Endocrine System

Water soluble hormones?

Amino acid-based hormones

_{^{* thyroid exception}}

Lipid soluble hormones?

Steroid & Thyroid hormones

Water soluble hormones: can & cannot?

• _{^{Can: interact w/ receptors on the plasma membrane}}

• _{^{Cannot: enter cell}}

Lipid soluble hormones: can & cannot?

• _{^{Can: interact w/ intercellular receptors - activates genes}}

• _{^{Cannot: interact with the plasma membrane}}

A hormone binds to a receptor. What is activated?

G protein becomes activated

G protein activates?

_^.

_{^{w/s: GPCR–cAMP signaling pathway}}

Adenylate cyclase protein

Adenylate cyclase does what?

_^.

_{^{w/s: GPCR–cAMP signaling pathway}}

Converts ATP into cAMP 

What is cAMP

_^.

_{^{w/s: GPCR–cAMP signaling pathway}}

_{^{The 2nd messenger in the: GPCR–cAMP signaling pathway}}

cAMP does what?

_^.

_{^{w/s: GPCR–cAMP signaling pathway}}

Activates protein kinases

What do protein kinases do?

Donates phosphate

1st & 2nd Messengers?

_^.

_{^{w/s: GPCR–cAMP signaling pathway}}

1. Hormones

2. cAMP

What are hormones to a receptor?

1st messenger / signal

Steps: GPCR–cAMP signaling pathway

_^w/s

_{^{1. Hormone binds to receptor, activating the G protein}}

_{^{2. G protein activates adenylate cyclase}}

_{^{3. Adenylate cyclase converts ATP to cAMP}}

_{^{4. cAMP activates protein kinases}}

Steps: PIP₂ - Ca signaling pathway 

_^w/s

• _{^{Hormone binds to receptor, activating G protein}}

• _{^{G protein activates phospholipase C (PLC)}}

• _{^{PLC cleaves PIP2 into two 2nd messengers}}

_^-

_{^{DAG - activate protein kinases}}

_{^IP3 ^{- causes Ca release from intercellular storage sites}}

_^-

_{^{Ca is also a 2nd messenger}}

1st & 2nd messengers?

_^.

_{^{w/s: PIP2 - Ca pathway}}

1. Hormones

2. DAG, IP_3, Ca²⁺

Steroid hormone binds to?

_^.

_{^{l/s: genomic pathway}}

An intracellular receptor

The first thing the receptor-hormone complex does?

_^.

_{^{l/s: genomic pathway}}

_{^{Enters the nucleus / binds to a DNA sequence}}

What happens after the receptor-hormone complex binds to DNA?

_^.

_{^{l/s: genomic pathway}}

_{^{Initiates transcription resulting in mRNA}}

What does mRNA do?

Directs protein synthesis (in the ribosomes)

Steps: Genomic Pathway

1. _{^{Hormone binds to intercellular receptor}}

2. _{^{The receptor-hormone complex enters the nucleus}}

3. _{^{Binds to DNA, initiates transcription, mRNA created}}

4. _{^{mRNA leaves nucleus / directs protein synthesis in the ribosomes}}

Hormone release is triggered by what kind of feedback?

Negative feedback

Understanding: negative feedback / hormones

_{^{1. A change in the body disrupts homeostasis}}

_{^{2. An endocrine gland releases a hormone}}

_{^{3. The hormone travels through the blood and binds to its target cells}}

_{^{4. The target cells respond, correcting the imbalance}}

_{^{5. Once homeostasis is restored, hormone secretion decreases or stops}}

_{^{6. The response ends because the original stimulus is gone}}

Why do endocrine glands become stimulated? What is their function?

Synthesize / release hormones in response to 3 stimuli

3 endocrine gland stimuli

_{^{1. Humoral - mineral levels in the blood}}

_{^{2. Neural - sympathetic nervous system fibers (epi / noraepi release)}}

_{^{3. Hormonal - hormone triggers a gland so it can secrete their hormone (tropic)}}

Target Cell Specificity refers to?

_{^{How hormone levels influence the number/presence of receptors}}

2 ways the body manipulates Cell Specificity:

1. _{^{Up-regulation: increases the cell's sensitivity to hormones}}

2. _{^{Down-regulation: decreases the cell's sensitivity to hormones}}

Up-regulation Mechanism

_{^{Target cells form more receptors in response to low hormone levels}}

_^-

_{^{Effect: higher # of receptors in the cell, more hormones bind}}

_{^{(increases cell’s sensitivity to hormone)}}

Down-regulation Mechanism

_{^{Target cells lose receptors in response to high hormone levels}}

_^.

_{^{Effect: lowers # of receptors in the cell, fewer hormones bind}}

_{^{(decreases cell’s sensitivity to hormone)}}

Permissiveness?

_{^{When a hormone needs another hormone to stimulate a cell}}

Synergism?

_{^{When 2+ hormones produce the same effect on the target cell}}

Antagonism?

_{^{When 1+ hormones opposes the action of another hormone}}

Relationship btwn - Hypothalamus & Posterior Pituitary

_{^{The hypothalamus synthesizes 2 hormones that are stored and secreted in the posterior pituitary}}

Relationship btwn - Hypothalamus & Anterior Pituitary

• _{^{Hypothalamus synthesizes inhibitory/release hormones}}

• _{^{These hormones are sent to the anterior pituitary, where they stimulate or inhibit the release of pituitary hormones}} 

Difference btwn the Anterior & Posterior Pituitary

_{^{Posterior - nervous tissue}}

_{^{hypothalamus transports hormones down nerve fibers to PP}}

_^.

_{^{Anterior - endocrine gland}}

_{^{hypothalamus secretes hormones into blood vessels that travel to AP}}

The 2 hormones that Hypo transports to PP?

1. ADH _{^{(antidiuretic hormone)}}

2. Oxytocin

Oxytocin?

_^.

_{^{Released from?}}

_^Triggers?

_{^{Target Cells?}}

• _{^{Posterior Patuitary}}

• _{^{Milk ejection & uterine contractions (positive feedback)}}

• _{^{Mammary glands / muscle cells of the uterus}}

_^.

• _{^{Acts as a neurotransmitter in the brain (PIP2 - Ca signaling pathway)}}

ADH _{^{(antidiuretic hormone)}}

_{^{Released from?}}

_^Triggers?

_{^{Target Cells?}}

• _{^{Posterior Pituitary}}

• _{^{Water retention}}

• _{^{Kidney tubules}}

.

_{^{ADH release triggered by:}}

• _{^{Pain, low BP, drugs}}

• _{^{Osmoreceptors in the hypo monitor solute [ ]. When [ ] is high, PP secretes ADH}}

What Are Tropic Hormones?

_{^{Hormones that stimulate endocrine glands, causing them to release their own hormones}}

The 6 hormones that are synthesized/secreted in the AP?

_{^{1. PRL (prolactin)}}

_{^{2. GH (growth hormone)}}

_^.

_{^{4 tropic hormones}}

_{^{3. TSH (thyroid-stimulating hormone)}}

_{^{4. ACTH (adrenocorticotropic hormone)}}

_{^{5. FSH (follicle-stimulating hormone)}}

_{^{6. LH (luteinizing hormone)}}

_^.

_{^{**TSH/ACTH regulate the secretion of other hormones**}}

Few facts about AP hormones?

• _{^{All are peptide hormones}}

• _{^{Except for GH, they all activate target cells via cAMP}}

• _{^{2 AP hormones regulate the secretion of other hormones}}

GH (growth hormone/somatotropin)

_{^{Released from?}}

_^Triggers?

_{^{Target Cells?}}

_^Tropic?

• _{^{Posterior Pituitary}}

• _{^{Increases metabolism / causes liver to break down glycogen into glucose}}

• _^Liver

• _^No

_^-

_{^{GHRH (hypo) - stimulates GH release in AP}}

_{^{GHIH (hypo) - inhibits GH release in AP}}

TSH (thyroid-stimulating hormone / thyrotropin)

_{^{Released from?}}

_^Triggers?

_{^{Target Cells?}}

_^Tropic?

• _{^{Anterior Pituitary}}

• _{^{Stimulates normal development / secretory activity of thyroid}}

• _^Thyroid

• _^Yes 

_^-

_{^{TRH (hypo) —> AP}}

_{^{TSH —> Thyroid Gland}}

_{^{Thyroid hormones —> target cells (many)}}

ACTH (adrenocorticotropic hormone)

_{^{Released from?}}

_^Triggers?

_{^{Target Cells?}}

_^Tropic?

• _{^{Anterior Pituitary}}

• _{^{Stimulates cortisol / androgen release}}

• _{^{Adrenal cortex}}

• _^Yes

_^.

_{^{CRH (hypo) —> AP}}

_{^{ACTH —> Adrenal Gland}}

_{^{Adrenal hormones —> target cells (many)}}

Gonadotropins: FSH (follicle-stimulating hormone)

_{^{Released from?}}

_^Triggers?

_{^{Target Cells?}}

_^Tropic?

• _{^{Anterior Pituitary}}

• _{^{Stimulates production of gametes (egg / sperm)}}

• _{^{Ovaries / testes}}

• _^Yes

.

_{^{GnRH (hypo) - stimulates FSH release in AP}}

Gonadotropins: LH (luteinizing hormone)

_{^{Released from?}}

_^Triggers?

_{^{Target Cells?}}

_^Tropic?

• _{^{Anterior Pituitary}}

• _{^{Production of sex hormones (estrogen / testosterone)}}

• _{^{Ovaries / testes}}

• _^Yes

.

_{^{GnRH (hypo) - stimulates LH release in AP}}

PRL (prolactin)

_{^{Released from?}}

_^Triggers?

_{^{Target Cells?}}

_^Tropic?

• _{^{Anterior Pituitary}}

• _{^{Milk production}}

• _{^{Mammory glands}}

• _^No

_^.

_{^{PIH (hypo) - inhibits PRL release in AP}}

Thyroid Gland - anatomy

• _{^{The two lobes rest on either side of the trachea}}

• _{^{The isthmus is the connective tissue}}

Thyroid Gland - under a microscope

• _{^{Follicular cells surround colloid-filled follicles}}

• _{^{Parafollicular cells are found next to the follicular cells}}

Steps: synthesis of thyroid hormone

1. _{^{Thyroglobulin is synthesized and discharged into the colloid space}}

2. _{^{Iodide enters the space, oxidizes, becomes iodine}}

3. _{^{Iodine and tyrosine bind}}, _{^{forming DIT & MIT}}

4. _{^{DIT and MIT combine to form T3s and T4s}}

5. _{^{T3s and T4s eventually make their way to the blood}}

6. _{^{T4s get converted into T3 in order to stimulate cells}}

Thyroid Gland

_^Location?

_^Hormone?

_^Triggers?

_{^{Target Cells?}}

• _{^{In the neck, on trachea}}

• _{^{T3/T4 (secreted from the follicular cell)}}

• _{^{Increases basal metabolic rate & heat production}}

• _{^{Almost every cell in the body}}

Calcitonin _^(thyroid)

_{^{Released from?}}

_^Triggers?

_{^{Target Cells?}}

• _{^{Parafollicular cells in thyroid glands (when Ca levels are high)}}

• _{^{Lowers Ca levels}}

• _^Osteoblast

_^.

_{^{Osteoblasts synthesize bone, taking Ca from the bloodstream, depositing it in the bone}}

_{^{Ca levels and blood decreases}}

Parathyroid Gland - anatomy

• _{^{Located on the posterior side of the thyroid gland lobes}}

Parathyroid Gland

_^Location?

_^Hormone?

_^Triggers?

_{^{Target Cells?}}

• _{^{Posterior side of the thyroid gland lobes}}

• _{^{Parathyroid hormone (secreted from parathyroid cells)}}

• _{^{Increases calcium levels in the blood}}

• _{^{Many cells - osteoclasts, kidney, s. intestine}}

_^.

_{^{Osteoclasts degrade, causing calcium to be absorbed into the blood}}

_{^{Calcium levels increase}}

Adrenal Gland - anatomy

_{^{The adrenal gland sits on top of the kidneys (2 glands in 1)}}

_{^{1. Adrenal Cortex: 3 layers of tissue that synthesize/secrete hormones}}

_{^{2. Adrenal Medulla: nervous tissue (a part of SNS)}}

Adrenal Cortex 3 layers + hormone synthesis

_{^{Zona Glomerulosa - mineralocorticoids (aldosterone)}}

_{^{Zona Fasciculata - glucocorticoids (cortisol)}}

_{^{Zona Reticularis - gonadocorticoids (androgen)}}

Mineralocorticoids - aldosterone

_{^{Cortex Layer?}}

_^Triggers?

_{^{Target Cell?}}

• _{^{Zona Glomerulosa}}

• _{^{Sodium retention - kidney pumps Na back into the bloodstream}}

• _^Kidneys

.

_{^{Psst! Clue: mineralocorticoids… Na is a mineral}}

Glucocorticoids - cortisol

_{^{Cortex Layer?}}

^Triggers?

^{Target Cell?}

• _{^{Zona Fasciculata}}

• _{^{Increases blood sugar (due to stress, exhaustion, poor diet)}}

• _^Kidneys

Gonadocorticoids - androgen

_{^{Cortex Layer?}}

^Triggers?

^{Target Cell?}

• _{^{Zona Reticularis}}

• _{^{Support estrogen and testosterone production}}

• _{^{Ovaries / testes}}

Adrenal Medulla

_^Hormones?

_^Triggers?

_{^{Target Cells?}}

• _{^{Secretes epinephrine and norepinephrine (fight or flight situations) ***}}

_^.

_{^{Extra Info (not tested):}}

• _{^{Vasoconstriction | ↑ heart rate | ↑ BP levels | Blood diverted to brain, heart, skeletal muscle}}

• _{^{Tissues involved in the body's stress response}}

***ANP _{^{(atrial natriuretic)}}

_{^{Released from?}}

_^Triggers?

_{^{Target Cells?}}

• _^Heart

• _{^{Blocks renin / aldosterone secretion to decrease BP}}

• _{^{Kidneys - zona glomerulosa}}

Pineal Gland

_^Location?

_^Hormone?

_^Triggers?

_{^{Target Cells?}}

• _{^{Brain posteriorly}}

• _^Melatonin

• _{^{Day/night cycles, puberty}}

• _{^{Fall asleep}}

• _^Brain

Pancreas

_^Location?

_^Hormone?

_^Triggers?

_{^{Target Cells?}} 

• _{^{Behind stomach}}

• _{^{Glucagon (alpha) | insulin (beta) | digestive enzymes (acinar)}}

• _{^{Increases BP | decreases BP | promotes digestion}}

• _{^{Liver | muscle, fat, liver}}

_^.

_{^{Pancreas is comprised of three types of cells}}

• _{^{Acinar - exocrine cells}}

• _{^{Alpha / beta - endocrine cells}}

Gonads

_^Location?

_^Hormone?

_^Triggers?

_{^{Target Cells?}} 

• _{^{Ovaries / testes}}

• _{^{Estrogen plus progesterone / testosterone}}

• _{^{Maturation of reproductive organs, breast development / sperm production, sexual characteristic development}}

Placenta

_{^{Secretes estrogens, progesterone, hCG (human chronic gonadotropin)}}

Thymus

_^Location?

_^Hormone?

_^Triggers?

_{^{Target Cells?}} 

• _{^{Upper chest / behind breast bone}}

• _{^{Thymulin, thymopoietins, thymosins}}

• _{^{Development of T-cells}}

• _{^{Lymph nodes, spleen, lymphatic organs}}

Stimulus: Hypothalamus

_{^{Changes in the body's internal environment}}

Stimulus: Anterior Pituitary

_{^{Arrival of hormones secreted by the hypothalamus}}

Stimulus: Posterior Pituitary

_{^{Nerve impulses from the hypothalamus trigger release of ADH and oxytocin}}

Stimulus: Thyroid Gland

_{^{T3 / T4}}

_{^{TSH | TRH (hypo) —> TSH (AP) —> T3/T4 (thyroid gland)}}

_^-

_^Calcitonin

_{^{↑ Ca levels}}

Stimulus: Parathyroid Gland

↓ Ca levels

Stimulus: Thymus

_{^{Thymulin, thymopoietins, thymosins}}

• _{^{Immune system development (T-cells)}}

• _{^{Most active during childhood}}

Stimulus: Heart

^↑ BP

Stimulus: Pineal Gland

Circadian sleep cycle

Stimulus: Adrenal Medulla

SNS stimulation

Stimulus: Adrenal Cortex

_{^{Mineralocorticoid - Aldosterone - RAAS, ↑K levels, ATCH}}

_^-

_{^{Glucocorticoids - Cortisol - ATCH}}

_^-

_{^{Gonadocorticoids - Androgen - ATCH}}

_^-

_^-

_{^{CRH (hypo) —> ATCH (ap) —> Cortisol (cortex)}}

Stimulus: Pancreas

_{^{Insulin (beta cells): ↑ BS}}

_{^{Glucagon (alpha cells) ↓ BS}}

Stimulus: Ovaries

_{^{FSH / LH}}

_{^{GnRH (hypo) —> FSH / LH (ap)}}

Stimulus: Placenta

Pregnancy

Stimulus: Testes

_{^{FSH / LH (anterior pituitary)}}

Stimulus: Kidneys

_{^{Erythropoietin: ↓ blood oxygen levels (hypoxia)}}

_^-

_{^{Renin: ↓ BP / ↓ blood volume}}