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Endocrine System

consists of ductless endocrine glands scattered throughout the body


chemical messengers
-go to target cells that contain receptor proteins for it

What are the 2 hormone categories in the endocrine system?


What are the functions of the endocrine system?

-regulate organic metabolism and H2O and electrolyte balance
-induce adaptive changes to help body cope w/ stressful situations
-promote growth and development
-control reproduction
-regulate red blood cell production
-control circulation/digestion/absorption of food

Lipophilic Hormones

-nonpolar hydrophobic (water hating) lipid-loving
-include steroid and thyroid hormones
*can pass through the cell membrane


-polar hydrophilic (water loving) lipid-hating
-do not readily pass through the cell membrane

Second Messengers

messengers that communicate the info of hormones that cannot pass through the membrane

Tropic Hormones

-regulate hormone secretion by another endocrine gland

Endocrine Glands

-do not have ducts
-work w/ nervous system for control of bodily functions
-indirect link to tissue

Exocrine Glands

-have ducts that carry their secretions to specific locations
-direct pathways

How do hormones bind to nuclear receptor proteins?

-lipid hormones travel in blood attached to carrier proteins
-they dissociate from carriers to pass thru plasma membrane of target

Chemical Classification of Hormones



hormones are derived from tyrosine or tryptophan (melatonin)


amino acids maybe short chain or long chain


proteins combined to 1 or more CHO groups


lipids derived from cholesterol (testosterone, estrogen, progesterone, cortisol)


one hormone must be present in adequate amounts for full exertion of another hormone's effects
*if you release epinephrine in a cell and its affects make more binding sites for thyroid hormonesa


-occurs when actions of several hormones are complimentary
-combined effects is greater than the sum of their separate effects


-occurs when one hormone causes loss of another hormone's receptors
-reduces effectiveness of second hormone

High blood levels cause...


Low blood levels cause...


What promotes growth, protein synthesis, and movement of amino acids into cells?

Growth Hormone (GH)

What stimulates thyroid to produce and secrete T4 & T3?

Thyroid Stimulating Hormone (TSH)

What stimulates adrenal cortex to secrete cortisol, aldosterone?

Adrenocorticotrophic Hormone (ACTH)

What stimulates growth of ovarian follicles & sperm production?

Follicle Stimulating Hormone (FSH)

What causes ovulation and secretion of testosterone in testes?

Luteinizing Hormone (HL)

What stimulates milk production by mammary glands?

Prolactin (PRL)

Posterior Pituitary

stores and releases 2 hormones produced in hypothalamus:
*Antidiuretic Hormone

Antidiuretic Hormone

-promotes H2O conservation by kidneys
-causes contraction of smooth muscles in arterioles


-stimulates contractions of uterus during parturition (childbirth)
-stimulates contractions of mammary glands alveoli for milk ejection reflex

Thyroid Gland

secretes T4 & T3 which set BMR and are needed for growth and development

Effects of Thyroid Hormone...

-main determinant of basal metabolic rate
-influences synthesis and degradation of carbs, fat, & protein
-increase target-cell responsiveness to catecholamines
-increases heart rate and force of contractions
-essential for normal growth
-plays crucial role in normal development of nervous system

Hypoactive Thyroids

-an underactive thyroid
-slowing down of physical processes that result from insufficient thyroid hormone
-symptoms: fatigue, constipation, weight gain, low blood pressure

Hyperactive Thyroids

-rapid metabolism resulting from oversupply of thyroid hormone
-symptoms: anxiety, insomnia, weight loss, diarrhea, high blood pressure

Islets of Langerhans

-scattered clusters of endocrine cells in pancreas
-contain alpha, beta, & delta cells

Beta Cells

site of insulin synthesis & secretion in response to high blood glucose

Alpha Cells

produce glucagon

Delta Cells

pancreatic site of somatostatin synthesis: monitors bloods glucose & regulates insulin & glucagon activities (most impotant in regulating fuel metabolism)

Diabetes Mellitus

-most common of all endocrine disorders
-prominent feature is elevated blood glucose levels
-2 major types: Type I & Type II

Type I Diabetes

lack of insulin secretion

Type II Diabetes

normal/even increased insulin secretion but reduced sensitivity of insulin's target cells


-found in adrenal glands
-mainly aldosterone
-influence mineral balance specifically Na+ and K+ balance


-found in adrenal glands
-primarily cortisol
-major role in glucose metabolism, protein and lipid metabolism


-male sex hormone

Adrenal Medulla

-activated during fight/flight response; releases epinephrine
-causes: increased respiratory rate, increased HR & cardiac output, general vasoconstriction which increases venous return, glycogenolysis & lipolysis

General Adaption Syndrome

-stress induced, nonspecific response
-causes ACTH & cortisol release
-affects physiology negatively

Autocrine Regulators

-produced and act within same tissue of an organ
-control gene expression in target cells

Paracrine Regulators

-autocrines produced in one tissue and act on different tissues in same organ


any # of substances that are secreted by specific cells of the immune system

Growth Factors

promote growth and cell divition


provides trophic support for normal and regenerating neutrons

Why do hormones want to work with specific target cells?


What is a hormone that is chemically combined with a protein and carb?


What are the 2 lobes of the pituitary glands?

anterior and posterior

What are some of the affects of the anterior and posterior pituitary glands?

-protein synthesis

Where are adrenal glands located?

above the kidneys

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