Download The Endocrine Syetem

The Endocrine System
Chapter 9
Communication and Control – slower and long
lasting through hormones – chemical messages –
that effect a target organ
 Diseases (tumors) influence by:

Hyposecretion – too little secretion
 Hypersecretion –two much secretion


All organs are glands:
Exocrine – secrete products into ducts
 Endocrine – ductless glands
 Heterocrine Gland - Both (pancreas)

Origin Of Hormones
 Hormones
affects target cells
 Secreted by endocrine glands
 Secreted by neurons (neuro-hormones) neurosecretory cells
 Secreted by individual cells or tissues (Growth
Factors, prostaglandins, histamine)
Chemical Nature of Hormones
 Derived
from
cholesterol
 Derived from amino
acids
 Derived from fatty
acids
Protein Hormones





Second Messenger Hypotheses
Cause specific affects on target
organs only
Hormone binds to specialized
receptor – “first messenger”
Second Messenger is Cyclic
Adenosine MonoPhosphate
(cAMP)
The bonding of the hormone
activates activates a G4
protein, which in turn activates
adenylate cyclase (enzyme) to
react with ATP to produce
cAMP
Steroid Hormones
Small – lipid soluble
Hormones
 Pass directly through the
cell membrane of target
organs
 Go to nucleus, interact
with DNA to allow
transcription of certain
proteins

Prostaglandins
 PG’s
- tissue hormone – produced on a tissue and
acts on nearby cells
 Three groups PGA, PGE, PGF
 Might have a role in asthma, blood pressure
disorders, and ulcers
Negative Feedback
 Reverses
a change in a body condition
 Insulin – high blood-sugar content after a meal,
pancreas secretes insulin to move blood-sugar into
cells, thus decreasing levels
Other types of Negative Feedback
Positive Feedback
 More
Uncommon than negative feedback
 Amplify changes rather than reverse them
 Labor – the contractions are amplified through
hormone control
Pituitary Gland
 Gland
in hind brain about the size of a pea
 Anterior (adrenohypophysis)- gland / Posterior
(neurohypophysis) - nervous
Anterior (adrenohypophysis)- gland - hypothalamin releasing
hormones get anterior to release hormones
Posterior (neurohypophysis) - nervous - nerve endings from
hypothalamus cause hormones to be released
Hormones of Anterior Pituitary

Tropic Hormones – Stimulates another endocrine gland to grow and
secrete its hormone
ANTERIOR GLAND - TROPIC
 TSH
- (thyroid-stimulating) Growth and secretion of
the thyroid
 ACTH - (adenocorticotropic) Growth of Adrenal
cortex and secretions
 FSH - (follicle stimulating) Growth and
development of Ovarian Follicles - providers of ova
(eggs), release of estrogen/progesterone
 LH - (Luteinizing) Control ovulation - maturation
and bursting of follicle - males - interstitial cells
 ICSH - (Interstitial cell)Testosterone secretion of
testes


MSH - (melanin stimulating hormone) - synthesizes and spreads
melanin - pigment
GH - (Growth Hormone) -stimulates growth by protein anabolism
(building) - fat and glucose catabolism - enhances the movement of
Amino acids across cell membrane



Insufficient GH - dwarfism
Oversecretion - giagntism
Prolactin - (lactogenic) - stimulates milk production, in males excess
may decrease sex hormones
Posterior Pituitary Hormones
 ADH-
retention of water by kidneys (diuretic - loss
of water by kidneys)- maintained by
osmoreceptors in the brain
 Oxytocin - stimulates uterine contraction - positive
feedback
Thyroid Gland ---Parathyroid Gland




Located in the neck, below the
larynx
Thyroxin (T4 - four atoms of
iodine - accelerates metabolism
Calcitonin - decreases blood
calcium, puts calcium into
bones
Triiodothyronine (T3 three
atoms of iodine) -energy for
metabolism - five times as
potent as thyroxin
Small (usually 4) found on
the back of the thyroid
 Increases Blood Calcium breaks down bone

Adrenal Glands
 Adrenal
 Two
Glands - Lie on top of the kidneys
separate endocrine glands the adrenal cortex and
the adrenal medulla
ADRENAL GLANDS
CORTEX
 Glucocorticoids - maintain
blood pressure, sugar,
stress - cortisol
 Mineralocorticoids increase blood sodium,
decrease blood potassium
 sex hormones - small
amount secreted, female
converted to estrigens

Medulla
 Produces epinephrine and
norepinephrine for stress
response - sympathetic
inervation
 The effects include
increase heart rate,
breathing rate, and all
assoisiated sympahtetic
responses

 Pancreatic
 Alpha
Islets/ Islets of Langerhans
cells = glucagon, Beta cells = insulin
 Female
and Male Sex Hormones
 Ovaries – female, Testis - male
 Female characteristics and fertility - release of
estrogen and progesterone
 Male - secretes testosterone - interstitial cells controls male sexual development
 PLACENTA
Temporary endocrine gland
 secretes choriongonadotropin hormone - maintains corpus
luteum - high in urine = pregnancy

 PINEAL
Small pine-coned shaped gland at the roof of the third
ventricle of the brain
 Also called third eye – responds to senses
 Produces melatonin
 inhibits ovarian activity
 influences menstrual cycle
 biorhythms

 HEART
Natriuretic Hormone – secreted by the walls of
the atria – regulates fluid and electrolytes
 Atrial
 THYMUS
 Located
in mediastinum. Has cortex and medulla
 Houses lymphocytes
 secretes thymosin - immune regulator
 Digestive
Glands - stomach and small intestines
secrete hormones to aid digestion - gastrin, secretin
Endocrine Development
 Endocrine
tissue develops from the ectoderm,
epithelial tissue