PCB 3703C Lecture Notes - Lecture 35: Hypophyseal Portal System, Holocrine, Apocrine

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30 Mar 2017

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The endocrine system refers to glands that secrete hormones directly into the circulatory system to be carried towards distant target cells/tissues/organs. Endocrine glands secrete hormones into the bloodstream and extracellular fluid. Because endocrine glands are ductless, their secreted hormones are released into the interstitial space surrounding cells where they will be delivered to the nearest capillaries for systemic circulation. The endocrine response time is slower than that of the exocrine. Endocrine hormones require one of two specific receptors: cell surface receptor on cell membrane (specific for protein hormones, peptide hormones, and amino acid hormones) nuclear (intracellular) receptor inside of nucleus (specific for steroid hormones. 2 types are steroid hormones are sex hormones such as testosterone, androgen, estrogen, and progesterone; and, corticosteroids). Examples of exocrine glands are sweat, saliva, and mammary glands. Exocrine hormones are released into ducts versus the ductless endocrine glands. Classifications of exocrine ducts are merocrine glands, holocrine glands, and apocrine glands.

Related Questions

Key: A.Increase

B.Decrease

C. Remain thesame

For questions 19-20 use the following information Thyroid-stimulating hormone (TSH) is secreted from the anterior pituitarygland and acts on the thyroid gland to increase the secretion ofthyroid hormones. Thyroid hormones, on the other hand, have anegative-feedback effect on TSH secretion (See Fig. 16.8 in yourtext). For a person having normal thyroid function, the rate atwhich TSH and thyroid hormones are secreted remains within a normalrange of concentrations. In some people, however, the immune systembegins to produce an abnormal substance that functions likeTSH.

Predict what that substance will do to:

19. _____the rate of thyroid stimulating hormone secretion

20. _____ the rate of thyroid hormone secretion.

For question 21 use the following information. Background:Hormones are dissolved in blood plasma and transported either in afree form or bound to plasma proteins. Hormones that are lipidsoluble, such as steroids and thyroid hormone, circulate in theblood in combination with these plasma proteins. Hormones that bindto plasma proteins do so in a reversible fashion according to theequation:

H + BP <-----------> HBP

(Hormone) (BindingProtein) (Hormone bound to binding protein)

An equilibrium is established between the free plasma proteinsand the hormones bound to the plasma proteins. This equilibrium isimportant because only a free hormone is able to diffuse throughcapillary walls and bind to target cells. The combination of ahormone bound to a binding protein reduces the rate at which theydiffuse through the walls of capillaries.

This increases the half-life of the hormone. The half-life isthe length of time it takes to eliminate half a dose of a substancefrom the circulatory system. The half-life of a hormone is astandard measurement used by endocrinologists because it allowsthem to predict the rate at which a given hormone will beeliminated from the body.

21. _____How is the half-life of a hormone affected by adecrease in the concentration of the

specific plasma protein to whichthat hormone binds? Remember if the time to

eliminate a hormone from theblood stream is longer then the half life has increased.

If the time to eliminate ahormone shortens then the half life has decreased

22. _____Consider a hormone that is secreted in large amounts ata given interval, modified

chemically by the liver, andexcreted by the kidney at a rapid rate, making the

half-life of the hormone in thecirculatory system very short. The hormone therefore

rapidly increases in the bloodand then decreases rapidly. Predict the

consequences of liver and kidneydisease on the blood levels of that hormone.

For question 23 use the following background information:Periodic increases in the sensitivity of some tissues to certainhormones is called up-regulation. It results from an increase inthe rate of receptor molecule synthesis. In many tissues the numberof hormone receptors rapidly decreases after exposure to certainhormones. This is called down-regulation.

Problem. Estrogen is a hormone secreted by theovary. It is secreted in greater amounts after menstruation and afew days before ovulation. Among its many effects is causing

up-regulation of receptors in the uterus for another hormonesecreted by the ovary called progesterone. Progesterone is secretedafter ovulation. A major effect of progesterone is to cause theuterus to become ready for the embryo to attach to its wallfollowing ovulation. Pregnancy cannot occur unless the embryoattaches to the wall of the uterus.

23. ______Predict the consequences on becoming pregnant if theovary secretes too little

estrogen?

24. ______ Predict the effect of inadequate dietary intake ofcalcium on PTH secretion

25. ______ Predict the effect of inadequate dietary intake ofcalcium on Calcitriol secretion

violetspider457

QUESTION 1

Which of the following is an example of an extracellular signal molecule?

	a.	IP₃
	b.	cAMP
	c.	Insulin
	d.	Diacylglycerol

2 points

QUESTION 2

Nuclear hormone receptors _____

	a.	Bind to water soluble ligands
	b.	Activate second messengers
	c.	Regulate transcription in response to ligand binding
	d.	Are normally located on the plasma membrane

2 points

QUESTION 3

Which of the following does not occur when a receptor tyrosine kinase is bound by ligand?

	a.	Phosphorylation of the RTK
	b.	Cytoplasmic proteins bind the phosphorylated RTK
	c.	Dimerization of the RTK
	d.	The RTK binds to DNA to regulate transcription

2 points

QUESTION 4

Which of these is a logical signal-transduction pathway?

	a.	An intracellular receptor activates phospholipase C, which cleaves a membrane protein to form IP₃, which then activates the opening of an ER channel protein, which releases cyclic AMP into the cytoplasm, where it binds to an intracellular enzyme that carries out a response.
	b.	A G-protein-linked receptor activates G protein, which activates phospholipase C, which cleaves a membrane lipid to form IP₃, which binds to a calcium channel on the ER, which opens to release calcium ions into the cytoplasm, which bind to an intracellular enzyme that carries out a response.
	c.	An ion-channel receptor opens, allowing a steroid hormone to enter the cell; the steroid hormone then activates protein kinases that convert GTP to GDP, which binds to an intracellular enzyme that carries out a response.
	d.	A tyrosine-kinase receptor activates adenylyl cyclase, which activates phospholipase C, which converts ATP into cyclic AMP, which binds to an intracellular enzyme that carries out a response.

2 points

QUESTION 5

Which of the following is an example of signal amplification?

	a.	activation of an enzyme molecule
	b.	activation of a specific gene by a growth factor
	c.	Breakdown of many cAMP molecules
	d.	activation of 100 molecules by a single signal binding event

2 points

QUESTION 6

Consider a signal transduction pathway that utilizes cAMP as a second messenger to activate PKA (Protein Kinase A). Which of the following situations will result in the cellular response?

		The G protein releases GDP and binds to GTP
		The target protein (adenylyl cyclase) is inactive
		The regulatory subunits of PKA (Protein Kinase A) are bound to the catalytic subunits
		The appropriate G protein is bound to GDP

2 points

QUESTION 7

Which of the following is found in only some signal transduction pathways? [In other words, which is not found in all signal transduction pathways?]

		Receptor protein
		Extracellular signal molecule
		Intracellular signaling molecule
		Cellular response
		Effector protein

2 points

QUESTION 8

The enzyme that specifically catalyzes the conversion of ATP to cAMP is:

		Adenylyl phosphatase
		Adenylyl kinase
		Adenylyl dehydrogenase
		Adenylyl cyclase

2 points

QUESTION 9

If an animal cell suddenly lost the ability to produce GTP, what might happen to its signaling system?

		It would use ATP instead of GTP to activate and inactivate the G protein on the cytoplasmic side of the plasma membrane.
		It would not be able to activate and inactivate the G protein on the cytoplasmic side of the plasma membrane.
		It would employ a transduction pathway directly from an external messenger.
		It would be able to carry out reception and transduction but would not be able to respond to a signal.

2 points

QUESTION 10

A hormone signal is sent from the brain to other parts of the body via the bloodstream. Why do only certain cells respond to this signal?

		Hormones do not last long enough in the bloodstream to stimulate a cellular response
		Only cells that have a specific transcription factor gene will be able to respond to the signal
		Only cells in the immediate vicinity of the cell sending the signal will respond
		Only cells that have a receptor for the specific signal will be able to respond to it

cerisehedgehog846

1) A drop of urine would follow this path

a) renal pyramid/major calyx/minor calyx/renal pelvis/ureter

b) minor calyx/major calyx/renal pyramid/renal pelvis/ureter

c) renal pelvis/minor calyx/major calyx/renal pyramid/ureter

d) renal pyramid/minor calyx/major calyx/renal pelvis/ureter

2) The production of filtrate starts at

a) Loop of Henle

b) capsular space

c) distal convoluted tubule

d) proximal convoluted tubule

3) Major reabsorption of water happens by ____at the _____

a) contransport, distal convoluted tubules

b) Cl- shift, nephron loop

c) countercurrent, nephron loop

d) countercurrent, ureter

4) Angiotensin II causes production of ____to increase Na + reabsorption in the _________

a) renin; collecting duct

b) aldosterone; PCT

c) ADH; nephron loop

d) aldosterone; collecting duct

5) Most of the reabsorbed compounds from the filtrate end up in the

a) peritubular capillary

b) urine

c) nephron loop

d) DCT

6) Reabsorption of urea happens by

a) transcellular movement

b) by paracellular movement

c) by cotransport with glucose

d) by HCO3- movement

7) Transport Maximum, in urinary system terms, refers to

a) proteins performing âtransportâ out of the filtrate at maximum rate

b) the reason why a diabetic produces large volumes of diluted urine

c) excess filtrate components being urinated out of the body

d) All choices are correct

8) Urine does not drop below pH 4.5 because

a) proteins that move H+ into filtrate stop working when too much H+ builds up in filtrate

b) proteins in urine neutralize acid

c) H+ are always buffered

d) the buffering system in urine does not run out

9) Hyperkalemia will

a) activate adrenal cells to secrete aldosterone

b) can stop the heart

c) No choices are correct

d) cause reduced excitability of neurons

e) All choices are correct

10)In your body, chloride (Cl-) can be found in its highest concentration in

a) extracellular fluid

b) intracellular fluid

c) Neither choice is correct

11) Diuretic abuse leads to

a) All choices are correct

b) two choices are correct

c) No choice is correct

d) dehydration

e) athletes being accused of doping

f) hypotonic hydration

12) Long diffusion distance, low blood pressure, and impaired circulation are the result of

a) hypernatremia

b) edema

c) hyperkalemia

d) water toxicity

13) In males FSH is under feedback control by _____ and is down regulated when _________reaches high concentrations

a) inhibin, testosterone/sperm #s

b) testosterone, inhibin/sustentocyte #s

c) ADH, inhibin/sustentocyte #s

d) LH, testosterone/sperm #s

14) Testosterone production is done by ____-cells

a) posterior pituitary

b ) interstitial endocrine

c) anterior pituitary

d) sustentocytes

15) Upon _____of estrogen/progesterone, the ____phase of the uterine cycle begins

a) increase; menstrual

b) decrease; menstrual

c) increase; proliferative

d) decrease; secretory

16) Progesterone

a) All choices are correct

b) is low in the luteal phase

c) No choices are correct

d) raises in the follicular phase

e) is high along with estrogen during the follicular phase

17) Which nephron is most responsible for urine concentration?

a) cortical nephrons

b) Juxtamedullary nephrons

c) Neither

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PCB 3703C Lecture Notes - Lecture 35: Hypophyseal Portal System, Holocrine, Apocrine

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