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Chapter 19: Endocrine Gl.s 2 (TIII)


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Where is the adrenal medulla?
the inner core of the adrenal gland
What (in really general terms) does the adrenal medulla produce?
a neurohormone
(because it involves SNS)
How could you say that the adrenal medulla is "modified"?
-it is a modified part of the sympathetic n.s.
-it is a modified postganglionic neuron
What is the adrenal medulla (in really general terms) signaled by?
a preganglionic neuron
What does the adrenal medulla store and secrete?
Stores and secretes epinephrine and NE
-BUT epinephrine is the most abundant (about 80% of output)
Where is the NE and epinephrine secreted to from the adrenal medulla? What does this make it?
-released into the blood by sympathetic stimulation
-this makes it a neurohormone (not a neurotransmitter) in this sit.
Epinephrine and NE vary in their affinity for what?
for different kinds of alpha and beta adrenergic receptors on target organs
What does the epinephrine secreted by the adrenal medulla reinforce and exert?
reinforces the sympathetic n.s. and exerts additional metabolic effects
List 5 effects of the epinephrine released by the adrenal medulla?
1. fight or flight response
2. Constricts most bl. vessels supplying organs EXCEPT it dilates the blood to the heart and skeletal muscles
3. metabolically, promotes glycogenolysis (liver and skeletal muscles), while stim. glucagon secretion and inhibiting insulin secretion
4. Promotes lipolysis
5. Causes CNS arousal
What is glycogenolysis?
glycogen breakdown which produces glucose circulation in blood thus increasing energy
The promotion of lipolysis is for what?
CNS arousal as a response to stress is caused by what?
a rush of epinephrine from the adrenal medulla
What kind of pattern is a stress response?
a pattern of reactions to a situation that threatens homeostasis
Another name for a common group of responses to noxious stimuli?
general adaptation syndrome
What has a role in "general adaptation syndrome" to noxious stimuli?
sns and epinephrine
What is the result of sns and epinephrine's response to stress?
result is readiness and mobilization of biochemical resources
What is key in the stress response?
Where is blood shunted during the stress response?
shunted to the heart and skeletal muscles while being diverted away from the other organs
What systems are activated by the stress response?
1. CRH - ACTH - Cortisol
2. Renin - Angiotensin - Aldosterone
How is blood glucose activated in the stress response?
by decreased insulin and increased glucagon secretions
In the stress response what does the renin-angiotensin-aldosterone system do?
along with vasopressin it is responsible for the maintenance of BP and blood volume
The multifaceted stress response is coordinated by what?
What does the hypothalamus do in the stress response?
activates the sns and CRH-ACTH-cortisol release
Activation of the stress response by what may be harmful?
psychosocial stressors
What is metabolism?
all of the chemical rxns within the cells of the body
What is fuel metabolism?
the degradation, synthesis, and transformation of proteins, carbs, and lipids
What is fuel metabolism aka?
intermediary metabolism
What is digestion?
macromolecules broken down into smaller absorbable subunits
Give 3 examples of digestion?
1. proteins to AAs

2. Carbs to monosaccharides

3. Dietary fats to fatty acids and monoglycerides
What is anabolism?
SYNTHESIS of large organic molecules
What do anabolic rxns req?
What is catabolism?
BREAKDOWN of large molecules
What do catabolic rxns make?
Give two examples of catabolic rxns?
hydrolysis and glucose oxidation
The smaller subunits produced by catabolism can be used for what?
Energy or cellular synthesis
What do we do with nutrients between meals?
store them
Brain's fuel of choice is what?
Glucose-it needs a continous supply
Name three structural and functional macromolecules in cells?
1. AAs
2. Glucose
3. Fatty acids
What does it mean when you say that some of the nutrient molecules can be interconverted?
ex. AAs can b/c glucose
ex. glucose can b/c fatty acids
ex. AAs can become fatty acids
Give examples of some nutrients that have to be digested?
vitamins, minerals, iron, iodine, calcium
Nutrients from meals must be what between meals?
stored and released
Where is excess circulating glucose stored?
it is stored as GLYCOGEN in the liver and skeletal muscles
How much glycogen can you store?
a limited, about 24 hour, supply
When the limited amount of glycogen that can be stored is reached what happens to the rest?
It is stored as triglycerides in adipose tissue
The brain needs a constant supply of what?
The brain cannot store what?
glycogen (this is why it needs a constant supply of glucose)
Since the brain cannot store glycogen the blood glucose concentration is what?
highly regulated
When the body is fasting what occurs?
many body cells burn fatty acids to spare glucose for the brain
If necessary, to supply the brain, what can AAs do?
They can be converted to glucose by gluconeogenesis
Excess circulating fatty acids are incorporated into what? Where does this happen mainly?
-incorporated into triglycerides
-mainly in adipose tissue
Excess AA are converted to what? What are they ultimately stored as?
-converted to glucose and fatty acids
-stored as triglycerides in adipose tissue
What is the main site of amino acid storage?
the muscles via structural proteins
Are proteins the first choice for energy? explain.
No. b/c they serve essential functions (so they will only breakdown if you are starving)
Name the two functional metabolic states?
1. Absorptive (fed) state
2. Postabsorptive (fasting) state
Adipose tissue is what?
Describe the Absorptive st.?
It occurs when ingested nutrients are being absorbed into the blood following a meal (approx. 4 hours).
What fuels are stored during absorptive state?
metabolic fuels
Describe the postabsorptive state?
Nutrients are not being absorbed at this time (between meals)
What is mobilized during the postabsorptive state?
metabolic fuels
Fuel metabolism is regulated by what?
insulin and glucagon from the pancreas
Pancreas has what kind of cells?
exocrine and endocrine
What are endocrine cells in the pancreas organized into?
islets of langerhans
What do the beta cells in the pancreas produce?
What do the alpha cells in the pancreas produce?
What can inhibit both the beta cells and the alpha cells of the pancreas?
somatostasin from pancreatic d cells
When is insulin increased?
after meals
Insulin lowers what?
blood glucose, fatty acid, and amino acid levels
-it promotes their storage
What does insulin facilitate?
glucose transport into most cells
How is the facilitation by insulin of glucose into most cells accomplished?
glucose transporter acts as a plasma membrane carrier to accomplish this process
Insulin and the glucose transporter not only facilitate glucose transport into cells, but also assists what?
the transport of fatty acids into tissues
Insulin stimulates what?
glycogenesis in skeletal muscles and liver cells
What does insulin inhibit?
glycogenolysis and gluconeogenesis
(inh.s breakdown and inhibits new production of glucose)
What does insulin catalyze?
the production of fatty acids from glucose
-promotes entry of fatty acids from blood into adipose
What does insulin promote?
the transport and incorporation of AAs into cells for protein synthesis
An increase in blood glucose during the absorptive st. increases what? What does this do?
insulin secretion
-this brings bl. glucose down to a normal level
A decrease in glucose below normal does what? What does this do to metabolism?
-inhibits insulin secretion
-shifts metabolism from the absorptive to the postabsorptive state
Elevated blood AAs do what?
stimulate insulin secretion.
The sns does what to insulin?
decreases its secretion
Inadequate insulin action produces what? What does this result in?
-diabetes mellitus
-results in hyperglycemia
-too much glucose in the blood for both types
Type I diabetes is due to what?
insulin deficiency
Type II diabetes is due to what?
reduced sensitivity of target cells to insulin
The parasympahetic is the ? of the sympathetic?
-calm, relaxed st.
Insulin and Glucagon could be considered what?
ying and yang
Glucagon ? the actions of insulin.
Name 3 ways in which glucagon opposes the effects of insulin?
1. Promotes glycogenolysis and stimulates gluconeogenesis
2. Promotes fat breakdown
3. Promotes protein breakdown in the liver
Glucagon secretion increases during what state?
the postabsorptive state
In relation to bl. glucose conc. when does glucagon secretion increase?
when blood glucose concentration is too low
What abnormalities are due to a glucagon deficiency?
-there are no known abnormalities due to a glucagon deficiency
There are no known abnormalities due to a glucagon deficiency but an excess of glucagon may do what?
An excess can aggravate the hyperglycemia of diabetes mellitus
Insulin and glucagon work as a team to do what?
control blood concentration of glucose AND fatty acids
Where are insulin and glucagon stored?
in the pancreas, released when needed
What kind of hormones are insulin and glucagon?
peptide hormones
An increase in blood glucose causes what in order to decrease back to normal?
1. inhibits alpha cells to decrease glucagon
2. stim.s beta cells to increases insulin
A decrease in blood glucose causes what in order to increase back to normal?
1. stim.s alpha cells to increase glucagon
2. Inh.s beta cells to decrease insulin
Calcium metabolism is controlled by what?
the endocrine system
Distribution of calcium in the body? (percentages)
1. 99% in bones and teeth
2. 9% in intracellular soft tissue
3. 1% in ECF
4. 0.05% of that is involved in the ENDOCRINE (in plasma proteins)
Plasma calcium must be what?
5 functions of calcium?
1. neuromuscular excitability
2. excitation-coupling in cardiac smooth muscle
3. stimulus-secretion coupling
4. maintenance of tight junctions between cells
5. blood clotting
What does calcium homeostastis involve?
immediate adjustments to control the calcium in the blood
What does calcium balance involve?
involves slow adjustments to maintain the total amount of calcium in the body
PTH aka?
parathyroid hormone
What is PTH essential for?
life (w/out it you will die in few days)
What is PTH secreted by?
the parathyroid glands
Where are the parathyroid gl.s located?
at the back of the thyroid gl.
3 effects of PTH?
1. raises level of calcium ions in blood
2. signals the bones, kidneys, and intestine, resulting in increased plasma calcium
3. Lowers phosphate ions in the blood
Why is the bone hard?
due to calcium and phosphate
Bones constantly undergo what?
remodeling, because it is a dynamic living tissue
Two reasons why the bones constantly undergo remodeling?
1. keeps skeleton at maximal effectiveness
2. helps maintain plasma calcium levels
The remodeling of the bones results from what?
an interplay of bone deposition (osteoblast activity) and bone resorption (osteoclast activity)
Bone deposition is aka?
osteoblast activity
Bone resorption is aka?
osteoclast activity
In adults the rate of deposition and resorption processes are what?
about equal
Children have more deposition or resorption in their bones?
deposition, still growing
Bone deposition of Calcium increases what?
the mechanical strength of the bones
Too much bone resorption can do what?
weaken the bones
Osteoporosis is essentially what?
a reduction in bone mass
The overall effect of PTH is to accomplish what?
to release calcium ions from the bones into the blood
2 ways that PTH accomplishes releasing calcium ions from the bones into the blood?
1. PTH QUICKLY releases calcium from a LABILE POOL in bone fluid (immediate need)

2. PTH also promotes the SLOW TRANSFER of calcium and phosphate from a STABLE POOL of minerals in bones (chronic need)
Describe what occurs in the quick release of calcium from a labile pool in bone fluid for immediate need?
1. PTH stims the transfer of calcium across the osteocytic-osteoblastic bone membranes in bones
2. Calcium in the area is quickly replaced from mineralized bone
How does PTH promote the slow transfer of calcium and phosphate from a stable pool of minerals in bones for chronic need?
via localized dissolution of calcium in bones into the surrounding ECF
The bone membrane is what?
osteoblastic and osteocytic
What is an osteocyte?
interacts with osteoblast
-communicates with eachother thru canals (canaliculi)
What is canaliculi?
fluid filled
-means of exchange
What is lamella?
layers of osteocytes
-formed in concentric rings
What is an osteon?
-with central canal surrounded by concentric rings known as lamella
-run parallel to long axis of bone
Describe blood vessels from marrow?
run thru the central canal of the osteon
-it's where other vessels from bone marrow and outside portion of bone feeding in
The central canal is a what?
blood vessel
-allows extracellular fluid to go into canals
Fast exchange of calcium thru osteocytic-osteoblastic bone membrane derived from where?
the labile pool of calcium in bone fluid in
-fueled by PTH
Where does the slow exchange of calcium through the osteocytic-osteoblastic membrane derive from?
from mineralized bone (stable pool) thru bone dissolution
-fueled by PTH
What is included in the caniliculi of the bone?
1. labile pool of bone fluid
2. ostoecytic-osteoblastic bone membrane
What is included in the central canal
PTH signals the kidneys to do what?
to conserve calcium and eliminate phosphate
When PTH signals the kidneys to conserve calcium and eliminate phosphate what effect does it have?
adds calcium to the blood plasma
When PTH signals the kidneys to conserve calcium and eliminate phosphate what kind of relationship is there between the two?
-there is an inverse relationship between calcium and phosphate levels in the blood plasma because they are in equilibrium with bone crystals
-the product of their two concentrations must be constant
PTH indirectly promotes intestinal absorption of what?
How does it do this? In turn what does vitamin D do?
Calcium and phosphate by playing a role in vitamin D activation
-in turn vitamin D increases intestinal calcium absorption
Whenever calcium is increasing what is phosphate doing?
-phosphate is decreasing
What is the primary regulator of PTH secretion?
the plasma concentration of Calcium
-PTH secretion rises in response to a decrease in calcium in the blood
Calcitonin (thyroid gland) lowers what in the blood? But it is not important in what?
-lowers calcium level in the blood
-but it is not important in normal (day to day) control of calcium metabolism
Calcitonin (thyroid gl.) protects against what?
hypercalcemia (an increase in calcium concentration)
Phosphate metabolism is controlled by the same mechanisms that regulate what?
Calcium metabolism
Increase in PTH leads to what in relation to calcium and phosphate?
-increase in calcium
-decrease in phosphate
A decrease in PTH leads to what in relation to calcium and phosphate?
-decrease in calcium
-an increase in phosphate
The matrix of bones is composed of what two elements?
What does the body focus on?
calcium and phosphate
-body focuses on calcium and phosphate reacts kind of secondary
PTH hypersecretion is aka?
What does hyperparathyroidism cause? What effects occur?
hypercalcemia (inc. calc.) and hypophosphatemia (dec. PO4)
-reduces the excitability of muscle and nervous tissue
-cardiac disturbances can occur
-thinning of bones
-development of kidney stones
During PTH hypersecretion why would there be a thinning of bones?
YES, Because you are constantly making them give up there calcium
PTH hyposecretion is aka?
What does hypoparathyroidism lead to? What are the asscoiated effects?
leads to hypocalcemia and hyperphospatemia
-increases neuromuscular excitability
Which is more likely to happen hyperparathyroidism or hypo-""?
Hyper- b/c hypo rarely occurs, rarely if there is an autoimmune attack
Hyperparathyroidism and Hypoparathyroidism are considered what kind of disorders?
Calcium disorders
Name another Calcium disorder besides hyper/hypo-parathyroidism?
vitamin D deficiency
What does vitamin D deficiency cause?
decreases intestinal absorption of calcium
-can lead to rickets in children and osteomalacia in adults
What is rickets?
-seen in children with vitamin d deficiency
-bowing of the legs
What is osteomalacia?
seen in adults with vitamin D deficiency
-softening of the bones

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