endocrine system Flashcards
endocrine system
glands of an organism that secrete hormones into the circulatory system so they can be carried to target organs
what are the functions of the endocrine system
- Regulate metabolism
- Control of food intake and digestion
- Regulation of ion levels
- Control of water balance
- Changes in heart rate and blood pressure
- Control of immune system function
- Control of reproductive functions
what are the characteristics of hormones
stability, communication, and distribution
stability
- Shorter half-lives are degraded by proteases inside a lysosome
- Modification to water-soluble hormones increases their half-lives
Communication – how do hormone initiate a response?
through binding to a receptor
Distribution – hormones need to be transported to a distant organ/tissue, how do they do that?
-Ability to be transported to target organs and tissues
-Do this through binding proteins
water-soluble hormones
- Bind to membrane bound receptors to initiate a response
- Shorter half life
- Levels change rapidly
- Regulates activities that have a rapid onset or short duration
- No binding protein, free hormone
lipid soluble hormones
- Small size, low solubility
- Binding protein, solubilizes hormone and protects it
- Bind to nuclear receptors
- Have a constant activity rate and longer half life
- Binding protein almost always
Which hormone can respond to rapid onset activities better? Water-soluble or lipid-soluble hormones? Why?
Water soluble hormones, their levels change rapidly and regulate activities that have a rapid onset
Describe the 3 patterns of hormone secretion
chronic, acute, episodic
Chronic
Maintenance of relatively constant concentration of hormone
* Ex is thyroid hormone
Acute
Changes dramatically and irregularly
* Insulin secretion
Episodic
Fairly regular intervals and concentrations
* Female reproductive hormones
how are humoral hormone secretions regulated
stimulated by molecules or metabolites, cells that secrete hormones have receptors for these substances
how are neural hormone secretions regulated
neural control via neurotransmitter
how are hormonal secretions regulated
hormone stimulate the secretion of other hormones
how does negative feedback control hormone secretion
hormone secretion is inhibited by the hormone itself once blood levels reach a certain concentration
how does positive feedback control hormone secretion
hormones stimulated by tropic hormone promote synthesis and secretion of tropic hormone
Why are receptors important to hormone signaling? How do they help regulate responses of cell to hormones
-Hormones act on target cells that have specific receptors for chemical signals
- Alter g protein signaling pathway by interaction with adenylate cyclase and activate second messengers
- Alter the intracellular activity
Different type of receptors that the water-soluble and lipid-soluble hormones binds to describe what happen when these hormones bind to the receptors and differentiate
- Nuclear receptor enhances the transcription of mRNA/protein synthesis
- Membrane-bound receptors enhances intracellular reaction
Which organ has both endocrine and exocrine glands?
pancreas
Oxytocin
- Stimulate uterine contraction during labor
-The love hormone
-Sperm movement
ADH
- Increase in blood osmolality and decrease in blood pressure
- enhances water permeability
what is the outcome of ADH
Decreases the amount of urine produced
what are tropic hormones
target other endocrine glands, regulated by hormonal stimuli
what are examples of tropic hormones
tsh, acth, fsh
what is the target of tropic hormones
endocrine glands
where are tropic hormones produced
anterior pituitary
what is the regulation of thyroid hormone secretion
the hypothalamic-pituitary-thyroid axis. Thyrotropin-releasing hormone is released from the hypothalamus and stimulates the synthesis and secretion of thyroid-stimulating hormone
What happen if someone is iodine deficient?
calcitonin
calcium homeostasis
what’s the target organ of calcitonin
Target tissue is bone and increases bone formation
Parathyroid hormone
- Composed of chief cells that secrete parathyroid hormones
- Organs involved: bone, kidneys and small intestine
regulation of calcium hormones
High calcium- inhibit PTH secretion
Low calcium- promote PTH secretion
- vit d helps in regulation of calcium levels
Synthesis of vitamin D, environmental factors that affect vitamin D synthesis
- Synthesized in the skin
- Picked up by vit d binding protein for transport in blood
- Helps with absorption of calcium
- Environmental: where you live and how much sunlight you get, time of year
Forms and sources of vitamin D
- Plants and animal products
- Sunlight
Digestion, transport, and activation of vitamin
- Enters the nucleus from the cytosol
- Binds to receptors
- Induces gene transcription
- Organs involved: liver and kidney
- Outcome of vitamin D deficiency
- Osteomalacia- softening of bones, mostly in children
- Loss of bone matrix
exocrine in the pancreas
pancreatic digestive juices
endocrine in the pancreas
consists of pancreatic islets
Role of insulin and glucagon in glucose homeostasis
*Beta cells secrete insulin
*Alpha cells secrete glucagon
*Insulin is a anabolic reaction and secreted when blood glucose is high
*Glucagon is a catabolic hormone and is secreted when blood glucose is low
Define and understand the mechanism of insulin resistance
*When cells stop responding to insulin
*Common in people with T2DM
Cholecystokinin (CCK)
*Hunger suppression
*Stimulates the release of pancreatic enzymes
*Stimulates gall bladder contraction
secretin
Pancreatic juice secreted into duodenum, decreases acidity
Which hormones are secreted by the stomach
gastrin and ghrelin
Gastrin
*Gastric secretion
*Stimulate gastric and intestinal motility
ghrelin
*Increases hunger
*Stimulates growth hormone secretion
- hunger hormone
What is the primary function of Somatostatin?
Endocrine off switch, inhibit release of GI hormones
somatostatin is released by which cells/location?
Stomach, small intestine and pancreatic delta cells
What is the action/outcome of somatostatin secretion?
- Inhibit release of GI hormones
- Slow gastric emptying and motility
- Reduce blood flow to intestine
Leptin is secreted by _______? Does it suppress or increase appetite?
- Secreted by adipose cells
- It decreases appetite
