Chapter 45 ~Hormones and the Endocrine System

Endocrine and Nervous System Regulation

Nervous system - Electrical signals- Fast acting for immediate response Endocrine system- Hormones - Slower and longer acting

Negative Feedback Loops The hormonal

response reduces the initial stimulus

Prevents overreaction of the system and maintains homeostasis (sugar levels in the blood)

Positive Feedback Loops Reinforces

the stimulus Creates a

greater response

Regulatory systems Hormone~ chemical signal secreted into body

fluids (blood) communicating regulatory messages Target cells~ body cells that respond to hormones Endocrine glands~ hormone secreting glands;

ductless, travel through interstitial fluid or circulatory system

Exocrine glands secrete chemicals through ducts; tears, mucus, saliva

Neurosecretory cells~ actual cells that secrete hormones

Water and Fat Soluble Hormones Water soluble- faster

acting, reversible, protein based, removed from blood quickly– insulin, ADH: attaches to cell membrane

Fat soluble hormones- slower acting and longer lasting, irreversible, stimulated by a trophic hormone – steroids: enters the cell

Paracrine signaling

Cell to cell communication

Induces a change in nearby cells

Travel in short distances Example-Hedgehog

proteins

Local regulators Nitric oxide (NO)`

vessel dilation, increase blood flow for more O2

Growth factors ~ proteins for cell proliferation

Prostaglandins~ immune, reproduction, blood clotting

Local Regulators Histamine- triggers dilation

and increased permeability in the immune response

Interleukins-a cytokine protein that activates lymphocytes

Retinoic acid- necessary for vision and bone growth (anti aging hormones in cosmetics)

Trophic Hormones

Growth effect on the gland it stimulates

It is released in the bloodstream to travel to the target organ or gland

The pancreas- feedback for glucose Islets of Langerhans Alpha cells:

•glucagon~ raises blood glucose levels

Beta cells: •insulin~ lowers blood glucose levels

Type I diabetes mellitus (insulin-dependent; autoimmune disorder)

Type II diabetes mellitus (non-insulin-dependent; reduced responsiveness in insulin targets)

The adrenal glands Adrenal medulla (catecholamines): •epinephrine &

norepinephrine~ increase basal metabolic rate (blood glucose and pressure)

Adrenal cortex (corticosteroids):•glucocorticoids (cortisol)~ raise

blood glucose •mineralocorticoids (aldosterone)~ reabsorption of Na+ and K+

Epinephrine Release

Fight or flight Stress hormone Increases blood

pressure Increases diameter

of blood vessels

The gonads Steroid hormones:

precursor is cholesterol

androgens (testosterone)~ sperm formation; male secondary sex characteristics;

estrogens (estradiol)~uterine lining growth; female secondary sex characteristics

Progestins (progesterone)~uterine lining

growth

Gonadotropic Hormones Stimulates gonads FSH- follicle

stimulating hormone (in women regulates menstruation and ovulation)

LH- luteinizing hormone (ovulation in women and production of testosterone in men)

Arthropods have extensive endocrine systems regulating molting in insects and crustaceans.

The regulation of molting in insects. Neurosecretory cells in the brain produce brain

hormone (BH), which regulates the secretion of ecdysone.

Ecdysone also promotes the development of adult features and molting

Juvenile hormone (JH) promotes the retention of larval characteristics.

Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

I know- It’s my

Pharoahmones

You are so irresistible!!!