Controller of the Human Body

The nervous system “is often referred to as the master controller of the human body, the nervous system is specialized for communication of information from one part of the body to another”. This system used neurons to communicate throughout the body. “The endocrine system regulates biological processes through the release of chemicals called hormones. Hormones are released into body fluids—usually blood, which carries these chemicals to their target cells, where they elicit a response” . A big difference between the two systems is how they communicate; the nervous system communicates through electrical responses and the endocrine system uses hormones or chemical signals to carry out commands. The nervous system releases quick responses within the body while the endocrine system releases responses from a few seconds to a few days depending on what is going on in the body. Both systems are used to communicate with our bodies and make sure that everything stays in working order.

The endocrine glands are located throughout your body, from your head down to your reproductive organs. The endocrine glands that are located throughout the human body are as follows: “the hypothalamus, Pituitary gland, Thyroid gland, Adrenal gland, Pancreas, and the gonads” (Environmental Protection Agency). The endocrine glands are stimulated to synthesize and release hormones in three different regulations, humoral, hormonal, and neural. “Humoral stimuli regulate the release of hormones in response to specific changes in extracellular fluids, with tropic hormonal stimuli, a hormone is produced and released by an endocrine gland in response to another hormone (known as “tropic hormones”), and the nervous system can also directly stimulate endocrine glands to release hormones through a mechanism known as neural stimuli” . The functions of the endocrine glands are to help regulate our metabolism, growth and development, sexual function, mood even our emotions and sleep.

To get a better understanding of the endocrine system let’s break down the terminology of the word; endo-, meaning “within,” and -crine, meaning “to secrete.” The endocrine system includes the organs of the body that secrete hormones directly into body fluids such as blood. It is the second controlling system of the body as the nervous system is the fast-control system. This is because the responses are hormonal, oppose to electrical. Also meaning the responses take a bit longer to subside verses the nervous system because enzymes are required to break them down in the bloodstream.  

Endocrine glands are ductless glands. This means they release their hormones directly into the tissues they act upon or into the bloodstream, which carries the hormone to the target cells. Hormones are chemicals secreted by a cell that affect the functions of other cells. Once released, most hormones enter the bloodstream, which transports them to their target cells. A hormone’s target cells are those that contain the receptors for the hormone. A hormone cannot affect a cell unless the cell has receptors for it, in much the same way that doors require a specific key to unlock it.

Hormones help to regulate the chemical reactions within cells. They therefore control the functions of the organs, tissues, and other cells. On a larger scale, hormones control several major processes. For example, reproduction, growth and development, mobilization of body defenses, maintain homeostasis, and regulation of metabolism. Hormones are classified chemically as amino acid–based, which includes proteins, then there are steroids which are produced from cholesterol. Many hormones in the body are derived from steroids. Steroids are soluble in lipids (fats) and therefore can cross cell membranes easily. Once a steroidal hormone is inside a cell, it binds to its receptor, which is commonly in the cell’s nucleus. The hormone-receptor complex turns a gene on or off. When new genes are turned on or off, the cell begins to carry out new functions, and this is ultimately how steroidal hormones affect their target cells. Examples of steroidal hormones are estrogen, progesterone, testosterone, and cortisol. However, nonsteroidal hormones aka proteins cannot easily cross the cell membrane. Therefore, these hormones bind to receptors on the cell’s surface. The hormone-receptor complex in the membrane usually activates a G-protein. The G-protein causes enzymes inside the cell to be turned on. Different chemical reactions then begin inside the cell, and the cell takes on new functions. Hormone levels are controlled by a mechanism known as a feedback loop, which can be negative or positive. More often times our bodies project negative feedback loops.

Carbon Dioxide is a necessity when it comes to the human body. Oxygen is taken in by inhaling through the lungs. The oxygen is then passed through the blood stream to parts of the body where the oxygen is then turned in to carbon dioxide. The CO2 is then returned back to the lungs via blood stream, where it is then exhaled through the lungs. CO2 regulation is important to the pH balance in the body. Too much CO2 can cause respiratory acidosis. This is maintained by the chemoreceptor reflex. There are two types of chemoreceptors; peripheral and central. Peripheral chemoreceptors are located in the carotid and aortic bodies. The central chemoreceptors are located near the surface of the medulla.

Cellular respitory converts nutrients and oxygen are broken down to create energy. CO2 is a product of this formula. Gas exchange at the tissues results in diffusion of CO2 produced by respiration from the tissues into the blood, while O2 is offloaded from hemoglobin in red blood cells to replenish tissue oxygen stores.  

“Your digestive system is made up of the gastrointestinal (GI) tract and your liver, pancreas and gallbladder. The GI tract is a series of hollow organs that are connected to each other from your mouth to your anus. The organs that make up your GI tract, in the order that they are connected, include your mouth, esophagus, stomach, small intestine, large intestine and anus. ” (Cleveland, 2018).

The digestive system begins with your mouth. Even before you actually take a bite of food, your saliva begins to get ready to start breaking down food. Once you have taken a bite of food and chew it, your tongue then pushes the food back into your esophagus. The esophagus then closes the epiglottis to keep you from choking on the food. Muscular contractions of the peristalsis helps the esophagus to push the food down into your stomach. The stomach contains enzymes and acid that help break down the food further. Once the stomach has broken down the food enough, it then releases the food into the small intestines. The small intestines is a 22 foot muscular tube that helps further break down food in three different areas. The first is the duodenum that breaks down the food even further. The second and third part is the jejunum and ileum. This is where the nutrients are absorbed into the bloodstream and the food is now broken down into a liquid form. The pancreas, liver, and gall bladder all help with the breakdown process and absorption of nutrients. The final part of the digestive system is the large intestines. This is a 6 foot muscular tube that is responsible for emptying the bowels.

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