9.3 Endocrine

Question 1

describe the thyroid gland

Answer 1

• largest endocrine gland-> lateral lobes conencted via isthmus
• FOllicle cells produce the glycoprotein thyroglobulin

- colloid (thyroglobulin and isodine) fills the lumen of the follicles

Question 2

what are the effects of thyroid hormone

Answer 2

* 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

Question 3

What are the exceptions of the areas that are not affected by the thyroid gland

Answer 3

* will have an exam question

USTAT

uterus, spleen, testis, adult brain (role in neural development in younger kids), thyroid gland (doesnt target itself)

Question 4

What are the 2 types of thyroid hormones

Answer 4

T4 - Thyroxine; two tyrosine molecules plus 4 iodine

T3 - Triiodothyronine; two tyrosines with 3 iodine

Synthesis

1. Thyroglobulin (constains 134 tyrosine) is synthesized and discharged into the lumen, only hanful actually used
2. I^- taken into cell actively, oxidized to I₂ and released into lumen
3. thyroid perioxidase attached iodine to tyrosine, forming T₁ (MIT) and T₂ (DIT)
4. thyroid peroxidase links togther to form T₃ and T₄
5. Endocytosis of T₃ and T₄ are cleaves in lysoomes and diffuse into blodo stream

Question 5

describe the transport and regulation of TH

which is mroe active

Answer 5

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

Question 6

Describe Hypothyroidism

Answer 6

• 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

Question 7

what is cretinism

Answer 7

form of hypothyroidism found in infants

Question 8

what is graves disease

Answer 8

• 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)

Question 9

what is calcitonin

Answer 9

• 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

Question 10

describe the parathyroid glands

Answer 10

• 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

Question 11

what are the effects of parathyroid hormone

Answer 11

• 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

Question 12

Question 13

describe the adrenal galnds

Answer 13

contains

adrenal medualla: neural tissue that acts as part of the sympathetic nervous system (SNS)

Adrenal cortex: releases steroid hormones called corticosteroids (>24)

Question 14

what are the layers of the adrenal cortex and the corticosteroids produced at each layer

Answer 14

Zona glomerulosa - mineralocorticoids (mostly aldosterone)

Zona fasciculata - glucocorticoids (mostly cortisol)

Zona reticularis - gonadocorticoids (mostly androgens)

Question 15

all steroids are derived from

Answer 15

cholesterol

Question 16

estrogen synthesis, which form is most potent

Answer 16

E2 i the most potent

E1 (estrone) can make E2 (estradiol) or E3 (Estriol)

E2 can also be used yo make E3

Question 17

describe mineral corticoids

Answer 17

• 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

Question 18

what stimulates teh secretion of aldosterone

Answer 18

􏰃 Rising blood levels of K+
􏰃 Low blood Na+
􏰃 Decreasing blood volume or pressure

Question 19

what methods regulate aldosterone

Answer 19

1. Renin-angiotensin mechanism
   
   • angiostensin II stimulates aldosterone release
2. Inc plasma K+ (Na+), directly influences the zona glomerulosa cells
3. ACTH causes small increases of aldosterone during stress
4. Atrial natriuretic peptide (ANP) inhibits activity of zona glomerulosa
   
   • only inhibitory one

Question 20

What do glucocorticoids do

Answer 20

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

Question 21

what happens if these is an excess in the levels of glucocorticoids

Answer 21

• Depress cartilage and bone formation
• Inhibits inflammation and the immune system
• Promote changes in cardiovascular, neural, and GI function

Question 22

what are Gonadocorticoids

Answer 22

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

Question 23

what does the adrenal medulla secrete

Answer 23

*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
• Norepinephrine
  
  • peripheral vasoconstriction and blood pressure

Question 24

how does the adrenal gland respond to stress (short term)

Answer 24

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

Question 25

how does the adrenal galnd respond to stress (long term)

Answer 25

- 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

Question 26

what is glucagon

Answer 26

A 29-amino-acid hormone that is a potent hyperglycemic agent - secreted by alpha cells of the pancreas

Question 27

What is insulin

Answer 27

- 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

Question 28

how are bloog glucose levels regulated

Answer 28

* 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

Question 29

type 1 vs type 2 diabetes

Answer 29

* 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

Question 30

what is diabetes mellitus? what are the long term effects

Answer 30

- type 1 - inability to control blood glucose long term effects: blindness, loss of limbs, nerve deterioration, kidney and cardiovascular disease

Question 31

what are the 3 cardinal signs of diabetes Mellitus

Answer 31

􏰃 Polyuria - huge urine output 􏰃 Polydipsia - excessive thirst 􏰃 Polyphagia - excessive hunger and food consumption

Question 32

describe the gonads in females

Answer 32

- 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

Question 33

describe the gonads in males

Answer 33

- 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

Question 34

location of pineal gland and whats it involed in

Answer 34

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

Question 35

what is the SCN? where is it?

Answer 35

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

Question 36

what is the thymus

Answer 36

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

Question 37

what hormone does adipose tissue secrete

Answer 37

* 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