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Endocrine vs Exocrine
Endo = within Exo = out Crine = to secrete
Exocrine glands (sweat, sebaceous, digestive) secrete products through ducts into body cavities or onto body surfaces
Endocrine glands are small, inconspicuous, ductless tissues that deposit products into the interstitial tissues that bathe the cells.
Hormonal Actions
Reproduction Growth and Development Mobility of body defenses Maintenance of blood electrolyte,
water and nutrient balance Regulation of cellular metabolism Energy balance
Regulate the metabolic function of other cells in the body
Chemistry of Hormones Body produces a large variety of hormones Classified chemically as:
A) Amino acid based 1) Makes up the majority
2) Can be simple AA derivatives or long polymers
B) Steroids1) derived from cholesterol
2) only gonadal and adrenocortical hormones
C) Prostaglandins/Eicosanoids1) Derived from lipids
2) Leukotrienes
3) Protaglandins
Endocrine System Focuses on the hormonal control of the body Integrates with nervous system to maintain
homeostasis
Nerves stimulus receivedmillis
econdsMuscle/Gland
Activity
EndocrineGland
Stimulus received
Increase in metabolic
activity in most body cellsSeconds to
Days
Second Messenger Mechanisms
Cyclic AMP
Activated G-protein moves along the
membrane; binds and activates the enzyme
Adenylate Cyclase
Receptor changes shape
and binds to an inactive
G-protein
GTP in the cytoplasm
binds to and “turns
on” the G-protein
ActivatedAdenylate Cyclase
generates the second messenger cAMP
from ATP
Hormone binds to its receptor on
the Target cell membrane
cAMP now triggers cascade reactions to
activate protein kinase,which can catalyze
hundreds of reactions
ATP = Adenocine Triphosphate
How Hormones work?
1. Hormones signal a cell by binding to specific receptors on or in the cell
2. lock and key
3. alter chemical rxns in target cell (ex. Initiate synthesis of new protein)
4. different hormones can work together- synergism
5. different hormones can have opposite effect- antagonism
Prostaglandins
lipid molecules that are similar to, but do not meet usually definition of, a hormone
A through I secreted by seminal vesicles, kidneys,
lungs, iris, brain, thymus varied functions. Ex:
– PGE- regulate HCL secretion in stomach– PGF- cause uterus contractions; induce labor
Hormone Interaction at Target Cells
Multiple hormones acting upon target cells simultaneously = varied resultsPermissiveness = one hormone depends upon
another in order to have full effect (reproductive hormones need thyroid hormones)
Synergism = More than one hormone amplifies the desired effect (glucagon and epinephrine cause liver to release glucose)
Anatgonism = One hormone opposes the action of another(insulin and glucagon produce opposite effects on blood glucose levels)
Control of Hormone Release Humoral Stimuli
– Respond to blood levels of ions and nutrients• Aldosterone (Kidney)
• Insulin (Pancreas)
Neural Stimuli– Respond to innervation
• Sympathetic nervous system releases Epinephrine and Norepinephrine during stress
Hormonal Stimuli– Respond to release of other hormones
The pituitary gland (Hypophysis)1. “master gland”2. stalk- infundibulum3. 2 parts:
1. adenohypophysis (anterior pituitary)- secretes GH, TSH, PRL, LH, FSH, MSH- actually controlled by hypothalamus’ releasing hormones (ex. GnRH)
2. neurohypophysis (posterior pituitary)- secretes ADH and OT
hangs from diencephalon
Pineal Body
Pineal Body- part of diencephalon
– biological clock- sleeping; female reproductive cycle
– secretes melatonin- induces sleep; secretion inhibited by sunlight
Thyroid Gland: Master of metabolism
below larynx secretes Thyroid
hormones– T4
– T3
– Calcitonin, CT
Thyroid GlandsCell Type Follicular cells Parafollicular cells
Hormone Thyroid Hormones (T3,T4) Calcitonin
Regulator TSH Calcitonin
Target Tissue all tissues Bone
Function Regulates basal metabolic rate Regulates blood Ca++ levels in
and has important influences concert with parathyroid hormone.
on growth and maturation. Calcitonin lowers Ca++ by inhibiting
decalcification of bone.
Parathyroid Gland
Acts on: Bone: increases blood calcium by inhibiting osteoblast
deposition of calcium and stimulating osteoclast removal of calcium.
Kidney: increases blood calcium by increasing calcium ion reabsorption by kidney tubular cells; inhibits reabsorption of phosphate ion from the glomerular filtrate
Small intestine: increases the absorption of calcium from the small intestine
Parathyroid Glands- 4 or 5; posterior surface of thyroid; secrete PTH
Calcium regulation
PTH - increases blood calcium by taking in out of bones, kidney, and small intestine
Calcitonin - decreases blood calcium by stimulating uptake into bone
Adrenal Glands (aka suprarenal)
top of kidneys; secrete corticosteroids
which are divided into:
1. Mineralocorticoid- aldosterone
2. glucocorticoids- cortisol; cortisone
3. gonadocorticoids- androgens
The Endocrine Pancreas The endocrine pancreas is
formed by the Islets of Langerhans that are scattered throughout the exocrine tissue.
Secretes the following:– glucagon– Insulin– Somatostatin– pancreatic polypeptide
Islets of Langerhans