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Terms in this set (74)
Produces hormones that help maintain homeostasis and regulate reproduction and development. A hormone is a chemical messenger produced in one part of the body that affects target cells in another part of the body
Endocrine vs exocrine glands
Endo - synthesize and secrete chemical substances called hormones directly into the circulatory system. Exo - such as gallbladder, secrete substances transported by ducts
3 characteristics of hormones
1. Transported in the body through blood
2. Minute amounts of hormones can have a significant affect on target cells
3. Hormones may be steroids, peptides, or modified amino acids
What part of the brain plays a big part in the endocrine system
Forebrain and hypothalamus
What kind of cells link the hypothalamus to the pituitary gland?
What is the function of neurosecretory cells?
Secrete hormones into blood such as ADH, oxytocin
What are the two halves of the pituitary gland?
What else is the pituitary gland known as?
Posterior and anterior
What hormones are produced by the posterior pituitary?
ADH (anti-diuretic hormone) and oxytocin
What hormones are produced by the anterior pituitary?
Releasing hormones are produced by neurosecretory cells in the hypo and secreted into the blood and this blood flows directly to the anterior pituitary where the releasing hormones stimulate the release of TROPIC HORMONES produced by the anterior pituitary.
Two parts of the adrenal gland
Adrenal cortex and adrenal medulla
Lies on top of the kidney
What is the master gland and what is it controlled by?
Pituitary, controlled by the hypothalamus
Among the cells of the pancreas that produce digestive enzymes, there are bundles of cells called _________
Islet of Langerhans
What two kinds of cells are in the islet of Langerhans?
Alpha cells and beta cells
Beta cells secrete, when?
Insulin. When the concentration of blood glucose rises (after eating)
Alpha cells secrete, when?
Glucagon. When the concentration of blood glucose drop (during exercise)
What does insulin do?
Stimulates the liver and most other body cells to absorb glucose
What does glucagon do?
Stimulates the body to release glucose
Hormone that increases Ca2+ in the blood? What hormone has the opposite effect?
Parathyroid hormone (PTH) from the parathyroid glands increases Ca2+ in the blood by stimulating Ca2+ reabsorption in the kidney and Ca2+ release from the bones.
Opp effect: Calcitonin
WHat are the two methods by which hormones trigger activities in target cells?
Steroid or peptide
Hormones can be classified into two major groups: peptide hormones and steroid hormones and two ways to be affected, via extracellular receptors or intracellular receptors
Steroid hormone method?
Diffuses through the plasma membrane, through the cytoplasm, and into the nucleus. The hormone binds to a receptor protein in the nucleus and the receptor protein, in turn, activates a portion of the DAN that turns on specific genes
○ Lipid derived
○ Examples are estrogen and aldosterone
○ Produced by the testes, ovaries, placenta, and adrenal cortex and because they are lipid soluble, they can cross the phospholipid bilayer and enter their target cells directly in order to bind to specific receptor proteins in the cytoplasm
○ Then enters the nucleus and directly activates the expression of specific genes by binding to the receptors on the chromatin, inducing a chance in mRNA transcription and protein synthesis
Peptide hormone method
The hormone binds to a receptor protein on the plasma membrane of the cell (aka receptor endocytosis). The receptor protein, in turns, stimulates the production of one of the following second messengers: 1) cyclic AMP 2) inositol triphosphate
examples are ADH and insulin
○ Act as first messengers
○ Bind to specific receptors on the surface of their target cells, and trigger a series of enzymatc reactions within each cell, the first of which may be the conversion of ATP to cyclic adenosine monophosphate
○ Cyclic AMP acts a second messenger, relaying messages from the extracellular peptide hormone to cytoplasmic enzymes and initiating a series of reactions and this is called cascade effect (each step, the hormone's effects are amplified)
§ Cyclic AMP activity is inactivated by the cytoplasmic enzyme phosphodiesterase
What is cyclic AMP and IP3 produced from?
What do CAMP and IP3 do?
cAMP triggers an enzyme that generates specific cellular changes and IP3 triggers the release of Ca2+ from the endoplasmic reticulum, which in turn activates enzymes that generate cellular changes
Where are the adrenal glands located?
Located on top of the kidneys
Adrenal cortex - stimulated by 1? (from the anterior pituiary), producing a dozen steroid hormones and this is collectively known as 2? and when these are in the bloodstream they are bound to transport proteins called 3?
2. adrenocortical steroids / corticosteroids
Three major classes of transcortins?
3. Cortical sex hormones
cortisol and cortisone = glucose regulation and protein metabolism
raise blood glucose levels by promoting protein breakdown and gluconeogensis and decreasing protein synthesis
increase plasma glucose levels and are antagonistic to the effects of insulin
Release amino acids from skeletal muscle as well as lipids from adipose tissue
Aldosterone regulate plasma levels of sodium and potassium and the total extracellular volume
Does this by causing active reabsorption of sodium and passive reabsorption of water in the nephron of the kidney which results in an increase in blood volume and blood pressure
Excess production of aldosterone results in excess retention of water with hypertension (high blood pressure)
Stimulated by angiotensin II and inhibited by ANP (atrial natriuretic peptide)
Cortical sex hormones
adrenal cortex secretes androgen (male sex hormone) in both male and females (ex: androstenedione and dehydroepiandrosterone).
produces epinephrine (adrenaline) and norepinephrine (noadrenaline), both belonging to amino acid derived compounds called catecholamines
increases the conversion of glycogen to glucose in liver and muscle tissue, causing an increase in blood glucose levels and an increase in the basal metabolic rate
Also, inhibits other functions such as digestion that are not immediately important for survival
Both ___________ will increase the rate and strength of heartbeat and dilate and constrict blood vessels in such a way as to increase the blood supply to the skeletal muscles
Also promote the release of lipids by adipose tissue.
norepinephrine and epinephrine
Fight or flight, elicited by the?
sympathetic nervous system
What connects the pituitary to the hypothalamus
What is the difference between direct and tropic hormones?
Direct = directly act on their target organs
Tropic hormones = stimulate other endocrine glands to release hormones
What are two examples of direct hormones?
Growth hormone and prolactin
Milk production in female mammary glands
Growth hormone (GH, somatotrophin)
promotes bone and muscle growth, and protein synthesis and lipid mobilization and catabolism
In children, deficiency or overproduction can lead to dwarfism or gigantism. The overproduction causes acromegaly - disproportionate overgrowth of bone
What are some examples of tropic hormones?
TSH / Thyroid stimulating
stimulates the thyroid gland to synthesize thyroid hormones, including thyroxine
ACTH / Adrenocorticotrophic hormone
stimulates the cortex to synthesize and secrete glucocorticoids and is regulated by the corticoreleasing factor (CRF)
LH / Luteinizing hormone
stimulates ovulation and maintenance of the corpus luteum and is also responsible for regulating progesterone in women. In men, it stimulates the production of testosterone by the interstitial cells
FSH / Follicile stimulating hormone
causes maturation of ovarian follicles which in turn secrete estrogen and in men, it stimulates the maturation of the seminiferous tubules and sperm production
MSH / Melanocytes stimulating hormone
secreted by the intermediate lobe of the pituitary
neurotransmitters with pain relieving properties
secreted during childbirth increases the strength and frequency of uterine muscle contractions and is also induced by suckling, stimulates milk secretion in mammary glands
ADH / Antidiuretic hormone
increases the permeability of the nephron's collecting duct to water, promoting water reabsorption and increasing blood volume, increasing blood pressure.
- Part of the forebrain and located above the pituitary gland
Receives neural transmissions from other parts of the brain and from peripheral nerves that trigger specific responses from its neurosecretory cells, which regulate the p. gland secretions via negative feedback mechanisms and through the actions of inhibiting and releasing hormones
What is the interaction of the hypothalamus with the anterior pituitary
GnRH stimulates the anterior pituitary to secrete FSH and LH
Releasing hormones are secreted into the hypothalamic-hypophyseal portal system and blood from the capillary bed in the hypothalamus flows through a portal vein into the anterior pituitary, where it diverges into a second capillary network, so releasing hormones can immediately reach the anterior pituitary
What is the interaction of the hypothalamus with the posterior pituitary?
Neurosecretory cells in the hypo synthesize oxytocin and ADH and transport them via their axons to the posterior pituitary for storage and secretion
What stimulates the anterior pituitary to secrete FSH and LH?
Thyroid affects what?
Affect function of nearly every organ in the body and are essential for growth and development in children, and increase the rate of metabolism throughout the body and metabolic stability in adults
What are the thyroid hormones? Are formed by which glycoprotein?
Thyroxine T4 and triiodothyronine T3
Formed by thyroglobin, which is synthesized in the thyroid cells
Which is more potent? T3 or T4? And by how much? Transported by what? Bound or unbound?
T3 is 5x more potent than T4. Transported via plasma proteins. 99.5% are bound, but it needs to be unbound to enter the cell and elicit a cellular response
Where is T4 and T3 made? Converted to? By which enzyme? And where is it found?
All of T4 is made in the thyroid gland, but only 20% of T3 is
The majority of T3 made is converted to T4 by the enzyme 5'-monodeiodase, found in the peripheral tissue
Hypothyroidism. What's it called in infants?
thyroid hormones are undersecreted or not secreted at all and common symptoms are slowed heart rate, respiratory rate, fatigue, cold intolerance, and weight gain (in infants, called cretinism)
overstimulated, resulting in oversecretion with includes increased metabolic rate, feelings of excessive warmth, profuse sweating, palpitations, weight loss, protruding eyes
In both hyper and hypothyroidism, a bulge forms...whats it called?
What kind of functions does the pancreas do? Exo or endo? Performed by what kind of cells?
○ Exocrine function is performed by the cells that secrete digestive enzymes into the small intestine via a series of ducts
Endocrine is performed by the islets of Langerhans, composed of alpha and beta cells
secrete glucagon (absorb glucose)
□ Stimulates protein and fat degregation, the conversion of glycogen into glucose and gluconeogenesis, all of which serve to increase blood glucose levels
Antagonistic to insulin
secrete insulin (release glucose)
□ Insulin is secreted in response to high blood glucose concentration, stimulating the uptake of glucose by muscle and adipose cells and the storage of glucose as glycocgen in muscle and liver cells, thus lowering blood glucose cells
□ Also stimulates the synthesis of fats from glucose and the uptake of amino acids
□ Antagonistic to glucagon and the glucocorticoids
□ Underproduction leads to diabetes mellitus, hyperglycemia (high blood glucose levels)
Diabetes is the most common endocrine disorder
What is the most common endocrine disorder?
Kidneys produce ???? when blood volume falls? And what does it do? What does it stimulate
Renin and it converts the plasma protein angiotensinogen to angiotensin I and this is converted into angiotensin II which stimulates adrenal cortex to secrete aldosterone
What does aldosterone do?
helps to restore blood volume by increasing sodium reabsorption by the kidneys, leading to an increase in fluid retention, removing the initial stimulus for renin production
Also produce erythropoietin (EPO) which controls the production of RBC, and the hormone is produced primarily in the kidneys
When aldosterone helps produce erthropoietin (EPO, what happens?
§ Stimulation of the stem cells to differentiate into rubriblasts (least mature erthryocytes)
§ Increased rate of mitosis
§ Increased release of reticulocytes from bone marrow
Increased hemoglobin (HgB) formation, which results in the critical HgB concentration necessary for RBC maturity to be reached at a more rapid rate
What are the gastrointestinal hormones?
Released by the stomach when food is ingested, which stimulates the glands to secrete HCL in response to food in the stomach and secretion of pancreas
Tiny structure at the base of the brain that secretes melatonin and the role is unclear, but believed to be involved in the regulation of the circadian rhythms (physiological cycles lasing approx 24 hours). Regulated by light and dark. Antagonist to MSH
released by the small intestine in response to the presence of fats and causes the contraction of gallbladder and the release of bile into the small intestine. Bile helps with the emulsification and digestion of fats
released by the small intestine when acidic chyme enters from the stomach, and it stimulates the secretion of an alkaline bicarbonate solution from the pancreas that neutralizes the acidity of chyme
What secretes melatonin?
What does the pineal gland at antagonist to?
ADH and insulin are examples of what type of hormone?
Estrogen and aldosterone are examples of what kind of hormones?
Steroids (lipid soluble)