Endocrine System

Endocrine System

Endocrine System • The endocrine system includes the endocrine glands and their hormones • The function of the endocrine system is to secrete hormones into the bloodstream. • Hormone: A chemical messenger which targets a specific group of cells, in order to cause that group of cells do some activity or stop doing an activity.

Endocrine System • Exocrine glands release their secretions into ducts, or tubes – Liver Bile released into the gallbladder, then through a duct into the small intestine – Pancreas releases pancreatic juice into the small intestine via a duct

• Endocrine Glands are called ductless glands – Release hormones directly into the bloodstream – Blood transports hormones throughout the body – Each hormone acts on only a certain kind of tissue called its target tissue

Endocrine System • Each hormone acts on a certain kind of tissue called its target tissue

Human Endocrine Glands • • • • •

Pituitary Thyroid Parathyroid Adrenal Pancreas (Islets of Langerhans) • Testes and Ovaries

Pituitary

• Pituitary gland is a round organ about the size of a pea (~1 cm in diameter), located behind the bridge of the nose at the base of the brain • Secretes 9 different hormones, which affect many different areas of the body, including: • • • • • • • • •

Growth Blood pressure Regulation of Pregnancy Breast milk production Sex organ functions in both men and women Thyroid gland function Metabolism Water regulation in the body (kidneys) Temperature regulation

Two parts of Pituitary Gland • Anterior Lobe – Master gland – Secretes 7 hormones which are folliclestimulating hormones, luteinizing hormone and proclatin

• Posterior Lobe – Secretes two hormones – Oxytocin

A Few Pituitary Hormones Hormone Growth Hormone (GH)

Function To increase body size during childhood and adolescence; to maintain body size during adulthood

To stimulate the thyroid to produce Thyroid Stimulating Hormone thyroxin (TSH) Follicle Stimulating Hormone (FSH) Regulate puberty, development, and reproductive processes Luteinizing Hormone (LH) Stimulates the production of estrogen and testosterone

Growth Hormone • Oversecretion of growth hormone: – Giantism in childhood and acromegaly in adults (bones of face, hands and feet enlarge)

• Undersecretion of growth hormone: – Dwarfism in childhood

Hypothalamus • Part of brain and attach to the pituitary gland. • Control the secretion of the pituitary gland

Neurons of the Hypothalamus • Regulate the secretion of anterior lobe by secreting releasing hormones.

What is the relationship of pituitary and hypothalamus then? -It links the interaction of the Nervous system and the Endocrine system

Hormones involved in the reproductive system • During puberty, Hypothalamus secrete Gonadotropin hormone (GnRH) which is secreted to the blood into the anterior lobe of the pituitary gland. • GnRH will activate the release of luteinizing hormone (LH) and Folliclestimulating hormone (FSH)

Male Sex Hormones • Testosterone- primary male sex hormone. • Testosterone stimulates the maturity of the male reproductive system (SPERMATOGENESIS) • Helps in the development of the secondary sexual characteristics

Female Sex Hormones • Estrogen and Progesterone • Estrogen- stimulates the maturation of the female sex organs and development of ovum (OOGENESIS) • Helps in the development of the secondary sexual characteristics

• Progesterone- develop and maintain the uterine lining in pregnancy • Prevents the uterine contractions and dilation of the cervix • Prepares the mammary glands for milk production • Proclatin- a hormone that maintains the production of milk after the birth of the child • Oxytocin- stimulates contraction of uterus during childbirth and release milk

Negative Feedback • Homeostasis is often maintained by two hormones who have antagonistic effects – Each hormone does the opposite of the other. • For example, if the blood pressure drops too low, the pituitary releases ADH, which causes the kidneys to reabsorb more water. If it the blood pressure increases too much, then the heart will release ANH, which will cause the kidneys to reabsorb less water.

Positive Feedback Mechanisms

• Positive Feedback mechanisms control events that can be out of control and do not require continuous adjustment • Rarely used to maintain homeostasis • Example of positive feedback found in childbirth – Oxytocin stimulates and enhances labor contractions – As labor continues, more oxytocin is produced – Intensifies contractions until the baby is outside birth canal – Oxytocin production stops and labor contractions stop

The one responsible for secreting hormones

Endocrine System

A chemical messenger which targets a specific group of cells, in order to cause that group of cells do some activity or stop doing an activity

Hormones

Each hormone acts on a certain kind of tissue called _____________

Target tissues/Target cells

Pituitary gland is a round organ about the size of a pea that secretes 9 hormones, located behind the bridge of the nose at the base of the brain

Pituitary Gland

Pituitary gland is a round organ about the size of a pea that secretes 9 hormones, located behind the bridge of the nose at the base of the brain

Pituitary Gland

Two parts of Pituitary Gland

Anterior Lobe and Posterior Lobe

Called as Master Gland

Anterior Lobe

Control the secretion of the pituitary gland

Hypothalamus

Process wherein the testosterone stimulates the maturity of the male reproductive system

SPERMATOGENESIS

Process wherein the estrogen stimulates the maturity of the female reproductive system

OOGENESIS

Oversecretion of Growth Hormone will result int0 ________

Giantism

Undersecretion of Growth Hormone will result int0 ________

Dwarfism

The process of controlling and balancing the release of hormones in the body Homeotasis

Why is Feedback Important? Without feedback, homeostasis cannot occur. This means that an organism loses the ability to self-regulate its body