Endocrine System (help)

3 main hormone types

1. peptide

2. steroid

3. amino acid derived

endocrine

hormones secreted directly into the bloodstream

paracrine

hormones secreted to neighboring cells

autocrine

hormones secreted onto the same cell that’s secreting it

place where peptide hormones are synthesized

rough ER

water soluble, not lipid soluble

peptide hormones

indirect stimulation

peptide hormones interact with cell surface receptors to kick off a signal transduction pathway to carry out the signaling

ligand-gated receptors

receptor proteins capable of inducing intracellular signal transduction pathways once an extracellular ligand is bound

ex: IP3/DAG pathway

second messengers

signaling molecules independent of the original hormone which propagate signals within the cell

examples of second messengers

cAMP, IP3, DAG, Ca²⁺

GPCRs

G protein coupled receptors

associated with a G protein on the intracellular domain, responsible for conveying intracellular signals

RTKs

receptor tyrosine kinases

twin components dimerize to and cross phosphorylate to influence intracellular signasl

ligand-gated ion channels

channel proteins that change shape once a ligand is bound in order to allow flow of ions across membrane

PIP2 is cleaved into…

secondary messengers IP3 and DAG (DAG is not important)

IP3 binds…

ligand-gated Ca²⁺ channels on surface of ER

place where steroid hormones are synthesized

smooth ER

structure of steroid hormones

4-rings (3 hexanes and 1 pentane)

all hormones produced by the adrenal cortex and gonads (reproductive organs) are…

steroid hormones

produced by adrenal cortex

glucocorticoids

mineralocorticoids

androgenic steroids

produced by reproductive organs

progesterone

testosterone

estrogen

lipid soluble, not water soluble

require water soluble transport protein to travel through the blood

steroid hormones

direct stimulation

steroid hormones directly bind intracellular receptors of the cytoplasm of the nucleus

these complexes directly bind DNA to affect transcription

where are amino acid hormones synthesized

rough ER and cytosol

derived from tyrosine

all hormones produced by adrenal medulla are…

amino acid hormones

produced by adrenal medulla

epinephrine

norepinephrine

T3 and T4 are…

amino acid hormones

hypothalamus

regulation of hormone secretion

coordinates homeostasis

pituitary gland

hormones production, storage, and release

just below hypothalamus

two parts (anterior and posterior)

posterior pituitary gland

direct neuronal extension of hypothalamus

constructed of neuronal tissue

hormones produced by posterior pituitary gland

antidiuretic hormone (ADH)

oxytocin

antidiuretic hormone (ADH)

aka vasopression

increases water reabsorption in nephron by increasing number of aquaporins in collection duct

decrease in urination

oxytocin

causes uterine contraction during labor

RELEASE of milk during breastfeeding

• targets uterus and mammary glands

operates in positive feedback loop

anterior pituitary gland

produces its own hormones

composed of glandular tissue (not neural tissue)

hypothalamic releasing hormones

Hormones released by the hypothalamus in order to stimulate the release of hormones generated by the anterior pituitary gland

hypothalamic inhibiting hormones

Hormones released by the hypothalamus to inhibit the release of other hormones by the anterior pituitary

hypophyseal portal system

connects anterior pituitary gland to hypothalamus and allows for quick diffusion of hormones through portal vein

hypothalamic releasing hormones

GnRH, TRH, CRH, GRH

GnRH (gonadotropin releasing hormone)

causes release of luteinizing hormone (LH) and follicle stimulating hormone (FSH)

TRH (thyrotropin releasing hormone)

causes release of thyroid stimulating hormone (TSH)

CRH (corticotropin releasing hormone)

causes release of adrenocorticotropic hormone (ACTH)

GRH (growth hormone releasing hormone)

causes release of growth hormone (GH)

tropic hormones

target other endocrine glands for further hormone release

direct hormones

directly target organs to cause effects

anterior pituitary gland tropic hormones

FSH, LH, ACTH, TSH

FSH (follicle stimulation hormone)

follicle growth in females

sperm maturation in males

LH (luteinizing hormone)

stimulates ovulation and formation of corpus luteum in females

production of testosterone in males

ACTH (adrenocorticotropic hormone)

stimulates the release of glucocorticoids from adrenal gland to fight stress

• increases body’s glucose levels

TSH (thyroid stimulation hormone)

stimulates thyroid to produce T3 and T4 to increase metabolism

anterior pituitary direct hormones

prolactin, GH

prolactin

stimulates development of mammary gland and increases milk production after birth

GH (growth hormone)

stimulates growth/division of cells

pineal gland

gland in brain responsible for melatonin production

• circadian rhythm

thyroid gland

largest endocrine organ

• in front of trachea

parathyroid glands

endocrine glands on posterior side of the thyroid

produced by thyroid

T3, T4, calcitonin

T3 and T4

increase metabolism

• released in response to TSH stimulation from anterior pituitary gland

• amino acid hormones

• negative feedback effect on TSH and TRH secretion

T3

active form of hormone set

4x more potent

T4

stable form of hormone

main circulating form

calcitonin

decreases blood calcium levels upon release from parafollicular thyroid cells

• stimulates osteoblast use of calcium to generate new bone

goiter

enlargement of thyroid

caused by iodine deficiency

PTH (parathyroid hormone)

increases calcium levels in blood

• stimulates osteoclasts to free Ca by breaking down bone

pancreas

consists of endocrine and exocrine tissue

what hormones does pancreas secrete

glucagon (from alpha cells)

insulin (from beta cells)

somatostatin (from delta cells)

• endocrine function

exocrine function of pancreas

secretion of digestive enzymes into small intestine via pancreatic duct

glucagon

released by alpha cells in times of low blood glucose

stimulates liver and fat tissue to release stored glucose

insulin

released by beta cells in times of high blood glucose

stimulates liver, fat, and muscle tissues to store glucose

insulin is what type of hormone

peptide

insulin associates with

RTKs, resulting in second messengers

somatostatin

inhibitory hormone released from delta cells

inhibits insulin, glucagon, and GH from anterior pituitary

adrenal gland

outside surface of kidneys

2 different types (cortex and medulla)

stress combatting

adrenal cortex

outer region of adrenal gland

adrenal medulla

inner region of adrenal gland

adrenal cortex

long term stress

release steroid hormones upon stimulation by ACTH from anterior pituitary

glucocorticoids (cortisol)

raise blood glucose levels for fuel during long periods of stress, lowers immune response

released by adrenal cortex

mineralocorticoids (aldosterone)

increase blood volume/pressure by increasing reabsorption of Na⁺, passive reabsorption of water via osmosis

released by adrenal cortex

androgens

male sex hormones produced in small amounts by adrenal cortex

released by adrenal cortex

glucocorticoids (cortisol), mineralocorticoids (aldosterone), androgens

adrenal medulla

releases amino acid hormones in response to stimulation by sympathetic nervous system

short term stress

released by adrenal medulla

catecholamines

long term stress is met with _____ hormones while short term stress is met with _____ hormones

steroid, amino acid