Neuroendocrine System
A dog is following the scent of a jackrabbit. Which of the following accurately describes how the dog's brain integrates information for smell? (A) Chemoreceptors in the brain send impulses for smell in the nasal cavity. (B) Chemoreceptor cells in the nasal cavity send impulses to the appropriate area of the brain. (C) Chemoreceptors on epithelial cells of the tongue send hormones to the appropriate area of the brain. (D) Receptors originating in the nose send action potentials to the motor regions of the brain
B. Chemoreceptor cells in the nasal cavity send impulses to the appropriate area of the brain.
The diagram above illustrates feedback control as exerted by the hormone thyroxine. Following surgical removal of the thyroid gland, the level of TSH in the blood will increase. Which of the following best explains this increase? (A) Residual blood thyroxine, from prior to thyroid gland removal, will bind to cells in the anterior pituitary, signaling more TSH secretion. (B) Thyroxine will remain bound to thyroxine receptors on various body cells, and these body cells will secrete additional hormones that stimulate the anterior pituitary to secrete TSH. (C) Thyroxine that was stored in the anterior pituitary prior to thyroid gland removal will signal more TSH secretion. (D) A decrease in thyroxine levels means a loss of inhibition to the hypothalamus and anterior pituitary, leading to increased TSH secretion.
D. A decrease in thyroxine levels means a loss of inhibition to the hypothalamus and anterior pituitary, leading to increased TSH secretion.
The diagram above depicts the response to a pinprick (stimulus) on the tip of a human finger. The arrows show the direction of impulse transmission along the labeled axons. If axon II was damaged before the pinprick, which of the following is most likely? (A) The person will not feel the pinprick. (B) The person can no longer feel pain. (C) The person's finger will not withdraw reflexively. (D) The person cannot transmit nerve impulses to the brain.
C.The person's finger will not withdraw reflexively.
Which of the following observations best supports the hypothesis that CDK5 negatively regulates neurotransmitter release? (A) Introduction of CDK5 protein into neurons results in the movement of synaptic vesicles to the plasma membrane in the absence of any stimulus. (B) Uptake of a gene encoding CDK5 by neurons results in the movement of synaptic vesicles to the plasma membrane in the absence of any stimulus. (C) Suppression of CDK5 expression in neurons inhibits the movement of synaptic vesicles to the plasma membrane in response to a specific stimulus. (D) Inhibition of CDK5 activity in neurons increases the movement of synaptic vesicles to the plasma membrane in response to a specific stimulus.
D. Inhibition of CDK5 activity in neurons increases the movement of synaptic vesicles to the plasma membrane in response to a specific stimulus.
Which of the following representations best shows a portion of an axon at rest (before or after an action potential)?
A.
Transmission of an action potential across a synapse involves the release of neurotransmitters by the presynaptic neuron. The arrival of the action potential triggers a rise in the calcium concentration in the synaptic terminal, and the change in concentration triggers a release of neurotransmitters into the synaptic cleft. Which of the following representations of the movement of calcium, sodium, and potassium ions best shows how an action potential is transmitted to the postsynaptic neuron?
A. (Ca++ going in on the left side, Na+ going in from right side K+going out)
Which of the following best explains why GFP* might exhibit a bright green fluorescence in alkaline conditions but not in acidic conditions? (A) Addition of an H+ to GFP* at acidic pH changes the shape of the protein, preventing fluorescence. (B) CDK5 is a degrading enzyme that hydrolyzes GFP* at alkaline pH, preventing fluorescence. (C) An influx of protons into the axon terminal activates synthesis of new GFP* molecules, preventing fluorescence. (D) Packaging of GFP* into synaptic vesicles is triggered by a sudden drop in cytosolic pH, preventing fluorescence.
A. Addition of an H+ to GFP* at acidic pH changes the shape of the protein, preventing fluorescence.
Previous experiments indicate that CDK5 is active only when attached to a protein called p35. Which of the following best predicts how p35 might play a role in regulating neuron function? (A) Elevated intracellular levels of p35 result in increased synaptic activity. (B) Degradation of p35 results in increased synaptic activity. (C) Reabsorption of p35 from the synaptic cleft results in increased synaptic activity. (D) Attachment of p35 to synaptic vesicles results in increased synaptic activity
B) Degradation of p35 results in increased synaptic activity.
Based on the model, which of the following best explains how regulation of neurotransmitter release might increase the range of responses to a stimulus in the nervous system? (A) In the absence of any stimulus, neurons can still release neurotransmitters. (B) Different neurons in the same neural network can release different amounts of neurotransmitter. (C) In the depolarization phase of an action potential, postsynaptic neurons can adjust the amount of neurotransmitter bound to receptors on their surface. (D) In the recovery phase following a stimulus, enzymes can be mobilized to degrade molecules present in the synaptic vesicles.
B, Different neurons in the same neural network can release different amounts of neurotransmitter.
Based on the model, which of the following describes the most likely mechanism by which CDK5 regulates neurotransmitter release? (A) CDK5 adds methyl groups to DNA, altering expression of genes required for synthesis of neurotransmitters. (B) CDK5 promotes the rearrangement of the lipid molecules of two bilayers into a single membrane. (C) CDK5 alters the activity of other proteins involved in the movement of synaptic vesicles to the plasma membrane. (D) CDK5 binds to gated ion channels in the postsynaptic membrane, resulting in diffusion of calcium ions.
C. CDK5 alters the activity of other proteins involved in the movement of synaptic vesicles to the plasma membrane.
Based on the model, which of the following best explains why a bright green fluorescence was observed following stimulation of a presynaptic neuron? (A) GFP* synthesis was activated when a gene taken up by the neuron was switched on. (B) GFP* stored in the cytoplasm of the neuron was packaged into synaptic vesicles. (C) GFP* contained in synaptic vesicles moved into the synaptic cleft by exocytosis. (D) GFP* present in the synaptic cleft was reabsorbed by endocytosis into the neuron
C. GFP* contained in synaptic vesicles moved into the synaptic cleft by exocytosis.
When a stimulus is applied to a receptor in the skin, an action potential is propagated along a neuron to the brain, where another signal is sent back to then muscle for response. Which of the following best describes what occurs when the action potential reaches a chemical synapse at the end of an axon? A) The action potential jumps from one axon to the next connecting axons. B) The action potential travels through the synapse to the next connecting dendrite C) The action potential jumps the synapse to the next connecting dendrite D) The action potential causes a release of neurotransmitters that travel across the synapse
D. The action potential causes a release of neurotransmitters that travel across the synapse
Thyroxin is a hormone that increases metabolic activities within various tissue targets. Low levels of circulating thyroxin trigger the secretion of thyroid-stimulating hormone (TSH) from the anterior pituitary. TSH secretion then stimulates thyroxin production and release by the thyroid gland. The increased level of circulating thyroxin inhibits further secretion of TSH from the anterior pituitary. Based on the information provided, which of the following can most likely be concluded about the TSH-thyroxin loop? (A) A person taking thyroxin to supplement low thyroxin secretion will produce more TSH. (B) Increased thyroxin production would cause elevated ribosomal activity in the anterior pituitary. (C) The structure of the loop would lead to elevated thyroid and tissue activity due to positive feedback. (D) The feedback mechanism would maintain relatively constant levels of thyroxin throughout tissue targets.
D. The feedback mechanism would maintain relatively constant levels of thyroxin throughout tissue targets.
Precise regulation of specific hormone levels is required for optimal sperm production in mammals, as summarized in the figure above. Anabolic-androgenic steroids (AAS) are synthetic variants of testosterone that are sometimes abused by persons who desire to enhance their athletic performance or alter their physique. Assuming that AAS function in the same way as naturally occurring testosterone, it is most likely that abuse ofAAS would A stimulate FSH secretion B. stimulate testosterone production C. stimulate LH secretion D. reduce sperm production
D. reduce sperm production
Antidiuretic hormone (ADH) is important in maintaining homeostasis in mammals. ADH is released from the hypothalamus in response to high tissue osmolarity. In response to ADH, the collecting duct and distal tubule in the kidney become more permeable to water, which increases water reabsorption into the capillaries. The amount of hormone released is controlled by a negative feedback loop. Based on the model presented, which of the following statements expresses the proper relationship between osmolarity, ADH release, and urine production? (A) As tissue osmolarity rise s, more ADH is released, causing less water to be excreted as urine. (B) As tissue osmolarity rises, less ADH is released, causing less water to be excreted as urine. (C) As tissue osmolarity rises, more ADH is released, causing more water to be excreted as urine. (D) As tissue osmolarity rises, less ADH is released, causing more water to be excreted as urine.
A. As tissue osmolarity rises, more ADH is released, causing less water to be excreted as urine
