The Endocrine System: Organs and Functions

The endocrine system is crucial for the working of the nervous system as it is used by the latter along with the neurons and neurotransmitters. The endocrine system is a collection of glands that secrete chemicals known as hormones into the bloodstream. The pituitary gland in the brain is usually considered the primary or ‘master’ endocrine gland because it releases hormones that activate the other endocrine glands.

Glands in the Endocrine System

Besides pituitary, other glands in the endocrine system include the thyroid (in the neck), the thymus (in the chest), the adrenal glands and pancreas (near the kidney and stomach), and the gonads (ovaries, testes).

The endocrine system helps maintain regular short-term bodily processes, such as digestion and elimination, as well as regulate long-term bodily processes, such as growth and the development of secondary sex characteristics at the time of puberty.

The endocrine system assumes significance in our body also because it is used by the nervous system along with the neurons and neurotransmitters to send messages. The endocrine system works as a second set of receiver for messages being sent by the nervous system throughout the body using hormones.

Neurotransmitters Versus Hormones

In order to understand this, we need to understand the difference between messages sent by the autonomic nervous system for breathing and by the endocrine system for something like digestion.

To begin with, neurotransmitters are faster; neural signals travel in milliseconds and lead to rapid changes. Hormones, on the other hand, work more slowly. Their effects can require seconds, minutes, or even hours to take place.

However, one of their limitation is their mobility. Neurotransmitters are released from the neuron into the synapse, where they bind to specific receptors on the next neuron. This system is like traveling on a train, where it can operate only if tracks exist between the two points.

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Hormones

Hormones have no such limitation and can trigger different parts of the body to act. They are released from endocrine glands directly into the bloodstream, where they travel throughout the body and can deliver a message to all cells.

Thus, hormones are like traveling by car, where one can drive to many different destinations since there are far more roads than train tracks.

Hormones and neurotransmitters might sound like two totally different things but, interestingly, some hormones work like neurotransmitters and some neurotransmitters work in some ways like hormones. An example of this interchanging roles would be the hormones progesterone and estrogen. Both progesterone and estrogen can bind to specific receptors, just like neurotransmitters, leading to very fast effects.

Similarly, certain neurotransmitters, such as dopamine and serotonin, also work as hormones, regulating the release of various other hormones by the pituitary gland.

Adrenaline

Just like different neurotransmitters have different effects on the body, different hormones play a distinct role in how the body functions. Epinephrine, also known as adrenaline, is the hormone that increases physiological arousal, triggering the ‘fight or flight’ response.

It helps our entire body quickly prepare to respond in times of immediate stress by increasing heart rate, elevating blood pressure, and boosting available energy.

Cortisol

Cortisol, which is often described as the ‘stress hormone’, also helps the body respond to stress, but in a more sustained way, over a longer time frame. Cortisol controls blood sugar levels so the body has enough energy.

It also reduces inflammation, which protects the body in case of injury. And cortisol suppresses non-essential processes, such as digestion, reproduction, the production of growth hormone, and tissue repair.

Oxytocin

Another hormone that plays a very distinct role is Oxytocin. Levels of oxytocin, which is often referred to as the bonding hormone, climb after various types of nurturing behaviors: hugging a loved one, giving birth, having sex.

Oxytocin also creates a reinforcing feedback loop. When a mother stares into her baby’s eyes, the baby’s oxytocin levels rise, causing the baby to stare back into its mother’s eyes, which in turn causes the mother to release more oxytocin, and so on. This positive cycle helps create a strong mother-child bond, which is an essential part of social development.

Although most research with young infants is conducted examining the mother-child bond, there’s no reason to assume the exact same positive oxytocin feedback loop doesn’t work with fathers and babies.

Oxytocin Feedback Loop and Pet Owners

An interesting finding is that this same type of positive oxytocin feedback loop is seen between pet owners and their dogs. Researchers in one study brought in 30 pairs of owners and dogs and collected urine samples from both to measure oxytocin levels. They then asked the pet owners to interact with their dog alone in a room for 30 minutes.

During this time, owners typically petted their dogs and talked to them; sometimes they also gazed into their dog’s eyes. The researchers then collected new urine samples to measure changes in oxytocin levels. Their findings were fascinating. Pairs that spent more time gazing into each other’s eyes showed a substantial increase in oxytocin for both people and dogs!

This discovery may help explain why service dogs can be useful for people with post-traumatic stress disorder.

Hormones and Behavior

These studies on the oxytocin feedback loop also illustrate a broader point: The link between hormones and behavior is bidirectional—hormones influence behavior, but behavior also influences hormones.

Thus, in conclusion, one can clearly observe the vital role hormones play in the working of the endocrine system. All its message-receiving ability rests upon the healthy hormone levels in our body. Only with the help of hormones can the endocrine system continue to works as a receiver for the messages being sent by the nervous system and, in turn, work as a unified system, complementing each other.

Common Questions about the Endocrine System

The pituitary gland in the brain is usually considered the primary or ‘master’ endocrine gland because it releases hormones that activate the other endocrine glands.

The endocrine system helps maintain regular short-term bodily processes, such as digestion and elimination, as well as regulate long-term bodily processes, such as growth and the development of secondary sex characteristics at the time of puberty.

The hormone epinephrine , also known as adrenaline , is the hormone that increases physiological arousal, triggering the ‘fight or flight’ response.

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