All Questions: 61-90

Correct answer: A

Naloxone is a competitive antagonist at opioid receptors, which means that it works by binding to the same receptors that opioid drugs bind to, but instead of activating those receptors like opioid drugs, naloxone blocks activity at them. Naloxone also causes opioid drugs that are already attached to the receptor to be displaced.

Correct answer: D

The longitudinal fissure is a deep groove that runs along the middle of the brain, separating it into two cerebral hemispheres. It is one of the most recognizable features of the brain.

Correct answer: B

While there are some functional differences between the left and right cerebral hemispheres, the idea that someone's personality style corresponds to a greater utilization of one cerebral hemisphere over another is generally regarded as a myth. A 2013 study, for example, looked at the brains of 1,000 people with a variety of personalities, and found no evidence of utilization of one hemisphere over the other.

Correct answer: D

The sedating and anxiety-reducing effects of benzodiazepines are believed to be attributable to the drugs’ actions at receptors for the neurotransmitter gamma-aminobutyic acid, or GABA. By increasing GABA activity, these drugs reduce neural activity, which can help to reduce anxiety by reducing the occurrence of anxiogenic thoughts. Benzodiazepines are no longer a first-line option to treat anxiety, however, because they have a high potential to cause dependence.

Correct answer: A

The accessory nerve supplies the sternomastoid and trapezius muscle. The sternomastoid helps to turn your head to the side, as well as bend your neck down or to the side. The trapezius is involved with the movement of the neck and scapula (shoulder blade). Dysfunction of the accessory nerve often causes shoulder pain, impaired arm and shoulder movement, a drooping shoulder, and/or protrusion of the shoulder blade (winged scapula).

Correct answer: C

The spinal cord itself ends at L1-L2, but the meningeal layers continue down to the S2 level, as does the subarachnoid space (which contains cerebrospinal fluid). Between the L1/L2 and S2 vertebrae is a region known as the lumbar cistern, which contains cerebrospinal fluid but no spinal cord. Thus, it is safest to sample cerebrospinal fluid from this region, since insertion of a needle doesn't risk damaging the spinal cord.

Correct answer: B

The hypothalamus plays a direct role in the regulation of body temperature. It constantly monitors the temperature of the body and, when temperature gets too high or too low, enacts mechanisms to bring it back to baseline. For example, if your body is too hot, the hypothalamus can cause perspiration to cool it off. The hypothalamus is involved a long list of other functions as well.

Correct answer: C

Spina bifida is a birth defect that involves disrupted formation of a structure called the neural tube. The neural tube forms in early neural development, and eventually will become the brain and spinal cord. In spina bifida, the neural tube either does not form or close properly.

Correct answer: C

Amphetamine enters neurons and disrupts the storage of monoamines (e.g., dopamine, norepinephrine, serotonin) in synaptic vesicles. This leads to high levels of free-floating monoamines inside the neuron. Amphetamine then can cause the monoamine transporters to run in reverse, leading to increased release of monoamines into the synaptic cleft. These elevated monoamine levels (especially dopamine & norepinephrine) are thought to be responsible for the main psychoactive effects of amphetamine.

Correct answer: B

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: D

The raphe nuclei are a collection of nuclei clustered around the midline of the brainstem. They are thought to contain about 85% of your brain's serotonin-producing neurons, and the neurons in the raphe nuclei project throughout the central nervous system (sending serotonin throughout the nervous system as well).

Correct answer: A

fMRI provides information about brain activity. It detects changes in blood flow in the brain, which is an indirect measure of brain activity because parts of the brain that are more active require more blood flow. MRI and CT scans provide information about the structure of the brain, while DTI provides information about white matter tracts, or pathways, within the brain.

Correct answer: D

Melatonin secretion from the pineal gland occurs in the dark phase of the night. Melatonin secretion is inhibited by exposure to light, and the highest levels of secretion typically occur after midnight. Secretion from the pineal gland during the day is negligible.

Correct answer: C

The axon is the extension of a neuron that carries an action potential from one end of a neuron to the other. The axon conducts action potentials away from the soma/cell body and toward the axon terminals.

Correct answer: C

The cerebral aqueduct connects the third ventricle with the fourth ventricle. Cerebrospinal fluid (CSF) is produced in all of the ventricles and flows out through the fourth ventricle into the subarachnoid space. If the cerebral aqueduct is blocked, CSF would continue to be produced in the lateral and third ventricles, but it would have no way of reaching the fourth ventricle to exit the ventricular system. Thus, it would accumulate in the third ventricle and both lateral ventricles.

Correct answer: A

One of the hallmark signs of Alzheimer's disease is the accumulation of misfolded amyloid beta protein in amyloid plaques outside of neurons. It's still uncertain, however, exactly what role these plaques play in the progression of the disease.

Correct answer: B

The semicircular canals consist of three tubes, positioned approximately at right angles to one another, that are each situated in a plane in which the head can rotate. This design allows each of the canals to detect one of the following head movements: nodding up and down, shaking side to side, or tilting left and right.

Correct answer: B

Narcolepsy is linked to a loss of orexin-producing neurons in the hypothalamus, leading to low orexin levels. Orexin neurons have an excitatory effect on several regions of the brain that are involved in promoting wakefulness and suppressing REM sleep. Thus, the loss of these neurons leads to deficiencies in maintaining wakefulness. The cause of the loss of orexin neurons in narcolepsy is not completely understood, but several lines of evidence implicate an autoimmune mechanism.

Correct answer: B

Most of the effects of caffeine are thought to be traceable back to its action as an antagonist at receptors for the neurotransmitter adenosine, meaning it binds to and blocks adenosine receptors (reducing activity there). Adenosine receptors are thought to be involved in promoting sleep, so by blocking those receptors caffeine promotes wakefulness.

Correct answer: D

Amyotrophic lateral sclerosis (ALS) is a debilitating neurodegenerative disorder characterized by a progressive loss of motor function. ALS affects upper motor neurons and lower motor neurons. As these motor neurons stop working, muscles also begin to atrophy; this can eventually lead to respiratory failure, which is often the cause of death in ALS patients.

Correct answer: B

The anterior horn contains the cell bodies of motor neurons that activate skeletal muscle to cause movement. Damage to the anterior horn typically causes movement deficits, such as paralysis, weakness, and hyporeflexia; since the damage is in the cervical cord, it would affect the upper limbs.

Correct answer: A

The pons is a major division of the brainstem. Pons is Latin for "bridge"; the structure was given its name by the Italian anatomist Costanzo Varolio, who thought that the most conspicuous portion of the pons resembled a bridge that connected the two cerebellar hemispheres.

Correct answer: A

S.M. is a well-known medical case who has almost completely lost the ability to experience fear after a rare genetic disorder caused the deterioration of both of her amygdalae. Her case helped us to recognize the importance of the amygdala in fearful emotions, although it is now recognized to play a role in positive emotions as well.

Correct answer: C

Stage 3 sleep is also known as deep sleep or slow-wave sleep. In stage 3 sleep, brain activity (as measured by an EEG) is made up of at least 20% delta waves, which are low-frequency (slow), high amplitude waves. Stage 3 sleep is the deepest stage of non rapid-eye movement sleep, and is thought to be especially important to overall restfulness.

Correct answer: D

The white matter lesions are a hallmark sign of MS. The disease is characterized by damage to the myelin sheaths surrounding the axons of neurons in the central nervous system. This myelin damage disrupts the conduction of action potentials along these axons, which is thought to cause many of the symptoms of the disease. The damage is thought to be caused by an autoimmune attack.

Correct answer: B

The sodium-potassium pump uses the energy of ATP to move 3 sodium ions out of the cell and 2 potassium ions into the cell with each cycle of the pump. The actions of the pump help to ensure that sodium ions are more concentrated outside the cell and potassium ions are more concentrated inside the cell, which helps create the conditions that enable action potentials to occur.

Correct answer: C

Estimates have varied over time, but our current best estimate of the number of neurons in the brain is 86 billion (on average). Neurons are not distributed evenly throughout the brain, and some areas (e.g., cerebellum) have much more than others.

Correct answer: A

When an action potential travels down the neuron and reaches the axon terminal, it causes depolarization of the neuron. This change in membrane potential causes voltage-gated ion channels, which are ion channels that open in response to changes in membrane potential, to open and allow calcium to enter the cell. Calcium seems to be involved with mobilizing vesicles to prepare them for neurotransmitter release.

Correct answer: C

The vagus nerve is an extremely long nerve that travels from the brainstem to the colon and has a long list of functions. One of those functions is to act as the main parasympathetic nerve of the body, providing parasympathetic innervation to organs throughout the neck, thorax, and abdomen, contributing to a variety of functions such as slowing of the heart rate.

Correct answer: A

The function of acetylcholinesterase is to remove acetylcholine from the synapse—in effect reducing the effect the neurotransmitter can have at that synapse. By inhibiting acetylcholinesterase activity, AChEIs cause acetylcholine levels to increase. In the process, these drugs can lead to modest improvements in memory.