Endocrine System

Glands Organs which secrete

substances Made of epithelial cells

2 types Exocrine glands: secrete

materials into ducts Endocrine glands (ductless):

secrete materials called hormones into bloodstream

Hormones Released in bloodstream Usually in low concentrations Each type of hormone recognizes only a

certain type of tissue to regulate Target Tissue: hormone increases or decreases

activity

Hormones Regulate

Metabolism Homeostasis Growth Reproduction

The process that controls the level of hormones in the blood is called negative feedback

Organisms must maintain homeostasis to survive in diverse environments.

Homeostasis is the maintenance of constant internal conditions.

Homeostasis is usually maintained through negative feedback.

Negative feedback systems return a condition to its normal (set) point.

• Homeostasis is the maintenance of constant internal conditions.

Human Endocrine System Hypersecretion: excess Hyposecretion: not enough Can cause a disorder

Glands Pituitary (master gland)

Controlled by hypothalamus Location= base of brain Secretes

Follicle stimulating hormone (FSH) ACTH Thyroid simulating hormone (TSH) Growth Hormone (GH)

FSH Stimulates development of eggs in ovaries

ACTH Adrenocorticotropic hormone Stimulates adrenal gland

TSH Stimulates production of thyroxin in thyroid

gland Controls metabolic processes

GH Affects growth of bones and metabolism of

glucose Disorders

Hypersecretion: giantism (enlarged bones) Hyposecretion: dwarfism (reduced bones)

7 feet 8 inches (2.36 meters)

29.2 inches (73 centimeters)

Thyroid Location= neck Secretes thyroxin

Regulates rate of metabolism Needed for mental and physical development

Hypersecretion: nervousness, weight lossHyposecretion: cretinism (mental retardation), small size

Lack of iodine enlarges thyroid (goiter)

Parathyroid Location: Embedded in back of thyroid Secretes parathormone

Controls metabolism of calcium Nerve and muscle functions

Hyposecretion: brittle bones, clotting probelms

Adrenal Gland location: top of kidneys Has outer cortex and inner medulla Secretes

Adrenaline (epinephrine) which raises blood sugar levels, increases heartbeat, increases breathing rate “Fight or flight” hormone Hyposecretion: inability to deal with stress

Adrenal Gland Secretes

Norepinephrine Same effects as adrenaline

Islets of Langerhans Location: pancreas Secretion

Insulin: lets glucose enter cells and liver to be stored as glycogen (lowers blood glucose level in blood) Hypersecretion: low blood

sugar Hyposecretion: diabetes

(sugar in blood and urine)

Islets of Langerhans Secrete

Glucagon: enables conversion from glycogen to glucose (increases blood sugar) Hypersecretion:

high blood sugar

Gonads (sex glands) Male= testes

Produce testosterone Responsible for development of secondary sex

characteristics (deep voice, facial hair) Female= ovaries

Produce estrogen Responsible for secondary sex characteristics (broad

hips, breast development) Hyposecretion: reduction of secondary sex

characteristics

Nervous vs. Endocrine Both forms of cellular communication

Nervous System Endocrine System

Nervous regulation Chemical regulation

Involves neurotransmitters Involves hormones

Fast response Slow response

Short duration Long duration

Only in multicellular organisms

Common to call organisms