Podcast
Questions and Answers
What are the primary functions of dendrites in a neuron?
What are the primary functions of dendrites in a neuron?
Which part of the neuron is primarily responsible for conducting information to other neurons?
Which part of the neuron is primarily responsible for conducting information to other neurons?
In the structure of a typical neuron, what is the role of axon terminals?
In the structure of a typical neuron, what is the role of axon terminals?
What structure primarily covers the axon and is involved in the conduction speed of electrical signals?
What structure primarily covers the axon and is involved in the conduction speed of electrical signals?
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Which statement correctly describes the soma (cell body) of a neuron?
Which statement correctly describes the soma (cell body) of a neuron?
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How does synaptic input predominantly occur in a neuron?
How does synaptic input predominantly occur in a neuron?
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What major organelles are typically found in the soma of a neuron?
What major organelles are typically found in the soma of a neuron?
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Which section of the central nervous system features the highest number markings from the provided illustration?
Which section of the central nervous system features the highest number markings from the provided illustration?
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What structure is primarily responsible for producing cerebrospinal fluid (CSF) in the brain?
What structure is primarily responsible for producing cerebrospinal fluid (CSF) in the brain?
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Which ventricle does the cerebrospinal fluid (CSF) flow into after passing through the interventricular foramen?
Which ventricle does the cerebrospinal fluid (CSF) flow into after passing through the interventricular foramen?
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What is the name of the space located below the meningeal layer of the dura mater?
What is the name of the space located below the meningeal layer of the dura mater?
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Which structure connects the third ventricle to the fourth ventricle?
Which structure connects the third ventricle to the fourth ventricle?
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What are the two layers of the dura mater called?
What are the two layers of the dura mater called?
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What is the term for the potential space that can fill with blood during vascular trauma, situated superficially to the periosteal layer?
What is the term for the potential space that can fill with blood during vascular trauma, situated superficially to the periosteal layer?
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Which structure forms the boundary between the right and left cerebral hemispheres?
Which structure forms the boundary between the right and left cerebral hemispheres?
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Which structure sends cerebrospinal fluid out of the ventricular system into the subarachnoid space?
Which structure sends cerebrospinal fluid out of the ventricular system into the subarachnoid space?
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What type of cells line most of the ventricles and are responsible for CSF production?
What type of cells line most of the ventricles and are responsible for CSF production?
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What is the primary function of the myelin sheath surrounding the axon?
What is the primary function of the myelin sheath surrounding the axon?
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Which anatomical structure separates the frontal lobe from the parietal lobe?
Which anatomical structure separates the frontal lobe from the parietal lobe?
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Where does the body of the lateral ventricles connect with the posterior and inferior horns?
Where does the body of the lateral ventricles connect with the posterior and inferior horns?
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What is the primary function of the meninges surrounding the central nervous system?
What is the primary function of the meninges surrounding the central nervous system?
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What is the role of the corpus callosum in the brain?
What is the role of the corpus callosum in the brain?
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Which structure is found beneath the gray matter of the cortical surface?
Which structure is found beneath the gray matter of the cortical surface?
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What distinguishes the falx cerebelli from other dural reflections?
What distinguishes the falx cerebelli from other dural reflections?
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The fourth ventricle is bordered by which structures?
The fourth ventricle is bordered by which structures?
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The somatic nervous system is primarily responsible for which of the following functions?
The somatic nervous system is primarily responsible for which of the following functions?
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Which of the following best describes the grey matter of the cerebrum?
Which of the following best describes the grey matter of the cerebrum?
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What separates the temporal lobe from the frontal lobe?
What separates the temporal lobe from the frontal lobe?
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What are gyri and sulci responsible for in the cerebral hemispheres?
What are gyri and sulci responsible for in the cerebral hemispheres?
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What is the primary role of the visceral nervous system?
What is the primary role of the visceral nervous system?
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In the central nervous system, where is white matter predominantly located?
In the central nervous system, where is white matter predominantly located?
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Which of the following correctly identifies parts of the internal capsule?
Which of the following correctly identifies parts of the internal capsule?
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What structure is referred to as the operculum in the cerebral cortex?
What structure is referred to as the operculum in the cerebral cortex?
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Which portion of the lateral ventricles is located in the frontal lobe?
Which portion of the lateral ventricles is located in the frontal lobe?
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What structure serves as the synaptic relay for pathways projecting to the cerebral cortex?
What structure serves as the synaptic relay for pathways projecting to the cerebral cortex?
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Which veins primarily receive drainage from superficial veins?
Which veins primarily receive drainage from superficial veins?
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Which of the following is NOT mentioned as a branch from the posterior cerebral artery?
Which of the following is NOT mentioned as a branch from the posterior cerebral artery?
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What is the role of the interthalamic adhesion?
What is the role of the interthalamic adhesion?
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Which vein courses superiorly across the parietal lobe to drain into the superior sagittal sinus?
Which vein courses superiorly across the parietal lobe to drain into the superior sagittal sinus?
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Which structure is positioned lateral to the thalamus?
Which structure is positioned lateral to the thalamus?
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The basal vein (of Rosenthal) is primarily formed by the junction of which deep veins?
The basal vein (of Rosenthal) is primarily formed by the junction of which deep veins?
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What is an incorrect classification of thalamic nuclei based on their relationship to the internal medullary lamina?
What is an incorrect classification of thalamic nuclei based on their relationship to the internal medullary lamina?
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Where does the internal cerebral vein eventually drain into?
Where does the internal cerebral vein eventually drain into?
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What anatomical feature is located behind the cavernous sinus?
What anatomical feature is located behind the cavernous sinus?
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Which vein is NOT considered a deep vein in the brain's venous system?
Which vein is NOT considered a deep vein in the brain's venous system?
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Which nerve is NOT present within the cavernous sinus?
Which nerve is NOT present within the cavernous sinus?
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The thalamus acts as a gatekeeper to information transfer based on which factor?
The thalamus acts as a gatekeeper to information transfer based on which factor?
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Which aspect of the thalamus connects it to the lateral aspect of the midbrain?
Which aspect of the thalamus connects it to the lateral aspect of the midbrain?
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Which structure is located below the center of the horizontal pathway in the lateral view of the ventricular system?
Which structure is located below the center of the horizontal pathway in the lateral view of the ventricular system?
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What connects the inner meningeal layer and the outer periosteal layer of the dura mater?
What connects the inner meningeal layer and the outer periosteal layer of the dura mater?
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Which artery arises from the internal carotid artery just before it enters the subarachnoid space?
Which artery arises from the internal carotid artery just before it enters the subarachnoid space?
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What is located just above the cerebral aqueduct in the posterior view of the ventricular system?
What is located just above the cerebral aqueduct in the posterior view of the ventricular system?
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Which two arteries anastomose proximally via the anterior communicating artery?
Which two arteries anastomose proximally via the anterior communicating artery?
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What is the thin layer that closely follows the gyri and sulci on the surface of the brain?
What is the thin layer that closely follows the gyri and sulci on the surface of the brain?
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Which component of the ventricular system is associated with the tail-like projection of the lateral ventricle?
Which component of the ventricular system is associated with the tail-like projection of the lateral ventricle?
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Which space is normally filled with cerebrospinal fluid (CSF) and can be enlarged in cisterns?
Which space is normally filled with cerebrospinal fluid (CSF) and can be enlarged in cisterns?
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What structure is found at the bottom of the vertical pathway in the posterior view of the ventricular system?
What structure is found at the bottom of the vertical pathway in the posterior view of the ventricular system?
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Which part of the brain does the internal carotid artery perfuse primarily?
Which part of the brain does the internal carotid artery perfuse primarily?
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What is the primary function of the arachnoid trabeculae?
What is the primary function of the arachnoid trabeculae?
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What are the two divisions of the middle cerebral artery primarily responsible for perfusing?
What are the two divisions of the middle cerebral artery primarily responsible for perfusing?
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Which layer of the meninges contains the superior sagittal sinus?
Which layer of the meninges contains the superior sagittal sinus?
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What anatomical structure serves as the connection point for the anterior cerebral arteries?
What anatomical structure serves as the connection point for the anterior cerebral arteries?
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Which portion of the cortex is primarily perfused by the inferior division?
Which portion of the cortex is primarily perfused by the inferior division?
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What is the starting point for the vertebrobasilar system of arteries?
What is the starting point for the vertebrobasilar system of arteries?
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Which artery branches off from the basilar artery at the midbrain level?
Which artery branches off from the basilar artery at the midbrain level?
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Where does the superior sagittal sinus drain?
Where does the superior sagittal sinus drain?
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Which sinus drains into the internal jugular vein?
Which sinus drains into the internal jugular vein?
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What is the role of the posterior communicating artery?
What is the role of the posterior communicating artery?
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Which sinus joins with the inferior sagittal sinus to form the straight sinus?
Which sinus joins with the inferior sagittal sinus to form the straight sinus?
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What feature is true about the vessels in the venous drainage network of the cerebral hemispheres?
What feature is true about the vessels in the venous drainage network of the cerebral hemispheres?
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Which artery is primarily responsible for perfusing the inferior and medial temporal and occipital lobes?
Which artery is primarily responsible for perfusing the inferior and medial temporal and occipital lobes?
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What is the significance of the confluence of sinuses?
What is the significance of the confluence of sinuses?
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What is found along the superior edge of the falx cerebri?
What is found along the superior edge of the falx cerebri?
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Which veins drain into the cavernous sinus among its functions?
Which veins drain into the cavernous sinus among its functions?
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What is the main artery involved in the vascular supply of the frontal lobe?
What is the main artery involved in the vascular supply of the frontal lobe?
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What anatomical feature does the sigmoid sinus exit through?
What anatomical feature does the sigmoid sinus exit through?
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What structure connects the midbrain to the medulla?
What structure connects the midbrain to the medulla?
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Which cranial nerve emerges from the midbrain and projects medially from the crus cerebri?
Which cranial nerve emerges from the midbrain and projects medially from the crus cerebri?
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What prominent feature on the posterior surface of the midbrain is responsible for visual processing?
What prominent feature on the posterior surface of the midbrain is responsible for visual processing?
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Which part of the brainstem contains the facial and vestibulocochlear nerves at its junction?
Which part of the brainstem contains the facial and vestibulocochlear nerves at its junction?
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Which structure is the longest portion of the brainstem?
Which structure is the longest portion of the brainstem?
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What does the decussation of the pyramids primarily involve?
What does the decussation of the pyramids primarily involve?
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Which cranial nerve emerges at the junction of the pyramid and the olive in the medulla?
Which cranial nerve emerges at the junction of the pyramid and the olive in the medulla?
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What is the primary role of the trigeminal nerve (CN V) as it emerges from the pons?
What is the primary role of the trigeminal nerve (CN V) as it emerges from the pons?
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What is the characteristic feature of the pons' anterior surface?
What is the characteristic feature of the pons' anterior surface?
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Which structure represents the relationship between the facial nerve fibers and the abducent nerve in the posterior pons?
Which structure represents the relationship between the facial nerve fibers and the abducent nerve in the posterior pons?
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Which anatomical feature separates the left and right halves of the medulla oblongata?
Which anatomical feature separates the left and right halves of the medulla oblongata?
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Which structure can be found lateral to the medullary pyramids in the medulla oblongata?
Which structure can be found lateral to the medullary pyramids in the medulla oblongata?
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Which structure forms the floor of the fourth ventricle?
Which structure forms the floor of the fourth ventricle?
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What is the measured length of the midbrain?
What is the measured length of the midbrain?
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Which of the following statements about relay nuclei is correct?
Which of the following statements about relay nuclei is correct?
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What categorizes specific relay nuclei from nonspecific relay nuclei?
What categorizes specific relay nuclei from nonspecific relay nuclei?
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Which of the following arteries does NOT contribute to the vascular supply of the thalamus?
Which of the following arteries does NOT contribute to the vascular supply of the thalamus?
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Which of the following nuclei is classified as a specific relay nucleus?
Which of the following nuclei is classified as a specific relay nucleus?
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The primary visual cortex receives inputs from which nucleus?
The primary visual cortex receives inputs from which nucleus?
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What is the primary function of the intralaminar nuclei?
What is the primary function of the intralaminar nuclei?
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Which component is found within the midbrain region of the brainstem?
Which component is found within the midbrain region of the brainstem?
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Which thalamic nucleus is primarily associated with auditory processing?
Which thalamic nucleus is primarily associated with auditory processing?
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What defines the reticular nucleus of the thalamus?
What defines the reticular nucleus of the thalamus?
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Which functional classification of thalamic nuclei is involved with limbic and olfactory information?
Which functional classification of thalamic nuclei is involved with limbic and olfactory information?
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Which nucleus processes sensory input from the trunk and limbs?
Which nucleus processes sensory input from the trunk and limbs?
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The brainstem is responsible for which of the following functions?
The brainstem is responsible for which of the following functions?
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Which nucleus is not classified as a specific relay nucleus?
Which nucleus is not classified as a specific relay nucleus?
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What is the primary role of the lateral posterior nucleus in the thalamus?
What is the primary role of the lateral posterior nucleus in the thalamus?
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Which cranial nerves emerge at the junction of the olive and inferior cerebellar peduncles?
Which cranial nerves emerge at the junction of the olive and inferior cerebellar peduncles?
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What structure forms the floor of the fourth ventricle in the medulla?
What structure forms the floor of the fourth ventricle in the medulla?
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What is located on either side of the posterior median sulcus in the medulla?
What is located on either side of the posterior median sulcus in the medulla?
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Which structure is NOT part of the midbrain according to the information provided?
Which structure is NOT part of the midbrain according to the information provided?
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At what level are the pontine nuclei primarily located?
At what level are the pontine nuclei primarily located?
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The tectum is only present at which level of the brainstem?
The tectum is only present at which level of the brainstem?
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Which structure forms the lateral walls of the expanding fourth ventricle at mid-pontine levels?
Which structure forms the lateral walls of the expanding fourth ventricle at mid-pontine levels?
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What is the primary function of the inferior olivary nucleus in the medulla oblongata?
What is the primary function of the inferior olivary nucleus in the medulla oblongata?
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Which structure connects the cerebellum posteriorly and is laterally oriented in the rostral medulla?
Which structure connects the cerebellum posteriorly and is laterally oriented in the rostral medulla?
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Which nucleus can be appreciated just lateral to the medial longitudinal fasciculus in the caudal aspect of the pons?
Which nucleus can be appreciated just lateral to the medial longitudinal fasciculus in the caudal aspect of the pons?
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What is the primary function of the structures located in the tegmentum?
What is the primary function of the structures located in the tegmentum?
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At which level does the decussation of the internal arcuate fibers occur within the medulla?
At which level does the decussation of the internal arcuate fibers occur within the medulla?
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What type of fibers run longitudinally among the transversely oriented pontocerebellar fibers in the rostral pons?
What type of fibers run longitudinally among the transversely oriented pontocerebellar fibers in the rostral pons?
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Which cranial nerve is associated with the abducens nucleus in the caudal pons?
Which cranial nerve is associated with the abducens nucleus in the caudal pons?
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Which of the following nuclei is NOT located in the rostral medulla?
Which of the following nuclei is NOT located in the rostral medulla?
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Which nuclei are primarily visible in caudal sections of the midbrain?
Which nuclei are primarily visible in caudal sections of the midbrain?
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What does the medial lemniscus form in the pons?
What does the medial lemniscus form in the pons?
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Which pathway carries sensory information and decussates at the pyramidal decussation in the caudal medulla?
Which pathway carries sensory information and decussates at the pyramidal decussation in the caudal medulla?
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Which of the following structures is NOT associated with the brainstem?
Which of the following structures is NOT associated with the brainstem?
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What provides vascular supply to the brainstem and arises from the subclavian arteries?
What provides vascular supply to the brainstem and arises from the subclavian arteries?
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Which of the following structures runs adjacent to the midline of the medulla and assists in sensory processing?
Which of the following structures runs adjacent to the midline of the medulla and assists in sensory processing?
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Which structure is primarily responsible for transmitting auditory information from the cochlear nuclei?
Which structure is primarily responsible for transmitting auditory information from the cochlear nuclei?
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Which nucleus is located laterally within the caudal pons and plays a role in the pontine relay?
Which nucleus is located laterally within the caudal pons and plays a role in the pontine relay?
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What structure travels through the cerebral aqueduct in the midbrain and is involved in the flow of cerebrospinal fluid (CSF)?
What structure travels through the cerebral aqueduct in the midbrain and is involved in the flow of cerebrospinal fluid (CSF)?
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What is the primary role of the pontocerebellar fibers located in the mid-pons?
What is the primary role of the pontocerebellar fibers located in the mid-pons?
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Which cranial nerve is primarily involved with the sensory information received from the face and can be found at the level of the trigeminal nerve?
Which cranial nerve is primarily involved with the sensory information received from the face and can be found at the level of the trigeminal nerve?
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Which structure is primarily responsible for modulating responses to pain and temperature sensations within the medulla?
Which structure is primarily responsible for modulating responses to pain and temperature sensations within the medulla?
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Which fissure separates the anterior lobe from the posterior lobe of the cerebellum?
Which fissure separates the anterior lobe from the posterior lobe of the cerebellum?
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What structure connects the cerebellum to the brainstem?
What structure connects the cerebellum to the brainstem?
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Which area of the cerebellum is defined by the posterolateral fissure?
Which area of the cerebellum is defined by the posterolateral fissure?
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What term describes the branching pattern of the folia in the cerebellar cortex?
What term describes the branching pattern of the folia in the cerebellar cortex?
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What anatomical feature covers the surface of the cerebellum?
What anatomical feature covers the surface of the cerebellum?
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Which artery primarily supplies the lateral aspect of the medulla and the inferior portion of the cerebellum?
Which artery primarily supplies the lateral aspect of the medulla and the inferior portion of the cerebellum?
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What is the role of the paramedian branches off of the vertebral arteries in medullary vascularization?
What is the role of the paramedian branches off of the vertebral arteries in medullary vascularization?
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Which of the following branches off the basilar artery supplies the medial aspect of the midbrain?
Which of the following branches off the basilar artery supplies the medial aspect of the midbrain?
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Where does the spinal dura mater extend to in adults?
Where does the spinal dura mater extend to in adults?
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What anatomical structure is formed by the pia mater midway between the anterior and posterior roots?
What anatomical structure is formed by the pia mater midway between the anterior and posterior roots?
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Which arteries branch off the basilar artery and supply the superior cerebellar peduncles?
Which arteries branch off the basilar artery and supply the superior cerebellar peduncles?
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The subarachnoid space of the spinal cord terminates at which vertebral level?
The subarachnoid space of the spinal cord terminates at which vertebral level?
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What is the primary function of the circumferential branches of the basilar artery?
What is the primary function of the circumferential branches of the basilar artery?
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How is the spinal dura mater related to the arachnoid mater in the spinal cord compared to the cranial cavity?
How is the spinal dura mater related to the arachnoid mater in the spinal cord compared to the cranial cavity?
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Which structure can be identified as the deep separation on the anterior surface of the spinal cord?
Which structure can be identified as the deep separation on the anterior surface of the spinal cord?
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What is the primary role of the posterior spinal arteries?
What is the primary role of the posterior spinal arteries?
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Which artery is responsible for supplying blood to the inferior cerebellum?
Which artery is responsible for supplying blood to the inferior cerebellum?
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What type of information do the ascending axonal tracts in the spinal cord primarily convey?
What type of information do the ascending axonal tracts in the spinal cord primarily convey?
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Which arteries are the final branches that emerge from the top of the basilar artery?
Which arteries are the final branches that emerge from the top of the basilar artery?
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What segments define the cervical enlargement in the spinal cord?
What segments define the cervical enlargement in the spinal cord?
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Which structure primarily contains cell bodies of sensory neurons in the spinal cord?
Which structure primarily contains cell bodies of sensory neurons in the spinal cord?
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Which spinal nerve segments comprise the lumbar enlargement?
Which spinal nerve segments comprise the lumbar enlargement?
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What pathways convey sensations of pain and temperature in the spinal cord?
What pathways convey sensations of pain and temperature in the spinal cord?
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Which structure in the spinal cord primarily conveys fine touch and proprioceptive sensations?
Which structure in the spinal cord primarily conveys fine touch and proprioceptive sensations?
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What is the primary function of the lateral funiculus in the spinal cord?
What is the primary function of the lateral funiculus in the spinal cord?
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How many pairs of spinal nerves are derived from the spinal cord?
How many pairs of spinal nerves are derived from the spinal cord?
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What distinguishes the ventral horn from the dorsal horn in gray matter?
What distinguishes the ventral horn from the dorsal horn in gray matter?
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What type of information is processed in the intermediolateral cell column of the spinal cord?
What type of information is processed in the intermediolateral cell column of the spinal cord?
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Which lamina of Rexed corresponds to sensory processing in the dorsal horn?
Which lamina of Rexed corresponds to sensory processing in the dorsal horn?
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What is primarily found in the inner structure of the spinal cord?
What is primarily found in the inner structure of the spinal cord?
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What type of neuron is primarily responsible for transmitting sensory input to the CNS?
What type of neuron is primarily responsible for transmitting sensory input to the CNS?
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What is the extent of the coccygeal nerve pathway?
What is the extent of the coccygeal nerve pathway?
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Which of the following regions is NOT part of the spinal cord but relates to its structure?
Which of the following regions is NOT part of the spinal cord but relates to its structure?
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What is the primary function of the spinothalamic tract?
What is the primary function of the spinothalamic tract?
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Where do the second-order neurons of the spinothalamic tract primarily synapse?
Where do the second-order neurons of the spinothalamic tract primarily synapse?
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Which structure does the spinoreticular tract primarily project to?
Which structure does the spinoreticular tract primarily project to?
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What distinguishes the spinomesencephalic tract from the spinothalamic tract?
What distinguishes the spinomesencephalic tract from the spinothalamic tract?
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In the posterior column–medial lemniscal pathway, first-order neurons carry information from which regions of the body?
In the posterior column–medial lemniscal pathway, first-order neurons carry information from which regions of the body?
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Which part of the spinal cord do first-order neuronal cell bodies of the posterior column–medial lemniscal pathway enter?
Which part of the spinal cord do first-order neuronal cell bodies of the posterior column–medial lemniscal pathway enter?
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The medial lemniscus is formed by the axons of which neurons crossing over?
The medial lemniscus is formed by the axons of which neurons crossing over?
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What role do descending tracts in the spinal cord primarily serve?
What role do descending tracts in the spinal cord primarily serve?
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What is the primary difference between the lateral and medial motor systems?
What is the primary difference between the lateral and medial motor systems?
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What is the main pathway for conveying pain and temperature sensation to the brain?
What is the main pathway for conveying pain and temperature sensation to the brain?
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Which layer of gray matter in the spinal cord is most associated with sensory processing?
Which layer of gray matter in the spinal cord is most associated with sensory processing?
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Which tracts primarily influence the regulation of motor planning?
Which tracts primarily influence the regulation of motor planning?
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What is the role of the axonal collaterals in the spinothalamic tract?
What is the role of the axonal collaterals in the spinothalamic tract?
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What primarily influences motor activity in the direct pathway of the basal nuclei?
What primarily influences motor activity in the direct pathway of the basal nuclei?
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Which structure is medial to the internal capsule?
Which structure is medial to the internal capsule?
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In the indirect pathway, what is the role of the subthalamic nucleus?
In the indirect pathway, what is the role of the subthalamic nucleus?
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What defines the anterior column of the basal nuclei structure?
What defines the anterior column of the basal nuclei structure?
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Which pathway in the basal nuclei is primarily responsible for processing excitatory inputs?
Which pathway in the basal nuclei is primarily responsible for processing excitatory inputs?
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What role does the globus pallidus serve in the basal nuclei?
What role does the globus pallidus serve in the basal nuclei?
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How does the tail of the caudate nucleus terminate?
How does the tail of the caudate nucleus terminate?
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Which neurotransmitter is particularly associated with the excitatory connections in the direct pathway?
Which neurotransmitter is particularly associated with the excitatory connections in the direct pathway?
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What feature distinguishes the posterior limb of the internal capsule?
What feature distinguishes the posterior limb of the internal capsule?
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Which component is NOT part of the basal nuclei?
Which component is NOT part of the basal nuclei?
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What structural feature does the cerebellum utilize for its function?
What structural feature does the cerebellum utilize for its function?
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What is one primary function of the cerebellum?
What is one primary function of the cerebellum?
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Which structure separates the anterior column from the posterior column of the basal nuclei?
Which structure separates the anterior column from the posterior column of the basal nuclei?
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What functional output does the indirect pathway achieve?
What functional output does the indirect pathway achieve?
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Which tract originates from the primary motor cortex and terminates predominantly in the cervical and lumbosacral enlargements?
Which tract originates from the primary motor cortex and terminates predominantly in the cervical and lumbosacral enlargements?
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What is the primary function of the medial motor system?
What is the primary function of the medial motor system?
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What is the primary function of the medial vestibulospinal tract?
What is the primary function of the medial vestibulospinal tract?
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Which artery is considered the largest segmental medullary artery and significantly contributes to perfusion of the lower spinal cord?
Which artery is considered the largest segmental medullary artery and significantly contributes to perfusion of the lower spinal cord?
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Which of these tracts primarily projects bilaterally in the spinal cord?
Which of these tracts primarily projects bilaterally in the spinal cord?
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Which part of the brain controls voluntary movement and posture through its connections with the basal nuclei?
Which part of the brain controls voluntary movement and posture through its connections with the basal nuclei?
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Which of the following describes the pathway of the ventral corticospinal tract?
Which of the following describes the pathway of the ventral corticospinal tract?
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What is the primary vascular supply to the anterior median fissure of the spinal cord?
What is the primary vascular supply to the anterior median fissure of the spinal cord?
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What is the primary role of the tectospinal tract?
What is the primary role of the tectospinal tract?
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Where do axons of the medial vestibulospinal tract project in the spinal cord?
Where do axons of the medial vestibulospinal tract project in the spinal cord?
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Which tract arises from the pontine and medullary reticular formation and impacts automatic posture?
Which tract arises from the pontine and medullary reticular formation and impacts automatic posture?
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Which of the following statements about the medial longitudinal fasciculus is correct?
Which of the following statements about the medial longitudinal fasciculus is correct?
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What distinguishes the anterior corticospinal tract from the lateral corticospinal tract?
What distinguishes the anterior corticospinal tract from the lateral corticospinal tract?
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What type of movements are primarily regulated by the medial motor system?
What type of movements are primarily regulated by the medial motor system?
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What anatomical feature separates the lentiform nucleus from the thalamus?
What anatomical feature separates the lentiform nucleus from the thalamus?
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What is the role of the vestibulospinal tracts?
What is the role of the vestibulospinal tracts?
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Which of the following functions is attributed to the rubrospinal tract?
Which of the following functions is attributed to the rubrospinal tract?
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In which region does the anterior spinal artery primarily supply blood?
In which region does the anterior spinal artery primarily supply blood?
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Which part of the nervous system primarily gives rise to the rubrospinal tract?
Which part of the nervous system primarily gives rise to the rubrospinal tract?
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What is the role of the pons in the context of the reticulospinal tracts?
What is the role of the pons in the context of the reticulospinal tracts?
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What anatomical feature do axons of the tectospinal tract follow within the brainstem?
What anatomical feature do axons of the tectospinal tract follow within the brainstem?
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What is the primary function of the lateral vestibulospinal tract?
What is the primary function of the lateral vestibulospinal tract?
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Which area in the spinal cord receives input from the axons of the pontine reticulospinal tract?
Which area in the spinal cord receives input from the axons of the pontine reticulospinal tract?
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Which tract is involved in mediating reflexive movements in response to visual stimuli?
Which tract is involved in mediating reflexive movements in response to visual stimuli?
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Which structure is NOT part of the basal nuclei?
Which structure is NOT part of the basal nuclei?
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What is the general role of the lateral vestibulospinal tract (VST)?
What is the general role of the lateral vestibulospinal tract (VST)?
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What pathway do second order neurons travel through after the thalamus?
What pathway do second order neurons travel through after the thalamus?
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In which area do tectospinal tract axons synapse within the spinal cord?
In which area do tectospinal tract axons synapse within the spinal cord?
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Which fibers pass through the middle cerebellar peduncle?
Which fibers pass through the middle cerebellar peduncle?
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What is the primary clinical significance of the lateral corticospinal tract?
What is the primary clinical significance of the lateral corticospinal tract?
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Where are the cell bodies of upper motor neurons for the lateral corticospinal tract located?
Where are the cell bodies of upper motor neurons for the lateral corticospinal tract located?
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Which statement best describes the path of axons in the lateral corticospinal tract?
Which statement best describes the path of axons in the lateral corticospinal tract?
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What is the primary role of the rubrospinal tract?
What is the primary role of the rubrospinal tract?
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Which structure is responsible for the decussation of axons forming the lateral corticospinal tract?
Which structure is responsible for the decussation of axons forming the lateral corticospinal tract?
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Which of the following tracts remains ipsilateral and is associated with the medial motor systems?
Which of the following tracts remains ipsilateral and is associated with the medial motor systems?
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Which part of the spinal cord do both the lateral corticospinal and rubrospinal tracts synapse on?
Which part of the spinal cord do both the lateral corticospinal and rubrospinal tracts synapse on?
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What is the role of lower motor neurons in the lateral motor system?
What is the role of lower motor neurons in the lateral motor system?
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What anatomical feature is unique to the rubrospinal tract when compared to the lateral corticospinal tract?
What anatomical feature is unique to the rubrospinal tract when compared to the lateral corticospinal tract?
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Which descending tract is known for its role in the modulation of pain and temperature sensations?
Which descending tract is known for its role in the modulation of pain and temperature sensations?
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In the organization of the spinal cord, where are the ascending tracts located?
In the organization of the spinal cord, where are the ascending tracts located?
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What is the effect of the rubrospinal tract on muscle activity?
What is the effect of the rubrospinal tract on muscle activity?
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Which structure accommodates the transverse pontocerebellar fibers?
Which structure accommodates the transverse pontocerebellar fibers?
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The pathway of which neurons is primarily responsible for transmitting sensory information about conscious proprioception?
The pathway of which neurons is primarily responsible for transmitting sensory information about conscious proprioception?
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Study Notes
Neuron Structure
- Dendrites: Tapered extensions of the cell body that receive information from other neurons
- Soma: Cell body responsible for synthesizing macromolecules and integrating electrical signals
- Axon: Single, cylindrical structure that conducts information to other neurons
- Axon terminals: Vesicle-filled structures that transmit information to other neurons
Nervous System Functional Organization
- Somatic nervous system: Consists of nerves that carry conscious sensation from the periphery to the CNS and nerves that innervate voluntary muscles
- Visceral nervous system: Consists of nerves that carry sensory information to and motor innervation from the CNS to regulate homeostatic functions
Cerebral hemispheres
- Cerebral cortex: Outer surface of the brain composed of gray matter (six layers of cell bodies)
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White matter: Myelinated axonal processes extending from the cell bodies
- Located on the cortical surface and deep inside the cerebral hemispheres
- Gyri: Elevations on the surface of the cerebral hemispheres, increasing surface area
- Sulci: Infoldings on the surface of the cerebral hemispheres
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Lobes: Frontal, parietal, occipital, and temporal
- Frontal lobe: Located anteriorly, separated from the parietal lobe by the central sulcus
- Parietal lobe: Separated from the temporal lobe by the lateral sulcus
- Occipital lobe: Separated from the parietal lobe by the parieto-occipital sulcus
- Temporal lobe: Located at the bottom of the brain
- Longitudinal fissure: Separates the cerebral hemispheres
Ventricular System
- Derived from the inner lumen of the developing neural tube
- Lateral ventricles: Two C-shaped cavities within the cerebral hemispheres
- Choroid plexus: Modified ependymal cells lining the ventricles, producing cerebrospinal fluid (CSF)
- Third ventricle: Slit-like ventricle surrounded by the thalamus and hypothalamus
- Cerebral aqueduct: Connects the third ventricle to the fourth ventricle
- Fourth ventricle: Located between the pons and medulla, anteriorly, and the cerebellum, posteriorly
Meninges
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Dura mater: Tough, fibrous outer layer composed of two layers
- Periosteal layer adherent to the skull
- Meningeal layer lying against the arachnoid mater
- Separates in some regions to form dural venous sinuses
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Arachnoid mater: Middle layer with a network of connective tissue strands (arachnoid trabeculae)
- Connects the outer arachnoid mater to the pia mater
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Pia mater: Thin, veil-like innermost layer that closely follows the brain's surface
- Separated from the arachnoid mater by the subarachnoid space containing CSF and major blood vessels
Cerebral Vasculature
- Anterior circulation: Supplied by the internal carotid arteries
- Posterior circulation: Supplied by the vertebral arteries
- Internal carotid arteries: Branch from the common carotid arteries at the level of the fourth cervical vertebra
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Anterior Cerebral Arteries (ACAs): Anastomose via the anterior communicating artery
- Course along the medial aspect of the cerebral hemisphere
- Perfuse most of the medial aspect of the brain, from the frontal lobe to the anterior portion of the parietal lobe
Middle Cerebral Artery (MCA)
- Branches off the internal carotid artery
- Penetrates the lateral fissure and gives off lenticulostriate striate arteries
- Bifurcates into superior and inferior divisions
- Superior division perfuses the cortex above the lateral fissure, including the lateral frontal lobe and anterior parietal lobe
- Inferior division perfuses the cortex below the lateral fissure, including the temporal lobe and anterolateral portion of the parietal lobe
Posterior Cerebral Cortex
- Receives vascular supply from the vertebrobasilar system of arteries
Vertebrobasilar System of Arteries
- Begins with the vertebral arteries bilaterally
- Vertebral arteries arise from the subclavian arteries and ascend through the foramen transversarium of the cervical vertebrae in the neck
- After entering the foramen magnum at the level of the pontomedullary junction, the arteries join to form the basilar artery
- Basilar artery courses along the midline of the ventral brainstem
- At the level of the midbrain, the basilar artery gives rise to the posterior cerebral artery (PCA)
- PCA turns posteriorly and gives rise to branches that perfuse the inferior and medial temporal and occipital lobes
- PCA also gives rise to the posterior communicating artery, which connects to the internal carotid artery
Venous Drainage
- Cerebral hemispheres drained by a system of deep veins, superficial veins, and dural venous sinuses
- Superficial and deep veins connect to the dural sinuses located between the periosteal and meningeal layers of the dura
- Dural sinuses lack valves
- Superior sagittal sinus runs along the superior edge of the falx cerebri and drains into the transverse sinuses bilaterally
- Each transverse sinus turns inferiorly to form the sigmoid sinus, which exits the jugular foramen to become the internal jugular vein
- Inferior sagittal sinus is located along the inferior margin of the falx cerebri
- Inferior sagittal sinus joins the great vein of Galen to form the straight sinus
- Confluence of sinuses is the point where the straight sinus, superior sagittal sinus, and occipital sinus join
- Confluence of sinuses is drained by the transverse sinuses
- Cavernous sinus is a plexus of veins on either side of the hypophysial fossa
- Cavernous sinus receives drainage from other sinuses and the ophthalmic veins
- Cavernous sinus is drained by the superior petrosal sinus into the transverse sinus and inferior petrosal sinuses into the internal jugular vein
Superficial Veins
- Primarily drain into the superior sagittal sinus and cavernous sinus
- Superficial middle cerebral vein is positioned in parallel to the lateral fissure and drains into the cavernous sinus from the temporal lobe.
- Superior anastomotic vein (of Trolard) connects to the superficial middle cerebral vein perpendicularly
- Superior anastomotic vein courses superiorly across the parietal lobe to drain into the superior sagittal sinus
- Inferior anastomotic vein (of Labbé) connects to the superficial middle cerebral vein perpendicularly
- Inferior anastomotic vein passes inferiorly along the temporal lobe to drain into the transverse sinus
Deep Veins
- More constant in their organization
- Most deep veins eventually drain into the great cerebral vein (of Galen) before entering the dural venous sinuses
- Anterior cerebral vein and deep middle cerebral vein travel adjacent to the ACA and MCA
- Anterior cerebral vein and deep middle cerebral vein join to form the basal vein (of Rosenthal)
- Basal vein continues around the lateral aspect of the midbrain
- Internal cerebral veins are formed at the interventricular foramen by the joining of the septal and thalamostriate veins bilaterally
- Internal cerebral veins and basal veins join to form the great cerebral vein (of Galen)
- Great cerebral vein joins the inferior sagittal sinus to form the straight sinus
Thalamus
- Greek for “inner chamber”
- Large, egg-shaped mass of gray matter derived from the diencephalon of the developing brain
- Most significant role of the thalamus is as a synaptic relay for pathways projecting to the cerebral cortex
- Thalamus also acts as a gatekeeper to prevent or enhance information transfer
- Sensory, motor, limbic, and modulatory signals from behavioral and arousal circuits all have synaptic relays within the thalamic nuclei
Thalamus Location
- Located deep within the brain, near several structures and portions of the ventricular system
- Extends forward to contact the interventricular foramen, which connects the lateral and third ventricles
- Thalamic nuclear masses and the ventrally located hypothalamus comprise the lateral walls of the third ventricle
- Posterior limb of the internal capsule is immediately lateral to the thalamus
- Body of the lateral ventricle is related to the dorsal aspect of the thalamus
- Midbrain portion of the brainstem extends caudally from the thalamus
- Two thalamic masses are interconnected across the midline of the third ventricle by the interthalamic adhesion
Thalamus Organization
- Thalamic nuclei are classified into four groups based on their relationship to the internal medullary lamina: anterior, medial, lateral, and intralaminar
- Nuclei are also divided into three major functional classes: relay, intralaminar, and reticular
- Most of the thalamus is composed of relay nuclei, which have reciprocal excitatory connections with the cortex
- Relay nuclei are further subdivided into specific and nonspecific based on their projections to specific areas of the primary sensory and motor cortex or more diffuse cortical projections
- Majority of specific relay nuclei reside in the lateral thalamus
- All sensory modalities, with the exception of olfaction, have relays in the lateral thalamus before reaching their primary cortical target
- Vascular supply to the thalamus arises from penetrating branches from the ACA, anterior choroidal artery branching from the internal carotid, lenticulostriate arteries of the MCA, and thalamoperforator arteries from the PCAs
Brainstem
- Stalk-like structure within the posterior cranial fossa of the skull connecting the forebrain and spinal cord
- Consists of the midbrain, pons, and medulla oblongata from rostral to caudal
- Brainstem has three main functions:
- It is a conduit for tracts ascending and descending through the CNS
- It houses CN nuclei III to XII
- It is the location for reflex centers related to respiration, cardiovascular function, and regulation of consciousness
External Midbrain
- Approximately 2 cm in length
- Connects the forebrain to the pons caudally and the cerebellum posteriorly
- Deep depression called the interpeduncular fossa is along the midline of the anterior surface
- Crus cerebri are on either side of the interpeduncular fossa
- CN III, the oculomotor nerve, projects medially from the crus
- Superior and inferior colliculi are the most prominent features on the posterior surface, or tectum
- CN IV, the trochlear nerve, emerges between the inferior colliculi, crosses the midline, and wraps around the lateral aspect of the midbrain
- Superior brachium and inferior brachium project in an anterolateral direction from the superior and inferior colliculi laterally
Brainstem Overview
- The brainstem is a vital structure that connects the cerebrum and cerebellum to the spinal cord. It comprises the midbrain, pons, and medulla oblongata.
- Its dorsal surface forms the floor of the fourth ventricle.
External Anatomy of the Brainstem
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Pons:
- Connects the midbrain to the medulla.
- Approximately 2.5 cm long.
- Contains the basilar groove on its anterior surface, housing the basilar artery.
- Has a convex shape due to fibers bridging to the cerebellum through the middle cerebellar peduncle.
- CN V (trigeminal nerve) emerges from its anterolateral surface.
- CN VI (abducent), CN VII (facial), and CN VIII (vestibulocochlear) emerge at the pons-medulla junction.
- Posterior surface forms part of the fourth ventricle floor.
- Facial colliculus: Prominent bump on the posterior surface, where facial nerve fibers loop around the abducent nerve nucleus.
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Medulla Oblongata:
- Longest part of the brainstem, measuring approximately 3 cm.
- Anterior Median Fissure: Midline groove that continues into the spinal cord.
- Pyramids: Lateral to the fissure, they contain motor fibers descending from the cerebral cortex.
- Decussation of Pyramids: Site where most motor fibers cross to the opposite side.
- Olives: Lateral to the pyramids, they represent underlying inferior olivary nuclei.
- CN XII (Hypoglossal Nerve): Emerges at the junction of the pyramid and olive.
- Inferior Cerebellar Peduncles: Connect the cerebellum and medulla.
- CN IX (Glossopharyngeal), CN X (Vagus), and CN XI (Spinal Accessory): Emerge at the junction of the olive and inferior cerebellar peduncle.
- Posterior Median Sulcus: Midline groove on the posterior surface, continuing into the spinal cord.
- Gracile and Cuneate Tubercles: Lateral to the sulcus, they are formed by the underlying gracile nucleus and cuneate nuclei.
Internal Anatomy of the Brainstem
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The brainstem's internal structures are organized into: Tectum (roof), tegmentum (covering), and basis.
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Serial sections stained for myelin help identify nuclear groups and myelinated axons.
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Midbrain:
- Rostral Section: Contains superior colliculi, oculomotor nuclei, Edinger-Westphal nuclei, red nuclei, mesencephalic nuclei of CN V, and substantia nigra.
- Caudal Section: Contains inferior colliculi, trochlear nucleus, mesencephalic nuclei of CN V, and substantia nigra.
-
Pons:
- Rostral Pons: Contains pontine nuclei, pontocerebellar fibers, corticospinal fibers, medial lemniscus, spinothalamic tract, and medial longitudinal fasciculus.
- Mid-Pons: Contains the expanding fourth ventricle with superior cerebellar peduncles forming its lateral walls, middle cerebellar peduncles, motor and principal sensory nuclei of the trigeminal nerve (CN V).
- Caudal Pons: Contains the abducent nucleus (CN VI), medial vestibular nucleus, and anterior and posterior cochlear nuclei.
-
Medulla Oblongata:
- Level of Inferior Olivary Nucleus: Contains nuclei related to CN VIII (vestibulocochlear), CN IX (glossopharyngeal), CN X (vagus), CN XI (spinal accessory), and CN XII (hypoglossal). The medial lemniscus, medial longitudinal fasciculus, and hypoglossal nucleus are also present. The inferior cerebellar peduncle connects to the cerebellum posteriorly.
- Level of Internal Arcuate Fibers Decussation: Contains gracile nucleus, cuneate nucleus, spinal trigeminal nucleus, internal arcuate fibers forming the medial lemniscus, spinocerebellar and anterolateral tracts.
- Level of Pyramidal Decussation: Contains decussating fibers of the pyramids, gracile and cuneate nuclei, and the spinal accessory nucleus (located in the cervical spinal cord).
Vascular Supply to the Brainstem
- The vertebrobasilar system provides blood supply to the brainstem.
- It originates from the vertebral arteries, which arise from the subclavian arteries and ascend through the cervical vertebrae.
- The vertebral arteries fuse to form the basilar artery at the pontomedullary junction.
- The basilar artery terminates as the paired posterior cerebral arteries at the pontomesencephalic junction.
Branches of the Vertebrobasilar System:
-
Vertebral Artery:
- Posterior inferior cerebellar artery (PICA): Supplies the lateral medulla and inferior cerebellum.
- Posterior spinal artery: Supplies the medial and anterior medulla.
- Anterior spinal artery (contributes to): Supplies the anterior spinal cord.
-
Basilar Artery:
- Anterior inferior cerebellar artery (AICA): Supplies the lateral caudal pons.
- Circumferential branches: Supply the rostral lateral pons.
- Paramedian branches: Supply the medial pons.
- Superior cerebellar arteries: Supply the superior cerebellar peduncles, caudal dorsal midbrain, and superior cerebellar hemispheres.
- Posterior cerebral arteries (PCAs): Supply the lateral midbrain, thalamus, medial occipital lobe, and inferior temporal lobe.
Spinal Cord Overview
- The spinal cord is an extension of the medulla oblongata, starting at the foramen magnum and extending down to the L1-L2 vertebral level in adults.
- It contains numerous ascending and descending tracts that connect with the brain to convey sensory and motor information for movement, reflexes, and sensory feedback.
Spinal Meninges
- Three concentric meninges surround the spinal cord: dura mater, arachnoid mater and pia mater.
- The dura mater is continuous with the cranial dura mater and extends down to the vertebral body of S2.
- It's separated from the vertebral canal by the epidural space.
- The arachnoid mater is loosely attached to the dura mater, creating a potential space called the subdural space.
- The subarachnoid space, between the arachnoid and pia mater, extends to the S2 vertebra and contains cerebrospinal fluid (CSF).
- The innermost pia mater is highly vascular, tightly attached to the spinal cord, and forms the denticulate ligament for anchoring the spinal cord within the subarachnoid space.
External Features of the Spinal Cord
- The anterior and posterior surfaces of the spinal cord have longitudinal fissures and sulci.
- The anterior median fissure is a deep groove on the anterior surface.
- The posterior median sulcus is a shallower groove on the posterior surface.
- Thirty-one pairs of spinal nerves emerge from the spinal cord, formed by the convergence of anterior and posterior roots.
- Cervical and lumbar enlargements occur along the spinal cord, accommodating the neurons innervating the upper and lower extremities respectively.
Internal Features of the Spinal Cord
- A cross-section of the spinal cord reveals an inner H-shaped grey matter containing neuronal cell bodies and an outer white matter composed of myelinated axons.
- The anterior horns of the grey matter house the cell bodies of motor neurons.
- The posterior horns contain cell bodies receiving sensory information.
- The intermediolateral cell column, located in the T1 to L2 region, accommodates the preganglionic cell bodies of the sympathetic nervous system.
- The grey matter is further divided into 10 zones known as Rexed's laminae, which are important for understanding the ascending and descending tracts.
Ascending Tracts in the Spinal Cord
- Sensory information travels through ascending tracts to the brain.
- These tracts convey modalities like pain, temperature, touch and proprioception.
- Conscious perception of sensory information reaches the primary somatosensory cortex.
- Subconscious sensory information reaches other structures, like the cerebellum.
Anterolateral Pathways
- Conveys sensations of pain, temperature, and crude touch.
- Composed of three tracts: spinothalamic, spinoreticular, and spinomesencephalic.
- The spinothalamic tract carries pain information.
- First-order neurons, located in spinal ganglia, send axons to the posterior horn of the spinal cord.
- Second-order neurons cross over to the contralateral side and ascend to the thalamus.
- Third-order neurons project to the primary somatosensory cortex.
- The spinoreticular tract projects to the brainstem reticular formation for emotional and arousal aspects of pain.
- The spinomesencephalic tract projects to the midbrain for central pain modulation.
Posterior Column-Medial Lemniscal Pathway
- Conveys discriminative touch, vibration, and conscious proprioception.
- First-order neurons, located in spinal ganglia, send axons to either the gracile fasciculus (for lower limb and trunk information) or the cuneate fasciculus (for upper limb and neck information).
- These axons ascend ipsilaterally to the medulla.
- Second-order neurons are located in the nucleus gracilis and nucleus cuneatus, and their axons cross over to form the medial lemniscus.
- These axons ascend to the thalamus.
- Third-order neurons project to the primary somatosensory cortex.
Descending Tracts in the Spinal Cord
- Descending tracts originate from the cerebral cortex and brainstem, involved in voluntary, postural and coordinated movements.
- These pathways are influenced by sensory input and feedback loops from the cerebellum and basal ganglia.
Lateral Motor Systems
- Includes the lateral corticospinal tract and rubrospinal tract, both located in the lateral column of the spinal cord.
- The lateral corticospinal tract controls movement of the upper and lower limbs.
- Upper motor neurons originate in the primary motor cortex, descend through the brainstem, decussate at the medulla, and become the lateral corticospinal tract.
- These axons synapse on lower motor neurons in the spinal cord, and their axons exit through the anterior root.
- The rubrospinal tract originates in the red nucleus, crosses over in the midbrain, and descends through the brainstem and spinal cord.
- It facilitates flexor muscle activity in the upper limb and inhibits extensor muscle activity.
Somatosensory Pathways
- The medial lemniscal pathway, or dorsal columns, conveys conscious proprioception, vibration, and discriminative touch.
- The pathway consists of three order neurons:
- First order neurons start in the nucleus cuneatus or nucleus gracilis in the medulla, then pass through the fasciculus gracilis or fasciculus cuneatus in the cervical cord, and finally enter the lumbar cord.
- Second order neurons, called internal arcurate fibers, start in the thalamus, enter the midbrain, pass through the medial lemniscus of the pons, and enter the medulla.
- Two branches of the third order neurons pass from the lower limb and finally into the thalamus.
Medial Motor Systems
- Tracts of the medial motor system regulate axial or truncal muscles involved in maintaining posture, balance, and automatic gait-related movements and orientating movements of the head and neck.
- Tracts in this system primarily project bilaterally on interneurons within the spinal cord.
Anterior Corticospinal Tract
- Formed by descending upper motor neurons that did not decussate in the caudal medulla to form the lateral corticospinal tract.
- These upper motor neurons descend through the medial aspect of the anterior spinal cord to the level of the upper thoracic region.
- They project bilaterally to synapse on cell bodies of lower motor neurons in the medial portion of the anterior horn gray matter.
Tectospinal Tract
- Axons arise from cell bodies located in the superior colliculus of the dorsal midbrain.
- These axons decussate in the dorsal tegmental decussation shortly after leaving the nucleus to form the tectospinal tract along the midline of the brainstem.
- The tectospinal tract continues through the brainstem near the medial longitudinal fasciculus and into cervical regions of the spinal cord near the anterior median fissure.
- Within the cervical spinal cord, axons project bilaterally to synapse on cell bodies of interneurons in the anterior horn gray matter.
- The superior colliculus receives visual input, and the tectospinal tract modulates reflex postural movements in response to visual stimuli.
Vestibulospinal Tract
- Axons arise from vestibular nuclei located in the pons and medulla.
- The medial vestibular nucleus gives rise to the medial vestibulospinal tract, which projects bilaterally to thoracic regions of the spinal cord.
- The lateral vestibular nucleus gives rise to the lateral vestibulospinal tract, which descends ipsilaterally through the entire length of the spinal cord to synapse on interneurons in the anterior horn gray matter.
- The vestibular nuclei receive sensory input from the inner ear and cerebellum, and this tract facilitates activity of extensor/antigravity muscles and inhibits activity of flexor muscles to maintain balance and an upright posture.
Reticulospinal Tract
- Axons arise from the reticular formation in the pons and medulla.
- The axons of the pontine and medullary reticulospinal tracts descend ipsilaterally through the length of the spinal cord in the anterior white matter and synapse with interneurons in the anterior horn gray matter.
- They are believed to function in regulating voluntary movements in reflex activity and autonomic outflow.
Vascular Supply to the Spinal Cord
- Blood supply to the spinal cord is by three longitudinally running vessels and several segmental branches.
- The longitudinally running vessels are the anterior spinal artery and two posterior spinal arteries.
- The posterior spinal arteries originate in the cranial cavity as branches of either the vertebral artery or PICA.
- These arteries descend along the length of the posterior spinal cord on the posterolateral sulcus.
- The single anterior spinal artery originates within the cranial cavity from the union of two contributing branches from the vertebral arteries.
- The anterior spinal artery descends along the length of the anterior spinal cord on the anterior median fissure.
- Reinforcing vascular supply to these longitudinally running vessels is provided by eight to ten segmental medullary arteries.
- The largest segmental medullary artery is the artery of Adamkiewicz in the lower thoracic or upper lumbar region.
- This vessel is typically on the left side and contributes significantly to perfusion of the lower portion of the spinal cord.
- Venous drainage of the spinal cord occurs through a series of longitudinally running channels that connect with the anterior and posterior spinal veins on the surface of the cord.
Basal Nuclei
- The basal nuclei are a collection of gray matter structures deep within the base of the forebrain.
- They have a significant role in controlling posture and voluntary movement.
- They also have connections to limbic system pathways.
Corpus Striatum
- The corpus striatum (Latin for “striped body”) includes the caudate nucleus and lentiform nucleus.
- The lentiform nucleus (Latin for “lens-shaped”) includes the globus pallidus and putamen.
- Both of these structures are lateral to the internal capsule, which separates them from the thalamus and caudate nucleus medially.
- Medial to the internal capsule is the caudate nucleus.
- The caudate nucleus is a large C-shaped structure divided into a head, body, and tail, which closely follows the shape of the lateral ventricle.
- The tail of the caudate continues anteriorly within the roof of the inferior horn of the lateral ventricle to terminate in the amygdaloid nucleus.
Connections of the Basal Nuclei
- Input to the basal nuclei is primarily received by the striatum (caudate nucleus and putamen), and output predominantly leaves from the globus pallidus.
- Two simplified neuronal loops are described: the direct pathway and the indirect pathway.
- The direct pathway has a series of connections through the basal nuclei, which result in an overall increase in motor activity.
- The indirect pathway has a similar course, with the addition of output connections to the subthalamic nucleus, which results in an overall decrease in motor activity.
Cerebellum
- The cerebellum is the largest structure of the hindbrain.
- It resides within the posterior cranial fossa and is composed of two large hemispheres, which are connected by the vermis in the midline.
- The cerebellum plays a role in maintaining balance and influencing posture and is responsible for coordinating movements by synchronizing contraction and relaxation of voluntary muscles.
Structures of the Cerebellum
- Within the posterior cranial fossa, the cerebellum is covered by the tentorium cerebelli of the dura mater and connects to the posterior surface of the brainstem via the superior, middle, and inferior cerebellar peduncles.
- Anteriorly, the cerebellum forms the roof of the fourth ventricle.
- On its surface, the cerebellum has several convoluted folds, or folia, separated by fissures.
- Two of these fissures serve as landmarks to divide the cerebellum into three lobes.
- Superiorly, the primary fissure separates the anterior lobe from the posterior lobe.
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