BIOA 2006 - Lecture 11: Endocrinology

Secretory glands of the endocrine system

Adrenal medulla, adrenal cortex, pineal gland

hypothalamus, anterior pituitary, posterior pituitary

parathyroid gland, thyroid gland, pancreas

Long distance hormones travel through the

blood stream

Local hormones travel through the

interstitial fluid

the pancreas has both

endocrine and exocrine cells

Communication between cells in the body occurs by means of these two systems

nervous (quick) and endocrine (slow, like digestion, growth, development, and reproduction) systems

Cells will only be affected by the hormones if they have

receptors that recognize the hormone

Hormones are

chemical messengers that regulate the activity of target cells

Target cells have

receptors for specific hormones

Endocrine cells release hormones into

interstitial fluid then into blood

exocrine cells release secretions via

a duct to the epithelial surface

Neurohormones are produced by

neurons in hypothalamus called neuroendocrine cells

Endocrinology definition

the study of internal secretions and of the hormonal controls of bodily function

Paracrine (endocrine) glands

glands that secrete chemicals that diffuse through the interstitium to affect other cells in a very localized fashion.

ex: leydig cells of the testes secrete testosterone to the seminiferous tubules for spermatozoa development

The "traditional" endocrine glands are

pituitary

thyroid

parathyroid

adrenal gland

pancreas

gonads (ovary or testes)

Classic hormones are those that communicate

over long distance

autocrine glands

secrete substances that act on themselves

-ex: immune cells that secrete chemicals called interleukins, which in turn affect that cells function

Classical vs Local hormones reach target cells by

Local: diffusion through interstitial fluid

Classic: long distance, blood

What is the difference between neurohormones and neurotransmitters

NTs act locally and quickly at a synapse while neurohormones travel long distances to make a longer term impact travelling through the blood

Endocrine, paracrine, autocrine, neural, and neuroendocrine regulation diagrams

What do hormones regulate?

-energy and metabolism

-electrolyte and fluid balance

-growth and devel

-reproduction

-digestion

-immune functions

-biological rhythm

Hormones circulate at ______ levels in the blood

low

though all cells are exposed to hormones, which can respond?

those with receptors

generally, the greater amount of hormone, the

greater the response

classical hormone example

insulin

neurohormone ecample

oxytocin

local hormone example

prostaglandins (paracrine/autocrine)

Tropic hormones are those which

regulate the secretion of other hormones (eg., thyroid stimulating hormone) as well as the growth of the target endocrine gland (eg., thyroid stimulating hormone supports growth of the thyroid gland)

Thymosin

stimulates the maturation of lymphocytes into T cells of the immune system

Neuroendocrine regulation

neurohormones are released from nerve endings of neuroendocrine cell and transported as classical hormone in the blood stream to the target cells