Chapter 45Hormones and the Endocrine System

Receptor location varies with hormone type.

Which one is fat soluble?How do you know?What is an example?

Which one is water soluble? How do you know?What is an example?

Epinephrine

• Also known as Adrenaline• Primarily secreted by Adrenal gland• Also secreted by some neurons as a

neurotransmitter• Mediates the “fight or flight” response• Basically increases the amount of chemical

energy available for immediate use.

In addition, it increases heart rate, stroke volume (amount of blood pumped from ventricles) and dilates the bronchioles in the lungs

Showing the signal pathway for the liver cells to know to start breaking down glycogen

How the Endocrine system works

• There are simple hormone pathways– Negative feedback loops– Positive feedback loops

• There are antagonistic hormones– Insulin and glucagon– Parathyroid hormone and calcitonin

Simple Hormone Pathway Negative Feedback

• The response leads to the reduction in the stimulus and the pathway shuts off.

• Here, release of bicarbonate raises the pH in the duodenum

• Negative feedback is when the response REDUCES the stimulus

Simple Hormone Pathway Positive Feedback

• Oxytocin in mammals regulates milk release during nursing.

• Oxytocin also induces target cells in the uterine muscles

• Positive feedback is when the response REINFORCES the stimulus

Antagonistic Hormones

• Two hormones that operate in a simple endocrine pathway regulated by negative feedback.

• Diabetes Type I• Diabetes Type II

• Insulin and Glucagon controlling blood glucose levels

• Blood Glucose– Insulin released which

triggers the uptake of glucose from the blood

• Blood Glucose– Glucagon promotes the

release of glucose into the blood