Hormones and the Endocrine System

Page
4

are

inside

the cell

and

directly regulate gene expression

Hormone

(estradiol)

Hormone-receptor

complex

Plasma

membrane

Estradiol

(estrogen)

receptor

DNA

Vitellogenin

mRNA

for vitellogenin

Slide 24

Multiple Effects of Hormones

The same hormone may have different effects on target cells that have

Different receptors for the hormone

Different signal transduction pathways

Different proteins for carrying out the response.

A hormone can also have different effects in different species.

Slide 25

One hormone, different effects

Glycogen

deposits

 receptor

Vessel

dilates.

Epinephrine

(a) Liver cell

Epinephrine

 receptor

Glycogen

breaks down

and glucose

is released.

(b) Skeletal muscle

blood vessel

Same receptors but different

intracellular proteins

Epinephrine

 receptor

Different receptors

Epinephrine

 receptor

Vessel

constricts.

(c) Intestinal blood

vessel

Slide 26

Specialized role of a hormone in frog metamorphosis

(a)

(b)

Slide 27

Signaling by Local Regulators

In paracrine signaling, nonhormonal chemical signals called local regulators elicit responses in nearby target cells.

Types of local regulators:

Cytokines and growth factors

Nitric oxide (NO)

Prostaglandins - help regulate aggregation of platelets, an early step in formation of blood clots.

Slide 28

Major endocrine glands:

Adrenal

glands

Hypothalamus

Pineal gland

Pituitary gland

Thyroid gland

Parathyroid glands

Pancreas

Kidney

Ovaries

Testes

Organs containing

endocrine cells:

Thymus

Heart

Liver

Stomach

Kidney

Small

intestine

Slide 29

Simple Hormone Pathways

Negative feedback and antagonistic hormone pairs are common features of the endocrine system.

Hormones are assembled into regulatory pathways.

Hormones are released from an endocrine cell, travel through the bloodstream, and interact with the receptor or a target cell to cause a physiological response.

Slide 30

A simple endocrine pathway

Pathway

Example

Stimulus

Low pH in

duodenum

S cells of duodenum