March 10, 2015 --> 91-105 Flashcards Preview

BOARD: Biochemistry (Dental Decks) > March 10, 2015 --> 91-105 > Flashcards

Flashcards in March 10, 2015 --> 91-105 Deck (42):

The major effects of glucagon on glucose metabolism are? (2)

1. Breakdown of liver glycogen (Glycogenolysis)
2. Increased gluconeogenesis in the liver.

*Both of these effects greatly enhance the availability of glucose to the other organs of the body.


Glucagon is secreted by what cells?

Alpha cells in the islets of Langerhans of the pancreas

- This is in response to a fall in blood glucose level.


What type of nerve stimulation promotes glucagon release

Sympathetic stimulation


T or F, Glucagon release is promoted by many factors one of which is circulating catecholamines via alpha 1-Adrenergic receptors

False, B2-adrenergic receptors


In what instance are glucagon and insulin responses not opposites?

Increased levels of amino acids (especially arginine and alanine) in the blood plasma


What hormone acts locally within the islets of Langerhans themselves to depress the secretion of insulin and glucagon

Somatostatin (aka, growth hormone inhibitory hormone)


Secretin is secreted by what cells? They are secreted in response to what?

Secreted by "S" cells in the mucosa of the duodenum in response to acidic gastric juice emptying into the duodenum from the pylorus of the stomach.


Secretin has what 3 functions?

1. Inhibits stomach motility and gastric acid secretion
2. Stimulates the pancreatic duct cells to secrete a fluid that contains a lot of bicarbonate ions but is low in enzymes
3. Stimulates the secretion of bile from the gallbladder


Cholecystokinin is secreted by what cells in response to what?

Secreted by the "I" cells in the mucosa of the duodenum and jejunum mainly in response to digestive products of fat, fatty acids and monoglycerides in the intestinal contents


As acidy chyme enters the duodenum, the decreasing pH inhibits the secretion of what?

Inhibits gastrin secretion
- Also causes the release of negative or "stop" signals in the duodenum.


What are enterogastrones and what 3 hormones are considered enterogastrones?

Enterogastrones: Hormones that are negative or "stop" signals in the duodenum
1. Cholecystokinin (most important stop signal)
2. Secretin
3. Gastric inhibitory peptide (GIP)


Enterogastrones are released by what part of the GI tract?
- In response to what?? (3)

Released by small intestine in response to:
1. Acidity of the duodenal chyme
2. Presence of Amino acids
3. Presence of free fatty acids in the chyme


Where is aldosterone produced?

Adrenal cortex


Cells in what part of the adrenal cortex secrete Aldosterone?

Cells located in the zone glomerulosa of the adrenal cortex


Aldosterone promotes reabsorption of what?

Promotes reabsorption of sodium into the blood from the glomerular filtrate
- Note: Potassium is lost in the urine. High aldosterone levels will result in low potassium levels I'm in the plasma


The major target of aldosterone is where?

The distal tubule of the kidney, where aldosterone stimulates exchange of sodium and potassium


What 3 primary physiologic effects occur as aldosterone targets distal tubule in kidney

1. Increased resorption of sodium
2. Increased resorption of water
3. Increased renal excretion of potassium


Two most significant regulators of aldosterone secretion are:?

1. Concentrations of potassium ion in extracellular fluid: Small increases in blood levels of potassium strongly stimulate aldosterone secretion
2. Angiotensin II: activation of the renin-angiotensin system as a result of decreased renal blood flow results in release of angiotensin II, which stimulates aldosterone secretion.


Decreased sodium concentration causes the juxtaglomerular cells of the kidneys to secrete what?

Renin, which converts angiotensinogen to angiotensin I. Angiotensin I is converted to angiotensin II, which in turn, stimulates the adrenal cortex to release aldosterone


What molecule has the opposite physiologic effects of aldosterone?

ANP's (Atrial natriuretic peptide)


What disease is a common adrenocortical insufficiency?

Addison's disease

Symptoms: hypotension, hyperpigmentation, muscle weakness, anorexia, hypoglycemia and hyperkalemic acidosis


How do oral contraceptives work?

They apparently prevent the rise in luteinizing hormone which in turn, prevents ovulation.

Mechanism: In presence of either estrogen or progesterone (synthetic), the hypothalamus fails to secrete the normal surge of LH-releasing factor (gonadotropin-releasing factor). This then inhibits the release of luteinizing hormone from basophils of the anterior pituitary gland. Subsequently, ovulation does not occur.


T or F, although 93% of active hormones secreted by thyroid gland is thyroxine and 7% is triiodothyronine, almost all of the thyroxine is eventually converted to triiodothyronine in the tissues, so both are functionally important.



What will a dietary iodine deficiency do do the hormones secreted by the thyroid

Will increase secretion of thyroglobulin (as opposed to thyroxine, triiodothyronine or TSH)


What two hormones are considered catecholamines? From what amino acid are they synthesized from?

Epinephrine and Norepinephrine
Synthesized from tyrosine


What stimulates the release of catecholamines?

These hormones are stimulated by acetylcholine release from preganglionic sympathetic fibers innervating the adrenal medulla.


Norepinephrine can be released in what 2 ways?

1. By the adrenal medulla into the bloodstream
2. Directly onto an organ by a postganglionic sympathetic (adrenergic) neuron that stores norepinephrine


5 effects of Epinephrine

1. Stimulates glycogenolysis and gluconeogenesis, which tend to raise blood glucose levels. Also stimulates lipolysis in adipose tissue
2. Increases the rate, force and amplitude of the heartbeat
3. Constricts blood vessels in skin, mucous membranes and kidneys
4 Dilates bronchioles in the lungs, dilates blood vessels in skeletal muscle and relaxes bronchiolar smooth muscle
5. Activates muscle glycogen phosphorylase


3 effects of Norepinephrine

1. Increases the heart rate and the force of contraction of heart muscle
2. Promotes lipolysis in adipose tissue
3. Constricts blood vessels in almost all areas of the body, thus increasing total peripheral resistance


Parathyroid hormone is secreted by what cells in response to what?

Secreted by chief cells in the parathyroid gland in response to decreased plasma-calcium levels.
- Plasma-calcium level is the major controller of parathyroid hormone secretion


3 modes of action for parathyroid hormone

1. Increases calcium removal from storage in bone and increases absorption of calcium by intestines, increasing blood calcium levels.
2. Acts on the kidneys to decrease calcium excretion and increase phosphate excretion in the urine
3. Increases the absorption of calcium in the GI tract indirectly by causing the kidney to produce vitamin D


T or F, A diet rich in calcium will result in production of PTH and bone resorption

False, a diet deficient in calcium


All steroid hormones are synthesized from what molecule?



Cortisol promotes what metabolic effects?

Breakdown of protein


Cushing's syndrome results from what?



Adrenocorticotropic hormone (ACTH) stimulates the adrenal cortex to synthesize and secrete what?



Release of cortisol is controlled by what other hormone?

Controlled primarily by ACTH


Describe the steps needed for the secreting of cortisol starting at the hormone released from the Hypothalamus

Hypothalamus: Corticotropin-releasing hormone is released from here and influences the release of ACTH.

Anterior Pituitary: ACTH is released from here which controls the release of cortisol

Adrenal cortex: Cortisol is secreted by the cells of the zone fasciculate in the adrenal cortex


Cortisol has a negative feedback or positive feedback loop influence on ACTH and CRH?

Negative feedback. Cortisol exerts an inhibitory influence on both ACTH and CRH


What effects does cortisol have on insulin, glucagon and epinephrine

Allows glucagon and epinephrine to work more effectively at their target tissues
Antagonizes the actions of insulin


What is the Best-Known metabolic effect of cortisol and other glucocorticoids on metabolism?

Their ability to stimulate gluconeogenesis by the liver, often increasing the rate of gluconeogenesis as much as 6- to 10-fold


Why might taking cortisol for a LONG period of time atrophy the adrenal cortex?

There may be an atrophy of the adrenal cortex because of the inhibition of ACTH production