Week 2 Flashcards
- An elderly patient has normal pressure hydrocephalus due to scarring of the pia-arachnoid and arachnoid villi. This prevents resorption of the CSF into which structure?
Answer: The superior sagittal sinus.
Arachnoid villi drain into the superior sagittal sinus.
Lecture: Lab 1: Brain Coverings and General Features
Objective 1. Identify the bridging veins, superior sagittal sinus and arachnoid granulations
- What is the only direct sensory to motor pathway? Where do its synapses occur (2 options)?
ANSWER: The motor stretch reflex. Its synapses occur either in the ventral horns of the spinal cord or in cranial nerve motor nuclei of the brainstem. Other spinal reflexes have two or more synapses and incorporate interneurons, allowing for more complex processing.
Lecture: Brain and Spinal Cord
Objective 5. Describe the functions of dorsal (sensory) and ventral (motor) spinal cord and identify their major components; dorsal columns, second order neurons of anterolateral system, interneurons, lateral descending corticospinal tracts, lower motor neurons. (medical knowledge, MKS – 1a)
- What does afferent mean? Efferent? Are sensory cues transmitted to the brain by afferent or efferent paths?
ANSWER: Afferent generally means “ascending” while efferent means “descending.” Thus, sensory information travels to the brain via afferent paths.
Lecture: Brain and Spinal Cord
Objective 1. Acquire a basic neuroscience vocabulary to help organize detailed content to be presented in the neurology module. (medical knowledge, MKS – 1a)
- The resting potential in Neurons is roughly ___ mV. This potential is governed primarily by the permeability of which ion?
ANSWER: Resting neuronal potential is roughly -70mV. This is governed by predominantly high K+ permeability and a high internal K+ concentration. Other ions also contribute to a lesser extent, including Na+.
Lecture: Brain and Spinal Cord
Objective 3. Refresh your knowledge of the membrane properties and ionic distributions underlying the resting and action potentials. (medical knowledge, MKS – 1a)
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- At what age is the corticospinal tract fully myelinated? The corpus callosum? In what direction does myelination occur in the developing brain?
ANSWER: Myelination occurs in the caudal to rostral direction. From the CNS development learning guide: “The spinal cord and brainstem myelinate first. This is to expand the capacity for learning activities, memory, and complex sensory perception. The corticospinal tract is not fully myelinated until 2 years of age, the corpus callosum until late adolescence, and the ipsilateral frontotemporal association bundle is the last to myelinate at about 32 years.”
Lecture: CNS development
Objective 6. Distinguish the direction of myelination in the developing brain (MKS1a)
- Which of these pairings of embryonic structure and CNS derivative is/are incorrect?
a) telencephalon -> cerebral hemispheres and lateral ventricles
b) diencephalon -> thalami and cerebral aqueduct
c) mesencephalon -> midbrain and third ventricle
d) metencephalon -> pons and cerebellum and upper 4th ventricle
e) myencephalon -> medulla and lower 4th ventricle
ANSWER: b and c are incorrect. Correct pairings:
a) telencephalon -> cerebral hemispheres and lateral ventricles
b) diencephalon -> thalami and third ventricle
c) mesencephalon -> midbrain and cerebral aqueduct
d) metencephalon -> pons and cerebellum and upper 4th ventricle
e) myencephalon -> medulla and lower 4th ventricle
Lecture: CNS development
Objective 3. Name the embryonic dilatations that give rise to the CNS and their derivatives (MKS1a)
- Within the fasciculi of the DCML, which body segment is represented most medially? Most laterally?
ANSWER: The gracile fasciculus of the DCML is more medial, while the cuneate fasciculus is more lateral. From medial to lateral: sacral and lumbar (gracile), thoracic and cervical (cuneate).
Lecture: Spinal Cord Anatomy
Objective 2. Describe the basic anatomy of the spinal cord including the different spinal cord tracts and the information transmitted through each tract. (MKS-1a)
At what level does the conus medullaris begin?
ANSWER: L1. The conus medularis is the caudal, tapering portion of the cord. Further in the caudal direction is the cauda equina.
Lecture: Spinal Cord Anatomy
Objective 2. Describe the basic anatomy of the spinal cord including the different spinal cord tracts and the information transmitted through each tract. (MKS-1a)
- A patient presents with double vision, inability to move his right eye medially or upward, ptosis, and dilated right pupil. He also has left hemiplegia. Which artery is likely to be occluded?
ANSWER: This is ventral midbrain syndrome (Weber’s syndrome), caused by an occlusion of the posterior cerebral artery. Contralateral hemiplegia is seen because of the affected corticospinal tract, and ipsilateral oculomotor nerve palsy causes “down and out” eye position (lateral strabismus), ptosis, and mydriasis.
Lecture: Cranial Nerves and Brain Lesions
Objective 5. List the causes and deficits of the medial medullary syndrome, the lateral medullary (Wallenberg’s) syndrome and the ventral (Weber’s) syndrome of the midbrain (MKS1b).
- From medial to lateral, what are the six columns of nerve nuclei in the adult CNS?
ANSWER: Medial to lateral: Somatic motor Parasympathetic Branchial motor ---sulcus limitans--- Taste/Visceral sensory Special sensory Somatic Sensory
Lecture: Cranial Nerves and Brain Lesions
Objective 3. List from medial to lateral the six columns of nuclei and the location (medulla, pons, and midbrain) of the nuclei in each column in the adult (MKS1a).
