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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[PooKan]

I m not sure with 1 but you are correct with 2 and 3.

2) As far as I understand (I actually studied this about 5 hrs ago ), you know how posterior teeth have a cusp hitting central fossa...etc? When you are moving it laterally (working; bennett movement), it will move from central fossa to groove(facial groove). For example, distobuccal cusp of mand 1st molar that was hitting the central fossa of max 1st molar is gonna pass the facial groove of max 1st molar, right (m i right?) so it's true that groove direction would be affected by Bennett movement when it comes to posterior.
When it comes to anterior teeth, I am not positive whether i understood this correctly or not but I think mandibular cusps are scretching(i don't know if this is right term LOL) the lingual concavity of max teeth.

3) A = T (in DNA replication) or U (when paired into RNA)
G = C (in both DNA and RNA)
5 = 3
FYI, A and T are connected via 2 H bond whereas G and C are connected via 3 H bond so more contents of GC provide more stability and higher melting point.

Now, if you are interested in learning more about Bennett movement, maybe you can answer my question above as well

edit: I thnk I might be able to answer 1st one
our body got more IgG then any other antibodies followed by IgA.
IgM shows up 1st when you encounter a specific antigen for the very first time.
But if you encounter it for the 2nd time, IgG will show up even faster than IgM.
Since the question said he encountered it for the 3rd time, I think that's what this question was asking and IgG is the correct answer.

thankz got it..

 

[ionomer]

RNA polymerse binds to which of the following DNA regions?

A) Repressor

B) Initiator

C) Operator

D) Terminal codon

E) Promoter

 

[Holly J]

RNA polymerse binds to which of the following DNA regions?

A) Repressor

B) Initiator

C) Operator

D) Terminal codon

E) Promoter-ANSWER

 

[molar65]

Which of the following statements is true?
The MORE the VERTICAL overlap, the TALLER the cusps MUST be
The MORE the HORIZONTAL overlap, the SHORTER the cusps MAY be
The LESS the VERTICAL overlap, SHORTER the cusps MUST be
The MORE the HORIZONTAL overlap, the TALLER the cusps MAY be
this ques is from decks [09-10] num 89th deck for dental anatomy
Could anyone please explain the role of the words MUST and MAY in answering this question.I am just confused.

 

[PooKan]

I did not understand this question....plz explain
Juxtamedullary and cortical nephrons differ primarily in?
ans:- length of thin segment of loop of Henle

Swelling from angle of mandible and lateral neck most likely resulted from deflection of exudates by which of the following structures?
-sublingual gland
-mylohyoid muscle (ans)
-hyoglossus muscle
-ptergomandibular raphae
-buccopharngeal fascia

 

[Holly J]

I did not understand this question....plz explain
Juxtamedullary and cortical nephrons differ primarily in?
ans:- length of thin segment of loop of Henle

Swelling from angle of mandible and lateral neck most likely resulted from deflection of exudates by which of the following structures?
-sublingual gland
-mylohyoid muscle (ans)
-hyoglossus muscle
-ptergomandibular raphae
-buccopharngeal fascia

1.There are two types of nephrons-juxtamedullary and cortical.
JM-extends from cortex to medulla( long henle loop)
Cortical-doesnt go beyond cortex(therefore short henle loop)

2.I guess thats submandibular space infection...therefore swelling of angle of mandible,where the mylohyoid attaches and divide it from the sublingual space infection.

 

[Hatico]

I did not understand this question....plz explain
Juxtamedullary and cortical nephrons differ primarily in?
ans:- length of thin segment of loop of Henle


Swelling from angle of mandible and lateral neck most likely resulted from deflection of exudates by which of the following structures?
-sublingual gland
-mylohyoid muscle (ans)
-hyoglossus muscle
-ptergomandibular raphae
-buccopharngeal fascia

1) Nephrons classification is based on length of loop of Henle
2) Check Decks, Anatomy, Nerves - I saw answer there. But I cannot explain it. As far as I can imagine this process - Mylohyiod muscle can "push" pus from Submandibular space to Lateral Pharyngeal space. If Lateral Pharyngeal space is "angle of mandible and lateral neck" than I agree with this answer.



Holly answered... I did not see.

 

[tinman831]

df

 

[DancingKoala]

"An infection spreading by way of the lymphatic system from the vermiform appendix first enters the blood stream at the brachiocephalic vein."

Appendix is all the way at the bottom whereas brachiocephalic vein is all the way at the top of the upper extremity so I am having hard time understanding how to understand this. Could someone explain this to me?




And why is the greatest volume of blood can be found in systemic veins?

 

[PooKan]

1)Hep C causes chronic hepatitis or hepatocellular carcinoma most commonly?

2)what does scarring of left ventricle means?

3)Ameloblasts will form enamel if which of these cells are present?
-stellate reticulcum
-stratum intermedium (ans)
-langerhans and merkel cells
-outer enamel epithelium
-reduced enamel epithelium
Ameloblasts form enamel from 'inner enamel epithelium' and reduced enamel epithelium has both inner and outer enamel epithelium right ? so the answer should be REE but the ans s stratum intermedium..how?

 

[PooKan]

thankz Holly and Hatico for the explanation...

 

[DancingKoala]

1)Hep C causes chronic hepatitis or hepatocellular carcinoma most commonly?

2)what does scarring of left ventricle means?

3)Ameloblasts will form enamel if which of these cells are present?
-stellate reticulcum
-stratum intermedium (ans)
-langerhans and merkel cells
-outer enamel epithelium
-reduced enamel epithelium
Ameloblasts form enamel from 'inner enamel epithelium' and reduced enamel epithelium has both inner and outer enamel epithelium right ? so the answer should be REE but the ans s stratum intermedium..how?

Hep C = it can cause chronic hepatitis, hepatocellular carcinoma, and also Cirrhosis. 80% of patients with hepatocellular carcinoma has Cirrhosis. But! Carcinoma~ as much as it sounds, is very dangerous and rare. Chronic hepatitis is more common. I know exactly where you got this question from cuz I was confused too (it was only about 2 weeks ago ) and someone told me that the most common form is chronic hepatitis although the others can happen in more serious cases.

I don't know the 2nd question, maybe someone ate something sharp like fish bone and it scretched the ventricle JK

for the 3rd one, I think it's basically asking what signals ameloblast to make enamel and the signal is the presence of stratum intermedium.
FYI, preameloblast turns into active ameloblast when it gets poked by odontoblast process which is basically a signal

 

[DancingKoala]

1) The partial pressure of oxygen in arterial blood is lower than that in alveoli. This condition suggested is thickening of the alveolar membrane.

2) what is "total osmotic pressure"?

Can someone tell me what this means?

 

[Hatico]

1)Hep C causes chronic hepatitis or hepatocellular carcinoma most commonly? chronic hepatitis > cirrosis> hepatocellular carcinoma

2)what does scarring of left ventricle means? regeneration after myocardial infarction?

3)Ameloblasts will form enamel if which of these cells are present?
-stellate reticulcum
-stratum intermedium (ans)
-langerhans and merkel cells
-outer enamel epithelium
-reduced enamel epithelium
Inner enamel epithelium (main role-ameloblasts) and Stratum intermedium(additional role) take part in formation of the enamel. o

 

[Holly J]

"An infection spreading by way of the lymphatic system from the vermiform appendix first enters the blood stream at the brachiocephalic vein."

Appendix is all the way at the bottom whereas brachiocephalic vein is all the way at the top of the upper extremity so I am having hard time understanding how to understand this. Could someone explain this to me?




And why is the greatest volume of blood can be found in systemic veins?

Lymphatic drainage of appendix ->sup.mesenteric->thoracic duct->subclavian->left brachiocephalic...whewwwww!!!

Okie I dint get the next question....yes greatest amount of blood flows in systemic circulation....but why? It seems to me like you are asking-why is there so much of blood in veins! Ask the lord!

 

[Hatico]

To Koala.
1)Toracic duct and R. limphatic duct joint subclavian vein. Vermiform appendices are additional formation on brachiosephalic veins close to junctions with lymphatic ducts from lower lip.

 

[DancingKoala]

Lymphatic drainage of appendix ->sup.mesenteric->thoracic duct->subclavian->left brachiocephalic...whewwwww!!!

Okie I dint get the next question....yes greatest amount of blood flows in systemic circulation....but why? It seems to me like you are asking-why is there so much of blood in veins! Ask the lord!

Thanks. For the 2nd one, I was just curious why systemic vein has more blood than systemic artery...etc.



Here is another question.

A major effect of Sickle cell anemia is decreased solubility of the deoxy form of hemoglobin.

Sickle cell anemia happens when RBC becomes sickle shape and can't carry O2 well. Shouldn't Deoxy form (deoxyhemoglobin) increased instead of decreased? Deoxy means it doesn't have O2 bound to the hemoglobin.

 

[Hatico]

Here is another question.

A major effect of Sickle cell anemia is decreased solubility of the deoxy form of hemoglobin.

Sickle cell anemia happens when RBC becomes sickle shape and can't carry O2 well. Deoxy form (deoxyhemoglobin) has low affinity for O2 so shouldn't deoxy form increased instead of decreased?

No. Solubility of hemoglobine is checked by reduction test. HbG S forms crystalls (less soluble) - positive test, but normal HbG stays transparant (more soluble) - negative test.

 

[Hatico]

thank u...
for pain from body of mandible -its auriculotemporal n-given in ans sheet...

There are many mistakes. Auriculotemporal carry sensory fibers to ramus of mandible, inferior alveolar - to body of mandible. What do you think about this answer?

 

[ionomer]

I did not understand this question....plz explain
Juxtamedullary and cortical nephrons differ primarily in?
ans:- length of thin segment of loop of Henle

Swelling from angle of mandible and lateral neck most likely resulted from deflection of exudates by which of the following structures?
-sublingual gland
-mylohyoid muscle (ans)
-hyoglossus muscle
-ptergomandibular raphae
-buccopharngeal fascia

Most infections of this type are as a result of carious posterior mandibular molars (7 and 8) because their root in the mandibule go beyond the attachment of the mylohyoid muscle line of attachment and this infection process EASILY spreads to the spaces and neck.

 

[ionomer]

Lymphatic drainage of appendix ->sup.mesenteric->thoracic duct->subclavian->left brachiocephalic...whewwwww!!!

Okie I dint get the next question....yes greatest amount of blood flows in systemic circulation....but why? It seems to me like you are asking-why is there so much of blood in veins! Ask the lord!

Holly J is right but also, the veins are seen or should i say are hollow tubes with no musculature of their own to pump blood. They only contain valves which prevent back flow to the capillaries. They are blood reservoir, the action of skeletal muscles help to empty the blood in veins and a more reason they are more superficial than arteries.

The arterioles have most pressure so are the major regulator of blood pressure while the veins have the most volume.

 

[DancingKoala]

1)I have a question about bicep (or radio-ulnar joint).
1 question says it's flexion at the gleno humeral and the humero ulnar joint.
I understand this so far.

But then the next question says
Biceps brachii is a primary supinator at the radio-ulnar joint. Where is this joint? Is this joint where the elbow is or the wrist is?


2) Fast vs. slow twitch
Fast has
- higher myosin ATPase activity
- fewer capillaries
- more SR
- more glycolytic enzymes
- less mitochondria

Is there a way to understand why? or do we just need to memorize this?
What I don't understand is that less mitochondria means less ATP but there are more ATPase activity.
More SR would mean more calcium but why do we need more calcium when running a short distance (fast twitch)
when we could use more for long distance running (slow twitch)?
And why do we need more glycolytic enzymes?

 

[ionomer]

1)I have a question about bicep (or radio-ulnar joint).
1 question says it's flexion at the gleno humeral and the humero ulnar joint.
I understand this so far.

But then the next question says
Biceps brachii is a primary supinator at the radio-ulnar joint. Where is this joint? Is this joint where the elbow is or the wrist is?


2) Fast vs. slow twitch
Fast has
- higher myosin ATPase activity
- fewer capillaries
- more SR
- more glycolytic enzymes
- less mitochondria

Is there a way to understand why? or do we just need to memorize this?
What I don't understand is that less mitochondria means less ATP but there are more ATPase activity.
More SR would mean more calcium but why do we need more calcium when running a short distance (fast twitch)
when we could use more for long distance running (slow twitch)?
And why do we need more glycolytic enzymes?

There are actually 2radioulnar joints proximal (close to the elbow) and distal (@ the wrist)


The fast muscles are used for very powerful but short duration burst of activity so they have less mitochrondria fewer capillaries (so they appear white) while the slow oxidative muscle type are also called red muscle cos the are rich in capillaries and mitochrondria and myoglobin and can sustain aerobic oxidation.

I hope im right oooo

 

[PooKan]

which of the following glands s purely mucous?
-parotid
-palatine (ans)
-sublingual
-von ebner
-submandibular
even sublingual gland is purely mucous...thn y they gave as palatine...

condyle on laterotrusive mov rotates around
-vertical axis and translates laterally

recovery from mumps infection confers life long immunity..which of the following types of immuntiy
-innate
-natural active (ans)
-natural passive
-artificial active
-artifical passive
i thought mumps vaccination s given and thn life long immunity so it must be artifical active...how come natural active?

condyle in laterotrusive side moves rotates about vertical axis and moves laterally....
how can it move along vertical axis..condyles moves only on horizontal axis right

 

[Holly J]

which of the following glands s purely mucous?
-parotid
-palatine (ans)
-sublingual
-von ebner
-submandibular
even sublingual gland is purely mucous...thn y they gave as palatine...
Sublibgual-mostly mucous...yet some serous secretions.

condyle on laterotrusive mov rotates around
-vertical axis and translates laterally

recovery from mumps infection confers life long immunity..which of the following types of immuntiy
-innate
-natural active (ans)
-natural passive
-artificial active
-artifical passive
i thought mumps vaccination s given and thn life long immunity so it must be artifical active...how come natural active?
The question is about mumps infections....not about mumps vaccination!If the question was about MMR vaccination then definitely-artificial active.

condyle in laterotrusive side moves rotates about vertical axis and moves laterally....
how can it move along vertical axis..condyles moves only on horizontal axis right
Horizontal axis-opening/closing movements.
Vertical axis-lateral movements.

Hope that works.

 

[Hatico]

.condyles moves only on horizontal axis right

I guess you mean "horizontal plate" instead "horizontal axis"

 

[DancingKoala]

I guess you mean "horizontal plate" instead "horizontal axis"

Ah...so if something is moving horizontally (left or right), we say that it's moving horizontal plate along the vertical axis ? That's very confusing


Here are my next questions


1) Sodium is least permeable to cell membrane compared to O2, CO2, H2O, and ethanol. Why is Sodium least permeable?

one of my notes says only small and non polar can penetrate membrane.
Sodium is just one Na+ ion whereas CO2, H2O,.... all are compounds so i think they must be bigger than sodium. And I don't know if Na+ is polar or nonpolar.

2) glycoprotein is made in golgi apparatus
isn't all protein made from rough ER?

3) Among Proximal convoluted tubule, loop of hanle, distal convoluted tubule, and collecting duct, which one uses the most ATP?
I think this is asking about active transport but I don't know where it happens.


4) gall bladder is unlike stomach, duodenu, jejunum, and colon in that it doesn't contain
a) submucosa
b) muscularis externa
wiki says b is the answer. Released test says A is the answer. Some say both are the answers

 

[Holly J]

Ah...so if something is moving horizontally (left or right), we say that it's moving horizontal plate along the vertical axis ? That's very confusing


Here are my next questions


1) Sodium is least permeable to cell membrane compared to O2, CO2, H2O, and ethanol. Why is Sodium least permeable?
There are so many factors here...polarity,size, type of transportation, etc
Sodium being larger molecule cannot diffuse like O2/CO2 and hence...lower permeability and require an active transportation.

one of my notes says only small and non polar can penetrate membrane.
Sodium is just one Na+ ion whereas CO2, H2O,.... all are compounds so i think they must be bigger than sodium. And I don't know if Na+ is polar or nonpolar.

2) glycoprotein is made in golgi apparatus
isn't all protein made from rough ER?
This is what I got-Dont know how much of it is right though!
Glycoproteins are created in the nucleolus (in the Nucleus) the messenger RNA then exits the nuclear envelope via a nuclear pore, then it attaches to a ribosome on the R.E.R (rough endoplasmic reticulum). the protein is synthesised by the ribosome and is folded in the R.E.R. The R.E.R transports the protein throughout the cell to the Golgi body where the protein is further processed (sugars added) before budding off the Golgi body, it then infuses with the bi-layered plasma membrane by means of exocytosis where it is released into the extracellular environment.


3) Among Proximal convoluted tubule, loop of hanle, distal convoluted tubule, and collecting duct, which one uses the most ATP?
I think this is asking about active transport but I don't know where it happens.
Shoud be Proximal convoluted tubule.

4) gall bladder is unlike stomach, duodenu, jejunum, and colon in that it doesn't contain
a) submucosa
b) muscularis externa
wiki says b is the answer. Released test says A is the answer. Some say both are the answers When nothing seems right-go with the gut!

 

[Hatico]

1) Sodium is least permeable to cell membrane compared to O2, CO2, H2O, and ethanol. Why is Sodium least permeable?

one of my notes says only small and non polar can penetrate membrane.
Sodium is just one Na+ ion whereas CO2, H2O,.... all are compounds so i think they must be bigger than sodium. And I don't know if Na+ is polar or nonpolar.
You already answer - Na+. Charged molecules are always polar.

2) glycoprotein is made in golgi apparatus
isn't all protein made from rough ER?
All proteins are from ER

3) Among Proximal convoluted tubule, loop of hanle, distal convoluted tubule, and collecting duct, which one uses the most ATP?
I think this is asking about active transport but I don't know where it happens.
Polar moleculels are reabsorbed mostly in proximal tubules - Ca+, Na+. Cl-, HCO3-, glucose. All of them requare ATP ( active transport). PCT is my answer ( I'm not sure, just logic)


4) gall bladder is unlike stomach, duodenu, jejunum, and colon in that it doesn't contain
a) submucosa
b) muscularis externa
wiki says b is the answer. Released test says A is the answer. Some say both are the answers

 

[DancingKoala]

Holly J, how am I supposed to know that Sodium ion is larger than H2O, O2, ethanol....etc?
Also, do they provide a periodic table just like they did on DAT?

And here is a question about collagen.

The concentration of which of the following amino acids can be used to determine whether or not dentin has contaminated a purified enamel preparation?

a. lysine
b. proline
c. hydroxyproline
d. phosphotyrosine
e. phosphoserine

The correct answer is hydroxyproline because it's present in Collagen which is present in cementum and dentin but absent in Enamel. However, proline is also present in collagen so why can't it be correct answer? Is this something that I have to go with a gut too

Oh, and also, I know that hydroxylysine is present in collegen but is lysine also present?

 

[Holly J]

Holly J, how am I supposed to know that Sodium ion is larger than H2O, O2, ethanol....etc?
Also, do they provide a periodic table just like they did on DAT?

And here is a question about collagen.

The concentration of which of the following amino acids can be used to determine whether or not dentin has contaminated a purified enamel preparation?

a. lysine
b. proline
c. hydroxyproline
d. phosphotyrosine
e. phosphoserine

The correct answer is hydroxyproline because it's present in Collagen which is present in cementum and dentin but absent in Enamel. However, proline is also present in collagen so why can't it be correct answer? Is this something that I have to go with a gut too

Oh, and also, I know that hydroxylysine is present in collegen but is lysine also present?

Just read...there are like 40 AA in dentin/Enamel....So I guess all the options are actually true to some extent.
Still we choose the best option.
Its asking about the "contaminant"= something that is absent in enamel but present in dentin. Hydroxyproline is not usually seen in Enamel(though Lysine and Glycine are usually there)
p.s: not so sure. I hate these AA topic....because I clearly suck at it! Hoping not to see lots of Qs on my exam!

 

[PooKan]

Hope that works.

thankz Holly...it did..

 

[PooKan]

I guess you mean "horizontal plate" instead "horizontal axis"

no i meant horizontal axis only

 

[PooKan]

1) Action potential initiated along the length of the axon, the ans given s they propagate towards both soma and nerve endings...
but AP travels only in one direction (unilateral) towards nerve endings...how did they come with this ans?

2)each of he following is the mechanism in increasing body temp EXCEPT one
-shivering (ans)
-exothermic reactions
-atp hydrolysis
-peripheral vasodilation
-increased thyroxine release
Shivering causes increased voluntary activity and causes epi release from medulla thus inccreasing BMR....so how does shivering not cause increase body temp?
and exothermic reactions releases heat from body so it must decrease body temp so this must be ans right ...plz help

3)which of the following most likely to result from increased vagal activity
-decreased cardiac oxygen consumption (ans)
-decreased transit time through AV node
why cant second option be the ans?

 

[Hatico]

1) I also was confused, but they are many mistakes in the Decks. Explanation is here:
"AP propagation occurs in one direction because the recently depolarized area of the membrane is in absolute refractory period and cannot generate action potential"

2) An exothermic reaction is a chemical reaction that releases energy . ATP hydrolysis is also exothermic reaction.
Shivering leads to small muscle movement and energy release. Does every energy release increase body temperature?

 

[Holly J]

1) Action potential initiated along the length of the axon, the ans given s they propagate towards both soma and nerve endings...
but AP travels only in one direction (unilateral) towards nerve endings...how did they come with this ans?
From what I remember, yes it is uni-direction. But dendrites receive the signal...pass through the soma then to the axon. So the answer.
2)each of he following is the mechanism in increasing body temp EXCEPT one
-shivering (ans)
-exothermic reactions
-atp hydrolysis
-peripheral vasodilation
-increased thyroxine release
Shivering causes increased voluntary activity and causes epi release from medulla thus inccreasing BMR....so how does shivering not cause increase body temp?
and exothermic reactions releases heat from body so it must decrease body temp so this must be ans right ...plz help

3)which of the following most likely to result from increased vagal activity
-decreased cardiac oxygen consumption (ans)
-decreased transit time through AV node-Vagal stimulation has no direct effect on AV node. It effects only the SA node.
why cant second option be the ans?

 

[DancingKoala]

1) Action potential initiated along the length of the axon, the ans given s they propagate towards both soma and nerve endings...
but AP travels only in one direction (unilateral) towards nerve endings...how did they come with this ans?

2)each of he following is the mechanism in increasing body temp EXCEPT one
-shivering (ans)
-exothermic reactions
-atp hydrolysis
-peripheral vasodilation
-increased thyroxine release
Shivering causes increased voluntary activity and causes epi release from medulla thus inccreasing BMR....so how does shivering not cause increase body temp?
and exothermic reactions releases heat from body so it must decrease body temp so this must be ans right ...plz help

3)which of the following most likely to result from increased vagal activity
-decreased cardiac oxygen consumption (ans)
-decreased transit time through AV node
why cant second option be the ans?

1) I actually don't know how to explain this because I also had the same question. But I just decided to memorize it like this. The only reason it's unilateral is because dendrite --> cell body --> axon --> synapse --> postganglionic cell dendrite....repeat. Dendrite is the place where it recieves the signal. If we tweak something and make the signal recieved in the mid way of axon, I think it can go to both dendrite and axon terminal. But, even if the signal goes from mid way of axon to cell body (which is located at the opposite side of the axon terminal), it won't be able to jump from dendrite to axon terminal. It will just go to cell body and stop (my theory)

2)
I actually agree with you.
According to the old released NBDE (it was asked in two different versions)
"- Shivering = produced by reduction in core temperature
o Temperature regulating mechanisms that increase heat production include shivering, increased voluntary activity, and increased secretion of epinephrine from the adrenal medulla.
"
so you are correct that shivering increases body temperature. Can I ask you where you got this question from because if it's also from old nbde test, then nbde is definitely contradicting to what they said before.

3) I agree with you again.
Right vagus nerve stimulates SA node and Left vagus nerve stimulates AV node.

When are you taking your boards?

 

[ionomer]

Both options seem correct but in the decks it says excessive vagal stimulation can lead to AV nodal block. someone Please clarify im also confused right now.

 

[DancingKoala]

Both options seem correct but in the decks it says excessive vagal stimulation can lead to AV nodal block. someone Please clarify im also confused right now.

I think so, too.
Wikipedia says
Parasympathetic innervation of the heart is controlled by the vagus nerve. To be specific, the vagus nerve acts to lower the heart rate. The right vagus innervates the sinoatrial node. Parasympathetic hyperstimulation predisposes those affected to bradyarrhythmias. The left vagus when hyperstimulated predisposes the heart to atrioventricular (AV) blocks.

What I think is that
Vagus nerve stimulation to nodes = slow them down = less heart pumping = less oxygen needed for heart cardiac muscles
So I think both of them should be right. When it says transit time, is it talking about the time it takes for an impulse to travel from SA node to AV node? or is it talking about the impulse to make the heart beat?

 

[PooKan]

hey...ur true tht vagal stimulation has no effect on AV node....but here its says as TRANSIT time ....and so with increase vagal stimulation there should be Decrease in SA node discharge and so the rate of depolarization through the heart should also decrease i.e., the transit time from SA node to AV node should decrease...

 

[PooKan]

I think so, too.
Wikipedia says
Parasympathetic innervation of the heart is controlled by the vagus nerve. To be specific, the vagus nerve acts to lower the heart rate. The right vagus innervates the sinoatrial node. Parasympathetic hyperstimulation predisposes those affected to bradyarrhythmias. The left vagus when hyperstimulated predisposes the heart to atrioventricular (AV) blocks.

What I think is that
Vagus nerve stimulation to nodes = slow them down = less heart pumping = less oxygen needed for heart cardiac muscles
So I think both of them should be right. When it says transit time, is it talking about the time it takes for an impulse to travel from SA node to AV node? or is it talking about the impulse to make the heart beat?

i think they mean time taken for an impluse to travel from SA node to AV node...

 

[ionomer]

Bone tissue increase in size by which of the following means?

A) Action of osteoclast

B) Mitotic division of osteoclast

C) Appositional growthby osteoblast

D) Interstitial growth by osteoblasts

It says the answer is D but i think its C. Help please

 

[PooKan]

1) I actually don't know how to explain this because I also had the same question. But I just decided to memorize it like this. The only reason it's unilateral is because dendrite --> cell body --> axon --> synapse --> postganglionic cell dendrite....repeat. Dendrite is the place where it recieves the signal. If we tweak something and make the signal recieved in the mid way of axon, I think it can go to both dendrite and axon terminal. But, even if the signal goes from mid way of axon to cell body (which is located at the opposite side of the axon terminal), it won't be able to jump from dendrite to axon terminal. It will just go to cell body and stop (my theory)

2)
I actually agree with you.
According to the old released NBDE (it was asked in two different versions)
"- Shivering = produced by reduction in core temperature
o Temperature regulating mechanisms that increase heat production include shivering, increased voluntary activity, and increased secretion of epinephrine from the adrenal medulla.
"
so you are correct that shivering increases body temperature. Can I ask you where you got this question from because if it's also from old nbde test, then nbde is definitely contradicting to what they said before.

3) I agree with you again.
Right vagus nerve stimulates SA node and Left vagus nerve stimulates AV node.

When are you taking your boards?

hey...i got this question from K series...abt my exams not sure ..thinkin in sept..

 

[DancingKoala]

i think they mean time taken for an impluse to travel from SA node to AV node...

i think vagus nerve starts the signal at SA node but it doesn't care about what happens after that. I think what determines the transmit time between SA node and AV node is atrial filling time because I remember reading that the slight delay of AV node is because it waits until atrial is fully filled with blood.

edit: am i correct that vagus nerve stimulates SA node? Vagus nerve is supposed to inhibit the impulse instead of promoting it, right?

Bone tissue increase in size by which of the following means?

A) Action of osteoclast

B) Mitotic division of osteoclast

C) Appositional growthby osteoblast

D) Interstitial growth by osteoblasts

It says the answer is D but i think its C. Help please

The main difference is that appositional is increase in width whereas interstitial growth is the length. I think both of them can be the answers. Is this from the old released test?

The one I saw says
"§ Long bones of the skeleton increase in length because of the interstitial growth in the cartilagious epiphyseal plate. (not appositional growth)"
So it specifices whether they are looking for the growth in length (or width) in actual test and maybe you don't have to worry about the question you posted unless it's also from a released test.

 

[Hatico]

Bone tissue increase in size by which of the following means?

A) Action of osteoclast

B) Mitotic division of osteoclast

C) Appositional growthby osteoblast

D) Interstitial growth by osteoblasts

It says the answer is D but i think its C. Help please

I also think it's C. Interstitial growth is possible only with chondrocytes (not osteoblast). Correct?

 

[Holly J]

Q. A drug(D) has a pK of 6.4. At pH 7.4, which of the following approximates the ratio of the unprotonated form to the protonated form?
0, 0.1, 1, 10
Somebody care to explain this please?

 

[DancingKoala]

Can someone tell me if there is a way to memorize where we can find root concavities?
For example, which tooth has root concavity on which side on which root...etc?
And here is a sample problem I have.
Buccal and Lingual root concavities can be found in
1) max canine
2) mand canine
3) both canines
4) neither
Besides answer this question, could you also tell me whereelse we can find root concavities so I can make a chart?

 

[Holly J]

Can someone tell me if there is a way to memorize where we can find root concavities?
For example, which tooth has root concavity on which side on which root...etc?
And here is a sample problem I have.
Buccal and Lingual root concavities can be found in
1) max canine
2) mand canine
3) both canines
4) neither
Besides answer this question, could you also tell me whereelse we can find root concavities so I can make a chart?

Neither!
I know its alot confusing!Make our own charts Koala from all the sources.

 

[Hatico]

Q. A drug(D) has a pK of 6.4. At pH 7.4, which of the following approximates the ratio of the unprotonated form to the protonated form?
0, 0.1, 1, 10
Somebody care to explain this please?

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.

 

[DancingKoala]

1) renal compensation for chronic metabolic alkalosis involve a partial reabsorption of the filtered HCO3. (I combined the question with the correct answer and made this sentence )

Metabolic alkalosis happens when HCO3 level goes up and makes pH go up.
To compensate, aren't we supposed to excrete HCO3 instead of reabsorbing more?


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?