discuss and define the term hormone
Definition: Hormones are chemical messengers made by glands or special cells.
Transport: They usually travel through the blood to reach target cells or organs.
Function: Tell cells/organs what to do — regulate processes like growth, metabolism, reproduction, and stress response.
Examples:
Insulin → lowers blood sugar by helping cells take in glucose.
Adrenaline → prepares the body for fight-or-flight.
Importance: Keep the body balanced (homeostasis) by coordinating communication between different systems.
what are the properties of hormones
- cell to cell communication molecules
-> chemical signals (usually v low conc) - binding to target receptor initiates cellular response
- communication is eventually terminated
-> by limiting secretion removing/inactivating hormone, terminating target cell activity - half-life = time for [hormone] in blood to reduce by 1/2
-> a measure of stability of the hormone
what factors can hormones be classified based on
- source (ex. pancreatic hormones)
- neuronal control of release
- receptor type
- chemical structure
- function
what are the 3 chemical classes of hormones
- peptide/protein
- steroid
- amine
how are peptide/protein hormones synthesized and stored
peptide/protein - made in endocrine cells
-> made in advance and stored in vesicles for release
preprohormone-> prohormone->hormone
- initially made as large, inactive preprohormone (includes one or more copies of the final peptide hormone)
- series of post-translational modifications converts to prohormone then hormone
- only final hormone in vesicle is active
how are peptide/protein hormones released/transported in blood
- released into ECF via exocytosis then diffuses from ECF into blood (carried away in solution)
what is the half-life of peptide/proteins/hormones
- half life is short (sec to min)
what is the receptor location for peptide/protein hormones
- cell membrane
- lipophobic -> binds membrane receptors
- activates 2nd messenger systems
what is the general cellular response of the peptide/protein hormone
- response usually involves altered activity of target proteins
- modification of existing proteins and induction of new protein synthesis
what are some examples of peptide/protein hormones
- insulin, parathyroid hormone
what is the synthesis and storage of steroid hormones
- made on demand from lipophobic precursors that may be stored in intracellular compartments (SER, cytoplasm)
- made from cholesterol (all have similar structure)
- only made in adrenal cortex, kidney, skin, gonads, placenta
- final hormone is lipophilic = can’t be stored
- cells have lots of SER, contain enzymes required for steroid synthesis
how are steroid hormones released/transported in the blood
- released by simple diffusion into blood
- transported bound to carrier proteins
what is the half life of steroid hormones
- longer half life (hours)
what is the receptor location of steroid hormones and the response
- cytoplasm or nucleus
- some have membrane receptors also
1. intracellular receptors -> slow genomic response (=modulation/regulation of gene activity)
2. membrane receptors -> fast non genomic response - activation of genes for transcription and translation
what is the general cellular response of steroid hormones
- induction of new protein synthesis
what are examples of steroid hormones
- aldosterone
- estrogen
- testosterone
how are amine hormones synthesized and stored
- made in pineal gland, adrenal medulla, thyroid
- mostly derived from tyrosine
- catecholamines (adrenaline) - made in advance, stored in secretory vesicles
- thyroid hormones - synthesized on demand from stored precursors
how are amine hormones released and transported in the blood
thyroid - transport protein, bound to carrier protein
catecholamines - exocytosis, dissolved in plasma
what is the half-life of amine hormones
catecholamines - short
thyroid - long
what is the location of the receptor of amine hormones and response
catecholamines - cell membrane, lipophobic
-> activation of 2nd messengers
thyroid - nucleus, lipophilic
-> activation of genes for transcription and translation
what is the general cellular response of amine hormones
catecholamines - modification of existing proteins
thyroid - induction of new protein synthesis
what are some examples of amine hormones
catecholamines - epinephrine, norepinephrine, dopamine
thyroid - thyroxine (T4)
what are catecholamine and thyroid hormones similar to
catecholamines - similar to peptide hormones
thyroid - similar to steroid hormones
compare endocrine vs exocrine glands
gland = collection of secretory cells
exocrine - A hollow center, or lumen, forms
in exocrine glands, creating a
duct that provides a passageway
for secretions to move to the
surface of the epithelium.
- release secretions to the body’s external environment through ducts or internal surfaces continuous with the outside
- ex. Sweat glands, mammary glands in the
breast, salivary glands, the liver, pancreas
endocrine - lose the connecting bridge of cells that links them to the parent epithelium. Their secretions go directly into the bloodstream.
- ductless
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