The Glands and Hormones of the Endocrine System Endocrine System Regulation of Body Temperature Regulation of Body’s H 2 O Content Regulation of Serum.

The Glands and Hormones of the Endocrine System

Endocrine System

Regulation of Body Temperature

Regulation of Body’s H2O

Content

Regulation of Serum Glucose

Levels

Regulation Ca++

MetabolismRegulation of

Rate of Metabolism

Hormones steroids

peptides(proteins)

prostaglandins

catecholamines

“little ones”

“big ones”

“really big ones”

anteriorpituitary

hypothalamus

posterior pituitary

somatostatin

uterus

breast

kidney

adrenal cortex

adrenal medulla

liver

beta cellsin pancreas

alpha cellsin pancreasbody cells

& musclesblood

ovaries

testes

gut

bones

parathyroid

thyroid

oxytocin

prolactin

oxytocin

ADHHGH (somatotropin)

FSH & LH

FSH & LH

TSH

ACTH

T3 &

T4

calcitonin

PTH

catecholamines

peptides

protein

insulin

glucacon

epinephrine & norepinephrine

epinephrine & norepinephrine

steroids

glucocorticoids

aldosterone

estrogen

testosterone

estrogen & progesterone

glycoproteins

Hormone Interactions in the Human Body

Main Function:it secretes hormones (chemical messengers) into the blood to signal other cells to behave in certain ways. it is a slower form of communication compared to the nervous system, but it has longer lasting effects.

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Endocrine glands secrete hormones into the bloodstream.pituitary, pineal, thyroid, parathyroid, and adrenal glands are solely endocrine glandshypothalamus, thymus, pancreas, testes, and ovaries have other functions

Hormones:over 200 different ones

Consists of:

• The word “hormone” comes from the Greek meaning “to excite or to set into motion”

• There are two types:o Steroid hormones: lipid-soluble molecules made form

cholesterol (e.g. male and female sex hormones, cortisol)

o Water-soluble hormones: derived from amino acids or chains of amino acids (e.g. insulin, growth hormone, thyroxine)

Delivery Systems

• autocrine system – chemicals made by a cell to affect itself

• paracrine system – chemicals made to affect cells nearby

• juxtacrine system – chemicals made to signal along a cell membrane (own cell or neighbouring cells)

Hormone Action on Target CellsHow do they know where to go?

– Target cells have protein receptors for hormones

Steroid Hormones• Steroid hormones are lipids

(and hydrophobic)– Made from cholesterol

– Not soluble in water1. diffuse through the lipid bilayer of the

membranes of the target cells

2. Diffuse into target cells & bind to receptors

3. Often moves into nucleus to affect transcription

This binding activates specific genes, causing changes in the cells such as cell growth.

Steroid Hormone Action

Steroid Hormone Action

R

RH

H

Steroid Hormone ActionSteroid Hormone Action

binding area

RH

RH

Protein Hormones• Short peptide sequences

• Water soluble

• 1. transported from cell of origin (secretory vacuoles)

• 2. attach to surface receptors of target cells

• 3. activates enzymes to make other internal signals – cascade of reactions (amplifies)

protein hormone action

Protein Hormone ActionProtein Hormone Action

R

H

ATP

cyclic AMP + PPi

other enzymes

The Hypothalamus

The Hypothalamus

• located in the brain, this region controls most endocrine secretions

• link between the nervous system and the endocrine system

• mainly regulatory hormones are produced here

• most control the pituitary gland

PITUITARY GLAND

• This is known as the master gland because it controls a lot of other endocrine glands.

• A small sac connected to the hypothalamus.

• Pituitary gland stores hormones while the hypothalamus stimulates it to release them.

PITUITARY GLAND

• The pituitary gland has two lobes:

– The posterior lobe stores and releases hormones produced by the hypothalamus (ex. ADH, oxytocin)

– The anterior lobe produces and stores its own hormones (ex. TSH, prolactin)

Regulating the Regulators

After receiving signals from sensors in the body, the hypothalamus secretes releasing hormones. These hormones stimulate the pituitary gland to secrete other hormones that act on other endocrine glands. Hormones that target endocrine glands to secrete other hormones are called tropic hormones.

Continued…

Regulating the RegulatorsA specific example of hormone regulation is the negative feedback system that controls thyroid-stimulating hormone (TSH), shown in diagram A, below.

Working TogetherThe nervous system and the endocrine system work together to maintain homeostasis. The functions of these two systems often overlap:

• some nervous system structures (such as cells in the hypothalamus) release hormones

• some chemicals (epinephrine) act as both neurotransmitters and hormones

• both the endocrine and nervous systems are regulated by feedback loops

• some physiological processes require both systems to operate (e.g., breastfeeding a baby involves nerve messages and the hormone oxytocin)