and sensory loss, urinary incontinence, impaired judgment, personality changes, abulia, and transcortical motor aphasia.
      • Middle Cerebral Artery (MCA) Occlusion: Symptoms include contralateral hemiparesis and hemisensory loss, homonymous hemianopia, global aphasia, apraxia, neglect syndrome, and Gerstmann syndrome.
      • Posterior Cerebral Artery (PCA) Occlusion: Symptoms include visual field defects, contralateral hemiparesis, and sensory loss.

    Posterior Cerebral Artery (PCA) Lesions

    • May cause Homonymous hemianopia (similar to Middle Cerebral Artery (MCA) lesions)
    • May cause visual agnosia (difficulty recognizing objects)
    • May cause prosopagnosia (difficulty recognizing faces)
    • May cause color agnosia (difficulty recognizing colors)
    • May cause alexia without agraphia (difficulty reading, but can write)
    • May cause memory impairment, due to involvement of the hippocampus and parahippocampal gyrus
    • May cause thalamic syndrome (sensory loss, pain, and some movement disorders)

    Spinal Cord Pathways

    • Spinothalamic Tract: Transmits pain and temperature information.
      • Sensory information enters spinal nerve, cell body in dorsal root ganglion
      • Neuron projects into dorsal horn
      • Relay neuron ascends through spinal cord after crossing to the other side, traveling in the ventrolateral white matter (spinothalamic tract).
      • Pathway continues up the spinal cord, through the medulla hole and the brainstem to the thalamus
    • Dorsal Column Medial Lemniscus (DCML): Transmits light touch and proprioception.
      • Sensory information enters spinal nerve, cell body in dorsal root ganglion
      • Axon ascends through the dorsal column (divided into the cuneate fasciculus for the upper limb and the gracile fasciculus for the lower limb).
      • Axons synapse at the cuneate or gracile nucleus in the medulla, then cross and decussate through the medial lemniscus (a white matter pathway).
    • Corticospinal Tract: Transmits motor signals from the motor cortex to the spinal cord.
      • Motor neuron resides in the ventral horn
      • Axon leaves via the ventral root and joins the spinal nerve
      • Axon originates in the precentral gyrus (or premotor or supplementary motor area)
      • Travels through the corticospinal tract, crosses over to the lateral side of the spinal cord to innervate muscles.

    Spinal Cord Blood Supply

    • Anterior Spinal Artery: Supplies the ventral 2/3 of the spinal cord.
    • Posterior Spinal Arteries: Supplies the posterior 1/3 of the spinal cord.
    • Radicular Arteries: Connect the anterior and posterior spinal arteries and form a network.

    Spinal Cord Injury

    • Transverse Myelitis: Inflammation of the spinal cord
    • Multiple Sclerosis: Autoimmune disorder that attacks the myelin sheath of neurons.
      • Can affect the anterior 2/3 of the spinal cord, causing bilateral loss of pain and temperature sensation below the lesion.
      • If only some myelin is affected, some sensation/motor might still be present.
      • Bilateral motor issues may present, potentially with preserved proprioception if the damage is restricted to the anterior side
      • A complete spinal cord injury will affect all pathways bilaterally.

    Extrapyramidal Tracts

    • Rubrospinal Pathway: Originates in the red nucleus (midbrain), crosses to the other side, and projects down the lateral aspect of the medulla and spinal cord to synapse on motor neurons.
      • Receives input from the cerebellum
      • Involved in maintaining tone in flexor compartments and complex reflexes in the limbs.
      • Involved in inhibiting contraction of antigravity muscles (extensors).
      • Injuries above the red nucleus can present with decorticate posturing (flexion of upper limbs, drawing of limbs towards the core, extension of legs).
    • Tectospinal Tract: Originates in the superior colliculus (midbrain), crosses to the contralateral side, and runs in the anterior medial part of the spinal cord to innervate muscles.
      • Receives input from the retina and visual association areas
      • Involved in reflex eye movements in response to visual stimuli or head position.
      • It contributes to maintaining posture in response to visual stimuli, mainly in head and neck muscles.
    • Reticulospinal Tract: Originates in the reticular formation (pons), primarily ipsilateral (some bilateral input).
      • Involved in extrapyramidal control of lower motor neurons.
      • Medial nuclei drive excitatory motor control.
      • Lateral nuclei inhibit motor control through interneurons.
      • Important for postural control and modulating heart rate and respiratory rates.
      • Part of the autonomic nervous system.
      • Injury below the red nucleus, particularly in the pontine/medullary region, creates a decerebrate posture (extended and internally rotated arms).
    • Vestibulospinal Tract: Originates in the vestibular nuclei (inner ear, receives input from vestibular ganglion).
      • Involved in maintaining posture and balance, and controlling eye movements (vestibulo-ocular reflex) in coordination with the medial longitudinal fasciculus (MLF).
      • Lateral tract drives tone in antigravity muscles.
      • Medial tract assists in postural adjustments related to head and eye movements.
      • Damage to the vestibular nuclei impairs the vestibulo-ocular reflex.

    Clinical Cases

    • Case 1: Patient experiences temporary visual disturbance, clumsiness, slurring of speech, and difficulty with motor control.
      • Likely diagnosis: Atherosclerosis in the left internal carotid artery with potential emboli.
      • Symptoms point to disruption of the ophthalmic artery (for vision), anterior cerebral artery (for right-sided motor symptoms), and the middle cerebral artery (for speech and motor control).
      • Possible cause: Blockage or occlusion in the internal carotid artery, middle cerebral artery, or anterior cerebral artery, as well as potential emboli.
    • Case 2: Patient with multiple sclerosis experiences dizziness, tingling, and blurry vision.
      • Diagnosis: Multiple sclerosis.
      • Likely cause: Demyelination of neurons within the central spinal cord, affecting spinothalamic and sensory pathways.
    • Sports Injury Case: Patient experiences decorticate posturing.
      • Likely cause: Injury to the red nucleus, likely caused by a stroke or trauma.
      • Decorticate posturing is a result of unmodulated flexor activity and inability to inhibit extensor function.

    Glasgow Coma Scale

    • A scoring system used to assess the level of consciousness in patients.
    • Assesses eye opening, verbal response, and motor response.
    • Scores range from 3 to 15.

    Glasgow Coma Scale (GCS)

    • GCS used to assess level of consciousness
    • Score based on eye opening, verbal response, and motor response
    • Anything less than 8 indicates coma and requires immediate medical attention

    Concussion

    • Repeated concussions can cause injuries to the white matter and long tracts
    • Tua Taigivaloa has sustained multiple concussions but passes all protocols
    • Debate on whether he is safe to play despite ongoing concussions

    Ventricular system

    • Identify major components of the ventricular system
    • Appreciate main cisterns where Cerebrospinal Fluid (CSF) may accumulate
    • Understand how typical ventricular anatomy changes due to:
      • Midline shift
      • Subfalcine herniation
      • Transtentorial herniation

    Cerebral Circulation

    • Identify major arteries contributing to cerebral circulation
    • Recognize hyperdense middle cerebral artery sign on CT
    • Understand how imaging can visualize the extent of a lesion

    Basal Ganglia

    • Components include caudate, globus pallidus, and putamen
    • Anterior and posterior limbs of the internal capsule pass through these structures
    • Parkinson’s disease associated with resting tremors
    • Cerebellar dysfunction associated with action tremors

    Tremors

    • Parkinson's resting tremor - pill rolling
    • Cerebellar tremors - worse at the end of a movement, high amplitude, zigzagging movements
    • Cerebellar tremors can also cause rapid uncontrollable eye movements
    • Cerebellar testing includes finger-to-nose and heel-to-shin tests
    • Parkinson's can be investigated through vascular tumor scans
    • Positron emission tomography (PET) scans can visualize the loss of dopaminergic receptors

    Parkinson's Treatment

    • Levodopa + carbidopa: Inhibit dopa decarboxylase enzyme peripherally
    • Anticholinergics and MAOB inhibitors can be used to manage the condition

    Cerebellar Dysfunction Treatment

    • Thalamic deep brain stimulation used to address cerebellar dysfunction

    Tracts

    • Visceral tracts cross the longitudinal fissure to join hemispheres via the corpus callosum and anterior/posterior commissures
    • Association tracts connect regions within one hemisphere
    • Short association tracts connect regions within one lobe, while long tracts connect across lobes (e.g., arcuate fasciculus, superior longitudinal fasciculus)
    • Major tracts include:
      • Corticospinal
      • Corticopontine
      • Corticobulbar
      • Dorsal Column Medial Lemniscus (DCML)
      • Medial Lemniscus

    Internal Capsule

    • Acts as a highway for fibers traveling through the brain
    • Composed of anterior, posterior limbs, and genu
    • Runs through the caudate, globus pallidus, and putamen
    • Posterior limb carries corticospinal tract and some somatosensory fibers from the thalamus to the cortex
    • Damage to this region affects contralateral motor and sensory function
    • Most corticobulbar tracts (cranial nerves) pass through the genu

    Middle Cerebral Artery (MCA)

    • Branch of the internal carotid artery
    • Largest of the three cerebral arteries
    • Supplies most of the brain except the outer layers
    • M1 segment supplies the basal ganglia
    • M2 segment passes through the insula cortex
    • M3 segment loops back on itself (opercular segment)
    • M4 segment wraps around the entire cortex, supplying motor, sensory, auditory, and posterior limb regions
    • Infarction in this area is devastating, causing significant functional impairments

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    Test your knowledge on key anatomical structures and relationships within the brain in this Neuroscience Chapter 4 Quiz. Questions cover the connections between upper and lower motor neurons, the role of the basal nuclei, and the anatomy surrounding the ventricles. Challenge yourself and deepen your understanding of neuroscientific concepts.

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