THE ENDOCRINE SYSTEM

By: Kasey Carns & Amberly Anderson

Major Glands/Organs

HypothalamusRoles/Functions:

• The portion of the brain that maintains the body's internal balance (homeostasis)

• The hypothalamus is the link between the endocrine and nervous system.

• Produces releasing and inhibiting hormones, which stop and start the production of other hormones throughout the body.

Pituitary (the master gland)

Roles/Functions:

• Help regulate the functions of other endocrine glands.

• The hypothalamus sends signals to the pituitary to release or inhibit pituitary hormone production.

Pineal Gland

Roles/Functions:

• Produces melatonin, which helps maintain circadian rhythm and regulate reproductive hormones.

ThyroidRoles/Functions:

• Regulates your metabolism, which is your body's ability to break down food and convert it to energy.

AdrenalRoles/Functions:

• The adrenal cortex (outer part): Produces hormones that are vital to life, such as cortisol (which helps regulate metabolism and helps your body respond to stress) and aldosterone (which helps control blood pressure)

• The Adrenal Medulla (inner part): Produces non-essential hormones, such as adrenaline (helps you react to stress).

PancreasRoles/Functions:

• Maintains the body’s blood glucose balance.

• Primary hormones of the pancreas include insulin and glucagon.

Thymus glandRoles/Functions:

• Thymosin is the hormone of the thymus, and it stimulates the development of disease-fighting T cells.

• Located behind your sternum and between your lungs but is only active until puberty.

• After puberty the thymus gland starts to slowly shrink and become replaced by fat.

Female Gonads (Ovaries)

Roles/Functions:• Maintains the health

of the female reproductive system.

• They secrete two main hormones: estrogen and progesterone, which are vital to normal reproductive development and fertility.

Male Gonads (Testes)Roles/Functions:

• Secrete testosterone, which is necessary for proper physical development in boys.

• In adulthood, testosterone maintains muscle strength and bone density.

Positive vs. Negative Feedback

Negative feedback controls the rate of a process to avoid accumulation of a product. The rate of a process will continuously accelerate under positive feedback as long as substrate is available.

Negative FeedbackStimulus response chain: Destabilizing stimulus is sensed. Hormone secretion is triggered. Hormone activity lowers to bring process back to pre-

stimulus state.

Example:When blood calcium level drops, parathyroid glands sense that and secrete hormones that cause release of calcium from bone. Blood calcium levels return to normal, secretion stops.

Positive Feedback

In childbirth, stretching of uterus brings out production of hormones that stimulate contraction of uterine muscles; this leads to more stretching of uterus, more hormone secretion, more muscle contractions; loop is broken upon birth of a baby.