The Endocrine System Michael TarPey

Hypothalamus- A region of the forebrain below the thalamus that coordinates both the autonomic nervous system and the activity of the pituitary, controlling body temperature, thirst, hunger, and other homeostatic systems, and involved in sleep and emotional activity.

Pituitary Gland- The major endocrine gland. A pea-sized body attached to the base of the brain, the pituitary is important in controlling growth and development and the functioning of the other endocrine glands.

Pineal Gland- A pea-sized conical mass of tissue behind the third ventricle of the brain, secreting a hormonelike substance in some mammals.

Thyroid/Parathyroid- A large ductless gland in the neck that secretes hormones regulating growth and development through the rate of metabolism.

Thymus- A lymphoid organ situated in the neck of vertebrates that produces T cells for the immune system. The human thymus becomes much smaller at the approach of puberty.

Pancreas- A large gland behind the stomach that secretes digestive enzymes into the duodenum. Embedded in the pancreas are the islets of Langerhans, which secrete into the blood the hormones insulin and glucagon.

Adrenals- Relating to or denoting a pair of ductless glands situated above the kidneys. Each consists of a core region ( adrenal medulla ) secreting epinephrine and norepinephrine, and an outer region ( adrenal cortex ) secreting corticosteroids.

Testes(Male)- An organ that produces spermatozoa (male reproductive cells).

Ovaries(Female)- A female reproductive organ in which ova or eggs are produced, present in humans and other vertebrates as a pair.

Placenta(Pregnancy)- A flattened circular organ in the uterus of pregnant eutherian mammals, nourishing and maintaining the fetus through the umbilical cord.

Hormone- A regulatory substance produced in an organism and transported in tissue fluids such as blood or sap to stimulate specific cells or tissues into action.

2 Types of Hormones

In a peptide hormone, the hormone itself does not enter the cell. Once the target cell is reached, the hormone binds to a receptor on the plasma membrane. This triggers the production of enzymes on the inside of the cell, like cAMP. The activation may hinder or aid many other processes.
In a lipid soluble hormone, the hormone is able to enter the target cell that it reaches because the plasma membrane is made of phospholipids. It enters the nucleus with the same type of membrane and is able to directly affect the gene expression once it comes in contact with the DNA.

Positive and Negative Feedback

Positive Feedback- The enhancement or amplification of an effect by its own influence on the process that gives rise to it.

When a hormone is concentrated in high amounts, the body area responds with increased secretions.

Ex. Child Birth in Female bodies

Negative Feedback- The diminution or counteraction of an effect by its own influence on the process giving rise to it, as when a high level of a particular hormone in the blood may inhibit further secretion of that hormone, or where the result of a certain action may inhibit further performance of that action.

When a hormone is secreted, sometimes it causes negative feedback, inhibiting the production of secretions.

Ex. Body's control of blood sugar

Pituitary Gland- The pituitary is an important gland in the body and it is often referred to as the 'master gland', because it controls several of the other hormone glands (e.g. adrenals, thyroid). It is usually about the size of a pea and communicates with the hypothalamus.

Luteinizing Hormone:

This hormone is produced by the pituitary gland

This hormone regulates the female menstrual and egg production, which is known as ovulation

LH surge: a rapid increase in the amount of luteinizing hormone being produced right before ovulation

It also stimulates the production of testosterone in men, which eventually leads to the production of sperm

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