1.11.2 Endocrine Glands & Hormones II
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Thyroid gland) structure: lobes
Has 2 lobes
Thyroid gland) structure: isthmus
Joins the lobes together
Thyroid gland) structure: follicles
Walls made of cuboidal cells
Thyroid gland) follicles structure : what's inside them?
Thyroid gland) follicles structure : what are colloids made from? (2)
-thryoglobin + iodine
Thyroid gland) follicles structure : what store in here?
- Stored form of thyroid hormone
- *it is made of both substances that create colloid
Thyroid hormones made up of (2)
-tyrosine and iodine
2 subtypes of thyroid hormones
- -thyroxine T4
- *converted into T3
- -triiodothyronine T3
- *most bio active
What's difference between both subtypes of thyroid?
Synthesis of thyroid) 2 events happen simultaneously
-formation & storage of thryoglobin
-iodine trapping outside cell
Synthesis of thyroid) in follicle cell,, thyroglobin synthesis begins with
- Joining together of many tyrosines
- *they may be 70 long
Synthesis of thyroid) side chains of tyrosine contain
Aromatic ring and are exposed
Synthesis of thyroid) what create thyroglobin?
Synthesis of thyroid) thyroglobin is transported into
colloid after it is made
Synthesis of thyroid) where is iodine transported to
Enzymes located in the membrane of follicular cell (at the side that faces the colloid)
Places iodine onto the tyrosines
How many iodine atoms bind on aromatic ring of the tyrosine side chains?
1 or 2
Multiple chains of tyrosine are
Couples and this is tired in the colloid
When thyroid hormone is needed,
iodinated thryoglobain is endocytosed into the follicular cell
Cutting of thryogbloin molecules is done by
- Enzymes in lysosomes in follicular cells
- *colloid to follicular cell to lysosomes
Final product from cutting of thyroglobin is separate molecules of T3 & T4, these are
Put into bloodstream where they are transported to target issues
Transport and regulation) thyroxine binding globulin
Protein produced in liver that binds to mostly t3 and some t4 to protect the hormones from degrading as they circulate the blood
What do target tissues do with t4?
They convert it to t3
Regulation of TRH) steps 6
1. TRH (T3/T4) released to stiulate ant gland
2. Ant gland is timualted and releases TSH
3. TSH stimulates thyroid gland to release thyroid hormone
4. Thyroid hormones stimulates all tissues
5. All tissues can inhibit TRH production if there is an increased in body temperature
6. If there is too much thyroid hormone it can inhibit TSH and TRH.
Mechanism of action of thyroid hormone ) intracellular receptors
- Even though it is A.A based product, it goes inside the cell and bins with intracellular receptor mimicking the transduction mechanism of a steroid hormone
- *only exception
Thyroid hormone functions (8)
- -cardiac function
- -skeletal and muscle growth
-reproduction function and lactation
-secretory activity of skin
Thyroid hormone function) metabolic rate
- Enzymes within us begin to function more rapidly causing reactions to occur rapidly
- Ex) glycolysis quicker with thyroid
Thyroid hormone function) CHO and lipid metabolism
CHO and lips metabolism would occurs more rapidly bc of enzymes functioning more rapidly
Thyroid hormone function) neural development
During embryological development, nervous system highly dependent on thyroid for normal development growth
Thyroid hormone function) cardiac fucntion
- Dependent on thyroid
- *too much thyroid causes rapid heartbeat
- *too little slows it down
Thyroid hormone function) skeletal and muscle growth
No normal growth during childhood without thyroid bc thryid assist GH with production of skeletal muscle growth
Thyroid hormone function) GI motility
Assists in moving food along tract for digestion
Thyroid hormone function) reproduction function and lactation
In the background
Thyroid hormone function) secretory of skin
Assist in sebum, sweat, etc
- **too little thyroid = dry skin
- **too much= sweaty
Calcitonin) function (2)
-inhibits osteoclast activity
-regulates blood calcium by increasing uptake by bone
Is calcitonin regulated by hypo and pit?
When calcitonin is realased what does it target?
Regulation of calcitonin) steps (3)
1. Calcitonin will be to stimulate bone
2. If there is high blood calcium, then it will positively feedback to produce more
3. If there is low blood calcium, then it will inhibit calcitonin
Parathyroid glands) 2 types of cells
Parathyroid glands) what do oxyphil cells do?
We don't know
Parathyroid glands) what do chief cells do?
Produces Parathyroid hormone
Parathyroid hormone ) function (3)
Increase osteoclast activity
kidney calcium reabsorption
Calcium absorption from digestive tract
***antagonistic to calcitonin
What is the result form the 3 functions parathyroid hormone ?
Increase blood calcium
Parathyroid hormone ) mechanism of aciton
Regulation ) steps (3)
1. Parathyroid hormone relaxed from endocrine gland to stimulates target tissues
2. If low calcium blood then it will stimulate more parathyroid hormone
3. If high blood calcium, then it will inhibit parathyroid hormone production
*not regulated by hypo or pit
Where are mineralocorticoids produced
Function of aldosterone
Regulates amount of plasma sodium concentration
Where is glucocorticoids produced?
What are the 3 types of glucocorticoids?
Glucocorticoids functions (4)
-increase plasma glucose
Glucocorticoids ) mechanism
Modify gene activity and increased protein sysntheissi
Glucocorticoids ) mechanism: modify gene activty
Glucocorticoids ) mechanism: increased protein synthesis
Glucocorticoids ) mechanism: how are the acitivitre achieved?
The PRoteins that are synthesized are enzymes that perform the activities listed on the previous slide
Regulation of glucocorticoids ) steps (6)
1. Hypo releases CRH
2. CRH stimulates pit, causing it to release ACTH
3. ACTH stimulates adrenal cortex where glucocorticoids reside
4. gluco corticoids stimulate many tissues
5. As glucocorticoids rises, ACTH and CRH are inhibited
6. Also stress stimulated CRH production
Gonadotropin) where is it found?
What are the 2 types of gonadotropin?
Regulation of gonadocorticoids )
1. Hypo releases CRH to stimulate pit
2. Pit simulated releases ACTH
3. ACTH stimulus estrogens/androgens.
- 4. Estrogens and androgens stimulate skeletal system, integument, brain
- *stimulates small amounts of and or and estro for essential purposes in opposite sex like sex drive
5. If estrog and Andre levels high, then they will inhibit ACTH and crh
Adrenal medullary hormones ) chrmoaffin cells release (2)
What are epinephrine and norepehionehre contorled by?
What is the control for chromaffin cells?
chromaffin cells involved in
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