endocrine

main glands of endocrine system

pituitary, thyroid, parathyroid, adrenal, pineal

Hypothalamus

A neural structure lying below the thalamus; helps govern the endocrine system via the pituitary gland,

chemical classification of hormones

amino acid-based, steriod based, eicosanoids

mechanism of hormone action

Only target cells will respond to a hormone. Recognition leads to an alteration in target cell activity. Response depends on the type of target cell

alterations

plasma membrane permeability• membrane potential• Stimulating synthesis of enzymes or proteins• Activating or deactivating enzymes• Inducing secretory activity• Stimulating mitosis

Lipid-soluble hormones

internal receptors inside the cel

Water-soluble hormones:

receptors in the plasma membrane

cAMP pathway

1. Amino acid hormone binds membrane receptor.

2. G protein activated by displacement of GDP with GTP.

3. Adenylate cyclase activated by G protein

4. cAMP made by converting ATP

5. Protein kinase cascade. Signaling Cascade

PIP- CA pathway

Hormone binds to its receptor•

G-protein is activated•

PLC enzyme splits PIP2 into 2 second messengers DAG and IP3

Calcium acts as a second messenger

Ca binds to calmodulin, activating the signaling cascade

Direct Gene activation

Steroid diffuses and binds to the intracellular receptor

The receptor hormone complex enters the nucleus

The receptor complex binds to a DNA region

Transcription of the gene to mRNA was initiated

mRNA directs protein synthesis

Target cell activation depends on

Binding of a hormone to its receptor

Levels of hormones in the blood

Number of receptors on or in the target cells

Affinity

up-regulation

persistently low levels of a hormone can trigger its target cells to express more receptors

down regulation

Prolonged exposure to a hormone can cause the cell to express fewer receptors.

affinity

strength of binding between hormone and receptor

Humoral stimulus

Hormone release caused by altered levels of certain critical ions or nutrients

Neural stimulus

hormone release caused by neural input

hormonal stimulus

hormone release caused by another hormone (a tropic hormone)

Hormones circulate in the blood in 2 forms

free or bound to carrier

Amount of hormone in blood atany given time depends on

Rate of release anddSpeed at which hormone is inactivated and removed from the body

Permissiveness

One hormone cannot exert its full effects withoutanother hormone

Synergism

Combined effects of multiple hormones producing thesame effect

Antagonism

One hormone opposes the action of another

Infundibulum

connects the pituitary gland to the hypothalamus

posterior pituitary

Hormone storage: not a true endocrine gland

Composed largely of neuronal tissue

Releases neurohormones that are produced in the hypothalamus

Posterior pituitary + infundibulum = neurohypophysis

posterior pituitary hormones

oxytocin and ADH

oxytocin

acts through the pip-ca pathway

for stretching of the uterus and Hormonal trigger for milk ejection: Let-down reflex

also a neurotransmitter for affectionate behavior

Antidiuretic Hormone (ADH)

inhibits or decreases urine production

directed toward the kidney tubles by the cAMP pathway

anterior pituitary hormones

GH, TSH, ACTH, FSH, LH, PRL

many are tropic hormones that stimulate endocrine glands

only GPH isnt cAMP

prolactin

Stimulates milk production in female mammaryg lands

ACTH (adrenocorticotropic hormone)

Stimulates release of corticosteroids, particularly cortisol which regulates metabolism, blood pressure, stress, immune function

gonadotropins

Regulate gonad maturation and function by Gonadotropin-releasing hormone (GnRH), which is absent in pre-pubescent humans

Follicle-stimulating hormone (FSH

Promotes production of gametes(sperm and egg) in both sexes

Luteinizing hormone (LH

Promotes production of gonadal hormones•

In males: production of testosterone•

In females: production of ovarian hormones and ovulation

thyroid gland

two lobes connected by an isthmus

Colloid

amber-colored, sticky material consisting of thyroglobulin and iodine that fills the thyroid follicles

Thyroglobulin

precursor tothyroid hormone

Follicular cells

line thyroid follicles &produce thyroglobulin

parafolliculer cells

produce calcitonin

Thyroid Hormone: Major Effects

Body's major metabolic hormone

Thyroxine and Triiodothyronite(T3 and T4)

Synthesis of Thyroid Hormone

Iodine is attached to tyrosine in colloid

Iodinated tyrosines form T3 and T4

cleave T3 and T4 from thyroglobulin

Calcitonin

Inhibits osteoclasts

Stimulates uptake of calcium into the bone

Parathyroid gland

Calcium reabsorption and activation of vitamin D by kidney

adrenal gland

sits on top of kidneys and is made up of the medulla(inner part) and cortex(outer part)

adrenal cortex

three layers: Zona glomerulosa, Zona fasciculata(produces glucocorticoids) , Zona reticularis (produces adrenal sex hormones

Aldosterone

Regulates contractions of sodium and potassium

Glucocorticoids

for gluconeogenesis

three types: Cortisol, Cortisone, Corticosterone

Gonadocorticoids: Adrenal Sex Hormones

Weak androgens (male sex hormones) converted to testosterone in tissue cells, some to estrogens

drives the development of axillary and pubic hair and sex drive

three types: Androstenedione and Dehydroepiandrosterone (DHEA)

Adrenal Medulla

Epinephrine & norepinephrine• Released during fight-or-flightresponse

pineal gland

makes melatonin

pancreas

Has both endocrine and exocrine gland cells

acinar cells make pancreatic juice

alpha cells make glucagon

beta cells make insulin

glucagon

hyperglyemic

target is liver

converts glycogen -> glucose and releases to blood

insulin

Hypoglycemic

comes from proinsulin

lower glucose by: increases transport of glucose, inhibits glycogen conversion, inhibits amino acid and fat conversion to glucose

gonads

females release ova and produce estrogen and progestrone(helps with breast development and changes in uterine mucosa

Males release sperm and produce testosterone

placenta

Temporary endocrine organ

Gigantism

Too much growth hormone inchildhood

Acromegaly

Too much GH after epiphyseal plates have close do

Overgrowth of bone in face and extremities

dwarfism

Too little GH in childhood If detected early, can be treated with GH

Hypothyroidism

Lowers the metabolic rate

Hyperthyroidism

Grave's Disease is an autoimmune disorder that increases metabolic rate

Symptoms: sweating, irregular heartbeat, weight loss, protruding eyes

Type 1 Diabetes

insulin-dependent and early onset, Autoimmune disease; the body attacks its beta cells because of molecular mimicry. Makes it difficult to control the sugar level

type 2

non-insulin dependent, adult-onset Insulin is produced but insulin receptors can't respond= Insulin resistance

gestational diabetes

High blood sugar levels that develop during pregnancy• Pregnancy/placental hormones may interfere withinsulin binding to insulin recepto

risks: Pre-eclampsia Depression Baby of large size, Underdeveloped newborn lung