Neurochemistry and Neuroendocrinology Questions

Correct answer: C

The hypothalamus is connected to the anterior pituitary gland via a network of blood vessels called the hypophyseal portal system. The hypothalamus secretes a releasing hormone into the hypophyseal portal system, and the releasing hormone binds to receptors on anterior pituitary cells, prompting the release of a specific hormone from the anterior pituitary into the bloodstream in response.

Correct answer: B

Upon binding to a receptor, GABA can cause the opening of an ion channel that is permeable to negatively charged chloride (Cl-) ions. When these negatively charged ions flow into the neuron, they cause the neuron to become slightly hyperpolarized. Thus, the neuron is less likely to fire an action potential, and GABA has had an inhibitory effect.

Correct answer: A

Neurotransmitter reuptake is a method neurons use to remove excess neurotransmitter molecules from the synaptic cleft. If you were to inhibit reuptake, it would typically cause more neurotransmitter molecules to accumulate in the synaptic cleft (because the neuron would be less capable of removing them). Inhibition of reuptake is the mechanism for a number of psychoactive drugs, including recreational drugs (e.g., cocaine) and therapeutic drugs (e.g., SSRIs).

Correct answer: C

Locus coeruleus means "blue spot" in Latin, and it's so named because it has a bluish tinge in unstained brain tissue. It is the primary site of norepinephrine production in the brain, and it sends norepinephrine throughout the cerebral cortex as well as to a variety of other structures including the amygdala, hippocampus, cerebellum, and spinal cord.

Correct answer: C

The hormonal stress response of the HPA axis first involves secretion of corticotropin-releasing hormone from the hypothalamus. CRH causes the secretion of adrenocorticotropic hormone (ACTH) from the anterior pituitary gland. ACTH travels to the adrenal glands, and prompts the secretion of cortisol.

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: 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

Oxytocin is involved with increasing uterine contractions during labor and with the milk let-down reflex, which causes milk to be released during breastfeeding. Some research suggests it is involved with positive social interactions and feelings of trust, empathy, and social bonding. In truth, however, the research in this area is very unclear, and there is no consensus on oxytocin's effects on behavior.

Correct answer: A

Serotonin was first discovered in blood serum in the late 1940s and found to cause blood vessels to constrict. It was named serotonin, with sero- referring to serum and -tonin referring to tone (as in vascular tone). It was initially thought that serotonin's only role was in regulation of the circulatory system, but it was later discovered to play a key role in the nervous system as a neurotransmitter.

Correct answer: D

The ventral tegmental area (VTA) and substantia nigra are the two largest areas of dopamine neuron concentration (and production) in the brain. There are several major dopamine pathways that carry dopamine from these areas of concentration to other parts of the brain.

Correct answer: A

Curare acts as an antagonist at acetylcholine receptors. Specifically, it blocks nicotinic acetylcholine receptors, which are typically activated to cause muscle contraction. By blocking these receptors, curare causes paralysis. Studying curare helped scientists to understand the function of acetylcholine at the neuromuscular junction---where neurons synapse on muscles to cause them to contract.

Correct answer: A

Tryptophan is necessary for serotonin production. It needs to be taken in through the diet, and once in the body it is converted into 5-hydroxytryptophan (5-HTP) by the enzyme tryptophan hydroxylase. 5-HTP is then converted into serotonin (5-HT).

Correct answer: C

Beta-endorphin is one of a class of substances called endogenous opioids, which received their name because they are produced by the body and bind to the same receptors that opioid drugs like morphine bind to. By binding to opioid receptors, beta-endorphin can elicit natural pain-relieving effects that have been found to be more potent than morphine.

Correct answer: A

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

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: 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 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

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.

Correct answer: C

Cortisol is secreted from the adrenal glands, which are endocrine glands that sit on top of the kidneys. The release of cortisol causes a number of changes that help the body to deal with stress. For example, it helps to mobilize energy like glucose so the body has enough energy to cope with a prolonged stressor.

Correct answer: A

Agonism occurs when a drug binds to a receptor and causes a biological response. Agonists that can generate a maximal response at a receptor are called full agonists. Partial agonists are only able to generate a fraction of the possible response at a receptor.

Correct answer: C

Although melatonin is produced in several parts of the body, the pineal gland is the main source of melatonin released into the bloodstream in a circadian pattern. It receives signals from the suprachiasmatic nucleus (SCN) of the hypothalamus and increases melatonin production in darkness, helping to regulate the sleep–wake cycle.

Correct answer: A

Glutamate is a standard amino acid used to build proteins, and it also serves as the brain’s main excitatory neurotransmitter.

Correct answer: B

While turkey does contain tryptophan, it doesn't have higher levels of tryptophan than many other foods such as chicken, cheese, etc. While it is often claimed that eating a lot of turkey (e.g., on Thanksgiving) can increase tryptophan levels to the point of causing sleepiness, the tryptophan in turkey is not thought to contribute substantially to fatigue. It's more likely that tiredness after a large turkey meal is due to other factors, such as typical post-meal lethargy, alcohol intake, etc.

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

Serotonin is a monoamine neurotransmitter, a term that refers to its chemical structure and the fact that it is derived from an amino acid.

Correct answer: A

When we experience something stressful, the hypothalamus releases a hormone called corticotropin-releasing hormone (or CRH). CRH signals the pituitary gland to secrete a hormone called adrenocorticotropic hormone, or ACTH, into the bloodstream. ACTH travels down to the adrenal glands where it prompts the release of a hormone called cortisol from the cortex, or outer layer, of the adrenal glands.

Correct answer: A

Norepinephrine-producing neurons in the central nervous system are primarily concentrated in the pons and medulla. The most prominent of these groups of neurons is a nucleus called the locus coeruleus, which is the main site of norepinephrine production for the central nervous system.

Correct answer: C

Dopamine is synthesized from the amino acid tyrosine, which is first converted into L-DOPA by tyrosine hydroxylase, and then decarboxylated into dopamine by DOPA decarboxylase.

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: 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.