Module 1 Flashcards
Gland
Specialized cell/cell group/organ that secretes substances to be used/eliminated by the body
Functions of the Endocrine system
- Homeostasis
- Adaptive Stress Response
- Growth and Development
- Autonomic Nervous System Integration
- Reproduction
- Red Blood Cell Production
What are glands coordinated by?
Hormones that produced homeostatic adjustments
Hormone
Chemical substances secreted directly into the bloodstream
How do hormones circulate? And what types can they be
circulates in low quantities to exert physiological effects at distant target tissues: can be hydro- or lipo-philic
Hydrophilic
Water soluble, low lipid solubility; generally free, unbound to plasma carrier molecules
Lipophilic
Fat/lipid soluble, low water solubility; generally bound, requires plasma carrier molecules and therefore lasts longer as they are bound and cannot be removed
Peptide Hormones
(synthesis, packaging, secretion)
- amino acid chains
- free in plasma
- Preprohormones (in ER/ribosomes) -> Prohormones -> Hormones
- ER, Golgi, packed into secretory vesicles
- Cell signals initiate exocytosis; vesicles/hormones released into blood
Amine Hormones
(Catecholamines, Thyroid Hormones)
- single amino acids
- Norepinephrine, Epinephrine, can be free or bound in plasma
- Actually lipophilic and requires carrier molecules (bound)
Steroid Hormones
(synthesis, storage)
- 4-ring carbon structure
- Cholesterol is the precursor for all steroid hormones
- end hormone determined by the tissue that cholesterol ends up in
- Lipophilic and cannot be contained in phospholipid bilayers
- released as they are made -> rate of synthesis is the main regulator (only exception: thyroid)
Examples of Steroid Hormones
- cortisol
- aldosterone (adrenal cortex)
- progesterone/test/estrogen (gonads)
Amine thyroid hormones
Amine hormone released by the thyroid
Requirement of hormone/cell interaction
Hormone must be free/unbound to interact with target cell receptor
Hormones and cell interaction
- Hydrophilic hormones = not a problem (peptides and unbound catecholamines)
- More of a problem for lipid hormones and if they’re bound
Dynamic Equilibrium
(hormone/cell interactions)
Lipophilic hormones are binding and rebinding
- some fraction is unbound at any given time -> they’re active and can act on target cells
- bound is not
Specific Hormone Receptors
Peptide and Catecholamine Hormones
- Can’t cross cell membrane as they are charged/polar
- Binds to specific receptors on outer plasma membrane surface
General MoA of Specific Hormone Receptors
Activates a secondary messenger system to amplify signals from low hormone concentrations
cAMP (Specific Hormone Receptors) MoA
- Hormone binds to surface receptor
- G-protein is activated and activates Adenylyl Cyclase; converts ATP to cAMP
- cAMP activates protein kinase A (PKA)
-
PKA phosphorylates and activates the target proteins to have the result
- Includes ACTH, Calcitonin, Epi, Glucagon, PTH, ADH (ACE GPA)
Ca2+ (Specific Hormone Receptors) MoA
- Hormone binds to surface receptor
- G-protein is activated and activates Phospholipase C; converts PIP2 -> IP3, DAG
- IP3 mobilizes intracellular Ca2+ to active calmodulin
- Ca2+-Calmodulin complex activates Ca2+-Calmodulin-dependent protein kinase (CaM Kinase)
-
CaM Kinase phosphorylates and activates target proteins to have the result
- Includes GHRH, GnRH, OXT, ACh, Epi, TRH
Difference between hydrophilic and lipophilic movement across the cell membrane
Peptide and Catecholamine Hormones: Can’t cross cell membrane as they are charged/polar
- Binds to specific receptors on outer plasma membrane surface
Steroid, Thyroid Hormones: Easily diffuse across the lipophilic plasma membrane
- Binds to specific intracellular receptors to regulate gene transcription, protein synthesis
Steroid, Thyroid Hormone (Protein Synthesis Regulation)
- Lipophilic hormone diffuses across plasma/nuclear membrane, interacts with intracellular receptors (either in cytoplasm or nucleus)
- Hormone-Receptor (H-R Complex) binds to DNA Hormone Response Element (HRE)
- HR-HRE binding activates specific genes to transcribe mRNA -> ribosome translation
-
Newly synthesized protein leads to hormonal cellular response
- Includes testosterone, estrogen, progesterone, aldosterone, calcitriol
Neurotransmitters vs. Hormones
(4)
Nervous (Along set nerves) VS. Endocrine (Bloodstream Circulation)
Transmitted across synaptic cleft VS. Transported through blood
Made by neurons VS. Made by endocrine glands
Travels short distance across synapse VS. Travels long way across body/bloodstream
Neural vs. Endocrine Control: RESPONSE SPEED
Nervous (ms)»_space;> Endocrine (minutes/hours)
Neural vs. Endocrine Control: EFFECT DURATION
Nervous (brief) «< Endocrine (long, persists after stimulus stops)
Neural vs. Endocrine Control: TARGET NUMBER
Nervous (single hardwired muscle/gland) «< Endocrine (many across circulation)
Tropic Hormone
released: these hormones stimulate other endocrine glands to release their hormones
- Includes most Anterior Pituitary (AntPit) hormones and Hypothalamic hormones
Hypothalamus
- controls hormone release
- interacts with pituitary gland lobes in different ways
Pituitary gland
(what, location and divisions)
- small gland in skull sella turcica
- divided into completely separated lobes:
1. Posterior Pituitary Gland “Neurohypophysis”
2. Anterior Pituitary Gland “Adenohypophysis”
Neurohypophysis
Posterior Pituitary Gland
consists of neural-like tissue
Hypothalamic Stimulation:
(PostPit)
- PostPit directly connected to hypothalamus by neural pathways
- within hypothalamus -> two well defined clusters of neurons:
1. supraoptic nucleus
2. paraventricular nucleus - axons from nuclei project onto connecting pituitary stalk and terminate on posterior pituitary blood vessels
Pituitary Stalk
the narrow region connecting the hypothalamus and the pituitary
Adenohypophysis
Anterior Pituitary Gland
consists of endocrine glandular epithelial tissue
Hypothalamic Stimulation:
(AntPit)
Hypothalamic-Hypophyseal Portal System
^ system of arteries/capillaries
