Podcast
Questions and Answers
What is the primary function of the cerebellum?
What is the primary function of the cerebellum?
Which part of the cerebellum is located next to the foramen magnum?
Which part of the cerebellum is located next to the foramen magnum?
What separates the anterior lobe from the posterior lobe of the cerebellum?
What separates the anterior lobe from the posterior lobe of the cerebellum?
Which cerebellar peduncle is considered the major output arm of the cerebellum?
Which cerebellar peduncle is considered the major output arm of the cerebellum?
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What anatomical feature divides the cerebellum into two hemispheres?
What anatomical feature divides the cerebellum into two hemispheres?
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What type of fibers predominantly come through the middle cerebellar peduncle?
What type of fibers predominantly come through the middle cerebellar peduncle?
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Which feature of the cerebellum is visible in an anterior view?
Which feature of the cerebellum is visible in an anterior view?
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What marks the deepest fissure of the cerebellum?
What marks the deepest fissure of the cerebellum?
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What type of visual field defect is commonly associated with pituitary gland tumors?
What type of visual field defect is commonly associated with pituitary gland tumors?
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Where must a lesion occur to cause contralateral homonymous hemianopia?
Where must a lesion occur to cause contralateral homonymous hemianopia?
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Which of the following statements about optic radiation lesions is true?
Which of the following statements about optic radiation lesions is true?
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What is the significance of macular sparing in visual field defects?
What is the significance of macular sparing in visual field defects?
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In the context of the pupillary reflex, where do the afferent optic nerve fibers project?
In the context of the pupillary reflex, where do the afferent optic nerve fibers project?
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What role do interneurons play in the pupillary reflex?
What role do interneurons play in the pupillary reflex?
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Why can a patient experience inferior quadrantanopia?
Why can a patient experience inferior quadrantanopia?
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What is true regarding the lesions that result in quadrantanopia?
What is true regarding the lesions that result in quadrantanopia?
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Which visual field defect would be expected if there is a lesion in the area of Meyer’s loop?
Which visual field defect would be expected if there is a lesion in the area of Meyer’s loop?
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What may occur if there are problems with the optic nerve after localizing the afferent pupillary response?
What may occur if there are problems with the optic nerve after localizing the afferent pupillary response?
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What is the function of the posterolateral fissure in the cerebellum?
What is the function of the posterolateral fissure in the cerebellum?
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Which nuclei are primarily found in the deep white matter of the cerebellum?
Which nuclei are primarily found in the deep white matter of the cerebellum?
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What is the primary pathway for cerebellar outputs?
What is the primary pathway for cerebellar outputs?
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How does light travel through the retina to reach photoreceptors?
How does light travel through the retina to reach photoreceptors?
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What does bitemporal hemianopia refer to?
What does bitemporal hemianopia refer to?
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What is the significance of the optic disc in diagnosing intracranial pressure?
What is the significance of the optic disc in diagnosing intracranial pressure?
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What happens during lesions to the optic nerve at site A?
What happens during lesions to the optic nerve at site A?
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Why is it necessary to cover one eye during visual field testing?
Why is it necessary to cover one eye during visual field testing?
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In which region of the retina is the highest density of cone receptors found?
In which region of the retina is the highest density of cone receptors found?
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What type of visual deficit results from a large lesion at the optic chiasm?
What type of visual deficit results from a large lesion at the optic chiasm?
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What is the role of the lateral geniculate nucleus in the visual pathway?
What is the role of the lateral geniculate nucleus in the visual pathway?
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What occurs when light enters the eye?
What occurs when light enters the eye?
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What is the primary input pathway into the cerebellum?
What is the primary input pathway into the cerebellum?
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What is the purpose of the double H pattern test?
What is the purpose of the double H pattern test?
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What would be an indication of cerebellar dysfunction during the finger-nose test?
What would be an indication of cerebellar dysfunction during the finger-nose test?
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During the smooth pursuit examination, which of the following movements should be avoided to prevent inducing nystagmus?
During the smooth pursuit examination, which of the following movements should be avoided to prevent inducing nystagmus?
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How does one assess rebound during upper limb testing?
How does one assess rebound during upper limb testing?
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What is the expected finding in a patient with cerebellar dysfunction during the rapid movement test for dysdiadochokinesia?
What is the expected finding in a patient with cerebellar dysfunction during the rapid movement test for dysdiadochokinesia?
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What characterizes scanning speech in a patient with cerebellar dysfunction?
What characterizes scanning speech in a patient with cerebellar dysfunction?
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What is one of the physiological roles of the cerebellum concerning eye movement?
What is one of the physiological roles of the cerebellum concerning eye movement?
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Which test involves a clinician pulling on the patient's arm to assess response?
Which test involves a clinician pulling on the patient's arm to assess response?
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What is an expected result if a patient demonstrates intention tremor during movement?
What is an expected result if a patient demonstrates intention tremor during movement?
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What does the presence of nystagmus generally indicate?
What does the presence of nystagmus generally indicate?
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What indicates a potential damage to the optic nerve when both pupils remain dilated upon shining light in one eye?
What indicates a potential damage to the optic nerve when both pupils remain dilated upon shining light in one eye?
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Which structure is primarily responsible for the bilateral response in pupil constriction?
Which structure is primarily responsible for the bilateral response in pupil constriction?
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What role does the visual association cortex play in the accommodation reflex?
What role does the visual association cortex play in the accommodation reflex?
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Which part of the cerebellum is primarily involved in midline functions, such as trunk control?
Which part of the cerebellum is primarily involved in midline functions, such as trunk control?
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Which pathway primarily carries proprioceptive information from the spinal cord to the ipsilateral side of the cerebellum?
Which pathway primarily carries proprioceptive information from the spinal cord to the ipsilateral side of the cerebellum?
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What is the primary function of the inferior olivary nucleus concerning the cerebellum?
What is the primary function of the inferior olivary nucleus concerning the cerebellum?
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Which type of neurons project down through the corticospinal tract to influence movements on the opposite side of the body?
Which type of neurons project down through the corticospinal tract to influence movements on the opposite side of the body?
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Which component of the accommodation reflex arc is responsible for controlling pupillary sphincter and ciliary muscle contraction?
Which component of the accommodation reflex arc is responsible for controlling pupillary sphincter and ciliary muscle contraction?
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What is the main role of the vestibulocerebellum?
What is the main role of the vestibulocerebellum?
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Which structure receives input from both the spinal cord and cerebral cortex?
Which structure receives input from both the spinal cord and cerebral cortex?
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Which nucleus is specifically associated with the pupillary light reflex?
Which nucleus is specifically associated with the pupillary light reflex?
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What describes the primary location of the trunk representation in the cerebellum?
What describes the primary location of the trunk representation in the cerebellum?
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Which neural pathway is responsible for conveying integrated sensory information to the contralateral side of the cerebellum?
Which neural pathway is responsible for conveying integrated sensory information to the contralateral side of the cerebellum?
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What differentiates the cerebrocerebellum from the other regions of the cerebellum?
What differentiates the cerebrocerebellum from the other regions of the cerebellum?
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What is the primary function of the flocculonodular lobe of the cerebellum?
What is the primary function of the flocculonodular lobe of the cerebellum?
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How does the cerebellum primarily influence eye movements?
How does the cerebellum primarily influence eye movements?
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What effect would damage to the flocculonodular lobe likely have?
What effect would damage to the flocculonodular lobe likely have?
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Which cerebellar peduncle is primarily responsible for sending outputs from the cerebellum to the cortex?
Which cerebellar peduncle is primarily responsible for sending outputs from the cerebellum to the cortex?
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Which nucleus is primarily involved in postural regulation within the cerebellum?
Which nucleus is primarily involved in postural regulation within the cerebellum?
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What is the significance of the vestibular apparatus in the cerebellum's function?
What is the significance of the vestibular apparatus in the cerebellum's function?
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Where does the cerebellum primarily receive inputs for processing eye movements?
Where does the cerebellum primarily receive inputs for processing eye movements?
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What role does the interposed nucleus serve in the cerebellar function?
What role does the interposed nucleus serve in the cerebellar function?
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What is nystagmus and how is it related to cerebellar function?
What is nystagmus and how is it related to cerebellar function?
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What movement does the cerebellum help regulate to allow for smooth pursuit in vision?
What movement does the cerebellum help regulate to allow for smooth pursuit in vision?
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Which aspect of the cerebellum's anatomy is most complex concerning input and output?
Which aspect of the cerebellum's anatomy is most complex concerning input and output?
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What type of eye movements can indicate a cerebellar injury during examination?
What type of eye movements can indicate a cerebellar injury during examination?
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Which area of the cerebellum primarily processes information related to motor planning?
Which area of the cerebellum primarily processes information related to motor planning?
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What pathway conveys input from the cortex to the cerebellum?
What pathway conveys input from the cortex to the cerebellum?
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Which sinus runs in a sagittal direction and terminates at the confluence of sinuses?
Which sinus runs in a sagittal direction and terminates at the confluence of sinuses?
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What is significant about the falx cerebri during skull injuries?
What is significant about the falx cerebri during skull injuries?
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Which blood vessel is commonly associated with epidural hematomas?
Which blood vessel is commonly associated with epidural hematomas?
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What type of MRI scan shows CSF as bright?
What type of MRI scan shows CSF as bright?
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What is the shape of an extradural hematoma when viewed on imaging?
What is the shape of an extradural hematoma when viewed on imaging?
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Which structure separates the cerebellum from the cerebrum?
Which structure separates the cerebellum from the cerebrum?
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Subdural hematomas are most commonly caused by the tearing of which structures?
Subdural hematomas are most commonly caused by the tearing of which structures?
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What happens to the right lateral ventricle when midline shift is present?
What happens to the right lateral ventricle when midline shift is present?
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Which of the following sinuses is NOT primarily associated with the confluence of sinuses?
Which of the following sinuses is NOT primarily associated with the confluence of sinuses?
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What characteristic distinguishes white matter from gray matter?
What characteristic distinguishes white matter from gray matter?
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During an injury, what can push on the brain tissue?
During an injury, what can push on the brain tissue?
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Which of the following structures helps connect both hemispheres of the brain?
Which of the following structures helps connect both hemispheres of the brain?
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In a T1 MRI scan, how is white matter typically represented?
In a T1 MRI scan, how is white matter typically represented?
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What is the primary function of the dorsal root ganglion?
What is the primary function of the dorsal root ganglion?
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Which ganglion typically receives signals from sympathetic motor neurons?
Which ganglion typically receives signals from sympathetic motor neurons?
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What is the primary role of the cerebellum in relation to the cortex?
What is the primary role of the cerebellum in relation to the cortex?
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Where does sensory information related to light touch and proprioception ascend to after bypassing the grey matter?
Where does sensory information related to light touch and proprioception ascend to after bypassing the grey matter?
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What anatomical feature is used to identify cervical vertebrae?
What anatomical feature is used to identify cervical vertebrae?
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Which test is specifically used to identify cerebellar dysfunction through coordination?
Which test is specifically used to identify cerebellar dysfunction through coordination?
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What occurs as a result of narrowing of the intervertebral foramina?
What occurs as a result of narrowing of the intervertebral foramina?
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What type of muscle tone abnormalities might indicate cerebellar disease?
What type of muscle tone abnormalities might indicate cerebellar disease?
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Why does the Romberg test NOT specifically assess cerebellar function?
Why does the Romberg test NOT specifically assess cerebellar function?
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What does the dura mater primarily assist with in the cranial cavity?
What does the dura mater primarily assist with in the cranial cavity?
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What is the function of the ventral root in relation to the spinal cord?
What is the function of the ventral root in relation to the spinal cord?
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What anatomical areas are involved in maintaining normal stance during the Romberg test?
What anatomical areas are involved in maintaining normal stance during the Romberg test?
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Which structure is responsible for conveying information about pain and temperature sensation?
Which structure is responsible for conveying information about pain and temperature sensation?
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Which area of the spinal cord contains the motor neurons responsible for innervating striated skeletal muscles?
Which area of the spinal cord contains the motor neurons responsible for innervating striated skeletal muscles?
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What is the primary function of the dorsal columns in the spinal cord?
What is the primary function of the dorsal columns in the spinal cord?
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What is the primary role of the anterior rami after leaving the spinal nerve?
What is the primary role of the anterior rami after leaving the spinal nerve?
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What characteristic might indicate cerebellar dysfunction during gait testing?
What characteristic might indicate cerebellar dysfunction during gait testing?
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Which of the following is NOT a key characteristic of the dura mater?
Which of the following is NOT a key characteristic of the dura mater?
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Which neuronal structure is primarily responsible for the white color of white matter in the spinal cord?
Which neuronal structure is primarily responsible for the white color of white matter in the spinal cord?
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What is a common result of spondylosis in the cervical region?
What is a common result of spondylosis in the cervical region?
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Visceral afferents are responsible for conveying which type of information?
Visceral afferents are responsible for conveying which type of information?
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Where are preganglionic autonomic motor neurons located in the spinal cord?
Where are preganglionic autonomic motor neurons located in the spinal cord?
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How do pain and temperature sensory fibers project their information after synapsing in the dorsal root ganglion?
How do pain and temperature sensory fibers project their information after synapsing in the dorsal root ganglion?
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Which component of white matter carries signals from the brain to the spinal cord for voluntary movement?
Which component of white matter carries signals from the brain to the spinal cord for voluntary movement?
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With what kind of movements might a patient with elevated muscle tone present?
With what kind of movements might a patient with elevated muscle tone present?
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What tissue lies between the dura mater and the inner lining of the cranial cavity?
What tissue lies between the dura mater and the inner lining of the cranial cavity?
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Which sensory modalities are primarily conveyed by the dorsal column pathway?
Which sensory modalities are primarily conveyed by the dorsal column pathway?
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What might be a consequence of damage to the flocculonodular lobe?
What might be a consequence of damage to the flocculonodular lobe?
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What type of neuron conveys noxious pain and temperature information from the skin of the T1 dermatome?
What type of neuron conveys noxious pain and temperature information from the skin of the T1 dermatome?
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Where does the first synapse occur for the ascending spinothalamic pathway?
Where does the first synapse occur for the ascending spinothalamic pathway?
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Which part of the spinal cord is affected by a Brown-Sequard syndrome lesion at the L3 level?
Which part of the spinal cord is affected by a Brown-Sequard syndrome lesion at the L3 level?
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What is the primary ascending pathway responsible for pain and temperature sensation?
What is the primary ascending pathway responsible for pain and temperature sensation?
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Which type of reflex arc involves motor activity occurring at the spinal level without brain involvement?
Which type of reflex arc involves motor activity occurring at the spinal level without brain involvement?
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In the context of a spinal cord hemisection, which modality is expected to be lost contralaterally?
In the context of a spinal cord hemisection, which modality is expected to be lost contralaterally?
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What outcome is expected after a lesion to the upper motor neuron?
What outcome is expected after a lesion to the upper motor neuron?
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What is the correct anatomical location for performing a lumbar puncture?
What is the correct anatomical location for performing a lumbar puncture?
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At what anatomical location does the decussation of the lateral corticospinal tract occur?
At what anatomical location does the decussation of the lateral corticospinal tract occur?
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Which structures may be affected by septic thrombosis of the cavernous sinus?
Which structures may be affected by septic thrombosis of the cavernous sinus?
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In the event of a tentorial herniation, which structure is likely to herniate through the tentorial notch?
In the event of a tentorial herniation, which structure is likely to herniate through the tentorial notch?
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Which part of the brain is likely affected if a patient exhibits motor and sensory loss on the right side of the body?
Which part of the brain is likely affected if a patient exhibits motor and sensory loss on the right side of the body?
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What pathway do sympathetic motor neurons take to reach the heart?
What pathway do sympathetic motor neurons take to reach the heart?
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Where do the visceral sensory afferents of the heart synapse in the central nervous system?
Where do the visceral sensory afferents of the heart synapse in the central nervous system?
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What type of disability would arise from a lesion in the primary motor cortex that affects hand movement?
What type of disability would arise from a lesion in the primary motor cortex that affects hand movement?
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Which nerve is primarily responsible for the parasympathetic innervation to the heart?
Which nerve is primarily responsible for the parasympathetic innervation to the heart?
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In the context of the heart, which receptors do postganglionic sympathetic neurons primarily act on?
In the context of the heart, which receptors do postganglionic sympathetic neurons primarily act on?
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What does the lateral sulcus separate?
What does the lateral sulcus separate?
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Which lobe contains the cingulate gyrus?
Which lobe contains the cingulate gyrus?
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What is the name of the sulcus that is on the superior margin of the cingulate gyrus?
What is the name of the sulcus that is on the superior margin of the cingulate gyrus?
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What is the main function associated with the precentral gyrus?
What is the main function associated with the precentral gyrus?
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What sulcus separates the occipital lobe from the wedge-shaped area known as the cuneus?
What sulcus separates the occipital lobe from the wedge-shaped area known as the cuneus?
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What is a key function of the parietal lobe?
What is a key function of the parietal lobe?
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Where do sensory fibers enter the spinal cord?
Where do sensory fibers enter the spinal cord?
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What marks the termination of the spinal cord?
What marks the termination of the spinal cord?
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What areas are particularly susceptible to ischaemia due to limited collateral circulation?
What areas are particularly susceptible to ischaemia due to limited collateral circulation?
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Which artery is primarily responsible for supplying the anterior two-thirds of the spinal cord?
Which artery is primarily responsible for supplying the anterior two-thirds of the spinal cord?
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What characterizes symptoms following a hemisection of the spinal cord?
What characterizes symptoms following a hemisection of the spinal cord?
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What is a common purpose of performing a lumbar puncture?
What is a common purpose of performing a lumbar puncture?
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What is the primary shape of subdural haematomas as a result of their anatomical characteristics?
What is the primary shape of subdural haematomas as a result of their anatomical characteristics?
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Which structure limits the extent of subdural haematomas?
Which structure limits the extent of subdural haematomas?
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In a T2 weighted MRI image, which substance appears hyperintense compared to other tissues?
In a T2 weighted MRI image, which substance appears hyperintense compared to other tissues?
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What is the likely consequence of a herniated disc in the lumbosacral region?
What is the likely consequence of a herniated disc in the lumbosacral region?
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What type of paralysis occurs below the level of a complete spinal cord transection?
What type of paralysis occurs below the level of a complete spinal cord transection?
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What is one of the defining features of an anterior cord infarct?
What is one of the defining features of an anterior cord infarct?
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Which dural venous sinus is located along the inferior margin of the falx cerebri?
Which dural venous sinus is located along the inferior margin of the falx cerebri?
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What is the role of arachnoid granulations within the dural venous sinuses?
What is the role of arachnoid granulations within the dural venous sinuses?
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Which part of the spinal cord is particularly affected in a complete cord transection?
Which part of the spinal cord is particularly affected in a complete cord transection?
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What characterizes bilateral upper motor neuron lesions below the level of an anterior cord infarct?
What characterizes bilateral upper motor neuron lesions below the level of an anterior cord infarct?
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Which sinus is known as the confluence of sinuses?
Which sinus is known as the confluence of sinuses?
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Which area of the brain is affected by a long segment of increased T2 signal indicating an anterior cord infarct?
Which area of the brain is affected by a long segment of increased T2 signal indicating an anterior cord infarct?
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What causes complete paralysis of the diaphragm if the spinal cord is transected above the C4 level?
What causes complete paralysis of the diaphragm if the spinal cord is transected above the C4 level?
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What structure separates the two cerebral hemispheres?
What structure separates the two cerebral hemispheres?
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Study Notes
Cerebellum Anatomy
- The cerebellum is situated in the posterior cranial fossa, separated from the cerebrum by the tentorium cerebelli.
- The cerebellum is divided into two hemispheres by a deep groove on the underside, with a midline mass of tissue called the vermis.
- The cerebellar peduncles, composed of white matter, connect the cerebellum to the brainstem, transmitting information from the spinal cord, brainstem, and major nuclei in the pons.
Cerebellar Peduncles
- Superior: Major output arm of the cerebellum, with minor spinal input.
- Inferior: Receives input from the spinal cord and medulla, particularly the olivary complex.
- Middle: Continuous with the pons, receives major input from the cortex through cortical fibers.
Cerebellar Nuclei
- Dentate: Located posterolaterally, involved in motor coordination and planning.
- Interposed nuclei: (globose and embiliform) Medially located, involved in limb movement coordination.
- Fastigial: Most medially located, involved in trunk and posture control.
Visual Pathway
- Retina: 100 million neurons, light travels through the layers, exciting photoreceptors and transmitting signals to the ganglion cells.
- Optic Nerve: Carries axons of ganglion cells from the retina to the brain.
- Optic Chiasm: Where fibers from the nasal side of the retina cross to the contralateral side, while fibers from the temporal side remain ipsilateral.
- Lateral Geniculate Nucleus: Relay station in the thalamus where visual information is processed.
- Optic Radiation: Fibers from the LGN project to the visual cortex.
- Visual Cortex: Processes visual information, located in the occipital lobe.
Types of Visual Field Defects
- Complete Blindness (Ipsilateral eye): Lesion to the optic nerve.
- Nasal Hemianopia (Ipsilateral eye): Lesion to the nasal part of the retina.
- Bitemporal Hemianopia (Tunnel Vision): Lesion to the middle of the optic chiasm, often associated with pituitary gland tumours.
- Contralateral Homonymous Hemianopia: Lesion to the optic tract or visual cortex, affecting the same half of the visual field in both eyes.
- Quadrantanopia: Loss of a quarter of the visual field, often due to a lesion in the optic radiation.
- Macular Sparing: Indicates a lesion in the visual cortex, sparing central vision.
Pupillary Reflex
- Afferent Pathway: Optic nerve.
- CNS Relay: Pretectal area of the midbrain.
- Efferent Pathway: Bilateral oculomotor nerve (CN III).
- Ciliary Ganglion: Postganglionic fibers from the EW nucleus synapse here and innervate the ciliary muscle.
- Pupillary Constriction: Stimulated by increased light levels, the ciliary muscle contracts.
Accommodation Reflex
- Afferent Pathway: Optic nerve.
- CNS Relay: Lateral geniculate nucleus and visual association cortex.
- Efferent Pathway: Oculomotor nerve (CN III).
- Accommodation: Adjusting the lens to focus on objects at different distances.
Cerebellar Inputs and Outputs
- Spinocerebellum (Vermis): Involved in trunk and posture control, receives input from the spinal cord.
- Cerebrocerebellum (Lateral hemispheres): Involved in limb and hand movements, receives input from the cerebral cortex.
- Vestibulocerebellum (Flocculus and Nodulus): Involved in balance and coordination of eye movements, receives input from the vestibular system.
Cerebellar Mapping
- Spinocerebellum: Midline structures control the trunk, lateral structures control limbs.
- Corticocerebellum: Different cortical areas project to specific regions of the cerebellum, controlling movement on the contralateral side of the body.
- Inferior Olivary Nucleus: Complex processing center, involved in motor learning and coordination.
Spinal Cord Anatomy
- The spinal cord is composed of two substances: white matter (containing axons) and gray matter (containing neurons).
- The gray matter is arranged in a specific manner:
- Dorsal horn: Contains projection neurons that convey sensory information to the brainstem.
- Ventral horn: Contains motor neurons that innervate skeletal muscle.
- Lateral horn: Present from T1-L2, contains preganglionic autonomic motor neurons.
- The white matter contains axons connecting the brain and spinal cord:
- Dorsal columns: Axons sending sensory information (light touch and proprioception) to the brainstem.
- Lateral white matter: Contains the corticospinal tract, connecting the brain to the spinal cord.
- Ventral white matter: Contains axons leaving the spinal cord and ascending to the thalamus.
Spinal Cord Information Flow
- Sensory information enters the spinal cord through the dorsal roots and travels up the dorsal columns towards the brainstem.
- Motor information exits the spinal cord through the ventral roots and travels to skeletal muscles.
- Autonomic information exits the spinal cord through the ventral roots along with skeletal motor neurons.
- Sensory information from the dorsal horn (sensory afferents) ascends through the spinothalamic tract to the thalamus.
- Motor information from the cortex descends through the corticospinal tract to the ventral horn.
Spinal Cord Structure
- Dorsal and ventral roots are bundles of axons that connect the spinal cord to the periphery.
- Blood vessels enter the spinal cord through longitudinal fissures and circle around the outside.
- Deep impressions within the white matter may contain blood vessels.
- Myelin, produced by oligodendrocytes, insulates the axons in the white matter, giving it a white color.
- Interneurons connect neurons within the spinal cord, facilitating communication between different parts of the nervous system.
Ventral/Lateral Horn Motor Neurons
- Motor neurons in the ventral/lateral horns of the spinal cord send their axons via ventral rootlets, joining sensory fibers in the mixed spinal nerve.
- Motor neurons directly innervating skeletal muscle send their fibers directly to the muscle.
- Autonomic motor neurons travel through the mixed spinal nerve to a ganglion.
- Sympathetic nerves typically target paravertebral ganglia (T1-L2).
- Parasympathetic ganglia from the sacral region and brainstem target smaller ganglia within tissues.
Sensory Information
- Sensory information about touch, stretch, and chemosensation is conveyed by sensory fibers.
- All sensory fibers travel through the dorsal root, with their cell bodies located in the dorsal root ganglion.
- Sensory afferents from the dorsal root ganglion project to the dorsal horn or travel up the dorsal columns.
- Pain and temperature sensation synapse in the DRG onto projection neurons, which send information to the contralateral side via the ventral white matter.
- Light touch and proprioception bypass the gray matter, travel directly into the dorsal columns, and ascend to the brainstem for their first connection.
Visceral Afferents
- Visceral afferents convey sensory information from organs like the heart and gut, where localization is less precise, and are important for autonomic reflexes.
- They send information via the dorsal horn, with cell bodies in the dorsal root ganglion, and project onto the dorsal aspect of the gray matter.
Intervertebral Foramina
- The mixed spinal nerve sits between stacked vertebrae, in the intervertebral foramina.
- Cervical vertebrae have characteristic features, including a bifid spinous process, space for the vertebral artery, obliquely oriented zygopophyseal articular surfaces, and uncinate processes.
- The dorsal root ganglion, a swelling containing sensory neuron cell bodies, projects from the dorsal root in the intervertebral foramina.
- The dura mater, the outermost covering of the spinal cord, lies externally.
- The arachnoid mater lies between the dura mater and the internal lining.
Anatomical Relationships and Potential for Injury
- Nerve roots converge to form the mixed spinal nerve near the dorsal root ganglion, within the intervertebral foramina, making them susceptible to injury in cases of bone damage.
- The vertebral artery travels through the cervical vertebrae.
- The intervertebral foramina is the exit point for spinal nerves except in the sacrum.
- Spinal nerves, upon exiting the intervertebral foramina, divide into ventral and dorsal roots.
- The dorsal root ganglion is located in the intervertebral space, with axons projecting to the dorsal horn or dorsal columns.
Spinal Nerve Ramifications
- The anterior rami of spinal nerves supply the limbs and anterior side of the body, potentially forming plexuses.
- The posterior rami of spinal nerves innervate the intrinsic muscles of the back, including the erector spinae, deeper muscles, and skin overlying the back.
Intervertebral Foramina Stenosis
- Narrowing of the intervertebral foramina can cause neurological symptoms.
- Spondylosis, the sliding of vertebrae on each other, can contribute to narrowing.
- Stenosis, particularly in the cervical region, can compress the spinal nerve, causing nerve-related symptoms.
Dura Mater and Dural Venous Sinuses
- The dura mater is arranged in folds within the cranial cavity, including the falx cerebri and the tentorium cerebelli.
- Dural venous sinuses are found within the dural folds and serve as conduits for venous return from the brain.
- Major dural venous sinuses include the superior sagittal sinus, inferior sagittal sinus, straight sinus, transverse sinus, sigmoid sinus, and cavernous sinus.
- The rigid structure of the dural venous sinuses prevents backflow of blood due to siphoning action.
Injuries to the Skull
- Injuries to the skull can cause bleeding, separating the dura mater from bony tissue and potentially leading to brain shift.
- Midline shift of the falx cerebri or brain tissue herniation into the opposite hemisphere indicates potential brain displacement.
Cisterns of the Brain
- Cisterns are areas within the brain where cerebrospinal fluid (CSF) pools.
Cerebral Cortex and Important Structures
- The primary somatosensory cortex is located just posterior to the central sulcus.
- The primary motor cortex is located anterior to the primary somatosensory cortex.
- The central sulcus divides the frontal and parietal lobes.
- Other important cortical structures include the calcarine sulcus, collateral sulcus, cingulate gyrus, and paraoccipital fissure.
Anatomical Relationship of Blood Vessel
- The middle meningeal artery is located near the pterion, a bony landmark formed by the frontal, parietal, temporal, and sphenoid bones.
Meninges
- The falx cerebri is a dural fold separating the cerebral hemispheres.
- The tentorium cerebelli is a tent-like structure separating the cerebellum from the cerebrum.
MRI Imaging
- T1-weighted MRI images show CSF as dark, white matter as light, gray matter as grey, fat as bright, and inflammation as dark.
- T2-weighted MRI images show CSF as bright, white matter as dark grey, grey matter as light grey, fat as light, and inflammation as bright.
- Axial, sagittal, and coronal sections are commonly used in MRI imaging.
Lobes of the Brain
- The frontal lobe, parietal lobe, temporal lobe, occipital lobe, and cerebellum are visible in MRI scans.
- The longitudinal fissure separates the cerebral hemispheres.
- The corpus callosum connects both hemispheres.
Structures Identified on T1 MRI
- The spinal cord, medulla, pons, genu of the corpus callosum, cerebellum, hypothalamus, and splenium of the corpus callosum can be identified on T1 MRI.
Structures Identified on MRI
- The thalamus, hypothalamus, and pituitary gland can be identified on MRI.
Pathologies Identified on CT Scans
- Epidural hematomas are usually biconvex in shape and hyperdense on CT scans.
- Subdural hematomas are crescent-shaped and hypodense on CT scans.
- Subarachnoid hemorrhages show hyperdense material within the subarachnoid space, often extending into the ventricles.
Disc Herniation
- Disc herniation occurs when the nucleus pulposus protrudes beyond the confines of the intervertebral disc, compressing the nerve in the intervertebral foramina.
- The intervertebral foramina narrowing can lead to lower back pain, shooting pain, sensory deficits, and weakness in the lower leg.
- Nerve roots immediately below a lumbar disc prolapse are particularly vulnerable to compression.
Spinal Cord Transection and Infarct
- Spinal cord transection, often resulting from trauma, can cause complete loss of motor function and sensory perception below the lesion, with preservation above.
- Anterior cord infarct, commonly occurring in the thoracic region, results in bilateral lower motor neuron lesions at the level of the infarct, bilateral upper motor neuron lesions below the infarct, and bilateral loss of cutaneous sensation below the infarct.
- Proprioception and discriminative tactile sensation are typically preserved in anterior cord infarcts.
Dural Venous Sinus Functions and Arachnoid Granulations
- Dural venous sinuses contain protrusions of arachnoid mater called arachnoid granulations.
- Arachnoid granulations allow CSF to flow into the venous sinuses, preventing blood from flowing back into the subarachnoid space.
- These granulations contribute to CSF pressure regulation, filtering, and removal of waste products from the central nervous system.
Cerebral Fissures and Gyri
- The median longitudinal fissure (interhemispheric fissure) separates the left and right cerebral hemispheres.
- The lateral sulcus (Sylvian fissure) separates the temporal lobe from the frontal and parietal lobes.
- The insula is a lobe hidden beneath the temporal lobe in the depths of the lateral sulcus.
- The cingulate gyrus lies superior to the corpus callosum and is part of the limbic lobe.
- The cingulate sulcus forms the superior margin of the cingulate gyrus.
- The central sulcus (fissure of Rolando) is located just anterior to the sharp turn of the cingulate sulcus. ### The Cerebrum
- The precentral gyrus is anterior to the central sulcus and is associated with motor function.
- The postcentral gyrus is posterior to the central sulcus and is associated with somatosensory function.
- The parieto-occipital sulcus separates the cuneus, a wedge-shaped area of the occipital lobe, from the rest of the cerebrum.
Lobes of the Brain and Functions
- Frontal Lobe: Executive functions, motor planning, speech production, emotional regulation, personality, working memory.
- Parietal Lobe: Sensory integration, spatial awareness, language processing, attention, mathematical reasoning.
- Temporal Lobe: Auditory processing, memory formation, language comprehension, emotion processing, visual recognition.
- Occipital Lobe: Visual processing, color recognition, motion perception, visual association.
- Insula: Interoception, emotional awareness, taste processing, pain perception, empathy, social cognition.
Spinal Cord Anatomy
- Rhizotomy: Surgical destruction of nerve fibers to relieve intractable pain.
- Dorsal Root: Sensory fibers enter the spinal cord.
- Ventral Root: Motor fibers exit the spinal cord.
- Conus Medullaris: Tapered end of the spinal cord, typically terminating at the L1-2 vertebral levels.
- Cauda Equina: Bundle of nerve roots below the conus medullaris, resembling a horse's tail.
Spinal Cord Arterial Supply
- Anterior Spinal Artery: Single midline vessel supplying the anterior two-thirds of the cord.
- Paired Posterior Spinal Arteries: Supply the posterior one-third of the cord.
- Radicular Arteries: Branch from segmental arteries and reinforce the longitudinal spinal arteries.
- Artery of Adamkiewicz: Major reinforcing radicular artery, usually arising on the left side between T9 and L2. Damage to this artery can cause significant ischaemia of the lower spinal cord.
Spinal Cord Vulnerability
- Limited collateral circulation: Few anastomoses between anterior and posterior spinal arteries.
- Variable reinforcement: Number of radicular arteries varies between individuals and spinal levels.
- Watershed zones: Areas between territories supplied by different arteries are susceptible to ischaemia.
- Long length of anterior/posterior spinal arteries: Makes them prone to pathological processes.
Brown-Sequard Syndrome
- Ipsilateral Loss of Motor Function: Below the level of the lesion.
- Ipsilateral Loss of Sensation: Below the level of the lesion.
- Contralateral Loss of Pain and Temperature: Below the level of the lesion.
Lumbar Puncture
- Procedure: Performed with the patient flexing their vertebral column to stretch the ligamentum flavum.
- Location: Between the L4 and L5 spinous processes.
- Two "pops" from the needle: One through the ligamentum flavum, one through the dura mater.
Lesion Location and Function
- Right arm and leg paralysis and sensory loss: Contralateral lesion potentially affecting the parietal lobe, likely around the central sulcus.
Cavernous Sinus Structures
- Structures within the Cavernous Sinus: Internal carotid artery, carotid plexus, oculomotor, trochlear, ophthalmic, maxillary and abducens nerves.
Tentorial Notch
- Location: Opening into the tentorium cerebelli for the brainstem.
- Structure within the notch: The midbrain.
- Tentorial herniation: Raised intracranial pressure can cause the uncus of the temporal lobe to herniate through the tentorial notch, compressing the midbrain.
Autonomic Nervous System - Heart
- Sympathetic: Preganglionic neurons originate in the lateral horn of the spinal cord, travel via white rami communicans to the sympathetic trunk. Postganglionic neurons travel from the sympathetic trunk to the heart, acting on beta 1 receptors to increase conductivity and contraction.
- Parasympathetic: Vagus Nerve. Preganglionic neurons originate in the medulla of the brain, travel close to the heart where they synapse on postganglionic neurons, innervating the SA and AV nodes of the heart.
Visceral Sensory Afferents - Heart
- Sympathetic: Travel with cardiac nerves, join the spinal cord at dorsal roots of T1-T5, follow the sympathetic trunk to the cortex, causing ‘referred pain’ to the chest.
- Parasympathetic: Travel with the vagus nerve and synapse at the nucleus tractus solitarius in the brainstem.
### Motor Neuron Pathway - Right Hand
- Descending Pathway (Motor): Lateral corticospinal tract.
- Path: Passes through the internal capsule, white matter of the spinal cord, decussates in the medullary pyramid and synapses with motor neurons in the ventral horn to innervate the left hand.
Sensory Neuron Pathway - Right Hand - Pain & Temperature
- Ascending Pathway (Sensory): Spinothalamic tract (lateral).
- Path: First-order neuron travels in the dorsal column, decussates in the spinal cord, then travels through the spinothalamic tract, synapsing in the thalamus, before the third-order neuron projects to the primary sensory cortex.
Sensory Neuron Pathway - T1 Dermatome - Pain & Temperature
- Ascending Pathway (Sensory): Spinothalamic tract (lateral).
- Path: First-order neuron travels in the dorsal column, decussates in the spinal cord, then travels through the spinothalamic tract, synapsing in the thalamus, before the third-order neuron projects to the primary sensory cortex.
Reflex Arc
- Upper Motor Neuron Lesion: Decreased power but increased tendon jerk reflex.
- Reflex Arc Components: Afferent, relay, and efferent neurons.
- Example Reflex: Biceps reflex (C5-C6), Brachioradialis reflex (C6), Triceps reflex (C7-C8), Knee jerk reflex (L2-L4), Achilles reflex (S1-S2).
Brown-Sequard Syndrome - Left Side
-
Hemisecion of the spinal cord:
- Ipsilateral loss of motor function below the level of the lesion (corticospinal tract).
- Ipsilateral loss of sensation below the level of the lesion (DCML).
- Contralateral loss of pain and temperature sensation below the level of the lesion (spinothalamic tract).
Brown-Sequard Syndrome - Explanation
- Hemisection of the Spinal Cord: Transection of one half of the spinal cord, often seen in trauma.
-
Consequences at the Level of the Lesion:
- Flaccid Paralysis: Lower motor neuron lesion with loss of all senses.
- Loss of Specific Myotomes: Loss of muscle function specific to the affected spinal level.
-
Consequences Below the Level of the Lesion:
- Spastic Paralysis: Upper motor neuron lesion (corticospinal tract).
- Ipsilateral loss of fine/crude touch: Damage to the dorsal column - medial lemniscus (DCML) pathway.
- Contralateral loss of pain and temperature sensation: Damage to the contralateral spinothalamic tract.
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