9.3 Endocrine Flashcards
describe the thyroid gland
- largest endocrine gland-> lateral lobes conencted via isthmus
- FOllicle cells produce the glycoprotein thyroglobulin
- colloid (thyroglobulin and isodine) fills the lumen of the follicles
what are the effects of thyroid hormone
* major emtabolic hormone
- -TH is concerned with:
- glycose oxidation
- increasing metabolic rate
- heat production
- -TH plays a role in:
- maintaining blood rpessue
- regulating tissue growth
- developing skeletal and nervous sytems
- maturation and reprofuctive capabilities
What are the exceptions of the areas that are not affected by the thyroid gland
* will have an exam question
USTAT
uterus, spleen, testis, adult brain (role in neural development in younger kids), thyroid gland (doesnt target itself)
What are the 2 types of thyroid hormones
T4 - Thyroxine; two tyrosine molecules plus 4 iodine
T3 - Triiodothyronine; two tyrosines with 3 iodine
Synthesis
- Thyroglobulin (constains 134 tyrosine) is synthesized and discharged into the lumen, only hanful actually used
- I- taken into cell actively, oxidized to I2 and released into lumen
- thyroid perioxidase attached iodine to tyrosine, forming T1 (MIT) and T2 (DIT)
- thyroid peroxidase links togther to form T3 and T4
- Endocytosis of T3 and T4 are cleaves in lysoomes and diffuse into blodo stream
describe the transport and regulation of TH
which is mroe active
T4 and T3 bind to thyroxine binding globulins (TBGs or thyroxine binding protein, TBP) produced by liver
- both bind to target receptors but T3 is 5-10x more active
- peripheral tissues (target tiss) convert T4 -> T3 via deiodinase
- mechanisms of activity are simialr to sterioids
- hypothalamic thyroprotin-releasing hormone (TRH) can overcome the negative feedback
Describe Hypothyroidism
- symptoms include: low metabolic rate, lethargy, mental slugishmess
- Low T4 and possible T3 leads to higher THS (unless pituitaru problem)
- lack of I2 can lead to enlarges thyorid (goiter)
*tries to make more TH increases colloid space -> causes thyorid gland to grwo really big
what is cretinism
form of hypothyroidism found in infants
what is graves disease
- autoimmune disease that most commonly afects the thyorid, causes it to grow twice its size or more (goiter)
- symptoms include increased heartbeat, muscle weakness, dsiturbed sleep and iritability
- it can also affect the eyes, causing bulging (exophthalamos)
- abnormal antibodies that mimic TSH and continuously stimulate TH release (act and bind to thyroid gland)
what is calcitonin
- peptide hormone rpduced by parafollicular, or C-cells
- lowers blood Ca2+ in children and targets skeleton
- > inhibits osteoclast activity and release of Ca2+
- Stimulates Ca2+ incorporation into bone matrix
describe the parathyroid glands
- tiny glands embedded in the posterior aspect of the thyroid
- cells are arranged in cords containing oxyphyl and chief cells
- chief (principal) cells secrete parathyorid hormone (PTH) whihc reg Ca2+ balance in blood
what are the effects of parathyroid hormone
- stimulates osteoclasts
- Enhances the reabsorption of Ca2+ and the secretion of phosphate by the Kidneys
- promotes Vitmain D activation to calcitriol whihc increases Ca2+ abs of the intestine
*Cising Ca2+ in blood inhibits PTH release
describe the adrenal galnds
contains
adrenal medualla: neural tissue that acts as part of the sympathetic nervous system (SNS)
Adrenal cortex: releases steroid hormones called corticosteroids (>24)
what are the layers of the adrenal cortex and the corticosteroids produced at each layer
Zona glomerulosa - mineralocorticoids (mostly aldosterone)
Zona fasciculata - glucocorticoids (mostly cortisol)
Zona reticularis - gonadocorticoids (mostly androgens)
all steroids are derived from
cholesterol
estrogen synthesis, which form is most potent
E2 i the most potent
E1 (estrone) can make E2 (estradiol) or E3 (Estriol)
E2 can also be used yo make E3
describe mineral corticoids
- produced in Zona glomerulosa of adrenal cortex
- regualte electrolytes in extracellular fluids
Aldosterone most important mineralocorticoid
- > Maintains Na+ by reducing excretion of Na+ from the body
- > Stimulates reabsorption of Na+ by the kidneys
what stimulates teh secretion of aldosterone
Rising blood levels of K+
Low blood Na+
Decreasing blood volume or pressure
what methods regulate aldosterone
- Renin-angiotensin mechanism
- angiostensin II stimulates aldosterone release
- Inc plasma K+ (Na+), directly influences the zona glomerulosa cells
- ACTH causes small increases of aldosterone during stress
-
Atrial natriuretic peptide (ANP) inhibits activity of zona glomerulosa
- only inhibitory one
What do glucocorticoids do
aka cortisol
- ex include: cortisol (hydrocortisone), cortisone and corticosterone
- help to resist stress by: keeping blood sugar rel constant & maintaining blood volume and preventing water shift into tissue
provokes: glyconeogensis (glucose formation) and rises in blood glucose, fatty acids and amino acids
what happens if these is an excess in the levels of glucocorticoids
- Depress cartilage and bone formation
- Inhibits inflammation and the immune system
- Promote changes in cardiovascular, neural, and GI function
what are Gonadocorticoids
sex hormones
- most are androgens (male sex hormones), most ipmortant is testosterone
- contrubute to: onsert of puberty, secondary sex characteristics and sex drive in females (produced in adrenal cortex)
- can be converted into estrogens after menopause
what does the adrenal medulla secrete
*more interior part
- Chromaffin cells secrete catecholamines (epinephrine and norepinephrine)
- Increases blood glucose levels during short term stress
-
Epinephrine
- potent stimulator of the heart
- bronchiole dilation
- increases blood flow to skeletal muscle, brain and heart
- potent stimulator of the heart
-
Norepinephrine
- peripheral vasoconstriction and blood pressure
how does the adrenal gland respond to stress (short term)
adrenal medualla secretes epinpehirne and norep
inc HR, inc BP, liver conversts glycogen to glucose to release in blood
dilation of bionchioles
changes in blood flow patters to dec digestive system actiivty and reduce urine output
inc metabolic rate
how does the adrenal galnd respond to stress (long term)
- hypothalamus released CRH -> anterior pit, ant pit releases ACTH
- targets adrenal cortex to release mineralcorticoids and glucocorticoids
- Mineralcorticoids
- retention of sodium and water by kidneys
- inc blood volume and blood pressure
- Glucocorticoids
- proteins and fats converted to glucose or broken down for energy
- inc blood glucose
- suppression of immune system
what is glucagon
A 29-amino-acid hormone that is a potent hyperglycemic agent
- secreted by alpha cells of the pancreas
What is insulin
- 51 amino acid protein with two amino acid chains linked by disulfide bonds
- released by beta cells
- enhances tranposrt of glucose into cells
- counters metabolic activity that would enhance blood glucose levels
*goes to lvier, inc glycolysis, glycogenesis and lipogenesis to descrease plasma glucose
how are bloog glucose levels regulated
- Too high
- pancrease releases insulin
- stimulates glucose uptake by cells and glycogen formation by liver
- Too low
- pancrease releases glucagon that stim glycogen breakdown in the liver
type 1 vs type 2 diabetes
- Type 1
- typically early onset
- autoimmune disorder that rends to run in families resulting in beta cell death
- needs insulin injections
- Type 2
- Usually adult onset and tends to occur in obese sedentary people
- cells do not respond to insulin
- usually deit and exercise are important for control
what is diabetes mellitus?
what are the long term effects
- type 1
- inability to control blood glucose
long term effects: blindness, loss of limbs, nerve deterioration, kidney and cardiovascular disease
what are the 3 cardinal signs of diabetes Mellitus
Polyuria - huge urine output
Polydipsia - excessive thirst
Polyphagia - excessive hunger and food consumption
describe the gonads in females
- paired ovaries in the abdominopelvic cavity produce estrogen and progesterone
- responsible for
- > maturation of reproductive organs
- > appearance of secondary sexual characteristics
- > breast development and cyclic changes in uterine mucosa
describe the gonads in males
- testes are located in the extra abdominal sax (scrotum)
- > produce testosterone
Testosterone
- > initiates maturation of male reproductive organs
- > causes appearance of secondary sexual characteristics and sex drive
- > is necessary for sperm production
- > maintains sex organs in their functional state
location of pineal gland and whats it involed in
Small gland hanging from the roof of the third ventricle of the brain that secretes melatonin
- Melatonin is involved with day/night cycles, show rhythmic variations (body temperature, sleep, appetite)
*helps the SCN sense the length of the night
what is the SCN? where is it?
Endogenous circadian peacemaker is the Suprachiasmatic nucleus (SCN)
- located in the anterior ventral hypothalamus
*Internal clocks allow us to anticipate and synchronize brain and body functions so they occur at appropriate and optimal times
what is the thymus
Lobulated gland located deep to the sternum
- Hormonal products are thymopoietins and thymosins
- Essential for the development and education of T lymphocytes (T cells) of the immune system thymus
what hormone does adipose tissue secrete
- leptin
- peptide hormone
- secretion of leptin is proportional to fat stores; increased by nutrient uptake
- acts on brain to suppress appetite and increase energy expenditure
- Resistin & adiponectin
- peptide hormones
- unknown trigger
- acts on fat, muscle, liver
- resistin antagonized insulins action
- adiponectin enhances insluins action
