The Endocrine System Flashcards
What is the endocrine system?
A series of organs and glands that work together to synthesize, store and secrete different hormones for a variety of purposes
What are the functions of the endocrine system?
*Play a key role in maintaining homeostasis by regulating things like: smooth muscle, cardiac muscle, alter metabolism, reproductive processes, and circadian rhythms
* Plays a major role in the developmental changes that occur during puberty
How does the nervous system control bodily functions?
by action potentials and the release of
neurotransmitters
How does the endocrine system control bodily functions?
releases chemical mediators to regulate body systems called hormones
What is a hormone?
a molecule released by an organ or gland that has an effect on tissues or cells somewhere within the body. Usually carried to the target site via the blood stream.
How do neurotransmitters and hormones release their effects?
binding to receptors on or in a target cell (lock and key)
True or False:
Some chemicals in the body can act as both neurotransmitters and hormones
True:
Depending on where they are released.
Ex. norepinephrine
Are responses of the endocrine system typically faster or slower than the nervous system?
Slower
Do responses of the endocrine system typically last longer or shorter than the nervous system?
Longer
True or False:
It is common for both the nervous system and endocrine system to work together to regulate certain functions
True:
Ex. The nervous system can inhibit or stimulate the release of certain hormones
What is an exocrine gland?
Secretes products into ducts that carry their secretions into body cavities, the lumen of an organ, or to the outer surface of the body
What is an endocrine gland?
Secrete hormones into interstitial fluid, where they then diffuse into the circulatory system
True or False:
The endocrine system is heavily reliant on the cardiovascular system for distribution
True:
The cardiovascular system/circulatory system plays a key roll in hormone distribution, endocrine glands are highly vascular
What are the 5 endocrine glands?
-Pituitary
-Thyroid
-Parathyroid
-Adrenal
-Pineal
What are the endocrine organs/tissues?
-Hypothalamus
-Thymus
-Pancreas
-Ovaries/testes
-Kidneys
-Stomach
-Liver
-Small intestine
-Skin
-Heart
-Adipose tissue
-Placenta
What are hormone receptors?
For a hormone to exert its effect on a given cell or tissue, it must bind to a specific hormone target receptor designed to accept that hormone (lock and key)
What are hormone receptors made of?
Made up of proteins that are constantly being synthesized and broken down as needed
What occurs in down-regulation?
excess exposure to a hormone will reduce the amount of target cell receptors (target cells are less sensitive to the hormone)
What occurs in up-regulation?
hormone deficiency may increase the amount of target cell receptors (makes the target cell more sensitive to the hormone)
What are circulating hormones?
secreted by glands/tissues/organs into interstitial fluid and then diffuse into blood
What are local hormones
act locally on neighboring cells or on the same cell that secreted them without entering the bloodstream
What are paracinres?
Local hormones that act on neighboring cells
What are autocrines?
Local hormones that act on the cell that secreted it
Hormones are divided into which two categories?
Lipid-soluble and water-soluble
What are some lipid soluble hormones?
-steroid hormones
-thyroid hormones
-nitric oxide (NO)
What are some water soluble hormones?
-Amine hormones
-Peptide and protein hormones
-Eicosanoids (Prostaglandins and Leukotrienes)
How do water soluble hormones circulate in the blood?
Independently
How do most lipid soluble hormones circulate in the blood?
By binding to a transport protein
True or False:
Hormones always have the same effect regardless of where on the target cell it binds to
False:
Hormones can have an entirely different effect depending on where on the target cell it binds to.
Ex. Insulin stimulates glycogenesis in the liver cells and synthesis of triglycerides in adipose tissues
Where do lipid-soluble hormones bind to target receptors?
Within a target cell (can pass through lipid bilayer)
Where do water-soluble hormones bind to target receptors?
on the plasma membrane of target cells (cannot pass through lipid bilayer)
How do lipid-soluble hormones take action?
- Lipid-soluble hormone is released from a transport protein, diffuses from the blood to interstitial fluid and through lipid bilayer of cell
2.Hormone binds to target cell and activates receptors (turns genes on or off)
3.New mRNA forms, directs synthesis of new protein (often an enzyme)
4.Newly formed proteins alter cell activity and cause the responses typical of that hormone
How do water-soluble hormones take action?
- Water soluble hormone diffuses from the blood, to the interstitial fluid and binds to its receptor on the outer surface of the target cell
- Activation of the receptor triggers a process that creates a secondary messenger (Ex. cAMP)
- Process involving different types of proteins continues to produce different physiological response
- An enzyme called phosphodiesterase inactivates cAMP
Why do water-soluble hormones not require high concentrations to induce their effects?
Because of the exponential chain reaction that occurs within the cell when a hormone binds to the target receptor on the plasma membrane
The responsiveness of a target cell to a hormone depends on which 3 factors?
- Hormone concentration in the blood
- Abundance of hormone receptors in or on the target cell
- Influences exerted by other hormones
What is a synergistic effect?
Two hormones working together create greater results
What is a permissive effect?
One hormone increases the effect of another hormone
What is an antagonistic effect?
Two hormones oppose each other’s actions
True or False:
The release of most hormones occurs in short bursts, with little or no secretion between bursts
True
Secretion is regulated in which3 different ways (mostly via negative feedback)?
-Signals from the nervous system
-Chemical changes in the blood
-Other hormones
The hypothalamus is a major link between which systems?
The nervous and endocrine systems
What is the pituitary gland?
A small spherical gland that attaches to the base of the hypothalamus
What are the two anatomically and functionally separate portions of the pituitary gland?
The anterior pituitary and posterior pituitary
What hormones are secreted by the anterior pituitary gland?
-Human growth hormone (hGH)
-Thyroid Stimulating Hormone (TSH)
-Adrenocorticotropic Hormone (ACTH)
-Melanocyte Stimulating Hormone (MSH)
-Follicle-Stimulating Hormone (FSH)
-Luteinizing Hormone (LH)
-Prolactin (PRL)
What does Human Growth Hormone (hGh) do?
Stimulates general body growth and regulates aspects of metabolism
What does thyroid stimulating hormone (TSH) do?
Controls the secretions and other activities of the thyroid gland
What does Adrenocorticotropic Hormone (ACTH) do?
Stimulates the adrenal gland to secrete glucocorticoids (cortisol)
What does Melanocyte Stimulating Hormone (MSH) do?
Involved in protecting skin from UV, pigmentation, and appetite
What does Follicle-Stimulating Hormone (FSH) do?
Men: stimulate the testes to produce sperm
Women: simulate ovaries to mature oocytes and to secrete estrogen
What does Luteinizing Hormone (LH) do?
Women: triggers ovulation and the secretion of progesterone
Men: stimulates the testes to secrete testosterone
What does Prolactin (PRL) do?
Initiates milk production in the mammary glands
Which releasing hormones does the hypothalamus secrete to stimulate secretion of anterior pituitary hormones?
-Growth Hormone-Releasing Hormone (GHRH)
-Tyrotropin-Releasing Hormone (TRH)
-Corticotropin-Releasing Hormone (CRH)
-Prolactin-Releasing Hormone (PRH)
-Gonadotropin-Releasing Hormone (GnRH)
The hypothalamus secretes which inhibiting hormones, which suppress secretion of anterior pituitary hormones?
-Growth Hormone-Inhibiting Hormone (GHIH)
-Prolactin-Inhibiting Hormone (PIH)
What is the release of anterior pituitary hormones also regulated by?
Negative feedback systems, sensors in the blood monitor hormone concentrations
True or False:
The posterior pituitary does not synthesize any hormones
True:
Instead of synthesizing it’s own hormones, it stores and releases them
Which hormones are secreted by the posterior pituitary?
-Oxytocin
-ADH
What does Oxytocin do?
During/after delivery:
-Enhances contractions of the uterus
-Stretching of the cervix stimulates its release, and uterine contractions stimulate further release
-Positive feedback loop
After delivery:
-stimulates milk ejection (“let down”)
What does Antidiuretic Hormone (ADH) (aka vasopressin) do?
-Stimulates reabsorption of H2O and decreases H2O loss from sweating
-Arteriole vasoconstriction (increased BP)
-Increased blood osmolarity/decreased blood volume trigger its release
-Target tissues include kidneys, smooth muscle in arterioles
What inhibits and stimulates ADH secretion?
-Alcohol inhibits ADH secretion
-Many drugs and stressors stimulate secretion
Where is the thyroid gland located?
Inferior to the larynx and divided into two lobes
What hormones does the thyroid gland produce and secrete?
-Calcitonin (CT)
-Thyroid Hormones - T3 and T4
What does Calcitonin (CT) do?
-Helps to regulate calcium homeostasis via negative feedback
-High blood calcium levels stimulate release
What do the Thyroid hormones T3 and T4 do?
-Increases the speed of cellular metabolism
-Increases production and use of ATP
-Thermoregulatory, ATP production and use generates heat
-Enhance actions of catecholamines (epi/NE)
-Up-regulate β-adrenergic receptor
-Promote development and growth of nervous and skeletal tissue
How are hormones in the thyroid gland regulated?
-Thyroid hormone secretion is regulated by low blood levels of T3 and T4
-Stimulates hypothalamus to secrete thyrotropin-releasing hormone (TRH) which triggers the anterior pituitary gland to secrete thyroid stimulating hormone (TSH) into circulation
-TSH stimulates thyroid production and release of T3 and T4 until the metabolic rate returns to normal and elevated T3 levels inhibit the release of TRH and TSH
Where are the parathyroid glands located?
Found embedded in the posterior surface of the lateral lobes of the thyroid
What does the parathyroid glands secrete?
Parathyroid Hormone (PTH)
What does the Parathyroid Hormone (PTH) do?
-Regulates Ca2+, Mg2+ and HPO42- ions in the blood
-Promotes bone release of Ca2+ and HPO42- into the blood
-Slows the renal loss of Ca2+ and Mg2+ while promoting loss of HPO42-
-Promotes renal formation of calcitriol (VitD) which increase GI absorption of Ca2+, Mg2+ and HPO42-
-Increases blood Ca2+ and Mg2+ and decreases HPO42-
Where are the adrenal glands located?
The pair of adrenal glands lie superior to each kidney
The adrenal glands are structurally and functionally divided into which two regions?
Adrenal cortex (90% of the gland) and adrenal medulla
What does the adrenal cortex produce?
-Glucocorticoids (cortisol)
-Androgens
-Aldosterone
What does the adrenal medulla produce?
-Epinephrine
-Norepinephrine
-Dopamine
What does the Renin-Angiotensin-Aldosterone System (RAAS) do?
-Regulates homeostasis of Na+ and K+
-Major effect on blood pressure and blood volume
-Promotes excretion of H+ in the urine
Where is renin secreted?
Low blood pressure triggers the juxtaglomerular cells to secrete renin
What is angiotensinogen?
Angiotensinogen is a plasma protein produced by the liver
How does the Renin-Angiotensin-Aldosterone system work?
-Renin converts angiotensinogen into angiotensin I
-Angiotensin I travel to the lungs, where angiotensin converting enzyme (ACE) converts it to angiotensin II
-Angiotensin II stimulates the adrenal cortex to secrete aldosterone
-In the kidneys, aldosterone promotes Na+ (and H2O) reabsorption, and inhibits the reabsorption of K+ and H+
-Causes increased blood volume (BP) and decreased acidosis
-Angiotensin II also stimulates vasoconstriction in arterioles (increased BP)
What other than angiotensin II stimulates the secretion of aldosterone?
Increased K+ concentration
What are the glucocorticoids secreted by the adrenal cortex?
-Cortisol (95% of all glucocorticoid activity)
-Cortisone
-Corticosterone
What are the effects of glucocorticoids?
-Increased rate of protein breakdown into amino acids
-Gluconeogenesis
-Lipolysis
-Depression of immune response (in high doses): used in organ transplants
-Inhibit WBCs in inflammatory responses: slow wound repair (can be used to treat chronic inflammation)
Stress response
This promotes the release of adrenocorticotropic hormone (ACTH) from the anterior pituitary - adrenal release of glucocorticoids
What is gluconeogenesis?
Conversion of amino acids or lactic acid into glucose
What is lipolysis?
Breakdown of triglycerides (from adipose) into fatty acids
What happens in stress response?
Make blood vessels more sensitive to vasoconstricting hormones, increased fatty acids for more energy (fight or flight)
What does low blood levels of glucocorticoids stimulate the release of?
Corticotropin-releasing hormone (CRH) from the hypothalamus which promotes the release of adrenocorticotropic hormone (ACTH) from the anterior pituitary
What are androgens?
Androgens are sex hormones in males and females
What androgen does the adrenal cortex secrete?
Dehydroepiandrosterone (DHEA)
What is the function of dehydroepiandrosterone (DHEA)?
Females:
-promotes libido
-converted to estrogen
-promotes axillary and pubic hair growth during puberty as well as supports the prepubertal growth spurt
Males:
-promotes axillary and pubic hair growth during puberty
-supports the prepubertal growth spurt
-following puberty, testosterone outweighs DHEA making its effects negligible
What is the adrenal medulla composed of?
Composed of modified autonomic nervous system cells that cluster around large blood vessels
What is the release of adrenal medullary hormones stimulated by?
The autonomic nervous system
What are the two major hormones synthesized are secreted by the adrenal medulla?
-Epinephrine
-Norepinephrine (NE)
What are the functions of epinephrine and norepinephrine
-During stress, the hypothalamus stimulates the secretion of epi and NE which greatly augment the sympathetic response (fight or flight)
-+ve inotrope, +ve chronotrope, increase blood flow to the heart/liver/skeletal muscles, dilate a/w, increase BGL
What are the pancreatic islets/islets of Langerhans?
small clusters of endocrine tissue scattered amongst the exocrine cells
Each pancreatic islet contains which 4 types of hormone secreting cells?
-Alpha or A cell
-Beta or B cells
-Delta or D cells
-F cells
What do alpha or A cells secrete?
secrete glucagon (raises blood glucose)
What do beta or B cells secrete?
secrete insulin (lowers blood glucose)
What do delta or D cells secrete?
secrete somatostatin (inhibits insulin and glucagon release, slows absorption of nutrients in GI tract, inhibits secretion of GH)
What do F cells secrete?
secrete pancreatic polypeptide (inhibits somatostatin secretion, gallbladder contraction and secretion of pancreatic digestive enzymes
What does glucagon do?
acts on hepatocytes (liver cells) to speed up glycogenolysis and gluconeogenesis
What is glycogenolysis?
the conversion of glycogen into glucose
What levels would be considered hypoglycemia?
Adults < 4.0mmol/L, Peds < 3.0mmol/L
What does hyperglycemia stimulate the release of?
the release of insulin from the beta cells of the islet of Langerhans
What does insulin do?
acts on body cells to accelerate facilitated diffusion of glucose into cells, speeds up glycogenesis, increases uptake of amino acids by cells, speed up lipogenesis, slows glycogenolysis, and slows gluconeogenesis
What is glycogenesis?
conversion of glucose into glycogen
What is lipogenesis?
synthesis of fatty acids
What is glycogen?
glucose storage in the liver
Gonads are the organs that produce what?
That produce gametes (sperm in males, oocytes in females)
What do the ovaries produce?
-Produce estrogen and progesterone
-Along with FSH, LH they work together to: regulate the menstrual cycle, maintain pregnancy, and prepare the mammary glands for lactation
-Also promote breast enlargement and widening of the hips during puberty
What do the testes produce?
-Produce testosterone
-Regulates production of sperm
Stimulates facial hair growth and voice lowering during puberty
Where is the pineal gland located?
Attached to the roof of one of the ventricles of the brain (part of the epithalamus)
What does the pineal gland secrete?
Secretes melatonin - aids in sleep regulation
Where is the thymus located?
Behind the sternum and between the lungs
What does the thymus secrete?
Secretes a handful of hormones involved in the maturation of T cells
What are the two families of eicosanoids?
-Prostaglandins (PGs)
-Leukotrienes (LTs)
Thromboxane
a prostaglandin that vasoconstricts and promotes platelet aggregation
