Nerve to Meet You [Neurohistology/Neurophysiology]
These twisted pairs of actin filaments cause movement of growing axonal tips during development and regeneration.
What are microfilaments?
This term refers to an axon bundle that crosses the midline to go from one location on one side of the body to another location on the contralateral side. Name a common example of this.
What is a decussation? example: pyramidal decussation in lower medulla
These 3 structures make up the tapered end of the spinal cord, the bundle of nerve roots descending below it, and the thin connective tissue strand that anchors the cord to the coccyx.
What is the conus medullaris, the cauda equina and the filum terminale?
The lateral cord is formed by these divisions of these trunks.
What is the anterior divisions of the upper and middle trunks.
These are the days the anterior and posterior neuropore close on, respectively. Name the neural tube defect associated with the failure of the closure of each neuropore.
What are days 24 and 26. Failure of anterior neuropore closure > anencephaly. Failure of posterior neuropore closure > spina bifida.
Movement of this ion typically causes depolarization, while movement of this ion typically causes hyperpolarization. Bonus if you can specify whether the ion is moving in or out of the cell!
What is sodium INFLUX (depolarization) and potassium EFFLUX (hyperpolarization)?
A patient presents with right lower facial droop and difficulty processing language. This is the likely affected artery and the two cortical regions responsible for the deficits.
What is the left MCA and what is the facial region of the precentral gyrus and Wernickes area.
These levels of the spinal cord have white rami communicans, compared to these levels that have gray rami communicans.
What are T1-L2 (white) and all spinal levels (gray)?
The axillary nerve contains fibers from these roots.
What is C5-C6.
The prosencephalon divides into these two secondary vesicles. Name them and their major adult brain derivatives.
What are the: 1) Telencephalon: cerebral cortex, most basal ganglia, and subcortical white matter and 2) Diencephalon: thalamus, hypothalamus; also retina and optic nerve
3 PARTS: This is the glial cell that forms myelin in the CNS, the concentric layers created by its wrapping, and the type of conduction that allows signals to "jump" between nodes of Ranvier.
What are Schwann cells, lamellae and saltatory conduction?
This is the direction of the flow of CSF from its origin in the choroid plexus in the lateral ventricles, through its drainage into the internal jugular veins.
What is lateral ventricles > intraventricular foramen of Monro > third ventricle > cerebral aqueduct > fourth ventricle > median foramen (Magendie) and lateral foramen (Luschka) > subarachnoid space > arachnoid villi > dural venous sinuses > confluence > transverse > sigmoid > IJ
These two limb muscle groups are represented dorsally and ventrally, respectively, within the lateral ventral horn in the spinal cord.
What are the flexors dorsally and the extensors ventrally.
A patient has tingling in the thumb, index and middle fingers, along with weakness of the thenar muscles. What is the compressed nerve and associated diagnosis?
What is the median nerve and carpal tunnel syndrome?
Three patients have hindbrain malformations. One has isolated cerebellar tonsillar descent; another has myelomeningocele with downward displacement of the brainstem; the third has a cystically enlarged fourth ventricle. These are the three diagnoses, respectively.
What are Chiari Type I, Chiari Type II, and Dandy Walker syndrome.
Blocking this ion's entry into the presynaptic terminal prevents it from triggering synaptic vesicle fusion and neurotransmitter release.
What is calcium?
A patient with rising ICP from a right-sided glioblastoma develops a blown pupil and impaired eye movement on one side. Name the structure that may be herniating and the gyrus it projects from, the opening it passes through, and the cranial nerve it compresses. Specify the expected side of the eye findings.
What is the uncus, the parahippocampal gyrus, and cranial nerve III (oculomotor). Eye findings would be on right side (same side as compression).
This spinal cord cross-section has enlarged ventral horns, relatively little white matter, and fasciculus gracilis without fasciculus cuneatus. Explain the reasoning for each of these findings!
What is the lumbar cord? Enlarged ventral horns > hella motor neurons supplying the lower limbs. Less white matter than above > fewer ascending fibers have accumulated, and many descending fibers have already terminated. Gracilis only > upper body sensory fibers have not entered at this level
An injury interrupts all three posterior divisions while sparing the anterior divisions. The patient develops wrist drop. Name the injured cord and the terminal branch affected. Then, predict one additional movement deficit that would indicate the other terminal branch from this cord being affected.
What are the posterior cord and radial nerve? Shoulder abduction or external rotation issues could also be present, indicating the axillary nerve is affected.
A defect affects neural crest cells but spares the neural tube. Determine whether each would be directly affected or spared: peripheral myelination, adrenal medullary chromaffin cells, spinal motor neurons, and CNS myelination. Name the myelinating cell in each system.
The NEURAL CREST derivatives would be affected! > peripheral myelination (Schwann cells), adrenal medullary chromaffin cells.
The NEURAL TUBE derivatives would be spared > CNS myelination (oligodendrocytes), spinal motor neurons.
A neuron receives a barely suprathreshold stimulus, then a much stronger one. This is what happens to action potential amplitude and firing frequency, and this is the idea that explains the amplitude.
What are unchanged amplitude with potentially increased action potential firing frequency! Due to the action potential "all or none" principle.
An infection spreads from outside the cranial cavity into a dural venous sinus. Name the sinus, the artery and cranial nerve passing through it, and the four cranial nerves located in its lateral wall.
What are the cavernous sinuses; ICA and CN VI abducens run through; CN III oculomotor, IV trochlear, and both divisions of V trigeminal (V1 ophthalmic and V2 maxillary) located in lateral wall.
A sympathetic pathway begins at T5 and reaches an abdominal organ without synapsing in the sympathetic chain. This is its full route from its first cell body to the target, identifying where the synapse occurs and whether each portion is preganglionic or postganglionic.
what is: T5 intermediolateral column > ventral root > T5 spinal nerve → ventral ramus → white ramus communicans → sympathetic chain → splanchnic nerve → prevertebral ganglion → target organ. Everything BEFORE prevertebral synapse=preganglionic, everything AFTER=postganglionic.
Two patients have posterior forearm numbness: one from a spinal root injury, the other from a terminal branch injury. Name the dermatome affected in the first patient and the terminal branch affected in the second patient.
first patient- C7 dermatome. second patient- radial nerve lesion.
In the developing spinal cord, neuroblasts leave the ventricular zone and settle in this zone, while their axons extend into this outer zone.
In the cerebral cortex, neuroblasts instead migrate along this scaffold and arrange themselves in this developmental sequence.
What are the intermediate zone, the marginal zone, the radial glia, and "inside out" development.