b. Lemniscus, fasciculus, and peduncle all refer to white matter structures, leaving putamen as the logical choice. The putamen is in fact a large nucleus that is part of the basal ganglia.

a. The lenticular nucleus is a major component of the basal ganglia, located subcortically in each cerebral hemisphere (see Fig. 1.1 and Table 1.1 ).

c. The midbrain, pons, and medulla are the three subdivisions of the brainstem (see Fig. 1.1 and Table 1.1 ).

b. The thalamus and hypothalamus are the major components of the diencephalon (see Fig. 1.1 and Table 1.1 ).

a. The amygdala, a major component of the limbic system, is located beneath the medial surface of the temporal lobe (see Fig. 1.1 and Table 1.1 ).

e.

f.

c.

b. Specialized ependymal cells form a secretory epithelium and produce cerebrospinal fluid (CSF). See Fig. 5.2 .

f.

e. Kinesin and dynein move organelles along microtubules during fast transport.

c. Although synaptic contacts can occur anyplace on a neuron, dendrites are the principal site.

g. Nissl bodies are large clumps of rough endoplasmic reticulum.

b. Although any part of a neuron can be presynaptic in some places, the most common synapses are from axon terminals onto dendrites.

c. Microglia develop from mesoderm.

d. The others are all demyelinating diseases.

a. The “locked in” state is characteristic of damage to the pons of the brainstem.

b. Defective closure of the neural tube causes malformation of overlying bones. If the rostral neuropore fails to close, anencephaly can result, as in this case.

a. Neural crest cells give rise to the PNS, including autonomic ganglion cells (see Fig. 2.2 ).

e. The skull and face were normal and the cerebral hemispheres present, indicating proper neural tube closure and differentiation of the telencephalon and diencephalon from the prosencephalon. This malformation most likely occurred later in development.

b. See Fig. 2.1 .

c. This is the only PNS element among the listed options. (Even though the axons of motor neurons travel through the periphery, their cell bodies reside in the CNS where they were formed.)

c. See Fig. 2.5 .

a. See Fig. 2.5 .

e. See Fig. 2.5 .

b. See Fig. 2.5 .

a. See Fig. 2.5 .

e. See Fig. 2.5 .

d. See Fig. 2.5 .

c. See Fig. 2.5 .

a. See Fig. 2.5 .

a. Open neural tubes allow alpha-fetoprotein to leak out into amniotic fluid or maternal serum.

c. Postcentral gyrus.

h. Continues over onto the medial surface of the hemisphere.

c. Postcentral gyrus, behind the central sulcus.

e. Visual cortex is located above and below the calcarine sulcus.

f. The most medial gyrus of the temporal lobe (actually part of the limbic lobe).

h. Between the midbrain (g) and medulla (i). Large basal portion protrudes anteriorly.

d. Posterior enlargement, containing occipital and some parietal and temporal fibers.

c. The fornix.

f. The thalamus.

e. The hypothalamus.

b. Cortex buried in the lateral sulcus.

c. Putamen + globus pallidus.

f. A midline structure by the 3rd ventricle.

c. The lenticular nucleus.

d. Cortical layer folded into the limbic lobe.

c. Primary afferents have their cell bodies in places like peripheral ganglia and terminate in the CNS uncrossed.

b. Because motor neurons almost always project ipsilaterally, a is unlikely. In fact, as explained in Chapter 12 , the explanation proposed in b is correct.

b. See Fig. 3.8 .

d. Cerebellar damage does not cause sensory deficits; it causes an ipsilateral movement disorder.

d. See Fig. 3.10 .

a. Meningeal arteries reside in the periosteal part of the cranial dura, and tears in these arteries can cause separation of the dura from the cranium. See Fig. 4.4 .

b. The cranial dura is attached to the skull externally and the arachnoid internally, so there is no real epidural or subdural space. The pia mater, on the other hand, is attached to the surface of the CNS, leaving a subarachnoid space between itself and the arachnoid. See Fig. 4.1 .

a. The name “dura” is derived from the Latin word for hard or tough (as in durable), describing this thick, collagenous membrane. The arachnoid and pia are much more delicate.

a. The cingulate gyrus, just above the corpus callosum, is adjacent to the falx cerebri.

b. The uncus of the temporal lobe can be pushed down under the tentorium and push into the midbrain of the brainstem. a. The cingulate gyrus herniates under the falx cerebri. c. Tentorium cerebelli separates the cerebellum from the brainstem. d. The cerebellar tonsils herniate through the foramen magnum.

b. Cells in a particular layer of the arachnoid are connected to each other by bands of tight junctions, forming a diffusion barrier. See Figs. 4.1 and 6.5 .

c. Arachnoid villi act like holes in the arachnoid barrier layer, allowing passive movement of CSF into dural venous sinuses (see Fig. 4.2 ).

c. The meningeal suspension system is made necessary by the lack of rigidity of the CNS.

a. The spinal dura has no periosteal component, so there is a space between the spinal dura and the periosteum of the vertebrae (see Fig. 4.3 ).

c. Uncal herniation pushes into the midbrain of the brainstem, often putting pressure onto cranial nerve (CN) III, resulting in a loss of function and a dilated pupil.

c. These are epidural bleeds that take on a lens shape and cannot move across the bony sutures due to the dura tightly attached in these areas. Subdural bleeds are often crescent-shaped and cannot cross the dura deflections between the cerebral hemispheres or the cerebellar cavity.

The right lateral ventricle would expand in this case of noncommunicating hydrocephalus. Remaining parts of the ventricular system would be OK because they still communicate with subarachnoid space and arachnoid villi.

b. Conventional CT produces maps of X-ray density, so bone is lightest and air is darkest.

d. See Fig. 3.6 .

d. The median aperture and the two lateral apertures are openings in the fourth ventricle and are the routes through which the ventricular system communicates with subarachnoid space.

a. Choroid plexus is found in all four ventricles. However, in each lateral ventricle it grows as a single C-shaped strand extending from the inferior horn through the body and then growing through the interventricular foramen. None grows in the anterior horn of the lateral ventricle.

c. Choroid epithelial cells are joined to one another by tight junctions, forming a diffusion barrier.

d. The choroid epithelium is a layer of ependymal cells specialized as a secretory epithelium. Substances that leak across the endothelial and pial layers of the choroid plexus are then actively transported across the choroid epithelium (see Fig. 5.2 ).

Arachnoid villi are the principal routes through which CSF reaches the venous system, and most are located in the walls of the superior sagittal sinus. Anterior occlusions allow CSF to reach most of the villi, but posterior occlusions effectively block this normal route of CSF circulation.

d. Gray matter, white matter, and CSF have opposite appearances in T1- and T2-weighted images. Bone and air produce little signal in either image type because of the lack of protons (see Fig. 5.6 ).

b. The T2-weighted images are opposite to T1. T2-weighted are often used to identify pathological findings.

a.

e. b. and c. both block normal CSF circulation and cause hydrocephalus; in both cases at least part of the ventricular system is cut off from subarachnoid space. a. also blocks CSF flow and causes hydrocephalus, but in this case the entire ventricular system is still in communication with subarachnoid space; hence, a. would cause communicating hydrocephalus.

c. The choroid plexus contains choroid epithelium, while the inner layer of the arachnoid membrane contains neuroectoderm-derived cells that both contain tight junctions preventing substances from passing between cells. The choroid capillaries are leaky, allowing substances to move towards and into the choroid epithelium but not between the epithelium. The pia mater, lacking tight junctions, does not constitute a barrier.

d. The blockage of the ventricular system anywhere prior to CSF leaving the brainstem is considered noncommunicating hydrocephalus. a. Chiari malformations are the movement of the cerebellar tonsils into the foramen magnum. b. Communicating hydrocephalus is due to blockage of fluid middle outside of the ventricular system from reaching and entering into the dura venous system. c. Dural meningeal swelling is seen as typically a benign tumor called a meningioma, slow-growing outside the ventricular system. e. Uncal herniation under the tentorium often causes a loss of cranial nerve III function.

d. Normal cranial nerves indicate the brainstem was probably not affected, eliminating the vertebral artery. Normal visual fields indicate the occipital lobes were probably not affected, eliminating the posterior cerebral artery. The anterior cerebral artery does not supply cortical areas dealing with the face and arm, leaving the middle cerebral artery as the culprit.

c. The vertebral and posterior inferior cerebellar arteries contribute to the supply of the medulla, the superior cerebellar and posterior cerebral arteries to the rostral pons and midbrain (see Fig. 6.3 ).

e. The basilar artery has penetrating arteries that feed midline structures of the pons and the caudal midbrain (see Fig. 6.3 ).

b. The vertebral arteries contribute to the midline structures of the medulla while the posterior inferior cerebellar arteries, on their way to the cerebellum, supply the lateral parts of the medulla.

a. The anterior cerebral artery and its branches parallel the corpus callosum, supplying the cingulate gyrus and the medial surface of the frontal and parietal lobes (see Fig. 6.2 ).

a. split between anterior and middle cerebral.

• b.
  

  anterior cerebral.

  
  
• c.
  

  middle cerebral artery

  
  
• d.
  

  some middle cerebral, but mostly posterior cerebral.

  
  
• e.
  

  mostly posterior cerebral and superior cerebellar.

  
  
• f.
  

  (also a little from the anterior cerebral.)

  
  
• g.
  

  (also a little from the anterior cerebral.)

  
  
• h.
  

  posterior cerebral.

There might be no effect in either case because, under normal circumstances, little blood flows through either artery. If perforating branches of one or both communicating arteries were involved, some deficits due to diencephalic damage might be noted.

c. See Fig. 6.4 .

d. On its way to the occipital lobe, the posterior cerebral artery supplies medial and inferior parts of the temporal lobe (see Fig. 6.2 ).

b. Distal branches of the middle cerebral artery are distributed to the lateral surface of the hemisphere and feed into the system of superficial veins (see Fig. 6.6 ). The internal cerebral vein is part of the system of deep veins.

c. See Fig. 6.5 . Choroidal capillaries, unlike usual CNS capillaries, are fenestrated; the pia mater is freely permeable at all locations.

a. Autoregulation keeps the total blood flow to the brain relatively constant. Local metabolic changes result in increased flow to active areas balanced by decreased flow to relatively inactive areas.

b. An ischemic infarct can begin to resolve over time, allowing some bleeding back into the damaged area. Collaterals from adjacent nondamaged areas may bleed into the damaged area.

a. Basal ganglia are prone to lacunar infarcts due to the small-diameter blood vessels that come off the larger internal carotid or middle cerebral arteries, allowing small emboli to pass though the larger vessels but to get caught in the smaller vessels that penetrate and supply the basal ganglia and internal capsule.

d. Subarachnoid bleeds often present symptom-wise as “worst headache ever.”

a. Closing K ⁺ channels would increase the relative permeability of the membrane to Na ⁺ , so the membrane potential would move closer to V _Na .

b. Closing Na ⁺ channels would increase the relative permeability of the membrane to K ⁺ , so the membrane potential would move closer to V _K . (In typical neurons this would be a very small hyperpolarization because there is not much Na ⁺ permeability to begin with and the membrane potential is already close to V _K .)

a. This would move V _Na to a more positive value. Because the membrane potential is a weighted average between V _K and V _Na , a small depolarization would result.

b. This would move V _K to a more negative value. Because the membrane potential is a weighted average between V _K and V _Na , hyperpolarization would result.

a. Lack of pumping would allow the Na ⁺ and K ⁺ concentration gradients to dissipate, moving the membrane potential to or toward 0 mV.

a. A large diameter makes it easier for current to travel down the dendrite, and few open channels make it harder for current to leave; both factors increase the length constant.

b. Lowered V _Na , lowered peak of the action potential.

a. Prolonged action potential, lack of an afterhyperpolarization.

c. Prolonged action potential, but an afterhyperpolarization is still present, indicating the opening of K ⁺ channels.

c. Both larger diameter and the presence of myelin increase conduction velocity.

c. Local anesthetics block the voltage-gated sodium channel pores. Aspirin is a nonsteroidal antiinflammatory drug (NSAID). Carbamazepine and valproic acid, used as anticonvulsants and mood stabilizers, prolong the inactivated state of the voltage-gated sodium channels but do not block the channels. Retigabine, used as an anticonvulsant, prolongs the opening of voltage-gated potassium channels.

c. Cocaine has an added function of blocking the reuptake of norepinephrine, resulting in vasoconstriction. Cocaine will also block the reuptake of dopamine, causing euphoria, resulting in the illegal recrea­tional use.

c. All others, depending on dose, may cause terato­genicity.

a. See Table 8.1 .

d. Neuropeptides are synthesized and packaged in the cell body, then shipped down the axon; small-molecule transmitters are synthesized by soluble enzymes in synaptic endings.

a. Acetylcholine is the major PNS excitatory transmitter, in this case acting at nicotinic receptors.

f. GABA is the principal CNS inhibitory transmitter.

a. Acetylcholine is the major PNS excitatory transmitter, here again acting at nicotinic receptors.

e. Glutamate is the major excitatory transmitter in the CNS, used at something like 90% of CNS synapses.

f. GABA is the principal CNS inhibitory transmitter.

b. Degeneration of the pigmented, dopaminergic neurons of the substantia nigra (compact part) causes Parkinson disease (see Fig. 11.9 and Chapter 19 ).

e. Glutamate is the principal CNS excitatory transmitter.

d. Raphe nuclei are found throughout the midline of the entire brainstem and contain serotonin.

c. Locus ceruleus nuclei are mainly found in the rostral pons and contain norepinephrine.

c. With few exceptions, postsynaptic effects are not mediated by voltage-gated channels. Of the ligand-gated channels listed, only the opening of a Na ⁺ /K ⁺ channel would cause depolarization.

b. Ethosuximide blocks T-type calcium channels, high concentration in the thalamus. Entacapone inhibits catechol-O-methyltransferase, desipramine is a tricyclic antidepressant that blocks reuptake of norepinephrine and serotonin, selegiline inhibits monoamine oxidase, and tetrabenazine blocks the vesicular reuptake of dopamine resulting in dopamine depletion.

a. Bupropion not only blocks reuptake of norepinephrine and serotonin but also dopamine, and is often used when individuals no longer find enjoyment in things. Edrophonium inhibits acetylcholinesterase and is used for myasthenia gravis. Fluoxetine and paroxetine block reuptake of serotonin only. Selegiline inhibits monoamine oxidase.

c. Myasthenia gravis.

c. Pyridostigmine inhibits acetylcholinesterase, therefore increasing levels of acetylcholine. Botulinum toxin inhibits the release of acetylcholine, desipramine is a tricyclic antidepressant inhibiting the reuptake of norepinephrine and serotonin, tetrabenazine blocks the vesicular reuptake of dopamine, and tolcapone blocks catechol-O-methyltransferase.

d. Refers to characteristics of the individual receptor that could be depolarizing or hyperpolarizing and does not have to be the largest possible response. Does not have to increase the rate of action potentials.

e. Receptor potentials spread electrotonically, like postsynaptic potentials.

b. Notice that the receptor responds vigorously while the stimulus is changing but stops responding when the stimulus is constant.

b. See Fig. 9.5 .

b. Stimulating gamma motor neurons causes contraction of the ends of intrafusal fibers. This in turn stretches the central part of the intrafusal fibers, where the stretch receptor endings are applied, and makes the primary afferents fire faster.

a., c.

e. Kind of a trick question, but most touch receptors are medium diameter and many are thinly myelinated or unmyelinated.

a., c.

b., d. Although some are thinly myelinated, many are unmyelinated.

b., d.

c. The epineurium is continuous with the dura mater and shares its mechanical strength.

c. The perineurium is continuous with the arachnoid and contains a continuation of the arachnoid barrier layer.

c. Muscle spindles detect static and dynamic activity of skeletal muscle.

a. Muscle stretch is detected by spindle fibers that are innervated by type Ia fibers (large in diameter and myelinated). Pain and temperature are detected by c-fibers that are small and nonmyelinated. Visceral detection is performed by small unmyelinated fibers. Touch is mediated by A-beta fibers that are medium in diameter and myelinated but less than Ia fibers.

b. Allodynia is defined as normally nonnoxious stimuli being perceived as painful.