Official NBDE Part 1 Study Q & A Thread

[tinman831]

Please post all study questions/answers for the NBDE Part 1 in this thread. Good luck!

As a side note, this is not the place for sales ads. Discussion of remembered questions appearing on the exam is also not permitted.

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[Hatico]

1st Aid 2009, Anatomy, #31

Q: Regarding the pupillary light reflex, which of the following is TRUE?
Correct A: When shining light onto the left eye, the consensual response elisit ipsilateral affering firing via CN II and subsequent contralateral efferent firing via CN III to right eye.

Why contralateral? Does CN III have any crossing?

 

[Holly J]

I can show you math part, but I'm confused with unprotonated\protonated form.

pH(A) = pK(A) + log ( [A-]/[HA] ) ;
log ([A-]/[HA] ) = pH(A) - pK(A) ;
log ([A-]/[HA] ) = 1 because 7.4 - 6.4 =1;
[A-]/[HA] = 10 because 10exp1 = 10;



Which one form is protonated? For me HA is more protonated than A-.
So, if [A-]/[HA] = 10 than [HA]/ [A-] = 0.1 ;
My answer is protonated/unprotonated = 0.1.

Hey thanks! That was simple.
One thing...the ratio is unprotonated/protonated... so the answer is 10 only.

 

[Holly J]

1st Aid 2009, Anatomy, #31

Q: Regarding the pupillary light reflex, which of the following is TRUE?
Correct A: When shining light onto the left eye, the consensual response elisit ipsilateral affering firing via CN II and subsequent contralateral efferent firing via CN III to right eye.

Why contralateral? Does CN III have any crossing?

Its not just contralateral. But both the pupils react.
Afferents-optic nerve reach the pretectal nucleus...then to the edinger westphal nucleus...then to the oculomotor(efferent)....pupil contrict on both sides.

Regarding Metabolic alkalosis....compensatory mechanism is excretion of bicarbonate by the kidneys not absorption.

Vitamin C deficiency-has no direct effects on the enamel but yes it effects the dentin.

 

[Hatico]

Hey thanks! That was simple.
One thing...the ratio is unprotonated/protonated... so the answer is 10 only.

Its not just contralateral. But both the pupils react.
Afferents-optic nerve reach the pretectal nucleus...then to the edinger westphal nucleus...then to the oculomotor(efferent)....pupil contrict on both sides.

Yes
Protonation is adding of protone to ion or molecule. [A-] + [H+] = [HA]. So, [HA] is protonated form of [A-]. So, [A-] - unprotonated, [HA] - protonated form.

If light shine into one eye (other one is closed) than pupil constrict on the both open and closed eyes. )

 

[Holly J]

Yes
Protonation is adding of protone to ion or molecule. [A-] + [H+] = [HA]. So, [HA] is protonated form of [A-]. So, [A-] - unprotonated, [HA] - protonated form.

If light shine into one eye (other one is closed) than pupil constrict on the both open and closed eyes. )

Yes...thats what the question is saying-light is shone in unilateral eye only...not bilateral....but the response is in both the eyes!

 

[DancingKoala]

1) The chemical mediator at the neuroeffector junction in sweat gland is ?
Answer = ACH

is sweat gland part of PNS because SNS releases ACH and then Nor-epinephrine whereas PNS releases ACH twice?


2) The absolute refractoery period of a nerve Action potential is determined by
answer = the duration of sodium inactivation gate closure

Absolute refractory period is when Na is opened so shouldn't the answer be the duration of Sodium gate opened?

3) the maximal number of impulses that a nerve fiber can carry is determined by the duration of the absolute refractory period.
I don't understand what this means. Could someone explain this to me?


4) during negative after potential, nerve fibers are hyperexcitable. During positive after potential, nerve fibers are hypoexcitable.
When or where is this positive and negative after potential located in the graph? I only know about depolarization, repolarization, and hyperpolarization.

 

[Hatico]

1) The chemical mediator at the neuroeffector junction in sweat gland is ?
Answer = ACH

is sweat gland part of PNS because SNS releases ACH and then Nor-epinephrine whereas PNS releases ACH twice?


2) The absolute refractoery period of a nerve Action potential is determined by
answer = the duration of sodium inactivation gate closure

Absolute refractory period is when Na is opened so shouldn't the answer be the duration of Sodium gate opened?

3) the maximal number of impulses that a nerve fiber can carry is determined by the duration of the absolute refractory period.
I don't understand what this means. Could someone explain this to me?


4) during negative after potential, nerve fibers are hyperexcitable. During positive after potential, nerve fibers are hypoexcitable.
When or where is this positive and negative after potential located in the graph? I only know about depolarization, repolarization, and hyperpolarization.

1) Postganglionic SNS fibers release NE exept sweat glands and vessels of muscles.
2) Absolute refractory period = Na+ gate closure
3)
4) I think negative after potential is depolarisation - membrane are hyperexcitable. Then become not excitable (absolute refractory) , then repolarization = low excitability (relative refractory period)

 

[ionomer]

1) Postganglionic SNS fibers release NE exept sweat glands and vessels of muscles.
2) Absolute refractory period = Na+ gate closure
3)
4) I think negative after potential is depolarisation - membrane are hyperexcitable. Then become not excitable (absolute refractory) , then repolarization = low excitability (relative refractory period)

For question number 1) , another sympathetic exception is the Adrenal gland. The adrenal gland is devoid of postganglionic fibers so it the preganglionic sympathetic fibers the do the jobs via acetylcholine

 

[Hatico]

For question number 1) , another sympathetic exception is the Adrenal gland. The adrenal gland is devoid of postganglionic fibers so it the preganglionic sympathetic fibers the do the jobs via acetylcholine

Thank you!! One of the sourses says that medulla of the adrenal glands contain only N1 receptors = postganglionic SNS mediator is ACh.

 

[DancingKoala]

1) what are found in kidney cortex and medulla?
I think -
cortex = bowman's capsule, PCT, DCT
Medulla = loop of henle, collecting tubule

2) why is IgG increased in periodontal disease patients?
I don't know

3) what are hormones increased/decreased in pregnant patients?

I think - FSH, estrogen, LH increase but these are before pregnancy so I think these go down but CGH is the only hormone increased

4) at the radio-ulnar joint, what muscle is used in extension?
Brachilis, Extensor radialis, Extensor ulnaris

I think all of them are correct.

5) maximal intercuspation of premolars?
I have seen many questions asking about molar occlusion but I've never had a question asking about premolar occlusion so I don't have good information about premolar occlusion rules. For example, does Max 2nd molar cusp hit the marginal ridges between mand 2nd premolar and mand 1st molar or does it hit 2nd premolar fossa? How about Max 1st premolar, mand 1st premolar?

Thanks in advance.

 

[Hatico]

In one of the Q Frontal bone is shown paired. When we are talking about paired/unpared bones/organs we mean developing or developed bones/organs? If Frontal bone is paired than the tongue seems to be paired organ

 

[DancingKoala]

In one of the Q Frontal bone is shown paired. When we are talking about paired/unpared bones/organs we mean developing or developed bones/organs? If Frontal bone is paired than the tongue seems to be paired organ

I don't think frontal bone is paired unless it's from First Aid.

 

[PooKan]

amplitude of an action potential can be increased most easily by increasing which of the following concentration?
answer- extracellular sodium
how? when sodium enters the cell thn only action potential is generated right so tthe answer has to be intracellular sodium..
plz help...

 

[Hatico]

amplitude of an action potential can be increased most easily by increasing which of the following concentration?
answer- extracellular sodium
how? when sodium enters the cell thn only action potential is generated right so tthe answer has to be intracellular sodium..
plz help...

"Hodgkin and Katz (1949) were the first to show this for the giant axons of squid neurons. The amplitude is highly influenced by the Na+ concentration. (This and similar studies led to a Nobel price for Hodgkin in 1963)
Depolarisation of the axon leads to activation of Na+-channels, that is: they open. This allows flow of Na+ accross the membrane of the neuron. The electrochemical gradient accross the membrane leads ot a current of Na+ ions into the cell. This leads to further depolarisation and futher opening of Na channels. With low Na+ outside the neuron, less Na+ can enter the cell, the action potential gets first smaller and finally with too low concentration ceases fully. "

 

[DancingKoala]

amplitude of an action potential can be increased most easily by increasing which of the following concentration?
answer- extracellular sodium
how? when sodium enters the cell thn only action potential is generated right so tthe answer has to be intracellular sodium..
plz help...

It's true that Na comes into the cell and cause AP but why does it come in? It's because of concentration gradient difference between in and out. What if inside is higher than outside? then Na will go outside and no AP will happen, right? What if in and out are the same? Then there is no net movement of Na and no AP will occur. AP occurs only if Na comes in and depolarizes the cell. By making the concentration gradient different (More Na outside, less Na inside), we can achieve AP.

 

[Holly J]

Can somebody tell me precisely where the ADH is released in kidneys. According to ASDA its released in collecting tubules...but ADH receptors are present in distal tubule...and yet max. water absorption occurs in proximal tubules! Now thats confusing!

 

[DancingKoala]

Can somebody tell me precisely where the ADH is released in kidneys. According to ASDA its released in collecting tubules...but ADH receptors are present in distal tubule...and yet max. water absorption occurs in proximal tubules! Now thats confusing!

I believe that ADH is released to both Distal convoluted tubule and collecting duct.
Max water absorption maybe occurring in Proximal convoluted tubule but I don't think it uses ADH.
I think most of stuffs (includes glucose, water....etc) are reabsorbed in proximal convoluted tubule using ATP but I don't think it uses ADH here.
I remember reading that 2/3 of the material that are filtered are reabsorbed in proximal convoluted tubule.

 

[Holly J]

I believe that ADH is released to both Distal convoluted tubule and collecting duct.
Max water absorption maybe occurring in Proximal convoluted tubule but I don't think it uses ADH.
I think most of stuffs (includes glucose, water....etc) are reabsorbed in proximal convoluted tubule using ATP but I don't think it uses ADH here.
I remember reading that 2/3 of the material that are filtered are reabsorbed in proximal convoluted tubule.

Thanks Dancingkoala! But it remains kinda confusing. Water reabs. doesnt use any ATP...nor is the ADH of any use in proximal tubule. Then whats the big hype about ADH...Renin etc etc when its use is just minimal! Nevermind I guess I will do some more reading about it. Thanks again!

 

[PooKan]

thankz Hatico and Koala..

 

[Hatico]

Can somebody tell me precisely where the ADH is released in kidneys. According to ASDA its released in collecting tubules...but ADH receptors are present in distal tubule...and yet max. water absorption occurs in proximal tubules! Now thats confusing!

It's from my notebook :
H2O reabsorbtion occures in each segment of nephron except accending loop ( maximal reabsorbtion - distal convolutive and collectind duct). ADH-controlled part is COOLECTING GUCT.

 

[Holly J]

It's from my notebook :
H2O reabsorbtion occures in each segment of nephron except accending loop ( maximal reabsorbtion - distal convolutive and collectind duct). ADH-controlled part is COOLECTING GUCT.

Thanks. But....Distal and collecting duct both are the only segments that are almost impermeable to water(except when controlled by ADH)! Correction*

 

[DancingKoala]

Thanks. But....Distal and collecting duct both are the only segments that are almost impermeable to water(except when controlled by ADH)! Correction*

Let me finish this argument by bringing 3 related questions from the released exam.

- ADH receptors in the nephron are located on the tubular membrane of distal tubule.
o ADH (antidiuretic hormone) functions to regulate the water permeability of the distal tubule and the collecting duct.
o Antidiuretic hormone acts to increase permeability of distoconvoluted tubules and/or collecting ducts to water.

These are from old exam and they repeated it 3 times (confirm confirm and confirmed ). ADH acts on distal convoluted tubule and collecting duct.
If ASDA said it 3 times, who can argue?

 

[DancingKoala]

1) Most congenitally missing permanent tooth is?
answer= ???

2) Design for restoring a complete and functional occlusal surface depends on the position of the tooth in the arch, direction of lateral shift in working condyle, contour of articular eminence, and amount of vertical overlap of anterior teeth.
Q. could someone explain to me why each of them are important?


3) If the condyles were steeper, what would be the shape of the teeth?
Answer = ???

4) mesial contact area of molars?
answer = ??
Is it middle 3rd or junction between occlusal and middle 3rd?

5) Which lingual embrasure is smaller than facial embrasure?
answer = ??
I think it's either distal or mesial of mand 1st molar cuz it has lingual surface wider than facial surface but I am not sure.

6) True/False?
a. in cervical cross section, the root of a mand canine is flattened in a mesiodistal direction
b. in cervical cross section, the root of a mand canine is irregularly oval
c. A cross section at mid root of a permanent mand central incisor show that the pulp cavity is flatteened mesiodistally
answer = ??
Both mandibular canine and central incisors have oval shape. If they got flat mesiodistal, doesn't that mean it's a triangular shape (max central insicor) because of flat base is at mesiodistal ?

 

[Hatico]

1) 20,29 (after wisdom teeth)
3) should be higher crown and sharper cusps
4) middle 1\3
5) i think it is lateral incisor - canine contact

 

[ionomer]

I don't think frontal bone is paired unless it's from First Aid.

According to dental decks, there are 7 unpaired and 10 paired bones of the skull.
The 7 unpaird are Frontal, Ethmoid, Sphenoid, Hyoid, Occipital Mandible and Vomer bones.

My Qestion - Why is the mandible, two of them joined at the symphysis, labeled as an unpaired bone????

 

[DancingKoala]

According to dental decks, there are 7 unpaired and 10 paired bones of the skull.
The 7 unpaird are Frontal, Ethmoid, Sphenoid, Hyoid, Occipital Mandible and Vomer bones.

My Qestion - Why is the mandible, two of them joined at the symphysis, labeled as an unpaired bone????

I think paired bones are the ones that u can actually grab with two of your hands and separate into two.
I don't remember seeing a crack on mandible or any of the 7 bones that you listed as unpaired.

 

[PooKan]

phage conversion c responsible for which of the following?
-transformation of bacteria
-production of pyrogenic toxin (ans)
y cant it be first option?

uncomplicated healing of a wound healing by secondary intention ,observed microscopically at 3 days is most likely to show evidence of which of the following?
-mature cicatrix
-keloid formation
-granulomatous inflammation
-lack of acute inflammation
-ulceration of epithelial surface(ans)
y cant it be 3rd option?

which of the folowing bacterial vaccines is given routinely in USA?
-DPT ..
y only this one?

 

[vdt2009]

2) Lack of what vitamins during tooth formation most likley induces enamel hypoplasia.
a. A
b. C
c. D
answer = A and D
why can't vitamin C be the answer?

Another question I read said
"normal production of sound enamel and dentin requiers adequate amounts of vitamin A, C, and D"
"Vitamin A, C, D are involved in tooth development and calcification"

Could it be possible that C is only for collagen formation required for dentin and cementum only?

Enamel hypoplasia is the defect of the teeth in which the tooth enamel is hard but thin and deficient in amount. This is caused by defective enamel matrix formation with a deficiency in the cementing substance.
i.e properly calcified.
collagen is not a component for enamel matrix , n vitamin C is require for collagen synthesis ...they r specifically asking about hypoplasia i.e defective matrix formation not minralisation ,,,so ans would be A and D

 

[Holly J]

phage conversion c responsible for which of the following?
-transformation of bacteria
-production of pyrogenic toxin (ans)
y cant it be first option?
Transformation is entry of naked DNA into the bacterium. Phage conversion is where the virus attaches to the surface of the bacteria and the DNA is released into the bacterium.
uncomplicated healing of a wound healing by secondary intention ,observed microscopically at 3 days is most likely to show evidence of which of the following?
-mature cicatrix
-keloid formation
-granulomatous inflammation
-lack of acute inflammation-This is never present in healing-not in secondary or primary healing methods.
-ulceration of epithelial surface(ans)-definitely seen in secondary healing...forming granulation tissue.
y cant it be 3rd option?

which of the folowing bacterial vaccines is given routinely in USA?
-DPT ...
y only this one? Hey every country has their own protocol...the most prevalent disease requires the vaccines,so Diptheria/whooping cough must be common there.

 

[DancingKoala]

1) Increase in extracellular Calcium increase strength of muscle contraction
Q. I thought Calcium from Sarcoplasmic Reticulum is released and cause muscle contraction so shouldn't it be intracellular calcium?


2) which muscle is used for circumduction of arm and what innervates it?

3) which muscle is used for extension of radio-ulnar joint and what innervates it?

 

[PooKan]

host responses against encapsulated strepto pneumoniae s mediated by-
-IgE
-IgD
-opsonins (ans)
-cytotoxic Tc lymphocytes
-delayed hypersensitivity
y cant the answer be cytotoxic lymphocytes....they are supposed to work as host defence against viruses, bacteria, fungi n parasites right?

 

[PooKan]

so phage conversion means viruses attach to the bacteria and release the DNA but do not undergo lytic phase....am i right?

 

[PooKan]

just want to be sure of :-
pilus has 2 functions:-
-enables bacteria to colonise on cell surface called as short pili or fimbriae ,which is the main function and
-enables conjugation i.e., transfer of DNA called as long pili.....
am i right?

 

[DancingKoala]

host responses against encapsulated strepto pneumoniae s mediated by-
-IgE
-IgD
-opsonins (ans)
-cytotoxic Tc lymphocytes
-delayed hypersensitivity
y cant the answer be cytotoxic lymphocytes....they are supposed to work as host defence against viruses, bacteria, fungi n parasites right?

I could be wrong but I would pick opsonins simply because I think delayed hypersensitivity = T lymphocytes.

 

[Holly J]

so phage conversion means viruses attach to the bacteria and release the DNA but do not undergo lytic phase....am i right?

Conversion of a normal bacteria into a virulent strain is phage conversion-it can be lytic or lysogenic.

 

[Holly J]

host responses against encapsulated strepto pneumoniae s mediated by-
-IgE
-IgD
-opsonins (ans)
-cytotoxic Tc lymphocytes
-delayed hypersensitivity
y cant the answer be cytotoxic lymphocytes....they are supposed to work as host defence against viruses, bacteria, fungi n parasites right?

Important point to be noticed here is "encapsulated". When capsule is present,first it need opsonins which forms the target so that the antibodies can act.

 

[Holly J]

1) Increase in extracellular Calcium increase strength of muscle contraction
Q. I thought Calcium from Sarcoplasmic Reticulum is released and cause muscle contraction so shouldn't it be intracellular calcium?
Yes calcium is carried into the cell which activates the Ach receptors....which leads to the contraction.

2) which muscle is used for circumduction of arm and what innervates it?
circumduction of arm is nothing but the whole shoulder movement-involves almost all the muscles of shoulder and upp arm.
3) which muscle is used for extension of radio-ulnar joint and what innervates it?The only movement that occur at radio-ulnar joint is pronation and suppination. It doesnt "extend" as such.

 

[DancingKoala]

SR is extracellular structure unlike ER in non-skeletal muscle cells?

 

[PooKan]

each of the following statements describes characteristic feature of ischaemic heart disease EXCEPT one. that is :-
-usually results from complete occlusion of one or more coronary arteries(ans)
-imbalance btw myocardial oxygen demand and supply
-men over 60yrs and women over 70yrs
-contributing factors are low levels of low density lipoprotein and hypertension
all the factors are correct right..?? ischemic heart disease s due to occlusion n the coronary arteries....y have they marked this answer as right...

 

[PooKan]

Conversion of a normal bacteria into a virulent strain is phage conversion-it can be lytic or lysogenic.

ohh ok...in decks its given as bacteriophage causes infection in 2 courses-
1)lytic (also called virulent) phase- where host s destroyed
2)lysogenic(also called temperate) phase- host cells are not destroyed..
is this right? if not can u plz explain me this lytic n lysogenic phases....thankz

 

[Holly J]

SR is extracellular structure unlike ER in non-skeletal muscle cells?

Sorry for the confusion...But in nonskeletal muscle....extracellular calclium concentration is important because it induces the SR to release the stored Ca...but a process called "calcium induced calcium release".

 

[Holly J]

ohh ok...in decks its given as bacteriophage causes infection in 2 courses-
1)lytic (also called virulent) phase- where host s destroyed
2)lysogenic(also called temperate) phase- host cells are not destroyed..
is this right? if not can u plz explain me this lytic n lysogenic phases....thankz

You got it this time!

 

[DancingKoala]

..

 

[Hatico]

each of the following statements describes characteristic feature of ischaemic heart disease EXCEPT one. that is :-
-usually results from complete occlusion of one or more coronary arteries(ans)
-imbalance btw myocardial oxygen demand and supply
-men over 60yrs and women over 70yrs
-contributing factors are low levels of low density lipoprotein and hypertension
all the factors are correct right..?? ischemic heart disease s due to occlusion n the coronary arteries....y have they marked this answer as right...

Correct answer leads to Myocardial Infarction only. Every Myocardial Infarction is Ischaemic Heart Disease , but not every Ischaemic Heart Disease is Myocardial Infarction.

 

[DancingKoala]

Q1. Which of the following is a property of gel electrophoresis?
1) dependent on the pH of the molecule
2) determines protein molecular weights.

The correct answer is 2.
But! I thought the answer should be 1.
I had bunch of old released test question saying that pH lower than the isoelectric point will move toward negative pole and it will stay the same if pH is equal to the isoelectric point.




Q2. Sickle Cell Hemoglobin (Hb S) differs from normal hemoglobin (Hb A) in which of the following ways?
1) Hb S tends to polymerize in the deoxy form
2) Hb S shows a reduced ability to bind oxygen at the same pO2

The answer is 1.
But! isn't 1 and 2 the same?
If Hb S loves to be in deoxy form that means it doesn't bind to oxygen well which means it shows a reduced ability to bind oxygen.




Q3. which of the following will be released if there is a deficiency in iodine?
answer = TSH

low iodine means low T3 and T4 so it's true that we need more of these. What I want to know is, even if there is a secretion of TSH by positive feedback mechanism, we still can't produce T3 or T4 unless there is iodine, right?

 

[iverson3504]

Hey yall, quick and easy question..

If a patient wants a tooth extracted but you do do not see any reason for it to be taken out, what do you do?

This is not from decks or anything, I'm just wondering how to answer this kind of q if it pops up.

Thanks

 

[DancingKoala]

Hey yall, quick and easy question..

If a patient wants a tooth extracted but you do do not see any reason for it to be taken out, what do you do?

This is not from decks or anything, I'm just wondering how to answer this kind of q if it pops up.

Thanks

If you lie to a patient and extract a tooth that has no reason to be extracted then that's unethical.
But~ If a patient asked for it, I think u should go for it.

 

[ionomer]

Hey yall, quick and easy question..

If a patient wants a tooth extracted but you do do not see any reason for it to be taken out, what do you do?

This is not from decks or anything, I'm just wondering how to answer this kind of q if it pops up.

Thanks

This is under what is called "AUTONOMY". its the patients right so you go for it.

 

[Holly J]

Q1. Which of the following is a property of gel electrophoresis?
1) dependent on the pH of the molecule
2) determines protein molecular weights.

The correct answer is 2.
But! I thought the answer should be 1.
I had bunch of old released test question saying that pH lower than the isoelectric point will move toward negative pole and it will stay the same if pH is equal to the isoelectric point.

Thats right,I read that too. 1st look and I would mark pH too! But the whole gel electrophoresis process is done to separate molecules based on their sizes only. pH is just a factor which causes migration of the molecules. The gel separates the larger molecules from the smaller molecules while they are migrating towards the opposite charges.

 

[DancingKoala]

I have a question about inferior alveolar injection.
If needle enters parotid gland during inferior alveolar injection or mandibular block injection, why does it paralyze facial expression?
Facial expression is innervated by CN VII wheras parotid gland is innervated by CN IX so I am having hard time understanding this.