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Endocrinology
Physio Exam #3
78
Medical
Professional
09/29/2008

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Cards

Term

 

NO is cell-permeant and activates what? 

Definition

 

 

cytosolic guanylyl cyclase 

Term

 

 

From where do agonists exert their influence? 

Definition

 

Outside the Cell 

Term

 

Protein kinase action vs. protein phosphatase action 

Definition

 

p. kinases phosphorylate proteins

 

p. phosphatases catalyze the removal of phosphates 

Term

 

what activates members of the protein kinase C family? 

Definition

 

Ca++, diacylglycerol, certain membrane phospholipids and some breakdown products of membrane phospholipids

Term

 

True or False:

 

Calmodulin is found in all cells 

Definition

 

 

True 

Term

 

What are the steps leading up to the exchange of GDP for GTP in the activation of a heterotrimeric G-protein? 

Definition

 

1. Hormone or agonist binds to membrane receptor, which causes conformational change.

2. Activated receptor accociates with inactive G-protein bound to GDP.

3. Binding to receptor causes G protein alpha subunit to release GDP in exchange for GTP. 

Term

 

What are the steps in G-protein activation following binding of GTP to the protein's alpha subunit? 

Definition

 

1. The GTP-bound alpha subunit  dissociates from beta/gamma subunits and hormone receptor.

 

2. Activated G protein associates with effector protein (eg. adenyl cyclase) and activates it to generate second messenger (eg cAMP).

 

3. Intrinsic GTPase of alpha subunit converts GTP to GDP, causing inactivation and reassociation of alpha subunit with beta/gamma subunits.  

Term

 

 

Gs  G-proteins are activated by receptors for what compounds?

Definition

 

Epinephrine

 

Norepinephrine

 

Glucagon 

Term

 

What is the effector for Gs proteins? 

Definition

 

Adenyl cylclase 

Term

 

Gi G-proteins are activated by receptors for which compounds? 

Definition

 

 

Norepinephrine

 

Adenosine 

 

Prostaglandins

 

Opiates 

Term

 

What is the effector (target) for activated Gi proteins? 

Definition

 

Adenyl cyclase 

Term

 

Gq proteins are activated by receptors for which compounds?

Definition

 

Acetylcholine

 

Epinephrine

 

 

 

(targets Phospholipase C) 

Term

 

Cholera toxin interferes with which step of G-protein activation/inactivation? 

Definition

 

Cholera toxin prevents hydrolysis of GTP in the activated Gs alpha subunit through the addition of an ADP-ribosyl group.  

Term

 

The presence of ________ greatly inhibits the enzymatic activity of PKA 

Definition

 

 

its 2 regulatory subunits

 

 

- cAMP binds to the regulatory subunits, allowing the catalytic subunits to dissociate and phosphorylate target proteins on particular serine and threonine residues. 

Term

 

Myosin light chain kinase and phosphorylase kinase are examples of? 

Definition

 

Calmodulin-dependent protein kinases 

Term

 

_________ is covalent modification of the protein, which changes its properties and most often leads to activation. 

Definition

 

Phosphorylation 

Term

 

4 examples of Serine/Threonine kinases 

Definition

 

 PKA

 PKG
PKC
MLCK

Term

 

Axons from the hypothalmus project directly into the ____________, where they release hormones from nerve terminals into the blood. 

Definition

 

posterior pituitary 

Term

 

_________ hormones are synthesized from cholesterol. They include ______, _______, _______,_______,________, _______. 

Definition

 

Steroid hormones include:

cortisol, aldosterone, androgens, estrogens, progestins, vitamin D. 

Term

 

__________ hormones are synthesized from tyrosine and iodide and include ____ and _____. 

Definition

 

Thyroid hormones include thyroxine (T4) and triiodothyronine (T3).

Term

 

True or False:

 

 ADH and OCT are released by the anterior pituitary. 

Definition
 False. They are released by the posterior pituitary.
Term

 

Diabetes insipidus is characterized by a failure to secrete suffcient amounts of what hormone? 

Definition

 

ADH (vasopressin)

 

 

 

This can lead to excessive water loss through hypotonic urine (polyuria) and drinking large volmes of water (polydipsia).  Treatment with ADH provides rapid relief.

Term

 

Tropic hormones made and secreted by the anterior pituitary include: 

Definition

 

"FLAT PG"

 

FSH

LH

ACTH

TSH 

Prolactin

GH 

Term

 

True or False:

 

GH can inhibit insulin uptake and lipolysis 

Definition

 

False.

 

It does inhibit insulin uptake, but it enhances (does not inhibit) lipolysis.

 

 

Thus GH is diabetogenic (produces diabetes). 

Term

 

GH works directly on peripheral tissues or through the release of secondary peptide hormones called _____. 

Definition

 

Somatomedins or Insulin-like growth factors (IGF-1 and IGF-2) 

Term

 

_____ stimulates GH release from the anterior pituitary, while ____ inhibits it. 

Definition

 

GHRH stimulates

Somatostatin inhibits 

Term

 

______ inhibits Prolactin secretion while _____ enhances it. 

Definition

 

Dopamine or PIF from the hypothalmus is the primary inhibitor. Less important are thyrotropin (TRH) and vasoactive intestinal peptide (VIP).

 

Estrogen acting directly on mammotrophs of ant. pituitary enhances secretion.  

Term

 

A. Iodine is moved from the blood into the follicular cells of the thyroid through what kind of transport?

 

B. By what kind of transport does it move from the follicular cell into the colloid? 

Definition

 

A. Secondary active transport (through I-, Na+ symport)

 

 

B. Facilitated diffusion 

 

Term

 

Which enzyme catalyzes iodination of Thyroglobulin to make T3 and T4

Definition

 

TPO - Thyroid peroxidase 

Term

 

_________ is the protein precursor which contains the tyrosine residues used to synthesize T3 and T4

Definition

 

 

Thyroglobulin 

Term

 

True or False:

 

Only small amounts of T3 and rT3 are secreted by the thyroid. 

Definition

 

 

True.

 

 

Most of the T3 and rT3 are formed from deiodination of T4 in the tissues.

Term

 

Grave's disease, toxic adenoma, TSH-secreting pituitary tumor, and thyroiditis can all cause _____. 

Definition

 

Hyperthyroidsim 

Term

 

Liver glycogen can be made available to other tissues via the process of _________ and glucose release. 

Definition

 

 

glycogenolysis 

Term

 

Glucose can be made de novo by the conversion of two pyruvate molecules via the process called _________. 

Definition

 

 

gluconeogenesis 

Term

 

In the pancreas,

 

1. Alpha cells secrete ____

 

2. Beta cells secrete _______

 

3. D cells secrete ________ 

Definition

 

1. glucagon

 

2. insulin, amylin

 

3. somatostatin 

Term

 

Hsp's are bound to what hormone receptors ?

Definition

 

GRs and MRs (for Cortisol and Aldosterone, respectively) and ARs (for DHT and testosterone) are bound to Hsp's in the cytosol. Binding of the hormones releases the receptors from the heat shock proteins. The new complex then enters the nucleus, dimerizes, and initiates transcription of specific genes.

Term

 

The major hormones synthesized by the adrenal cortex 

Definition

 

Aldosterone (in Glomerulus)

Cortisol (in fasciculata)

Androgens (in Reticularis) 

Term

 

Major hormones synthesized by Adrenal Medulla 

Definition

 

Epinephrine and Norepinephrine

(synthesized in chromaffin cells) 

Term

 

What endocrine organ can be thought of as an enlarged specialized sympatheic ganglion? 

Definition

 

The adrenal medulla 

Term

 

What are catecholamines derived from?

Name the intermediate compounds. 

Definition

 

Tyrosine } Dopa } Dopamine } Norepinephrine } Epineprine

 

 

Limiting step: action of tyrosine hydrogenase in converting tyrosine to dopa 

 

Term

 

Epinephrine binds to what and increases what? 

Definition

 

binds to beta 1 and 2 adrenergic receptors and increases cAMP 

Term

 

Norepinephrine binds to what and increases what? 

Definition

 

binds to alpha 1 and 2 adrenergic receptors and increases intracellular free Ca2+

(through PLC conversion of PIP2 to IP3 and DG)

 

Nepi also decreases cAMP 

Term

 

Beta blockers are used to treat what? 

Definition

 

hypertension 

 

 

(ACE inhibitors also used) 

Term

 

Pheochromocytoma are tumors of what organ? 

Definition

 

Adrenal medulla

 

- produces too much epi and Norepi and so symptoms include high BP, tachycardia, anxiety, headaches, cold sweats, etc 

Term

 

True or false:

 

Catecholamines are secreted from the chromaffin cells of the adrenal medulla with the help of carrier proteins 

Definition

 

False

 

 

ACh stimulates secretetion directly without help of proteins

- No Time for helpers in the fight or flight response! 

Term

 

Metabolic actions of Epi and NorEpi 

Definition

 

blood vessels - constrict (Nepi especially)

heart - increase rate and force of contractions

muscle - release of lactate via glycogen breakdown

liver - glycogenolysis and gluconeogenesis

bronchioles - induces pulmonary vasodilation

renin - stimulates renin release which stim. aldosterone, which increase Na+ retent. and BP 

Term

 



The most distinctive feature of the luteal phase is a 10-fold increase in plasma levels of __________, secreted by the corpus luteum.  

Definition

 

progesterone 

Term

 

What gonadotropin stimulates which cell?

 

LH, FSH

 

Leydig cells, Sertoli cells 

Definition

 

LH acts on Leyding cells 

 

-increases testosterone production through the cholesterol/pregnenolone pathway

 

FSH acts on Sertoli cells

 

- stimulates protein synthesis: inhibin, ABP, P450 aromatase, AMH and 5alpha reductase 

 

- Both cell types are also sensitive to testosterone 

Term

 

True or False:

 

Leydig cells are found in the seminiferous tubules 

Definition

 

False

 

They are found in the connective tissue outside the seminiferous tubules 

Term

 

If fertilization of the egg occurs in the luteal phase, declining LH is replaced by _________, secreted by  placental cells. 

Definition

 

 

HCG - human chorionic gonadotropin  

 

Term

 

True or False:

 

Progesterone is converted to androgens in the Granulosa cells 

Definition

 

False

 

Granulosa cells lack the CYP17 and 17BetaHD enzymes 

Term

 

True or False

 

Estradiol secretion by the dominant follicle feeds back positively to the pituitary and hypothalmus, resulting in LH and FSH secretion. 

Definition

 

True

 

This positive feedback by estradiol responsible for pre-ovulation surge of FSH and LH 

Term

 

Theca cells do not have the ________ enzyme, and so cannot convert androgens to __________. 

Definition

 

aromatase

estradiol

 

 

Theca cells produce androgens from progesterone, while granulosa cells produce estradiol from androgens. 

Term

 

True or False

 

DHEA is synthesized from pregnenelone in the placenta 

Definition

 

False

 

DHEA comes from fetus or mother because it cannot be synthesized by the placenta, which lacks CYP17

 

Placenta turns DHEA into estrogens (estradiol)

Term

 

Name 2 G-proteins that bind to Adenyl Cyclase and activate it to generate cAMP as a second messenger 

Definition

 

Gs and Golf 

Term

 

The inactivation of cAMP is catalyzed by what enzyme? 

Definition

 

cAMP phosphodiesterase 

 

 

-inactivation yields 5'-AMP, which is inactive as a second messenger 

Term

 

Which class(es) of hormones are derived from tyrosine? 

Definition

 

 

Thyroid hormones and catecholamines

 

 

 

Term

 

On which residues are proteins phosphorylated by protein kinases? 

Definition

 

Tyrosine, Serine, or Threonine

 

 

(all have OH groups) 

 

Term

 

Which classes of hormones are lipophylic? 

Definition

 

Steroids and thyroid hormones 

 

 

-These 2 classes are lipophylic, which means they are often bound to proteins (TBG, albumin) and have a longer half-life, making their effects last hours to days as opposed to minutes or seconds, as is the case with hydrophilic catecholamines or peptide hormones.

Term

 

Sensitivity of a hormone receptor is measured by what?  

Definition

 

The hormone dose giving half the maximal response (EC50)

Term

 

 

Diabetes insipidus is caused by a defect in which hormone? 

Definition

 

 

ADH or vasopressin 

Term

 

which hormones are secreted into the median emminence? 

Definition

 

RHs (releasing hormones) and IHs (inhibitory hormones) 

Term

 

What is the other name for the anterior pituitary hormone TSH and what hypothalmic hormone stimulates its release? 

Definition

 

Thyrotropin

Thyrotropin Releasing Hormone (TRH) 

Term

 

Name three hormones that Somatostatin inhibits the secretion of

Definition

 

GH  (Somatotropin)

insulin

glucagon 

Term

True or False:

 

Somatomedins from the liver and other tissues exert both long loop and short loop negative feedback to stop the secretion and release of GH. 

Definition

 

True

 

-somatomedins are also known as Insulin-like growth factors (IGFs) 

Term

 

 

True or False:

 

 

GH inhibits glucose uptake and enhances lipolysis 

Definition

 

 

True

 

 

-thus GH termed diabetogenic 

Term

 

What hormone is produced by the intermediate lobe of the pituitary gland? 

Definition

 

Melanocyte-stimulating hormone (MSH, melanotropin) 

Term

 

Name the actions of LH in both the female and male 

Definition

 

LH in female: stimulates ovulation and luteinization of ovarian follicles

 

LH in male: stimulates testosterone secretion 

Term

 

What are the primary actions of FSH in the male and female, respectively? 

Definition

 

Male: stimulates spermatogenesis

 

Female: stimulates follicle growth 

Term

 

How are thyroid hormones stored? 

Definition

 

T3 and T4 are stored in the precursor protein iodinated thyroglobulin in an extracellular colloid storage compartment.

Term

 

Fatty acids feed into __________.

A. glycolysis

B. citric acid cycle 

 

They do this via the compound _________.

 A. Acetyl CoA

B. Pyruvate 

Definition

 

 

fatty acids only feed into the citric acid cycle through the compound acetyl CoA. 

Term

 

_______ activates glucose uptake into fat and muscle and also enhances the conversion of glucose to glycogen in the liver. 

Definition

 

 

Insulin 

Term

 

_______ inhibits amino acid release and proteolysis in muscle and inhibits lipolysis. 

Definition

 

 

Insulin 

Term

 

 

________ enhances the breakdown of glycogen and increases the uptake of fatty acids and amino acids. 

Definition

 

Glucagon 

Term

 

 

______ is the glucose transporter stimulated by insulin.

 

A. SGLT1

B. SGLT2

C. GLUT4 

Definition

 

C. GLUT4

 

main expression of GLUT4 is in the skeletal and cardiac muscle and adipose and other tissues.

 

 

SGLT1 and 2 are Na-dependent co-transporters of glucose, expressed in the small intestine and renal tubules, respectively. 

Term

 

Can insulin levels be normal in Type 1 or Type 2 diabetes? 

Definition

 

Type 2

-Where there is resistance to insulin

 

 

 

 

 

Type 1 is a defect in pancreatic beta cells - you don't actually secrete any insulin, so treated with injections. 

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