Download Hormones of the Anterior Pituitary Gland

Chapter 9: Endocrine System
The #1 Function of the Endocrine System is:
- The communication and control of the body but providing a slower &
longer lasting signal using hormones (chemicals secreted into & circulated
by the blood)
Endocrine Vs Nervous
 Hormones travel to every point in the body – neurotransmitters travel
short distances over synapse
 Endocrine can regulate most body cells – nervous system can only control
organs innervated w/ efferent fibers
 Hormones appear slowly & last longer – neurotransmitters are rapid &
short-lived
Organs of the Endocrine System are all glands – but not all glands are in the
Endocrine System (ex. lacrimal glands, sebaceous glands, sudoriferous
glands)
- endocrine glands can be made of glandular epithelium or neurosecretory
tissue (modified neurons)
Review!
- Endocrine gland – ductless gland that secretes in
- Exocrine gland – secretes out to the surface – ex.) sweat gland
Some Hormone Classifications:
- tropic hormones – those that target other endocrine glands & stimulate their
growth & secretion
- sex hormones – those that target reproductive tissues
- anabolic hormones – those that stimulate anabolism in their target cells
2 Chemical Structures of Hormones
1.)
Nonsteroid Hormones –
a.)
Proteins – consists of:
insulin
growth hormone
calcitonin
prolactin
adrenocorticotropic hormone
parathyroid hormone
glucagon
b.)
c.)
d.)
Glycoproteins – consists of:
follicle-stimulating hormone
luteinizing hormone, thyroidstimulating hormone
chorionic gonadotropin
Peptides – consists of :
antidiuretic hormone
oxytocin
melanocyte-stimulating hormone
somatostatin
thyrotropin-releasing hormone atrial natriuretic hormone
gonadotropin-releasing hormone
Amino acid derivatives – consists of:
1.)
Amines – norepinephrine, epinephrine, melatonin
2.)
Iodinated amino acids – thyroxine, triiodothyronine
2.) Steroid Hormones – made from cholesterol (4 interconnected rings)
- they are lipid soluble & can pass directly through the cell membrane of a
target organs cell
- ex.) cortisol, aldosterone, estrogen, progesterone, testosterone
How Do Hormones Work?
- hormones bind to specific receptors on or in a cell (target cell)
- cells usually have many different receptors types so they can be acted upon by
different hormones
- hormones are the main regulators of metabolism, growth &
development, reproduction, etc. - they also maintain homeostasis
-
if hormones work together – synergism
if small amount of 1 hormone allows a 2nd to have full effect – permissiveness
when 1 hormone produces the opposite effect of another - antagonism
Steroid Hormone Action – Mobile-Receptor Hypothesis
- lipid so they are not very soluble in blood plasma – attach to soluble plasma proteins
- can pass into cells so most have receptors on the cell’s inside
- once inside they combine with specific receptors & enter the nucleus to influence
cell activity by acting on specific genes
Nonsteroid Hormone Action – 2nd Messenger Hypothesis or Fixed-Membrane-Receptor
Hypothesis
- in this hypothesis:
a.) protein hormones serve as 1st messengers providing communication
between endocrine glands & target organs
b.) another molecule acts as a 2nd messenger providing
communication within a hormone’s target cell
Regulation of Hormone Secretion
- regulation of the secretion of hormones depends on negative feedback –
secretion continues until a point is reached & the system is shut off
- positive feedback is a mechanism that amplifies the change from the
hormone instead of reversing the change
- positive feedback is most of the time very harmful leading to death,
however, it can be helpful especially in labor contractions
The Major Endocrine Organs:
1.)
Pituitary Gland – about the size of a grape & lies deep in the cranial cavity
surrounded by the sphenoid bone – is really 2 endocrine glands
A.)
anterior pituitary gland – or adenohypophysis – has the structure of
endocrine glands
B.)
posterior pituitary gland – or neurohypophysis – has the structure of
nervous tissue
Hormones of the Anterior Pituitary Gland
1.)
thyroid stimulating hormone (TSH)
2.)
adrenocorticotrophic hormone – (ACTH)
3.)
follicle stimulating hormone – (FSH)
4.)
lutenizing hormones – (LH) –
in males –also referred to as interstitial cell-stimulating hormone
(ICSH) - hyposecretion of FSH & LH leads to sterility in both males &
females
5.)
melanocyte stimulating hormone – (MSH)
6.)
growth hormone – (GH)
- increase blood glucose levels – this increase is called hyperglycemia
- hypersecretion during childhood results in gigantism (body
proportions are fairly normal), if during adulthood results in
acromegaly (change in facial features, hands & feet) – most
hypersecretion cases are due to pituitary gland tumors
- hyposecretion during childhood results in pituitary dwarfism (body
proportions are fairly normal just miniaturized)
7.)
prolactin (lactogenic) hormone – function in males is not known
Hormones of the Posterior Pituitary Gland
1.)
antidiuretic hormone – (ADH)
2.)
oxytocin
***Amazing fact of the Posterior Pituitary Gland (PPG) is
that the 2 hormones released are produced in the hypothalamus – so
technically the PPG is not an endocrine gland because it does not produce
the hormones
- release of hormones is controlled by nervous stimulation
Major Endocrine Organs cont..
2.) Pineal Gland – small, cone-shaped gland found in the roof of the
3rd ventricle of the brain – secretes a number of hormones in small quantities –
only one to show a significant amount is Melatonin – its levels rise & fall over the
course of the day – believed to establish our internal clock & inhibit ovarian
activity during childhood
- abnormal secretion causes winter depression – exposure to
sunlight is low & melatonin levels are high
3.) Thyroid Gland – lies in the neck just below the larynx (voice
box) – consists of 2 lobes – secretes:
A.) Thyroid Hormone – is actually 2 active hormones:
1.) Thyroxine – (T4) – contains 4 iodine atoms – more
important & more abundant
2.) Triiodothyronine – (T3) – contains 3 iodine atoms
- Problems that can occur:
a.) Simple Goiter – painless enlargement of the
thyroid gland as a result of low intake of iodine causing a
hyposecretion of thyroxine
b.) Cretinism – hyposecretion of thyroxine in the
formative years – results in dwarfism where the adult body
parts remain childlike – if untreated will result in mental
retardation
c.) Myxedema – hyposecretion of thyroxine in the
adult years – have mental & physical sluggishness, puffiness in the
face, fatigue, poor muscle tone, low body temperature, obesity &
dry skin
d.) Hyperthyroidism – generally results from a tumor
in the thyroid gland – there is an oversecretion of thyroid
hormone that will increase the metabolic rate so food is
burned at an excessive rate – symptoms include a loss of
weight, increased appetite, nervous irritability, protruding
eyes (condition called exophthalmos) – one form of
hyperthyroidism is Graves’ Disease
e.)
Hashimoto disease – autoimmune damage to thyroid causing
hyperthyroidism
B.) Calcitonin –or thyrocalcitonin – acts as an antagonists to
the parathyroid gland to maintain homeostasis
- few problems are known but calcitonin production does cease in the
elderly
4.) Parathyroid Gland – small gland, usually 4 of them found on
the back of the thyroid gland
- secrete parathyroid gland hormone (or parahormone) – (PTH)
- problems that occur result in a life & death situation – too little causes
uncontrollable spasms that lead to death – too much cause fragile
bones
5.) Hypothalamus - adjusts the secretions of the anterior pit. Gland
through (-) feedback – secretes:
A.)
Growth hormone-releasing hormone - GRH
B.)
Growth hormone-inhibiting hormone – GIH – somatostatin
C.)
Corticotropin- releasing hormone – CRH
D.)
Thyrotopin- releasing hormone – TRH
E.)
Gonadotropin- releasing hormone – GNRH
F.)
Prolactin- releasing hormone – PRH
G.)
Prolactin-inhibiting hormone – PIH
6.) Adrenal Gland – curves over the top of each kidney – is 2 organs
that function as one – they are:
A.)
Adrenal Cortex – outer part of gland – its secreted hormones are called
corticoids & the adrenal cortex has 3 layers:
1.)
Zona glomerulosa – outer zone - secretes mineralocorticoids (MCs)
- the main hormone of this group is aldosterone
B.)
2.)
Zona fasciculata – middle zone – secretes glucocorticoids (GCs)
- main hormone of this group is cortisol or cortisone
3.)
Zona reticularis – inner zone – secretes sex hormones – in males
androgens are produced that are weak
because of the testosterone produced by the testes
- in females some estrogens are produced & this helps stimulate
the sex drive
Adrenal Medulla – inner part of the adrenal glands
- secretes epinephrine (adrenaline) & norepinephrine (noradrenaline) –
they belong to a group called catecholamines because the nervous
system also releases norepinephrines as a neurotransmitter
- these are fast acting stress responses
- these hormones are essential for maintaining life
- in a threatening situation – the nervous system brings about the “fight or
flight” response – the adrenal medulla is stimulated & adrenaline is
secreted – the heart will beat faster, increase in blood pressure, more
blood to muscle, more glucose from the GCs for more energy
- prolonged stress causes the GCs to “burn out” - death
Problems with the Adrenal Glands: usually caused by tumors
1.)
Addison’s Disease – hyposecretion of the zona reticularis – symptoms are:
bronze tone of the skin, electrolyte & H2O balance is off, muscle become weak,
hypoglycemia, burnout, susceptible to infections
2.)
Aldosteronism – hypersecretion of aldosterone – Na+ retention & K+ loss
3.)
Hypersecretion of sex hormones – leads to male secondary sex characteristics –
apparent in females, hidden in males
4.)
Cushing’s Syndrome: hypersecretion of the zona fasciculata – symptoms are:
“moon face”, “buffalo hump” of fat on upper back, high blood pressure,
hyperglycemia, diabetes, weak bones, immune system suppression
Major Endocrine Organs cont…
7.) Pancreatic Islets – located within the pancreas (found close to
the stomach in the abdominal cavity) – also known as the islets of Langerhans –
the hormone-producing tissue is scattered among the pancreatic cells they
secrete pancreatic digestive juices (exocrine system) - produces 2 important
hormones:
a.)
Glucagon – secreted by the alpha cells of the islets – it is
stimulated by low blood levels of glucose – will target the liver to
breakdown stored glycogen to glucose (glycogenesis) which increases blood
glucose concentration – no known disorders from hypo- or hypersecretion
b.)
Insulin – secreted by the beta cells if the islets – acts on
almost all body cells & helps the transport of glucose across their cell
membranes – is stimulated by high blood levels of glucose - is the only
hormone that decreases blood glucose levels
- disorders:
1.) without it glucose could not be used by cells
2.) diabetes mellitus – too much glucose in the blood
spills into the urine causing dehydration – weight
loss, infections, excessive urination, excessive
thirst, & hunger – without treatment leads to a
coma & then death
c.)
d.)
Somatostatin – produced by the delta cells of the islets
Pancreatic polypeptide - produced by the pancreatic polypeptide cells or F
cells – influences digestion
8.) Thymus – located in the upper thorax, posterior to the sternum –
composed mostly of connective tissue & fat – large in infants & children, size
decreases in adulthood – produces:
a.)
Thymosine
b.)
Thymopoietin
***Both play a role in the dvlpt & function of the body’s immune system
9.) Gonads – produce sex hormones that are identical to those
produced by the adrenal cortex – difference is the source & amounts – don’t
function until puberty - 2 types:
a.)
female gonads – ovaries – stimulated by the anterior pituitary gland - 2
groups of steroid hormones:
1.)
Estrogens – mainly Estrone & Estradiol – produced by the ovarian
(Graafian) follicles
2.)
Progesterone – produced by the corpus luteum (which also secretes
a small amount of estrogen)
- disorders – from hyposecretion – infertility
- decrease in later years - menopause
b.)
male gonads – testes – also stimulated by the APG – hormone is Androgens
– mainly Testosterone – produced by the interstitial cells of testes
- disorders – from hyposecretion – sterility
10.) Placenta – temporary Endocrine Gland – produces hormones
that maintain pregnancy – secretes:
a.)
Estrogen
ovaries become inactive during
b.)
Progesterone
pregnancy
c.)
Human Chorionic Gonadotropins (hCG) – what a pregnancy test picks up
d.)
Human Placenta Lactogen – prepares breast for lactation
e.)
Relaxin – relaxes pelvic ligaments for birth
11.) Stomach & Intestinal Mucosa – produces:
a.)
Gastrin
b.) Secretin
c.) Cholecystokinin
d.) Ghrelin
12.) Kidneys – erythropoietin, active vitamin D3
13.) Heart – atrial wall secretes atrial natriuretic hormone (ANH) that stimulates Na+
loss from kidneys