Lets discuss questions of NBDE 1

[d dimps]

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1). .Which angle does a P Wave makes on ECG?
a). .45 degree
b). .180 degree
c). .0 degree
d). .-45 degree
e). .-180 degree.

2). .What is endogenous cholesterol? Most endogenous cholesterol is converted to?
a). .Glucose
b). .Cholic acid
c). .Steroid
d). .Oxaloacetete
e). .Ketone bodies

3). .Which of the following statement is correct regarding Glioblastoma multiforme?
a). .the tumor is most common before puberty
b). .it is classified as a type of meningioma
c). .it is most common type of Astrocytoma.
d). .Its prognosis is generally more favourablethan Grade 1 astrocytoma.
e). .It is derived from the epithelial lining of ventricles

4). .Which of the following pathological changes is irreversible?
a). .fatty changes in liver cells
b). .karyolysis in myocardial cells
c). .glycogen deposition in hepatocyte nuclei
d). .hydropic vacuolization of renal tubular epithelial cells.

5). .An example of Synergism is the effect of?
a). .insulin and glucagon on blood glucose
b). .estrogen and progesterone on uterine motility
c). .growth hormone and thyroxine on skeletal growth.
d). .Antidiuretic hormone and aldosterone on potassium excretion.

 

[bratdoc]

in the lungs, oxygenation of Hb promotes dissocitation of H+ from Hb, this shifts equilibrium toward CO2 formation; therefore, CO2 is released from RBC's (Haldane effect).

in the peripheral tissue, high H+ from tissue metabolism shifts curve to the right, unloading O2 (bohr effect).

so the answer is

2]movement of HCO3- ions from rbc to plasma

Check out the attached images... and can u please explain a bit more coz i fail to understand how it can be option2

 

[teethie]

pb2007:
i think i will go with HCO3- option if there is no combination mentioned in the choices. but this is solely my gut feling that i will go with. I have no reference to support this single option.

 

[bratdoc]

pb2007:
i think i will go with HCO3- option if there is no combination mentioned in the choices. but this is solely my gut feling that i will go with. I have no reference to support this single option.

teethie u are talking about option 4 right?

 

[teethie]

Yes bratdoc, option 4.

teethie u are talking about option 4 right?

 

[bratdoc]

....

 

[teethie]

dont get confused bratdoc, venous blood here means blood with CO2 going to lungs. finally we are done with this question. thats it.

....

 

[bratdoc]

dont get confused bratdoc, venous blood here means blood with CO2 going to lungs. finally we are done with this question. thats it.

Yes thanks!!! someone's post got me confused!!!

 

[pb2007]

Yes bratdoc, option 4.

thanks guys...
even i was thinkin abt that option only ,so finally we got this rite

 

[deck]

2006 old exam...my exam is coming in less than 2 weeks, could u guys help me solve my Qs?



Plasmid-mediated antibiotic resistance has been observed in diseases caused by each of the following EXCEPT one. Which one is the EXCEPTION?
A) Neisseria gonorrhoeae
B) Streptococcus pyogenes...why??
C) Bordetella pertussis
D) Haemophilus influenzae
E) Staphylococcus aureus

Which of the following represents the location of the lingual height of contour on the crown of the mandibular second premolar?
A) Same third as that tooth's buccal height of contour
B) Same third as the lingual height of contour on the crown of the mandibular first premolar
C) Occlusal third
D) Middle third.....but I thought lingual contour at mand post. teeth are M(1/3), so proximal view can look like rhomboid..😕
E) Same third as the lingual height of contour on the crown of the maxillary premolars

Between which of the following permanent teeth is the lingual embrasure smaller than the facial embrasure?
A) Mandibular first molar and mandibular second molar
B) Maxillary first premolar and maxillary second premolar
C) Mandibular first premolar and mandibular second premolar
D) Maxillary second molar and maxillary third mol...i chose this one

 

[teethie]

please see below:

2006 old exam...my exam is coming in less than 2 weeks, could u guys help me solve my Qs?

Plasmid-mediated antibiotic resistance has been observed in diseases caused by each of the following EXCEPT one. Which one is the EXCEPTION?
A) Neisseria gonorrhoeae
B) Streptococcus pyogenes...why??
C) Bordetella pertussis
D) Haemophilus influenzae
E) Staphylococcus aureus

no idea why???

Which of the following represents the location of the lingual height of contour on the crown of the mandibular second premolar?
A) Same third as that tooth's buccal height of contour
B) Same third as the lingual height of contour on the crown of the mandibular first premolar
C) Occlusal third

D) Middle third.....but I thought lingual contour at mand post. teeth are M(1/3), so proximal view can look like rhomboid..😕
ques is abt location so do not think abt shape.
Middle one third is the answer ref: kaplan

E) Same third as the lingual height of contour on the crown of the maxillary premolars


Between which of the following permanent teeth is the lingual embrasure smaller than the facial embrasure?
A) Mandibular first molar and mandibular second molar
B) Maxillary first premolar and maxillary second premolar
C) Mandibular first premolar and mandibular second premolar-- see next post incorrect because of lingually tilted mand 1 st premolar👍.

D) Maxillary second molar and maxillary third mol...i chose this one

 

[bratdoc]

please see below:

But Teethie kaplan says that all Posteriors have Lingual embrasures greater than the Facial except for maxillary molars@😕

 

[deck]

please see below:

👍👍👍👍👍👍👍👍


Thanks u, teethie!!! I really appreciate it!😍

does that mean u agree the second one ans is mid 1/3??

 

[teethie]

YES DECK, IT IS MIDDLE mid 1/3

👍👍👍👍👍👍👍👍


Thanks u, teethie!!! I really appreciate it!😍

does that mean u agree the second one ans is mid 1/3??

 

[teethie]

I am very sorry deck, I marked this wrong. pl disregard previous answer. correct answer should be choice:
Maxillary second molar and maxillary third molar.

this key is correct as we have a valid resource and reference. i do not know which year your queston is from but sometimes there are erros in keys. so go with the reference only.


reason: bratdoc already mentioned it below. i have confirmed it again from wheelers, due to narrow lingual cusp of mand premolar lingual embrassure is wide not smaller.

bratdoc: thank u for the correction👍

But Teethie kaplan says that all Posteriors have Lingual embrasures greater than the Facial except for maxillary molars@😕

 

[Cindrella]

Decks mention that Second messengers frequently act to stimulate protein kinases , and they r rapidly broken down in cells ( to terminate response ) by enzymes called phosphodiesterases ...

Can someone please elaborate on this and explain . Thank you and sorry but its not entering my hippocampus 😉

 

[Cindrella]

But Teethie kaplan says that all Posteriors have Lingual embrasures greater than the Facial except for maxillary molars@😕

Bratdoc can your please confirm specifically ...
isn't the lingual embrasure smaller between maxillary 1st and 2nd molar
its not maxillary 1st molar and 2nd premolar right 👎

 

[pb2007]

Decks mention that Second messengers frequently act to stimulate protein kinases , and they r rapidly broken down in cells ( to terminate response ) by enzymes called phosphodiesterases ...

Can someone please elaborate on this and explain . Thank you and sorry but its not entering my hippocampus 😉

this is a mechanism of how messages from outside the cell are sent inside .example.....the receptor for epinephrine has a ligand domain outside the cell where epinephrine molecules settles down .attachment of this receptor outside will send signal to inner domain which will activate g protien complex n alpha gtp breaks away frm beta n gamma n will carry signal further to adenyl cyclase ,the moment alpha gtp attaches to adenyl cyclase this will further convert atp to cyclic AMP WHICH acts as 2nd MESSENGER and this 2nd messenger activates the protein kinase A .so in the end its protein kinase that will phosphorylate the target protien which will go to nucleus n tel dna to make a particular mRNA for the required protein sequence .this is one of the many ways how receptors on cell surface works .
once job is over so the 2nd messenger needs to go away so this is wen phosphodiesterase breaks it .caffiene n theophylline inbihits this enzyme so that cell keeps working .
http://www.learnerstv.com/animation/animation.php?ani=183&cat=biology

plz make corrections
http://entochem.tamu.edu/G-Protein/index.html

look at this animation too.dont wana confuse you but the working for protein kinase A is what i tried expaining and the animation shows another way how protein kinase C works .
first link shows how kinase A works n 2nd shows how kinase C works.

 

[Cindrella]

this is a mechanism of how messages from outside the cell are sent inside .example.....the receptor for epinephrine has a ligand domain outside the cell where epinephrine molecules settles down .attachment of this receptor outside will send signal to inner domain which will activate g protien complex n alpha gtp breaks away frm beta n gamma n will carry signal further to adenyl cyclase ,the moment alpha gtp attaches to adenyl cyclase this will further convert atp to cyclic AMP WHICH acts as 2nd MESSENGER and this 2nd messenger activates the protein kinase A .so in the end its protein kinase that will phosphorylate the target protien which will go to nucleus n tel dna to make a particular mRNA for the required protein sequence .this is one of the many ways how receptors on cell surface works .
once job is over so the 2nd messenger needs to go away so this is wen phosphodiesterase breaks it .caffiene n theophylline inbihits this enzyme so that cell keeps working .
http://www.learnerstv.com/animation/animation.php?ani=183&cat=biology

plz make corrections
http://entochem.tamu.edu/G-Protein/index.html

look at this animation too.dont wana confuse you but the working for protein kinase A is what i tried expaining and the animation shows another way how protein kinase C works .
first linbk shows hopw kinase A works n 2nd shows how kinase C works.

Thanks a lott pb2007 .. this is just what i was looking for ... 👍 your explanation says it all.. awesome !!!

 

[bratdoc]

Bratdoc can your please confirm specifically ...
isn't the lingual embrasure smaller between maxillary 1st and 2nd molar
its not maxillary 1st molar and 2nd premolar right 👎

Yes Cindrella the exception to this is Maxillary 1st molar in which the facial embrasure is large than the lingual!

 

[deck]

The proximal contact areas between anterior teeth are incisal to the middle third of the teeth. Which of the following is an EXCEPTION to this rule?
A) The mesial contact of a mandibular lateral incisor😕😕 (Incisal1/3)
B) The mesial contact of a maxillary canine
C) The distal contact of a maxillary canine(mesial1/3)...ans
D) The mesial contact of a maxillary lateral incisor

I think answer should be A or C....what do u guys think?

Which of the following represents the correct size and characteristic of the nerve fibers that conduct sensory input of pain from the oral-facial region?
A) Large diameter, unmyelinated
B) Large diameter, myelinated...why is not A-alfa fiber??😕😕
C) Intermediate diameter,. myelinated
D) Small diameter, myelinated
E) Small diameter, unmyelinated,...ans

Which of the following is the most common location for an atherosclerotic induced aneurysm?
A) Common iliac arteries
B) Thoracic aorta
C) Abdominal aorta...ans
D) Coronary arteries...why is not this one??
E) Arch of the aorta



I finally understand the last question, and it's tricky....maybe some of u guys wants to take a look ^^

Which of the following can result if an individual having reactivation of latent varicella zoster virus transmits virus to a seronegative individual?
A) Herpetic gingivostomatitis
B) Infectious mononucleosis
C) Shingles
D) Herpes labialis
E) Chickenpox..ans...so tricky!!! **

Thank u guys ^^ 😍

 

[bratdoc]

CORRECTIONS IN PURPLE

The proximal contact areas between anterior teeth are incisal to the middle third of the teeth. Which of the following is an EXCEPTION to this rule?
A) The mesial contact of a mandibular lateral incisor😕😕 (Incisal1/3)---NO
B) The mesial contact of a maxillary canine
C) The distal contact of a maxillary canine(mesial1/3)...ans---ANSWER
D) The mesial contact of a maxillary lateral incisor

I think answer should be A or C....what do u guys think?---- Answer is C the correct answer mesial contacts of both the mandibular incisors are incisal---refer Kaplan

Which of the following represents the correct size and characteristic of the nerve fibers that conduct sensory input of pain from the oral-facial region?
A) Large diameter, unmyelinated
B) Large diameter, myelinated...why is not A-alfa fiber??😕😕-NO (NEVER A-alpha fiber here)
C) Intermediate diameter,. myelinated
D) Small diameter, myelinated
E) Small diameter, unmyelinated,...ans----CORRECT ANSWER

Pain conducted in this region is via A-delta and C-fiber only
A-delta=Small diameter, myelinated, FASTER CONDUCTING, SHARP/INSTANT PAIN..just for the initial short duration
C-fiber=Small diameter, unmyelinated, SLOWER CONDUCTING, DULL PAIN, lasts longer... this is the fiber for greater duration....


Which of the following is the most common location for an atherosclerotic induced aneurysm?
A) Common iliac arteries
B) Thoracic aorta
C) Abdominal aorta...ans------ANSWER
D) Coronary arteries...why is not this one??--NO
E) Arch of the aorta

Most frequent site of arteriosclerotic aneurysm is ABDOMINAL AORTA>Coronary artereis... u can check the order of other arteries included also from either Decks or Kaplan.. cant remember which one

I finally understand the last question, and it's tricky....maybe some of u guys wants to take a look ^^

Which of the following can result if an individual having reactivation of latent varicella zoster virus transmits virus to a seronegative individual?
A) Herpetic gingivostomatitis
B) Infectious mononucleosis
C) Shingles
D) Herpes labialis
E) Chickenpox..ans...so tricky!!! **
----Indeed a Good Question!!

Thank u guys ^^ 😍

👍

 

[anniemirza]

[Which of the following represents the correct size and characteristic of the nerve fibers that conduct sensory input of pain from the oral-facial region?
A) Large diameter, unmyelinated
B) Large diameter, myelinated...why is not A-alfa fiber??😕😕-NO (NEVER A-alpha fiber here)
C) Intermediate diameter,. myelinated
D) Small diameter, myelinated
E) Small diameter, unmyelinated,...ans----CORRECT ANSWER

Pain conducted in this region is via A-delta and C-fiber only
A-delta=Small diameter, myelinated, FASTER CONDUCTING, SHARP/INSTANT PAIN..just for the initial short duration
C-fiber=Small diameter, unmyelinated, SLOWER CONDUCTING, DULL PAIN, lasts longer... this is the fiber for greater duration....]

Regarding this can you explain please Bratdoc...lil confused.
And i guess A-DELTA FIBERS ARE LARGE DIAMETER,MYELINATED.
http://en.wikipedia.org/wiki/Nerve_fiber

 

[deck]

CORRECTIONS IN PURPLE


👍

Thanks for the reply, but I used kaplan essential--> It said Man lateral incisal proximal contact is Incisal 1/3 on both mesial and distal

😕The Y shape type of Man 2nd premolar has the same number of occlusal pit as Man 1st molar or Max 1st molar?? Did anyone know? Thank u guys!!!😍

 

[deck]

Here is some dental fact,
1. what groove separate cusp ridge and marginal ridge?
developmental groove

2. What's greatest role on disoccluding post teeth on lateral protrusive?
Ant. guidance

3. The bulk of tooth consist of what? Dentin

4. parotid papilla will appear on vestibule

5.what developmental groove btw df and d cusp of the mad 1st molar? distofacial

6 Max 1st premolar occlude at distal fossa (I thought it was distal marginal ridge before, until I use typodon)

I conclude this by doing old exams,plz correct me if I made mistakes ^^ Good luck everyone!!!!

 

[pb2007]

[Which of the following represents the correct size and characteristic of the nerve fibers that conduct sensory input of pain from the oral-facial region?
A) Large diameter, unmyelinated
B) Large diameter, myelinated...why is not A-alfa fiber??😕😕-NO (NEVER A-alpha fiber here)
C) Intermediate diameter,. myelinated
D) Small diameter, myelinated
E) Small diameter, unmyelinated,...ans----CORRECT ANSWER

Pain conducted in this region is via A-delta and C-fiber only
A-delta=Small diameter, myelinated, FASTER CONDUCTING, SHARP/INSTANT PAIN..just for the initial short duration
C-fiber=Small diameter, unmyelinated, SLOWER CONDUCTING, DULL PAIN, lasts longer... this is the fiber for greater duration....]

Regarding this can you explain please Bratdoc...lil confused.
And i guess A-DELTA FIBERS ARE LARGE DIAMETER,MYELINATED.
http://en.wikipedia.org/wiki/Nerve_fiber

jst want to share this piece of info i found in 'monheim's local anesthesia and pain control in dental practice' .
a delta fibres r large myelinated n conduct fast impluse .they r confined to the pregang autonomic fibres .no such fibres found in dorsal roots ,therefore they hav no afferent function .so we are left with c fibres which r slow conducting small unmyelinated

resting potential of nerve memb is maintained by
1]osmoreceptors
2]gibbs donan equilibrium
3]electrical and chemical gradients
4]active transport of sodium n potassium ions .....answer
5]memb permeabilityto potassium ions

for the above ques the answer in the key is 4th choice but why isnt it 5th choice.RMP is dependent on potassium channels .can anyone explain why 4th is correct choice .

 

[anniemirza]

resting potential of nerve memb is maintained by
1]osmoreceptors
2]gibbs donan equilibrium
3]electrical and chemical gradients
4]active transport of sodium n potassium ions .....answer
5]memb permeabilityto potassium ions

for the above ques the answer in the key is 4th choice but why isnt it 5th choice.RMP is dependent on potassium channels .can anyone explain why 4th is correct choice .[/QUOTE]

Hey pb2007...thanx for the explanation above.
Regarding ur question,we had a similar discussion on the last page but anyways iam posting the link here for potassium transport which is not due to membrane permeability but rather active transport which occurs due to sodium -potassium pump using ATP.
link:http://www.biologymad.com/NervousSystem/nerveimpulses.htm

 

[pb2007]

resting potential of nerve memb is maintained by
1]osmoreceptors
2]gibbs donan equilibrium
3]electrical and chemical gradients
4]active transport of sodium n potassium ions .....answer
5]memb permeabilityto potassium ions

for the above ques the answer in the key is 4th choice but why isnt it 5th choice.RMP is dependent on potassium channels .can anyone explain why 4th is correct choice .

Hey pb2007...thanx for the explanation above.
Regarding ur question,we had a similar discussion on the last page but anyways iam posting the link here for potassium transport which is not due to membrane permeability but rather active transport which occurs due to sodium -potassium pump using ATP.
link:http://www.biologymad.com/NervousSystem/nerveimpulses.htm[/QUOTE]
thnks anniemirza.

 

[wdent]

Thanks for the website pb2007 ...

Was lookin in NBDE ist aid page 307 ,,

In Restin Memb poterntial :
* A charge seperation occurs : K LEAK , + charge leave the cell down electromechemical gradiest
and that IT IS MOST IMPORTANT DETERMINANT OF RMP

My Quest. why POTASSIUM (k) Leak is the most determinant of Restin memb. potentail

Pls can someone clear this doubts what do they mean by this !!!! its in nbde ist aid page 307

Thanks

 

[anniemirza]

In Restin Memb poterntial :
* A charge seperation occurs : K LEAK , + charge leave the cell down electromechemical gradiest
and that IT IS MOST IMPORTANT DETERMINANT OF RMP

My Quest. why POTASSIUM (k) Leak is the most determinant of Restin memb. potentail

Pls can someone clear this doubts what do they mean by this !!!! its in nbde ist aid page 307

Thanks

[/QUOTE]
Hey wdent....this mite help u here:
The combination of the Na+K+ATPase pump and the leak channels cause a stable imbalance of Na+ and K+ ions across the membrane. This imbalance of ions causes a potential difference (or voltage) between the inside of the neurone and its surroundings, called the resting membrane potential.

 

[pb2007]

Thanks for the website pb2007 ...

Was lookin in NBDE ist aid page 307 ,,

In Restin Memb poterntial :
* A charge seperation occurs : K LEAK , + charge leave the cell down electromechemical gradiest
and that IT IS MOST IMPORTANT DETERMINANT OF RMP

My Quest. why POTASSIUM (k) Leak is the most determinant of Restin memb. potentail

Pls can someone clear this doubts what do they mean by this !!!! its in nbde ist aid page 307

Thanks
this is what is thought initially but the link mentions different thing so as annie said its n/k pump that dominantly determines .

 

[bratdoc]

HI Guys please refer to Kaplan Review notes first page of the chapter on Nervous System Physiology
It says that "Resting memebrane potential is because of the differential distribution of ions and the selective permeability of the cell membrane. The resting membrane potential is formed largely because the neuron is permeable to K ions and impermeable to intracellular anions. K flows down the electrochemical gradient leaving a net negative charge inside......."
In the column next to it Kaplan again meintions under the heading "NOTE: Vr(RESTING MEMBRANE POTENTIAL) is largely determined by K because the cell membrane is much more permeable to K than to other ions"
Hope this helps!!!
coz Na-K Pump maintains the concentration gradient of the ions NOT the electrical gradient!

 

[anniemirza]

jst want to share this piece of info i found in 'monheim's local anesthesia and pain control in dental practice' .
a delta fibres r large myelinated n conduct fast impluse .they r confined to the pregang autonomic fibres .no such fibres found in dorsal roots ,therefore they hav no afferent function .so we are left with c fibres which r slow conducting small unmyelinated

@pb2007 and (also Bratdoc)....You stated that A-delta fibres do not have affrent function....but luk at dis:
A DELTA fiber is an extension of a pseudounipolar neuron with its cell body located in a dorsal root ganglion.These nerve fibers are associated with acute (sharp) pain and therefore constitute the afferent portion of the reflex arc that results in "pulling away" from noxious stimuli.😕😕😕

 

[wdent]

Thanks guys for ur explanations !

 

[bratdoc]

@pb2007 and (also Bratdoc)....You stated that A-delta fibres do not have affrent function....but luk at dis:
A DELTA fiber is an extension of a pseudounipolar neuron with its cell body located in a dorsal root ganglion.These nerve fibers are associated with acute (sharp) pain and therefore constitute the afferent portion of the reflex arc that results in "pulling away" from noxious stimuli.😕😕😕

@Anniemirza
I never said they dont have afferent function!!👍

 

[pb2007]

jst want to share this piece of info i found in 'monheim's local anesthesia and pain control in dental practice' .
a delta fibres r large myelinated n conduct fast impluse .they r confined to the pregang autonomic fibres .no such fibres found in dorsal roots ,therefore they hav no afferent function .so we are left with c fibres which r slow conducting small unmyelinated

resting potential of nerve memb is maintained by
1]osmoreceptors
2]gibbs donan equilibrium
3]electrical and chemical gradients
4]active transport of sodium n potassium ions .....answer
5]memb permeabilityto potassium ions

for the above ques the answer in the key is 4th choice but why isnt it 5th choice.RMP is dependent on potassium channels .can anyone explain why 4th is correct choice .

bratdoc can u explain this ques ,i'm badly confused now .

 

[anniemirza]

@Anniemirza
I never said they dont have afferent function!!👍

Bratdoc....it ws stated by pb2007...I put you in the brackets becoz it was ur post initially so I wanted you to 2clarify too.Dats it.

 

[pb2007]

Bratdoc....it ws stated by pb2007...I put you in the brackets becoz it was ur post initially so I wanted you to 2clarify too.Dats it.

,kaplan does mention a delta fibres association with dorsal root ,then may be that buk mentions it wrongly.sorry for all this confusion.

 

[bratdoc]

bratdoc can u explain this ques ,i'm badly confused now .

According to Kaplan i will go with 5) Membrane permeability of sodium ions

Because i think the Na-K pump just helps to create a concentration gradient but the actual RMP is created by the selective permeability to the K ions


According to wiki
http://en.wikipedia.org/wiki/Resting_potential
Any voltage is a difference in electric potential between two points - for example, the separation of positive and negative electric charges on opposite sides of a resistive barrier. The typical resting membrane potential of a cell arises from the separation of potassium ions from intracellular, relatively immobile anions across the membrane of the cell. Because the membrane permeability for potassium is much higher than that for other ions (disregarding voltage-gated channels at this stage), and because of the strong chemical gradient for potassium, potassium ions flow from the cytosol into the extracellular space carrying out positive charge, until their movement is balanced by build-up of negative charge on the inner surface of the membrane. Again, because of the high relative permeability for potassium, the resulting membrane potential is almost always close to the potassium reversal potential. But in order for this process to occur, a concentration gradient of potassium ions must first be set up. This work is done by the ion pumps/transporters and/or exchangers and generally is powered by ATP.

Another wiki link says
http://en.wikipedia.org/wiki/Na+/K+-ATPase#Resting_potential
In order to maintain the cell membrane potential, cells must keep a low concentration of sodium ions and high levels of potassium ions within the cell (intracellular)[citation needed]. After the formation of an action potential, when the cell is repolarizing (that is, the interior of the cell is becoming more and more negative as K+ ions flood out), there is a stage wherein the membrane potential undershoots its resting membrane potential, as K+ channels take too long to close[citation needed]. This is called hyperpolarization[citation needed]. This process changes only 1 in 100,000,000,000 of bulk concentration; however, over time, there would be run-down of the ionic gradients. The sodium-potassium pump moves 3 sodium ions out by hydrolysing ATP and allows 2 potassium ions in through active transport[citation needed]. The pump undergoes a conformational change in order to do this. However this does not contribute to the restoration of the resting membrane potential in any way, which is mainly accomplished by potassium leak channels that are always active.

 

[anniemirza]

From the pain receptors, pain impulses
are carried to the CNS by two fiber systems:
the large myelinated fibres (A-delta) conduct
impulses rapidly (15.25 m/sec), the small
unmyelinated fibres (C-fibres) conduct at a
slower rate (<1 m/sec).It is known that noxious
stimulation exciting somatic and dental A&#948;​

afferents may exert a masking or inhibitory​

effect on C-fiber related sensations.

 

[bratdoc]

Bratdoc....it ws stated by pb2007...I put you in the brackets becoz it was ur post initially so I wanted you to 2clarify too.Dats it.

No Problem!!👍👍 As long as we get to understand our answers, that is what matters most!!!!
Hmm and thank you for mentioning the size of the a delta fibers.. they are larger when compared to the C-fibers, but are nonetheless small otherwise... i mean that is what i read! might be wrong!🙂

 

[anniemirza]

[Which of the following represents the correct size and characteristic of the nerve fibers that conduct sensory input of pain from the oral-facial region?
A) Large diameter, unmyelinated
B) Large diameter, myelinated...ANSWER!!
C) Intermediate diameter,. myelinated
D) Small diameter, myelinated
E) Small diameter, unmyelinated,..


Now finally i guess this is the right choice!!!Phewwww!

 

[pb2007]

According to Kaplan i will go with 5) Membrane permeability of sodium ions

Because i think the Na-K pump just helps to create a concentration gradient but the actual RMP is created by the selective permeability to the K ions


According to wiki
http://en.wikipedia.org/wiki/Resting_potential
Any voltage is a difference in electric potential between two points - for example, the separation of positive and negative electric charges on opposite sides of a resistive barrier. The typical resting membrane potential of a cell arises from the separation of potassium ions from intracellular, relatively immobile anions across the membrane of the cell. Because the membrane permeability for potassium is much higher than that for other ions (disregarding voltage-gated channels at this stage), and because of the strong chemical gradient for potassium, potassium ions flow from the cytosol into the extracellular space carrying out positive charge, until their movement is balanced by build-up of negative charge on the inner surface of the membrane. Again, because of the high relative permeability for potassium, the resulting membrane potential is almost always close to the potassium reversal potential. But in order for this process to occur, a concentration gradient of potassium ions must first be set up. This work is done by the ion pumps/transporters and/or exchangers and generally is powered by ATP.

Another wiki link says
http://en.wikipedia.org/wiki/Na+/K+-ATPase#Resting_potential
In order to maintain the cell membrane potential, cells must keep a low concentration of sodium ions and high levels of potassium ions within the cell (intracellular)[citation needed]. After the formation of an action potential, when the cell is repolarizing (that is, the interior of the cell is becoming more and more negative as K+ ions flood out), there is a stage wherein the membrane potential undershoots its resting membrane potential, as K+ channels take too long to close[citation needed]. This is called hyperpolarization[citation needed]. This process changes only 1 in 100,000,000,000 of bulk concentration; however, over time, there would be run-down of the ionic gradients. The sodium-potassium pump moves 3 sodium ions out by hydrolysing ATP and allows 2 potassium ions in through active transport[citation needed]. The pump undergoes a conformational change in order to do this. However this does not contribute to the restoration of the resting membrane potential in any way, which is mainly accomplished by potassium leak channels that are always active.

thnkuuu so much bratdoc,finally i got it rite now.wikipedia mentions it clearly primarily its na/k pump only .

[Again, because of the high relative permeability for potassium, the resulting membrane potential is almost always close to the potassium reversal potential. But in order for this process to occur, a concentration gradient of potassium ions must first be set up. This work is done by the ion pumps/transporters and/or exchangers and generally is powered by ATP.]

 

[anniemirza]

No Problem!!👍👍 As long as we get to understand our answers, that is what matters most!!!!
Hmm and thank you for mentioning the size of the a delta fibers.. they are larger when compared to the C-fibers, but are nonetheless small otherwise... i mean that is what i read! might be wrong!🙂

Hey bratdoc...its the same thing...They are just considered larger wen they are compared to the c-fibers.

 

[bratdoc]

thnkuuu so much bratdoc,finally i got it rite now.wikipedia mentions it clearly primarily its na/k pump only .

[Again, because of the high relative permeability for potassium, the resulting membrane potential is almost always close to the potassium reversal potential. But in order for this process to occur, a concentration gradient of potassium ions must first be set up. This work is done by the ion pumps/transporters and/or exchangers and generally is powered by ATP.]

👍good that you got it... but i didnt exactly understand how does the NA-K pump maintain RMP..... according to the info the Na-K pump just maintains the CONCENTRATION GRADIENT...... BUT the RMP is CAUSED due to the SELECTIVE PERMEABILITY of the Membrane to the K ions!! that is what is written in Kaplan also! can u explain how?

 

[anniemirza]

What is collateral circulation in pulp???😕

 

[teethie]

Hi guys,

pb 2007: the reference you mentioned from Monheims was not wrong , you only missed seeing a bracket there which meant that only B fibres do not have afferent function, it was not written for A delta fibres.
that book is not wrong.

A delta: large diameter , myelinated, due to large diameter, pain is sharp.
C fibres: small diameter, unmyelinated

Reference: check in anatomy decks#208, monheims local anesthesia, Grossman endodontics. I am confident that if you refer any other book, this information will be same.


Which of the following represents the correct size and characteristic of the nerve fibers that conduct sensory input of pain from the oral-facial region?
A) Large diameter, unmyelinated
B) Large diameter, myelinated--- correct answer. it is A-Delta fibres.
C) Intermediate diameter,. myelinated
D) Small diameter, myelinated
E) Small diameter, unmyelinated

 

[pb2007]

👍good that you got it... but i didnt exactly understand how does the NA-K pump maintain RMP..... according to the info the Na-K pump just maintains the CONCENTRATION GRADIENT...... BUT the RMP is CAUSED due to the SELECTIVE PERMEABILITY of the Membrane to the K ions!! that is what is written in Kaplan also! can u explain how?

we know that n/k pumps 3 na out n 2 k inside so basically our cells become a bag of potassium .now to achieve the RMP k+starts to leak out n cells keeps becomin electro negative until a point comes wen we achieve the RMP. SO WAT WIKIPEDIA says is that for this potassium leak to happens it was n/k pump that worked intially .so ultimately the thing that is setting the stage for k leak is the atpase pump .
sorry ,this explanation is too stupid but i dont kno how to say my thing in better words .jst concentrate on lines i put in brakets frm wiki .

this what i thing goes for that ques but plz correct if i messed up .

thnks teethie i didnt pay attention while reading n missed that part

 

[teethie]

I think there is no collateral circulation in dental pulp.

What is collateral circulation in pulp???😕

 

[bratdoc]

👍good that you got it... but i didnt exactly understand how does the NA-K pump maintain RMP..... according to the info the Na-K pump just maintains the CONCENTRATION GRADIENT...... BUT the RMP is CAUSED due to the SELECTIVE PERMEABILITY of the Membrane to the K ions!! that is what is written in Kaplan also! can u explain how?

we know that n/k pumps 3 na out n 2 k inside so basically our cells become a bag of potassium .now to achieve the RMP k+starts to leak out n cells keeps becomin electro negative until a point comes wen we achieve the RMP. SO WAT WIKIPEDIA says is that for this potassium leak to happens it was n/k pump that worked intially .so ultimately the thing that is setting the stage for k leak is the atpase pump .
sorry ,this explanation is too stupid but i dont kno how to say my thing in better words .jst concentrate on lines i put in brakets frm wiki .

Thank you pb2007 ... i understand it now... since the question asked "RMP is maintained by" that is why it should be NA-K pump.... if the question was "RMP is caused by" then it should have been permeability of K ions!! Super👍

 

[anniemirza]

I think there is no collateral circulation in dental pulp.

Yea thats what I thought initially...but the decks say "Young pulp lacks collateral circulation"...so that means mature pulp contain collateral circulation which is not seen in the young pulp.Somebody clarify😕 please.