Transcript Glands of the Endocrine System

The Endocrine
System
Exocrine vs Endocrine
Classified by location of secretion
Exocrine- through tube or duct to a surface
Endocrine- secrete into internal
environment
Endocrine Glands
Can be cell, tissue, or organ (gland)
Hormone- messenger secreted by gland
Target cell- receives the message
– Receptor for hormone
– Hormone creates a response
Tropic hormones- hormone whose target
cell is another endocrine gland
Other Messengers
“Local Hormones”- never reach
bloodstream
– Paracrine- affect neighboring cells
– Autocrine- affect secreting cell
Prostaglandins- lipids messenger usually
affecting organ secreted in
Hormone Action
Steroid Hormone (derivative of
cholesterol)
– Must be carried by plasma proteins through
bloodstream
– Diffuse into any cell
– Binds to receptor in cell
– Activates specific area of DNA
– Protein synthesis is end result
– Example
Hormone Action (cont)
Nonsteriod hormone (amines, peptides,
proteins)
– Hormone (primary messenger) binds to
receptor on outside of cell
– Binding causes activity center inside cell to
activate a messenger (sometimes cAMP)
– This second messenger cause the change in
the target cell
Hormonal Control
Stimulation of hormone release
– Hypothalamus
– Nervous system
– Changing internal environment
Inhibition of hormone release
– Negative feedback loop
Hypothalamus
•Located deep
inside the brain
•Releasing and
inhibiting hormone
secretion to
anterior pituitary
•Direct innervation
to posterior
pituitary
Pituitary Gland
•Located deep within the
brain
•Divided into two sections
•Anterior Pituitaryglandular epithelium
with many blood
vessels
•Posterior Pituitarynerve fibers and
neuroglial cells
Tropic Hormones of the Anterior
Pituitary
Thyroid-stimulating hormone (TSH)
Adrenocorticotropic hormone (ACTH)
Gonadotropins
– Follicle-stimulating hormone (FSH)
– Lutenizing hormone (LH)
Thyroid-stimulating hormone
(TSH)
Stimulation: Thyrotropin-releasing
hormone (TRH) from hypothalamus
Inhibition: Circulating thyroid hormones
decrease TSH and TRH secretion
Target Cell: Thyroid
Action: Increase thyroid secretions
Adrenocorticotropic hormone
(ACTH)
Stimulation: Corticotropin-releasing
hormone (CRH) from hypothalamus
Target Cell: Adrenal cortex
Action: Increase adrenal cortex secretions
Follicle-stimulating hormone
(FSH)
Stimulation: Gonadotropin-releasing
hormone from hypothalamus
Target Cell: Gonads (testes in males and
ovaries in females)
Action:
– Female- maturation of egg; secretion of
estrogen
– Male- development of sperm
Lutenizing hormone (LH)
Also called Interstitial cell stimulating hormone
(ICSH)
Stimulation: Gonadotropin-releasing hormone
from hypothalamus
Target Cell: Gonads (testes in males and
ovaries in females)
Action:
– Female- release of mature egg from ovary (ovulation)
– Male- development of interstitial cell; secretion of
male sex hormones
Other hormone of the Anterior
Pituitary
Growth Hormone (GH)
– Stimulation: GH-releasing hormone from
hypothalamus
– Inhibition: GH release-inhibiting hormone
– Target Cell: Somatic cells
– Action: enhances movement of amino acids
across cell membrane; speeds up rate of
carbohydrate utilization
Other hormone of the Anterior
Pituitary (cont)
Prolactin (PRL)
– Stimulates breast development necessary for
lactation
– Stimulates breast to secrete milk after birth
Posterior Pituitary
Antidiuretic hormone (ADH)
– Stimulation: Nerve Impulse from hypothalamus when
osmoreceptors sense dehydration
– Target Cell: kidneys
– Action: kidneys produce less urine to conserve water
Oxytocin (OT)
– Stimulates contraction of the pregnant uterus
– Stimulates “let-down” of milk
Thyroid
•Location: attached to
front of trachea
•Contains follicles
•Follicles have hollow
center cavity filled with
colloid
Thyroid (cont)
Follicular cells secrete two hormones
– Thyroxine (tetraiodothyronine)- T4
– Triiodothyronine- T3 (much more potent)
– Increases metabolism of carbohydrates,
lipids, and proteins
Extrafollicular cells secrete calcitonin
– Lowers blood calcium level by inhibiting
osteoclasts and making kidney secrete more
calcium in urine
Parathyroid glands
Located on the thyroid in four patches of
highly dense secretory cells
Secrete Parathyroid hormone (PTH)
– Raises blood calcium levels
– Inhibits osteoblasts, stimulates osteoclasts,
makes kidneys conserve calcium, increase
absorption of calcium in intestine
Adrenal glands
Adrenal Cortex
Three layers: outer, middle, and inner
Closely packed masses of epithelial tissue
Outer Layer of Cortex
Outer (glomerulosa)
– Mineralocorticoid (MC)- regulate mineral
electrolytes
Aldosterone
– Stimulated by decrease in blood levels of sodium,
increase in potassium in blood levels, or decrease in
blood pressure
– Cause kidneys to retain sodium and secrete potassium
into urine
– Indirectly water will be retained as well
Adrenal Cortex (cont)
Middle (fasciculata)
– Glucocorticoids- affects glucose metabolism
Cortisol or hydrocortisone
–
–
–
–
Increase gluconeogenisis
Inhibition of protein synthesis
Promotion of fatty acid release from adipose tissue
Produce state of stress
Adrenal Cortex (cont)
Inner (reticularis)
– Sex hormones
Produces androgen hormones
Can be used to synthesize female sex hormones
like estrogens
Adrenal Medulla
Composed of modified neurons
Secrete epinephrine (adrenaline) and
norepinephrine (noradrenaline)
“Fight or Flight” response
Directly innervated by sympathetic
nervous system
Pancreatic Islets (Islets of
Langerhans)
Alpha cells
– Glucagon
Accelerates process of gylcogenolysis
Beta cells
– Insulin
Increeases movement of glucose inside of cells for
metabolism
Stimulates liver to produce glycogen
Thymus
•Located in
mediastinum
cavity
•Hormones
called thymosins
•Important
function in
development of
immune system
Pineal gland
Releases melatonin
– Regulates body clock and sleep cycle
Female Sex Glands
Ovaries
Ovarian
follicles
Corpus
luteum
Male sex glands
Testes
– Interstitial cells produce testosterone
– Testosterone stimulates sperm production
Placenta
•Chorionic
gonadotropins
•Pregnancy
tests test for
this hormone
•Prevents
dissolution of
corpus luteum
Other hormones
Wall of Atria in Heart
– Atrial Natriuretic hormone- regulates fluid and
electrolyte balance by increasing removal of
sodium and water
Various Digestive Glands
Kidneys
– Erythropoietin- red blood cell growth hormone