Unit 2 - Intro into Endocrine Physiology Flashcards
What is a hormone?
a signaling molecule released by a cell and conveyed by the blood stream by neural axons, or by local diffusion to cells in target tissues
What is a hormones chemical nature?
protein, peptide, catecholamine, steroid, or iodinated tyrosine derivative
What do hormones do at the target tissue?
regulates metabolic pathways, via second messengers, or regulates synthesis of enzymes and other proteins at the DNA level
What is the function of the endocrine system?
to regulate metabolism, fluid status, growth, sexual development, and reproduction
What other system does the endocrine system work with in order to maintain homeostasis?
the nervous system
What are the four types of hormonal action based on the route by which the signalling molecule reaches the target?
autocrine, paracrine, endocrine, and neurocrine
What is autocrine action?
the hormone acts on the cell which released it; it binds on the cell itself
What is paracrine action?
the hormone acts on adjacent cells without entering the blood stream
What is endocrine action?
before reaching target cells, hormone first enters the blood stream
What is neurocrine action?
it refers to the interaction between neurons and endocrine cells
What are the four categories of hormones?
Peptide, protein, and glycoprotein hormones, catecholamine hormones, thyroid hormones, steroid hormones
How are peptide, protein, and glycoprotein hormones synthesized?
DNA to messenger RNA to preprohormone to prohormone to hormone
How are peptide, protein, and glycoprotein hormones stored?
in secretory granules originating from the golgi apparatus
How are peptide, protein, and glycoprotein hormones secreted?
by exocytosis
How are catecholamine hormones synthesized?
from amino acid tyrosine
How are catecholamine hormones stored?
in secretory granules
How are catecholamine hormones released?
via exocytosis
How are thyroid hormones synthesized?
from tyrosine and iodine
How are thyroid hormones stored?
extracellularly in follicles of the thyroid gland as a component of a large protein molecule
How are thyroid hormones secreted?
they have to be retrieved from the follicle and released from the storage protein
What are steroid hormones synthesized from?
cholesterol
How are steroid hormones stored?
they arent
There is a possible 5th type of hormone, what is it?
lipokines
What feedback system is the dominant mechanism of regulating hormone secretion?
negative feedback
How does negative feedback work in regulating hormone secretion?
the condition requiring hormone action, such as deviation from homeostasis, is sensed, stimulating endocrine cells to secrete hormone to fix the abnormality. Once it is fixed, hormone secretion is ceased
How would you characterize negative feedback?
common, stable, and critical for homeostasis
How does positive feedback work in regulating hormone secretion?
once a hormone is first secreted , it promotes further secretion of hormone until some physiologic end point is achieved
How would you characterize positive feedback?
rare, unstable, and used when a surge of hormone is required
What happens to horomones after they are secreted into extracellular fluid?
they circulate either free or bound to other plasma constituents and are eventually taken up by cells or metabolically degraded and removed by urinary or biliary secretion
What does half-life mean in regards to hormones?
it referes to the time in which the hormone loses 50% of its biological activity
Describe the events that occur after hormones reach their target cells.
the hormone binds to a specific receptor in the target cell, this changes the enzyme activity or concentration which leads to the regulation of mutliple metabolic pathways and results in the physical change the hormone was set out to accomplish
Which property of a cell determines whether it will be affected by a particular hormone?
the hormone concentration together with the number and sensitivity of involved receptors
Where are lipophilic receptors normally found?
within the cell; cytoplasm or nucleus
Where are lipophobic receptors normally found?
on the cell membrane
What are first messengers?
extracellular signaling molecules that second messengers respond to
What are second messengers?
intracellular signaling moleciles released by the cell in response to exposure to extracellular signaling molecules
How are second messengers activated?
by enzymes
What are the consequences of second messenger actions?
they alter the cells physiology
What second messenger systems are most commonly activated by protein and catecholamine hormones?
cAMP or IP3/DG
How do second messengers affect the physiology of target cells?
they activate protein kinases which phosphorylate other proteins leading to the eventual physiologic effect
Why can relatively few molecules of hormones produce a large physiologic response?
intracellular signal amplification
How does intracellular signal amplification work?
a signal ligand activates multiple G proteins, each G protein activates an inzyme that produces multiple molecules of the second messenger, the second messengers then activate other enzymes and each enzyme reactions on multiple molecules of the substrate
What happens when a steroid binds to its receptor within a cell?
the shape of the receptor changes and forms a bond with a transcription regulating hormone
The dimer formed when a steroid binds to a transcription regulating protein can have what result?
an increase or inhibition of transcroption and translation
What are the products of steroid hormone action?
enzymes, structural proteins, receptor proteins, and transcriptional proteins
What does the synergism of hormonal action mean?
that different types of hormones can work together
What is an example of a process that uses synergism of hormonal action?
gluconeogenesis
