5.1 Intro To Endocrine Flashcards
Functions of endocrine system
- Regulates multiple organs
- Maintains growth and reproductive needs
- Respond to fluctuations within the internal environment
Study of processes involved in the regulation and integration of cells and organ systems by hormones
Endocrinology
Endocrine glands of the brain
Hypothalamus gland and pineal gland
Transitory endocrine gland
Placenta
Type of communication where the cell recognizes itself as the target cell
Autocrine
Signaling molecule is received by a neighboring cell (type of communication)
Paracrine
Characteristics of neuron doctrine communication
- Secreted by neuron
- Travels via blood
- Acts on distant target cells
Mode of travel for endocrine communication
Via blood
Precursor of secretory peptides
Prehormone/preprohormone
What happens to secretory hormones after its synthesis
Stored in secretory vesicles
At what terminal of nascent peptides can signal peptides be found
N-terminal
Where are the receptors of hydrophilic peptides found
Membrane-bound/surface of cell membrane
Signals from hydrophilic peptides are amplified by
Second messengers
Water-soluble hydrophilic peptides can enter the circulatory system (T/F)
True
Peptide hormones are biologically active and are free to interact with receptor of target cell when in what form
Free form
What condition of free hormones will result to the release of hormones from transport protein?
Decreased levels of free hormones
Extends the half-life of hormones
Bound hormones
The only 2 peptide hormones that work in bound form
Growth hormone and IGF-1
Onset and duration of peptide hormone
Fast onset and short-time duration
Number of amino acids for it to be considered a protein
Greater than 100 amino acids
Peptide if less than 100 amino acids
Peptide hormone: Rough ER
Steroid hormone: __________
Smooth ER
Steroid hormones are stored in secretory vesicles (T/F)
False - peptide hormone not steroid
Peptide hormone: water soluble
Steroid hormone:
Lipid soluble/hydrophobic
Peptide hormones are degraded by
Peptidases
Site of steroid hormone receptors
Intracellular (cytoplasm or nucleus)
Steroid hormones with cytoplasmic receptors
Adenocorticosteroids, glucocorticoids, mineralocorticoids
Location of Vitamin D and sex steroid hormone receptors
Inside nucleus
Effect of steroid hormones
Increase or decrease transcription of regulatory proteins by modulating gene expression
Precursor of steroid hormone
Cholesterol
Steroid hormones have no storage, thus, must be synthesized after stimulus is received. How does the body compensate for this
Large stores of cholesterol esters in cytoplasm vacuoles are available for steroid synthesis
Amino acid derivatives
Tyrosine or tryptophan
Amino acids can function either as a peptide or a steroid (T/F)
True
Ioidothyronine, a steroid-like amine, is synthesized in
Thyroid gland
Ioidothyronine derivative
Tyrosine
Half-life of T3 and T4
T3- 18 days
T4- 7 days
Thyroid hormone is a steroid-like amine. How is it similar to steroid hormones
- Intracellular receptor (nucleus)
- Acts as a transcription factor
- Protein bound
- Slow onset and long duration
Primary hormones produced by endocrine system
Catecholamines
Catecholamines are synthesized by
Adrenal medulla and neurons
Catecholamines are copackaged with
ATP, Calcium, Chromogranins (proteins)
After Catecholamines are synthesized, the final product is stored in
Chromaffin granules
Catecholamines are secreted in response to
Sympathetic stimulation
Catecholamines only circulate when bound to albumin (T/F)
False - circulate either unbound or loosely bound to albumin
Half-life of Catecholamines
1-2 minutes
Catecholamines are peptide-like amines. How are they similar to peptide hormones
- Do not cross cell membrane
- Membrane-bound receptors
- Make use of second messengers
- Stored in vesicles
- Plasma form is unbound
- Fast onset and fast/short duration
Cells and receptors exhibit specificity (T/F)
False- only receptors exhibit specificity. Cells may have receptor for different hormones
What are the cell membrane receptors
GPCR, Catalytic, Cytokine
How many domains does GPCR have? Describe each
3 - extracellular (ligands bind), transmembrane (7 subunits), intracellular (G-protein bind)
When inactivated, alpha subunit remains dissociated from beta-gamma subunit (T/F)
False- alpha reforms with beta-gamma when inactivated
Peptide hormones that bind Receptor Tyrosine Kinase
Insulin
IGF-1
NGF
Peptide hormones that bind to Cytokine receptors
Prolactin
GH
Erythropoietin
Leptin
In the mechanism of GPCR, GTP binds to which heterotrimer subunit?
Alpha
Peptide hormones that bind to receptor tyrosine kinase (RTK)
Insulin
IGF-1
NGF
Peptide hormones that bind to Cytokine Receptor
Prolactin
GH
Erythropoietin
Leptin
Effectors of adenylyl cyclase, Phospholipids C, Phospholipase A2
adenylyl cyclase - cAMP
Phospholipids C - DAG (activate protein kinase C) and and IP3 (open calcium channels)
Phospholipase A2 - eicosanoids (releases arachidonic acid)
Catalytic receptors posses enzymatic activity on the cytoplasmic side (T/F)
True
Ligand of guanylyl cyclase receptor
ANP
Receptor of “Transforming Growth Factor beta (ligand)”
Serine/threonine kinase
In Serine/Threonine Kinase Receptor, ligand binding to type II receptor leads to
Dimerization of type I and type II receptors (type II phosphorylates type I)
Type I phosphorylates SMAD, which complexes with co-SMAD. What does this complex do
Act as a transcription factor
In Tyrosine kinase receptor mechanism, ligand binding results to
Dimerization and autophosphorylation
Effectors of tyrosine kinase
GRB2 and IRS1
Receptor with a single membrane spanning domain
Cytokine Receptors/ Tyrosine Kinase Associated Receptors
Cytokine receptors do not posses any catalytic activity instead they are associated with tyrosine kinases like JAK protein (T/F)
True
Mechanism of Cytokine receptors
Ligand binding -> Dimerization then activation of JAK -> JAK phosphorylates STAT -> dimerize STAT dimer
STAT dimer goes to the nucleus to act as
Transcription factor
Intracellular receptors are peptide receptors (T/F)
False- steroid receptors not peptide
Intracellular receptors function to modify protein synthesis through
Gene expression
2 types of intracellular receptors and describe in terms of their bound state
- Cytoplasmic receptor (bound receptor)
2. Nuclear receptor (unbound receptor)
Intracellular receptors of glucocorticoids and mineralocorticoids
Cytoplasmic receptor
Intracellular receptor of progestins, androgens, estrogens, and vitamin D
Nuclear receptor
(T/F) Mechanism of cytoplasmic receptor:
Ligand binds in the cytoplasm -> dissociation of HSP -> ligand-receptor complex translocate to the nucleus -> complexes with HRE -> gene transcription is activated
True
In nuclear receptors, how do steroids pass through the cytoplasmic membrane
Diffusion
Steroid enters the nucleus through
Nuclear pore
Response counteracts the stimulus, shutting off the response loop
Negative feedback
Low levels of hormones: ______ production
High levels of hormones: ______ production
Increase
Decrease
Negative feedback ensures stability by
Keeping a physiologic parameter within normal range
Types of negative feedback loops
Response-driven feedback loop and endocrine axis-driven feedback loop
Negative feedback has little to do with the physiologic response to the hormone (T/F)
True
In positive feedback, the stimulus causes a _______ in response
Continuous increase
Required to shut off positive feedback cycle
Outside force
Causes the sequential series of release of hormones
HPT Axis
In HPT Axis, what are the hormones involved
Anterior Pituitary Hormones only
Which glands are involved in the HPT Axis and identify their hierarchy
Hypothalamus (1st tier) Pituitary gland (2nd tier) Peripheral endocrine gland (3rd tier)
Type of hormone released by the following glands in HPT Axis:
Hypothalamus
Pituitary gland
Peripheral endocrine gland
Hypothalamus: releasing hormone
Pituitary gland: stimulating hormone
Peripheral endocrine gland: final hormone
Negative feedback targets which glands in HPT Axis
Hypothalamus or pituitary gland
Organs not directly controlled by anterior pituitary gland
Free-standing endocrine organs (ex. Parathyroid gland and endocrine pancreas)
When does the parathyroid gland secrete hormones
When there is a decrease in ionized calcium
Decrease in ionized calcium -> Parathyroid gland is stimulated -> secrete hormone-> PTH Hormone increase ______
Serum calcium back to normal
Type of feedback loop wherein a change in substrate level causes negative feedback
Response-driven feedback
Hypothalamic releasing hormones : ________
___________ : posterior pituitary
Anterior pituitary
Nerve signals from hypothalamus
Steroid-like amino acid derivatives (T3 and T4) are produced in
Cytoplasm