All Questions: 151-180

Correct answer: D

The withdrawal reflex (also known as the flexor withdrawal reflex) is an automatic, polysynaptic spinal reflex that causes a limb to quickly withdraw from a painful stimulus. Because the circuitry is contained within the spinal cord, the reflex does not require input from the brain and occurs without conscious control.

Correct answer: C

Before the 1870s, scientists had little ability to obtain clear pictures of neurons due to the lack of a selective stain to make neurons appear distinct. Golgi developed a stain using silver nitrate, which caused neurons to appear dark against a yellow background. Golgi's stain led to the establishment of the fact that neurons are distinct cells, something that was very much up for debate before.

Correct answer: D

The facial nerve carries taste sensations from the anterior 2/3 of the tongue, and the glossopharyngeal nerve carries taste sensations from the posterior 1/3 of the tongue. The vagus nerve also carries some taste sensations, but primarily from the epiglottis and throat.

Correct answer: A

Norepinephrine is synthesized from dopamine in a reaction catalyzed by the enzyme dopamine beta-hydroxylase.

Correct answer: B

The midbrain contains the ventral tegmental area (VTA) and substantia nigra, which are the two largest concentrations of dopamine neurons in the brain.

Correct answer: C

The anterior horn contains the cell bodies of motor neurons that activate skeletal muscle. These neurons, called alpha motor neurons, leave the cord in the ventral roots and represent the way the nervous system enacts movements. Thus, damage to the anterior horn would result in a deficit of movement.

Correct answer: B

LSD’s activity at a subtype of serotonin receptor called the 5-HT2A receptor is critical to the drug’s psychedelic effects. LSD acts as a partial agonist at the 5-HT2A receptor, which means that it binds to the 5-HT2A receptor and generates a response that is a fraction of what the natural ligand, serotonin, generates. LSD also interacts with other receptors, although the role of these receptors in the effects of LSD is less clear.

Correct answer: C

The dorsal columns-medial lemniscus pathway (also called the posterior columns-medial lemniscus) is the main pathway that carries tactile information to the brain. It carries information about fine touch, vibration, pressure, and proprioception (the sense of body position).

Correct answer: B

The dopamine neurons in the substantia nigra are primarily found in the substantia nigra pars compacta; the pars reticulata is more heavily populated with GABA neurons. The substantia nigra gets its dark coloring from the large number of dopamine neurons in the pars compacta, as they express high levels of a dark pigment called neuromelanin.

Correct answer: B

The auditory cortex is found in the temporal lobe. Most of it is hidden from view, buried deep within a fissure called the lateral sulcus. Some auditory cortex is visible on the external surface the brain, however, as it extends to a gyrus called the superior temporal gyrus.

Correct answer: D

Seasonal affective disorder (SAD) is a subtype of depression or bipolar disorder in which symptoms appear at specific times of the year and go into full remission at other times. Several hypotheses have been proposed to explain seasonal affective disorder, with one being that low levels of vitamin D could play a role. The evidence is mixed, however, and suggests vitamin D probably only plays a role in certain cases.

Correct answer: C

Xanomeline (sold as xanomeline-trospium, or Cobenfy) is an acetylcholine receptor agonist. This means that it stimulates acetylcholine receptors (specifically M1 and M4 receptor subtypes). This is unique because most other antipsychotics primarily target dopamine and/or serotonin receptors.

Correct answer: D

The fovea is a small, specialized area in the center of the retina. It's the area responsible for our sharpest, most detailed vision. The fovea contains mostly cone photoreceptors, which are responsible for color vision and fine detail. It has virtually no rods, which are more sensitive to low light but less precise.

Correct answer: A

Lyme disease is a tick-borne illness caused by a group of bacteria belonging to the genus Borrelia. When Lyme disease affects the nervous system, the resulting condition is called Lyme neuroborreliosis.

Correct answer: B

Pain and temperature sensations are primarily carried in the spinothalamic tract. This pathway carries these sensations from receptors to the spinal cord and then crosses over (i.e., decussates) to the other side of the spinal cord before traveling up to the brain. Thus, the tract in the spinal cord is carrying info from the other side of the body. Damage to the spinothalamic tract then, results in a deficit in pain and temperature sense on the opposite side of the body---below the damage.

Correct answer: A

The placebo effect isn't just "all in your head" in the dismissive sense—it actually triggers real biological changes in the brain. When someone believes they're receiving an active treatment, even if it's inert, their expectation can activate brain systems involved in reward, pain, mood, etc.

Correct answer: D

Pacinian corpuscles are rapidly-adapting touch receptors with very large receptive fields. They are thought to be most effective at transmitting information about vibrations objects cause when they are contacted or grasped by the hand. This information may be important for the use of tools.

Correct answer: B

Leptin is produced by fat cells in the body and binds to receptors in the brain (e.g., cortex and hypothalamus). It provides an indication to the brain of the amount of energy reserves someone has, and it acts as a signal to reduce appetite. Thus, higher levels of leptin would typically make someone less hungry.

Correct answer: D

The discovery of the motor cortex is primarily credited to Gustav Fritsch and Eduard Hitzig. In 1870, Fritsch and Hitzig conducted experiments with dogs that demonstrated part of the cerebral cortex was directly responsible for causing movement; that region of the cortex would eventually be known as the motor cortex.

Correct answer: A

A lumbar puncture involves taking a sample of cerebrospinal fluid from around the spinal cord; it is the only definitive way to diagnose meningitis. Neuroimaging, a physical exam, and blood tests can all support the diagnosis or provide additional information on the infection.

Correct answer: C

Earlier estimates suggested glia outnumbered neurons 10 to 1, but more recent research using better cell-counting techniques (e.g., isotropic fractionation) has shown the neuron-to-glia ratio is closer to 1:1 across the whole brain.

Correct answer: D

The HPA axis includes a group of hormone-secreting structures: the hypothalamus, pituitary gland, and adrenal glands. Its primary function is to regulate the stress response. The cascade of hormones of the HPA axis involves the release of CRH from the hypothalamus, ACTH from the pituitary gland, and cortisol from the adrenal glands.

Correct answer: A

The Circle of Willis is made up of the anterior cerebral arteries, internal carotid arteries, posterior cerebral arteries, anterior communicating artery, and posterior communicating arteries. The interconnection of these vessels can allow blood flow to continue if a major vessel is blocked on one side of the brain.

Correct answer: C

Purkinje cells are a distinctive type of neuron found only in the cerebellum. They have extensive branching dendrites, which gives them a very unique appearance.

Correct answer: B

Computed tomography, also known as computed axial tomography, is a type of structural neuroimaging. It is usually called a CAT or CT scan. It involves taking a series of x-ray images from various locations around the head. These images can then be combined to construct an image of the brain. The other answer choices all are used to obtain information about brain function.

Correct answer: C

Tau protein is normally found inside neurons and involved in maintaining neuronal structure. In Alzheimer's disease it accumulates inside neurons in clusters called neurofibrillary tangles.

Correct answer: A

Luigi Galvani discovered that muscles contract in response to electrical stimulation, a phenomenon that he observed in frog legs. His work revealed that electricity plays a role in the nervous system, which was a critical step toward understanding neuronal physiology.

Correct answer: B

The basilar membrane moves in response to fluid vibrations in the cochlea. This movement causes the hair cells' stereocilia to bend, which leads to their activation and the transmission of sound signals to the brain.

Correct answer: B

Stage 2 sleep is characterized by the presence of phenomena on an EEG known as sleep spindles and K complexes. Sleep spindles are trains of high-frequency waves. A K complex involves a biphasic wave that stands out from the rest of the EEG. The roles of these unique brainwave patterns is not completely clear.

Correct answer: A

Vasopressin (also known as antidiuretic hormone) is produced in the hypothalamus and released from the posterior pituitary. It helps regulate fluid balance by promoting water reabsorption in the kidneys and supports blood pressure by constricting blood vessels.