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Questions and Answers
What is the primary composition of white matter in the central nervous system?
What is the primary composition of white matter in the central nervous system?
- Myelinated axons (correct)
- Neuroglial cells
- Efferent nerve fibers
- Unmyelinated axons
Which term describes a stout bundle of white matter that connects two major parts of the brain?
Which term describes a stout bundle of white matter that connects two major parts of the brain?
- Capsule
- Fasciculus
- Peduncle (correct)
- Tract
What anatomical term is used to refer to the 'lower' part of the central nervous system?
What anatomical term is used to refer to the 'lower' part of the central nervous system?
- Caudal (correct)
- Rostral
- Superior
- Inferior
Which of the following structures is a groove in the brain?
Which of the following structures is a groove in the brain?
What is the term for a bundle of axons that traverse the subarachnoid space?
What is the term for a bundle of axons that traverse the subarachnoid space?
Which of the following options best describes the spinothalamic tract?
Which of the following options best describes the spinothalamic tract?
Which term refers to any bundle of nerve fibers, central or peripheral?
Which term refers to any bundle of nerve fibers, central or peripheral?
From which embryonic layer are neurons and neuroglial cells derived?
From which embryonic layer are neurons and neuroglial cells derived?
What condition is described when the flow of cerebrospinal fluid (CSF) is blocked in the subarachnoid space?
What condition is described when the flow of cerebrospinal fluid (CSF) is blocked in the subarachnoid space?
Which spinal nerve is the highest and penetrates the atlanto-occipital membrane?
Which spinal nerve is the highest and penetrates the atlanto-occipital membrane?
What is indicated by the term 'dermatome'?
What is indicated by the term 'dermatome'?
Which spinal nerves go through foramina above their corresponding vertebrae?
Which spinal nerves go through foramina above their corresponding vertebrae?
What happens when a single spinal nerve or its ganglion is transected?
What happens when a single spinal nerve or its ganglion is transected?
Hydrocephalus ex vacuo is characterized by what condition?
Hydrocephalus ex vacuo is characterized by what condition?
Which spinal nerves utilize foramina below their corresponding vertebrae?
Which spinal nerves utilize foramina below their corresponding vertebrae?
What condition can lead to communicating hydrocephalus when obstructing the flow of CSF?
What condition can lead to communicating hydrocephalus when obstructing the flow of CSF?
What are the primary components of the spinocerebellum?
What are the primary components of the spinocerebellum?
What is the primary function of the spinocerebellum?
What is the primary function of the spinocerebellum?
What is a consequence of a lesion in the midline of the spinocerebellum?
What is a consequence of a lesion in the midline of the spinocerebellum?
Which structure receives afferents from extensive areas of the cerebral cortex?
Which structure receives afferents from extensive areas of the cerebral cortex?
What classical manifestations indicate a pontocerebellar disorder?
What classical manifestations indicate a pontocerebellar disorder?
Where does the dentate nucleus send its axons?
Where does the dentate nucleus send its axons?
Which part of the cerebellum is most affected by lesions resulting in ipsilateral clinical signs?
Which part of the cerebellum is most affected by lesions resulting in ipsilateral clinical signs?
What type of signals does the cuneocerebellar tract relay?
What type of signals does the cuneocerebellar tract relay?
What is the primary role of the hippocampus in relation to memory?
What is the primary role of the hippocampus in relation to memory?
Which structure is involved in sending axons to the anterior nuclei of the thalamus?
Which structure is involved in sending axons to the anterior nuclei of the thalamus?
What outcome is associated with bilateral interruption of the hippocampal circuitry?
What outcome is associated with bilateral interruption of the hippocampal circuitry?
Which part of the limbic system is NOT mentioned as being connected with the hippocampus?
Which part of the limbic system is NOT mentioned as being connected with the hippocampus?
What happens when the amygdala is electrically stimulated in humans?
What happens when the amygdala is electrically stimulated in humans?
What behavioral changes may occur if lesions affect the prefrontal cortex?
What behavioral changes may occur if lesions affect the prefrontal cortex?
Which area of the brain is specified as being connected with the olfactory system?
Which area of the brain is specified as being connected with the olfactory system?
What condition may result from lesions in the mamillothalamic tracts?
What condition may result from lesions in the mamillothalamic tracts?
What initiates the flow of cerebrospinal fluid into the subarachnoid space?
What initiates the flow of cerebrospinal fluid into the subarachnoid space?
Which structure of the midbrain is located dorsal to the cerebral aqueduct?
Which structure of the midbrain is located dorsal to the cerebral aqueduct?
Which cranial nerves are associated with the solitary nucleus?
Which cranial nerves are associated with the solitary nucleus?
What role do corticobulbar fibers have in the brain stem?
What role do corticobulbar fibers have in the brain stem?
What is the function of the spinal trigeminal nucleus?
What is the function of the spinal trigeminal nucleus?
Which of the following describes the relationship between the motor nuclei and the ventral horn of the spinal gray matter?
Which of the following describes the relationship between the motor nuclei and the ventral horn of the spinal gray matter?
What type of neurons are predominantly found in the reticular formation of the brain stem?
What type of neurons are predominantly found in the reticular formation of the brain stem?
Which statement correctly identifies part of the function of inferior and superior colliculi?
Which statement correctly identifies part of the function of inferior and superior colliculi?
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Study Notes
Central Nervous System - Terminology
- Rostral means higher (towards the beak) and caudal means lower (towards the tail)
- Sulcus is a groove
- Gyrus is a convexity delimited by sulci
- Fasciculus is a bundle of nerve fibers (central or peripheral)
- Capsule is a flattened region of white matter
- Peduncle is a stout bundle of white matter that joins two major brain parts
- Tract is a region of the CNS with axons of neurons with the same origin and destination
- Root is a bundle of axons that traverses the subarachnoid space
Spinal Nerve Formation
- Spinal nerves are formed by the union of a dorsal (sensory) root and a ventral (motor) root at each intervertebral foramen.
- The highest spinal nerve is C1 which penetrates the atlanto-occipital membrane, above the atlas vertebra (C1)
- Cervical nerves 1 to 7 pass through foramina above the numbered vertebrae.
- C8’s roots pass below the arch of vertebra C7 and above that of T1.
- Thoracic (T1-T12), lumbar (L1-L5) and sacral (S1-S5) nerves go through foramina below the equivalently numbered vertebrae.
Dermatomes
- Dermatomes are bands of skin innervated by a single dorsal root ganglion.
- Each ganglion also supplies skin in the dermatomes above and below its own level.
- Three adjacent dorsal roots or spinal nerves need to be transected to completely denervate a dermatome.
Cerebrospinal Fluid Flow
- CSF flows from the ventricular system into the subarachnoid space through apertures in the fourth ventricle's roof.
- The fourth ventricle becomes the cerebral aqueduct at the rostral border of the pons.
- The tectum is above the aqueduct.
Brain Stem
- The brain stem contains the nuclei of cranial nerves III-XII.
- Motor nuclei correspond to cells of the ventral horn of the spinal gray matter.
- Sensory nuclei correspond to the dorsal horn.
- Other cranial nerve nuclei have no spinal cord equivalent.
- Other major groups of neurons in the brain stem include nuclei connected with the cerebellum and the reticular formation.
Motor Pathways and Nuclei
- The most ventral parts of the midbrain, pons, and medulla contain corticopontine, corticospinal, and corticobulbar tracts.
- The spinal trigeminal nucleus extends from mid-pontine level to the dorsal horn of the spinal gray matter.
- The solitary nucleus extends the length of the medulla.
Cerebellum
- The spinocerebellum consists of the vermis and the rostral part of the cerebellum. It receives spinocerebellar and cuneocerebellar tracts.
- The pontocerebellum is the largest division and receives input from the contralateral pontine nuclei.
- All areas of the cerebellum receive input from the inferior olivary nuclei of the medulla.
The Limbic System
- Association and commissural fibers connect sensory association areas with the entorhinal area, which projects to the hippocampus.
- The hippocampus projects to the mammillary body of the hypothalamus via the fornix.
- The mammillary body sends axons to the anterior nuclei of the thalamus.
- The thalamus projects to the anterior part of the cingulate gyrus.
- The cingulate gyrus, entorhinal area and intervening cortex constitute the limbic lobe.
- The hippocampus, amygdala, and certain brain stem nuclei form the limbic system.
Bilateral Hippocampal Interruption
- Leads to loss of the ability to form new memories.
- Older memories can still be recalled, likely stored diffusely throughout the cerebral cortex.
- Lesions can occur in the entorhinal area and hippocampus (Alzheimer’s disease), fornices (tumors or surgery), or mamillothalamic tracts (Korsakoff’s psychosis).
Amygdala and Prefrontal Cortex
- The amygdala, in the anterior temporal lobe, has extensive two-way connections with the prefrontal cortex (frontal pole and orbital surface), and temporal lobe cortex.
- The amygdala descends to the hypothalamus, epithalamus, and several brain stem nuclei.
- Electrical stimulation of the amygdala causes fear.
- Amygdala lesions result in docility, flattened emotions, and occasionally increased or perverted sexual activity.
Prefrontal Cortex
- Lesions must be bilateral to affect behavior.
- Patients become rude, inconsiderate, and unable to foresee the consequences of their actions.
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