BIO 301 Exam 2

23 cards·by melissaarwood22

Endocrine Glands

Secrete hormones into the blood. Hormones are carried to target cells that have receptors for those hormones.

Amines

Derived from tyrosine and tryptophan. Ex: hormones from the adrenal medulla and thyroid.

Polypeptides and Proteins

Ex: antidiuretic hormone, insulin, and growth hormone

Glycoproteins

Long polypeptides bound to a carbohydrate. Ex: follicle-stimulating and luteinizing hormones

Steroids and Lipids

Derived from cholesterol. Secreted by adrenal cortex and gonads, ringed. Ex: Testosterone, estradiol, progesterone, cortisol.

Polar Hormones

Water Soluble. Cannot pass through plasma membrane. Must be injected if used as a drug (insulin).

Examples of Polar Hormones

Polypeptides, gylcoproteins, catecholamines (epi and norepi)

Nonpolar Hormones

Insoluble. Known as lipophilic hormones. Can enter target cells directly. Include steroids & thyroid hormone. Can be taken orally (pill)

Hormones elicit a physiological function by: #1

Target cells must express a specific receptor for the hormone.

Hormones elicit a physiological function by: #2

The binding of the receptor to the hormone causes a specific sequence of changes to occur in target cell

Hormones elicit a physiological function by: #3

There must be a mechanism to turn off the actions of the hormone. *Negative Feedback*

A target cell can . . .

be responsive to several different hormones at the same time

Hormones may be antagonistic, synergistic, or permissive.

How a cell responds depends on the amount of hormone & the combination of all hormones

Synergistic Effects

Occur when 2 or more hormones work together to produce a particular effect. Can be additive.

Example of Synergistic Effects:

when epinephrine and norepinephrine each affect the heart in the same way

Permissive Effects

Occur when one hormone makes the target cell more responsive to second hormone.

Example of Permissive Effects:

Exposure to estrogen makes the uterus more responsive to progesterone (increases receptors for progesterone)

Antagonistic effects

Occur when two hormones work in opposite directions.

Example of Antagonistic Effects:

Insulin & gulcagon both affect plasma glucose levels. Insulin decreases glucose, glucagon increases glucose.

Hormone Half-Life

Ranges from min. to hours. Most are removed from the blood by the liver (alcohol-medications) Thyroid hormone circulates for several days

Some target cells respond to a particular hormone by increasing the # of receptors it has for that hormone

This makes it more sensitive to subsequent hormone release

Desensitation or Down Regulation

Prolonged exposure to high concentrations of hormone may result in a decreased # of receptors for that hormone. Occurs in adipose cells.

Pulsatile Secretion

To avoid densitization, many hormones are released in spurts.