Neurobiology

Question 1

You are caring for an outpatient who has a history of spinal cord injury. You have prescribed oxybutynin for frequent urination. What class of medication is oxybutynin?
A. Muscarinic
B. Anticholinergic
C. Cholinergic
D. Nicotinic
E. Glutamatergic

Answer 1

A. Muscarinic
B. Anticholinergic
C. Cholinergic
D. Nicotinic
E. Glutamatergic

Oxybutynin is an anticholinergic drug that works on M1-3 muscarinic receptors in the bladder wall, inhibiting the activity of acetylcholine at this receptor. This leads to bladder relaxation which can help limit bladder spasticity and frequent urination. Further Reading: Jallo, Vaccaro. Neurotrauma and Critical Care of the Spine, 2009, page 178. Citow, Macdonald, Refai. Comprehensive Neurosurgery Board Review, 2nd edition, 2010.

Question 2

Astrocytes of the brain sequester what ion?
A. Sodium
B. Potassium
C. Calcium
D. Chloride
E. Magnesium

Answer 2

A. Sodium
B. Potassium
C. Calcium
D. Chloride
E. Magnesium

Astrocytes serve multiple functions in the brain, but they actively sequester potassium from the extracellular space in order to keep extracellular potassium levels low, thus maintaining the gradient of potassium required for membrane depolarization. Further Reading: Jallo, Loftus. Neurotrauma and Critical Care of the Brain, 2009, page 34.

Question 3

What receptor utilizes an excitatory neurotransmitter of the brain as a ligand?
A. GABA
B. Ryanodine
C. NMDA
D. Muscarinic
E. Nicotinic

Answer 3

A. GABA
B. Ryanodine
C. NMDA
D. Muscarinic
E. Nicotinic

The NMDA receptor utilizes glutamate as a ligand and after glutamate binds to the receptor, ion channels permeable to Na, K, and Ca open. It has been found to be associated with gene expression, synaptic plasticity, and other signaling systems. It is associated with pain, and ketamine is an NMDA receptor antagonist that can treat pain. Further Reading: Burchiel. Surgical Management of Pain, 2nd edition, 2015, page 296. Greenstein B, Greenstein A. Color Atlas of Neuroscience, 2000, page 108.

Question 4

Which of the following hypothalamic nuclei are associated with ADH secretion?
A. Periventricular
B. Lateral
C. Ventromedial
D. Median eminence
E. Supraoptic

Answer 4

A. Periventricular
B. Lateral
C. Ventromedial
D. Median eminence
E. Supraoptic

The supraoptic nucleus of the hypothalamus is one of the anterior nuclei and is associated with ADH secretion from the posterior pituitary. Further Reading: Greenstein B, Greenstein A. Color Atlas of Neuroscience, 2000, page 308

Question 5

5. Which of the following hypothalamic nuclei is associated with ADH secretion and has diffuse connections in the spinal cord and brainstem?
   A. Periventricular
   B. Paraventricular
   C. Supraoptic
   D. Posterior
   E. Suprachiasmatic

Answer 5

A. Periventricular
B. Paraventricular
C. Supraoptic
D. Posterior
E. Suprachiasmatic

The supraoptic and paraventricular nuclei of the anterior hypothalamus are associated with secretion of ADH from the posterior pituitary. Of these two, the paraventricular nucleus also has diffuse connections to the spinal cord and brainstem. Further Reading: Greenstein B, Greenstein A. Color Atlas of Neuroscience, 2000, page 308. Greenstein B, Greenstein A. Color Atlas of Neuroscience, 2000, page 294.

Question 6

The use of variable angle screws on a plate during anterior cervical discectomy and fusion surgery helps to diminish what according to Wolf’s law?
A. Graft subsidence
B. Screw pullout
C. Development of kyphosis
D. Stress shielding
E. Dysphagia

Answer 6

A. Graft subsidence
B. Screw pullout
C. Development of kyphosis
D. Stress shielding
E. Dysphagia

Wolf’s law states that bone will form along lines of stress, and alternatively, when normal stress loads are removed, bone will become osteopenic. This is important in fusion surgery as the goal is for bone to heal across the fusion segment. If fixed angle screws are used both above and below the fusion segment, the bone may not be allowed to settle and put stress on the graft(which can lead to higher rates of fusion). If there is no stress on the graft, it is said to be “stress shielded” and the likelihood of fusion decreases. Further Reading: Greenberg. The Handbook of Neurosurgery, 8th Edition, 2016, page 1091.

Question 7

Activated rhodopsin is involved in phototransduction. What downstream effect does activated rhodopsin have?
A. cGMP deactivation, hyperpolarization
B. cGMP activation, depolarization
C. Potassium channel activation, depolarization
D. Potassium channel activation, hyperpolarization
E. Sodium channel activation, depolarization

Answer 7

A. cGMP deactivation, hyperpolarization
B. cGMP activation, depolarization
C. Potassium channel activation, depolarization
D. Potassium channel activation, hyperpolarization
E. Sodium channel activation, depolarization

Activation of rhodopsin is the final pathway in phototransduction. It deactivates cGMP via cGMP phosphodiesterase which has the effect of decreasing sodium ion movement across the cell membrane (occurs through cGMP associated Na channels). Ultimately this leads to hyperpolarization of the photoreceptor, and signal transduction. Further Reading: Citow, Macdonald, Refai. Comprehensive Neurosurgery Board Review, 2nd edition, 2010, page 131. Greenstein B, Greenstein A. Color Atlas of Neuroscience, 2000, page 276

Question 8

Which cortical layer primarily projects back to the thalamus?
A. Layer II
B. Layer III
C. Layer IV
D. Layer V
E. Layer VI

Answer 8

A. Layer II
B. Layer III
C. Layer IV
D. Layer V
E. Layer VI

There are six cortical layers and cortical layer VI is associated projection fibers back to the thalamus. Layer IV receives input from the thalamus and is heavily myelinated in the occipital cortex (known as the stria of Gennari, also giving the name striate cortex). Layer V contains the large pyramidal Betz cells that project to the spinal cord. Further Reading: Citow, Macdonald, Refai. Comprehensive Neurosurgery Board Review, 2nd edition, 2010, pages 32, 123.

Question 9

The Betz cells of the cerebral cortex are located in what layer?
A. External pyramidal
B. External granular
C. Multiform
D. Internal pyramidal
E. Internal granular

Answer 9

A. External pyramidal
B. External granular
C. Multiform
D. Internal pyramidal
E. Internal granular

Betz cells of the cerebral cortex are large pyramidal neurons that project to the spinal cord. They are found in layer V, or the internal pyramidal layer of the cortex. Further Reading: Citow, Macdonald, Refai. Comprehensive Neurosurgery Board Review, 2nd edition, 2010, pages 32, 123.

Question 10

You decide that on your weekend off you would like to build a supercapacitor in your garage, and you need a phase transfer catalyst to make this system work. You choose TEA, tetraethylammonium, as your agent. During the process, you spill it on the floor and inhale large amounts of the fumes. You start to have difficulty breathing and are slowly becoming paralyzed due to the competitive inhibition of acetylcholine receptors. This compound also affects voltage gated receptors in nerve tissue that are associated with what ion?
A. Sodium
B. Potassium
C. Magnesium
D. Chloride

Answer 10

A. Sodium
B. Potassium
C. Magnesium
D. Chloride

TEA is a toxic compound that can lead to ganglionic competitive inhibition of acetylcholine. It also is known to block voltage gated potassium channels in nerve tissue and skeletal muscle. Further Reading: Citow, Macdonald, Refai. Comprehensive Neurosurgery Board Review, 2nd edition, 2010, page 114.

Question 11

Myelination of peripheral nerves leads to what?
A. Increased transmembrane resistance, decreased
capacitance
B. Increased transmembrane resistance, increased
capacitance
C. Decreased transmembrane resistance, increased
capacitance
D. Decreased transmembrane resistance, decreased
capacitance

Answer 11

A. Increased transmembrane resistance, decreased capacitance
B. Increased transmembrane resistance, increased capacitance
C. Decreased transmembrane resistance, increased capacitance
D. Decreased transmembrane resistance, decreased capacitance

Myelination of nerves helps to increase conduction velocity of the action potential. It increases the AP velocity by increasing transmembrane resistance and decreasing membrane capacitance. Further Reading: Citow, Macdonald, Refai. Comprehensive Neurosurgery Board Review, 2nd edition, 2010, page 113

Question 12

A mutation of the gene PTEN is most likely to be seen in the genotyping of what tumor type listed below?
A. Pilocytic astrocytoma
B. WHO grade II glioma
C. Primary GBM
D. Secondary GBM
E. Central neurocytoma

Answer 12

A. Pilocytic astrocytoma
B. WHO grade II glioma
C. Primary GBM
D. Secondary GBM
E. Central neurocytoma

PTEN mutations are often seen in primary glioblastoma rather than low grade gliomas or secondary glioblastoma. For this reason it is helpful when determining if the GBM is primary or is representative of malignant transformation. Further Reading: Gasco, Nader. The Essential Neurosurgery Companion, 2013, page 413

Question 13

Cerebellar mossy fibers synapse in what region?
A. Granular layer
B. Molecular layer
C. Purkinje layer
D. Multiform layer
E. Pyramidal layer

Answer 13

A. Granular layer
B. Molecular layer
C. Purkinje layer
D. Multiform layer
E. Pyramidal layer

The mossy fibers of the cerebellum synapse in the granular layer, and further projections arise from intrinsic cerebellar cortical cells. Only climbing fibers have direct synapses on Purkinje cells. Further Reading: Alberstone, Benzel, Najm, Steinmetz. Anatomic Basis of Neurologic Diagnosis, 2009, page 283.

Question 14

The Schaffer collateral pathway connects what two regions of the hippocampus?
A. Dentate gyrus–CA1
B. CA1–CA3
C. CA3–subiculum
D. CA1–subiculum
E. Dentate gyrus–subiculum

Answer 14

A. Dentate gyrus–CA1
B. CA1–CA3
C. CA3–subiculum
D. CA1–subiculum
E. Dentate gyrus–subiculum

The intrinsic circuitry of the hippocampus is heavily tested. Mossy fibers connect the dentate gyrus to CA3, and the Schaffer collateral pathway interconnects the CA3 and CA1 regions. Further Reading: Alberstone, Benzel, Najm, Steinmetz. Anatomic Basis of Neurologic Diagnosis, 2009, page 342.

Question 15

The perforant pathway of the hippocampus connects what two intrinsic hippocampal structures?
A. Dentate gyrus–CA1
B. CA1–CA3
C. Entorhinal cortex–dentate gyrus
D. CA3–fornix
E. Dentate gyrus–CA1

Answer 15

A. Dentate gyrus–CA1
B. CA1–CA3
C. Entorhinal cortex–dentate gyrus
D. CA3–fornix
E. Dentate gyrus–CA1

The perforant pathway of the hippocampus is the initial limb of the intrinsic hippocampal circuitry. It initiates in the entorhinal cortex and perforates across the subiculum to enter the dentate gyrus. Further Reading: Alberstone, Benzel, Najm, Steinmetz. Anatomic Basis of Neurologic Diagnosis, 2009, page 342.

Question 16

What receptor type is stimulated by neurons that originate in the substantia nigra pars compacta?
A. Glutamate
B. GABA
C. Dopamine
D. Acetylcholine
E. NMDA

Answer 16

A. Glutamate
B. GABA
C. Dopamine
D. Acetylcholine
E. NMDA

The substantia nigra has two nuclei, pars reticulata and pars compacta. The pars compacta projects dopaminergic neurons to the striatum as part of the intrinsic basal ganglia circuitry. Further Reading: Alberstone, Benzel, Najm, Steinmetz. Anatomic Basis of Neurologic Diagnosis, 2009, page 332

Question 17

Cortical projections to the striatum use what neurotransmitter?
A. Glutamate
B. GABA
C. Dopamine
D. Acetylcholine
E. Glycine

Answer 17

A. Glutamate
B. GABA
C. Dopamine
D. Acetylcholine
E. Glycine

The initial projections into the basal ganglia circuitry include motor cortex projections to the striatum. These projections are glutamatergic for both the direct and indirect pathways of the basal ganglia. Further Reading: Alberstone, Benzel, Najm, Steinmetz. Anatomic Basis of Neurologic Diagnosis, 2009, page 332.

Question 18

How many cortical layers are present in the hippocampus?
A. 2
B. 3
C. 4
D. 5
E. 6

Answer 18

A. 2
B. 3
C. 4
D. 5
E. 6

The hippocampus has three layers which is considered archicortex, histologically older cortex than the cerebral cortex. The three layers are the molecular layer, the pyramidal layer, and the polymorphic layer. Further Reading: Alberstone, Benzel, Najm, Steinmetz. Anatomic Basis of Neurologic Diagnosis, 2009, page 340.

Question 19

You are asked to evaluate a patient with an interesting endocrinologic phenomenon. Her body temperature varies with the temperature of her surrounding environment. She most likely has bilateral destruction of what hypothalamic nucleus?
A. Anterior nucleus
B. Posterior nucleus
C. Ventromedial nucleus
D. Supraoptic nucleus
E. Suprachiasmatic nucleus

Answer 19

A. Anterior nucleus
B. Posterior nucleus
C. Ventromedial nucleus
D. Supraoptic nucleus
E. Suprachiasmatic nucleus

This patient is experiencing poikilothermia, or variance of body temperature with surrounding temperature. This is due to bilateral destruction of the posterior thalamic nucleus. Further Reading: Yaşargil, Adamson, Cravens, Johnson, Reeves, Teddy, Valavanis, Wichmann, Wild, Young. Microneurosurgery IV A, 1994, page 268

Question 20

Destruction of the ventromedial nucleus of the thalamus results in what clinical condition?
A. Hyperthermia
B. Anorexia
C. Hyperphagia
D. Diabetes insipidus
E. Addison’s disease

Answer 20

A. Hyperthermia
B. Anorexia
C. Hyperphagia
D. Diabetes insipidus
E. Addison’s disease

The ventromedial nucleus is involved in satiety and when bilaterally damaged, hyperphagia and obesity can occur. This is a known complication of complex craniopharyngioma resection in children and is a feared complication as it is very difficult to control in the postoperative setting. Further Reading: Albright, Pollack, Adelson. Principles and Practice of Pediatric Neurosurgery, 3rd edition, 2015, page 490.

Question 21

Which of the following hypothalamic nuclei is involved with parasympathetic functions?
A. Anterior nucleus
B. Posterior nucleus
C. Lateral nuclei
D. Ventromedial nucleus
E. Supraoptic nucleus

Answer 21

A. Anterior nucleus
B. Posterior nucleus
C. Lateral nuclei
D. Ventromedial nucleus
E. Supraoptic nucleus

The anterior hypothalamus is involved in cooling of the body and parasympathetic functions. The posterior nucleus is involved in sympathetic functions and heating. Further Reading: Alberstone, Benzel, Najm, Steinmetz. Anatomic Basis of Neurologic Diagnosis, 2009, page 324.

Question 22

You are asked by nursing to evaluate a severely agitated and delirious postoperative patient. He is swinging at nursing and very confused. You decide to give a dose of a medication in the butyrophenone class to treat his agitation. This medication works on what subtype of receptors located in the frontal lobe, the hippocampus, and limbic system.
A. GABA
B. Glutamate
C. Serotonin
D. D1
E. D2

Answer 22

A. GABA
B. Glutamate
C. Serotonin
D. D1
E. D2

The medication you are using is haloperidol, a butyrophenone. It antagonizes both D1 and D2 receptors, but the D2 receptors are located in the frontal cortex, the limbic system, and the hippocampus. The D1 receptors are located in the striatum and are responsible for Parkinson-like effects of haloperidol. Further Reading: Citow, Macdonald, Refai. Comprehensive Neurosurgery Board Review, 2nd edition, 2010, page 294.

Question 23

You are seeing a patient with severe, unilateral mydriasis. You suspect that the first-order efferent nerve in this pathway is disrupted. What two structures are connected by the first order neuron in this pathway?
A. Pretectal nucleus – ciliary ganglion
B. Sympathetic chain – ciliary ganglion
C. Hypothalamus – sympathetic chain
D. Hypothalamus – intermediolateral cell column
E. Ciliary ganglion – radial fibers

Answer 23

A. Pretectal nucleus – ciliary ganglion
B. Sympathetic chain – ciliary ganglion
C. Hypothalamus – sympathetic chain
D. Hypothalamus – intermediolateral cell column
E. Ciliary ganglion – radial fibers

Sympathetic innervation of the eye begins in the hypothalamus where first-order neurons project to the intermediolateral cell column. The second-order neuron connects the IML cell column to the superior cervical ganglion, and the third-order neuron connects the superior cervical ganglion to the radial musculature via long ciliary nerves. Further Reading: Citow, Macdonald, Refai. Comprehensive Neurosurgery Board Review, 2nd edition, 2010, page 130

Question 24

You are evaluating a patient in the emergency department with altered mental status, lactic acidosis, and seizures. You suspect cyanide toxicity. What effect does cyanide have on the body?
A. Blocks voltage-gated potassium channel
B. Blocks alpha subunit of acetylcholine receptor
C. Uncouples oxidative phosphorylation
D. Cleaves synaptobrevin
E. Inhibits glycine release in the spinal cord

Answer 24

A. Blocks voltage-gated potassium channel
B. Blocks alpha subunit of acetylcholine receptor
C. Uncouples oxidative phosphorylation
D. Cleaves synaptobrevin
E. Inhibits glycine release in the spinal cord

Cyanide is a toxic compound that abolishes the proton gradient utilized during oxidative phosphorylation in the mitochondria. It leads to severe lactic acidosis and is highly toxic and ingestion is often fatal. Further Reading: Meyers. Differential Diagnosis in Neuroimaging: Brain and Meninges, 2017, page 240. Citow, Macdonald, Refai. Comprehensive Neurosurgery Board Review, 2nd edition, 2010, page

Question 25

The dorsal motor nucleus of the vagus nerve innervates what target organ(s)?
A. Muscles of the larynx and pharynx
B. Thoracic and abdominal viscera
C. Pharyngeal mucosa
D. Aortic arch
E. External ear

Answer 25

A. Muscles of the larynx and pharynx
B. Thoracic and abdominal viscera
C. Pharyngeal mucosa
D. Aortic arch
E. External ear

The vagus nerve has multiple nuclei with different functions. The dorsal motor nucleus of the vagus nerve supplies visceral motor innervation of the thoracic and abdominal viscera, having parasympathetic functions on the gut. Further Reading: Alberstone, Benzel, Najm, Steinmetz. Anatomic Basis of Neurologic Diagnosis, 2009, page 260

Question 26

Cyclic adenosine monophosphate is a second messenger system for what class of recepto
A. Tyrosine kinase
B. Gprotein
C. NMDA
D. Ionotropic

Answer 26

A. Tyrosine kinase
B. Gprotein
C. NMDA
D. Ionotropic

cAMP is a second messenger system within the G-protein receptor pathway. G proteins have three major subunits—alpha, beta, and gamma. The alpha subunit is associated with the interior plasma membrane and usually is the aspect that interacts with the effector enzymes. For G-protein receptors, G proteins are activated after GDP is exchanged for GTP. The G-proteins then stimulate adenylyl cyclase to synthesize cAMP which has downstream effects after it interacts with PKA (cAMP-dependent protein kinase), which in turn phosphorylates serine and threonine residues. Further Reading: Psarros. The Definitive Neurosurgical Board Review, page 5. Greenstein B, Greenstein A. Color Atlas of Neuroscience, 2000.

Question 27

You are working at a neurosurgical clinic in an underdeveloped country. You overhear another physician discussing her patient who drank contaminated water and now has severe diarrhea. The organism has been identified as a vibrio species. You try to remember your basic science days. What receptor protein does the toxin produced by this microbe activate?
A. Gi
B. Gs
C. cAMP
D. IP3

Answer 27

A. Gi
B. Gs
C. cAMP
D. IP3

This patient has cholera, and cholera toxin selectively activates Gs , part of the G-protein signaling pathway. Further Reading: Psarros. The Definitive Neurosurgical Board Review, page 5. Greenstein B, Greenstein A. Color Atlas of Neuroscience, 2000.

Question 28

Lithium selectively inhibits the phosphatases that degrade what second messenger?
A. DAG
B. Phospholipase C
C. Protein kinase C
D. IP3

Answer 28

A. DAG
B. Phospholipase C
C. Protein kinase C
D. IP3

Inositol triphosphate (IP3), is a messenger generated by DAG (along with phospholipase C), and is liberated from the plasma membrane through G-protein coupled messenger systems. IP3 binds receptors in the mitochondria and ER causing Ca2+ to be released within the cytosol of the neuron. Further Reading: Greenstein B, Greenstein A. Color Atlas of Neuroscience, 2000. Psarros. The Definitive Neurosurgical Board Review, page 5.

Question 29

Nitric oxide (NO) is liberated after stimulation of what receptor system?
A. Tyrosine kinase
B. G protein
C. NMDA
D. Ionotropic

Answer 29

A. Tyrosine kinase
B. G protein
C. NMDA
D. Ionotropic

Nitric oxide liberation is a downstream effect of activation of the NMDA receptor signaling mechanism. NO is lipid soluble and in turn stimulates the production of cyclic-GMP. Further Reading: Psarros. The Definitive Neurosurgical Board Review, page 5. Greenstein B, Greenstein A. Color Atlas of Neuroscience, 2000.

Question 30

What ligand would bind to a tyrosine kinase receptor mechanism?
A. Epidermal growth factor
B. Glutamate
C. Benzodiazepine
D. Substance P

Answer 30

A. Epidermal growth factor
B. Glutamate
C. Benzodiazepine
D. Substance P

Tyrosine kinase receptors bind ligands including epidermal growth factor, nerve growth factor, etc. Ultimately, binding of the ligands to this receptor subtype results in phosphorylation of serine and threonine residues. EGF receptor is often seen on high grade glial neoplasms, specifically astrocytic subtypes. Further Reading: Psarros. The Definitive Neurosurgical Board Review, page 5. Greenstein B, Greenstein A. Color Atlas of Neuroscience, 2000.

Question 31

Within an acetylcholine-activated receptor system, what specific subunit binds acetylcholine
A. Alpha
B. Beta
C. Gamma
D. Delta
E. Lambda

Answer 31

A. Alpha
B. Beta
C. Gamma
D. Delta
E. Lambda

The ACh receptor system is comprised of four major subunit types, with five total subunits—two alpha, one beta, one gamma, and one delta. Each alpha subunit binds one molecule of ACh, therefore requiring two molecules to activate the receptor. Further Reading: Psarros. The Definitive Neurosurgical Board Review, page 6. Greenstein B, Greenstein A. Color Atlas of Neuroscience, 2000.

Question 32

You are hiking through Bryce Canyon National Park on your day off and while you are enjoying the beautiful views, you feel a sharp pain in your ankle. You have been bitten by an odd-looking snake that contains alpha-bungarotoxin in its venom. You remember studying this toxin in medical school while you are losing consciousness. What downstream cellular effect is inhibited by alpha-bungarotoxin?
A. Phosphorylation of serine and threonine residues
B. Sodium influx into the cytosol
C. Synthesis of NO
D. Liberation of arachidonic acid from the plasma membrane

Answer 32

A. Phosphorylation of serine and threonine
residues
B. Sodium influx into the cytosol
C. Synthesis of NO
D. Liberation of arachidonic acid from the plasma membrane

Alpha-bungarotoxin inhibits the alpha subunit of ACh receptors and in turn inhibits the influx of sodium into the cytosol. Further Reading: Psarros. The Definitive Neurosurgical Board Review, page 6. Greenstein B, Greenstein A. Color Atlas of Neuroscience, 2000

Question 33

Which of these agents is a depolarizing neuromuscular blocker?
A. Vecuronium
B. D-tubocurarine
C. Succinylcholine
D. Gallamine

Answer 33

A. Vecuronium
B. D-tubocurarine
C. Succinylcholine
D. Gallamine

Succinylcholine is a depolarizing neuromuscular blocking agent often used for intubation during induction of anesthesia. All other listed options are nondepolarizing agents. Further Reading: Psarros. The Definitive Neurosurgical Board Review, page 6. Greenstein B, Greenstein A. Color Atlas of Neuroscience, 2000.

Question 34

G-protein coupled muscarinic receptors are located in what CNS location?
A. Dorsal nucleus of Clarke
B. Onuf’s nucleus
C. Renshaw cells of the spinal cord
D. Lateral geniculate nucleus

Answer 34

A. Dorsal nucleus of Clarke
B. Onuf’s nucleus
C. Renshaw cells of the spinal cord
D. Lateral geniculate nucleus

Muscarinic receptors are G-protein coupled receptors from the metabotropic family. They are inhibited by atropine and scopolamine, and activated by bethanechol and pilocarpine. They are located throughout the CNS, including the cortex, striatum, cerebellum, autonomic nuclei, and Renshaw cells of the spinal cord. Further Reading: Psarros. The Definitive Neurosurgical Board Review, Page 6. Greenstein B, Greenstein A. Color Atlas of Neuroscience, 2000.

Question 35

You are called by the emergency department to evaluate a 34-year-old man with new-onset confusion, high fever, and severe spasticity. You discover after looking at X-rays that he has an intrathecal pump in place. You believe the pump is malfunctioning and he is withdrawing from his medication. What receptor does this me
A. Muscarinic
B. NMDA
C. GABAA
D. GABAB

Answer 35

A. Muscarinic
B. NMDA
C. GABAA
D. GABAB

The patient is suffering from baclofen withdrawal. Baclofen is a GABA agonist that works on the GABAB channel. Picrotoxin inhibits the GABAA receptor. Further Reading: Psarros. The Definitive Neurosurgical Board Review, page 6. Greenstein B, Greenstein A. Color Atlas of Neuroscience, 2000

Question 36

What protein stimulates ACh receptor gene transcription in the muscle fiber ultimately leading to increased concentration of ACh receptors in the NMJ?
A. Rapsyn
B. Agrin
**
D. Muscle-specific tyrosine kinase

Answer 36

A. Rapsyn
B. Agrin
C. Neuregulin
D. Muscle-specific tyrosine kinase

There are a number of proteins that have effects on ACh receptor clustering in the NMJ. Neuregulin is responsible for increasing transcription of ACh receptors from within the muscle fiber, leading to increased concentration of these receptors in the NMJ. Further Reading: Psarros. The Definitive Neurosurgical Board Review, page 10. Greenstein B, Greenstein A. Color Atlas of Neuroscience, 2000.

Question 37

Increased calcium concentration within the muscle cell is mediated by what cellular structure
A. Sarcoplasmic reticulum
B. Endoplasmic reticulum
C. Mitochondria
D. Golgi complex

Answer 37

A. Sarcoplasmic reticulum
B. Endoplasmic reticulum
C. Mitochondria
D. Golgi complex

After an action potential is generated at the NMJ, it propagates throughout the muscle cell and leads to release of Ca2+ from the sarcoplasmic reticulum. Further Reading: Psarros. The Definitive Neurosurgical Board Review, page 11. Greenstein B, Greenstein A. Color Atlas of Neuroscience, 2000.

Question 38

Sarcomeres are connected to one another by what structure?
A. A band
B. H zone
C. Z disk
D. M linee

Answer 38

A. A band
B. H zone
C. Z disk
D. M line

Each sarcomere is connected to another sarcomere at the Z disk. Unfortunately, elements of the sarcomere are often tested on the neurosurgical written boards. Further Reading: Psarros. The Definitive Neurosurgical Board Review, page 11. Greenstein B, Greenstein A. Color Atlas of Neuroscience, 2000.

Question 39

Which area of the sarcomere shortens during muscle contraction?
A. A band
B. H zone
C. Z disk
D. M line

Answer 39

A. A band
B. H zone
C. Z disk
D. M line

During muscle contraction, Ca2+ facilitates crossbridges between actin/myosin fibrils. This leads to shortening of the H zone and the I band, while the A band remains the same size (this is because the actin fibrils move across the myosin fibrils and not the other way around). Further Reading: Psarros. The Definitive Neurosurgical Board Review, page 11. Greenstein B, Greenstein A. Color Atlas of Neuroscience, 2000.

Question 40

Ca2+ binds with what structure to disinhibit actin binding sites, ultimately allowing actin-myosin crossbridges to be made and muscle contraction to occur?
A. Tropomyosin
B. Troponin I
C. Troponin C
D. Troponin T

Answer 40

A. Tropomyosin
B. Troponin I
C. Troponin C
D. Troponin T

Troponin C binds four molecules of Ca2+ within the muscle cell. This causes the troponin/tropomyosin complex to release from the actin fibril. In turn, this allows myosin heads to freely bind actin, forming the crossbridges. Next, myosin, which has ATPase capability, rotates, pulling the actin fibril along its length, leading to muscle contraction. After this is complete, ATP binds myosin which recocks the myosin head, ready to grab the next actin binding site along the fibril. Further Reading: Psarros. The Definitive Neurosurgical Board Review, page 11. Greenstein B, Greenstein A. Color Atlas of Neuroscience, 2000

Question 41

You are evaluating a 40-year-old man who is noticing decreased peripheral vision bilaterally. Visual fields demonstrate bitemporal hemianopia. You appropriately order an MRI (demonstrated below). You obtain blood work and discover the following hormone levels 8 AM cortisol = 12 µg/100 mL Prolactin = 117 ng/mL IGF-1 = 187 ng/mL What is the most likely diagnosis?
A. Prolactinoma
B. Nonfunctioning pituitary adenoma
C. ACTH-producing adenoma
D. GH-producing adenoma

Answer 41

A. Prolactinoma
B. Nonfunctioning pituitary adenoma
C. ACTH-producing adenoma
D. GH-producing adenoma

Imaging demonstrates a pituitary mass, and the lab work is suggestive of a nonfunctioning adenoma. Normal values for 8 AM cortisol are 6 to 14, the IGF-1 levels are within the normal range for a 40 year old (87 to 267), and the prolactin, while elevated (normal 3 to 30), is indicative of stalk effect rather than prolactinoma (> 150, but often much higher). Further Reading: Greenberg. The Handbook of Neurosurgery, 8th edition, pages 733–736.

Question 42

You resected a difficult suprasellar craniopharyngioma. That evening, the nurse pages you because the patient has had very high urine output for several hours in a row. You order a urine specific gravity, and it returns at 1.003. The depleted hormone you are worried about is released from what structure?
A. Pineal gland
B. Organ vasculosum of the lamina terminalis
C. Adenohypophysis
D. Neurohypophysis

Answer 42

A. Pineal gland
B. Organ vasculosum of the lamina terminalis
C. Adenohypophysis
D. Neurohypophysis

This patient has central diabetes insipidus, caused by a lack of secretion of ADH from the posterior pituitary, or neurohypophysis. The diagnosis is made in the setting of consistent, high-volume urine output, dilute urine (specific gravity < 1.005), and increasing sodium levels. Patients can get profoundly dehydrated and may need administration of DDAVP. Further Reading: Greenstein B, Greenstein A. Color Atlas of Neuroscience, 2000

Question 43

You evaluated a patient in the office with a pituitary mass. She is set to undergo transsphenoidal resection. If her pituitary function tests are listed below, what medication should you give in the postoperative period to avoid complications? 8 AM cortisol = 19 µg/100 mL Prolactin = 16 ng/mL IGF-1 = 134 ng/mL
A. Bromocriptine
B. Octreotide
C. DDAVP
D. Hydrocortisone

Answer 43

A. Bromocriptine
B. Octreotide
C. DDAVP
D. Hydrocortisone

This patient has Cushing’s disease, most likely caused by an ACTH-secreting pituitary adenoma. If you are able to get a complete resection, it is important to give hydrocortisone as the patient can suffer an acute Addisonian crisis. Since the pituitary mass has inhibited endogenous production of ACTH, after complete resection, the source of ACTH will be eliminated and the endogenous steroid producing mechanisms have not yet ramped up. The patient will start feeling very nauseated and unwell, and blood pressure will be low. In such a case, 50 mg of IV hydrocortisone should be considered. Further Reading: Greenstein B, Greenstein A. Color Atlas of Neuroscience, 2000.

Question 44

You have resected a pituitary tumor from a patient with these pituitary function tests preoperatively. What lab test should you order on posterative day 1 to determine the success of the procedure? 8 AM cortisol = 9 µg/100 mL Prolactin = 22 ng/mL IGF-1 = 500 ng/mL
A. 8 AM cortisol
B. Sodium
C. Growth hormone
D. IFG-1

Answer 44

A. 8 AM cortisol
B. Sodium
C. Growth hormone
D. IFG-1

This patient has a growth-hormone secreting adenoma and may have features consistent with acromegaly. You should not order IGF-1 in the immediate postoperative period because it is similar to HgbA1c in that it represents levels of growth hormone over an extended period of time. You should order growth hormone to determine success of the surgery, as the levels of GH should respond much more quickly. Further Reading: Greenberg. The Handbook of Neurosurgery, 8th edition, pages 733–736.

Question 45

Which result below distinguishes a patient as having Cushing’s disease versus ectopic ACTH secretion?
A. Random ACTH = 3.4 ng/L
B. 50% reduction in cortisol levels after high dose DMZ suppression test
C. Negative inferior petrosal sinus sampling
D. Negative metyrapone test

Answer 45

A. Random ACTH = 3.4 ng/L
B. 50% reduction in cortisol levels after high dose DMZ suppression test
C. Negative inferior petrosal sinus sampling
D. Negative metyrapone test

Patients with Cushing’s disease will have a random ACTH > 5 ng/L, they will have a 50% or more reduction in cortisol levels after high dose DMZ test, often will have a positive IPS sampling (at least in the textbooks), and will have a positive metyrapone test (rise in 17-OHCS in urine 70% above baseline, or increase in serum 11-deoxycortisol 400-fold above normal). Further Reading: Greenberg. The Handbook of Neurosurgery, 8th edition, page 735

Question 46

What protein is utilized during retrograde axonal transport?
A. Dynamin
B. Dynein
C. Actin/myosin
D. Kinesin

Answer 46

A. Dynamin
B. Dynein
C. Actin/myosin
D. Kinesin

Retrograde axonal transport is considered fast transport, occurring at roughly 400 mm/day. It utilizes ATP and the protein dynein. Further Reading: Psarros. The Definitive Neurosurgical Board Review, page 3. Greenstein B, Greenstein A. Color Atlas of Neuroscience, 2000. Citow, Macdonald, Refai. Comprehensive Neurosurgery Board Review, 2nd edition, 2010, physiology section

Question 47

What protein is utilized during fast anterograde axonal transport?
A. Dynamin
B. Dynein
C. Actin/myosin
D. Kinesin

Answer 47

A. Dynamin
B. Dynein
C. Actin/myosin
D. Kinesin

There are several types of slow anterograde axonal transport that utilize both dynamin and actin/ myosin complexes. Fast anterograde transport utilizes kinesin and ATP, and can cover 400 mm/day. Further Reading: Psarros. The Definitive Neurosurgical Board Review, page 2. Greenstein B, Greenstein A. Color Atlas of Neuroscience, 2000. Citow, Macdonald, Refai. Comprehensive Neurosurgery Board Review, 2nd edition, 2010, physiology section.

Question 48

What drug listed below inhibits fast anterograde axonal transport?
A. Temozolomide
B. Carmustine
C. Vinblastine
D. Cyclophosphamide

Answer 48

A. Temozolomide
B. Carmustine
C. Vinblastine
D. Cyclophosphamide

Vinblastine is a chemotherapeutic agent that has the effect of limiting microtubule formation and function. This has the effect of inhibiting fast anterograde axonal transport as the protein kinesin utilizes microtubules and ATP during fast anterograde axonal transport. Further Reading: Psarros. The Definitive Neurosurgical Board Review, page 2. Greenstein B, Greenstein A. Color Atlas of Neuroscience, 2000. Citow, Macdonald, Refai. Comprehensive Neurosurgery Board Review, 2nd edition, 2010, physiology section

Question 49

What is the only neurotransmitter synthesized within the synaptic vesicle?
A. Acetylcholine
B. Norepinephrine
C. Dopamine
D. Glutamate

Answer 49

A. Acetylcholine
B. Norepinephrine
C. Dopamine
D. Glutamate

Norepinephrine is synthesized from dopamine within the synaptic vesicle by dopamine hydroxylase, and it is the only neurotransmitter synthesized from within the vesicle itself. Further Reading: Psarros. The Definitive Neurosurgical Board Review, page 3. Greenstein B, Greenstein A. Color Atlas of Neuroscience, 2000. Citow, Macdonald, Refai. Comprehensive Neurosurgery Board Review, 2nd edition, 2010, physiology section

Question 50

What is the rate-limiting step for norepinephrine synthesis?
A. Dopamine hydroxylase
B. Aromatic amino acid decarboxylase
C. Tyrosine hydroxylase
D. Choline acetyltransferase

Answer 50

A. Dopamine hydroxylase
B. Aromatic amino acid decarboxylase
C. Tyrosine hydroxylase
D. Choline acetyltransferase

NE synthesis begins with the amino acid tyrosine. It is converted into L-DOPA by tyrosine hydroxylase, the rate-limiting step. Next, aromatic amino acid decarboxylase synthesizes dopamine from L-DOPA, and then dopamine is taken up into synaptic vesicles where dopamine hydroxylase synthesizes NE from dopamine. Further Reading: Psarros. The Definitive Neurosurgical Board Review, page 3. Greenstein B, Greenstein A. Color Atlas of Neuroscience, 2000. Citow, Macdonald, Refai. Comprehensive Neurosurgery Board Review, 2nd edition, 2010, physiology section

Question 51

Serotonergic neurons are located primarily in what brainstem nucleus?
A. Locus ceruleus
B. Raphe nucleus
C. Nucleus basalis of Meynert
D. Periaqueductal gray

Answer 51

A. Locus ceruleus
B. Raphe nucleus
C. Nucleus basalis of Meynert
D. Periaqueductal gray

Serotonergic neurons are located primarily within the raphe nucleus of the brainstem reticular formation. Further Reading: Psarros. The Definitive Neurosurgical Board Review, page 4. Greenstein B, Greenstein A. Color Atlas of Neuroscience, 2000. Citow, Macdonald, Refai. Comprehensive Neurosurgery Board Review, 2nd edition, 2010, physiology section

Question 52

Which neurotransmitter is not considered an amino acid neurotransmitter?
A. Glutamate
B. GABA
C. Glycine
D. Histamine

Answer 52

A. Glutamate
B. GABA
C. Glycine
D. Histamine

Glutamate, GABA, and glycine are amino acid neurotransmitters, while histamine is not. Further Reading: Psarros. The Definitive Neurosurgical Board Review, page 4. Greenstein B, Greenstein A. Color Atlas of Neuroscience, 2000. Citow, Macdonald, Refai. Comprehensive Neurosurgery Board Review, 2nd edition, 2010, physiology section

Question 53

Which neurotransmitter is utilized by Renshaw cells of the spinal cord?
A. Glutamate
B. GABA
C. Glycine
D. Acetylcholine

Answer 53

A. Glutamate
B. GABA
C. Glycine
D. Acetylcholine

Glycine is utilized by inhibitory Renshaw cells of the spinal cord. Further Reading: Psarros. The Definitive Neurosurgical Board Review, page 4. Greenstein B, Greenstein A. Color Atlas of Neuroscience, 2000. Citow, Macdonald, Refai. Comprehensive Neurosurgery Board Review, 2nd edition, 2010, physiology section.

Question 54

The neurotransmitter used by all preganglionic autonomic neurons is synthesized by what enzyme?
A. Dopamine hydroxylase
B. Tyrosine hydroxylase
C. Choline acetyltransferase
D. 5-hydroxytryptophan decarboxylase

Answer 54

A. Dopamine hydroxylase
B. Tyrosine hydroxylase
C. Choline acetyltransferase
D. 5-hydroxytryptophan decarboxylase

Preganglionic autonomic neurons all utilize acetylcholine as their neurotransmitter, and acetylcholine is synthesized by the enzyme choline acetyltransferase. Further Reading: Psarros. The Definitive Neurosurgical Board Review, page 4. Greenstein B, Greenstein A. Color Atlas of Neuroscience, 2000. Citow, Macdonald, Refai. Comprehensive Neurosurgery Board Review, 2nd edition, 2010, physiology sectio

Question 55

Acetylcholine is the primary neurotransmitter of what nucleus?
A. Locus coeruleus
B. Raphe nucleus
C. Substantia nigra
D. Nucleus basalis of Meynert

Answer 55

A. Locus coeruleus
B. Raphe nucleus
C. Substantia nigra
D. Nucleus basalis of Meynert

The nucleus basalis of Meynert is located in the basal forebrain and contains connections throughout the cerebrum. Its primary neurotransmitter is ACh, and ACh has been found to be depleted in patients with dementia. Thus, pharmacologic management of dementia is focused largely on increasing levels of ACh within the cerebrum. Further Reading: Psarros. The Definitive Neurosurgical Board Review, page 3. Greenstein B, Greenstein A. Color Atlas of Neuroscience, 2000. Citow, Macdonald, Refai. Comprehensive Neurosurgery Board Review, 2nd edition, 2010, physiology section.

Question 56

What cell structures make up the blood−brain barrier?
A. Astrocytic foot processes
B. Endothelial tight junctions
C. Neuronal cell plasma membrane
D. Myelin

Answer 56

A. Astrocytic foot processes
B. Endothelial tight junctions
C. Neuronal cell plasma membrane
D. Myelin

The blood–brain barrier (BBB) is composed primarily of endothelial cell tight junctions. While astrocytic foot processes are involved with transport of molecules across the BBB, they stimulate the endothelial cells to form the BBB. Further Reading: Psarros. The Definitive Neurosurgical Board Review, page 1. Greenstein B, Greenstein A. Color Atlas of Neuroscience, 2000. Citow, Macdonald, Refai. Comprehensive Neurosurgery Board Review, 2nd edition, 2010, physiology section.

Question 57

This cell of the CNS from mesodermal origin is activated during infection/inflammation and is primarily phagocytic in function
A. Fibrous astrocyte
B. Bergmann cell
C. Protoplasmic astrocyte
D. Microglia

Answer 57

A. Fibrous astrocyte
B. Bergmann cell
C. Protoplasmic astrocyte
D. Microglia

Microglia are glial cells of the CNS that are involved in phagocytosis and antigen presentation within the CNS. They are from mesodermal origin. Further Reading: Psarros. The Definitive Neurosurgical Board Review, page 1. Greenstein B, Greenstein A. Color Atlas of Neuroscience, 2000. Citow, Macdonald, Refai. Comprehensive Neurosurgery Board Review, 2nd edition, 2010, physiology section.

Question 58

Which segment of the neuron does not contain Nissl substance?
A. Dendrite
B. Cytoplasm
C. Axon hillock
D. Presynaptic terminal

Answer 58

A. Dendrite
B. Cytoplasm
C. Axon hillock
D. Presynaptic terminal

Nissl substance is a granular body of the cell containing rough endoplasmic reticulum and ribosomes involved in protein synthesis. The axon hillock does not contain Nissl substance and it is the most excitable region of the axon owing to the fact that it has the highest concentration of sodium channels. Further Reading: Psarros. The Definitive Neurosurgical Board Review, page 1. Greenstein B, Greenstein A. Color Atlas of Neuroscience, 2000. Citow, Macdonald, Refai. Comprehensive Neurosurgery Board Review, 2nd edition, 2010, physiology section

Question 59

Substance P is synthesized solely in what location?
A. Endoplasmic reticulum
B. Golgi complex
C. Synaptic vesicle
D. Cytoplasm

Answer 59

A. Endoplasmic reticulum
B. Golgi complex
C. Synaptic vesicle
D. Cytoplasm

There are two major classes of neurotransmitters, small molecule neurotransmitters and neuroactive peptides. Small molecule neurotransmitters (dopamine, NE, histamine, etc.) are synthesized throughout the neuron, while the larger neuroactive peptides (substance Page, enkephalins) are synthesized solely from within the endoplasmic reticulum. Further Reading: Psarros. The Definitive Neurosurgical Board Review, page 4. Greenstein B, Greenstein A. Color Atlas of Neuroscience, 2000. Citow, Macdonald, Refai. Comprehensive Neurosurgery Board Review, 2nd edition, 2010, physiology section.

Question 60

You are finishing your basement and you see a rusty nail in the corner. You are concerned someone will step on the nail and get a bacterial infection that can have CNS effects. The toxin released by this microbe has what effect on neuron function?
A. Cleavage of v-SNAREs causing inhibition of
synaptic transmission
B. Cleavage of synaptobrevin causing inhibition of synaptic transmission
C. Microtubule dysfunction inhibiting fast anterograde
transport
D. Neuronal apoptosis

Answer 60

A. Cleavage of v-SNAREs causing inhibition of synaptic transmission
B. Cleavage of synaptobrevin causing inhibition of synaptic transmission
C. Microtubule dysfunction inhibiting fast anterograde transport
D. Neuronal apoptosis

The synaptic vesicle uses several proteins to fuse with the active zone of the presynaptic terminal. One of these proteins, synaptobrevin, is inhibited by tetanus toxin leading to inhibition of synaptic transmission. Botulinum toxin inhibits v-SNAREs with the same effect. Microtubule dysfunction is caused by certain chemotherapeutics, including vinblastine. Further Reading: Psarros. The Definitive Neurosurgical Board Review, page 5. Greenstein B, Greenstein A. Color Atlas of Neuroscience, 2000. Citow, Macdonald, Refai. Comprehensive Neurosurgery Board Review, 2nd edition, 2010, physiology section.

Question 61

Which region of the hippocampus is a site of neurogenesis?
A. CA1
B. CA3
C. Subgranular layer
D. Entorhinal cortex

Answer 61

A. CA1
B. CA3
C. Subgranular layer
D. Entorhinal cortex

There are two known sites of neurogenesis in the adult brain, the subependymal zone in the lateral ventricle (neurons and glia are generated and migrate to the olfactory bulb), as well as the subgranular layer of the dentate gyrus within the hippocampus. Further Reading: Psarros. The Definitive Neurosurgical Board Review, page 5. Greenstein B, Greenstein A. Color Atlas of Neuroscience, 2000. Citow, Macdonald, Refai. Comprehensive Neurosurgery Board Review, 2nd edition, 2010, physiology section.

Question 62

Which axon type will have the fastest conductance?
A. Large, unmyelinated
B. Large, myelinated
C. Small, unmyelinated
D. Small, myelinated

Answer 62

A. Large, unmyelinated
B. Large, myelinated
C. Small, unmyelinated
D. Small, myelinated

Neurons are capable of transmitting action potentials from 0.2 to 120 m/sec depending on the structure of the axon. Myelin increases the speed of conductance, but axon size plays a role. From Psarros: “The velocity of action potential transmission increases with increased axonal diameter, increased transmembrane resistance, decreased internal resistance and decreased membrane capacitance.” Further Reading: Psarros. The Definitive Neurosurgical Board Review, page 9. Greenstein B, Greenstein A. Color Atlas of Neuroscience, 2000. Citow, Macdonald, Refai. Comprehensive Neurosurgery Board Review, 2nd edition, 2010, physiology section.

Question 63

Which sensory axon type has the fastest conduction?
A. Primary muscle spindle afferents
B. Cutaneous touch afferents
C. Temperature afferents
D. Pain afferents

Answer 63

A. Primary muscle spindle afferents
B. Cutaneous touch afferents
C. Temperature afferents
D. Pain afferents

Type Ia and Ib fibers (spindle cell afferents and Golgi afferents, respectively) have the fastest conduction among sensory axons at 70 to 120 m/s. Further Reading: Psarros. The Definitive Neurosurgical Board Review, page 9. Greenstein B, Greenstein A. Color Atlas of Neuroscience, 2000. Citow, Macdonald, Refai. Comprehensive Neurosurgery Board Review, 2nd edition, 2010, physiology section.

Question 64

What nerve type violates the Bell-Magendie law?
A. Type Ia
B. Type III
C. B fibers
D. C fibers

Answer 64

A. Type Ia
B. Type III
C. B fibers
D. C fibers

The Bell-Magendie law states that all sensory fibers enter the spinal cord through the dorsal root. C fibers transmit pain and temperature sensation from the pelvic viscera through the ventral root. Their cell bodies are still located within the dorsal root ganglion, like other sensory fibers. These C fibers are only found at L5-S3. Further Reading: Psarros. The Definitive Neurosurgical Board Review, page 10. Greenstein B, Greenstein A. Color Atlas of Neuroscience, 2000. Citow, Macdonald, Refai. Comprehensive Neurosurgery Board Review, 2nd edition, 2010, physiology section.

Question 65

Which of these sensory receptors exhibits rapid adaptation?
A. Merkel disk
B. Meissner’s corpuscles
C. Ruffini endings
D. Golgi tendon organs

Answer 65

A. Merkel disk
B. Meissner’s corpuscles
C. Ruffini endings
D. Golgi tendon organs

Meissner’s corpuscles transmit skin flutter and are rapid adapters. Merkel disks transmit pressure and have slow adaptation. Ruffini endings sense strength and have slow adaptation. Further Reading: Psarros. The Definitive Neurosurgical Board Review, page 10. Greenstein B, Greenstein A. Color Atlas of Neuroscience, 2000. Citow, Macdonald, Refai. Comprehensive Neurosurgery Board Review, 2nd edition, 2010, physiology section.

Question 66

Which blood–brain barrier transport mechanism is energy independent?
A. L system
B. MDR system
C. Glut-1 system
D. Active transport system

Answer 66

A. L system
B. MDR system
C. Glut-1 system
D. Active transport system

Glut-1 is responsible for transferring glucose across the BBB along its gradient. It is an energy-independent transport mechanism. Further Reading: Psarros. The Definitive Neurosurgical Board Review, page 18. Greenstein B, Greenstein A. Color Atlas of Neuroscience, 2000. Citow, Macdonald, Refai. Comprehensive Neurosurgery Board Review, 2nd edition, 2010, physiology section.

Question 67

What is considered to be normal blood flow to the brain?
A. 30 cc/100 g/min
B. 50 cc/100 g/min
C. 70 cc/100 g/min
D. 90 cc/100 g/min

Answer 67

A. 30 cc/100 g/min
B. 50 cc/100 g/min
C. 70 cc/100 g/min
D. 90 cc/100 g/min

Normal blood flow to the brain is considered to be 50 cc per 100 g of tissue per minute. Due to autoregulation at the capillary level, the brain is able to maintain this rate of blood flow through a wide variation in systolic blood pressure. Further Reading: Psarros. The Definitive Neurosurgical Board Review, page 18. Greenstein B, Greenstein A. Color Atlas of Neuroscience, 2000. Citow, Macdonald, Refai. Comprehensive Neurosurgery Board Review, 2nd edition, 2010, physiology section.

Question 68

At what rate of diminished blood flow is electrical failure observed?
A. 12 cc/100 g/min
B. 18 cc/100 g/min
C. 24 cc/100 g/min
D. 30 cc/100 g/min

Answer 68

A. 12 cc/100 g/min
B. 18 cc/100 g/min
C. 24 cc/100 g/min
D. 30 cc/100 g/min

Normal blood flow to the brain is considered to be 50 cc per 100 g of tissue per minute. Electrical failure occurs when blood flow falls to 18 cc/100 g/ min or below. Further Reading: Psarros. The Definitive Neurosurgical Board Review, page 18. Greenstein B, Greenstein A. Color Atlas of Neuroscience, 2000. Citow, Macdonald, Refai. Comprehensive Neurosurgery Board Review, 2nd edition, 2010, physiology section

Question 69

During cerebral ischemia, glutamate is released and a subsequent increase in cytosolic Ca2+ is observed. If the Ca2+ concentration reaches high enough levels, what enzyme is activated leading to cell damage?
A. Fas ligand
B. Dopamine decarboxylase
C. Phospholipase C
D. Caspase 9

Answer 69

A. Fas ligand
B. Dopamine decarboxylase
C. Phospholipase C
D. Caspase 9

During cerebral ischemia, glutamate is released, causing influx of Na into the neuron. This results in cerebral edema and influx of Ca2+. If the Ca2+ levels are high enough, activation of phospholipase C occurs and further cell damage occurs, ultimately leading to apoptosis. Further Reading: Psarros. The Definitive Neurosurgical Board Review, page 18. Greenstein B, Greenstein A. Color Atlas of Neuroscience, 2000. Citow, Macdonald, Refai. Comprehensive Neurosurgery Board Review, 2nd edition, 2010, physiology section.

Question 70

The resting membrane potential of the neuron is −60 to −70 mV. This is closest to the equilibrium potential of what ion?
A. Na+
B. K+
C. Ca2+
D. Cl−

Answer 70

A. Na+
B. K+
C. Ca2+
D. Cl−

The resting membrane potential of the neuron is determined by diffusion of Na, K, and Cl ions across the plasma membrane. Each has its own equilibrium potential. Due to a much larger concentration of K+ channels open during the resting state and a resultant increased movement of K+ ions, the membrane potential is closest to that of K+ (−75 mV). Further Reading: Psarros. The Definitive Neurosurgical Board Review, page 7. Greenstein B, Greenstein A. Color Atlas of Neuroscience, 2000. Citow, Macdonald, Refai. Comprehensive Neurosurgery Board Review, 2nd edition, 2010, physiology section.

Question 71

. A miniature end plate potential requires release of roughly how many molecules of ACh?
A. 10,000 molecules
B. 100,000 molecules
C. 1,000,000 molecules
D. 10,000,000 molecules

Answer 71

A. 10,000 molecules
B. 100,000 molecules
C. 1,000,000 molecules
D. 10,000,000 molecules

Each synaptic vesicle contains a specific amount of neurotransmitters referred to as 1 quantum. For ACh, this is roughly 10,000 molecules. In the neuromuscular junction, only 1 quantum of ACh is required to generate an MEPP. This will not result in depolarization of the muscle cell, however. Further Reading: Psarros. The Definitive Neurosurgical Board Review, page 4. Greenstein B, Greenstein A. Color Atlas of Neuroscience, 2000. Citow, Macdonald, Refai. Comprehensive Neurosurgery Board Review, 2nd edition, 2010, physiology section.

Question 72

The only monosynaptic reflex in the body is mediated by what type of sensory fibers?
A. Ia
B. Ib
C. II
D. IV

Answer 72

A. Ia
B. Ib
C. II
D. IV

The muscle stretch reflex is the only monosynaptic reflex in the body and it is mediated by muscle spindles and Ia sensory fibers. Further Reading: Psarros. The Definitive Neurosurgical Board Review, page 12. Greenstein B, Greenstein A. Color Atlas of Neuroscience, 2000. Citow, Macdonald, Refai. Comprehensive Neurosurgery Board Review, 2nd edition, 2010, physiology section.

Question 73

What sensory fiber has the slowest conductance?
A. I
B. II
C. III
D. IV

Answer 73

A. I
B. II
C. III
D. IV

Type IV sensory fibers (slow/burning pain and some temperature from cutaneous free nerve endings) have the slowest conductance, at 0.4 to 2 m/s. Further Reading: Psarros. The Definitive Neurosurgical Board Review, page 10. Greenstein B, Greenstein A. Color Atlas of Neuroscience, 2000. Citow, Macdonald, Refai. Comprehensive Neurosurgery Board Review, 2nd edition, 2010, physiology section

Question 74

The structure involved in spinal reflexes that is in series with muscle cells utilizes what sensory fibers?
A. Ia
B. Ib
C. III
D. IV

Answer 74

A. Ia
B. Ib
C. III
D. IV

Golgi tendon organs are located in series with muscle cells (as opposed to muscle spindles which are organized in parallel). GTOs function to detect muscle tension at the muscle/tendon interface. They transmit via Ib sensory fibers. Further Reading: Psarros. The Definitive Neurosurgical Board Review, page 12. Greenstein B, Greenstein A. Color Atlas of Neuroscience, 2000. Citow, Macdonald, Refai. Comprehensive Neurosurgery Board Review, 2nd edition, 2010, physiology section.

Question 75

Catechol-O-methyl transferase (COMT) metabolizes what neurotransmitter?
A. Acetylcholine
B. Serotonin
C. Norepinephrine
D. Dopamine

Answer 75

A. Acetylcholine
B. Serotonin
C. Norepinephrine
D. Dopamine

COMT and MAO (monoamine oxidase) both metabolize norepinephrine in the cytosol of cells. These enzymes are inhibited by selegiline. Further Reading: Psarros. The Definitive Neurosurgical Board Review, page 3. Greenstein B, Greenstein A. Color Atlas of Neuroscience, 2000. Citow, Macdonald, Refai. Comprehensive Neurosurgery Board Review, 2nd edition, 2010, physiology section.