Endocrine System and Hormonal Control: Introduction

Vibuntita Chankitisakul, D.V.M., Ph.D.

The body’s regulator

• There are two systems responsible for maintaining homeostasis (homeostasis is maintaining a constant internal environment)

1. Nervous system – brain, spinal cord, nerves 2. Endocrine system – endocrine glands (pancreas,

thyroid, adrenal glands, ovaries/testicles) and hormones

Endocrine glands Nervous System

Nervous vs. Endocrine

The nervous system brings about immediate

responses (such as reflexes and reactions), but

the endocrine system is slower acting and

regulates processes that occur over days or even

months (for example, puberty and sexual

maturation occur over a period of years)

Exocrine v.s. Endocrine glands

Exocrine glands Ducts Lumen and surfaces Such as saliva, sweat

Endocrine glands No duct Chemical messengers

(hormones) Blood stream

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hormone

Endocrine glands

Hormones Hormones are chemical messengers which travel

through the bloodstream and exert their influence in another part of the body.

Hormones reach all parts of the body, but only target cells have receptors for that hormone

Chemical Structure of Hormone

• Proteins – pituitary, gonad • Polypeptides - hypothalamic • Steroids – gonad, adrenal • Fatty acids – prostaglandins • Modified amino acid - pineal

Functions of hormones

• Some hormones have a single action while other have multiple functions

1)metabolism- Thyroxin, ADH

2)growth and development - Thyroxin, GH, Sex Steroids, Cortisol

3)Homeostasis - ADH

4)reproduction - Estrogen, Testosterone, FSH, LH, Progesterone