Bio: Endocrinology Flashcards
Endocrine system
Means of internal communication, coordinating the activities of organ systems.
What do endocrine glands make?
Synthesize and secrete chemical substances called hormones directly into the circulatory system
Hormones two major groups
Peptide hormones and steroid hormones
Peptide hormones
Range from simple short peptides (AA chains) such as ADH to complex polypeptides such as inuslin
short lived. surface reptors. act via secondary messengers
What happens when peptide hormones bind to specific extracellular receptors
By binding to specific extracellular receptors on the surface of their target cells, they trigger a series of enzymatic rxns within each cell.
EACH STARTS WITH ATP TO cAMP
Cyclic AMP
acts as a secondary messenger and relays messages from extracellular peptide hormone to cytoplasmic enzymes, initiating a cascade effect in which the hormone’s effects are catalyzed
What inactivates cAMP
cytoplasmic enzyme phosphodiesterase.
Steroid hormones
ie estrogen and aldosterone
Lipid derived molecules with ring structure.
Because they’re lipid soluble, steroid hormones enter their target cells directly and bind to specific INTRACELLULAR RECEPTOR PROTEINS in the cytoplasm.
Intracellular receptor + Steroid hormone complex
receptor-hormone complex enters nucleus and activates expression of specific genes by binding to receptors on chromatin..
Induces a change in mRNA transcription and protein synthesis
Endocrine glands (12)
Pituitary Hypothalamus Thyroid Parathyroids Adrenals Pancreas Testes Ovaries Pineal Kidneys Gastrointestinal glands Heart Thymus
What determines the specificity of hormonal action
Presence of specific receptors on or in the target cells
Adrenal Glands
On top of kidneys.
Consist of adrenal cortex and adrenal medulla
Adrenal Cortex
With stress, ACTH stimulates adrenal cortexto synthesize and secrete the steroid hormones,, aka corticosteroids
Corticosteroids
Derived from cholesterol, includes glucocorticoids, mineralocorticoids, and cortical sex hormones
Glucocorticoids
Corticosteroids
Such as cortisol and cortisone
Involved in glucose regulation and protein metabolism.
Promote protein breakdown and use products in gluconeogenesis
Raise plasma glucose levels and are antagonistic to the effects of insulin
Mineralocorticoids
Particuarly aldosterone.
Regulate plasma levels of Na and K and the total extracellular water volume.
Aldosterone
Mineralocorticoid
Causes active reabsorption o sodium nd passive reabsorption of water in the nephron
Increases blood volume and blood pressure
Excess production of aldosterone = excess retention of water… HYPERTENSION
Cortical Sex hormones
Adrenal cortex secretes a little androgen (male sex hormone) in both M and F
androgen is made by testes.. physiologic effect of adrenal anrogens is small.
overproduction -> masculine
Adrenal Medulla
Produces epinephrine (adrenaline) and norepinephrine (noradrenaline) Both belong to AA derivedcopounds catecholaines
Epinephrine
Increase conversion of glycogen to glucose in liver and muscle tissue, causing a rise in blood glucose levels and basal metabolic rate.
Epinephrine and norepinephrine both do what?
increase the rate and strength of the heartbeatand they dilate and constrict blood vessels in a way as to increase blood supply sto skeletal muscle, heart, brain, while decreasing blood supply to kidneys, skin, and digestive tract
FIGHT OR FLIGHT
FIGHT OR FLIGHT
elicited by Sympathetic Nervous stimulation in response to stress
Epinephrine inhibits vegetative functions, like digestion.
both ep and norep are also NT
Control of adrenal hormones
Release of adrenal cortical hormones is controlled y ACTH
ACTH
hormone secreted by anterior pituitary gland
ACTH stimulates production of glucocorticoids and sex steroids.
Aldosterone production is controlled by reninangiotensin mechanism
Pituitary gland
small, tri-lobed gland lying at the base of the brain
Two main lobes, anterior and posterior are functionally distinct
Anterior Pituitary
synthesizes both direct hormones and tropic hormones
Regulated by hypothalamic secretions called releasing/inhibiting hormones or factors
Direct hormones
Directly stimulate their target organs
Growth hormones, prolactin, endorphins
Tropic hormones
Stimulate other endocrine glands to release hormones
ACTH, TSH, LH, FSH
Growth hormones
Direct hormone
GH, somatotropin
GH promotes bone and muscle growth. GH deficient = dwarf.
Overproduction = acromegaly
Prolactin
Direct hormone
Stimulate milk production and secretion in female mammary glands
Endorphins
Direct hormone
NT behaves like opioids providing and internal mechanism for pain relief and producing pleasure
ACTH
Adrenocorticotropic hormone
Stimualtes adrenal cortex to synthesize and secrete glucocorticoids and Is regulated by releasing hormone corticotrophin-releasing factor CRF
TSH
Thyroid stimulating hormone
Stimulates thyroid gland to synthesize and release thyroid hormones, thyroxine
LH
Luteinizing hormone
F -> stimulate ovulation and formation of corpus luteum which secretes progesterone and estrogen
M-> stimulate interstitial cells of testes to synthesize testosterone
FSH
Follicle stimulating hormone
F-> maturation of ovarian follicles, which secrete estrogen
M-> stimulates maturation of seminiferous tubules and sperm production
Posterior pituitary
doesn’t synthesize hormones
Stores and releases peptide hormones oxytocin and ADH, which are produced by neurosecretory cells of hypothalamus
Secretion occurs when action potentials descend fro hypothalamus in response to body signals
OXytocin
Posterior pituitary secretes
secreted during childbirth, increase strength and frequency of uterine muscle contractions. (+ feedback control) which releases more oxytocicn
Oxytocin secretion is induced by suckling, as it stimulates milk secretion in mammary glands
ADH or vasopressin
Antidiuretic hormone
Posterior pituitary secretes
ADH increases permeability of collecting duct in nephron to water, promo of water reabsorption and decreasing blood osmolarity by increasing blood volume
Secreted when plasma orsmolarity increases, as sensed by osmoreceptors in hypothalamus or when blood volume decreases, as sensed by baroreceptors in circulatory system.
Hypothalamus
in forebrain above pituitary gland
Receives NT from other parts of brain and peripheral nerves which trigger specific responses from its neurosecretory cells
Neurosecretory cells
regulate pituitary gland secretions via negative feedback mechanisms and through actions if inhibiting and releasing hormones
Interactions with Anterior Pituitary
hypothalamic releasing hormones stimulate or inhibit secretions of anterior pituitary
GnRH stimulates AP to secrete FSH and LH into hypothalamic hypophyseal portal system.
blood from capbed in hypothalamus flows through portal vein into AP, where it diverges into a second capillary network
What happens when plasma levels of adrenal cortical hormones drop?
Hypothalamic cells relsease aCTH releasing factor (ACTH-RF) into the portal system.
If plasma concentration of corticosteroids»_space; normal plasma level, steroids exert inhibitory effect on hypothalamus (- feedback)
Interactions with Posterior Pituitary
Neurosecretory cells in hypothalamus synthesize both oxytocin and ADH and transport via axons into PP for storage and secretion
Thyroid
bi-lobed structure located on the ventral surface of trachea. Produces and secretes thyroxine and triiodothyronine (thyroid hormones) and calcitonin
Thyroid hormones
Thyroxine andtriiodothyronine
T4 and T3. derived from iodination of Tyrosine
Need for growth and neurological development in children. Also increase rate of metabolism throughout the body.
Hypothyroidism
Thyroid hormones are undersecreted or not at all
Slowed heart rate and respiratory rate, fatigue, cold intolerance, weight gain. (in infants called creatinism) mental retardation and short stature.
Thyroid enlarges to bulge into a goiter
Hyperthyroidism
Overstimulated thyroids
increased metabolic rate, feelings of excessive warmth, profuse sweating, palpitations, weight loss, protruding eyes.
Thyroid enlarges to bulge into a goiter
Calcitonin
produced and secreted by Thyroid
Decreases plasma Ca2+ concentration by inhibiting release of Ca2+ from bone.
Calcitonin secretion is regulated by plasma Ca2+ levels
Antagonistic to parathyroid hormone.
Pancreas
Exocrine and endocrine organ
Exocrine function: performed by cells that secrete digestive enzymes into the small intestines via series of ducts
Endocrine function: performed by small glandular structures called islets of Langerhans, which are composed of alpha and beta cells
Alpha cells
produce and secrete glucagon
Beta Cells
Produce and secrete insulin
Glucagon
By alpha cells
Stimulates protein and fat degradation. Conversion of glycogen to glucose. Gluconeogensis.
All of these increase blood glucose levels.
Glucagon’s actions are largely antagonistic to those of insulin. Glucagon increases plasma glucose whereas insulin decreases it.
Insulin
Protein hormone secreted by pancreas in response to a high blood glucose concentration.
It stimulates uptake of glucose by muscle and adipose cells and the storage of glucose as glycogen in muscle and liver cells. Lowers blood glucose levels.
Stimulates synthesis of fats and from glucose and uptake of AA
Insulin’s actions are antagonistic to those of glucagon and glucocorticoids.
What else can increase plasma glucose?
GH Glucocorticoids, and epinephrine
Diabetes mellitus
Underproductionof insulin, or insensitivity to insulin, leads to it.
Characterized by hyperglycemia (high blood glucose levels)
Parathyroid glands
Four small, pea shaped structure in posterior surface of thyroid
Synthe and secrete parathyroid hormone, which regulates plasma Ca2+ concentration. PTH raises Ca2+ in blood by increasing bone resorption and deceasing Ca2+ excretion in kidneys.
PTH INCREASES Ca2+
Calcitonin decreases Ca2+
What happens when calcium in the bone bonds to phosphate?
BD of bone releasing Phosphate and Calcium.
Parathyroid hormone compensates for this by stimulating excretion of phosphate by the kidneys.
Kidneys
When blood volume decreases, kidneys make renin
Renin
When blood volume decreases, kidneys make renin which converts plasma protein angiotensinogen to angiotensin I. Angiotensin I is converted to angiotensin II, which stimulates the adrenal cortex to secrete aldosterone. Aldosterone restores blood volume by increasing sodium reabsorption at the kidney, leading to an increase in water.
Gastrointestinal hormones
ingested food stimulates stomach to release gastrin
Gastrin
carried to gastric glands and stimulates glands to secrete HCl in response to food in stomach. Secretion of pancreatic juice, exocrine secretion of pancreas, is under hormone control. secretin.
Secretin
released by small intestine when acidic food material enters the stomach.
stimulates secretion of alkaline bicarbonate solution from the pancrease, neutralizing chyme’s acidity
Cholecystokinin
Released from small intestine in response to presence of fats and cause the contraction of the gallbladder and release of bile into small intestine.
Bile digests fats
Cholecystokinin can travel to brain’s satiation center to indicate being full
Pineal gland
Tiny structure at the base of the brain that secretes melatonin.
Melatonin
Regulates circadian rhythms, physiological cycles lasting 24 hours.
Melatonin secretion is regulated by light and dark cycles in environment.
Plant hormones are primarily involved in the regulation o
Growth.
Produced by actively growing parts of the plant, such as the meristematic tissues in th eapical meristem offshoots and roots..
Also produced in young growing leaves and developing seeds
Auxins
associated with phototropism and geotropism
Phototropism
Tendency of shoots to bend to light.
light strikes tip of plant from a side, auxin supply on that side reduces.
illuminated side of the plant grows more slowly than the shaded side.
Asymmetrical growth in the cells of stem cause plant to bend toward light side.
Indoleacetic acid (auxin associated with phototropism)
Geotropism
Growth of portions of plants towards or away from gravity
Negative -> cause shoots to grow up away from gravity. if a plant is on its side, the shoot witll eventually turn up.
Gravity increases concentration of auxin on lower side of horizontally plaed plant, while the concentration on the upper side decreases. Unnequal distribution of auxins stimulates cells on the lower side to elongate faster than cells on the upper side, grow up.
Positive: roots grow towards the pul of gravity. horizontally placed roots have same auxin distribution as horizontally placed stems, but effect on root ells is opposite.
Cells exposed to hi conc of auxin are inhibited from growing. cells with lower concentration continue to grow. roots turn down.
Inhibition of lateral buds
auxins produced in terminal bud of aplant’s growing tip move downward in shoot and inhibit devo of lateral buds.
Auxins also initiate formation of lateral roots while inhibiting root elongation.
Gibberellins
stimulate rapid stem elongation, particularly in plants that don’t grow tall.
inhibit formation of new roots
Stimulate production of new phloem by cambium (auxin stiulate production of new xylem)
Terminate dormancy of seeds and buds.
induce biennial plants to flower
Kinins
promote cd
ratio of kkinetin to auxin is important in determining timing of differentiation of new cells. action of kinetin is enhanced with auxin
Ethylene
induces senescence. aging
Inhibitors
block cd and serve a role in growth regulation.
maintain dormancy in lateral buds and seeds of plants during autumn and winter. bd with time so that buds and seeds can be active in te growing season
Abscisic acid
Anti auxins
regulate activity of auxins
Indoleacetic acid oxidase regulates conc of indoleacetic acids.
increase in oncentration of indoleacetic acid increases the amount of indoleacetic acid oxidase produced.
