What Exactly Is A Gland?
When you think of glands, don’t just think of the thyroid, don’t underestimate your adrenals. In fact, you may not realize what your glands are doing for you until they stop doing. Let’s take a look at just how our glands to work. OK, what exactly is a gland anyways? After all, they are an important part of my body and I’d like to know what they do for me? Well, when we talk about your thyroid, your pituitary or the adrenals, we are talking about glands. Glands are kind of like organs, except that glands whole purpose is to make chemicals, store chemicals and then release chemicals. The system that contains all the glands is called the Endocrine System and the chemicals that glands produce, use and release are known as hormones. Just as the nervous system uses impulses that can produce an effect within a millisecond, the endocrine system uses hormones that can produce a rapid response as well, such as adrenaline. But unlike the nervous system, the glands can also be slow and persistent in their response. This second type of response is the more common since it provides day-to-day maintenance and growth such as the thyroid hormone thyroxine.
Glands secrete hormones that either stimulate or inhibit function. Hormones are different from enzymes (think of your digestive enzymes) because enzymes act as a catalyst that speed up chemical reactions. Hormones are coded to be received by and to activate certain cell sites in the body known as receptors. Each type of receptor is activated by a particular hormone, almost like a key in a lock. Hormones often have to be carried from the gland where they are made to the place where their receptors are located. Sometimes receptors can be found for a particular hormone all through the body, not just in one spot. Also, while the hormone is being carried to its destination, it remains inactive or in a kind of stasis. Once they reach their target tissues, they bring about a chemical reaction making the hormone metabolically active.
The Endocrine system is exactly that... a system working together as a system. So although each gland may have certain functional control based on the hormones that particular gland releases, all the glands work together to achieve a balance of your entire body which is consistent through the day and also day after day. This system doesn’t just contain glands, there are also sections of glandular tissue that are found within organs (such as the liver) which also act to maintain a constant balance of important functions such as metabolism, nutrient levels and energy balance.
Hormone secretion is controlled by signals from the nervous system, chemical changes in your bloodstream and other hormones. Most often, these signals are monitored constantly for their effects, in order to increase or decrease the hormonal response. This is called negative feedback. This explains the holistic approach to body function, because we would want to treat an entire system to maintain the delicate balance of the body, not just one gland individually. Without taking the entire system into account, you can create as many problems as you may solve by just focusing on the thyroid, or just the gonads.
Harrower’s Chart is one of the most comprehensive views of the interrelationships between glands in the Endocrine system. There are two types of glands, exocrine glands that secrete their products into ducts that carry the secretions into body cavities or onto the surface of the body [sweat glands, goblet cells in the digestive system, salivary glands]. The second type of gland are endocrine glands which secrete their products into the extracellular fluid around the cell, which then passes into the bloodstream through the capillaries [thyroid]. There is even endocrine tissue that is only one cell in size and that can be mobile (immune cells) moving throughout our lymphatic and blood systems.
So how do glands and glandular tissue know how much hormone we need at any given time? Well, the negative feedback system is part of that, which includes the nervous system. But also there is the number of any particular receptor at any given time. When a specific hormone is present in abundance the number of receptors for it will decrease to prevent an imbalance from occurring and when the hormone is present in less amounts, the number of receptors will increase. This is one way of the body regulating hormone activity for homeostasis. Sometimes an underactive gland, such as the thyroid, really isn’t underactive, but simply has overproduced, causing receptors to lessen. This can happen especially during periods of stress. In fact, stress is the most crucial determinant of glandular function. Severe stress can even cause the adrenal glands to wear out their reserves of hormones, causing fatigue, body pain, emotional instability and fluid retention.
Hormones that must circulate through the blood to reach more distant target tissues include steroids such as cortisol, amines produced from amino acids such as histamine and proteins such as insulin. Many of these, such as cortisol, are lipids making them difficult to transport through the blood. These rely on transporter proteins synthesized by the liver to make them temporarily water-soluble. If blood flow is compromised because of stress, muscle tension or other imbalances, then many hormones will have no mode of transportation to target tissues. Other hormones are localized reaching target cells close to their release site such as eicosanoids, which mediate inflammation. Some hormones even act on the same cell that secretes them.
There is also a lot of research in the last few years that is indicating that we may have many more hormones than we imagined, and many more receptors than we imagined. We may even have biochemicals that can act as hormones and also act as neurotransmitters for the nervous system. This means that emotion can interact with our gland system as much if not more than we traditionally thought. This also means that your immune system may be controlled to some extent by the chemicals of emotion. For this reason, stress, fear, anxiety, sadness, can all profoundly change how our body works.
So perhaps the first place to look for answers is within our emotional lives. After all emotions are what motivate us, control us, direct us, reward us. Listening to your "gut" may be the best advice after all....