Chapter 16 Endocrine System: Both Lectures Flashcards
Define half-life in relation to circulating hormones.
amount of time to eliminate 50% of the hormone, depends on hormone’s structure and solubility
Compare and contrast the hormonal and neural controls of body functioning.
nervous - fast effects, short-duration responses b/c body clears them out quickly, APs and NTs, specific locations, short distance
endocrine - slow effects, long-duration responses, hormones, diffuse locations, long-distance
both - alter gene expression to regulate activity of cells somehow, i.e. Epinephrine and NE from adrenal medulla
Define onset in relation to circulating hormones.
how long it takes for a hormone to have an effect; affected by its solubility
Describe, in detail, the cyclic AMP second messenger system used by water-soluble hormones to exert effects on target tissues.
hormone doesn’t enter cell, stays on receptor until released, transmembrane receptor proteins have confirmational shape change → hormone molecule plus receptor = GPCR → receptor activates G protein, it kicks off molecule of GDP → opens binding site for GTP, G protein travels → activates other G proteins (amplifies effect) → finds target enzyme and activates it (called adenylate cyclase) → enzyme converts ATP to 2nd messenger called cAMP → cAMP’s concentration changes → acts as messenger to activate lots of protein kinases → phosphorylate target proteins → change activity of molecules like activate more enzymes, dump contents (degranulate), exocytosis, open ion channels to adjust RMP/plasma permeability
at every level of the process, the signals are amplified
one hormone can change a lot of metabolism inside cell
Identify three factors that influence a hormone’s effect on its target cell and explain the role of each.
blood level of hormone, number of receptors, affinity between receptor and hormone
amount of hormone can influence number of receptors
what does exocrine duct do?
ducts release the exocrine gland’s secretions into external environment (skin, mucous membrane)
Explain how up-regulation and down-regulation of hormone receptors and target tissues affects the activity of the hormone.
up-regulation is response to low hormone levels, means cells make more surface receptors
down-regulation is response to high hormone levels, means cells desensitize self by removing receptors - causes cell not to be as affected by hormone
List and locate the body’s major endocrine organs.
pituitary, pineal (melatonin), thyroid, adrenal glands, thymus (some endocrine tissue, secretes thymocin)
What determines whether a particular cell is able to respond to a given hormone?
the presence of a specific hormone receptor
tropic hormone
hormone that stimulates release of another hormone, usually released from anterior pituitary gland
three major types of stimuli that trigger hormone release from endocrine glands?
neural, hormonal, humoral
Differentiate water-soluble hormones and lipid-soluble hormones.
water-soluble: all amino acid-based hormones except thyroid hormones, packaged into secretory vesicles and released via exocytosis, make way to bloodstream, find target cells w/surface receptors (extracellular),
lipid-soluble: all steroid hormones plus thyroid hormones, use transport proteins to travel through bloodstream, diffuse through PM so don’t need surface receptors
both: effect gene expression (division, making proteins)
Which hormone type can diffuse across PMs?
steroid hormones, lipid-soluble (receptors are inside cytosol)
Describe, in detail, the PIP2-calcium second messenger systems used by water-soluble hormones to exert effects on target tissues.
hormone → surface receptor → activate G protein → G protein moves around → activates more → find target enzyme → enzyme binds PIP2 → cut into two 2nd messenger molecules called DAG and IP3 → DAG stays in PM and travels there, IP3 acts as second messenger in cytosol → open calcium channels on ER to allow Ca2+ into cytosol → lots of effects including exocytosis of other hormones, activate different enzymes, and more cellular responses
2 names because 2 second messengers (PIP2 & Calcium)
classic example of down regulation
insulin resistance that leads to diabetes type II
Define duration in relation to circulating hormones.
how long hormone’s action lasts; ranges from 10 seconds to many hours,
GPCR
hormone molecule plus receptor = GPCR
G-PROTEIN COUPLED RECEPTOR
Explain the regulation of hormone release (three stimuli).
negative feedback loops - target cells’ effects feed back on original gland to decrease
1 humoral - stimuli = changing levels of ions in blood, simplest type, i.e. parathyroid gland cells monitor Ca2+ and release PTH as needed
2 neural - stimuli = nerve fibers, classic example is response to stress: SNS stim. adrenal medulla to release NE and E
3 hormonal - stimuli = hormone release caused by another hormone (tropic hormone), i.e. hypothalamic-pituitary-target endocrine organ feedback loop
Water-soluble hormones affect target cells by binding to
plasma membrane receptors
classic example of neural stimulus
APs in preganglionic sympathetic fibers to adrenal medulla leads to adrenal medulla cells releasing E and NE
Differentiate hormones, paracrines, and autocrines.
hormones - systemically released and acts at any tissues that have the corresponding receptor and responses can have longer-term effects
paracrines - released locally into interstitial fluid and travel to neighboring cells
autocrines - released locally into IF and travel to self
lots of overlap between autocrines and paracrines because molecules can bind to self and also neighboring cells
All amino-acid-based hormones except ___ use a second messenger system to alter a target cell’s gene expression and metabolism.
thyroid hormones
SG: Which of the following is NOT a steroid hormone?
m. Testosterone
n. Cortisol
o. Gonadotropin Releasing Hormone
p. Aldosterone
gonadotropin releasing hormone
exocrine gland examples
salivary glands, pancreas, lacrimal, mammary, digestive glands
list water-soluble hormones
glycoproteins, catecholamines, TSH, FSH, luteinizing hormone, insulin
list fat-soluble hormones
all steroids plus thyroid hormone, sex hormones including estrogen, progesterone, testosterone; cortisol, aldosterone
classic example of hormonal stimulus
hormones from hypothalamus stimulate anterior pituitary gland to secrete hormones that stimulate other endocrine glands (thyroid gland, adrenal cortex, testis) to secrete hormones
classic example of humoral stimulus
low concentration of Ca2+ in capillary blood leads to parathyroid glands secreting PTH which increases blood Ca2+
SG: Which of the following has both endocrine and exocrine function?
i. Pineal Gland
j. Thyroid Gland
k. Adrenal Medulla
l. Pancreas
pancreas
Differentiate amino-acid-based hormones and steroid hormones.
amino-acid-based hormones - protein hormones, can’t diffuse through PM,
steroid hormones - synthesized from cholesterol (fat), diffuse through plasma membrane
both - circulate systemically, access to lots of cells but only act on target cells
Differentiate endocrine glands and exocrine glands (including ducts)
exocrine have duct to release secretions into external environment;
endocrine have no ducts, release hormones into blood plasma instead
SG: Which of the following is a neuroendocrine organ?
e. Adrenal Cortex
f. Thyroid Gland
g. Gonads
h. Hypothalamus
hypothalamus
Describe the general mechanism used by lipid-soluble hormones to exert effects on target tissues.
don’t need surface receptors → binds to receptor inside cell and forms complex b/w self and receptor → complex goes into nucleus → alters expression in DNA to make new proteins or silence genes → change activity of cell
list organs that have partial endocrine function
pancreas (pancreatic islets-glucagon, insulin), gonads (ovaries/testes) produce hormones, placenta (hormones), adipose tissue (leptin), stomach (gastrin), intestine (CCK & secretin), kidneys (EPO), heart (ANP)
