ENDOCRINE SYSTEM

Honors Biology

Introduction

• Glands that transmit chemical messengers throughout the body

• Hormones: chemical messengers– Circulate through body– Affect many body cells

GLAND TYPES

• Gland: organ made of cells that secrete materials– Exocrine glands: secrete nonhormonal

chemicals into ducts and transport to locations inside and outside the body; i.e. sweat, mucous, saliva, digestive

– Endocrine glands: ductless and throughout body; secrete hormones into bloodstream through fluid surrounding cells

HORMONE TYPES

• Hormones: – Compounds that are secreted into

bloodstream and affect activity of distant cells– Diffuse into blood

• 2 Categories– Amino acid-base hormones: derived from

amino acids (epinephrine)– Steroid hormones: lipids derived from

cholesterol (estrogen and testosterone)

HORMONE ACTION

• Each hormone only affects certain cells called target cells

PROSTAGLANDINS

• Group of hormone like lipids

• Regulate cell activities

• Not made by specific endocrine glands

• Made by cells throughout body

• Made and travel locally

ENDOCRINE GLANDS

• JIGSAW ACTIVITY– Pituitary Glands– Thyroid Gland– Adrenal Gland– Gonads– Pancreas (done for you)

OTHER ENDOCRINE GLANDS

• Thymus Gland: – Located beneath sternum and between lungs– Development of immune system and T cells

• Pineal Gland:– Near base of brain– Secretes melatonin; cycle regulate sleep

patterns

OTHER ENDOCRINE GLANDS

• Parathyroid Glands– 4 parathyroid glands– Back of thyroid gland– Secrete parathyroid hormone: Increase concentration

of calcium ions in blood

• Digestive (in walls)– Gastrin: stimulates release of digestive enzymes– Secretin: in small intestine; stimulates release of

digestive enzymes from pancreas and bile from liver

FEEDBACK MECHANISMS

• Last step of a series controls the first step– Negative: shuts off– Positive: makes more (going into labor!)

• Homeostasis– Insulin and glucagon work together to balance

blood glucose– Antagonistic hormones

FEEDBACK MECHANISMS

NEGATIVE FEEDBACK

• Final step inhibits first step; thermostat• Example:

– Hypothalamus secretes LH releasing hormone – Stimulates LH from anterior pituitary– LH released into blood and transported– LH binds to target cells in tests– Stimulate cAMP production– Stimulate testosterone secretion– Testosterone binds to target cells– If high testosterone concentration; LH releasing

hormone is inhibited