Okay. So, let's dive into how those brain regions can work together to control our autonomic functions. As I mentioned, the hypothalamus is going to be the main integration center of the ANS. All of the commands are going to be coming from the hypothalamus. And as I kind of alluded to now, the ANS primarily operates in two ways. The first is maintaining homeostasis, and that, of course, is a largely parasympathetic response. It's also going to be responding to emotionally salient or stressful or threatening events, which is more of a sympathetic response. These two functions are going to involve slightly different neural pathways.
This first pathway where we're just maintaining homeostasis, we're going to have some kind of stimulus coming in. For example, the hormone levels in your blood, the chemical composition of your blood, the presence of food in your gut, something like that. The hypothalamus will process that and figure out what function we have to do to get back to homeostasis. For example, let’s slow down hormone production, let’s start digestion, whatever it may be. That command will get sent to the brainstem, to the reticular formation, and then down to the spinal cord where that nerve impulse will then travel along the efferent pathway to the relevant effector organ. Pretty straightforward there.
It gets a bit more complicated when we are responding to emotionally salient or threatening or stressful stimuli because more brain regions are now going to be involved. If we are encountering a threatening stimulus, what's going to happen is some activation in our limbic system. Our amygdala is going to be processing that fear, that threat. We are going to be using our hippocampus to kind of think back into long-term memory. Have we encountered this before? How did we feel about it? How did we deal with it? And we’re going to be consciously processing all of that in our prefrontal cortex, thinking through how am I feeling? Why do I feel that way? How can I get through this situation? That information will get sent to our hypothalamus which will decide if we’re going to be turning on fight or flight or not. Then from there, the pathway is very similar. The hypothalamus will send commands to the brainstem, to the reticular formation, which will then send commands to the spinal cord and then that nerve impulse will travel along the efferent pathway to the relevant organ.
Now, you see we also have this bidirectional arrow going back up from the hypothalamus to the limbic system and cerebral cortex. That is there because sometimes when, let’s say for example, you're beginning to feel some fear and then your fight or flight response kicks in and you start to have that pounding heart, the increased respiration. Well, your body has learned to associate that physical sensation with the emotion of fear. And so when you start feeling that physical sensation, it can actually increase your cognitions about fear, and it kind of creates like a feedback loop. It doesn’t always happen that way, but it can. So that's why that arrow is there as well. And you can see how in both of these pathways, the hypothalamus is still the structure that is in charge and is ultimately going to be sending out the commands for what the ANS should be doing.
Alright. So those are the levels of control in our ANS and I will see you guys in our next video. Bye bye.