These are simple, automatic responses to sensory stimuli, like the knee-jerk reaction. It's like the immediate deployment of airbags upon impact in our analogy.
This is an automatic physiological reaction to stressful or threatening situations, preparing body for action - similar to how a car might automatically switch into four-wheel drive mode when off-roading conditions are detected.
This refers to the body's ability to maintain a stable internal environment despite changes in external conditions - akin to a car's thermostat maintaining a steady temperature inside regardless of outside weather.