Neurochemistry and Neuroendocrinology Questions - p. 2

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: 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: D

Serotonin is primarily removed from the synaptic cleft by a transport protein called the serotonin transporter, or SERT.

Correct answer: A

When we experience something stressful, the hypothalamus releases a hormone called corticotropin-releasing hormone (or CRH). This starts the cascade by signaling the pituitary gland to secrete a hormone called adrenocorticotropic hormone, or ACTH into the bloodstream. ACTH travels to the adrenal glands where it prompts the release of a hormone called cortisol from the adrenal glands.

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

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

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: 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: A

Beta-endorphin is a peptide neurotransmitter and hormone found in the central and peripheral nervous systems. It is best known for its role in pain inhibition. 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: D

Dopamine is primarily removed from the synaptic cleft by a transporter protein called the dopamine transporter. Dopamine is taken back up into the presynaptic neuron and typically either repackaged into vesicles or broken down by the enzyme monoamine oxidase (MAO).

Correct answer: B

The pineal gland is made up of secretory cells called pinealocytes, which secrete melatonin throughout the 24-hour cycle. Secretion is highest in the middle of the night. It begins to decrease as it gets closer to dawn and is lowest during daylight hours.

Correct answer: C

After neurotransmitters have communicated with a postsynaptic neuron, they must be removed from the synaptic cleft. To accomplish this, many synapses rely primarily on proteins called transporter proteins, which remove neurotransmitters from the synaptic cleft and typically shuttle them back into the neuron that released them in a process called reuptake.

Correct answer: D

Serotonin neurons are primarily found in the brainstem in clusters of neurons called the raphe nuclei. Serotonin neurons from the raphe nuclei project throughout the brainstem and brain, and provide serotonin to the rest of the central nervous system.

Correct answer: B

Most neurotransmitters are packaged in small membranous sacs called vesicles.

Correct answer: C

There are 3 identified ionotropic glutamate receptors, named for substances that activate them: NMDA, AMPA, and kainate receptors. mGluR1 through mGluR8 are metabotropic glutamate receptors.

Correct answer: C

Oxytocin is primarily produced in the hypothalamus and transported through axons to the posterior lobe of the pituitary gland. From there it is secreted into the bloodstream of the body.

Correct answer: C

Although GABA’s primary functions are as a neurotransmitter, it has the structure of an amino acid and thus is referred to as 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: A

Serotonin is a monoamine neurotransmitter, a term that refers to its chemical structure and the fact that it is derived from an amino acid. To synthesize serotonin, the amino acid tryptophan is converted to 5-hydroxytryptophan, or 5-HTP, and 5-HTP is converted to serotonin, or 5-HT.

Correct answer: D

The anterior pituitary produces a number of hormones, and their secretion into the bloodstream is controlled by releasing hormones that are secreted by the hypothalamus.

Correct answer: B

Despite popular conceptions, dopamine is not thought to directly produce feelings of pleasure. Instead, it seems to play a key role in motivation and reward learning—helping the brain recognize cues associated with rewards and driving behavior to seek them out again.

Correct answer: B

Although GABA is widely known as the brain's main inhibitory neurotransmitter, in early embryonic and neonatal development, GABA is primarily excitatory. GABA is excitatory early on because immature neurons contain a high concentration of chloride ions inside the cell. When GABA binds to its receptors, chloride flows out of the neuron, causing the cell to depolarize—making it more likely to fire. Mature neurons have lower levels of internal chloride and GABA is inhibitory.

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: D

Neurotransmitters are typically stored in and released from the axon terminals (synaptic boutons) of the neuron.

Correct answer: A

Parasympathetic postganglionic neurons primarily release acetylcholine. This neurotransmitter binds to muscarinic receptors on target organs, producing effects like slowing the heart rate, stimulating digestion, etc.

Correct answer: B

In a famous experiment in 1921, Otto Loewi demonstrated that chemical signaling played a key role in neural communication by showing a chemical he called Vagusstoff could affect the activity of the vagus nerve. Prior to that experiment, many neuroscientists believed neural communication was only electrical. In 1936, Henry Dale isolated Loewi's Vagusstoff and named it acetylcholine.

Correct answer: C

Allosteric modulators bind to a receptor at a different site from where an agonist binds and influence the function of the receptor. Allosteric modulators can 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.