Nervous and Endocrine Systems Flashcards
The diagram below depicts a layer of epithelial cells with associated connective tissue and capillary.
Which of the above labeled structures would synthesize collagen?
A. 2
B. 3
C. 4
D. 5
D is correct. Structure 5 is a fibroblast, embedded in the extracellular matrix. These are the cells that produce the fibers comprising connective tissues such as collagen.
The diagram below depicts a layer of epithelial cells with associated connective tissue and capillary.
Layer 2 might connect to Layers 1 and 3 through which of the following proteins?
A. Connexin
B. Fibronectin
C. Cadherin
D. Occludin
B is correct. Layer 2 is the basement membrane, which is connected to an epithelial layer (1) and the endothelium of the capillary (3). Epithelial cells such as these do not directly connect to collagen and other basement membrane fibers; instead, they contain transmembrane proteins known as integrins that can connect to collagen, or, more typically, to a bridging protein like fibronectin, which itself connects to collagen.
A: Connexin is a gap junction protein and is not involved in this type of connection.
C: Cadherins form cell-cell junctions, not junctions between the cell and the extracellular matrix.
D: Occludin comprises tight cell-cell junctions.
Which of the structures below is NOT an exocrine gland?
A. The liver
B. The pancreas
C. A gastric chief cell
D. The adrenal gland
D is correct. Of the options listed, only D has no exocrine function. The liver and pancreas secrete many hormones into the bloodstream, but also release digestive enzymes into the lumen of GI tract, an exocrine function. Gastric chief cells are purely exocrine and secrete pepsinogen into the stomach.
Injuries to cartilaginous tissue, such as torn and stretched ligaments, can often take quite some time to heal. Which statement best explains why injuries to this type of connective tissue heal so slowly?
A. Cartilage does not contain cells, only fibers; therefore, cells must migrate from other parts of the body to repair it.
B. Cartilaginous fibers must be exposed to an enzyme to assure full tensile strength, and the mechanical stress placed on healing cartilaginous tissue tends to disrupt the action of this enzyme.
C. Cartilage relies on diffusive rather than direct vascular delivery of nutrients, and repairing cells therefore have a hard time sustaining increased activity.
D. Cartilaginous fibers are slow to divide, and an injury only slightly increases the reproduction rate of such fibers.
C is correct. Cartilage is not vascularized, and therefore cannot easily obtain the nutrients necessary to rebuild damaged tissues. Instead, it must rely on diffusion from the surrounding ECM.
A: Cartilage does contain chondrocytes, making this statement incorrect.
B: This explanation is entirely made up.
D: The fibers in cartilage are proteins, not cells, making this false.
A congenital defect in the synthesis of the proteins cloudin and occludin is most likely to impact the function of the:
A. lung vasculature.
B. peripheral nerves.
C. gastric musculature.
D. intestinal lining.
D is correct. Cloudin and occludin are the proteins that form tight junctions between epithelial cells. Therefore, any organ that relies on tight junctions will be negatively affected if their synthesis is impaired. If the intestinal lining is to properly absorb nutrients while leaving behind undesired materials, free diffusion cannot be permitted between the digestive ECM and the lumen of the digestive tract. Tight junctions seal the gaps between epithelial cells in the intestine, allowing cells to selectively control what passes through the epithelium through the use of transmembrane transport proteins. Without tight junctions, nutrient concentrations would equalize due to diffusion through the epithelium, vastly decreasing the efficiency of the GI tract.
A patient is suffering from persistent lethargy and a decreased heart rate, and various diagnostic tests reveal that his condition is neurological in origin. His symptoms are likely caused by a diminished activation of:
A. the limbic system.
B. the enteric nervous system.
C. the sympathetic nervous system.
D. the parasympathetic nervous system.
C is correct. Activation of the sympathetic nervous system stimulates the heart rate and excites the body into activity. The parasympathetic nervous system has opposite effects, causing decreased heart rate and general relaxation. Thus, deactivation of the sympathetic nervous system will cause parasympathetic activity to dominate, producing the described symptoms.
A: The limbic system is associated with the activation of emotions in the brain.
B: The enteric nervous system relates to the control of digestive organs. None of the described symptoms relate to digestion.
A construction worker is taken to the hospital after an accident involving a nail gun. Upon examination, it is determined that a nail entered his torso at an angle that missed most vital organs and blood vessels. However, the nail lodged in his spine between two thoracic vertebrae and severed many of the frontmost nerves, though rear and middle nerves are unaffected. What symptoms will this injury likely cause for the worker?
A. He will lose mobility in parts of the body below the injury.
B. He will lose feeling in parts of the body below the injury.
C. He will lose feeling below the injury, but only on the front side of the body.
D. He will lose both feeling and mobility in parts of the body below the injury.
A is correct. Sensory, or afferent, tracts lie toward the rear (dorsal) side of the spinal cord. In contrast, motor, or efferent, tracts are positioned near the front (ventral) and lateral sides. If only the ventral nerves are severed, the worker should retain sensation in body parts below the injury, but will likely suffer problems with the mobility of both voluntary and involuntary muscles.
Progressive multifocal leukoencephalopathy (PML) is a viral disease that causes inflammation of white matter in the brain and demyelination of the neurons. Symptoms include clumsiness, visual and speech abnormalities, and, occasionally, personality changes. From this information, PML most likely triggers the death of:
A. Schwann cells.
B. microglial cells.
C. astrocytes.
D. oligodendrocytes.
D is correct. Oligodendrocytes produce the myelin sheath of CNS neurons. The question states that in PML, white matter in the brain is demyelinated; since the brain is part of the central nervous system, it must be oligodendrocytes that are affected.
A: This answer is close! But Schwann cells form the myelin sheath in the peripheral nervous system, not the CNS.
B, C: Microglial cells perform maintenance in the brain, while astrocytes help support the blood-brain barrier. Neither glial cell type directly relates to myelin.
The image below depicts several distinct neuron types.
Which type of neurons are likely to predominate in the frontal lobe?
A. 1
B. 2
C. 3
D. 4
C is correct. For this question, we simply need to know that the frontal lobe is part of the brain. Multipolar neurons like #3 predominate in the CNS and the cerebrum specifically; their many dendrites allow them to integrate into a complex neural network capable of complicated responses.
A: This image depicts a unipolar neuron. Such simple neuron structures are rare in humans, though common in some insects.
B: #2 shows a bipolar neuron; these cells are common in special sensory organs, and are most commonly remembered as components of the retina.
D: Pseudobipolar neurons like #4 typically transmit sensory information from the periphery to the central nervous system. While you do not need to be intimately familiar with these structures, you should be able to tell from the figure that these do not resemble neurons found in the brain.
The parasympathetic nervous system promotes vasodilation in which of the following areas?
I. Small intestine
II. Skeletal muscles
III. Adrenal glands
IV. Stomach
A. I and II only
B. II and III only
C. I and IV only
D. I, III, and IV only
C is correct. The parasympathetic nervous system promotes “rest and digest” functions. Therefore, it would tend to dilate blood vessels in digestive organs like the small intestine and stomach.
II: Since the goal of the parasympathetic system is to free up blood flow to the digestive organs, it would constrict, not dilate, vessels in skeletal muscle.
III: The adrenal glands are stimulated by the sympathetic system. Remember, these glands secrete epinephrine and norepinephrine, which are part of the sympathetic response.
Within the nervous system, neurons compose only a fraction of the total cellular population. The remaining cells, broadly termed neuroglia, perform a variety of supporting roles. Which of the following is LEAST likely to be a function of peripheral glia?
A. Insulation and protection of electrically active cells
B. Clearance of cellular debris via phagocytosis
C. Circulation of CSF via the action of cilia present on the cell surface
D. Secretion of small, soluble signaling molecules
C is correct. The peripheral nervous system is not bathed in CSF, so this cannot possibly be a function of peripheral glia. Note that in the CNS, ependymal cells do use cilia to circulate CSF throughout the brain and spinal cord, a function that is essential for the effective clearing of extracellular waste.
A: This is the primary function of Schwann cells, the principal glial cell of the PNS.
B: Phagocytotic clearance is a secondary function of Schwann cells. As long as healthy Schwann cells are present, peripheral neurons are capable of recovering from significant structural damage.
D: Glial cells communicate (both among themselves and with neighboring neurons) using small molecules termed gliotransmitters. This occurs in the PNS and the CNS.
Latrotoxin (LTX), a large globular protein produced by Latrodectus spiders, acts to perforate the presynaptic membrane at the axon terminal. The resulting channel is large enough to permit the free influx of calcium, as well as the passage of water and other small molecules. A Latrodectus bite would most likely result in:
I. swelling of the axon terminal.
II. fusion of docked vesicles with the plasma membrane.
III. widespread release of glutamate within the CNS.
IV. widespread release of acetylcholine within the PNS.
A. I and II only
B. III and IV only
C. I, II, and IV only
D. I, II, III, and IV
C is correct. Swelling will result from the movement of water down its concentration gradient and into the neuron, which contains many large proteins and other solutes that contribute to its hypertonicity. Fusion of presynaptic vesicles is mediated by an increase in intracellular calcium, which the question mentions as a consequence of LTX action. Finally, in the peripheral nervous system, LTX will cause the widespread release of the principal motor neurotransmitter, acetylcholine.
III: We are told that the toxin is a large globular protein. Thus, it is unlikely to cross the blood-brain barrier, which is only permeable to small, hydrophobic molecules or those with a specific transporter. The toxic effects of LTX are most likely the result of peripheral activity.
For some time, long-term potentiation (LTP) was thought to be the primary molecular mechanism by which new memories are consolidated and archived within the brain. Recently, it has become clear that long-term depression (LTD) may also be critical for effective memory formation. Although LTD technically weakens existing synapses and reduces the chances of neuronal conduction, it may be necessary to reduce interference and promote synchrony. Which cellular change could be a component of LTD, but not LTP?
A. CaMKII-mediated phosphorylation of AMPAR, which reduces the threshold voltage for channel opening
B. Increased transcription of AMPAR subunit RNA
C. PKC-mediated phosphorylation of AMPAR, which reduces the affinity of AMPAR for scaffolding proteins
D. Increased mitochondrial activity in response to increased metabolic load
C is correct. Scaffolding proteins provide critical structure to the postsynaptic density, which prevents free diffusion of AMPAR out of the synapse and also prevents endocytotic sequestration. Phosphorylation that promotes detachment from intracellular scaffolds would loosen the positioning of AMPAR, potentially permitting its endocytosis and causing a subsequent reduction in synaptic activity.
A: A reduction in the threshold would allow the channel to open more readily. In other words, a potential could then be generated in response to a relatively low degree of depolarization. This is a sensitizing effect, and would probably be a component of LTP, not LTD.
B: Increased production of AMPAR would greatly increase the sensitivity of the postsynaptic neuron to neurotransmitter signaling. This is not consistent with the description of LTD provided in the question stem.
D: This option is extremely vague. Both catabolic and anabolic processes require energy, so mitochondrial activity could increase during both LTD and LTP.
Monoamine oxidase inhibitors (MAOIs), an older class of antidepressant medications, have largely been replaced by more modern selective serotonin reuptake inhibitors (SSRIs), which act on a specific serotonin transporter. However, MAOIs are still used in the treatment of hypokinesia associated with Parkinson’s disease, a condition caused by the loss of dopaminergic neurons in the CNS. Both SSRIs and MAOIs:
A. reduce extracellular concentrations of monoamines, such as dopamine and serotonin.
B. increase extracellular concentrations of monoamines, such as dopamine and serotonin.
C. inhibit the enzymatic degradation of monoamines, such as dopamine and serotonin.
D. inhibit the enzymatic synthesis of monoamines, such as dopamine and serotonin.
B is correct. The question states that Parkinson’s disease results from a loss of dopaminergic neurons, presumably causing a global deficiency in dopaminergic signaling. If we are to believe that MAOIs are an effective treatment, they must somehow facilitate the action of dopamine in the synaptic cleft. This could plausibly be accomplished by increasing the extracellular (synaptic) concentration of dopamine, which increases the likelihood that dopamine will bind to its postsynaptic receptor. Since we are told that MAOIs have been replaced by SSRIs, the two medications are likely to have an overlapping net effect, at least on serotonin (in other words, a facilitative effect on synaptic serotonin signaling).
C, D: SSRIs are said to target a transporter, not an enzyme.
Under the conditions given, which of the following neurons is most likely to fire an action potential?
A. An unmyelinated neuron that receives multiple EPSPs that summate temporally
B. An unmyelinated neuron that receives multiple IPSPs that summate spatially
C. A myelinated neuron that receives a single EPSP
D. A myelinated neuron that receives a single IPSP
A is correct. Myelination has no effect on neuron excitability. It only affects conduction velocity, which is irrelevant if the neuron never fires at all. Therefore, we can ignore the myelination aspect and choose an answer based on the described combination of input potentials. If more than one excitatory postsynaptic potential (EPSP) arrives in a very short interval, the neuron cannot return to a resting potential in the time between the arrivals. Therefore, multiple inputs over a short span of time increase the likelihood of reaching threshold, which is necessary for an action potential to fire.
B, D: Inhibitory post-synaptic potentials (IPSPs) will generally hyperpolarize a neuron or otherwise inhibit its firing.
The following are lab results for a patient complaining of excess sweating, hunger, fatigue, racing heartbeat and high blood pressure. A hormone-secreting tumor is suspected.
Based on the lab results above, this tumor is most likely located in the:
A. adrenal cortex.
B. adrenal medulla.
C. anterior pituitary.
D. thyroid gland.
C is correct. This patient has high levels of plasma cortisone, which could result from a hormone-secreting tumor that releases CRH, ACTH, or cortisone. We can see that the individual’s values for CRH are normal, but that ACTH is drastically elevated. Therefore, the tumor must be secreting either CRH or ACTH (since excess cortisone release would negatively feed back on ACTH secretion). CRH is released from the hypothalamus, while ACTH is released from the anterior pituitary; of these, only the anterior pituitary is listed as an answer choice.
A: The adrenal cortex secretes cortisone, which is elevated in this patient. However, high levels of cortisone would negatively feed back on and inhibit further CRH and ACTH. In that case, we would expect the patient to have lower-than-normal ACTH levels.
B: The adrenal medulla secretes epinephrine and norepinephrine, which are both unrelated to the given data.
D: While the symptoms may suggest a thyroid condition, T3 and T4 (which are produced in the thyroid) are present at normal levels.
