We say our hearts are overflowing with joy. Or we bemoan our hearts breaking. But when it comes to love, the brain, not the heart, is the engine that gets romance started. It’s also what can grind your next love affair to a halt.
The Brain in Love
In casual speech, we use the terms left brain and right brain as shorthand to accord a gender to each hemisphere of the brain’s main processing center, called its cerebral or frontal cortex. The left side of the frontal cortex is associated with the male. It does the rational and analytical tasks. It worries about details, planning, directions, and how something is designed and constructed, whether a city or a computer. In the chemistry of love, the left hemisphere monitors and manages your relationships. It weighs in on important decisions: whether to accept a date, jump into bed, or say “I do.”
The right hemisphere of the frontal cortex, associated with all things female, is given over to creativity, feelings, the overview or gestalt of a situation rather than the details, and to awareness of self and others. It processes the emotions of love and prompts you to act on them. Brain science has finally caught up with this common wisdom in at least one respect: particularly in matters of love and sex, male and female brains are not the same. Remember that when your next argument convinces you that you and your partner really do come from different planets.
Reptilian Love
As much as we may wish to identify exclusively with our higher “thinking” brains, when it comes to love, and especially sex, the lower or reptilian brain calls many of the shots. That’s because it controls the autonomic nervous system of the body. This is the system that operates largely without conscious thought. That includes the mating instinct, and the biochemical actions, and reactions that make mating possible.
The Hypothalmus
The hypothalamus is called the brain’s sex and pleasure center because it’s the seat or central control station for the body’s autonomic nervous system. It regulates hunger, thirst, body temperature, ovulation in females, and libido in both sexes. As such, it is the relay station between the endocrine system (glands, hormones) and the central nervous system (the brain and the spinal cord); thus it’s the hypothalamus that’s charged with sending out the signal for the sex hormones to get going.
Given the fact that many different drives are regulated by the hypothalamus, it makes sense that you don’t want to eat dinner and have sex at the same time.
The hypothalamus sends out signals to other organs and body systems in two distinct ways: by sending electrical pulses as neurotransmitters into the CNS, the central nervous system, and by activating the pituitary to release hormones into the bloodstream.
The Thalmus
The thalamus is the part of the lower brain that processes sensations received from several sensory organs (sight, taste, hearing, balance) and sends signals on to the frontal cortex.
The pituitary is a gland in the endocrine system situated next to the hypothalamus. It is the body’s main hormone factory, including the sex hormones.
The Amygdalae
The amygdalae are an almond-shape cell group in the brain. Considered the seat of our emotions, the amygdalae are closely linked by nerve pathways to the areas of the hypothalamus and thalamus that respond to sense perceptions and control the different physical changes activated by romantic attraction and attachment, such as pulse rate and muscle contractions. This ensures that our feelings and physical reactions are closely linked, no matter which occurs first.
Brain Chemistry
Hormones and neurotransmitters go together like a horse and carriage in one important respect: in the chemistry of love, one cannot go very far without the other. Both can be considered “information molecules” in that they carry signals to cells throughout the body.
Hormones
Hormones, the workhorses of human love and sexuality, are controlled by the hypothalamus and pituitary gland in the lower brain. There are hormones to stimulate and cool sexual desire. Another hormone gives you the urge to cuddle. And two others work by turning an orgasm into an ecstatic experience.
Neurotransmitters
Neurotransmitters are the messengers carrying electrical pulses through a maze of synapses in the brain and through the body’s central nervous system. These signals can be either excitatory or inhibiting as neurotransmitters excite or calm the senses. They also put the body on alert. They control the brain’s reward center. They signal major organs to get busy or relax.
The Nervous System
The central nervous system is one of two main thoroughfares for the body’s messengers and messages. Its neurons or nerve cells communicate with each other by passing along electrical impulses. When they reach a destination, called a receptor site (a muscle, sense organ, or gland), these pulses trigger an action, such as muscle contraction or the release of a hormone into the bloodstream. Each type of neuron performs a different task on a different route of the nervous system.
Sensory neurons carry signals from the internal environment (inside the body) and external environment to the spinal cord and brain, such as “it’s hot outside” or “my stomach is full.”
Motor neurons carry signals and commands from the brain to the muscles and glands of the body, such as “get up and move those legs.”
All Together Now
Now it’s time to see how the central nervous system works with the lower brain and the circulatory and respiratory systems to “make love happen” between two people. Watch how outside stimuli, in this case the actions of a lover, creates bodily reactions in three basic steps.
- Your lover walks in the door and you kiss. Sensory neurons (from the sense organs, e.g., eyes, skin) travel to the thalamus where sensations are processed. From there, neurotransmitters signaling arousal and pleasure travel to the amygdalae, hypothalamus, and pituitary, causing them to release their hormones.
- You are happy to see your lover. Emotional signals go from the amygdalae to the frontal cortex where feelings manifest in your conscious awareness. Other signals from the hypothalamus activate the brain’s reward system, indicating a source of pleasure has arrived. Motor neurons leave the brain to activate the muscles of the heart and lungs. Your heart starts to pound. Breathing intensifies.
You may be wondering if you really need to understand brain science to find a new love interest, or figure out what’s going on with your present lover. No, you don’t. (People get away with it all the time!) But it’s like driving a car without looking under the hood. Sure, you can do it. It’s just that as soon as it breaks down, you’re going to wish you knew a thing or two about how it operates.
From The Complete Idiot’s Guide to the Chemistry of Love by Maryanne Fisher, Ph.D., with Victoria Costello
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