All Questions: 361-390

Correct answer: A

At resting membrane potential, potassium ions are more concentrated inside the cell. This gradient is maintained by the sodium-potassium pump, which actively moves potassium into the cell and sodium out.

Correct answer: D

Sleep paralysis is generally believed to occur due to an overlap between REM sleep and wakefulness. During REM sleep, neurons in the brainstem inhibit spinal cord neurons, causing a widespread loss of muscle movement. Sleep paralysis appears to result from this REM-related paralysis persisting into wakefulness.

Correct answer: B

Ischemia is a term that refers to a reduction in blood supply to a bodily tissue, and ischemic strokes occur when blood flow to a part of the brain is blocked or restricted. This is most commonly due to a blood clot blocking a blood vessel.

Correct answer: D

Monoamine oxidase is an enzyme involved with the breakdown of a group of neurotransmitters called the monoamines, which include serotonin. MAOIs inhibit monoamine oxidase, leading to higher levels of monoamines.

Correct answer: A

How alcohol acts on the brain is still not completely understood. Two of the best known effects, however, are alcohol's actions on GABA and glutamate receptors. Alcohol increases GABA activity at a subtype of the GABA receptor known as GABAa. And, it inhibits the activity of glutamate receptors.

Correct answer: D

Bright light therapy is the most common treatment for seasonal affective disorder. Morning exposure to bright light may help to realign the circadian rhythm and improves mood symptoms in some patients.

Correct answer: A

Carpal tunnel syndrome is a common condition caused by the compression of the median nerve, which carries sensations from the thumb, index finger, middle finger, and part of the ring finger—primarily on the palm side of the hand—as well as controls most of the muscles in the thumb, some muscles in the forearm that help with finger and wrist movements, and muscles in the index and middle fingers.

Correct answer: C

Acetylcholine acts on two receptor families with multiple subtypes. Nicotinic receptors are ionotropic and named for their activation by nicotine; they generally produce neuronal excitation. Muscarinic receptors are metabotropic (G-protein coupled receptors) and named for their sensitivity to muscarine; their effects vary by receptor subtype.

Correct answer: D

The internal carotid arteries supply the brain with about 80% of its blood, while the vertebral arteries contribute the remaining 20%.

Correct answer: B

The vestibular system uses two organs, known as the otolith organs, to detect forward and backward movements and gravitational forces. There are two otolith organs in the vestibular labyrinth: the utricle, which detects movement in the horizontal plane, and the saccule, which detects movement in the vertical plane.

Correct answer: C

Sleepwalking typically occurs during stage 3 non-rem sleep (also known as slow-wave sleep or deep sleep). It can also occur in stage 2, but this is much less common.

Correct answer: B

The withdrawal reflex is an automatic response enacted to withdraw a limb from a painful stimulus. If, for example, you were to touch a hot stove or step on a tack, the withdrawal reflex would cause you to pull your arm or leg away from the painful stimulus without having to consciously plan to do so. The reflex is also known as the flexor-withdrawal reflex.

Correct answer: B

Beta blockers are antagonists at receptors called beta-adrenergic receptors, meaning they block these receptors. Beta-adrenergic receptors are normally activated by epinephrine and norepinephrine, and their activation increases heart rate and blood pressure (among other effects). Thus, by blocking beta-adrenergic receptors, beta-blockers can decrease heart rate and blood pressure and help to decrease physical symptoms of anxiety.

Correct answer: A

SNRIs work primarily by inhibiting a mechanism called reuptake. In reuptake, a protein called a transporter transports excess neurotransmitter molecules out of the synaptic cleft, typically back into the neuron that released them. SNRIs inhibit the reuptake of serotonin and norepinephrine, causing levels of these neurotransmitters in the synaptic cleft to rise.

Correct answer: C

There are a number of non-genetic risk factors for spina bifida, but the best established one is inadequate intake of folate or folic acid before and during early pregnancy. Although it’s not completely clear why low folate levels are linked to spina bifida, folate plays important roles in neural development and thus a deficiency is thought to have the potential to interfere with healthy development.

Correct answer: A

During REM sleep, certain neurons in the pons drive activation of the cortex, while others project to the medulla and spinal cord to inhibit motor neurons and cause the paralysis characteristic of REM sleep.

Correct answer: C

These symptoms are a clear sign of oculomotor nerve palsy, which involves lateral deviation of the eye, ptosis (drooping of the eyelid), impaired vertical movement of the affected eye, mydriasis (constantly dilated pupil), and diplopia (double vision).

Correct answer: B

Hydrocephalus is a condition that involves the build-up of cerebrospinal fluid, or CSF, a fluid that is produced in the cavities of the brain known as the ventricles.

Correct answer: C

The medial geniculate nucleus of the thalamus is the primary relay for auditory information, transmitting signals from the inferior colliculus to the auditory cortex in the temporal lobe.

Correct answer: B

Amyloid plaques are extracellular deposits composed mainly of amyloid beta peptides. Although amyloid beta is produced inside neurons, it is released and aggregates outside neurons, forming plaques in the extracellular space.

Correct answer: A

Drugs that bind to a receptor at a different site from where an agonist binds and influence the function of the receptor are called allosteric modulators. Allosteric modulators may increase or decrease the likelihood of an agonist binding to a receptor, enhance or reduce the effects an agonist has when it does bind, or activate the receptor on their own.

Correct answer: D

The primary auditory cortex is located in the temporal lobe of the brain, near the lateral (Sylvian) fissure. This region receives auditory information and is essential for processing basic features of sound such as pitch, loudness, and timing.

Correct answer: C

Gamma-aminobutyric acid, or GABA, is an amino acid neurotransmitter. It is synthesized from another amino acid neurotransmitter, glutamate, in a reaction catalyzed by the enzyme glutamic acid decarboxylase.

Correct answer: B

The substantia nigra is made up of two distinct regions: the substantia nigra pars compacta and the substantia nigra pars reticulata. The substantia nigra pars reticulata is primarily populated with GABA neurons, while the substantia nigra pars compacta is primarily populated with dopamine neurons.

Correct answer: C

A corpus callosotomy involves surgically cutting part or all of the corpus callosum, the major fiber tract connecting the two cerebral hemispheres. In some patients with severe, medication-resistant epilepsy, seizures rapidly spread from one hemisphere to the other through these fibers. By interrupting that pathway, the surgery reduces the spread and severity of seizures.

Correct answer: A

When neurotransmitters interacting with receptors causes repeated depolarization of the neuron, eventually the neuron reaches what is known as its threshold membrane potential. When threshold is reached, a large number of sodium channels open, allowing positively charged sodium ions into the cell and triggering an action potential.

Correct answer: B

The prefrontal cortex is heavily involved with executive functions, which involve processes that focus on controlling short-sighted behavior to be able to act with a goal in mind.

Correct answer: C

Metabotropic receptors are also known as G-protein-coupled receptors. When a neurotransmitter binds to one, it activates a G-protein. The G-protein can then influence the opening of ion channels, activate enzymes, and initiate signaling cascades within the cell.

Correct answer: B

The pathology of Huntington’s disease can be traced back to a mutation in a single gene called huntingtin. The mutation that causes Huntington’s disease is a dominant mutation. Thus, if one parent has the disease, their child has a 50% chance of developing it, too.

Correct answer: D

The organ of Corti is the receptor organ of the ear. It sits atop the basilar membrane and contains receptor cells known as hair cells, which convert sound vibrations into signals the nervous system can understand.