Basic Concepts Flashcards
(23 cards)
Endocrine and Exocrine
- Exocrine- uses ducts
- Endocrine-
- Does NOT use ducts
- Ductless gland that releases product directly into blood stream in order to act on a target tissue
- Can produce one or several chemical messengers
Mosiacs
- Contain several cell types
- Anterior pituitary
- Endocrine pancreas
Classifications of Hormones
Neurohormone: A hormone produced by a nerve cell
Neuropeptide: A peptidergic neurohormone
Neruopeptide Y and Angiontensin II
Nonpeptidergic neurohormone: not made of a peptide chain
Dopamine and Norepinephrine
Neurotransmitter: neurohormone that act transsynapically
Actelycholine
Neuromodulator: a hormone that alters the response of a neuron to the action of a neurotransmitter or hormone
Receptor
- Proteins with highly specific 3D structure and function
- Most commonly in the lipid bilayer of the membrane
- Sometimes found
- In cytoplasm
- In the nucleus
- Near DNA
Hormone Pathway in a Cell Using Receptor
Hormone –> membrane receptor –> 2nd messenger –>
- Acute:
- Protein modification
- Protein-protein interactions
- Phosphorylation
- Enzyme regulation
- Protein modification
- Chronic
- Nuceus –> DNA–>mRN–> protein synthesis
- Effect gene transcription
Hormone Permeability
- Permeable
- Binds to intercellular nuclear receptor
- Steroid
- Thyroid hormone
- Binds to intercellular nuclear receptor
- Non-permeable
- Peptide hormones
- Biogenic amines (catecholamine)
- Prostaglandins
Peptides and glycoproteins
- Derived from amino acids
- Receptor Location: Cell membrane
- Originating tissue: All except adrenal cortex, adrenal medulla, and thyroid
- Examples: Insulin, glucagon, TSH
Steroids
- Derived from cholesterol backbone
- Receptor Location: cytosol and nucleus
- Source: adrenal cortex, gonads, placenta
- Examples: cortisol, testosterone, estradiol, aldosterone
Amines
- Derived from the amino acid tyrosine
- Catecholamines: membrane receptor
- Adrenergic receptor subtype: α1,α2, β1, β2, β3
- Epinephrine: released from adrenal medulla
- Norepinephrine: released from synaptic nerve endings
- 80% of NE comes from neural secretion
- 20% comes from adrenal medulla
- Catecholamines: membrane receptor
Thyroid Hormones
- Released from thyroid gland
- T4
- Thyroine
- Biologically inactive
- 4 iodines in its structure
- T3
- Triiodothyronine
- Biologically active
- 3 iodines in its structure
- T4
- Receptor location: nuclear
Neurotransmitters
- Source: various neurons
- Receptor location: post synaptic membrane receptor
- Examples: Acetylcholine, dopamine, serotonin
Protaglandins
- Source: numerous tissues
- Receptor location: cell membrane
- Examples: PGE2, PGF2α
Hormone Delivery
-
Endocrine: messenger is blood borne
- Primary means of delivery for most hormones
- Neuroendocrine: hormone release by nerve cell is bloodborne
- Neurocrine: neuron contacts its target cells by axonal extensions and the messenger is released into the synaptic cleft between two cells
- Paracrine: released hormone diffuses to adjacent target cells via the extracellular space (Islets of Langerhans)
- Autocrine: hormone released may feedback upon the cell of origin (bradykinin release from endothelial cells)
Neural Control
- Sympathoadrenal: direct sympathetic innervation of adrenal medulla
-
ANS innervation of endocrine glands: central command
- Anterior and posterior pituitary
- Liver
- Pancreas
- Thyroid
- Gonads
- Parathyroids
Circulating Fuels and Ions
-
Plasma Fuels:
- Glucose
- Free fatty acids
- Amino Acids: Arginine
-
Ions:
- Calcium
- Phosphorus
- Sodium
- Potassium
Humoral Transport
- Steroid, thyroid and peptide hormones are bound to specific plasma proteins (binding globulins) for transport in the blood
- Only unbound, free hormone is biologically active
Binding Capacity and Sensativity
- Increased sensitivity
- The greater the hormone binding capacity, the more sensitive the tissue will be to a given concentration of hormone
- More available receptors increases biding capacity and sensitivity
- Response curve shifts left with increased sensitivity
- Response curve shifts right with decreased sensitivity
- Response curve shifts right and down with decreased responsiveness
PKA second messenger system
Hormone –> β-adrenergic receptor –>Gs –> AC –> cAMP –> activate PKA –> TF
Hormone –> α2-adrenergic receptor –> Gi –> AC –> inhibit cAMP
Used by peptide hormones and biogenic amines
PKC
Hormone –> α1-adrenergic receptor –> Gq –> PLC –> PIP2 –>
- DAG –> PKC –> phosphorylation of proteins –> cellular response
- IP3 –> ER –> increases Ca2+ release –>Ca2+ regulated enzymes –> cellular response
*increased Ca2+ also increases sensitivity of PKC to DAG
CaMK
Hormone –> Ach receptor –> opening of Ca2+ channels –> calmodulin binding Ca2+ –> activate affector protein –> cellular response
*both Ca2+ and CaMK are second messengers
*Calmodulin becomes activated by binding Ca2+
* Any Ca2+ increase within a cell can activate this pathway
Receptor Mediated Tyrosine Kinase Activity
Insulin –> α- subunit –> conformational change of β subunit –> Phosphorylation of Tyr residue –> increased Tyr kinase activity –> IRS-1 posphorylation –> cellular response
*IRS 1 is the second messenger
*IRS 1 is not an enzyme, but can act like one downstream
*the receptor itself is the enzyme
Nuclear Receptor
- Hormone enters by diffusion
- Binding of hormone with nuclear receptor
- Activation of hormone/receptor complex
- Interaction between hormone/receptor complex and DNA hormone-response elements (HREs) with transcription of specific DNA sequence into mRNA
- mRNA is translated into cell-specific protein
- Protein subsequently mediates biological response
Steroid Hormone Receptor
- Hormone enters by diffusion
- Binding of hormone with nuclear receptor
- Activation of hormone/receptor complex
- Interaction between hormone/receptor complex and DNA hormone-response elements (HREs) with transcription of specific DNA sequence into mRNA
- mRNA is translated into cell-specific protein
- Protein subsequently mediates biological response
