Now for a little recap..1. What type of behavior in animals might be

triggered by cold temperatures?2. What type of behaviors might be triggered in

hot temperatures?3. List 2 examples of negative feedback. List 2

examples of positive feedback.4. What is the main type of chemical messenger

in the endocrine system? The nervous system?

Chapter 45Hormones and the Endocrine System

A hormone called ecdysteroid regulates the timing of metamorphosis in this anise swallowtail butterfly.

You must know:

• Two ways hormones affect target organs.• The secretion, target, action, and regulation of

at least 3 hormones.• An illustration of both positive and negative

feedback in the regulation of homeostasis by hormones.

Types of Intercellular

Signaling

• Endocrine System = Hormone-secreting cells + Tissues

• Endocrine glands: ductless, secrete hormones directly into body fluids

• Hormones: chemical signals that cause a response in target cells (receptor proteins for specific hormones)– Affects 1 tissue, a few, or most tissues in body– Or affect other endocrine glands (tropic

hormones)• Regulation by Positive & Negative Feedback

Pheromones Hormones Local Regulators

Chemical signal from 1 individual

to another individual

Chemical signal from endocrine gland through blood to target

cell

Chemical signal from one cell to an adjacent cell

Eg. ant trail; sex phermones

Eg. peptide, steroid hormones

Eg. cytokines, growth factors,

nitric oxide (NO)

Discovery Video: Endocrine System

Types of HormonesPeptide• Water-soluble• Bind to receptors on plasma plasma

membranemembrane & triggers signal transduction pathway

• Affects protein activity already already present present in cell

• Rapid response• Short-lived• Eg. oxytocin, insulin,

epinephrine

Steroid• Lipid-soluble• Enters cell & binds to

intracellularintracellular receptors• Causes change in gene gene

expressionexpression (protein synthesis)• Slower response• Longer life• Eg. androgens (testosterone),

estrogen, progesterone, cortisol

EpinephrineEpinephrine: one hormone many effects

1.Liver cells break down glycogen and release glucose

2.Blood vessels to skeletal muscles dilate

3.Blood vessels to intestines constrict

Hypothalamus

Pituitary Gland

Master Glands

Hypothalamus

Pituitary Gland

• Receives info from nerves and brain

• Initiates endocrine signals

Posterior pituitary gland:

•Oxytocin: contract uterine muscles, eject milk in nursing

•Antidiuretic Hormone (ADH): promote H2O retention by kidneys

Anterior pituitary gland:

•Follicle-stimulating hormone (FSH): development of ovarian follicles (eggs); promote sperm production

•Luteinizing hormone (LH): trigger ovulation; stimulate testosterone production in testes

Master Glands

Hypothalamus regulation of Posterior Pituitary gland

Hypothalamus regulation of Anterior Pituitary gland

Negative feedback systems: • Thyroid hormones• Blood Ca2+ levels• Blood glucose levels

Positive feedback system:• Oxytocin (birthing process; release of

milk/suckling)

BIOFLIX: HOMEOSTASIS – BLOOD SUGAR

Control of Blood GlucoseHigh blood

glucose

InsulinInsulin released from pancreas

Body cells take up glucoseLiver stores glucose as

glycogenglycogen

Blood glucose drops

GlucagonGlucagon released from pancreas

Liver breaks down glycogen and releases

glucoseglucose into blood

Diabetes MellitusDiabetes Mellitus• Type I diabetesType I diabetes (10%):deficiency of insulin

– Insulin-dependent– Autoimmune disorder beta cells of pancreas

destroyed

• Type II diabetesType II diabetes (90%): failure of target cells to respond to insulin– Non-insulin dependent– Insulin produced cells don’t respond (defect in

insulin receptor or response pathway)– Risk factors: obesity, lack of exercise

Thyroid GlandThyroid Gland Hypothalamus

TRH

Anteriorpituitary

TSH

Thyroid

T3 T4

Graves’ Disease:• Autoimmune disorder• Antibodies bind to TSH

receptor• Hyperthyroidism• High temp, sweating,

weight loss, high BP

Stress and the Adrenal Gland

Anabolic-Androgenic Steroid (AAS) Use

• Legally prescribed to treat hormone deficiency, loss of muscle mass (cancer, AIDS)

• Used to enhance performance and improve physical appearance

Effects of AAS AbuseSource: www.drugabuse.gov/infofacts/steroids.html

• aggression• extreme mood swings• liver damage• jaundice• fluid retention• high blood pressure• increases in LDL (“bad”

cholesterol)• decreases in HDL (“good”

cholesterol)• renal failure• severe acne

• For men—shrinking of the testicles, reduced sperm count, infertility, baldness, development of breasts, increased risk for prostate cancer

• For women—growth of facial hair, male-pattern baldness, changes in or cessation of the menstrual cycle, enlargement of the clitoris, deepened voice

• For adolescents—stunted growth due to premature skeletal maturation and accelerated puberty changes; risk of not reaching expected height if AAS is taken before the typical adolescent growth spurt

• In addition, people who inject AAS run the added risk of contracting or transmitting HIV/AIDS or hepatitis.

OK, Now….

1. Compare peptide hormones to steroids.

2. Explain how insulin and glucagon work to regulate blood sugar levels.

3. Which glands and hormones respond when your body is under stress?