All Questions: 421-450

Correct answer: A

When a neuron is at rest, potassium ions and organic anions are more concentrated inside the cell, while sodium and chloride ions are more concentrated outside the cell.

Correct answer: C

Pain is primarily carried by two classes of peripheral axons: thinly myelinated A-delta fibers, which conduct fast, sharp, well-localized pain, and unmyelinated C fibers, which conduct slower, dull, aching, or burning pain.

Correct answer: A

SNARE proteins (including synaptobrevin/VAMP, syntaxin, and SNAP-25) form a complex that docks and primes synaptic vesicles and then drives membrane fusion during neurotransmitter release.

Correct answer: D

The intraparietal sulcus runs horizontally across the lateral surface of the parietal lobe and divides it into the superior and inferior parietal lobules.

Correct answer: A

CTE is classified as a tauopathy; it is defined by the accumulation of hyperphosphorylated tau in neurons and other cells like astrocytes to form abnormal clusters or aggregates.

Correct answer: C

Brain-derived neurotrophic factor, or BDNF, is a neuropeptide that plays a role in a wide range of important nervous system processes, including the growth and survival of neurons and the formation and strengthening of synaptic connections.

Correct answer: C

Non-REM stage 3 sleep is also known as slow-wave sleep or deep sleep. In stage 3, delta waves, which are low-frequency, high amplitude waves, make up at least 20% of brain activity.

Correct answer: D

The posterior cerebral artery supplies the occipital lobe, including the primary visual cortex.

Correct answer: B

There are several areas of the brain where dopamine neurons are concentrated. The largest are the substantia nigra pars compacta and ventral tegmental area in the midbrain.

Correct answer: D

While mutant huntingtin protein may display "prion-like" behavior, Huntington's disease is not considered a prion disease.

Correct answer: C

When the patellar tendon of the quadriceps muscle is stretched, the stretch is detected by stretch receptors known as muscle spindles that are found in the quadriceps muscle.

Correct answer: B

Meningitis is an inflammation of the meninges (the membranes that surround the brain and spinal cord). The most severe cases of meningitis tend to involve bacterial infections, and symptoms include headache, neck stiffness, fever, and altered mental status.

Correct answer: C

Oxytocin is made in the hypothalamus and released from the posterior pituitary gland.

Correct answer: D

If light is shined into the right eye and neither pupil constricts, it suggests a deficit in sensory input and may indicate damage to the right optic nerve.

Correct answer: D

GABA-B receptors are metabotropic (or G protein-coupled) receptors; when activated they frequently cause the opening of potassium channels. These channels allow positively charged potassium ions to flow out of the neuron, making the neuron hyperpolarized and less likely to fire an action potential.

Correct answer: D

The most common treatments for Alzheimer’s disease involve drugs that inhibit the activity of acetylcholinesterase, an enzyme that breaks down the neurotransmitter acetylcholine. The drugs, called acetylcholinesterase inhibitors, increase levels of acetylcholine, which is thought to promote healthy cognition and memory.

Correct answer: B

The anterior cerebral, internal carotid, and posterior cerebral arteries on both sides of the brain are interconnected by the anterior and posterior communicating arteries, forming a ring-like structure known as the circle of Willis. This interconnection can allow blood flow to continue if a major vessel is blocked on one side of the brain.

Correct answer: B

Microvilli extend from taste receptor cells through an opening called the taste pore into the mouth. These microvilli come in contact with substances in the mouth that can be tasted, also known as tastants. Tastants interact with taste receptor cells through a number of different mechanisms to depolarize the cells.

Correct answer: B

Methamphetamine is approved by the FDA for the treatment of ADHD, and was commonly prescribed (as Desoxyn) in the 1960s to early 1970s to treat pediatric hyperactivity before tighter controls on the medication in 1971 led to a drastic decline in use.

Correct answer: A

The mechanisms underlying tinnitus are not well understood, but it’s thought that hearing loss might be linked to tinnitus in a number of ways. Damage to the cochlea, for example, may lead to increased signaling in other auditory structures to compensate for the reduction in auditory input from the cochlea, and the resultant amplification of neural noise may lead to tinnitus.

Correct answer: D

The anterior pituitary contains cells that produce several important hormones: adrenocorticotropic hormone, thyroid-stimulating hormone, luteinizing hormone, follicle-stimulating hormone, growth hormone, and prolactin. Circulating melatonin is produced and secreted primarily by the pineal gland.

Correct answer: C

The vagus nerve (CN X) sends and receives signals between the brain and much of the GI tract. Because it carries both sensory information from the gut to the brain and motor signals back to the gut, it is the main nerve involved in communication along the gut–brain axis.

Correct answer: A

Neurons carrying sensory information enter the back of the spinal cord as dorsal rootlets, which all emerge from a single dorsal root. The cell bodies of these sensory neurons are contained in a cluster of cell bodies called a dorsal root ganglion.

Correct answer: A

Leptin is a hormone that is known to suppress hunger. Leptin levels are higher on average in obesity because adipose tissue produces leptin. The brain, however, is often less responsive to leptin---a phenomenon known as leptin resistance.

Correct answer: B

A concussion is a type of traumatic brain injury that occurs when rapid movement of the head or an impact to the head causes the brain to move within the skull, potentially stretching axons and damaging cell membranes of neurons.

Correct answer: C

Damage to the glossopharyngeal nerve can cause a variety of symptoms, including a loss of taste on the posterior ⅓ of the tongue, trouble swallowing, and generally decreased sensation on the back of the tongue, the soft palate, and pharynx.

Correct answer: D

The enzyme acetylcholinesterase is present at the neuromuscular junction; it breaks down acetylcholine and in the process terminates its effects on the muscle fiber, thus ending the communication between the motor neuron and the muscle fiber.

Correct answer: C

In seizures called focal seizures, excessive neural activity begins in one specific area of the brain called the seizure focus, but it can also propagate to other areas of the brain.

Correct answer: B

Astrocytes are star-shaped glial cells with many functions, which include providing nutrient support to neurons, helping repair damage to nervous system tissue, regulating communication between neurons, and maintaining the blood-brain-barrier, which keeps potentially toxic substances in the blood from entering the brain.

Correct answer: B

The axons of olfactory receptor cells travel from the olfactory epithelium to the olfactory bulb. These axons make up the first cranial nerve, which is generally considered the shortest cranial nerve.