the endocrine system. major endocrine glands what is a target cell? 15.1 endocrine glands

The endocrine system

Major Endocrine Glands

What is a target cell?

15.1 Endocrine glands

Circulating and local hormones

•Circulating hormones enter the blood.

•Paracrine hormones act on neighboring cells.

•Autocrine hormones act on the secreting cell.

HormonesReceptors

•Signal Chemicals

•Made in endocrine cells

• Transported via blood

•Receptors on target cells

Long Distance Communication: Endocrine Hormones

Figure 6-2a: Long distance cell-to-cell communication

Paracrine and Autocrine Hormones

• Local communication

•Signal chemicals diffuse to target

• Example: Cytokines»Autocrine–receptor

on same cell

»Paracrine–neighboring cells

Figure 6-1c: Direct and local cell-to-cell communication

Mechanisms of Hormone Action

• Endocrine – hormones secreted into the blood acting on downstream target tissues.

• Paracrine – hormones secreted into the interstitial space acting at nearby cells.

• Autocrine – hormones secreted into the interstitial space acting back on same cell.

Figure 6-2b, c: Long distance cell-to-cell communication

Comparison of Nervous System and Endocrine System

• Neurons release neurotransmitters into a synapse, affecting postsynaptic cells• Glands release hormones into the bloodstream • Only target cells of hormone responds

Hormones are Extremely Powerful

ACAT: acyl CoA;cholesterol acyl transferase; ACTH: adrenocorticotropic hormoneAT: angiotensin II; LH: luteinizing hormone

Fatty acids

Cholesterol

cholesterol esterase: activated by AT in ZG (IP3-DAG) ACTH in ZF (cAMP)LH in gonads (cAMP)

MITOCHONDRIONmatrix

Pregnenolone SER

Cholesterol esters

storagevacuole

Cholesterol

Acetyl CoA

LDLCholesterolfrom plasma

ACAT

biosynthesis

AT (ZG) ACTH (ZF) LH (gonads)

StAR

outer membrane

inner membrane

Steroidogenic acute regulatory protein

P-450scc: ACTH-activated: ZFAT-activated: ZGLH-activated: gonads

Figure 2. Initial events common to the biosyn-thesis of steroid hormones

inhibited by: AT, ACTH , LH

mRNA production;Preproinsulin genetranscription1

Figure 5. Structural components (italicized) of the pancreatic -cell involved in glucose-induced biosynthesis and release of insulin.

Glucoseuptake

Transport ofproinsulin to Golgi

3vesiclesTransfer

Synthesis of preproinsulin;Uptake into ER;Excision of signal peptide;Disulfide bonds formed

2Endoplasmicreticulum

Microfilaments

Golgi

Proinsulin to insulin;Packaging of insulin

4

Insulin storage5

Microtubules

Secretorygranules

Ca2+ contractionOf microfilaments

6

........ . Granule fusionwith membrane;Exocytosis of insulin7

Ca2+

Biological structuresNucleus

Mechanism of Hormone Action

Receptor

Protein Kinase A(PKA)

NucleusDNA

Protein Synthesis(Enzymes)

Plasma Membrane

Protein Hormones(cAMP second messenger)

Protein Hormones(cAMP second messenger)

CR

R-ERProtein Synthesis

Mitochondria

S-ERSteroid Synthesis

LH

G

Adenylate Cyclase

Mechanism of Hormone Action

Receptor

Protein Kinase A(PKA)

NucleusDNA

Protein Synthesis(Enzymes)

Plasma Membrane

Protein Hormones(cAMP second messenger)

Protein Hormones(cAMP second messenger)G

Adenylate Cyclase

CR

cAMP

LH

ATP cAMP

CR

R-ERProtein Synthesis

Mitochondria

S-ERSteroid Synthesis

C

RcAMP

Mechanism of Hormone Action

Receptor

Protein Kinase A(PKA)

NucleusDNA

Histones

Protein Synthesis(Enzymes)

Plasma Membrane

Protein Hormones(cAMP second messenger)

Protein Hormones(cAMP second messenger)G

Adenylate Cyclase

LH

ATP cAMP

(+ PO4)

R-ERProtein Synthesis

Mitochondria

S-ERSteroid Synthesis

mRNA

Mechanism of Hormone Action

Receptor

Protein Kinase A(PKA)

NucleusDNA

Histones

Protein Synthesis(Enzymes) mRNA

Plasma Membrane

Protein Hormones(cAMP second messenger)

Protein Hormones(cAMP second messenger)

Cholesterol

GAdenylate Cyclase

C

RcAMP

LH

ATP cAMP

(+ PO4)

R-ERProtein Synthesis

MitochondriaCholesterolPregnenolone

S-ERSteroid Synthesis

Testosterone

Nonsteroid Hormone ActionNonsteroid Hormone Action

Slide 9.9Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Figure 9.1b

Steroid Hormone ActionSteroid Hormone Action

Slide 9.7Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Figure 9.1a

Action of a steroid hormone

Master control

Master integrator

HYPOTHALAMUS

PITUITARY GLAND

AKA = hypophysis

Infundibulum

Sella turcica

hypothalamus

infundibulum

pituitary gland

sella turcica in sphenoid bone

Sella turcica of the sphlenoid bone

Location of the Pituitary

Hypothalamic releasing & inhibiting hormones

• Thyrotropin releasing hormone (TRH)

•Corticotropin releasing hormone (CRH)

•Growth hormone releasing hormone

(GHRH)

•Growth hormone inhibitory hormone

(GHIH) (Somatostatin)

•Gonadotropin releasing hormone (GnRH)

•Prolactin inhibitory hormone (PIH)

»Prolactin releasing hormone (PRH)

Hypothalamic Hormones

Hypothalamic Hormones:

Gondotropin RF Corticotropin RF

(CRF)

Thyrotropin RF Growth Hor RF Prolactin RF

Pituitary Hormones:

Follicle SH &

Lutenizing Hor.

Thyrotropin SHAdrenocorticoptropin

Hormone (ACTH)

ProlactinGrowth

Hormone

Target Gland or Structure:

Ovaries & Testes

(androgens, estrogen)

Adrenal Gland

(cortisol)

Cells of bodyThyroid Gland

(thyroxine)

Bones, breasts & cells of body

Endocrine Feedback Loops

•Negative»gonadal steriods

– Testosterone, Progesterone, Estradiol

»Protein hormones– inhibin

•Positive»Gonadal steroids

– estradiol

Control of Hormonal Secretions

• primarily controlled by negative feedback mechanism

Hypothalamus

Pituitary gland

Target organ

Hormone A

Hormone B

Releasing factorsInhibitingfactors

Neural input

+

+

+

Positive/Negative Feedback loop

Important Point: Secretions are pulsatile vs. continuous

Hypothalamus

Pituitary gland

Thyroid Gland

TSH

T3(inhibitory)

T4

Thyrotropin RH via dorsomedial nucleus

Neural input

+

+

+

Thyrotrophs (5%)

Defects? Hypothyroidism - At the level of the pituitary gland results in low levels of TSH and T3/T4- At the level of the thyroid gland results in normal levels of TSH and low levels of T3/T4

Hypothalamus

Anterior Pituitary

TRH Somatostatin

Thyrotropin (TSH)

Thyroid gland

Estrogen Growth hormone (GH)

Glucocorticoids

Thyroid hormones (T4 and T3)

Feedback inhibition on

hypothalamus TRH secretion

Feedback inhibition on pituitary TSH

secretion

Complex negative feedbackComplex negative feedback

Controlling centers of the CNS

Neural pathways

HypothalamusHypothalamic hormones

AdenohypophysisAdenohypophysal hormones

Peripheral glands

Hormones of peripheral glands

Tissue

Negative Feedback Regulation of Spermatogenesis

• both testosterone and inhibin feed back to hypothalamus and pituitary to inhibit FSH and LH secretion

• sperm production maintained at a relatively constant level (note: testosterone also needed for sperm production)

Pituitary gland

• Be able to identify which hormone comes from the anterior and posterior pituitary

• Hormones: FSH, LH, ACTH, TSH, GH, PRL, MSH, OT, ADH

Pituitary gland – (the hyperlinks work on this page)

PARS DISTALIS: chromophils (50%) and chromophobes (50%). The chromophils can be further subdivided into acidophils (40%) and basophils (10%). The acidophils secrete GH (somatotropes) and prolactin (mammotropes). Basophils secrete TSH (thyrotropes), LH (gonadotropes), FSH (gonadotropes), and ACTH (corticotropes).

PARS NERVOSA: main cell type here is a glial or supporting cell called a pituicyte . The bulk of the pars nervosa consists of axons from neurons in the supraoptic and paraventricular nuclei of the hypothalamus.

PARS INTERMEDIA: rudimentary in humans, lies between the pars distalis and pars nervosa.

BE ABLE TO IDENTIFY THE STRUCTURES WITH HYPERLINKS

Hormones of the Anterior PituitaryHormones of the Anterior Pituitary

Slide 9.17Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Figure 9.4

Figure 6.8

Anterior pituitary

Regulation Hormone Target organ Action Pathology

GHRH and GHIH Growth hormone (GH) Many cells (bones..) Stimulate cell growth and cell division

- not enough: children pituitary dwarfismtoo much: gigantism (children) – acromegaly (adult)

PRH - PIH Prolactin (PL) Breast secretory cells - milk secretion --

TRH Thyroid stimulating hormone (TSH)

Thyroid gland - promote thyroid gland secretion (T3 and T4)

- not enough: hypothyroidism (cretinism in children)- too much: hyperthyroidism

CRH Adrenocorticotropic hormone (ACTH)

Adrenal cortex (3 layers)

- stimulates secretion of adrenal cortex

- not enough: Addison's disease- too much: Cushing syndrome

GnRH Gonadotropin- Follicle stimulating hormone (FSH)- Luteinizing hormone (LH)

Stimulate gamete maturation

Stimulate gonadal gland secretion and gamete formation

- infertility

Con

trol

of

Pro

lact

in Hypothalamus

Ant Pituitary

Breast

Affe

ren

t Stim

ula

tory

pa

thw

ayTRH Dopamine

PRL

I

I+

+ StressHigher centers

Suc

klin

g st

imul

us

Milk production

+

+

PR

L

Con

trol

of

AC

TH Hypothalamus

Ant Pituitary

Adrenal Gland

CRH

Stress

ACTH

I

+

Cortisol

+

AC

TH

I

II

+

Cor

tisol

Con

trol

of

TS

H

Hypothalamus

Ant Pituitary

Thyroid Gland

TRHDopamine

Somatostatin

TSH

I

I+

T3 + T4

+

TS

HI

II

Higher centres

Con

trol

of

LH &

FS

HIn

Mal

eHypothalamus

Ant Pituitary

TestesLeydig Cells Sertoli cells

GnRH

LH

I

+

Testosterone

+

I

II

FSH

Inhibin

+

+

Con

trol

of

LH &

FS

HIn

Fem

ale

Hypothalamus

Ant Pituitary

Ovary

GnRH

LH

I

+

OestradiolProgesterone

+

I

I+I+

FSH

Inhibin

+

Pituitary & Hypothalamus

Hormones of the Posterior PituitaryHormones of the Posterior Pituitary

Slide 9.22bCopyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Figure 9.5

Con

trol

of

Oxy

toci

n

Hypothalamus

Post Pituitary

Oxytocin

Mammary gland

+

Uterus

+

Higher Centers

Str

etch

rec

epto

rs

Stretch receptors

Con

trol

of

Vas

opre

ssin

Hypothalamus

Post Pituitary

Vasopressin

Blood Vessel

Higher Centers

Stretch receptors

Baroreceptors

Osmoreceptors

H2O

Kidney

ANTI-DIURETIC HORMONE

AKA = vasopressin

Hypothalamic osmoreceptors

Water reabsorption

dehydration

increased interstitial fluid osmotic pressure

stimulation of hypothalamic osmoreceptors( -)

1. WATER REABSORPTION BY KIDNEYS2. decreased perspiration

secretion of ADH from posterior pituitary gland

increased water in blood

increased interstitial fluid osmotic pressure

Hormones of Adenohypophysis

• Somatotropes – human growth hormone (hGH)

• Corticotropes – adrenocorticotropin (ACTH)

» Melanocyte stimulating hormone (MSH)

• Thyrotropes – Thyroid stimulating hormone (TSH)

• Gonadotropes – gonadotropic hormones

» Luteinizing hormone (LH)

» Follicle stimulating hormone (FSH)

• Lactotropes – prolactin (PRL)

Hormonal Stimuli

Figure 16.5c

Figure 58-1 Hormones and releasing factors of the hypothalamus and pituitary.

Hypothalamus

Anterior pituitary gland

+ GHRH

Somatostatin -

GH

Liver

Cartilage and bone growthMuscle and other organs:-Protein synthesis and growth

Adipose Tissue -lipolysis- release of FFAsMost Tissues glucose utilization- blood glucose

Hypothalamus

Anterior Pituitary

Growth Hormone (GH)

Liver BoneAdipose Tissue Muscle

GHRH Somatostatin

IGF-1 synthesis and release

Gluconeogenesis

Glycogen synthesis

-Oxidation of fatty acids

Bone and cartilage growth

Glucose uptake

Protein synthesis

Amino acid uptake

Lipolysis

Promotion of secretion

GROWTH HORMONE

1. HYPOGLYCEMIA (low blood sugar)

2. decreased blood fatty acids3. increased blood amino acids4. deep sleep

Inhibition of secretion1. HYPERGLYCEMIA (high blood sugar)

2. increased blood fatty acids3. decreased blood amino acids4. REM sleep5. obesity6. severe emotional states

Actions 1. increased cellular uptake of amino acids = increased protein synthesis = growth/maintenance2. increased lipolysis and gluconeogenesis for energy, leading to hyperglycemia = diabetogenic effect

Regulation of secretion

inhibits GH-IFsecretion

Inhibits GH-RF secretion

HYPOTHALAMUS

hypoglycemia hyperglycemia

GH-RF GH-IF

ANTERIOR PITUITARY GLAND

growth hormone

secretion on secretion off

Growthhormone

Growth factors

http://www.maniacworld.com/worlds_tallest_man.htm

PiCtUrEs

People with this disease can also live a normal life like us. They too can get married and have kids. This is a picture of two dwarfs who are happily married with each other.

Dwarfs can also make friends.

They have friends who aren’t dwarfs

too.This is a picture of

two dwarfs that are at work.

Back to Description

Regulating blood osmolarity

If amount of dissolved material in blood too high, need to dilute blood ADH

Dehydration Lowers blood volume & pressure

Increased waterretention

Increasedvasoconstrictionleading to higherblood pressureReduced

urine volume

Osmotic concentrationof blood increases

ADH synthesized in hypothalamus

ADH released from posterior pituitary into blood

Osmoreceptors NegativefeedbackNegative

feedback

Antidiuretic Hormone

Oxytocin

• Two target tissues both involved in neuroendocrine reflexes

Pituitary Gland Growth Hormone (GH)

•Acromegaly:

• (↑ GH) irreversible

•enlarged cranium and jaw, bulging forehead, thick lips, big tongue

Too much Growth Hormone enlarged cranium and jaw,

Acromegaly

Effect of growth hormone

Dwarfism

By Amy Evans

PeDiGrEeAnD cHaRt

BaCk To InHeRiTaNcE

Control of ADH release …cont.Control of ADH release …cont.

3. arterial blood pressure, due to blood volume ADH.

4. Age: ADH secretion water retention & hyponatremia.

5. Pain, emotional stress & physical trauma ADH secretion.

6. Drugs, e.g. morphine, barbiturates, & nicotine ADH

secretion.7. Alcohol ADH secretion.