© 2013 Pearson Education, Inc.

Endocrine System: Overview

• Acts with nervous system to coordinate and integrate activity of the body

• Influences metabolic activities via hormones transported in blood

• Controlling effect on another part of the body - specific target cells.

• Response slower but longer lasting than nervous system

© 2013 Pearson Education, Inc.

Endocrine System: Overview

• Exocrine glands– Nonhormonal substances (sweat, saliva)– Have ducts to carry secretion to membrane

surface

• Endocrine glands– Produce hormones– Lack ducts

© 2013 Pearson Education, Inc.

Figure 16.1 Location of selected endocrine organs of the body.

Pineal glandHypothalamusPituitary gland

Thyroid glandParathyroid glands(on dorsal aspect of thyroid gland)Thymus

Adrenal glands

Pancreas

Gonads

• Testis (male)• Ovary (female)

© 2013 Pearson Education, Inc.

Chemistry of Hormones

Two main classes

1. Steroids: lipids from cholesterol. Interact with DNA of their target tissue, stimulating the synthesis of new proteins. Sex organs and adrenal cortex produce these.

 

2. Amino acid- never enter target cells, but interact with surface proteins of the cell, inducing the production of an internal messenger that produces the desired effect. Most are this class.

© 2013 Pearson Education, Inc.

© 2013 Pearson Education, Inc.

Figure 16.3 Direct gene activation mechanism of lipid-soluble hormones. Slide 1

The steroid hormone diffuses through the plasma membrane and binds an intracellular receptor.

1

5

The receptor-hormone complex enters the nucleus.

The receptor- hormone complex binds a specific DNA region.

Binding initiates transcription of the gene to mRNA.

The mRNA directs protein synthesis.

New protein

Nucleus

mRNA

DNA

ReceptorBinding region

Receptor-hormonecomplex

Receptorprotein

Steroidhormone Plasma

membraneExtracellularfluid

Cytoplasm

2

3

4

© 2013 Pearson Education, Inc.

© 2013 Pearson Education, Inc.

Hypothalamus controls pituitary by making it secrete or stop secreting hormones- EX. Secretion of TRH (thyroid-releasing hormone) by the hypothalamus, induces the pituitary to secrete TSH (thyroid stimulating hormone). TSH causes the thyroid to release thyroxin into the blood which increases most cells metabolic rate. Increasing thyroxin levels have a negative-feedback on the release of TSH.

© 2013 Pearson Education, Inc.

Hypothalamus

TRH

Anterior pituitary

TSH

Thyroid gland

Thyroidhormones

Target cellsStimulates

Figure 16.8 Regulation of thyroid hormone secretion.

Inhibits

© 2013 Pearson Education, Inc.

Neurosecretory cells extend from the hypothalamus into the pituitary and synthesize the hormone oxytocin. Oxytocin induces contractions of the uterine muscles during childbirth and causes the mammary gland to release milk during nursing.

© 2013 Pearson Education, Inc.

© 2013 Pearson Education, Inc.

Thyroid regulates development and metabolism.a. In adults, thyroid hormone maintains blood pressure, heart rate, muscle tone, digestive and reproductive function.b. Hyperthyroidism causes overheating, profuse sweating, irritability, high blood pressure and weight lose.c. Hypothyroidism causes lethargy, intolerance to cold, and weight gain. If prolonged, this causes goiter, which may be from to little iodine consumed. The normal neg.-feedback control of TSH is interrupted.

© 2013 Pearson Education, Inc.

Hypothalamus

TRH

Anterior pituitary

TSH

Thyroid gland

Thyroidhormones

Target cellsStimulates

Figure 16.8 Regulation of thyroid hormone secretion.

Inhibits

© 2013 Pearson Education, Inc.

© 2013 Pearson Education, Inc.

Figure 16.9 The thyroid gland.

Hyoid bone

Thyroid cartilage

Common carotidartery

Inferior thyroidartery

Trachea

Aorta

Gross anatomy of the thyroid gland, anterior view

Epiglottis

Superior thyroidartery

Isthmus ofthyroid gland

Left subclavianartery

Left laterallobe of thyroidgland

Colloid-filledfollicles Follicular cells

Parafollicular cells

Photomicrograph of thyroid glandfollicles (145x)

© 2013 Pearson Education, Inc.

Figure 16.10 Synthesis of thyroid hormone. Slide 1

Thyroglobulin is synthesized and discharged into the follicle lumen. 1

2

3

4

5

6

7

Golgiapparatus

Iodide (I−)

RoughER

Capillary

Iodide (I–) is trapped (actively transported in).

Lysosome

Lysosomal enzymes cleave T4 and T3 from thyroglobulin and hormones diffuse into bloodstream.

Thyroglobulin colloid is endocytosed and combined with a lysosome.

Iodinated tyrosines are linked together to form T3 and T4.

Iodide is oxidized to iodine.

Iodine is attached to tyrosine in colloid, forming DIT and MIT.

To peripheral tissues

Colloid inlumen offollicle

Thyroid follicular cells

Tyrosines (part of thyroglobulinmolecule)

Thyro-globulincolloid

T3

T4

T3

T4

T3

T4

IodineDIT MIT

Colloid

© 2013 Pearson Education, Inc.

© 2013 Pearson Education, Inc.

Figure 16.12 The parathyroid glands.

Parathyroidglands

Parathyroidcells(secreteparathyroidhormone)

Capillary

Oxyphilcells

Pharynx(posterioraspect)

Thyroidgland

Esophagus

Trachea

© 2013 Pearson Education, Inc.

Figure 16.13 Effects of parathyroid hormone on bone, the kidneys, and the intestine.

Osteoclast activityin bone causes Ca2+

and PO43- release

into blood

Hypocalcemia(low blood Ca2+)

PTH release fromparathyroid gland

Ca2+ reabsorptionin kidney tubule

Activation ofvitamin D by kidney

Ca2+ absorptionfrom food in small

intestine

Ca2+ in blood

Initial stimulus

Physiological response

Result

© 2013 Pearson Education, Inc.

© 2013 Pearson Education, Inc.

Figure 16.6 Growth-promoting and metabolic actions of growth hormone (GH).

Hypothalamussecretes growthhormone–releasinghormone (GHRH), andGHIH (somatostatin)

Anteriorpituitary

Inhibits GHRH release

Stimulates GHIH release

Inhibits GH synthesisand release

Feedback

Indirect actions(growth-promoting)

Liver andother tissues

Insulin-like growthfactors (IGFs)

Produce

Effects

Skeletal ExtraskeletalFat

metabolismCarbohydratemetabolism

Direct actions(metabolic,anti-insulin)

Effects

Growth hormone (GH)

Increased cartilageformation and

skeletal growth

Increased proteinsynthesis, andcell growth and

proliferation

Increasedfat breakdown

and release

Increased bloodglucose and otheranti-insulin effects

Increases, stimulates

Initial stimulus

Reduces, inhibits

Physiological response

Result

© 2013 Pearson Education, Inc.

Figure 16.7 Disorders of pituitary growth hormone.

© 2013 Pearson Education, Inc.

Figure 16.17 Stress and the adrenal gland.

Short-term stress Prolonged stress

Nerve impulses

Spinal cord

Preganglionicsympatheticfibers

Adrenal medulla(secretes amino acid–based hormones)

Catecholamines(epinephrine andnorepinephrine)

Short-term stress response

Stress

Hypothalamus

Corticotropic cells of anterior pituitary

To target in blood

CRH (corticotropin-releasing hormone)

Adrenal cortex(secretes steroidhormones)

Mineralocorticoids Glucocorticoids

ACTH

• Heart rate increasesLong-term stress response

• Kidneys retain sodium and water

• Proteins and fats converted to glucose or broken down for energy• Blood glucose increases

• Blood pressure increases• Bronchioles dilate• Liver converts glycogen to glucose and releases glucose to blood• Blood flow changes, reducing digestive system activity and urine output• Metabolic rate increases

• Blood volume and blood pressure rise • Immune system

supressed

24