3.3 THE ROLE OF HORMONES IN HUMANS

• Hormones are protein secreted from endocrine glands in our body.

• They are chemical messengers secreted directly into the blood stream, which carry them to their target cells/organs in another part of the body.

• Hormones are release in small quantities.• Hormones are specific in action, acting only on

their target cells.• Hormones are slow to act but their effects also

last longer.

The Endocrine System

Hormones Hormones!!!

• The endocrine system is made up of endocrine glands,

which secrete hormones to coordinate body activities in response to stimuli from the

environment.

• It works together and complement the nervous

system form body coordination.

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• Endocrine gland are ductless glands.

• They do not secrete hormones through ducts.

• The hormones are secreted directly into the blood stream, which distribute them all over the body.

• Each glands secreted different types of hormones.

Human Endocrine System

• Function of hormones can be divided into three main categories:

o Reproductiono Growtho homeostasis

Regulation of Hormone secretion

• Hormone secretion is need to be regulated to prevent over-production and under production.

• Hormone secretion is regulated by:Other hormonesLevel of certain substances in the bodySignals from the nervous system

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• The pituitary gland is regarded as the master of the endocrine gland because it secretes several hormones that control other endocrine gland.

• However the pituitary gland has its own master the hypothalamus.

• hormone secretion regulated by the negative feedback mechanism:

when gland X releases hormone X, this stimulates target cells to release hormone Y.

When there is an excess of hormone Y, gland X "senses" this and inhibits its release of hormone X.

“Fight & Flight” situation• When a person is in a stressful situation, the

nervous & endocrine systems both will work together to bring about immediate responses

to cope with the approaching danger.

Hormonal Imbalance

• Hormonal imbalance can be result of too much (excessive) or too little (deficiency) of hormones produced.

• Because the endocrine system coordinates long term changes in our body,

• any imbalance in the production of hormones affects our health.

Pituitary Gland

Function: It secretes nine hormones that directly regulate many body functions and controls functions of other glands.

Disorders: To much growth hormones (GH) in early childhood can result in a condition called gigantism. To little GH can result in Pituitary Dwarfism.

Robert Wadlow

Thyroid Gland• Function: plays a major role in

regulation the body’s metabolism.• Disorders: If the Thyroid Gland

produces to much Thyroxin, it can cause a condition known as Hyperthyroidism. If to little thyroxin produces it is called Hypothyroidism.

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Pancreas• Function: The Insulin

and Glycogen in the Pancreas help to keep the level of glucose in the blood stable.

• Disorders: When the Pancreas fails to produce or properly use Insulin, it can cause a condition known as Diabetes Mellitus.

Adrenal Gland • Functions:

-The adrenal glands release Adrenaline in the body that helps prepare for and deal with stress.-Also regulates kidney function.

Ovaries• Functions:

–Pair of reproductive organs found in women that produce eggs.

–Also secrete estrogen and progesterone, which control ovulation and menstruation.

Testes• Functions:

–Pair of reproductive glands that produces sperm.

–Also secrete Testosterone to give the body its masculine characteristics.

Interaction of GlandsThe hypothalamus is located in the brain and controls the release of hormones from the pituitary gland. It is an important link between the endocrine and nervous systems.

http://www.biocfarm.unibo.it/aunsnc/images/3D%20Objects/Hypothalamus.gif