Lecture 22 Flashcards
The thyroid gland is located in the ________ and consists of:
_______, ______, and _______
anterior neck
- right and left lobes
- isthmus
- fibrous capsule
the right and left lobes are located anterolateral to the _____ and _____
larynx and trachea
the isthmus is located ______
over the trachea and unites the lobes
the fibrous capsule is located where ?
surrounds the thyroid gland and sends septa deep into the gland
the fibrous capsule is located where ?
surrounds the thyroid gland and sends septa deep into the gland
The thyroid gland has a blood flow about ___x the weight of the gland each minute
5x
the thyroid gland contains microscopic spherical sacs called _________
thyroid follicles
the wall of each thyroid follicle consists of primarily _________ cells called _________.
cuboidal epithelial cells
follicular cells
follicular cells extend into the _______ of each follicle
luminal space
Follicular cells secrete a product called _____ which fills the follicle lumen.
colloid
Colloid is mainly comprised of a large glycoprotein called ________ which contains the thyroid hormones ________ within its molecule
This secretory product must be absorbed back through the _______ and then into the blood before it can function in the body.
thyroglobulin
(T3 and T4)
follicular epithelium
Thyroid hormone T4 is _________
T3 is ___________
Thyroxine (tetraiodothyronine or T4 )
Triiodothyronine (T3 )
Thyroxine (tetraiodothyronine or T4 )- contains _____ atoms of _____
Triiodothyronine (T3 )- contains ___ atoms of ____
___% of the hormone secreted by the thyroid gland is thyroxine.
___% of the hormone secreted by the thyroid gland is triiodothyronine.
4
iodine
3
iodine
93%
7%
____ is 4x as potent as ___ but is present in the blood at much ______ quantities and persists for a much ______ time.
T3
T4
smaller
shorter
Most ingested iodides are absorbed by the GI tract and rapidly excreted by the ______
However, about____% of our ingested iodide is removed from the circulating blood by the thyroid gland.
Iodide is then used for the synthesis of thyroid hormone.
kidneys
20%
Iodide is added to table salt at ______ Sodium Iodide per ______ of Sodium Chloride
one part
100,000
Iodine requirement by the body: ____ MG PER YEAR
If there is no iodine to allow production of thyroxine and triiodothyronine, the anterior pituitary continues to sense this, and ramps up______ production.
This stimulates the thyroid further, and the follicular cells _____________.
Overall, the thyroid gland may become ________ than normal
50 mg/year
TSH
grow larger and larger
10-20x larger
___________:
- thyroid follicular cells trap iodide ions by ________ transporting (pumping) them from the blood into the cytosol.
Iodide Trapping
actively
second step is the Synthesis of_________:
- Occurs while iodide is being trapped
- Follicular cells synthesize a large glycoprotein called _________ in the ___ and _______.
- It is packaged into secretory vesicles that will undergo exocytosis.
- Exocytosis will release it into the__________
thyroglobulin
thyroglobulin
ER
golgi complex
lumen of the follicle
step three is ________ of Iodide:
- __________ amino acids in thyroglobulin will become iodinated.
- Once iodide is oxidized by enzyme_________, it passes through the membrane into the _________.
Oxidation
tyrosine
thyroid peroxidase (TPO)
lumen of the follicle
step four is ___________:
- Newly formed _______ react with the _____ that are part of the thyroglobulin molecules.
- Binding of one iodine atom to tyrosine yields ___________ and binding of two yields __________
- The thyroglobulin accumulates in the follicle lumen
Iodination of Tyrosine
iodine
tyrosines
monoiodotyrosine (T1)
diiodotyrosine (T2 )
step five is Coupling of________ :
-_____ _____ molecules combine to form _____
- ____ ___ molecule and ____ ____ molecule combine to form ___
T1 and T2
two T2
T4
One T2
one T1
T3
Transport occurs upon stimulation of the thyroid gland by _____
Step 6
- when stimulated, droplets of _______ reenter follicular cells by _______ and merge with _______.
- Digestive enzymes in the lysosomes breakdown _________, cleaving off molecules of ______.
TSH
colloid
pinocytosis
lysosomes
thyroglobulin
T3 and T4
Step 7.) ________ of Thyroid Hormone:
- ______-soluble T3 and T4 diffuse through the plasma membrane into the _____ and then into the ____.
- In the blood more than 99% of both T3 and T4 combine with __________ within the blood mainly ________
Secretion
lipid
ISF
blood
transport proteins
thyroxine-binding globulin (TBG)
Diffusion of thyroid hormone:
Once T3 and T4 arrive at the target body cells these lipid-soluble hormones can readily diffuse across the membrane.
It is important to note that although ____ is secreted in higher quantities, once it arrives at the target cells an enzyme called an_______ directly converts it to ____ which is the thyroid hormone that acts within the target cell.
Intracellular hormone receptors have a high affinity for ____specifically.
T4
iodinase
T3
T3
Intracellular receptor binding:
_____ binds to an intracellular receptor forming a ___________
This complex activates __________ which results in the production of new ____
T3
thyroid hormone-receptor complex
gene transcription
mRNA
Synthesis of new protein:
______ diffuses from the nucleus into the cytosol where it attaches to _______.
________ translate the mRNA into _______
This produces the thyroid hormone response of the cell
mRNA
ribosomes
Ribosomes
new protein
_____ blood levels of T3 and T4 , _____ metabolic rate, and exposure to ____ temperatures stimulate the hypothalamus to secrete thyrotropin-releasing hormone (TRH).
Low
low
cold
TRH enters the __________ and flows to the anterior pituitary where it stimulates _________ to secrete ________
hypophyseal portal system
thyrotrophs
thyroid-stimulating hormone (TSH).
TSH travels through the bloodstream to the thyroid gland where it stimulates nearly all aspects of thyroid _______ such as: iodide trapping, hormone synthesis and secretion and even growth of the follicular cells.
follicular cell activity
Thyroid follicular cells release T3 and T4 into the blood until either the:
- _________ returns to normal or
- ___________ returns to normal
metabolic rate
body temperature
Elevated _____ in the body fluids feeds back to the hypothalamus and pituitary gland ________ the release of TRH and TSH respectively.
This negative feedback occurs when the rate of thyroid secretion rises to about _____ x normal.
Secretion of thyroid hormone is then stopped
T3
inhibiting
1.75x
Thyroid Hormone Stimulates __________ Metabolism: Increases circulating glucose for ATP production
- Increases rapid uptake of glucose into cells - Increases glycogenolysis - enhances glycolysis and gluconeogenesis - increases carb absorption in GI tract - increased insulin secretion
Carbohydrate
Thyroid Stimulation of Fat Metabolism:
- Increase in ________- releasing _______ which can be used for ATP production
lipolysis
free fatty acids
Effect of thyroid hormone on Plasma and Liver Fats:
- _________ the concentration of cholesterol, phospholipids and triglycerides in the plasma, it _________ free fatty acids
- decreased thyroid secretion results in ________ in plasma concentrations of cholesterol, phospholipids and triglycerides and almost always causes excessive deposition of fat in the liver.
Decreases
increases
increases
thyroid results in ________ Basal Metabolic Rate:
- Thyroid hormones _______ the rate of oxygen consumption under standard or basal conditions (awake, at rest, and fasting).
Increased
increase
thyroid hormone result in______ Respiration, Blood flow, and Cardiac Output:
- Increased BMR causes increases in oxygen consumption and formation of carbon dioxide.
- These increases activate the brainstem to______the rate and depth of respiration, as well as stimulating vasodilation in most body tissues which increases blood flow.
Increased
increase
Thyroid hormones stimulate the synthesis of additional _____ pumps
- These pumps use large amounts of ATP to move Na and K across the membrane against the gradients - As the cells produce and use more ATP, heat is given off and the body temperature rises. This is known as the \_\_\_\_\_\_\_\_ effect
Na/K
calorigenic
Thyroid hormones enhance some actions of _________ because they upregulate ______ receptors
- This causes ________ in heart rate and blood pressure
catecholamines (epinephrine and norepinephrine)
beta
increases
thyroid hormone results in ________ of the CNS:
- Due to upregulation of beta receptors, thyroid hormone increases mentation.
- Individuals with hyperthyroidism thus have bouts of extreme nervousness, psychoneurotic tendencies such as anxiety complexes, extreme worry, and paranoia.
Excitation
thyroid hormones ______ the muscular system
Therefore, hypothyroidism causes muscles to become _______ where hyperthyroidism causes _______
excite
sluggish
fine muscle tremors.
thyroid hormone Increases _________gland secretion:
- Thyroid hormones act on oil and sweat gland cells to increase their secretory activity produces increased perspiration and oily skin. - Individuals with \_\_\_\_\_\_\_\_\_\_ often complain of lack of sweating, dry skin, and dry hair.
suderiferous and sebaceous
hypothyroidism
due to the exhausting effects of thyroid hormone on the CNS and muscles, the ________ individual is often tired but cannot suppress the excitable effects of the hormone which often results in insomnia.
hyperthyroid
Males: _____ of thyroid hormone causes loss of libido and excessive hormone sometimes causes _____
Females:____ of thyroid hormone causes _______ and loss of _____
lack
impotence
lack
oligo- and amenorrhea
libido
we have ___ adrenal (or _______ glands)
At ______ poles of the ______
2
suprarenal
superior
kidneys
two distinct parts of adrenal glands ?
Adrenal Cortex (outer)
Adrenal medulla (center)
Adrenal Cortex:
-outer ___% of gland
- divided into ___ distinct zone
-secretes a group of hormones called ________ synthesized from _______.
- each zone secretes a different type of hormone
80%
3
corticosteroids- steroid hormones
cholesterol
Adrenal medulla-
- central ____% of the gland
-functionally related to the ______ nervous system
- secretes the hormones __________ and _______
20
sympathetic
epinephrine and norepinephrine
adrenal cortex is subdivided into ____ zones
what are they?
3
zona glomerulosa (outermost)
Zona faciculata (middle)
Zona reticularis (inner)
Zona glomerulosa:
- outermost ____% of adrenal cortex, just ______ the connective tissue capsule
- cells contain enzyme ________
- secrete hormones called ________ which effect mineral homeostasis
-_______!
15%
beneath
aldosterone synthase
mineralocorticoids
aldosterone
what zone is the widest?
Zona faciculata
Zona faciculata
______% of adrenal cortex
- secrete mainly ___________ which affect glucose homeostasis
-secretion controlled by the hypothalamic-pituitary axis secretion of ______________
-_________!
75%
glucocorticoids
adrenocorticotropic hormone (ACTH)
cortisol
Zona reticularis:
- synthesize small amounts of _______-
- secretion controlled by the hypothalamic-pituitary axis secretion of __________and _______________
-e.g. ____________
weak androgens
adrenocorticotropic hormone (ACTH)
cortical androgen-stimulating hormone
dehydroepiandrosterone (DHEA)
Adrenocortical hormones are derived from _______
Cells of the adrenal cortex can form small amounts of ______ from ______
However, about ____% of the cholesterol used for ______ is derived from __________ in circulating plasma.
cholesterol
cholesterol
acetate
80%
steroid synthesis
low-density lipoproteins (LDLs)
How are LDLs Captured and Used:
LDLs diffuse from the plasma into the ____ and attach to specific receptors contained in ______ on the _______ cell membrane.
Coated pits are internalized by ________, forming vesicles that will fuse with cell lysosomes
_________ is released to make steroid hormones
ISF
coated pits
adrenocortical
endocytosis
Cholesterol
______ cell uptake of cholesterol is regulated
This regulation can alter the amount of cholesterol available for _____ synthesis
One of the main regulators is the secretion of ____
Adrenal
steroid
ACTH
Once cholesterol enters the cells it is delivered to the _________ where cholesterol is ______
This results in the formation of _________
this is the rate-limiting step in the eventual formation of ________
mitochondria
cleaved
pregnenolone
adrenal steroids
Produced by cells of the zona glomerulosa
Mineralocorticoids
Mineralocorticoid produce mainly _______
aldosterone
Physiological Action of Aldosterone:
Regulates homeostasis of mineral ions ________, and helps adjust ____________
Also promotes excretion of ____ in the urine.
- This removal of acid from the body can help prevent acidosis
Na+ and K+
blood pressure and blood volume
H+
Produced by cells of the zona faciculata
Glucocorticoids
Glucocorticoids mainly produce __________
cortisol (95%), cortisone, and corticosterone
Physiological Action of Glucocorticoids
Regulates the metabolism and resistance to stress
The extra glucose supplied by the liver cells provides tissues with a ready source of ATP
- ATP helps fight many _______ such as: exercise, fasting, fright, extremes of temp., High altitude, bleeding, infection, surgery, trauma, and disease.
- In addition, because ________ make blood vessels more sensitive to other hormones that cause _________, they are said to raise ___________.
How would this be Advantageous?
- _____________________________
stresses
glucocorticoids
vasocontriction
blood pressure
In severe trauma and blood loss, this helps raise blood pressure.
Effects of Glucocorticoids on Stress:
- Anti-inflammatory Effects:
- glucocorticoids inhibit the activity of ______ that participate in inflammatory responses.
- Unfortunately, they also _____ tissue repair and wound healing.
- In low or short-term doses, glucocorticoids have proven very effective in treating chronic inflammatory disorders such as rheumatoid arthritis.
- Immune Responses:
- proven to ______ the surveillance and response of the immune system
- Often prescribed for __________ to counter tissue rejection.
WBCs
slow
depress
organ transplant recipients
Secreted by zona reticularis
Androgens, mainly DHEA
Physiological effects of Adrenal androgens
Secretion of adrenal androgens is so low that is has little physiologic effects, especially in males.
Males:
-mainly stimulate the growth of _________, as well as the prepubertal growth spurt in boys (and girls)
Females:
promote_____, and are converted into _____ by other body tissues
After menopause, when ovarian secretion of estrogen ceases, all estrogens come from the conversion of _________
axillary and pubic hair
libido
estrogens
adrenal androgens
Hormone producing cells of the adrenal medulla
Chromaffin Cells
The sympathetic nervous system exerts direct control over the chromaffin cells, and hormone release can occur ______
quickly
released by Chromaffin cells is ________
these are ____________
Metabolites of catecholamines are called ___________
Catecholamines
Epinephrine
Norepinephrine
metanephrines
____% of the medullary cells secrete epinephrine
____% secrete norepinephrine
Physiological Action:
- ____________________
80%
20%
Intensify sympathetic Fight or Flight response
Constricts most blood vessels in the body (increased arterial pressure)
Increases activity of the heart
Increased muscle strength
Increased blood glucose concentration
Increased glycolysis in liver and muscle
Increased mental activity
Increased coagulability
Dilates pupils
Inhibits kidneys
Inhibits GI tract
norepinephrine
Constricts most blood vessels in the body (increased arterial pressure)
Increases activity of the heart
Increased muscle strength
Increased blood glucose concentration
Increased glycolysis in liver and muscle
Increased mental activity
Increased coagulability
Dilates pupils
Inhibits kidneys
Inhibits GI tract
epinephrine
________ has greater Beta Adrenergic receptor stimulation, meaning:
- Greater cardiac stimulation means more cardiac output increase
_____________ has far greater effect on blood vessels of the muscles
- This increases total peripheral resistance and arterial pressure increases, but less of a direct effect on cardiac output
Epinephrine
Norepinephrine
Together, the effects norepinephrine and epinephrine look like _______________ activation
These effects last longer (hormones rather than direct nervous system activation).
Epi and Norepi effects last from _______ after the stimulating event
A relatively small percentage of cells in the body have direct sympathetic innervation
Despite this, all cells have a ________ increase caused by epinephrine, and to some extent norepi.
sympathetic (fight or flight response)
2-4 minutes
metabolic rate
