Chapter 7b

Introduction to the Endocrine System

Simple Endocrine Reflex: Parathyroid Hormone

Figure 7-10

Bone and

kidney

Low plasma [Ca2+]

Plasma [Ca2+]

Bone resorption

Kidneyreabsorption of

calcium

Parathyroid cell

Parathyroid hormone

Production of calcitriolleads to intestinalabsorption of Ca2+

Negative feedback

Neurohormones: Major Groups

• Adrenal medulla • Catecholamines

• Hypothalamus• Anterior pituitary• Posterior pituitary

Endocrine Control

• Three levels• Hypothalamic stimulation—from CNS• Pituitary stimulation—from hypothalamic

trophic hormones• Releasing factors or Neurohormones

• Endocrine gland stimulation—from pituitary trophic hormones• Stimulate other hormones

Negative Feedback Controls

Figure 7-14

Control Pathway for Cortisol Secretion

Figure 7-15

IGFs

GH

ANTERIORPITUITARY

GHRH

HYPOTHALAMUS

Bone andsoft tissue

Liver

GH cells in anteriorpituitary

Growth

Hypothalamus

Figure 7-17

A Complex Endocrine Pathway

• Growth hormone is an example of a complex endocrine pathway

The Pituitary Gland Anatomy

Figure 7-11

The Pituitary Gland: Anterior

Figure 7-13

HYPOTHALAMIC HORMONES

ANTERIOR PITUITARYHORMONES

NONENDOCRINETARGETS

ENDOCRINE TARGETSAND THE HORMONESTHEY SECRETE

Somatostatin

GHRH* GnRH

Portal system

Anterior pituitary

FSH LH

Neurons in hypothalamussecreting trophic hormones

To target tissues

GH

Endocrine cellsof the gonads

Endocrinecells

Many tissues

Germ cellsof the gonads

Thyroid gland

Thyroid hormones

Adrenalcortex

Cortisol

Liver

IGFs Androgens Estrogens,progesterone

PRFs TRH CRH

TSH ACTHProlactin

Breast

Dopamine*

(Gonadotropins)

GTFLAP

Endocrine cells releasetheir hormones into thesecond set of capillariesfor distribution to therest of the body.

Neurons synthesizingtrophic hormones releasethem into capillaries ofthe portal system.

Portal vessels carry thetrophic hormones directlyto the anterior pituitary.

Mammary glands Thyroid gland Adrenal cortex Gonads

Ovary Testis

Musculoskeletal system

HYPOTHALAMUS

Veins

Artery

ANTERIOR PITUITARY

POSTERIOR PITUITARY

Capillary bed

Capillary bed

TO TARGET ORGANSProlactin Gonadotropins (LH & FSH)

TSHGH ACTH

1

2

3

The Hypothalamic-Hypophyseal Portal System

Figure 7-16

The Pituitary Gland: Posterior

• Posterior pituitary• Vasopressin (ADH)• Oxytocin

Figure 7-12

HYPOTHALAMUS

Vein

POSTERIOR PITUITARY

Vesicles are transported down the cell.

Vesicles containing hormone are stored in posterior pituitary.

Hormones are releasedinto blood.

Hormone is made and packaged in cell body of neuron.

1

2

3

4

The Pituitary Gland: Posterior

Figure 7-12, step 1

HYPOTHALAMUS

POSTERIOR PITUITARY

Hormone is made and packaged in cell body of neuron.

1

The Pituitary Gland: Posterior

Figure 7-12, steps 1–2

HYPOTHALAMUS

POSTERIOR PITUITARY

Vesicles are transported down the cell.

Hormone is made and packaged in cell body of neuron.

1

2

The Pituitary Gland: Posterior

Figure 7-12, steps 1–3

HYPOTHALAMUS

POSTERIOR PITUITARY

Vesicles are transported down the cell.

Vesicles containing hormone are stored in posterior pituitary.

Hormone is made and packaged in cell body of neuron.

1

2

3

The Pituitary Gland: Posterior

Figure 7-12, steps 1–4

HYPOTHALAMUS

Vein

POSTERIOR PITUITARY

Vesicles are transported down the cell.

Vesicles containing hormone are stored in posterior pituitary.

Hormones are releasedinto blood.

Hormone is made and packaged in cell body of neuron.

1

2

3

4

The Pituitary Gland: Posterior

Figure 7-12

HYPOTHALAMUS

Vein

POSTERIOR PITUITARY

Vesicles are transported down the cell.

Vesicles containing hormone are stored in posterior pituitary.

Hormones are releasedinto blood.

Hormone is made and packaged in cell body of neuron.

1

2

3

4

Hormone Interactions

• Synergism• Multiple stimuli—more than additive• 1 + 1 = 3

• Permissiveness• Need second hormone to get full expression

• Antagonism• Glucagons oppose insulin

Example of Synergism

Figure 7-18

Glucagon + Epinephrine + Cortisol

Glucagon + Epinephrine

Epinephrine

GlucagonCortisol

Endocrine Pathologies

Figure 7-19

Endocrine Pathologies

• Hypersecretion: excess hormone• Tumors or cancer• Autoimmune• Grave’s disease—thyroxin

• Hyposecretion: deficient hormone• Goiter—thyroxin• Low Iodine

• Diabetes melitus type I—insulin

Goiter

Pathologies: Abnormal Receptors

• Downregulation • Hyperinsulinemia

• Transduction abnormalities• Testicular feminization syndrome• Pseudohypothyroidism

• Abnormalities of control mechanisms

Primary and Secondary Pathologies

Figure 7-20

Stress Pathologies: Hypocortisolism

Figure 7-21

Cortisol

Symptomsof

deficiency

Symptomsof

deficiency

Cortisol

ACTH ACTH

CRH CRH

Anterior pituitary Anterior pituitary

Adrenal cortex Adrenal cortex

(a) Hyposecretion from damage to the pituitary

(b) Hyposecretion from atrophyof the adrenal cortex

HypothalamusHypothalamus

Pineal Gland and Melatonin

• Influences body clock and antioxidant activity• Other roles need research• SAAD and sexual behavior

Pineal Gland and Melatonin

Figure 7-22 (1 of 3)

Thalamus

Corpuscallosum

The pineal gland

Pineal Gland and Melatonin

Figure 7-22 (2 of 3)

Pineal Gland and Melatonin

Figure 7-22 (3 of 3)

Summary

• Introduction to hormones• Classifications and features of hormones• Regulation controlled by the endocrine and

nervous systems• Interactions of hormones with other

hormones• Endocrine pathologies