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97 Cards in this Set
- Front
- Back
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Endocrine gland
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secrete chemical signals that influence tissues that are separate from the glands by some distance
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Endocrine system
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composed of glands that typically secrete chemical signals into the circulatory sytem
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hormone
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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 |
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compare and contrast the nervous system vs. the endocrine system
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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. |
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Name 5 categories of intercellular chemical signals (not hormones)
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1. Autocrine
2. Paracrine 3. Pheromones 4. Neurotransmitters 5. Neuromodulators |
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Autocrine chemical signals
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1. released by cells
2. have local effect on same cell type as 'releaser' |
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Paracrine chemical signals
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1. released by cells
2. affect other cells locally without going into bloodstream |
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Pheromones
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1. secreted into the environment
2. modify the behavior of other individuals of the same species. |
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Neuromodulator
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Substance that influences the sensitivity of neurons to neurotransmitters but neither strongly stimulates nor strongly inhibits neurons by itself
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List 3 categories of hormones and their subcategories (based on chemical structure)
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1. proteins / polypeptides
2. derivitives of amino acids 3. lipids |
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What are the 3 major patterns by which hormone secretion is regulated?
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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. |
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Is hormone regulation generally negative or positive feedback?
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Negative Feedback
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Chronic Hormone Regulation
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A relatively constant concentration of hormone is maintained in the circulating blood over a relatively long period.
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Acute Hormone Regulation
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A hormone rapidly increases in the blood for a short time in response to a stimulus.
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Cyclic Hormone Regulation
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A hormone is regluated so that it increases and decreases in the blood at a relatively constant time and to roughly the same amount.
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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. |
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Why does the wall of capillaries or organs regulated by protein hormones have large pores?
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they are bigger and take a longer time to pass through, unlike lipid soluable hormones which readily pass through the capillary walls.
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Fenestrae
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large pores in capillary walls
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half-life
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lenght of time it takes for half a dose of a substance to be eliminated fromt eh circluatory system
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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 |
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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 |
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Name 4 ways half life of hormone is shortened.
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1. Excretion
2. Metabolism (enzymes degrade in blood) 3. Active Transport (recycled ) 4. Conjugation (piggy back by acid groups to speed up excretion) |
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Name 2 ways in which half life is lengthened.
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1. bind reversibly to binding protein
2. protected by structure |
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What characteristics of a hormone receptor make it specific for one type of hormone?
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Shape and chemical characteristics of each receptor site.
Specificity Some hormones can bind to several different receptors that are similarly shaped, i.e. epinephrine. |
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Agonist
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drug that binds to a hormone receptor and activates it (competes for the spot)
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antagonist
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drug that binds to a hormone receptor and inhibits its action for that hormone
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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) |
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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. |
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Name the 2 classes of receptors hormones can bind to.
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1. Bind to membrane-bound receptors
2. bind to intracellular receptors |
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What types of hormones bind to membrane bound receptors?
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1. proteins
2. glycoproteins 3. polypeptides 4. smaller molecules such as epinephrine and norepinephrine |
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What type of hormones bind with intracellular receptors?
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lipid soluable and small
1. thyroid hormones 2. steroid hormones --testosterone --estrogen --progesterone --aldosterone --cortisol |
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Describe the process of a hormone that binds to a membrane-bound receptor and activates G proteins
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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 |
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What is GDP? Is it active or inactive
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guanine diphosphate
It is inactive when it is bound to alpha subunit |
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How does a membrane-bound hormone effect changes on the inside of the cell?
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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. |
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Describe the process of G proteins and Ca2+ Channels.
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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. |
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cGMP
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Cyclic guanine monophosphate
kidney cells increases Na+ and water excretion by the kidney |
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cAMP
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Cyclic adenosine monophosphate
Liver Cells Increases the breakdown of glycogen and the release of glucose into the circulatory system |
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Ca2+
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Calcium Ions
Smooth Muscle Cells Contraction of smooth muscles |
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IP3
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Inositol triphosphate
Smooth Muscle Cells Contraction of certain smooth muscle cells in response to epinephrine |
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DAG
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Diaclyglycerol
Smooth Muscle Cells Contraction of certain smooth muscle cells in response to epinephrine |
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NO
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Nitric Oxide
Smooth muscle cells Relaxation of smooth muscle cells of blood vessels, resulting in vasodilation |
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Insulin
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Pancreatic islets
most cells; increases glucose and amino acid uptake |
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Growth Hormone
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Anterior Pituitary Gland
Most cells; increases protein synthesis and resists protein breakdown |
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Prolactin
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anterior pituitary gland
mammary glands and ovary; initiates milk production following pregnancy |
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Growth Factors
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Various tissues
stimulate growth in certain types of cells |
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Some intracellular immune signal cells
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Cells of the Immune System
Immune-competent cells; help mediate responses of the immune system |
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Atrial nutriuretic hormone
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cells of kidney tubules
Increase na+ excretion by kidney tubule cells and increases urine volume |
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Membrane Bound Receptors that Activate G protein and Increase the synthesis of cAMP
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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 |
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Membrane Bound Receptors that Activate G proteins and Increase the Synthesis of IP3 and DAG
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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 |
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Membrane Bound Receptor that directly activates an intracellular Mediator
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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. |
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What binds to membrane bound receptors?
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Water soluable hormones
proteins glycoproteins polypeptides, epi norepi |
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What binds to intracellular receptors?
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Lipid soluable hormones
thyroid steroids: testosterone, estrogen, progesterone, aldosterone, cortisol |
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What are the 2 main mechanisms in membrane bound receptors that create change in the cell?
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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) |
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What can happen when G proteins are activated?
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1. opens ion channels (for Ca2+)
2. Alter enzyme activity: Increase rate of cAMP formation Protein Kinases |
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What is cAMP?
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an intracellular mediator molecule
activates protein kinases and thus phosphorylation. |
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What is protein kinases?
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enzymes that regulate the activity of other enzymes by attaching phosphates to them (phosphorylation)
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Luteinizing hormone
Type of receptor and action? |
source:
anterior pituitary Target: ovary or testis Membrane bound and activate G Proteins |
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FSH
Type of receptor and action? |
source:
anterior pituitary Target: ovary or testis membrane bound activates G proteins |
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Prolactin
Type of receptor and action? |
source:
anterior pituitary Target: mammary gland and ovary or testis membrane bound activates G proteins |
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TSH
Type of receptor and action? |
source:
anterior pituitary Target: thyroid gland membrane bound activates g proteins |
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Adrenocorticotropic hormone
Type of receptor and action? |
source:
anterior pituitary Target: adrenal cortex membrane bound, activates g proteins |
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Oxytocin
Type of receptor and action? |
Source:
Posterior Pituitary Target: Uterus membrane bound activates g proteins |
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Vasopressin
Type of receptor and action? |
Source:
Posterior Pituitary Target: Kidney membrane bound and activates g proteins |
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Calcitonin
Type of receptor and action? |
Source:
Thyroid Gland Target: Bone membrane bound and activates g proteins |
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Parathyroid Hormone
Type of receptor and action? |
Source:
Parathyroid gland Target Bone membrane bound and activates g proteins |
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Glucagon
Type of receptor and action? |
Source:
Pancreas Target: Liver membrane bound and activates g proteins |
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Epinephrine
Type of receptor and action? |
Source:
Medulla of Adrenal Gland Target: Cardiac muscle membrane bound and activates g proteins |
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cGMP
example of cell type and response |
Intracellular mediator
cyclic guanine monophosphate Kidney cells Increases Na+ and water excretion by the kidney |
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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 |
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Calcium ions (Ca2+)
example of cell type and response |
Intracellular mediator
smooth muscle cells Contraction of smooth muscle cells |
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What is the cascade effect?
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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. |
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Amplification
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a few mediator molecules can control a lot of enzymes in a cell.
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Where are the intracellular receptors located?
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cytoplasm
or nucleus |
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What takes place once a lipid soluable hormone has diffused into a cell?
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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 |
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Which type of hormone receptor is better for quick response?
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membrane bound
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Which type of hormone receptor is better for longer response times?
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intracellular
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Testosterone
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Intracellular Receptor
Source: Testis Target: Development of reproductive structures and male secondary sex characteristics |
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Progesterone
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Intracellular Receptor
Source: Ovary Target: Increase size of cells lining the uterus |
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Estrogen
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Intracellular Receptor
Source: Ovary Target: Increased cell division in the lining of the uterus |
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Aldosterone
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Intracellular Receptor
Source: Adrenal cortex Target: Increased reabsorption of na+ and increased secretion of K+ in the kidney |
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Cortisol
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Intracellular Receptor
Source: adrenal cortex Target: Increased breakdown of proteins and fats and increased blood levels of glucose |
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T3
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Intracellular Receptor
Source: Thyroid gland Target: Regulation of development and metabolism |
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Vitamin D
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Intracellular Receptor
Source: skin, liver and kidney Target: Increased reabsorption of Ca2+ in the kidney and absorption of Ca2+ in the gastrointestinal tract |
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Steroids are made from what?
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Cholesterol
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Describe the positive feedback cycle
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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 |
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Describe a negative feedback cycle
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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. |
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TSH is inhibited by
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negative feedback from T3 and T4
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What means shorten the half-life of a hormone?
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1. excretion
2. metabolism 3.active transport 4. conjugation |
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What is conjugation?
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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.
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What means lengthen the half life of a hormone?
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1. binding reversibly with binding proteins in the plasma
2. structure like carbohydrate glycoprotein hormones are protected from proteolytic enzymes in circulatory system |
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What type of hormone (water or lipid soluable) will have a longer half life?
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lipid soluable because they bind to proteins and are protected or prevented from diffusing through blood vessel walls
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neurohormone
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chemical signals that are produced by neurons and act like hormones
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amino acid derivatives
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Eat No tacos, Man!
Epinephrine Norepi Thyroid (T3 and T4) Melatonin |
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proteins
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Grow Peanuts Instead
Growth hormone Prolactin Insulin |
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Glycoproteins (protein and carb)
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It's the carb's FLT.
FSH LH TSH |
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Polypeptides
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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 |
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Lipids
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Steroids:
Men Target Every Prospect Mineralocorticoids (aldosterone) Testosterone Estrogen Progestins (progesterone) Fatty Acid Derivitives: Please Lose These Pounds Prostaglandins Thromboxanes Prostacyclins Leukotrienes |
