ANAT

Question 1

definition of hormone

Answer 1

1. Are substances released by endocrine glands and transported throughout the blood stream to target tissues where they act to regulate specific functions
2. Need to travel to distal sites via blood

Question 2

difference between endocrine glands and exocrine glands

Answer 2

1. endocrine produces small amount of hormones while exocrine produce nonhormonal substances
2. endocrine does not have duct; exocrine have duct
3. endocrine release hormones straight into the surrounding tissue fluid and into the blood; exocrine release into duct that carry these substances to a membrane surface

Question 3

difference between endocrine system and nervous system

Answer 3

1. endocrine system slow acting hormone messengers; nervous system fast acting electrochemical impulses delivered by neurons
2. long term slow response; short term quick response
3. release hormone; release neurotransmitters
4. regulates activities that require duration (overtime) rather than speed such as growth, development, reproduction to maintain homeostasis; regulates activity of muscles and glands (immediate)

Question 4

list the types of endocrine glands

Answer 4

hypothalamus, pituitary, thyroid, gonads, pancreas

Question 5

types of secondary endocrine organs

Answer 5

kidney, heart, stomach, small intestine, skeleton, skin, adipose tissue, placenta

Question 6

name the 2 classification of hormones

Answer 6

1. based on endocrine gland that produced it
2. based on chemical nature of hormones

Question 7

name the 3 building blocks of hormones

Answer 7

proteins and peptides (amino acids), steroids (cholesterol derivative), amines (tryptophan or tyrosine amino acids)

Question 8

name the hydrophilic and hydrophobic hormones

Answer 8

hydrophilic: FSH, LH, TSH, insulin, glucagon, inhibin, HCG, calcitonin, PTH, oxytocin
hydrophobic: testosterone, progesterone, estrogen/estradiol, vitamin D (calcitriol), melatonin, T3, T4

Question 9

how are hydrophilic and hydrophobic hormones transported around the body?

Answer 9

hydrophilic: dissolved and transported free in blood
hydrophobic: bound to plasma proteins

Question 10

why are not all the surrounding tissues responsive to the hormone that is being released into the bloodstream?

Answer 10

because the target cells have receptors only for that hormone. hormone actions are mediated by binding of hormone to receptor molecules on target tissues specific to that hormones

Question 11

types of target receptor and types of hormones they bind to + rationale

Answer 11

1. Cell membrane receptors
   - protein
   - catecholamines
   *They are both water soluble, hydrophilic hormones. They bind to cell surface receptors because they cannot enter the lipophilic cell membrane
2. Intracellular receptors
   - steroid hormones
   - thyroid hormones
   *They are both lipid soluble, hydrophobic hormones, which can enter the cell membrane due to its hydrophobic nature.

Question 12

binding of hormone with the receptor triggers:

Answer 12

1. alters channel permeability by acting on pre-existing channel-forming proteins
2. acts through second-messenger system to alter activity of pre-existing proteins
3. activates specific genes to cause formation of new proteins

Question 13

is high or low amount of hormones required by the body? why?

Answer 13

low. due to signal amplification, tyrosine kinase phosphorylation due to one protein getting phosphorylated and this triggers another protein to get phosphorylated as well

Question 14

how does our body regulate fluctuations in hormone levels?

Answer 14

negative feedback loop - inhibition of the previous stimuli

Question 15

HPA stands for

Answer 15

hypothalamic-pituitary axis

Question 16

where is thyroid gland located?

Answer 16

in the neck,
on the anterior surface of trachea,
immediately below the larynx

Question 17

shape of thyroid glands

Answer 17

two lobes connected by isthmus

Question 18

is thyroid gland an endocrine or exocrine gland ? why does thyroid gland have an extensive blood supply?

Answer 18

endocrine. require blood to transport hormone around the body

Question 19

list the types of cells in thyroid gland + function

Answer 19

1. follicle cells: Lines around the follicles , Synthesize a globular protein called thyroglobulin and secrete it into the colloid of the thyroid follicles. Thyroglobulin is the backbone of hormone
2. and parafollicular cells (C cells): Cells in between the follicles, Secrete calcitonin and Regulate calcium homeostasis

Question 20

2 other microscopic structures in thyroid glands + function

Answer 20

thyroid follicles (Functional unit for thyroid hormone production & Consists of follicle cells and colloid) and colloid (Extracellular space where thyroglobulin with attached iodine atoms are stored, T3, T4 stored)

Question 21

2 ingredients for thyroid hormones synthesis

Answer 21

tyrosine (synthesised in body) + iodine (dietary intake which must be reduced to iodide ion for it to be absorbed by small intestine)

Question 22

where do most steps of thyroid hormone synthesis occur in?

Answer 22

on TG molecules within the colloid

Question 23

name the 5 steps of thyroid hormone synthesis

Answer 23

iodine trapping, iodination, coupling, colloid resorption, thyroglobulin proteolysis

Question 24

recall the 15 steps of thyroid hormone synthesis

Answer 24

refer to onenote/slides

Question 25

which is the inactive thyroid hormone, T3 or T4? highest concentration in plasma; 90% of secretory produce released from thyroid gland

Answer 25

T4; T3 is the major biologically active form of TH at the cellular level (10 times more potent than T4) --> T3 gets preferentially binding to receptors

Question 26

where does T4 get converted into T3 and via which enzyme?

Answer 26

liver, kidney and pituitary; 5-deiodinase enzyme

Question 27

method of excretion of inactive metabolites formed during conversion of T4 to T3?

Answer 27

secreted into bile and eliminated in the feces with trace amount in the urine

Question 28

conversion of inactive metabolite does not occur in which organ?

Answer 28

pituitary

Question 29

how many percentage of T3 is derived from secreted T4?

Answer 29

80%

Question 30

T4 and to a lesser extent T3, are also metabolised in the liver. what is the process called and with what compound?

Answer 30

metabolised by conjugation with glucuronic acid in the liver

Question 30

T4 and to a lesser extent T3, are also metabolised in the liver. what is the process called and with what compound?

Answer 30

metabolised by conjugation with glucuronic acid in the liver

Question 31

TRH stands for TSH stands for

Answer 31

thyrotropin releasing hormone thyroid stimulating hormone

Question 32

T4, T3 physiological effects (6 effects)

Answer 32

1. increase basal metabolism rate (increase ventilation, HR, increase heat production (calorigenic effect)) - increase size and number of mitochondria together with increase in enzymes that regulates oxidative phosphorylation 2. sympathomimetic effect 3. cardiovascular effects 4. essential for bone growth and maturation 5. crucial for development of nervous system, especially the brain during childhood 6. increase synthesis and degradation of proteins, lipids, and carbohydrates

Question 33

hypothyroidism 3 causes

Answer 33

1. primary failure of thyroid gland 2. secondary to deficiency of TRH, TSH or both 3. inadequate dietary supply of iodine

Question 34

hyperthyroidism 3 causes

Answer 34

1. production of TSI 2. secondary to excess of TRH, TSH or both 3. hypersecreting thyroid tumour

Question 35

signs and symptoms of hyperthyroidism (8)

Answer 35

intolerance to heat, weight loss, muscle wasting, increase systolic BP, tremors, increased diarrhea, bulging eyes, enlarged thyroid

Question 36

signs and symptoms of hypothyroidism (7)

Answer 36

intolerance to cold, brittle nails and hair, weight gain, constipation, fatigue, cardiac complications, dull-blank expression

Question 37

describe graves diseases and the mechanism behind this

Answer 37

is an autoimmune disease in which the body erronously produces TSI (thyroid stimulating immunoglobulin) which mimics the action of TSH. they are able to bind to the TSH receptors on the thyroid cells which stimulates the production of T3 and T4. this cannot be controlled by negative feedback because TSI is not affected by subjected to negative feedback loop.

Question 38

does graves disease patients have goiter?

Answer 38

yes

Question 39

what is a goiter and what are the causes?

Answer 39

goiter = enlarged thyroid gland caused by increased levels of TSH and TSI can be caused by hypothyroidism due to lack of iodine intake from diet which causes increased TSH due to negative feedback hyperthyroidism which is graves disease that produces TSI that activates TSI-TSH receptors

Question 40

treatment of graves disease (3)

Answer 40

1. anti-thyroid medications that interferes with the synthesis of TH (carbimazol spofa) - prevent iodine absorption or deactivating TPO (thyroperoxidase) 2. surgically remove a portion of the enlarged thyroid gland - risk of hypothyroidism 3. administer radioactive iodine - to destroy thyroid gland