BMS 108 Ch. 11 Endocrine System Flashcards
This flashcard deck was created using Flashcardlet's card creator
What is a priming effect (upregulation)?
A hormone that induces more of its own receptors in the target cells, increasing response.
What kind of effect do hormones generally have?
metabolic effects
What is desensitization (downregulation)?
Decreased number of receptors or receptors become less responsive because of prolonged exposure.
What are the three chemical categories of hormones?
- Peptide hormones
- Steroid hormones
- Amines
Describe peptide hormones.
- chain of amino acids
- lipophobic = hydrophilic
- receptors are on cell surface
- e.g. ADH, insulin, glucagon
Describe steroid hormones.
- derived from cholesterol
- lipophilic = hydrophobic
- receptors in cytoplasm or nucleus
- e.g. estrogen, testosterone, aldosterone
Describe amines.
- derived from amino acids; small
- can be either lipophilic or lipophobic
- e.g. thyroid hormone (lipophilic); epinephrine (lipophobic)
Target cell receptors show _________ and _______ affinity for a hormone.
specificity; high
Almost ______ hormones use 2nd messenger systems.
all
Where do lipophilic hormones bind to their receptors?f
nucleus
Where do hydophilic hormones bind?
plasma membrane
How do lipophilic hormones travel in the bloodstream?
via carrier proteins (albumin)
Describe lipophic hormone action.
- lipid hormones travel in blood attached to carrier protein.
- They dissociate from carriers to pass thru plasma membrane of target
- Receptors are called nuclear hormone receptors
- Serve as transcription factors when bound to hormone ligands
- Activate transcription
What are the three major 2nd messenger systems used by hormones?
- Adenylate cyclase - cAMP
- Phospholipase C - calcium
- Tyrosine kinase
2nd messenger systems are examples of ________ _________.
signal transduction
Describe the steps involved in the Adenylate cyclase - cAMP system.
- Hydrophilic hormone binds to a receptor protein
- A subunit of the G protein dissociates and activates Adenylate cyclase (AC)
- AC converts ATP to cAMP & 2PP
- cAMP attaches to the inhibitory subunit of the protein kinase
- Releases kinases to phosphoylate things
- This increases the activity of some enzymes and decreases others
- cAMP is inactivated by phosphodiestrase
What type of receptor does adenylate cyclase - cAMP get activated by?
b-adrenergic receptors
Describe the steps involved in the Phospholipase C - calcium system.
- Hydrophilic hormone binds to receptor protein
- subunit of G protein dissociates and activates phospholipase C (PC)
- PC splits into 2nd messengers DAG and IP3
- IP3 causes Ca++ channels on smooth ER to open
- Ca++ activates calmodulin leading to activation of “other things”
What type of receptor is phospholipase c - calcium activated by?
alpha adrenergic receptors
What second messenger system is used by insulin? Where is insulin secreted?
Tyrosine kinase; pancreas
What does tyrosine kinasse cause in cells?
Tyrosine kinase phosphoylation signals molecules that induce hormone/growth factor effects
Describe the steps involved in the tyrosine kinase 2nd messenger system.
- hormone binds to extracellular receptor portion of tyronsine kinase (TK)
- TK dimers (2 halves) come together
- TK is phosphoylated
- Intracellular portion is now an active enzyme
- TK produces cellular effects (e.g. inerting GLUT4 carrier protein)
How does insulin stimulate glucose uptake?
by means of GLUT4 carrier proteins being inserted in the plasma membrane of the target cell
What type of tissue is the anterior pituitary gland? posterior?
epithelial tissue; nervous tissue
How does the hypothalamus control the anterior pituitary?
via a portal vein system
The anterior pituitary secretes ____ hormones that specialize in ______ effects.
6; tropic
What do tropic hormones do?
tell target to release other hormones and maintain the size of target cells
What is a portal vein system?
2 capillary beds with a vein in between them; used for shunting
What are the 6 tropic hormones released by the anterior pituitary?
- Growth hormone
- Thyroid stimulating hormone (TSH)
- Adrenocorticotropic hormone (ACTH)
- Follicle stimulating hormone (FSH)
- Lutenizing hormone (LH)
- Prolactin
What is neurotransmitter that is released into the capillary bed called?
neurohormones
The posterior pituitary gland is made of _________ tissue that stores and releases two hormones made in the hypothalamus. What are those two hormones?
nervous; Antidiuretic hormone (ADH) and Oxytocin
What is the function of ADH? Oxytocin?
H2O conservation in the kidneys; stimulates contractions of uterus during childbirth (and cuddling)
What does the Adrenal medulla synthesize and secrete?
Epinephrine (80%) and Norepinephrine (20%)
What does the Adrenal cortex synthesize and secrete? What controls the adrenal cortex?
Cortisol and Aldosterone; controlled by ACTH secreted by the anterior pituitary
What is the function of cortisol?
inhibits glucose utilization and stimulates gluconeogenesis
What is the function of aldosterone?
stimulates kidneys to reabsorb Na+ and secrete K+
What is the main precusor of all adrenal hormones?
cholesterol
What is the primary function of the thyroid gland?
sets your Basal Metabolic Rate (BMR)
The Thyroid Gland is a true _______ organ.
endocrine
What does the thyroid gland secrete and what is it used for?
T3 and T4 which set BMR and are needed for growth and development
What cells does the thyroid consist of?
Thyroid follicle cells
What is a thyroid follicle cell?
An outer layer of follicle cells that synthesize T4 and an interior filled with colloid, a protein rich fluid
How is thyroid hormone produced?
- Iodide (I-) is transported into the colloid
- where it is oxidized into Iodine (I2) and attached to thyroglobulin (a large storage molecule for T4 & T3)
- TSH stimulates hydrolysis of T4 and T3 from thyroglobulin and secretion
Does thyroid hormone need a carrier protein to be transported?
yes
What percentage of thyroid hormone secretion is T4 (thyroxane)? T3 (active form)?
90%;10%
What percentage of T4 in blood is bound to carrier proteins? why?
99.9%; to serve as a reservoir
Where is T4 converted into T3?
within target cell
Where are T3 receptors located in the target cell?
nucleus
What is goiter? What is the mechanism by which it is caused?
A swelling of the thyroid caused by inadequate iodide levels in the diet.
Without sufficient iodide, T4 and T3 cannot be produced and levels are low. This doesn’t provide enough negative feedback and TSH levels go up. TSH is a tropic hormone so the thyroid gland grows, resulting in goiter.
