The Endocrine System

The Third Date ;)

DON’T FREAK OUT

What do we know that we need to know?

• types and location of endocrine glands including pituitary, thyroid, parathyroid, pancreas, adrenal glands, gonads

• relationship between the hypothalamus and pituitary

• production site, target organ and effect of hormones associated with the specified glands

• feedback loops involving endocrine activity • hormonal modes of action.

Types Glands in the Body

• Exocrine glands secrete into a duct that carries the secretion to the body surface or to one of the body cavities. Sweat glands, mucous glands, salivary glands and the glands of the alimentary canal are examples of exocrine glands.

• Endocrine glands secrete hormones into the extracellular fluid that surrounds the cells making up the gland. The secretion then usually passes into the capillaries to be transported by the blood. Endocrine glands are sometimes called ductless glands.

Location of endocrine glands

Pituitary and Hypothalamus sitting in the tree….

Hypothalamus- base of brainPituitary- just under Hypothalamus

Joined by the

INFUNDIBULUM

Pituitary/ Hypothalamus Communication

• The hypothalamus produces many different hormones.

• Some of them are carried by the blood to the anterior lobe of the pituitary where they stimulate or inhibit the release of hormones made in the anterior lobe.

• Other hormones pass along the nerve fibres from the hypothalamus to the posterior lobe of the pituitary where they are then secreted.

Structure of Pituitary

ANTERIOR- glandular tissue

POSTERIOR- nervous tissue

Anterior Pituitary

• Hormone secretion regulated by releasing and inhibiting factors from hypothalamus

• FSH• LH• GH• TSH• ACTH• Prolactin

ROAD BLOCK

• CREATE AN ANAGRAM TO HELP YOU REMEMBER THE ANTERIOR HORMONES!!

• Eg. A Fishing Line Gets Thrown After Pinkies

• Or A Good Friend Lets People Talk After

• Or just learn one of these

FSH

• Female- acts on ovaries to stimulate the follicle that contains the egg

• Male- stimulates production and maturation of sperm in the testes

LH

• Female- Works with FSH to bring about ovulation and form corpus luteum. (ovaries and uterus)

• Male- LH stimulates interstitial cells in the testes to secrete male sex hormones

GH

• Stimulates body growth particularly growth of the skeleton.

• It increases the rate at which amino acids are taken up by cells and built into proteins.

• GH is secreted throughout life as it helps to maintain the size of organs once maturity is reached

TSH

• Stimulates production and release of hormones from the thyroid gland

ACTH

• controls production and release of some of the hormones from the cortex of the adrenal gland

Prolactin

• works with other hormones to initiate and maintain milk secretion in females (mammary glands)

POSTERIOR PITUITARY• releases the hormones oxytocin and antidiuretic hormone• neither is manufactured in the posterior lobe. Both

hormones are produced in special nerve cells in the hypothalamus of the brain.

• These cells have long extensions that pass through the infundibulum to the posterior lobe.

• Hormones manufactured in the cells move down the extensions and are stored ready for release into the bloodstream. The release of the hormones is triggered by nerve impulses initiated in the hypothalamus and conducted along the cell extensions

OXYTOXIN

• Stimulates contraction of the muscles of the uterus. It

• Is released in large quantities during labour.• Oxytocin also stimulates contraction of cells in

the mammary glands, resulting in release of milk during breastfeeding

ADH

• causes the kidneys to remove water from urine that is forming. This water is returned to the bloodstream.

• In this way, ADH helps to retain fluid within the body.

• At higher concentrations, ADH can also cause constriction of small arteries, the arterioles.

THYROID

THYROID

• Thyroxine• controls body metabolism by regulating reactions in

which complex molecules are broken down to release energy and in which complex molecules are synthesised from simple ones.

• The overall effect of thyroxine is to bring about the release of energy and, since some of the energy released is in the form of heat, to maintain body temperature.

• Thyroxine is secreted in response to thyroid stimulating hormone from the anterior lobe of the pituitary.