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. Nervous System and Immune System/ Skeletal System, Muscular System, and Integumentary System/ Digestive System and Excretory System/ Digestive System and Excretory System

Terms in this set (39)

The endocrine system regulates the body's metabolism, growth, and functions of sexual organs. It consists of glands which secrete chemicals directly into the bloodstream. These chemicals are known as hormones. Hormones control the functioning of organs.

The main gland of the endocrine system is the pituitary gland. The pituitary gland, located at the base of the brain, controls and regulates all the other glands. It also controls the body's rate of growth. How fast you grow and how tall you eventually become is dependent upon the pituitary's excretion of growth hormones. Growth hormones act as messengers, telling your bones and tissues to create more cells, thus producing growth. Other glands of the endocrine system include the pancreas, the thyroid, the parathyroid, the adrenal, and the reproductive glands.

The pancreas, a gland near the stomach, produces the hormones insulin and glucagon, which regulate blood sugar. You have already learned that the pancreas is also responsible for secreting digestive chemicals into the small intestine. With multiple functions, the pancreas is part of the endocrine system and the digestive system

The adrenal glands are located near the kidneys. They produce a hormone called epinephrine or adrenaline. This hormone initiates the "fight or flight" reaction.

The thyroid gland is located near your larynx in your neck. This gland is responsible for regulating the body's energy. If the thyroid gland is functioning improperly, the body may experience problems. An overactive thyroid may cause a nervous or overactive reaction while an underactive thyroid can cause fatigue and weight gain. The parathyroid gland is located behind the thyroid gland and regulates calcium levels in the body.

The reproductive glands are different for males and females. Female reproductive glands are called ovaries. The ovaries produce egg cells for reproduction. Male reproductive glands are called testes or testicles. These glands produce sperm cells for reproduction.
The reproductive system has four main purposes. As mentioned above in our discussion of the endocrine system, the reproductive system must produce hormones. It also produces reproductive cells, egg cells for females and sperm cells for males. In addition, the reproductive system must transport and sustain these cells. Finally, the reproductive system must nurture the developing offspring. Since female egg cells and male sperm cells meet in the female body in order to reproduce, the task of nurturing developing offspring is unique to the female reproductive system.

In form and function, the reproductive organs of the female differ from that of the male. The reproductive system of a female is located internally around the pelvic area. The main organs of the female system are the vagina, uterus, fallopian tubes, and ovaries. The ovaries produce the egg cells that are necessary for reproduction. When an egg is produced in an ovary, it migrates through the fallopian tubes toward the uterus. If an egg cell is fertilized by a sperm cell, it is implanted in the uterus. This is where a fetus grows and develops. When a baby is ready to be born, muscular contractions push it from the uterus, through the vagina, and into the world!

Unlike the female reproductive organs, the male reproductive organs are located internally and externally around the pelvic area. These reproductive organs are the testicles, the duct system, the accessory glands, and the penis. Testicles are responsible for producing the male reproductive cells, sperm. As you learned earlier, testicles are also part of the endocrine system. Sperm travels through the duct system to get from the testicles to the penis. The accessory glands lubricate and nourish the sperm as they travel through this duct system. The penis is the site where sperm cells are able to exit the male body in order to fertilize an egg cell.

Conception or fertilization occurs when the female gamete (egg cell) is fertilized by the male gamete (sperm cell). Both the female and the male reproductive systems are necessary for reproduction to occur.
The purpose of the nervous system is to gather, interpret, respond to, store, and retrieve information. The nervous system is comprised of the central nervous system (CNS) and the peripheral nervous system (PNS).

The central nervous system consists of the brain and the spinal cord. As the main component of the nervous system, the CNS receives information from sense organs, analyzes the information, and initiates a response which is carried to the designated body part via the peripheral nervous system. The PNS links the CNS to the rest of the body.

The brain has several major parts. The cerebrum is the largest part. It enables you to think, to feel emotions and to control your body. The cerebrum has two sides. The left side of the cerebrum controls the right side of your body and the right side of your cerebrum controls the left side of your body. The left side of the cerebrum deals with concrete things like math and speech, while the right side deals with abstract things like art and music.

Another part of the brain, the cerebellum controls coordination and posture. The cerebellum also helps you keep your balance. The medulla, a part of the brain stem, controls your vital functions. The medulla keeps organs like your intestines and lungs working and controls your blood pressure. Nerves from all parts of the body connect to the cerebrum and cerebellum through the brain stem.

The basic unit of the nervous system is a neuron, or nerve cell. A neuron transmits information in the form of an electrical impulse. Impulses can travel from neuron to neuron at speeds close to several hundred miles per hour.

As the central control unit of the body, the nervous system coordinates the body's systems via the autonomic nervous system and the somatic nervous system. The autonomic nervous system sends signals to certain organs so that they function without your conscious thought. For instance, you do not have to think about your stomach churning for it to digest your food. Your brain just tells your stomach to churn.

The somatic nervous system sends signals to muscles that are controlled voluntarily. For example, you have to think about whether you want to walk or run. Your legs are controlled by the somatic nervous system.
The purpose of the digestive system is similar to that of the respiratory system. It prepares needed energy and building supplies for absorption by the cells. The digestive system is a long tube that stretches from the mouth to the anus. The tube is also known as the digestive tract. As food passes through the digestive tract, it is broken down into a substance that can be easily absorbed into the bloodstream.

The digestion process begins in the mouth. Teeth, salivary glands, and the tongue work together to break down the food into a substance that can be easily swallowed. The teeth tear and smash the food. The salivary glands secrete enzymes, which prepare the food for digestion in the stomach. The tongue manipulates the food in the mouth until it is well lubricated and chewed. The tongue then pushes the food into the pharynx. The pharynx seizes the food and forms it into small balls, which are pushed into the esophagus. The esophagus transports the balls of food into the stomach.

As mentioned previously, the stomach mixes the food with powerful chemicals to further the digestive process. The powerful chemicals, known as gastric juices, break down the food into a thick liquid substance called chyme. The stomach also functions as a storage tank, holding food until it passes into the small intestine. The small intestine secretes salts, acids, and enzymes, which continue the breakdown of proteins, fats, and carbohydrates. These digestive juices originate in the liver, gallbladder, and pancreas.

Nutrients are absorbed into the blood-stream through small finger-like nodules on the wall of the small intestine called villi. Chemicals and other substances that cannot be digested by the body are passed into the large intestine. Villi in the large intestine absorb most of the water and the remaining amounts of vitamins and minerals in the food. The undigested substance, known as feces, is expelled from the body through the anus.