Endocrinology intro (Cell bio) Flashcards
The endocrine system – general concepts
The endocrine system has evolved to allow physiological processes to be coordinated and regulated.
The system uses ? messengers called ?
One of the important characteristics of the endocrine system is the ?
of the signal
One ? molecule can activate the formation of many messenger molecules, and each of these can induce the formation of many ? molecules (response)
recall:
endocrine: hormones
exocrine: digestive enzymes
The endocrine system – general concepts
The endocrine system has evolved to allow physiological processes to be coordinated and regulated.
The system uses chemical messengers called HORMONES
One of the important characteristics of the endocrine system is the amplification
of the signal
One hormone molecule can activate the formation of many messenger molecules, and each of these can induce the formation of many enzyme molecules (response)
recall:
endocrine: hormones
exocrine: digestive enzymes
ENDOCRINE SYSTEM
Definition:
Integrated network of ? and ? derived from different embryologic origins that release hormones (small ?, ?, ?). Hormones will signal ? or ? target cells
Coordinate and integrate cellular activity within the whole body:
Digestion
Reproduction
Electrolyte and fluid balance Energy balance
Fuel mobilization
Growth, development & senescence Response to injury
Mood
Stress (cortisol is not a bad hormone (but becomes bad when secreted a lot more than usual or at a higher frequency)
ENDOCRINE SYSTEM
Definition:
Integrated network of multiple glands and organs derived from different embryologic origins that release hormones (small peptides, glycoproteins, lipid derived). Hormones will signal neighboring or distant target cells
Coordinate and integrate cellular activity within the whole body:
Digestion
Reproduction
Electrolyte and fluid balance Energy balance
Fuel mobilization
Growth, development & senescence Response to injury
Mood
Stress (cortisol is not a bad hormone (but becomes bad when secreted a lot more than usual or at a higher frequency)
note:
glycoprotein: glycan (Carb.)attached to protein
lipid-derived: meaning cholesterol
WHAT CONTROLS THE ENDOCRINE SYSTEM
Endocrine system function is controlled by:
-> Secretion of hormones into the ? system to be transported towards ? ? organs (long-distance effect, i.e., pancreatic and thyroid hormones)
-> Hormones produced and acting ? (i.e., immune cells local/regional response)
-> Direct ? stimulation (i.e., hypothalamus)
WHAT CONTROLS THE ENDOCRINE SYSTEM
Endocrine system function is controlled by:
-> Secretion of hormones into the circulatory system to be transported toward distant target organs (long-distance effect, i.e., pancreatic and thyroid hormones)
-> Hormones produced and acting locally (i.e., immune cells local/regional response)
-> Direct neuroendocrine stimulation (i.e., hypothalamus)
ENDOCRINE SYSTEM
THE ENDOCRINE SYSTEM
Works closely with ? & ? System
Neuroendocrine -> ? nervous & ? systems
3 core components of the endocrine system
? glands
?
? organ
ENDOCRINE SYSTEM
THE ENDOCRINE SYSTEM
Works closely with CNS/PNS & Immune System
Neuroendocrine -> integrated nervous & endocrine systems
3 core components of the endocrine system
endocrine glands
hormones
target organ
CLASSICAL ENDOCRINE GLANDS
hypothalamus
pineal
parathyroid
adrenal glands
ovaries
testicles
pancreas
thyroid
pituitary gland
NON-CLASSICAL ENDOCRINE GLANDS (main function is not to produce hormones but produces hormones as a secondary thing)
HEART: Atrial Natriuretic Peptide
INTESTINES:
Cholecystokinin
Gastrin
Gastric Inhibitor peptide Secretin
Vasoactive Intestinal peptide Somatostatin
Motilin
Neurotensin
KIDNEY
1,25- Dihydroxicholecalciferol (name of active vitamin D)
Erythropoietin (stimulates production of RBCs)
PLACENTA
Gonadotropin
Estrogens
Progestin
Androgens
Inhibin
Relaxin
ADIPOSE TISSUE
Leptin
Adiponectin
Resistin
HORMONES - DEFINITION
Chemicals produced at ? concentrations by ?, transported by the vascular system affecting other tissues (target cell/tissue)
Hormones can be synthesized and released from:
* ? endocrine tissue/gland
* ? endocrine tissue/glands, brain, and other organs.
Can act:
* ?
* ? target cell
Some ? molecules can also act as hormones
i.e., some neurotransmitters such as dopamine can be considered hormones when secreted by the ?
HORMONES - DEFINITION
Chemicals produced at low concentrations by specific tissues/glands, transported by the vascular system affecting other tissues (target cell/tissue)
Hormones can be synthesized and released from:
* classical endocrine tissue/gland
* non-classical endocrine tissue/glands, brain, and other organs.
Can act:
* locally
* distant target cell
Some signalling molecules can also act as hormones
i.e., some neurotransmitters such as dopamine can be considered hormones when secreted by the hypothalamus
CHEMICAL MESSENGER CLASSIFICATION
- Neurotransmitters
* Affect communication between neurons, or between neurons and ? cells; the signals are ? in the distance traveled and the area of the cell influenced (synaptic cleft, neuromuscular junction…)
I.e., Acetylcholine, ? - Cytokines
* Are ? secreted by cells into the extracellular fluid (ECF) and can function as ?, paracrine or ? signal molecules; ? agents
-> Ex: Interleukins are released from T helper cells and act on other ? cells
-> Leptin is a ? produced by ? (participate in inflammatory responses)
peptides (shorter chain length) and protein diff. in terms of their size
- Neuroendocrine hormones
* Are secreted into the vascular system by ? tissues due to ? stimulation
* Influence function of ? cells at another location in the body
o I.e., ?, Epinephrine (synthesized by hypothalamus) - Endocrine hormones
* Are synthesized and released by ? or specialized cells into the vascular system
* Influence the function of target cells at another location in the body
o I.e., ? - ? cell of the Pancreas,
o I.e., ? - ? Cortex of the Adrenal Gland
CHEMICAL MESSENGER CLASSIFICATION
- Neurotransmitters
* Affect communication between neurons, or between neurons and target cells; the signals are limited in the distance traveled and the area of the cell influenced (synaptic cleft, neuromuscular junction…)
I.e., Acetylcholine, dopamine - Cytokines
* Are peptides secreted by cells into the extracellular fluid (ECF) and can function as autocrine, paracrine or endocrine signal molecules; immunomodulating agents
-> Ex: Interleukins are released from T helper cells and act on other immune cells
-> Leptin is a cytokine produced by adipocytes (participate in inflammatory responses)
peptides (shorter chain length) and protein diff. in terms of their size
- Neuroendocrine hormones
* Are secreted into the vascular system by endocrine tissues due to neuronal stimulation
* Influence function of target cells at another location in the body
o I.e., ADH (aquaporin), Epinephrine (synthesized by the hypothalamus) - Endocrine hormones
* Are synthesized and released by glands or specialized cells into the vascular system
* Influence the function of target cells at another location in the body
o I.e., insulin - beta cell of the Pancreas,
o I.e., cortisol - adrenal Cortex of the Adrenal Gland
- Paracrine hormones
* Are secreted by cells into the ? and affect ? target cells of a different type
o ? growth factor - Autocrine hormones
* Are secreted by cells into the ? and affect the function of the ? cells that produce them
o Ex: IL-6 in cancer cells; IL-1 in monocytes
- Paracrine hormones
* Are secreted by cells into the ECF and affect neighbouring target cells of a different type
o fibroblast growth factor - Autocrine hormones
* Are secreted by cells into the ECF and affect the function of the same cells that produce them
o Ex: IL-6 in cancer cells; IL-1 in monocytes
CHEMICAL STRUCTURE OF HORMONES
- PROTEIN and PEPTIDE HORMONES
- Comprises the ? of hormones
o ?, ACTH, PTH, CCK
o LH, FSH and TSH (glycoproteins) - Usually ? as an inactive larger molecule in the ER and Golgi apparatus
-> Then packaged into ? granules awaiting for ? and secretion
PRE-PROHORMONE → PROHORMONE → HORMONE (recall: proteolytic cleavage needed to activate zymogens which inactivated protein)
- PROTEIN AND PEPTIDE HORMONES
Circulate bound or unbound? in the blood
As an ? molecule or as an
active/? fragment
HYDROPHILIC or HYDROPHIC?
Mostly short ? (at most 30 minutes)
Bind to ? in the cell membrane
-> Hormone-receptor complex activate signal ? (i.e., GPCRs, RTK)
- PROTEIN and PEPTIDE HORMONES
- Comprises the majority of hormones
o insulin, ACTH, PTH, CCK
o LH, FSH and TSH (glycoproteins) - Usually synthesized as an inactive larger molecule in the ER and Golgi apparatus
-> Then packaged into secretory granules awaiting for activation and secretion
PRE-PROHORMONE → PROHORMONE → HORMONE (recall: proteolytic cleavage needed to activate zymogens which inactivated protein)
- PROTEIN AND PEPTIDE HORMONES
Circulate unbound in the blood
As an intact molecule or as an
active/inactive fragment
HYDROPHILIC
Mostly short half-life (at most 30 minutes)
Bind to receptors in the cell membrane
-> Hormone-receptor complex activate signal transduction (i.e., GPCRs, RTK)
bind to receptors as proteins and peptide hormones are HYDROPHILLIC so can’t cross the hydrophobic membranes but can circulate unbound in blood tho!
CHEMICAL STRUCTURE OF HORMONES
- AMINES (hormones derived from the modification of amino acids)
Derived from the amino acid * ? *
Ex: T3, T4 (thyroid hormones), ? (dopamine, NE, Epinephrine)
-> HYDROPHILIC (except thyroid hormones = hydrophobic)
Circulate unbound in the blood
Except Thyroid hormones → require
carrier proteins.
-> ?-binding globulin (TBG) &
? are both carrier proteins
produced by the liver
Half-life depends on the hormone
o Thyroxine = 7-10 ?
o Epinephrine = 1 ?
Bind to cell membrane ? or ? receptors
CHEMICAL STRUCTURE OF HORMONES
- AMINES (hormones derived from the modification of amino acids)
Derived from the amino acid * TYROSINE *
Ex: T3, T4 (thyroid hormones), CATECHOLAMINES (dopamine, NE, Epinephrine)
-> HYDROPHILIC (except thyroid hormones = hydrophobic)
Circulate unbound in the blood
Except Thyroid hormones → require
carrier proteins IN BLOOD.
-> Thyroxine-binding globulin (TBG) &
Albumin are both carrier proteins
produced by the liver
Half-life depends on the hormone
o Thyroxine = 7-10 days
o Epinephrine = 1 minute
Bind to cell membrane receptors or nuclear receptors
CHEMICAL STRUCTURE OF HORMONES
- STEROID HORMONES
* Hormones derived from ** ? **
? hormones (glucocorticoids and mineralocorticoids)
? hormones (estrogens, progesterone, androgens)
*Cells that produce steroid hormones have characteristic intracellular or extracellular? features:
o Abundance of:
-> Lipid droplets containing ? ? (CE)
-> ? & ? endoplasmic reticulum (SER)
CHEMICAL STRUCTURE OF HORMONES
- STEROID HORMONES
* Hormones derived from ** CHOLESTEROL **
adrenocortical hormones (glucocorticoids and mineralocorticoids)
sex hormones (estrogens, progesterone, androgens)
*Cells that produce steroid hormones have characteristic intracellular features:
o Abundance of:
-> Lipid droplets containing cholesterol esters (CE)
-> Mitochondria & Smooth endoplasmic reticulum (SER)
- STEROID HORMONES
The type of steroid hormone that is eventually synthesized depends on the presence of specific ? within the particular cell.
? steroid–forming cells do not have enzymes that allow the formation of adrenocortical hormones
The adrenal cortex contains the enzyme systems necessary for the formation of both adrenocortical hormones and ? hormones, although the former are emphasized.
As a result, the adrenal cortex normally produces small amounts of ? steroids and larger amounts in certain pathophysiological conditions.
- STEROID HORMONES
The type of steroid hormone that is eventually synthesized depends on the presence of specific enzymes within the particular cell.
sex steroid–forming cells do not have enzymes that allow the formation of adrenocortical hormones
The adrenal cortex contains the enzyme systems necessary for the formation of both adrenocortical hormones and sex hormones, although the former are emphasized.
As a result, the adrenal cortex normally produces small amounts of sex steroids and larger amounts in certain pathophysiological conditions.
- STEROID HORMONES
There is “storage or no storage??” of steroid hormones within the cell
They are secreted immediately after formation by simple diffusion across the cell membrane because of their “? structure.”
Synthesis and secretion of steroid hormones occur in a ? coupled manner, whereby the “rate of hormone secretion is controlled by the rate of ?.”
The only storage form of steroids within these cells → the ? molecule cholesterol ester
Steroids “ ? “ are usually “constant”→ concentrations of steroids in plasma are usually a good reflection of the ? rate
- STEROID HORMONES
There is no storage of steroid hormones within the cell
They are secreted immediately after formation by simple diffusion across the cell membrane because of their “lipophillic structure.”
Synthesis and secretion of steroid hormones occur in a tightly coupled manner, whereby the “rate of hormone secretion is controlled by the rate of synthesis.”
The only storage form of steroids within these cells → the precursor molecule cholesterol ester
Steroids “metabolic constant rate” are usually “constant”→ concentrations of steroids in plasma are usually a good reflection of the secretion rate
HORMONE - RECEPTOR INTERACTION
Protein Hormones have specific receptors on target tissue plasma membranes (i.e., GPCRs, RTK)
? have specific receptors within the cytoplasm or nucleus
? and ? of receptor and hormone allow hormones to be in low concentration in the blood but effective in producing significant tissue response.
? of the action of a hormone:
? of the hormone from the receptor → ↓ in plasma concentrations of the hormone
? of the receptor-hormone complex through the process of endocytosis (desensitization)
HORMONE - RECEPTOR INTERACTION
Protein Hormones have specific receptors on target tissue plasma membranes (i.e., GPCRs, RTK)
steroids have specific receptors within the cytoplasm or nucleus
specificity and affinity of receptor and hormone allow hormones to be in low concentration in the blood but effective in producing significant tissue response.
Termination of the action of a hormone:
Dissociation of the hormone from the receptor → ↓ in plasma concentrations of the hormone
Internalization of the receptor-hormone complex through the process of endocytosis (desensitization)
