Ch. 45—Hormones and the Endocrine System

The Endocrine System

• Includes hormones-secreting cells and tissues• Endocrine glands secrete hormones into body

fluids• Hormonescause a response intarget cells

Positive Feedback

• ‘A’ produces more of ‘B’ which produces more of ‘A’

• More gets you more• See bottom of pg. 254

Negative Feedback

• More gets you less• See top of pg. 254

Cell Surface Receptors• Integral membrane proteins• Communication between cell and outside• Triggers a signal transduction pathway– Series of events

that respond to the signal

– Ex: binding of epinephrine toliver cells which leads to conversion of glycogen to glucose

Intracellular Receptors• Located inside the cell (rather than on its cell

membrane)• Acts as a transcription factor – a protein that binds to specific DNA sequences and controls the flow of DNA to mRNA (transcription)

Hypothalamus

• Portion of the brain• Link the nervous system to the endocrine

system via the pituitary gland• Responsible for metabolic processes

(autonomic nervous system)– Controls body temp, hunger, thirst, fatigue, sleep

Posterior Pituitary

• Stores and secretes oxytocin and vasopressin (or antidiuretic hormone)– synthesized by the hypothalamus– See table 9.1

Anterior Pituitary

• Secretes hormones that act on target organs (adrenal gland, liver, bond, thyroid, gonads)

• Regulates several physiological processes– Stress, growth, reproduction, lactation

*See FSH and LH in Table 9.1