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Flashcards in Endocrine System Deck (42):

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


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.


Virtually all tissues produce an ___ messenger.

Endocrine messenger. Body fluids are a 'soup' of messengers.


Only cells with a specific receptor protein will ___ to a ____.

Only cells with a specific receptor protein will respond to a hormone.


What type of glands are there in the vertebrate endocrine system?

There are over a dozen glands. Some are specialists; thyroid and pancreas. Some have other functions; pancreas.
Only the adrenal gland and sex organs produce steroid hormones.


What connects the endocrine and nervous system?

The hypothalamus - the control centre for almost all the major endocrine systems in the body.


What is the Hypothalamus?

The control centre of the endocrine system; acts through the pituitary.


True or False: Some amine hormones can also act as neurotransmitters.



True or False: Hormones can act as both local and distant chemical messengers.



True or False: Neuro-hormones act via autocrine or paracrine signalling.

False, neuro-hormones act via Neuro-endocrine signalling.


True or False: Steroid hormones are produced only when they are needed.



True or False: A single hormone can regulate multiple physiological functions.



True or False: Steroid hormones exert their effect by activating the 2nd messenger (e.g. cAMP) pathway.

False. They exert their effect intracellularly.


True or False: Steroid hormones are lipid soluble, diffuse through the plasma membrane, cause genes to be turned off or on.



What is the Posterior Pituitary?

Nervous tissue; stores and secretes hypothalamus hormones (selective ones, doesn't make its own).


What is the Anterior Pituitary?

Glandular tissue (actual endocrine tissue), produces and secretes its own hormones.


What is the Hemostatic Role of the Hypothalamus?

TRH = TSH-releasing hormone.
TSH = Thyroid-stimulating hormone.
Thyroxine = increases metabolic rate/increases body temperature.
Uses negative feedback loops.


Function of the Posterior Pituitary (only peptide hormones)

Neuroendocrine signalling - secretory vesicles are released when signals from the hypothalamus comes.
Examples: Oxytocin and ADH


Function of the Anterior Pituitary (only peptide hormones)

True endocrine glands in the epithelial cell many hormones are created (neurosecretory cell); regulated by the hypothalamus.
Tropic Hormones act directly on the endocrine glands/tissues (TSH = thyroid, ACTH = adrenal cortex, FSH and LH = testes or ovaries)
Have a broad range of hormones that work on more than just the endocrine glands/tissues (growth hormone, prolactin, endophins - suppress pain receptors).


What are Growth Hormones?

They have a very broad effect; promotes protein synthesis and use of body fat for energy.
Promotes development and enlargement of all body parts, essential for normal growth and development. Overproduction of GH causes gigantism.