Orgasm is a reflex of the autonomic nervous system.

And then the message cascades into the amygdala, and then goes down the autonomic nervous system.

So if the amygdala is excited, and this is something important, the messages then cascade into the autonomic nervous system.

I felt something in this plexus of blood vessels and nerves, and there must be some muscles in there as well somewhere, I guess.

But if you remove the arm, you simply anesthetize my arm, so you put an injection into my arm, anesthetize the brachial plexus, so the arm is numb, and there is no sensations coming in, if I now watch you being touched, I literally feel it in my hand.

Many chemical mediators are involved, including cortisol and adrenalin from the adrenal glands, other hormones and neurotransmitters (such as serotonin and noradrenalin), and responses from the autonomic and immune systems. Depression thus leads to changes in the rest of the body, owing to long term chemical imbalances in the systems that control the heart, the immune system, and metabolism.