Good afternoon!
Case problem 11.1. What is the approximate duration of each wave in this recording?
Hint for answer 11.1. If the frequency of the waveform is 20 Hz (20 waves per second), then the duration of each wave is 1/20 sec, or 50 msec.
Case problem 11.2. Supposing that a patient from who this trace was recorded had a mild form of epilepsy, with the only symptom being vivid visual hallucinations. Where on the patient’s head was this measurement most likely taken?
Hint for answer 11.2. The primary visual cortex and related association areas are in the occipital lobes of the brain (review Figure 7.13), so it is most likely that this abnormal rhythm was recorded by electrodes placed on the scalp at the back of the patient’s head.
Case problem 11.3. Explain why some drugs prescribed to treat allergic reactions cause drowsiness as a side effect.
Hint for answer 11.3. Among the drugs used to treat allergic reactions are antihistamines, which block the histamine receptor. They are prescribed because of their ability to block histamine’s contributions to the inflammatory response, which include vasodilation and leakiness of small blood vessels. Because histamine is associated with the awake state, drowsiness is a common side effect of antihistamines. Fortunately, antihistamines have been developed that do not cross the blood–brain barrier and thus do not have this side effect (e.g., loratadine).
Case problem 11.4. Interleukin 1, a fever-inducing cytokine that increases in the circulation during an infection, promotes the sleep state. Speculate about some possible adaptive advantages of such a mechanism.
Hint for answer 11.4. There are a number of possible reasons it may be adaptive for cytokines to induce sleep. For example, the decreased physical activity associated with sleep may conserve metabolic energy when running a fever and fighting an infection. Sleeping more and eating less may also help by decreasing intake and plasma concentrations of specific nutrients needed by invading organisms to replicate, like iron. From a population health perspective, more time spent in sleep may be adaptive by reducing the number of others with which an infected individual comes into contact.
Case problem 11.5. A general principle of physiology states that physiological processes are dictated by the laws of chemistry and physics. How is this exemplified in the experiment depicted in this figure?
Hint for answer 11.5. Behavior and all brain-mediated phenomena are the result of changes in electrical properties of neurons. The physical principles that govern electrical signaling apply here, such as the generation of local currents (ion fluxes), movement of current across a resistance (lipid bilayers of plasma membranes), transmission of current (axons), and so on. Note that there is no relevant stimulus causing this animal’s behavior; it reflects the electrical events artificially induced in the brain by the implanted electrode.
Case problem 11.6. What might have favored the evolution of emotions?
Hint for answer 11.6. There are many ways emotions could potentially contribute to survival and reproduction. The perception of fear aids survival by stimulating avoidance or caution in potentially dangerous situations, like coming into contact with potentially venomous spiders or snakes or walking near the edge of a high cliff. Our tendency to be disgusted by the smell of rotting food and fecal matter might have evolved as a protection against infection by potentially harmful bacteria or pathogens. Anger and rage could contribute to both survival and reproduction by facilitating our ability to fight for mates or territory or for self-defense. Emotions like happiness and love might have been selected for because of the advantage they provided in kinship safety and pair bonding with mates.
Case problem 11.7. How would you expect dimethyltryptamine (DMT) to affect sleeping behavior?
Hint for answer 11.7. An increase in serotonin concentrations is associated with the waking state, so sleep is inhibited by DMT and other drugs that simulate serotonin action. For this same reason, sleeplessness is also a common side effect of antidepressant medications discussed earlier in the text (e.g., serotonin-specific reuptake inhibitors) because they increase serotonin levels in the brain.
Case problem 11.8. After a brief meeting, you are more likely to remember the name of someone you are strongly attracted to than the name of someone for whom you have no feelings. Propose a mechanism.
Hint for answer 11.8. The involvement of the limbic system in the formation of declarative memories (like remembering names) provides a clue. Experiences that generate strong emotional responses cause greater activity in the limbic system and are more likely to be remembered than emotionally neutral experiences.
Case problem 11.9. Note the various brain areas of increased metabolic activity as revealed by the PET scan in this figure. How does this reflect the general principle of physiology that information flow between cells, tissues, and organs is an essential feature of homeostasis and allows for integration of physiological processes?
Hint for answer 11.9. It is clear from these images that a language task (for example, speaking and listening to words) activates many different parts of the cerebral cortex at the same time. As you have learned in Chapters 6 through 8, different regions of the cortex communicate extensively with each other via fiber tracts. The images in this figure indicate that each specific type of language task is associated with considerable information flow in the form of electrical signals between different regions (lobes) of the cerebral cortex. Other tasks, such as motor tasks or interpretation of various types of sensory input, would also generate complex patterns of activation throughout parts of the cortex.
Good luck with your studies!