Endocrine System Flashcards
What is the Endocrine System?
Another way to regulate and coordinate animal body functions; works together with the nervous system to maintain homeostasis. The endocrine system works over long term while the nervous system works over short term, both using extensive feedback loops for coordination.
What features does the Endocrine System share with the Nervous System?
Both use chemical messengers to signal effector cells, similar mechanisms of messenger release, and similar mechanisms at effector of cell membrane, and both have similar biochemical diversity (4/5 neurotransmitters, 3 major hormones).
What differences does the Endocrine System have from the Nervous System?
All animals use endocrine signals, chemical signals (hormones) are carried in body fluids, and it provides long-term regulation.
What is a Gland?
An organ/tissue responsible for the synthesis and secretion of cellular products.
What is an Exocrine Secretion?
A secretion of chemicals onto a body surface or into a duct.
What is an Endocrine Secretion?
A secretion of chemicals into body fluids. They do not use ducts, they release directly into body fluids - synthesized in epithelial cells first.
What do Endocrine Regulations include?
Autocrine, paracine, and neuro-endocrine regulations.
What is Autocrine Regulation?
Hormones are released by the cell it was synthesized from, acting on the same cell.
What is Paracine Regulation?
Hormones bind to an adjacent cell/cell in close proximity.
What is Neuro-endocrine Regulation?
Hormones are released, move through the blood stream, and bind to cell.
What organs/tissues have dual endocrine and exocrine functions?
Pancreas, reproductive organs, liver, kidney, stomach, small intestine.
What are Hormones?
Signalling molecules secreted by endocrine cells. Hormones regulate physiology, behaviour, and development.
What are Amines?
Hormones that are small, water-soluble, and derived from tyrosine or tryptophan. Their cell receptor is the plasma membrane (except thyroid hormones), and they use second messengers (not thyroid hormones). Hydrophilic.
What are Proteins/Peptides?
Hormones that are water soluble, with the cell receptor on the plasma membrane, and use second messengers. Hydrophilic.
What are Steroids?
Hormones derived from cholesterol, mostly lipid-soluble. Their cell receptor is the cytosol or nucleus, and they usually stimulate gene transcription. Hydrophobic.
What are Fatty Acids/Derivatives?
Hormones like prostaglandins, juvenile hormone (in insects); act as autocrine and paracrine factors.
What is the Signalling Mechanisms of Non-steroid Hormones?
These are hormones derived from Amino acids - epinephrine, insulin, glucagon.
They bind to plasma membrane receptors; hormone binds to a receptor on the plasma membrane, triggering the pathway.
Can Non-Steroid Hormones bind to multiple cells?
Yes, a single hormone can act on multiple cells - triggering different responses.
This often involves a second messenger pathway, and elicits different responses.
What is the Signalling Mechanisms of Steroid Hormones?
They are lipid hormones that are derived from cholesterol. They bind to intracellular receptors. A single hormone can activate or inactivate multiple genes, triggering different responses.
Synthesis Pathway - Amine Hormones
Can act as a hormone or a neuro-transmitter, or both. The molecule produced depends on the enzyme gene expression in secretory cells.
Hydrophilic hormones stored in secretory vesicles before excretion from cell.
Regulation of synthesis (enzyme expression) and secretion (calcium mediated exocytosis).
Tyrosine - Amino Acid - Derivatives
L-dopa = inactive intermediate Dopamine = brain hormone Norepinephrine = fight or flight Epinephrine = fight or flight
Synthesis Pathway - Cholesterol Hormones
Diversity of steroids made from cholesterol.
Tissues have different enzymes/intermediates (example: estradiol synthesized from testosterone). Hydrophobic hormones diffuse out after synthesis (they are not stored in the cell).
Regulation of synthesis - enzyme expression involved in pathway.
Cholesterol - Derivatives - Steroids
Pregnenolone = intermediate Aldosterone = osmotic balance Coristol = body's response stress Testosterone = sex hormone = Estradiol Progesterone = sex steroid Ecdysons
What are Hormone Levels in Blood/Fluid Regulated by?
Altering the rate of hormones synthesis, altering the rate of secretion (release from secretory vesicles), removal (clearance) mechanisms (hormones are only useful when needed, when they aren’t they must be removed - steroid [lipophilic] must be converted into a water soluble molecule before secretion).
Converting inactive forms to active forms at the target tissue (ex. T4 to T3)
Homeostatic feedback loops are very important.
