Flashcards in Chapter 5 - Endocrine System Deck (79)
What can diabetes lead to if not controlled?
What is it that hormones do?
They bind to receptions in the target tissue, inducing a change in gene expression or cellular functioning.
3 classifications of hormones by CHEMICAL structure
1. Peptide hormones
2. Steroid hormones
3. Amino-Acid Derivative hormones
What are peptide hormones made from?
Derived from larger polypeptides that are cleaved during post translational modification.
They are made up of amino acids
How does a cell make peptide hormones?
Polypeptides are broken down
Smaller units go to the Golgi apparatus for modifications that ACTIVATE the hormone
Packages into vesicles and sent out of the cell via exocytosis
Can peptide hormones pass through the cell membrane?
Why / why not?
What are first / second messengers?
NO because they are charged.
They must hence bind to an exta cellular receptor. (Often a g-protein coupled receptor)
First messenger is the hormone - second messenger is within the cell. This is known as signaling cascade.
Examples of common second messengers?
Cyclic adenosine monophasphate (cAMP) -- am regulated by enzyme called adenylate cyclase
Inositol triphosphate (IP3)
Characteristics of peptide hormones:
Need carrier in bloodstream?
Fast response but short-lived (require constant stimulation of second messengers to continue the response)
Do not need a carrier in the bloodstream
What are steroid hormones made from?
Produced primarily by the gonads and adrenal cortex
Can steroid hormones pass through the cell membrane?
Why / why not?
Yes - because they are nonpolar
They don't require an extra cellular receptor (receptor is intercellular, in cytosol or in the nucleus)
How does a steroid hormone communicate with target cell/tissue?
Binds to receptor inside the cell
Steroid hormone-receptor complex undergoes CONFORMATIONAL CHANGES
Receptor can then bind directly to DNA
Increases or decreases transcription of particular genes
Characteristics of steroid hormones:
Carrier in bloodstream?
Slow acting but long-lasting (because they cause alterations in the amount of mRNA and protein present in the cell)
Carried by proteins in the blood stream
Common carriers of steroid hormones:
Sex-hormone-binding globulin (specific)
Thyroxine-binding globulin (TBG)
What are amino-acid derivative hormones made from?
Made from one or two amino acids, usually with additional modifications
Eg: thyroid hormones are made from tyrosine with the additional of iodine atoms
What are common examples of amino-acid derivative hormones:
Long or short duration? Fast or slow?
First two: think "adrenaline rush" fast onset but short lived
Last two: slow onset and longer duration (regulate metabolic rate over a long period of time)
What are catecholamines?
What do they bind to?
Epinephrine and norepinephrine
Bind to g-protein-couples receptors (like peptide hormones)
What do thyroid hormones bind to?
They bind intracellularly, like steroid hormones
Direct versus Tropic hormones?
Act directly on target tissue
Requires an intermediary
Usually originate in the brain and anterior pituitary gland
Eg: GnRH (gonadotropin-releasing hormone) and LH do not cause direct changes; they stimulate the production of another hormone by another endocrine gland.
What is the purpose of the endocrine system?
To use hormones and messengers to create changes in behavior and physiology to maintain homeostasis
High blood glucose can cause damage to which organs:
Retina of the eye (blindness)
Glomeruli of the kidneys (kidney failure)
Coronary vessels of the heart (heart attack)
Cerebral vessels of the brain (stroke)
Nerve damage in extremities (amputation)
Why are thyroid hormone levels higher in pregnant women?
Because high levels of estrogen and progesterone increase the production of TBG (thyroxine-binding globulin). Secretion of thyroid hormones is increased to compensate.
This is an example of a change in level of carrier protein (globulin increase) which sides a change in the level of the active hormone.
What systems does the hypothalamus connect?
What other endocrine gland(s) does it interact with? (2)
What else does the hypothalamus regulate? (2)
Connect nervous and endocrine systems. Located in the forebrain
Responds to increases in blood osmolarity, and regulated appetite/satiety
What is the suprachiasmatic nucleus?
A part of the hypothalamus
Received light input from the retinas, helps control sleep-wake cycles
What is the hypophyseal portal system?
A blood vessel system that directly connects the anterior pituitary and the hypothalamus.
Which hormones produced by the hypothalamus cause a response in secretions from the ANTERIOR PITUITARY? (5)
1. GnRH - gonadotropin releasing hormone.
2. GHRH - growth hormone releasing hormone (ALSO somatostatin, also affects GH)
3. TRH - thyroid releasing hormone
4. CRF - Corticotropin-releasing factor
5. Dopamine aka PIF - prolactin inhibiting factor (this is the only one that causes a decrease in secretion from the pituitary)
What is an "axis" or three-organ system?
When the organs have receptors (ie cortisol receptors) to detect when high levels of cortisol in the blood have been obtained - cortisol can then inhibit the hypothalamus and Ant Pit from producing more hormones stimulating cortisol.
This is the Hypothalamic-pituitary-adrenal (HPA) axis
There is also the hypothalamic-pituitary-ovarian (HPO) axis, etc
How does the hypothalamus interact with the posterior pituitary?
What (2) hormones are release from the posterior pituitary (produced in the hypothalamus)?
Neurons in the hypothalamus send their axons down the pituitary stalk directly to the posterior pituitary.
2. Antidiuretic hormone (ADH) aka Vasopressin
What is osmolarity?
Increased concentration of SOLUTES in the blood
Hormones secreted by the Anterior pituitary?
Adenocoeticotropic hormone ACTH
Thyroid stimulating hormone TSH
FLAT are Tropic hormones
PEG are direct hormones