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97 Cards in this Set

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Endocrine gland
secrete chemical signals that influence tissues that are separate from the glands by some distance
Endocrine system
composed of glands that typically secrete chemical signals into the circulatory sytem
hormone
chemical signal created by endocrine glands.

A ligand that is
1). produced in minute amounts by a collection of cells

2). is secreted into the interstitial spaces

3). enters the circulatory system

4). acts on target tissues at another site in the body to influence the activity of those tissues in a specific fashion
compare and contrast the nervous system vs. the endocrine system
hormones generally considered amplitude-modulated signals, whereas action potentials are considered frequency-modulated signals.

endocrine works from minutes to hours, whereas action potentials respond within milliseconds.
Name 5 categories of intercellular chemical signals (not hormones)
1. Autocrine

2. Paracrine

3. Pheromones

4. Neurotransmitters

5. Neuromodulators
Autocrine chemical signals
1. released by cells

2. have local effect on same cell type as 'releaser'
Paracrine chemical signals
1. released by cells

2. affect other cells locally without going into bloodstream
Pheromones
1. secreted into the environment

2. modify the behavior of other individuals of the same species.
Neuromodulator
Substance that influences the sensitivity of neurons to neurotransmitters but neither strongly stimulates nor strongly inhibits neurons by itself
List 3 categories of hormones and their subcategories (based on chemical structure)
1. proteins / polypeptides

2. derivitives of amino acids

3. lipids
What are the 3 major patterns by which hormone secretion is regulated?
1. Non Hormonal Regulation:
changes in the extracellular concentration of a substance other than a hormone and the effect of those changes on the endocrine gland

2. Nervous System Regulation:
neural control of the endocrine gland (neurons synapse with hormone producing cells and recieve neurotransmitters when action potentials fire)

3. Hormonal Regulation:
endocrine gland working to increase or decrease another endocrine gland.
Is hormone regulation generally negative or positive feedback?
Negative Feedback
Chronic Hormone Regulation
A relatively constant concentration of hormone is maintained in the circulating blood over a relatively long period.
Acute Hormone Regulation
A hormone rapidly increases in the blood for a short time in response to a stimulus.
Cyclic Hormone Regulation
A hormone is regluated so that it increases and decreases in the blood at a relatively constant time and to roughly the same amount.
What effect does a hormone binding to a plasma protein have on the level of hormone in the blood?

What is the effect on the amount of time a hormone remains in the blood?
Hormones bind to proteins to make a sort of resevoir. As the level of "free" hormones decreases, they free the bind and are then available to effect target tissue.

hormones that bind to binding proteins can remain constant in the blood for longer periods of time.
Why does the wall of capillaries or organs regulated by protein hormones have large pores?
they are bigger and take a longer time to pass through, unlike lipid soluable hormones which readily pass through the capillary walls.
Fenestrae
large pores in capillary walls
half-life
lenght of time it takes for half a dose of a substance to be eliminated fromt eh circluatory system
Describe the activities of a hormone with a short half life.

Are they water or lipid soluable?
concentrations increase and decrease rapidly within the blood

rapid onset and short duration

Water soluable such as glycoproteins, proteins, epinephrine, norepinephrine
What activities do hormones with long half lives do?

Are they water soluable or lipid soluable?
Usually bind to binding proteins, prolonging their ride through the circulatory system

Maintain a relatively constant level through time

Lipid soluable
Name 4 ways half life of hormone is shortened.
1. Excretion

2. Metabolism (enzymes degrade in blood)

3. Active Transport (recycled )

4. Conjugation (piggy back by acid groups to speed up excretion)
Name 2 ways in which half life is lengthened.
1. bind reversibly to binding protein

2. protected by structure
What characteristics of a hormone receptor make it specific for one type of hormone?
Shape and chemical characteristics of each receptor site.

Specificity

Some hormones can bind to several different receptors that are similarly shaped, i.e. epinephrine.
Agonist
drug that binds to a hormone receptor and activates it (competes for the spot)
antagonist
drug that binds to a hormone receptor and inhibits its action for that hormone
What is down-regulation?

What are 2 mechanisms that cause this?
the number of receptors for a hormone decreases within target cells.

Eventually target cell becomes less sensitive to hormone.

1. rate at which receptors are synthesized decreases in some cells after the cells are exposed to a hormone.

2. combination of hormones and receptors can increase the rate at which receptor molecules are degraded. (receptor cells get gobbled up by endocytosis)
What is up-regulation?

Give an example.
occurs when some stinulus causes the number of receptors for a hormone to increase within a target cell

FSH acts on cells of the ovary to up-regulate the number of receptors for LH. Thus the ovary becomes more sensitive to the effect of LH.
Name the 2 classes of receptors hormones can bind to.
1. Bind to membrane-bound receptors

2. bind to intracellular receptors
What types of hormones bind to membrane bound receptors?
1. proteins

2. glycoproteins

3. polypeptides

4. smaller molecules such as epinephrine and norepinephrine
What type of hormones bind with intracellular receptors?
lipid soluable and small

1. thyroid hormones

2. steroid hormones
--testosterone
--estrogen
--progesterone
--aldosterone
--cortisol
Describe the process of a hormone that binds to a membrane-bound receptor and activates G proteins
1. Hormone binds. Alters the receptor. GTP replaces GDP

2. G protein separates. G subunit separates from y and B.

3. hormone separates from receptor. Phosphate is removed from G subunit making it GDP

4. all 3 subunits recombine
What is GDP? Is it active or inactive
guanine diphosphate

It is inactive when it is bound to alpha subunit
How does a membrane-bound hormone effect changes on the inside of the cell?
Activates intracellular mediators (Ca2+)
or
alter activity of enzymes inside the cell
Hormone causes G protien to bind to receptor and then releases the a subunit to an active state. a subunit can alter activity of molecules within plasma membrane and produce cellular responses.
Describe the process of G proteins and Ca2+ Channels.
1. hormone binds to membrane receptor,
receptor binds to G protein, releases alpha subunit

2. the GTP-alpha unit binds to Ca2+ channel causing it to open. Ca2+ binds to Calmodulin

3. Phosphate is removed from Gprotein making it GDP-alpha, separates from Ca2+ channel so it closes

4. Alpha, beta and gamma are one happy family again.
cGMP
Cyclic guanine monophosphate

kidney cells

increases Na+ and water excretion by the kidney
cAMP
Cyclic adenosine monophosphate

Liver Cells

Increases the breakdown of glycogen and the release of glucose into the circulatory system
Ca2+
Calcium Ions

Smooth Muscle Cells

Contraction of smooth muscles
IP3
Inositol triphosphate

Smooth Muscle Cells

Contraction of certain smooth muscle cells in response to epinephrine
DAG
Diaclyglycerol

Smooth Muscle Cells

Contraction of certain smooth muscle cells in response to epinephrine
NO
Nitric Oxide

Smooth muscle cells

Relaxation of smooth muscle cells of blood vessels, resulting in vasodilation
Insulin
Pancreatic islets

most cells; increases glucose and amino acid uptake
Growth Hormone
Anterior Pituitary Gland

Most cells; increases protein synthesis and resists protein breakdown
Prolactin
anterior pituitary gland

mammary glands and ovary; initiates milk production following pregnancy
Growth Factors
Various tissues

stimulate growth in certain types of cells
Some intracellular immune signal cells
Cells of the Immune System

Immune-competent cells; help mediate responses of the immune system
Atrial nutriuretic hormone
cells of kidney tubules

Increase na+ excretion by kidney tubule cells and increases urine volume
Membrane Bound Receptors that Activate G protein and Increase the synthesis of cAMP
1. G protein is activated (binds to receptor then breaks off from subunits)

2. activated GTP-alpha binds to adenylate cyclase enzyme so that it converts ATP to cAMP

3. cAMP activates protein kinase enzymes, which phosphorylate specific enzymes that break down glycogen to glucose and the glucose is released from the liver cells

4. Phosphodiesterase enzymes inactivate cAMP by converting it to AMP
Membrane Bound Receptors that Activate G proteins and Increase the Synthesis of IP3 and DAG
1. Epi binds to smooth muscle plasma membrane

2. G protein is activated, binds to phospholipase C and PIP2 which produces IP3 and DAG

3. IP3 releases Ca2+ from endoplasmic reticulum or opens Ca2+ channels in membrane. Ca ions regulate enzyme activity

4. DAG regulates enzymes like the ones that produce prostaglandin.

Increases smooth muscle contraction
Membrane Bound Receptor that directly activates an intracellular Mediator
1. Atrial natriuretic hormone binds with its receptor

2. inner surface of plasma membrane, guanylate cyclase is activated to produce cGMP from GTP

3. Cyclic GMP is an intracellular mediator that mediates the response of the cell.

4. Phosphodiesterase is an enzyme that converts cGMP to inactive GMP.
What binds to membrane bound receptors?
Water soluable hormones

proteins
glycoproteins
polypeptides,
epi
norepi
What binds to intracellular receptors?
Lipid soluable hormones

thyroid
steroids: testosterone, estrogen, progesterone, aldosterone, cortisol
What are the 2 main mechanisms in membrane bound receptors that create change in the cell?
1. hormone binds to membrane activating G proteins on inner surface of the membrane

2. This changes the enzyme activiity within the cell (2nd messenger mechanism)
What can happen when G proteins are activated?
1. opens ion channels (for Ca2+)

2. Alter enzyme activity:
Increase rate of cAMP formation
Protein Kinases
What is cAMP?
an intracellular mediator molecule

activates protein kinases and thus phosphorylation.
What is protein kinases?
enzymes that regulate the activity of other enzymes by attaching phosphates to them (phosphorylation)
Luteinizing hormone

Type of receptor and action?
source:
anterior pituitary

Target:
ovary or testis

Membrane bound and activate G Proteins
FSH

Type of receptor and action?
source:
anterior pituitary

Target:
ovary or testis

membrane bound activates G proteins
Prolactin

Type of receptor and action?
source:
anterior pituitary

Target:
mammary gland and ovary or testis

membrane bound activates G proteins
TSH

Type of receptor and action?
source:
anterior pituitary

Target:
thyroid gland

membrane bound activates g proteins
Adrenocorticotropic hormone

Type of receptor and action?
source:
anterior pituitary

Target:
adrenal cortex

membrane bound, activates g proteins
Oxytocin

Type of receptor and action?
Source:
Posterior Pituitary

Target:
Uterus

membrane bound activates g proteins
Vasopressin

Type of receptor and action?
Source:
Posterior Pituitary

Target:
Kidney

membrane bound and activates g proteins
Calcitonin

Type of receptor and action?
Source:
Thyroid Gland

Target:
Bone

membrane bound and activates g proteins
Parathyroid Hormone

Type of receptor and action?
Source:
Parathyroid gland

Target
Bone

membrane bound and activates g proteins
Glucagon

Type of receptor and action?
Source:
Pancreas

Target:
Liver

membrane bound and activates g proteins
Epinephrine

Type of receptor and action?
Source:
Medulla of Adrenal Gland

Target:
Cardiac muscle

membrane bound and activates g proteins
cGMP
example of cell type and response
Intracellular mediator
cyclic guanine monophosphate

Kidney cells

Increases Na+ and water excretion by the kidney
cAMP
example of cell type and response
Intracellular mediator
cyclic adenosine monophosphate

Liver cells

Increases the breakdown of glycogen and the release of glucose into the circulatory system
Calcium ions (Ca2+)
example of cell type and response
Intracellular mediator

smooth muscle cells

Contraction of smooth muscle cells
What is the cascade effect?
takes place because the hormones that stimulate synthesis of an intracellular mediator molecule are reaction with already existing enzymes.

A few mediator molecules activate several enzymes which in turn activate several more and on and on.
Amplification
a few mediator molecules can control a lot of enzymes in a cell.
Where are the intracellular receptors located?
cytoplasm

or

nucleus
What takes place once a lipid soluable hormone has diffused into a cell?
hormone binds to a receptor to alter the activity of cell's enzymes

moves into nucleus and binds to DNA

mRNA is synthesized, coded for specific proteins

mRNA leaves nucleus and binds to ribosomes

specific proteins are synthesized
Which type of hormone receptor is better for quick response?
membrane bound
Which type of hormone receptor is better for longer response times?
intracellular
Testosterone
Intracellular Receptor

Source:
Testis

Target:
Development of reproductive structures and male secondary sex characteristics
Progesterone
Intracellular Receptor

Source:
Ovary

Target:
Increase size of cells lining the uterus
Estrogen
Intracellular Receptor

Source:
Ovary

Target:
Increased cell division in the lining of the uterus
Aldosterone
Intracellular Receptor

Source:
Adrenal cortex

Target:
Increased reabsorption of na+ and increased secretion of K+ in the kidney
Cortisol
Intracellular Receptor

Source:
adrenal cortex

Target:
Increased breakdown of proteins and fats and increased blood levels of glucose
T3
Intracellular Receptor

Source:
Thyroid gland

Target:
Regulation of development and metabolism
Vitamin D
Intracellular Receptor

Source:
skin, liver and kidney

Target:
Increased reabsorption of Ca2+ in the kidney and absorption of Ca2+ in the gastrointestinal tract
Steroids are made from what?
Cholesterol
Describe the positive feedback cycle
Menstrual cycle:

1. before ovulation, small amounts of estrogen are secreted from the ovary

2. estrogen stimulates release of gonadotropin-releasing hormone (GnRH) from the hypothalamus and luteininzing hormone (LH) from the anterior pituitary

3. GnRH also stimulates the release of LH from the anterior pituitary

4. LH causes the release of adiditional estrogen from the ovary. The GnRH and LH levles in the blood increase because of this positive feedback
Describe a negative feedback cycle
Menstrual cycle:

1. after ovulation, the ovary begins to secrete progesterone in response to LH

2. Progesterone inhibits the release of GnRH from the hypothalamus and LH from the anterior pituitary

3. Decreased GnRH release from the hypothalamus reduces LH secretion from the anterior pituitary. GnRH, LH and estrogen levels in the blood decrease because of this negative feedback effect.
TSH is inhibited by
negative feedback from T3 and T4
What means shorten the half-life of a hormone?
1. excretion

2. metabolism

3.active transport

4. conjugation
What is conjugation?
substances like sulfate or glucuronic acid groups are attached to hormones primarily in the liver, normally making them less active as hormones and increasing the rate at which they are excreted in the urine or bile.
What means lengthen the half life of a hormone?
1. binding reversibly with binding proteins in the plasma

2. structure like carbohydrate glycoprotein hormones are protected from proteolytic enzymes in circulatory system
What type of hormone (water or lipid soluable) will have a longer half life?
lipid soluable because they bind to proteins and are protected or prevented from diffusing through blood vessel walls
neurohormone
chemical signals that are produced by neurons and act like hormones
amino acid derivatives
Eat No tacos, Man!

Epinephrine
Norepi
Thyroid (T3 and T4)
Melatonin
proteins
Grow Peanuts Instead

Growth hormone
Prolactin
Insulin
Glycoproteins (protein and carb)
It's the carb's FLT.

FSH
LH
TSH
Polypeptides
Poodles Think Only About Cats Getting An Endless Time Making Happy Lives Somatostatin

Parathyroid
TRH
Oxytocin
ADH
Calcitonin
Glucagon
Adrenocorticotropic
Endorphins
Thymosin
MSH
Hypothalamic
Lipotropins
Somatostatin
Lipids
Steroids:
Men Target Every Prospect
Mineralocorticoids (aldosterone)
Testosterone
Estrogen
Progestins (progesterone)

Fatty Acid Derivitives:
Please Lose These Pounds
Prostaglandins
Thromboxanes
Prostacyclins
Leukotrienes