If a developing country is at Stage 3 of the Population Transition Model (birthrates are falling), then why does the population of that country keep growing?
When a developing country reaches Stage 3 of the Demographic Transition, it is assumed that the country that developed enough to have widespread access to contraception, girls/women's education, and that the cost of each child per family rises, taking away from economic assets of the family, rather than add assets (like working on a farm; more children = more people to help with farming). The population keeps increasing, however, due to population momentum - when the country had high birth rates, the death rate was also higher. Now that healthcare has improved, those children and other adults are healthier and living longer, thus this results in a population momentum of the country overall. Thus, lowering birthrates will not result in lowered population overall until a later stage (Stage 4 or 5). (I would draw the Demographic Transition Model to better show this answer).
How do interest groups sometimes limit representative democracy?
Interest groups can sometimes limit representative democracy when they have significant resources (money and power) to influence elected officials to either change to what the interest group is advocating for, or maintain the status quo regarding current law or policy on that particular issue. However, just because an interest group has a lot of money and power doesn't mean it is necessarily the opinion of the majority of people, and thus limits representative democracy. Since it may not represent the majority viewpoint, well-heeled interest groups may end up protecting the interests of a small elite, because they can keep donating money to elected officials in return for the favor of the elected officials. This gives the interest group even more money and power, which can further narrow the issue, unfairly benefiting a small minority of people. This disproportional access thus limits those interests groups who are not as well funded, even if those less well-funded groups better represent the majority public opinion on a given issue.
What happens in the brain during a PTSD flashback?
During the original traumatic event, the flight-or-flight mechanism takes over, the amygdala is overactivated and the hippocampus is underactivated. After the event is over, the amygdala, like an elephant, "never forgets" because of the strength of the negative emotions. Thus, when a sight, sound, smell, or other environmental trigger reminds the person of the original trauma, the amygdala associates the trigger with that event (and with "danger"), even when the context of experiencing the trigger does not resemble the original event. So the fight-or-flight response is reactivated, which is a flashback. The amygdala is preparing the body to respond to the trigger as if it was the original event, happening in real-time. These are the flashbacks.