Endocrine Physiology Flashcards
Endocrine System
-2nd great controlling system
-hormones
-pituitary, thyroid, parathyroid, adrenal, pineal, and thymus glands
-pancreas, gonads to hormones + exocrine secretions
-Hypothalamus: neural functions + hormone release (pit)
-Adipose tissue
-Exocrine release into the body but outside the bloodstream.
How do hormones cause effects in their target cells?
receptors
Paracrines
Communicate with neighboring cells
-interleukins + interferons from WBC
Autocrines
Act on the cell that secreted it, self-stimulation
-histamine in inflammation
Neurotransmitters
Released by neurons into synapse (gap between neurons)
-acetylcholine
Hormones
Released by endocrine glands, secreted into interstitial fluid, diffuse to blood and travel to distant target
-insulin
Neurohormones (neuroendocrine)
Neurotransmitter released and travels outside brain
-antidiuretic hormone
Amines
epinephrine /norepinephrine come from tyrosine
Thyroxine
tyrosine cleaved off of thyroglobulin + iodine, GENE EXPRESSION
Peptide/Protein
ACTH, oxytocin, growth hormone, GENE EXPRESSION
Amino acid-based (majority)
-Amines
-Thyroxine
-Peptide/Protein
Lipid-based
Cholesterol-based
-steroids=gonadal (testosterone) and adrenocortical (cortisol) hormones
Fatty acid-based (arachidonic acid)
-eicosanoids= leukotrienes and PROSTAGLANDINS (PGE2, PGD2)
Fatty-Acid Based Hormones: Prostaglandins
-made throughout the body by most cell types
-fatty acids (mostly in cell membrane) are the starting substrate
-enzymes convert the fatty acid (arachidonic acid) into a hormone (prostaglandins) in the cell membrane
-It is a hormone once it is release into the bloodstream
-Prostaglandins act on cell surface g-protein-coupled receptors (GPCRs)
-GPCR signaling inside the cell eventually affects gene expression in the nucleus
What are steroids made from?
cholesterol
Cholesterol-Based Steroid Hormones
-Steroid hormones are released into the blood and diffuse easily into their target cells
-Steroid bind and activate a specific receptor inside target cell
-Hormone-receptor complex enters nucleus and affects gene expression
-Nuclear receptors are transcription factors!
-Cholesterol can cross cell membranes and act inside the nucleus as transcription factors, act as an activator
-Hormone-receptor complex binds to a response element on the DNA
Recep on Steroids
-Steroids hormones are made from CHOLESTEROL
-Whether a certain one will be made in a certain cell at a certain time depends on whether the RIGHT ENZYMES ARE EXPRESSED (MADE)
-The cholesterol-like structure allows steroids to diffuse across plasma membrane and enter cell
-steroids bind to receptors inside of cell that allow them to enter NUCLEUS AND BIND DNA to regulate transcription (nuclear receptors are transcription factors!)
Peptide Hormones
-comprised of amino acids
-made through gene expression and the secretory pathway
-cleaved from the protein after translation
-Most act on G-protein-coupled receptors (cell surface)
Amino acids
serve as building blocks for protein (translation), substrate for enzymatic conversion into some hormones, and some act as neurotransmitters
-formed by enzymatic synthesis or provided through diet, ~20 protein-containing AA
Peptides
2 or more amino acids joined by peptide bond
-most formed by enzymatic cleavage of protein (digestion in gut, NEUROPEPTIDE AND PEPTIDE HORMONE SYNTHESIS)
Proteins
usually larger than polypeptides, usually 50 to 1000 AA
-formed by TRANSLATION at a ribosome. Hormone=secretory pathway
-Proteins are genome encoded
a) gene expression
b)50 or more amino acids
Hormone Synthesis 1. Synthesis and storage
-hormones is synthesized and then stored in secretory vesicles
-nucleus (DNA to mRNA
-Ribosomes (Preprohormone (the protein))
-Endoplasmic reticulum (Prohormone (the protein))
-Golgi apparatus, stored in secretory vesicles (peptide hormone)
-Into blood!
-The Endoplasmic reticulum and Golgi are the secretory pathway
Hormone Synthesis 2. Transport
-upon release, travels freely in the blood
-peptide hormone
Hormone Synthesis 3. Binding and effects
-bind membrane receptors, initiate protein modification and synthesis
-hormone-receptor complex activates second messenger systems.
-happens on cell membrane
What are two major ways that a hormone can transduce a signal to change function in a cell?
- Cell surface RECEPTOR (like G-protein): signal transmitted to intracellular messengers that eventually affect transcription
- Nuclear RECEPTOR inside of cell that binds DNA (transcription factor) to directly affect transcription
-steroids act as transcription receptors.
Cell Surface Receptors: G Protein-Coupled Receptors (GPCRs)
-peptide can’t penetrate plasma membrane
-receptor binds ligand (peptide hormone)
-binding causes a conformational change in receptor
-The G-alpha protein dissociates
-G-alpha protein causes signaling inside cell
-3 SIGNALING PATHWAYS TO KNOW FOR THIS CLASS GAS, GAI, AND GAQ
Gas
this type STIMULATES (s= “stimulatory”) adenylyl cyclase (AC)
Gai
This INHIBITS (i= “inhibitory”) adenylyl cyclase, lowering the level of cAMP in the cell.
Gaq
This activates PHOSPHOLIPASE C (PLC), which generates the second messengers inositol trisphosphate (IP3) and diacylglycerol (DAG)
GPCR Pathway: Gaq
-ligand binds receptor , activates G protein
-G protein activates a phospholipase enzyme
-Phospholipase splits the phospholipid PIP2 into diacylglycerol (DAG) and IP3 (both act as second messengers)
-DAG activates protein kinases; IP3 triggers release of Ca2+ stores
-Ca2+ (third messenger) alters cellular responses
How many hormones does the dual-lobed have?
Nine
Neurohypophysis
-posterior lobe (neural tissue) and the infundibulum (stalk that connects hypothalamus to pituitary)
-receives, stores, and releases hormones from the hypothalamus
-hormone delivered via nerves
Adenohypophysis
-anterior lobe, made up of glandular tissue
-synthesizes and secretes hormones into blood
-told by hypothalamus to produce/release hormones via blood signals
Major Hormonal Cascades
-Growth
-Stress
-Lactation
-Metabolism
Growth Hormone (GH): Regulation of Growth
-synthesized by somatotropic cells (somatotrophs) of anterior
-stimulates most cells, but targets bone and skeletal muscle
-promotes protein synthesis + encourages use of fats for fuel
-most effects are mediated indirectly by somatomedin
-stimulates uptake of amino acids from blood
-mobilizes fats
Growth Hormone GHRH
-growth hormone releasing hormone
-stimulates growth hormone release
Growth Hormone GHIH
-Growth Hormone Inhibiting Hormone
-AKA Somatostatin (SS) inhibits Growth Hormone release
What do feedback loops do?
-ensure balance
-avoid over- or under- stimulation
Where does IGF1 go?
Into the blood
Recep on Growth
-Big picture: GH increase growth
-Medium picture: Hypothalamic - pituitary - live: feedback loops
-Small picture: GHRH and SS bind GPCR G-alpha
How you define stress?
-stimulus of a threat
Adrenocorticotrophic Hormone (ACTH; corticotropin) and stress
-stimulates adrenal cortex -> release corticotropin
-triggered by hypothalamic corticotropin-releasing hormone (CRH)
-Internal and external factors such as fever, hypoglycemia, and stressors can trigger the release of CRH
Pro-Opiomelanocortin (POMC)
-a protein
-multiple hormones can be made from the same protein
-POMC is where ACTH and B-Endorphin come from
What hormones can be made from arachidonic acid?
Prostaglandins and leukotrienes
What hormones can be made from cholesterol?
-Aldosterone
-cortisol/corticosterone
-testosterone
Where are ACTH and endorphins from?
-the POMC protein
Stress Response Hormone
-epinephrine
-cortisol (HPA)
-endorphins
What does cortisol activate?
nuclear receptors
What are effects of long-term cortisol release?
-weakened immune system
-anxiety, depression, and headaches
-nerve problems
-digestive issues
-high blood pressure
-high blood sugar
-heart disease
Big picture of stress cascade
ACTH released in response to stress
Medium picture of stress cascade
-hypothalamus-pituitary-adrenal (HPA)
-feedback loops
Small picture of stress cascade
-CRH binds to GPCR
-G-alpha, ACTH binds GPCR
-G-alpha and or -q
What does dopamine do to prolactin?
inhibits it
What hormone regulates blood calcium and keeps blood calcium from getting to high?
Parathyroid
What hormone regulates blood calcium and keeps blood calcium from getting to high?
calcitonin
Big picture of the regulation of lactation
prolactin and oxytocin: milk synthesis and letdown
Medium picture of the regulation of lactation
hypothalamus-pituitary-mammary; feedback loops
Small picture of the regulation of lactation
dopamine binds GPCR: G-alpha i, oxytocin binds GPCR: G-alpha q
What does parathyroid hormone (PTH) do to bone?
-tells the bone to release calcium
-bone activates osteoclasts; calcium and phosphate ions release into blood
What does parathyroid hormone (PTH) do to the kidneys?
-tells them to prevent calcium from leaving in urine
-promotes activation of vitamin D and increase calcium reabsorption
What does parathyroid hormone (PTH) do to the intestines?
-tells them to increase absorption from diet
Parathyroid Hormone (PTH) Effects
-PTH increase release (Ca2+ blood)
-stimulates osteoclasts to digest bone matrix
-enhances the reabsorption of Ca2+ and secretion of phosphate by the kidneys
-increase absorption of Ca2+ by intestinal mucosal cells
-increase (Ca2+ blood) inhibits PTH release
Calcitonin
-peptide hormone produced by the parafollicular, or c, cells of thyroid
-decrease blood calcium
-opposes parathyroid hormone (PTH)
-calcitonin -> skeleton
-regulated by blood calcium ion, negative feedback
What happens when calcitonin inhibits osteoclast activity?
inhibits bone reabsorption and release of calcium
What happens when calcitonin stimulates osteoclast activity?
calcium uptake and incorporation into bone
Recap on Major Hormonal Casades
-growth hormone and growth
-ACTH and stress
-prolactin/oxytocin and milk production
What is the big picture of the major hormonal cascades?
hormone regulates physiological processes
What is the medium picture of the major hormonal cascades?
cascades hypothalamus, pituitary, target organ and feedback loops
What is the small picture of the major hormonal cascades?
G protein-coupled receptor signaling in a cell, gene expression in a cell, and metabolism in a cell
