Identify how hormones work.

Reticular Formation (Arousal)

Sometimes the brain ignores the division of lobes, sections, parts, or systems so that a very strong alert or emergency message can be sent. Inside the brainstem is the reticular formation (main part of the reticular activating system (RAS). This is a system of neurons networking the hindbrain, midbrain, and the forebrain to alert our attention to emergent or important neural messages. It also helps us block out other messages that are not emergent or important. Letting yourself become involved with the main character in a book you are reading to the point that you ignore that the house is burning down around you is possible through the reticular formation. The reticular formation helps keep you awake as well. If you could only activate this system at will, you could study, drive, or do anything without getting drowsy or sluggish.

Limbic System (Hippocampus, Hypothalamus, Pituitary Gland)

The limbic system is a ring of structures surrounding the thalamus. This system actually includes the hypothalamus, part of the thalamus, and several other forebrain structures. Learning, emotional behavior, and memory are greatly affected, even regulated, by the limbic system. The hippocampus is essential in assisting short term memory to become long term. The amygdala is associated with rage, fear, and hunger. The hypothalamus is also associated with hunger along with sexual behavior, thirst, and stabilizing body temperature. The pituitary gland is directly controlled by the hypothalamus.

Speech functions are generally found in the left hemisphere of the cerebral cortex. Paul Broca (1865) observed that when damage occurs in a specific area of the left frontal lobe, called Broca’s area, people were unable to form words unless previously memorized, such as reciting poetry. Carl Wernicke (1874) found that a damaged left temporal lobe location, Wernicke’s area, resulted in speaking real words in disconnected/nonsensical ways and not comprehending language.

The spinal cord is the complex cord or cable of nerves inside of what we usually call our backbone. This cord connects the brain to the rest of the body. Most messages go from the body to the spinal cord, then up to the brain, then back to the spinal cord, and then finally back to the body. Simple reflexes, however, go from the body to the spinal cord, and then go immediately back to the body. The reflex arc of simple reflexes (stimulation to the sensory neuron, then immediately to the interneuron, then quickly back to the motor neuron) allows simpler and quicker reactions to protect the body from harm. This elimination of the brain’s direct involvement and decision-making ensures that reaction time is dramatically quicker in simple reflexes.

Peripheral Nervous System (Neurons: Sensory, Interneurons, & Motor)

The Peripheral Nervous System connects the rest of the body to the brain and spinal cord of the central nervous system. Within the peripheral nervous system, there are different types of neurons that carry information between the body’s parts and the brain. Sensory neurons carry information from tissues and sensory organs to the spinal cord and brain. When sensory neurons are densely arranged, we experience more sensitivity. For example, lips have the highest concentration of sensory neurons and are very sensitive to touch. In contrast, the skin on the arm does not have as densely arranged sensory neurons. This internal communication from tissues and organs to the brain is next transmitted through the use of interneurons. The brain and spinal cord then send messages back to the body through the use of motor neurons.

Somatic Nervous System (Skeletal Muscles) and the Autonomic Nervous System (Internal Organs: Sympathetic and Parasympathetic)

There are two major divisions of the peripheral nervous system: somatic and the autonomic nervous systems. The somatic nervous system controls your skeletal muscles, which move your bones. This system controls voluntary movement. Signing your signature or adjusting your position when you’ve been sitting the same way too long is done through your somatic nervous system. The autonomic nervous system carries all the messages between your brain and your internal organs and glands. It is an automatic pilot for your body; your organs like your heart and stomach will pump and digest whether you think about them or not. After head injuries, the eyes’ dilation is often checked to see if the automatic nature of the autonomic system is still working. Unless you make an extremely conscious effort to control this system, it’s on its own. This system has two basic functions: to arouse you or to calm you. The arousing sympathetic system is the division of the autonomic nervous system, which defends, arouses, accelerates, and increases the activity of internal organs. In a nutshell, this system gets you ready for action and causes the following organ reactions: pupils dilate (open wider), heart accelerates, blood sugar increases, tear glands secrete (you cry or tear up), sweating increases, salivation decreases (dry mouth), digestion decreases, adrenaline increases, and bladder relaxes. The calming parasympathetic system is the division that decreases activity within the body to return a state of homeostasis after the arousal of the sympathetic system. Homeostasis is a condition of balance between full arousal and full inactivity (sleep) so that energy can be conserved. The parasympathetic system contracts (closes, narrows) the pupil, slows the heart, decreases blood sugar, inhibits tears, decreases sweating, increases salivation, increases digestion, stops adrenaline, and contracts the bladder.

Endocrine System (Hormones)

Another system that is interconnected with our nervous system is called the endocrine system. The endocrine system secretes the chemical substances called hormones. After being secreted, hormones are carried to glands and other parts of the body through the blood stream. When carried to the brain and glands through the bloodstream, hormones can affect our vitality, metabolism, growth, sexual development, and our emotional responses to or interest in sex, aggression, and food. Hormones are slow to act, but also slow to die. Our bodies have the following major endocrine organs or glands: hypothalamus, pituitary gland, thyroid gland, parathyroid, adrenal glands, pancreas, ovaries, and testes.

Hypothalamus and Glands: Pituitary, Adrenal, Pancreas, and Gonads

The hypothalamus is not an endocrine gland, but it directly controls the pituitary gland. Because of its interconnection, I list it as part of the endocrine system. The pituitary gland is commonly called the “major gland” because it influences or controls the release of hormones from other endocrine glands. It could not function without the hypothalamus, however, so the major gland’s boss would be the hypothalamus. With the hypothalamus’ help, the pituitary gland produces the largest number of different hormones affecting the widest range of body functions through its influence on the rest of the endocrine system. Beyond affecting body functions, it also regulates contraction during childbirth, milk production after childbirth, blood pressure, retaining water weight, body growth, sexual arousal, and sexual development.

A good friend of mine acquired a tumor on his pituitary gland when he was in his mid-thirties. At first, he was not aware of what was happening and why. The tumor’s effect on his pituitary gland resulted in the gland sending unnecessary growth messages to his skeletal system. Most people’s bones stop growing during adolescence or early twenties, but my friend’s bones didn’t stop growing until his thirties. Because mature bones develop caps on their tips that stop further lengthening, the only further growth possible was through the thickening of his bones and increasing cartilage mass. His entire body frame, hands, feet, chin, eyebrows, and other bones widened and thickened through his growing bone structure. In spite of rare periods of reflective musings in which he would regret that this growth had not happened years earlier when he was playing high school and college football, this abnormal growth terrified him. Not only did he experience unexplained growth, but his emotions also became difficult to manage. His sexual drive was significantly reduced. His increased anger and moodiness added to the horror of the abnormal growth that finally scared him into searching for answers. His answers came through the CT and MRI scans he received that took pictures of the tumor.

The tumor was surgically removed. The symptoms described above have been lessened, but the tumor and surgical removal have resulted in a continued need to take hormone medication because of the permanent pituitary damage. His testosterone, cortisone, and thyroid are no longer produced naturally under the pituitary’s regulation. Even today, if he does not take the hormone medication as prescribed, he faces the certainty of death.

The adrenal glands are found just above the kidneys. These glands respond to stress and danger by giving us great energy, strength, and speed. Adrenaline (epinephrine) and noradrenaline (norepinephrine) are secreted at the need for “fight or flight.” In addition to increasing body speed and strength, the adrenal glands also help to kill pain.

Other glands affected by the endocrine system are the pancreas and gonads (sexual organs). The pancreas regulates the level of blood sugar found in our blood stream. Because sugar increases body activity, the endocrine system’s effect on the pancreas’s blood sugar regulation definitely affects body activity.

The adrenal glands work with the gonads (testes in males; ovaries in females) to stimulate the maturation of reproductive organs. Influenced by the hormones from the gonads, secondary sexual characteristics appear. These include voice change, shape and fat concentration of the body, pubic hair, beards, and breast growth. The sexual drive is definitely affected by these hormones also. The difference between your sexual and romantic feelings and thoughts during kindergarten years compared with those during high school years is certainly evidence of the effects of the gonads.