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Systems of a Human Organism - Paper Example

6 pages
1461 words
University of Richmond
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The endocrine system is made up of glands, which produce hormones that regulate reproduction, sexual function, tissue function, growth and development and metabolism. The hormones are secreted into the blood as chemical messengers, which transport messages between cells and coordinate other body functions. The main glands are the reproductive organs, pineal body, adrenals, parathyroids, thyroid, pituitary and hypothalamus. The feedback system regulates the endocrine system by sending a signal from the hypothalamus to the pituitary gland, which in turn stimulates the pituitary gland to secrete a hormone into the circulation. The stimulating hormone then signals the target gland to secrete its hormone.

The Excretory System

The main role of the excretory organ is to eliminate waste products in the body through homeostasis. The excretory system involves the kidney system, the lungs, the liver and the sweat glands. For example, in the kidney, the blood arrives through the renal artery that divides into different arterioles. The arterioles enter the Bowman's Capsules of nephrons where through pressure filtration; wastes are excreted from the blood system. Peritubular capillaries also allow substances to be removed from the blood stream. The renal pelvis is responsible for removing urine from the kidney through the ureter. The ureter moves the urine to the urinary bladder. The urine is then released through the urethra from the body. Thus the excretory system regulates the bodys fluid balance, while maintaining adequate water and salt levels.

Nervous System

The nervous system is a collection of specialized cells and nerves called neurons, which transmit signals between different body parts. The nervous system is regarded as the electrical wiring of the body. The system is made up of the peripheral nervous system and the central nervous system (CNS). The CNS is made up of the nerves, spinal cord and brain. The peripheral nervous system is made up of nerves, ganglia and sensory neurons. Functionally, the neurons receive and transmit electrochemical nerve impulses while the dendrites carry nerve impulses into the cell body. However, the cerebrum controls the activities, which balances the body.


Homeostasis within the Human Body

Homeostasis is the stable condition within the internal environment of an organism or the regulation and maintenance of the stable condition that balance the body functions. Maintaining the internal environment requires body adjustments since conditions change between the outside and inside environment. Homeostasis is regulated through chemical regulation, thermoregulation, and osmoregulation. These performances are carried out through the nervous system, urinary system, reproductive system, endocrine system and respiratory system. The body receptors always receive information that the condition in the body is changing, the control center receives the information and the effectors respond by either enhancing or opposing the stimulus. This is a continuous process, which aims at maintaining and restoring the homeostasis. Since the external and internal environments of the body change constantly, adjustments must be made to maintain the equilibrium to balance the body functions. Therefore, homeostasis keeps the environment of the body under control to enable cells to function and live under right conditions.

The Importance of Homeostasis within the Human Body

Feedback Regulation

Body cells are primarily regulated by hormones. The release of these chemicals is based on the body stimulus. Based on the changes of the internal conditions, the body responds to the stimulus leading to either a positive or negative feedback regulation. Positive feedback regulation speeds up the direction of change, for example during lactation, when the baby began sucking, the nerves pass information to the mammary glands that cause the production of prolactin from the pituitary glands leading to the production of milk. Negative feedback is important in maintaining the homeostatic balance by reversing the direction of change to maintain the equilibrium. For example, when CO2 level in the air increases, the body responds by signaling the lungs to exhale the CO2 more while increasing the rate of breathing until the balance is reached.


Homeostasis is critical in maintaining body temperature. In humans the normal body temperature is 37 degrees Celsius. Energy loss or gain must be at equilibrium for the body temperature to remain constant. Temperature receptors in the skin and brain (hypothalamus) help in detecting the external body temperature. The hypothalamus is the processing center that receives information from the skin receptors and triggers the effectors such as muscles or sweat glands to respond to the stimuli immediately. With a high body temperature, the sweat glands release sweat, which cools the body and as a result of vasodilatation more blood flow through the skin capillaries to increase loss of heat. Thus, the hypothalamus and the body receptors triggers responds to the stimuli leading to thermoregulation.


The body carries out osmosis for the proper functioning of the body cells. Osmosis leads to proper biochemical process that balances both sides of the cell membrane to prevent either cell shrinkage or swelling of the cell. By maintaining the stable concentration of solutes through osmosis and diffusion the cells will be able to function properly. Unicellular organisms always release CO2 and waste directly into the environment and utilize oxygen and nutrients directly into the external environment. Multi-cellular organism is made up of cells which assist in exchanging substances between cells.


Chemical reactions in the body are speed up by enzymes. Enzymes require optimal temperature to work. At low temperatures, increase in temperature increases the energy and frequency of the collisions of molecules in the enzyme, which increases the chemical reactions. With increase in temperature enzymes denature and through the lock and key model, only molecules with the correct shape fit into the enzyme as a result of the active sites. For example, chemical reactions occur during release of glucagon and insulin in response of falling and rising blood glucose levels, release of CO2 into exhaled air from lungs and increase in the rate of breathing after an increase the level of CO2 in blood.

How the Endocrine System is involved in Homeostasis

The endocrine system deals with chemical communication through the use of hormones and target cells, which respond to hormones. The system maintains the body functions ranging from growth and development and metabolism. The system also works together with the nervous system in maintaining homeostasis and regulating the internal functions. As chemical messengers, hormones are released by specialized nerve cells or endocrine cells called neurosecretory cells. The endocrine system glands release hormones into the blood stream and transported throughout the body.

Hormones maintain the endocrine system by controlling and maintaining cellular activities. Hormones regulate the functions of the body and controls cellular activities and the responses they draw out. When hormones enter the blood stream, they only respond to target cells. Because of the chemical structure of each hormone, they are recognized by the target cells using the receptors that are compatible with the structure. Released hormones bind to the hormone receptor or built into the plasma membrane. The receptor molecules allow the target cells to the chemical signaling of the hormones. Hormones are either insoluble or soluble based on their biochemical structures. The solubility of the hormone determines how it would react with the target cell.

Lipid soluble hormones such as thyroid and steroids hormones travel across the blood stream thereby affecting the functions of the DNA. Lipid insoluble hormones binds onto the cell surface receptors and the signal is transported using specified secondary messengers into the cell. The hormone sends signal through the membrane and form a secondary messenger, which then binds to an internal regulator that controls the response of target cells to the hormones signals.

Through local signaling, the endocrine system release the regulators into the interstitial fluids and absorbed by nearby cells or through long distance signaling, the endocrine system release hormones in the bloodstream. These hormones travel to the receptor cells and integrate and react to the signal. The hypothalamus is responsible for the secretion of hormones by controlling the pituitary gland which releases hormones.

The adrenal glands are part of the endocrine system. The hormone epinephrine is particularly released by adrenal glands. The moment the body is placed in conditions, which are unsafe bothe the nervous and endocrine system become operational. The reaction of the body to unsafe situations leads to an increase in the level of fatty acids and glucose in the blood stream and increases pulse rate, which increases blood flow to the muscles, brain and heart. The epinephrine changes thereby changes the body to a situation of tenseness and readiness.

The pituitary gland produces hormones that help in the functioning of the endocrine system. The antiduretic hormone and oxytocin released by the pituitary glands acts to help the kidney reabsorb water and causes the mammary glands to release milk. The release of these hormones is caused by neurosecretory cells in the hypothalamus. The hypothalamus also releases inhibiting...

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