Chapter 5- The Endocrine System Flashcards
Insulin
Favors the transport of glucose into organs as well as the storage of excess glucose when blood glucose concentrations are high
Glucagon
Triggers the release of sugar stored and raises blood glucose concentration
Organs of endocrine system
Glands (they release hormones)
Hormones
Signaling molecules that are secreted directly into the bloodstream to travel to a distant target tissue
Hormone classifications
- Peptides
- Steroids
- Amino acid derivatives
Peptide hormones
Bind to membrane-bound receptors to initiate a signal cascade, using secondary messengers (cAMP, IP3, and calcium). Effects are usually rapid and short-lived. Peptides are water soluble so they can just flow through the blood stream
Adenylate Cyclase
Raising or lowering the levels of cAMP accordingly
Protein kinase A
Phosphorylates transcription factors like cAMP, it can modify other enzymes as well
Steroid hormone production
Derived from cholesterol (nonpolar, so can cross cell membrane) and are produced primarily by the gonads and adrenal cortex
Mechanism of steroid hormones
Bind to intracellular (in cytosol) receptors and function by binding to DNA to alter gene transcription. Slower and longer lasting change (ex: estrogen and testosterone)
Albumin
Nonspecific protein carrying steroid hormones (need to be taken cause not water soluble)
Amino acid derivative hormones
Derived from one or two amino acids with some modifications and include epinephrine norepinephrine and thyroxine
Catecholamines
Find 2G protein coupled receptors well Fairoyal hormones bind intracellularly examples are epinephrine and norepinephrine
Mechanism of epinephrine and norepinephrine
Extremely fast onset but are short-lived like peptide hormones think of an adrenaline rush
Mechanism of Thyroxine and triiodothyronine
Slower on set but longer duration like steroid hormones they regulate metabolic rate over a long period of time
Direct hormones
Secreted then asked directly on the target tissue for example insulin
Tropic hormones
Require intermediary to act, do not cause direct changes and physiology. stimulate the production of another hormone buy another endocrine gland that acts on these target tissues they typically originate in the brain and anterior pituitary gland
List of endocrine organs
H-TAG 4P (#4P)
Hypothalamus, thyroid, adrenal glands, gonads, pituitary, parathyroid, pancreas, pineal gland
Hypothalamus
Bridge between nervous and endocrine systems. regulates the pituitary gland through tropic hormones and paracrine release of hormones into a portal system that directly connects the two organs
interactions between hypothalamus and anterior pituitary gland
hypothalamus secretes hormones into the hypophyseal portal system (blood vessel system that directly connects the two) then stimulates release of other hormones from anterior pituitary
hypophysis
alternative term for pituitary
4 hormones released by hypothalamus to anterior pituitary
- Gonadotropin-releasing hormone (GnRH)
- Growth hormone-releasing hormone (GHRH)
- Thyroid-releasing hormone (TRH)
- Corticotropin-releasing factor (CRF)
if the hypothalamus releases Gonadotropin-releasing hormone (GnRH)… what does the anterior pituitary release?
Follicle-stimulating hormone (FSH) and luteinizing hormone (LH)– act on the gonads (testes and ovaries)
if the hypothalamus releases Growth hormone-releasing hormone (GHRH)… what does the anterior pituitary release?
growth hormone (GH)
if the hypothalamus releases Thyroid-releasing hormone (TRH)… what does the anterior pituitary release?
thyroid-stimulating hormone (TSH) which promotes the release of T3 and T4
if the hypothalamus releases Corticotropin-releasing factor (CRF)… what does the anterior pituitary release?
adrenocorticotropic hormone (ACTH) which then causes the adrenal cortex to increase cortisol levels in the blood. cortisol acts through negative feedback to prevent hypothalamus from releasing CRF and anterior pituitary from releasing ACTH.
Prolactin-Inhibiting factor (PIF)
it is dopamine. released by the hypothalamus and causes a decrease in prolactin secretion. it is the absence of PIF that allows for prolactin to be released.
interactions between hypothalamus and posterior pituitary
No tropic hormones through hypophyseal portal system. neurons in hypothalamus send axons down pituitary stalk directly into posterior pituitary. this can release oxytocin and antidiuretic hormone.
oxytocin
hormone that stimulates uterine contractions during labor as well as milk letdown during lactation. may be involved in bonding behavior.
antidiuretic hormone (ADH) aka. vasopressin
increases reabsorption of water in the collecting ducts of kidneys (increases permeability of duct to water). secreted in response to increase plasma osmolarity/increased concentrations of solutes within the blood. results in increased blood volume and higher blood pressure.
products of anterior pituitary
FLAT (tropic hormones) PEG (direct hormones)
- Follicle-stimulating hormone (FSH)
- Luteinizing hormone (LH)
- Adrenocorticotropic hormone (ACTH)
- Thyroid-stimulating hormone (TSH)
- Prolactin
- Endorphins
- Growth hormone (GH)
Prolactin
stimulates milk production in mammary glands
endorphins
decrease perception of pain
growth hormone
promotes growth of bone and muscle by preventing glucose uptake in certain tissues and stimulates breakdown of fatty acids. increases availability of glucose for muscle and bone to use.
where does bone growth originate?
epiphyseal plates of bone. seal shuts during puberty
posterior pituitary
does NOT synthesize any of its own hormones. receives and stores ADH and oxytocin from the hypothalamus.
positive feedback
“spiraling forward” process with a definitive endpoint.
thyroid
controlled by anterior pituitary. setting basal metabolic rate (making energy production more or less efficient) and calcium homeostasis. mediates the first effect by releasing triiodothyronine (T3) and thyroxine (T4), whereas calcium levels are controlled by calcitonin.
T3 and T4 production and usage
iodination of tyrosine (amino acid) in the follicular cells of the thyroid. increased amounts lead to increased cellular respiration
hypothyroidism
caused by deficiency of iodine or inflammation of the thyroid. thyroid hormones are secreted in insufficient amounts or not at all. symptoms: lethargy, decreased body temp/respiratory rate/heart rate, cold intolerance, weight gain.
cretinism
developmental delay (can be a result of hypothyroidism) caused by deficiency in thyroid hormones
hyperthyroidism
excess of thyroid hormone. may result from a tumor or thyroid over-stimulation. increased activity level/body temperature/respiratory rate/heart rate, heat intolerance, and weight loss.
2 cell types in thyroid tissue
- Follicular cells- produce thyroid hormones
2. C-cells (aka. parafollicular cells)- produce calcitonin
calcitonin
Tones down Ca levels in the blood. decrease plasma calcium levels in 3 ways. increased Ca excretion from kidneys, decreased Ca absorption from gut, increased storage of Ca in bone. (high levels of Ca in blood stimulate secretion of calcitonin from C-cells).
parathyroid glands
4 small pea-sized structures that produce parathyroid hormone (PTH). antagonistic hormone to calcitonin, raising blood calcium levels. it decreases excretion of Ca by kidneys, increases absorption of Ca in gut (via Vitamin D), and increases bone resorption– freeing up Ca.
Parathyroid hormone (PTH) and Vitamin D
PTH activates vitamin D, required for absorption of Ca and phosphate in the gut. overall effect of PTH is a significant increase in blood Ca levels with little effect on phosphate.
adrenal cortex
located on top of kidneys. secretes corticosteroids (steroid hormones that can be divided into three functional classes: glucocorticoids, mineralocorticoids, and cortical sex hormones)
glucocorticoids and 2 examples
regulate glucose levels and affect protein metabolism. (ex: cortisol and cortisone) raise blood glucose by increasing gluconeogenesis and decreasing protein synthesis. can also decrease inflammation and immunologic responses.
cortisol
stress hormone. increases blood sugar and provides ready source of fuel in case the body must react quickly to a dangerous stimulus.
what controls glucocorticoid release?
CRF from hypothalamus promotes release of ACTH from anterior pituitary which promotes release of glucocorticoids from the adrenal cortex
mineralocorticoids
used in salt and water homeostasis. most profound effects on the kidneys. (ex: aldosterone)
aldosterone
increases sodium reabsorption in the distal convoluted tubule and collecting duct of the nephron. water follows Na cations in bloodstream increasing blood volume and pressure. (plasma osmolarity stays the same). also decreases reabsorption of K and H in same segments of the nephron, promoting their excretion in the urine.
what controls aldosterone release?
renin-angiotensin-aldosterone system. Decreased blood pressure causes juxtaglomerular cells of kidney to secrete renin which activates angiotensinogen to angiotensin I. This is then converted into angiotensin II by angiotensin-converting enzyme (ACE) in the lungs. Angiotensin II stimulates the adrenal cortex to secrete aldosterone. then when bp is restored it will stop being released.
cortical sex hormones
adrenal glands also makes androgens and estrogens. more sensitive in females cause for men its mainly in the testes.
functions of corticosteriods
3S’s
- Salt –> mineralocorticoids
- Sugar –> glucocorticoids
- Sex –> cortical sex hormones
adrenal medulla
inside of adrenal cortex. production of sympathetic hormones (ex: epinephrine and norepinephrine– both catecholamines). specialized cells here can secrete compounds directly into circulatory system.
epinephrine and norepinephrine
E- can increase breakdown of glycogen to glucose (glycogenesis) in both liver and muscle. also increases basal metabolic rate
Both- increase heart rate, dilate bronchi, alter blood flow to supply by systems used in sympathetic response.
pancreas
both exocrine (secrete substances directly into ducts, produces many digestive enzymes) and endocrine functions (small groups of hormone-producing cells are grouped together into islets of Langerhans throughout the pancreas).
Islets of Langerhans
in pancreas. 3 distinct type of cells.
- alpha- secrete glucagon (secreted when glucose is low)
- beta- secrete insulin (antagonistic to glucagon)
- delta- somatostatin (inhibitor of both insulin and glucagon secretion)
insulin
induces muscle and liver cells to take up glucose and store it as glycogen for later use
hypoglycemia
too much insulin (too little glucose in blood), low blood glucose concentration
diabetes mellitus
underproduction/ insufficient secretion/ insensitivity to insulin. clinically called hyperglycemia (excess glucose in blood)
counterregulatory hormones
hormones that raise blood glucose levels
polyuria
increased frequency of urination
polydipsia
increased thirst
type 1 vs type 2 diabetes mellitus
1- insulin dependent. autoimmune destruction of B-cells of pancreas
2- noninsulin dependent. receptor level resistance to effects of insulin. partly due to lifestyle. only need insulin when body cant control glucose levels.
pineal gland
located deep in brain. secretes melatonin, involved in circadian rhythms. decrease in light (info from retina) leads to melatonin release (makes you sleepy)
other organs that are capable of endocrine signaling
- gastrointesstinal tract
- kidney- erythropoietin (stimulates bone marrow to increase production of red blood cells-reythrocytes)
- heart- atrial natriuretic peptide (help regulate salt and water balance, increases volume of urine, antagonistic to aldosterone b/c it lowers blood pressure and volume)
- thymus- thymosin (important for proper T-cell development and differentiation)
acromegaly
enlargement of small bones in extremities and of certain facial bones, such as the jaw.
how are oxytocin and ADH similar
both peptide hormones produced by hypothalamus and released by pituitary
