lionden.com
Contact
Dr. Patton

  

L  e  a  r  n  i  n  g       O  u  t  l  i  n  e

    Back
Search
Lion Den
Up 
Related Links

Endocrine System

Lion Tracks

Lion Den -> Anatomy & Physiology -> Course Info -> A&P 1 -> A&P 1 Outlines -> ENDOCRINE

Reading assignment: 
Chapter 16
(Thibodeau & Patton Anatomy & Physiology)

Need help?

Press the
Panic Button

Key to Hyperlink Symbols

ACT  Interactive
 activity
GA  Gray's Anatomy
ANIM  Animation pp  PowerPoint slide
FIG  Figure term

Define,  pronounce

       

Online preview:
Endocrine System
(Parts 1 & 2)

(Previews are found at WebCT)

Note: you must know the names and sources of all hormones listed in tables of Chapter 16 (except the hypothalamic releasing hormones).  

In class, we will focus mainly on the theories of how this system works.  The details of individual glands and their hormones will be learned mostly on your own.

Hormones

bullet

Chemical messengers released into the blood and having an effect outside the tissue that made it

bullet

Source: endocrine (ductless) glands
bullet

"Regular" endocrine tissue - glandular epithelium

bullet

Neurosecretory tissue - modified neurons

bullet

Target concept    pp
bullet

Target cells, target tissues, target organs

bullet

Receptors (specific to a particular hormone)

bullet

Signal transduction

bullet

Pathway
bullet

Gland --> Blood --> Target tissue (receptor)

bullet

Two categories     pp
bullet

Steroid - lipids derived from cholesterol

bullet

Nonsteroid
bullet

Protein

bullet

Glycoprotein

bullet

Peptide

bullet

Amine (derived from amino acids)

Prostaglandins (PG)

bullet

Lipids (fatty acids)

bullet

Have LOCAL effects, but are regulatory chemicals carried in the blood, so they are sometimes called "tissue hormones"
bullet

Paracrine agents or "hormones"
bullet

Substances that regulate other cells in the same tissue

bullet

Autocrine agents or "hormones"
bullet

Substances that regulate the same cell that produced it

bullet

Endocrine hormone
bullet

Substances that regulate cells outside the tissue that produced it

bullet

Classical definition of hormone (one that we'll use in our course)

Mechanisms of hormone actions
bullet

Steroid hormones
bullet

Lipid hormones derived from cholesterol
bullet

Examples: testosterone, estrogens (e.g., estradiol), progesterone, aldosterone, cortisone

bullet

Mobile receptor model (nuclear receptor model)
bullet

Steroid hormone travels in blood plasma (hormone is temporarily bound to a plasma protein)

bullet

Hormone dissolves through phospholipid bilayer of plasma membrane of target cell

bullet

Hormone binds to receptor inside cell (probably in nucleus), forming hormone-receptor complex

bullet

Hormone-receptor complex triggers the activation of a particular gene (on nuclear DNA)

bullet

mRNA is transcribed at the activated gene

bullet

protein is made using the gene encoded in the new mRNA

bullet

protein causes the hormonal effect

bullet

Nonsteroid hormones (peptides, proteins)
bullet

Membrane-bound receptors (face out of the target cell)    pp
bullet

May move into cell if small enough

bullet

Second messenger systems
bullet

cyclic AMP
bullet

hormone travels in blood plasma

bullet

Hormone binds to its receptor in the plasma membrane

bullet

Hormone-receptor binding activates a G protein (in plasma membrane)

bullet

Activated G protein in turn activates the enzyme adenyl cyclase

bullet

Adenyl cyclase causes ATP to lose two P, becoming cAMP (cyclic AMP [adenosine monophosphate])

bullet

cAMP activates protein kinases (enzymes that activate other proteins/enzymes), producing the hormonal effect

bullet

Ca++-calmodulin
bullet

hormone travels in blood plasma

bullet

hormone binds to its specific receptor in the plasma membrane

bullet

hormone-receptor binding activates G protein, then adenyl cyclase, then protein kinases

bullet

activated protein kinase opens Ca++ channels in plasma membrane

bullet

Ca++ diffuses into target cells (remember, cells HATE calcium, so all the Ca++ was outside the cell to begin with)

bullet

Ca++ binds to calmodulin inside cell

bullet

Ca++-calmodulin complex activates (or inactivates) an enzyme, producing the hormonal effects

bullet

Many drugs are targeted at G-protein-coupled receptors (GPCRs)—about 25% of the top-selling drugs and more than half of all currently used drugs.

bullet

Amino acid derivative hormones, such as thyroid hormone, may have intracellular receptors as do steroid hormones

bullet

Hormones may work together to regulate target cells     pp
bullet

Synergistic effects: combined effect is  greater than sum of individual effects

bullet

Permissive effects: one hormone allows another hormone to have its full effect

bullet

Agonistic effects: two hormones have similar effects

bullet

Antagonistic effects: two hormones have opposing effects

bullet

Trop(h)ic effects: hormones stimulate development of another gland and secretion of that gland's hormones

bullet

Hormones have diverse functions

bullet

Even though our course focuses on one or two main actions for each hormone, each hormone may have hundreds of secondary effects

bullet

Important for understanding the complexity of endocrine function

bullet

Not all hormones find their targets    pp

bullet

Metabolized or excreted

bullet

Clinically useful:  blood or urine analysis shows hormone levels

Regulation of receptors
bullet

Up regulation
bullet

Target cells increase their number of a particular hormone receptor, becoming more sensitive to that hormone

bullet

Down regulation
bullet

Target cells decrease their number of a particular hormone receptor, becoming less sensitive to that hormone

bullet

Receptor turnover
bullet

Ongoing process of a cell moving receptors to its plasma membrane or nucleus and removing other receptors, all occurring at rates that can be increased or decreased under different conditions

Regulation of secretion
bullet

Basal secretion (may be periodic)
bullet

Increase or decrease via  feedback controlling mechanisms

bullet

Feedback
bullet

Negative; positive

bullet

Long loop; short loop

bullet

Responsive

Endocrine disorders     pp

Many endocrine disorders have historically been classified as:

bullet

hypersecretion disorders: where there is too much of one or more hormones being secreted

bullet

hyposecretion disorders: where there is not enough of one or more hormones being secreted

However, we now know that such classifications can be misleading because some disorders that appear to result from hypersecretion may instead be caused by increased sensitivity due to abnormal up regulation or changes in the signal transduction mechanism.  

Likewise, the appearance of hyposecretion may instead be caused by abnormal down regulation of receptors or by problems in signal transduction in the target cells.

Hypothalamus-pituitary

bullet

Neuroendocrine cells are neurons that release their transmitters directly into the blood (rather than across a gap to another neuron), so the transmitters then act as hormones

bullet

Hypothalamus
bullet

Part of brain on inferior side, just in front of (and above) the brain stem

bullet

Part of it is nervous tissue, part is neuroendocrine tissue

bullet

Pituitary (hypophysis)    GA
bullet

Divided into two parts: Anterior Pituitary and Posterior Pituitary    GA
bullet

Anterior pituitary (adenohypophysis)
bullet

"regular" endocrine tissue

bullet

Releasing (release-inhibiting hormones) from the hypothalamus regulate anterior pituitary secretion
bullet

Hypophyseal portal system

bullet

Major hormones
bullet

Pr (prolactin)

bullet

GH (growth hormone)

bullet

Tropic hormones (trigger development of/secretion by other glands)
bullet

ACTH (adrenocorticotropic hormone)

bullet

TSH (thyroid-stimulating hormone)

bullet

 LH (luteinizing hormone)

bullet

 FSH (follicle-stimulating hormone)

bullet

Posterior pituitary (neurohypophysis)
bullet

Neuroendocrine cells
bullet

Body of cell is in hypothalamus

bullet

Fiber extends from each neuron cell body down into posterior pituitary

bullet

Thus, posterior pituitary hormones are made in the hypothalamus but released from the posterior pituitary

bullet

Oxytocin and ADH (antidiuretic hormone)

Thyroid

bullet

Location - below larynx, wrapped around trachea    GA

bullet

Structure
bullet

Two lateral masses and isthmus

bullet

Follicles    GA
bullet

Follicular cells - release thyroid hormone

bullet

Thyroid colloid - store thyroid hormone

bullet

Thyroid hormone
bullet

T3 - triiodothyronine

bullet

T4 - tetraiodothyronine

bullet

Parafollicular cells
bullet

Calcitonin

Parathyroid

bullet

Location    GA
bullet

Imbedded in posterior surfaces of thyroid

bullet

Structure 
bullet

4-5 small round bodies made of glandular epithelium

bullet

Hormone: parathyroid hormone (PTH)

Adrenal (suprarenal)

bullet

Location     GA   GA  GA
bullet

On top of each kidney (renal = "kidney")

bullet

Structure    GA
bullet

Cortex (endocrine)
bullet

zona glomerulosa
bullet

mineralocorticoids (aldosterone)

bullet

zona fasciculata
bullet

glucocorticoids (cortisone)

bullet

zona reticularis
bullet

glucocorticoids (cortisone)

bullet

gonadocorticoids (testosterone, estrogens)

bullet

Medulla (neurosecretory)
bullet

catecholamines (epinephrine[adrenaline])

Pancreas

bullet

Location    GA  GA
bullet

Lies within the C of the duodenum, inferior to the stomach

bullet

Structure
bullet

Pancreatic islets (of Langerhans) (endocrine)
bullet

Alpha cells (A) - glucagon

bullet

Beta cells (B) - insulin

bullet

Delta cells (D) - somatostatin

bullet

PP cells (F) - pancreatic polypeptide

bullet

Acinar cells (exocrine)

Other endocrine glands

bullet

Ovaries
bullet

Estrogens and progesterone

bullet

Testis
bullet

Testosterone

bullet

Placenta
bullet

Human chorionic gonadotropin (HCG)

bullet

Estrogens

bullet

Progesterone

bullet

Placental lactogen

bullet

Thymus    GA
bullet

Thymosin

bullet

GI (gastrointestinal) mucosa
bullet

Several hormones regulate GI function

bullet

Heart
bullet

Atrial natriuretic hormone (ANH)

bullet

Pineal
bullet

Melatonin

Please refer to Table 16-10 in Anatomy and Physiology for a summary of these and other additional hormones of the human body.

Example of homeostatic endocrine regulation