All Questions: 271-300

Correct answer: C

Neurotransmitters are stored in small membrane-bound sacs called synaptic vesicles, which cluster in the presynaptic axon terminal. When an action potential arrives, calcium influx triggers vesicle fusion with the presynaptic membrane, releasing neurotransmitters into the synaptic cleft.

Correct answer: B

Allodynia is pain triggered by a stimulus that does not normally cause pain, such as light touch, mild pressure, or gentle temperature changes. It often occurs in conditions where the nervous system becomes sensitized and misinterprets non-painful input as painful.

Correct answer: C

Ketamine and norketamine act as antagonists at the NMDA receptor, which means that they block the receptor and inhibit activity there. This action alone does not seem to be capable of fully explaining ketamine's antidepressant effects, but it is the main mechanism of the drug, and it may lead to downstream effects (e.g., new synapse formation) that help treat depression.

Correct answer: A

Huntington’s disease is the classic example of an inherited neurodegenerative disorder. It is caused by a mutation in the HTT gene, and anyone who inherits this mutation from a parent will eventually develop the disease.

Correct answer: C

Trigeminal neuralgia, also known as tic douloureux, is a disorder of cranial nerve V, the trigeminal nerve. The trigeminal nerve is the main sensory nerve for the face; it also controls motor functions of the jaw like biting and chewing. Trigeminal neuralgia is a pain disorder that causes sudden intense pain, typically on one side of the face.

Correct answer: B

Positive symptoms of schizophrenia involve the development of a behavior or thought pattern that isn’t normally present, such as hallucinations and/or delusions. Negative symptoms involve the loss of a normal function, and cognitive symptoms are those that affect someone’s ability to think clearly.

Correct answer: C

The ganglion cells of the retina receive signals from other retinal neurons and their axons bundle together to form the optic nerve, which carries visual information from the brain.

Correct answer: B

Bell’s palsy is a disorder that results from the dysfunction of cranial nerve VII, the facial nerve. It involves weakness or paralysis, typically on one side of the face. The cause of Bell's palsy is not clear, and Bell’s palsy is only diagnosed when there is not another identifiable cause of the facial paralysis (e.g., Lyme disease, trauma).

Correct answer: A

Once threshold is reached, voltage-gated sodium channels rapidly open, allowing Na⁺ ions to rush into the neuron. This inward sodium current drives the depolarization phase of the action potential.

Correct answer: D

The corneal reflex is used clinically to test the integrity of the trigeminal and facial nerves and related structures, typically by touching the cornea with a piece of cotton. The healthy response to touching one cornea would be that both eyes would blink, but damage to the trigeminal or facial nerves or other related structures may cause a deficit in the reflex.

Correct answer: C

Lower motor neuron lesions often cause weakness or paralysis due to direct damage to the neurons that innervate skeletal muscle. This is frequently accompanied by decreased muscle tone and reduced or absent reflexes.

Correct answer: C

Microglia are the brain’s resident immune cells. They act as macrophage-like phagocytes, clearing debris, pathogens, and damaged neurons while regulating inflammation.

Correct answer: A

The ventral tegmental area and substantia nigra are both found in the midbrain. They produce the majority of dopamine used by the brain, and are involved in processes such as movement, motivation, reward, and much more.

Correct answer: B

The corticospinal tract carries voluntary motor commands from the brain to the body. Damage to this tract in the spinal cord can cause paralysis on the same side of the body below the injury.

Correct answer: D

The pineal gland is part of the epithalamus, a major structure in the diencephalon. The main function of the pineal gland is the secretion of melatonin, a hormone that is best known for its role in regulating circadian rhythms.

Correct answer: A

In the peripheral nervous system, each Schwann cell wraps around a single segment of one axon, forming one internode of myelin. This is in contrast to oligodendrocytes in the central nervous system, which can extend processes to myelinate multiple internodes across different axons.

Correct answer: B

The dorsal columns-medial lemniscus is the main pathway for carrying fine touch, vibration, and proprioceptive information from the body to the brain. It allows you to discriminate shapes, textures, and contours—like feeling a key in your hand and identifying it without seeing it.

Correct answer: C

The sensory neurons of the olfactory nerve originate in the olfactory epithelium of the nasal cavity. Their axons pass through the cribriform plate of the ethmoid bone and synapse in the olfactory bulb, where second-order neurons carry the information deeper into the brain.

Correct answer: B

The primary somatosensory cortex lies in the postcentral gyrus, just posterior to the central sulcus.

Correct answer: C

MAOIs block the activity of monoamine oxidase, the enzyme responsible for breaking down serotonin, norepinephrine, and dopamine in the synapse. This leads to increased availability of these neurotransmitters, which is thought to play a role in antidepressant effects.

Correct answer: D

The anterior cerebral arteries supply most of the medial surface of the frontal and parietal lobes.

Correct answer: A

Glutamate is the brain’s main excitatory neurotransmitter. It plays a central role in learning, memory, and overall neural communication. It’s used at more than half of all synapses in the central nervous system.

Correct answer: C

The choroid plexus is a network of specialized cells inside the brain’s ventricles. It is made up of ependymal cells and a rich network of blood capillaries, which work together to filter blood plasma and secrete CSF.

Correct answer: B

Broca’s area is important for language production; damage to it often leads to Broca’s aphasia, where comprehension is relatively preserved but speech is non-fluent, effortful, and halting.

Correct answer: A

Although there are a number of areas of the brain that may be damaged in alien hand syndrome, some of the most common variants of the syndrome involve damage to the corpus callosum. When the corpus callosum is damaged, it may impair the ability of the left and right cerebral hemispheres to coordinate movement between limbs, and to inhibit unwanted movements in the alien hand.

Correct answer: C

The posterior (dorsal) horn contains neurons that receive sensory input from peripheral nerves via the dorsal root, making it the main site for processing somatosensory information such as touch, pain, and temperature.

Correct answer: D

There is a lack of consensus as to what structures should be included in the limbic system, but areas that are often included are the amygdala, cingulate cortex, hippocampus, hypothalamus, septal nuclei, mammillary bodies, prefrontal cortex, certain nuclei of the thalamus, and tracts such as the fornix and medial forebrain bundle. The cerebellum is not generally included.

Correct answer: B

The basilar membrane moves in response to fluid movement in the cochlea. These movement of the basilar membrane bends the stereocilia of hair cells in the organ of Corti, which converts mechanical energy from sound waves into neural signals that the brain interprets as sound.

Correct answer: C

The telencephalon is also known as the cerebrum, and it consists of the largest part of the brain. It contains the cerebral hemispheres, and thus includes the cerebral cortex and a number of other structures lying below it (subcortical structures), along with a variety of important fiber bundles like the corpus callosum.

Correct answer: B

The most widely accepted explanation for cortical folding is it substantially increases the surface area of the cerebral cortex, allowing more neurons and synaptic connections to fit within the limited volume of the skull.