Neurohormones: Major Groups

• – • • Pituitary gland is two glands fused in one • is neural tissue and secretes two neurohomones: (antidiuretic or ADH) and • is endocrine tissue and six : , thyrotropin, adrenocorticotropin, , follicle-stimulating hormone, and luteinizing hormon

© 2016 Pearson Education, Inc. Figure 7.8a The Pituitary Gland

HYPOTHALAMUS

The pituitary gland sits in a protected pocket of bone, connected to the brain by a thin stalk. Infundibulum is the stalk that connects the pituitary to the brain.

Sphenoid bone

Posterior pituitary is an extension of the neural tissue.

Anterior pituitary is a true endocrine gland of ANTERIOR POSTERIOR epithelial origin.

© 2016 Pearson Education, Inc. Figure 7.8b The Pituitary Gland

The anterior pituitary is a true endocrine gland that secretes six classic hormones. Neurohormones from the hypothalamus control release of the anterior pituitary hormones. The hypothalamic hormones reach the anterior pituitary through a specialized region of the circulation called a portal system.

Neurons synthesizing HYPOTHALAMUS trophic neurohormones release them into capillaries of the portal system.

Capillary bed

Portal veins carry the trophic neurohormones Artery directly to the anterior pituitary, where they act on the endocrine cells.

POSTERIOR PITUITARY

Capillary bed Endocrine cells release their peptide hormones into the second set of ANTERIOR PITUITARY capillaries for distribution to the rest of the body. Veins

TO TARGET ORGANS

Prolactin Gonadotropins (LH & FSH) ACTH GH TSH

Ovary Testis

Mammary glands Musculoskeletal system gland Adrenal cortex Gonads

© 2016 Pearson Education, Inc. Figure 7.8c The Pituitary Gland

The posterior pituitary is an extension of the brain that secretes neurohormones made in the hypothalamus.

HYPOTHALAMUS

Neurohormone is made and packaged in cell body of .

Vesicles are transported down the cell.

Vesicles containing neurohormone are stored in posterior pituitary.

POSTERIOR PITUITARY

Vein

Neurohormones are released into blood.

Oxytocin Vasopressin Ile Gln Phe Gln

Asp Tyr Tyr Asp

Cys Cys Cys Cys Gly Gly Pro Pro Leu Arg

Mammary glands and uterus Kidneys

© 2016 Pearson Education, Inc. Figure 7.8c The posterior pituitary is an extension of the brain that secretes neurohormones made in the hypothalamus. Slide 1

HYPOTHALAMUS

Neurohormone is made and packaged in cell body of neuron.

Vesicles are transported down the cell.

Vesicles containing neurohormone are stored in posterior pituitary.

POSTERIOR PITUITARY

Vein

Neurohormones are released into blood.

© 2016 Pearson Education, Inc. Figure 7.8c The posterior pituitary is an extension of the brain that secretes neurohormones made in the hypothalamus. Slide 2

HYPOTHALAMUS

Neurohormone is made and packaged in cell body of neuron.

POSTERIOR PITUITARY

© 2016 Pearson Education, Inc. Figure 7.8c The posterior pituitary is an extension of the brain that secretes neurohormones made in the hypothalamus. Slide 3

HYPOTHALAMUS

Neurohormone is made and packaged in cell body of neuron.

Vesicles are transported down the cell.

POSTERIOR PITUITARY

© 2016 Pearson Education, Inc. Figure 7.8c The posterior pituitary is an extension of the brain that secretes neurohormones made in the hypothalamus. Slide 4

HYPOTHALAMUS

Neurohormone is made and packaged in cell body of neuron.

Vesicles are transported down the cell.

Vesicles containing neurohormone are stored in posterior pituitary.

POSTERIOR PITUITARY

© 2016 Pearson Education, Inc. Figure 7.8c The posterior pituitary is an extension of the brain that secretes neurohormones made in the hypothalamus. Slide 5

HYPOTHALAMUS

Neurohormone is made and packaged in cell body of neuron.

Vesicles are transported down the cell.

Vesicles containing neurohormone are stored in posterior pituitary.

POSTERIOR PITUITARY

Vein

Neurohormones are released into blood.

© 2016 Pearson Education, Inc. Endocrine Control

• A trophic hormone controls the secretion of another hormone • Hypothalamic-hypophyseal (pituitary) portal system • Three integrating centers – Hypothalamic stimulation—from CNS – Anterior pituitary stimulation—from hypothalamic trophic hormones – Endocrine gland stimulation—from anterior pituitary trophic hormones (except prolactin)

© 2016 Pearson Education, Inc. Endocrine Control

• Anterior pituitary hormones control growth, metabolism, and reproduction • Negative feedback loops – Short-loop pathway • Parathyroid – Long-loop pathway • Cortisol

© 2016 Pearson Education, Inc. Figure 7.9 Hormones of the Hypothalamic-Anterior Pituitary Pathway

© 2016 Pearson Education, Inc. Figure 7.10 The growth hormone pathway

© 2016 Pearson Education, Inc. Figure 7.11a Negative feedback in complex endocrine pathways

© 2016 Pearson Education, Inc. Figure 7.11b Negative feedback in complex endocrine pathways

© 2016 Pearson Education, Inc. Hormone Interactions

• Synergism – Combined effect is greater than the sum of individual effects • Permissiveness – Need second hormone to get full effect • Antagonism – One substance opposes the action of another – Competitive inhibitors vs. functional antagonism – opposes

© 2016 Pearson Education, Inc. Figure 7.12 Synergism

© 2016 Pearson Education, Inc. Endocrine Pathologies

• Hypersecretion: excess hormone – Caused by tumors or exogenous iatrogenic treatment – Negative feedback may lead to atrophy of gland • Hyposecretion: deficient hormone – Caused by decreased synthesis materials or atrophy – Absence of negative feedback leads to overproduction of trophic hormones

© 2016 Pearson Education, Inc. Figure 7.13 Negative feedback from exogenous hormone

© 2016 Pearson Education, Inc. Pathologies: Abnormal Receptors

• Down-regulation – Decreased number of receptors – Hyperinsulinemia • and abnormalities – Missing or nonfunctional receptors – Androgen insensitivity syndrome – Pseudohypothyroidism

© 2016 Pearson Education, Inc. Pathologies: Abnormal Receptors

• Diagnosis depends on the complexity of the reflex – Primary pathology due to issues with last endocrine gland in pathway – Secondary pathology due to pituitary gland – Tertiary pathology due to hypothalamus • Example of hypocortisolism due to primary or secondary pathology

© 2016 Pearson Education, Inc. Figure 7.14 Hypercortisolism

© 2016 Pearson Education, Inc. Figure 7.15 Hypocortisolism

© 2016 Pearson Education, Inc. Hormone Evolution

• Evolutionary conservation of hormone function • Proteomics – gene-related peptide example • Vestigial – Melanocyte-stimulating hormone example • Comparative – and example – Melatonin plays a role in sleep-wake cycle and internal clock

© 2016 Pearson Education, Inc. Figure 7.16-2 The Pineal Gland

© 2016 Pearson Education, Inc. Figure 7.16-3 The Pineal Gland

© 2016 Pearson Education, Inc. Figure 7.16-4 The Pineal Gland

© 2016 Pearson Education, Inc. Summary

• Hormones • The classification of hormones • Control of hormone release • Hormone interactions • Endocrine pathologies • Hormone evolution

© 2016 Pearson Education, Inc.