Endocrine system

Nervous system

uses electrical and chemical signals like ACH and other neurotransmitters to send quick brief signals and then stop

Endocrine system

uses only chemical(hormones) signals to affect many systems for potentially longer times

Endocrine gland

ductless gland that secretes hormones directly into the interstitial fluid and blood stream

includes-pituitary, thyroid, parathyroid, adrenal, pineal, gonads

exocrine gland/signal

secrete products into ducts

sebaceous and sweat glands

autocrine singals

chemical signal that elicits response in same cell

paracrine

chemical signal that elicits a response in a nearby cell

Types of hormones derived from amino acids

amines

peptide

protein

amines

amino acids with side groups

peptide

linked amino acids/short chain

protein

linked amino acids/long chain

Types of hormones derived from lipids

steroid- derived from cholesterol, testosterone, estrogens

Water soluble hormones

amines, peptides and proteins

Travel through blood stream unaided, but must bind to receptor outside of cell. The hormone is a first messenger.

-Signal cascade initiated by a G protein, which activates a second messenger (cAMP usually).

-cAMP activates protein kinases.

-Activated protein kinases activate proteins.

Lipid soluble hormones

-Hormone passes through cell membrane easily.

-It then binds with a receptor in the cytoplasm, forming a receptor-hormone complex.

-Complex binds to DNA.

-Triggers RNA transcription

-mRNA moves to cytoplasm, synthesizes protein.

upregulation

if hormone levels are too low, cells increase their receptors for that hormone

Downregulation

when the presence of a hormone causes cells to decrease their receptors for that hormone.

Feedback loops

control most hormone secretion

Positive feedback

levels of a hormone cause additional hormone to be released (e.g. oxytocin in childbirth)

Negative feedback

(more common) levels of a hormone causes inhibition of additional secretion of the hormone (e.g. glucocorticoid from adrenal gland)

Hypothalamus

has both neural and endocrine functions; it is anatomically and functionally related to pituitary; they are connected by the infundibulum 

Posterior pituitary

Does not produce hormones, but does store and secrete hormones produced by the hypothalamus, including oxytocin and ADH. ***

-Oxytocin is important in childbirth and breast feeding.

-ADH (aka vasopressin) is released in response to high blood osmolarity, or solute concentration, to retain water.

Anterior pituitary

does produce hormones; production is regulated by hormones from the hypothalamus: releasing and inhibiting hormones.

-Hormones from the hypothalamus travel to the anterior pituitary through a dedicated circulatory system called the hypophyseal portal system.

-Once produced, hormones from the anterior pituitary leave through a secondary capillary plexus into circulation.

anterior pituitary produces seven hormones…

1. Growth Hormone (GH)

2. Thyroid-stimulating hormone (TSH)

3. Adrenocorticotropic hormone (ACTH)

4. Follicle-stimulating hormone (FSH)

5. Luteinizing hormone (LH)

6. Beta endorphin

7. Prolactin (PRL)

Growth hormone

regulates growth of body

controlled by release of GHRH and GHIH from hypothalamus

Growth hormone effects

Glucose-sparing through lypolysis; fat breakdown spares glucose

Growth by increasing amino acid uptake, reducing apoptosis

Growth hormone disorders

Gigantism: in children, increased GH results in excessive growt

Acromegaly: in adults, increased growth of hands, feet and face

Thyroid Stimulating hormone

regulates thyroid gland

adrenocorticotropic hormone

stimulates the adrenal cortex to secrete cotricosteroids like cortisol

Regulated by corticotropin-releasing hormone (CRH) from hypothalamus.

Follicle-stimulating hormone and luteinizing

hormone

FSH stimulates production and maturation of sperm and eggs.

LH triggers ovulation in females, and stimulates testosterone production in males.

Prolactin (PRL)

promotes lactation/breast feeding

Intermediate pituitary

melanoyte-stimulating hormone(MSH)

can induce melanin production in skins melanocytes

Thyroid

butterfly shaped located anterior to the trachea, inferior to larynx

makes T3 and T4 for metabolism

Parathyroid

 paired glands, 2 on each side of thyroid, embedded on posterior incresae Ca++ absorption in kidneys

Follicle

filled with fluid called colloid, where thyroid hormone production happens.

Thyroid hormone

1. TSH binds to receptors, Iodide ions (I-) transported into follicle cells.

2. Iodide ions move to lumen that borders colloid, get oxidized into Iodine (I2) which passes into colloid.

3. Iodine (I2) is linked to tyrosine, producing 2 intermediaries: tyrosine with 1 Iodine and tyrosine with 2 Iodines.

-These intermediaries are then linked, forming T3 (triiodothyronine). More commonly, 2 of the latter intermediaries link to form T4 (thyroxine), which has 4 iodines. 

-Once stimulated by TSH, these T3 and T4 molecules are released into the bloodstream; regulated by negative feedback.

adrenal medulla

makes epi and norepinephrine

Zona glomerulosa

makes mineralocorticoids

Zona fasciculata

makes cortisol

Zona reticularis

makes androgens

adrenal medulla

Pineal gland

melatonin f

male testes make what?

testosterone and Inhibin

Gonads for females

estrogens produce ovaries

progesterone-menstrual regulations

Inhibin

Pancreas islets

secrete hormones glucagon, insulin, somatostatin and pancreatic polypeptide

what cells do the pancreatic islets contain?

Alpha cell- 20% makes glucagon and stimulated by low glucose

beta cell- 75% makes insulin and stimulated by high glucose

delta cell- 4% makes somatostatin and inhibits both glucagon and insulin

PP cell- 1% makes pancreatic polypeptide, appetite

Blood glucose is regulated by?

glucagon and insulin

Glucagon is secreted by alpha cells in response to low blood sugar levels

Insulin is secreted by beta cells in response to high glucose levels in the blood, to facilitate the uptake of glucose by the cells of the body.