doubts in bio-physio section of asda papers

[R19]

PLS explain ans to these qs...
1.Subliminal fringe of motor neuron pool is useful concept in explaining the phenomena of
A.direct inhibition
B.reciprocal innervation
C.CENTRAL FACILITATION (ans)
D.monosynaptic conduction

2.Diffusion coefficient for transfer of each gas through respiratory membrane depend upon-
a.solubility
b.molecular weight
c.both solubility and molecular weight (ans???)
d.concentration gradient
e.membrane pore size

3.substance that alters the rate of an enzymatic reaction by interacting with enzyme at a site other than active site-
a.an allosteric modifier
b.competetive inhibitor
c.non competative inhibitor
d.none (given ans is 'a' why not 'c'??)

4.which are cariostatic minerals?
a.fluoride and phosphate
b.fluoride and selenium
c.copper and phosphate
d.Selenium and Cu
d.Fluoride and lead (i think ans should b 'a'...m i rite??)

5.GFR may be measured by
A. creatinine
B.substance which is filtered and secreted
C.substance fileterd but not reabsorbed or secreted (this is the marked ans but A can also be the ans??)

6.absorption of Ca in small intestine can be increased by
a.ingestion of fat
b.high phosphate diet
c.administration of vit a
d.lower ph of intestine (ans)
e.adm of parathyroid hormone (shouldn't this be the ans??how does low ph work??)

7.which is not a method of regulating enzyme activity?
a.allosterism
b.zymogen activation
c.competitive inhibitor
d.induction and repression (this is marked as correct ans but in kaplan review notes induction and repression is listed among methods to regulate enzyme activity...which is rite??)

8.what is reflex after discharge and internuncial pool circuits??

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[ibeflossin]

PLS explain ans to these qs...
1.Subliminal fringe of motor neuron pool is useful concept in explaining the phenomena of
A.direct inhibition
B.reciprocal innervation
C.CENTRAL FACILITATION (ans)
D.monosynaptic conduction

2.Diffusion coefficient for transfer of each gas through respiratory membrane depend upon-
a.solubility
b.molecular weight
c.both solubility and molecular weight (ans???)
d.concentration gradient
e.membrane pore size

3.substance that alters the rate of an enzymatic reaction by interacting with enzyme at a site other than active site-
a.an allosteric modifier
b.competetive inhibitor
c.non competative inhibitor
d.none (given ans is 'a' why not 'c'??)

allosteric MODIFIER is not the same as an allosteric inhibitor, which is probably why you are wondering why a non-competitive inhibitor is not a correct answer choice. the question also says "interacting with the enzyme" not the binding site... therefore it is not an inhibitor, but a modifier.

4.which are cariostatic minerals?
a.fluoride and phosphate
b.fluoride and selenium
c.copper and phosphate
d.Selenium and Cu
d.Fluoride and lead (i think ans should b 'a'...m i rite??)

actually fluoride, lead, and silver are all cariostatic materials. this is why you see less recurrent decay with amalgam than with composite. phosphate is not cariostatic.

5.GFR may be measured by
A. creatinine
B.substance which is filtered and secreted
C.substance fileterd but not reabsorbed or secreted (this is the marked ans but A can also be the ans??)

creatinine is measured clinically, however it reabsorbed or secreted... but usually in very very minute amounts. but in this case the "best answer" is C.

6.absorption of Ca in small intestine can be increased by
a.ingestion of fat
b.high phosphate diet
c.administration of vit a
d.lower ph of intestine (ans)
e.adm of parathyroid hormone (shouldn't this be the ans??how does low ph work??)

7.which is not a method of regulating enzyme activity?
a.allosterism
b.zymogen activation
c.competitive inhibitor
d.induction and repression (this is marked as correct ans but in kaplan review notes induction and repression is listed among methods to regulate enzyme activity...which is rite??)

"choose the best answer" here. technically induction & repression may regulate enzyme activity, but the other 3 options DEFINITELY regulate enzyme activity. stay away from using kaplan as a reference. too many times have people used their excessive details and got very basic concepts wrong.

8.what is reflex after discharge and internuncial pool circuits??

good luck!

 

[R19]

thnx ibeflossin.one more doubt what exactly is diff. between muscle tonus and tension?there's a qn about which sensory organ is concernd with maintenance of muscle tonus and muscle spindle is the ans. instead of golgi tendon organ.

 

[ibeflossin]

thnx ibeflossin.one more doubt what exactly is diff. between muscle tonus and tension?there's a qn about which sensory organ is concernd with maintenance of muscle tonus and muscle spindle is the ans. instead of golgi tendon organ.

in short:
muscle spindles sense muscle length.
golgi tendon organs sense muscle tension.
the answer is muscle spindle b/c the question asks about SENSORY ORGAN.

muscle spindles are small muscle fibers innervated by GAMMA motor neurons & a stretch-sensitive AFFERENT neuron. when a muscle is stretched, there is a deformation of the muscle spindle, which causes the primary endings to synapse. this is thought of as a stretch reflex (like the knee-jerk reflex).

golgi tendon organ is thought of as a receptor in series with some skeletal muscle fibers. these are innervated by ALPHA motor neurons. so when the muscle contracts, there is a tendon that the muscle inserts in, which will lengthen & stretch the nerve endings of the afferent fibers, resulting in them firing. this is thought of like a "reverse stretch reflex" in order to protect against damage that can occur w/ excessive stretching of a muscle. what happens is muscle stretch causes an increased rate of firing from the spindle afferents resulting an increased firing of alpha motor neurons to cause muscle contraction.

try not to think of them as separate. they actually work together. so when a muscle is stretched, both of the afferents will fire. so the stretched muscle will contract, then the tendon organ will increase the discharge, & the muscle spindle will decrease the rate of discharge. input into the CNS through the gamma motor neurons can actually regulate muscle tone (or as you put it muscle tension) which can regulate contraction as well.

i am sorry if i confused you more. but from what i remember from the exam, you don't need to worry about this too much.

 

[Cindrella]

Thanks a lot Ibeflossin and R19... i had similar doubts with the same question
Can you please tell me something about Zymogen activation in Enzyme regulation ? thank you

 

[Cindrella]

Proteins serve as each of the following EXCEPT

A-hormones.
B-catalysts --> My answer
C-oxygen carriers.
D-structural elements.
E-carriers of genetic information -- ASDA's answer

pls explain

 

[Svetlana]

Proteins serve as each of the following EXCEPT

A-hormones.
B-catalysts --> My answer
C-oxygen carriers.
D-structural elements.
E-carriers of genetic information -- ASDA's answer

pls explain

Well,i suppose
carriers of genetic inf. are NUCLEIC ACID(not amino acid-->not protein)-DNA,RNA
catalysts are enzymes for ex.(which are PROTEINS)

 

[Cindrella]

Well,i suppose
carriers of genetic inf. are NUCLEIC ACID(not amino acid-->not protein)-DNA,RNA
catalysts are enzymes for ex.(which are PROTEINS)

Thanks ... Can u tell me a little about Zymogen activation... does it exist ?!

 

[Cindrella]

The mechanism of fluoride action in reducing dental decay is most likely the result of

1-an increase in remineralization of enamel.
2-a reduction of solubility of enamel as fluoride content increases.
3-an influence on exchange of ions between body fluids and hard tissues.
4-a decrease in carbohydrate metabolism in the oral cavity as a result of a bacteriostatic effect.

ASDA's answer --> sometimes they say 2 and sometimes 4 ... which one should we mark ???!

 

[bratdoc]

Thanks ... Can u tell me a little about Zymogen activation... does it exist ?!

Yes Zymogens are enzyme precursor forms. Many enzymes are secreted as precursors to avoid digestion of the cells they are secreted from. These enzymes are then converted from precursor(zymogen) form to the active enzymes. Here are a few examples
-Trypsinogen is a zymogen(inactive). It is acted upon by Enteropeptidase to be converted into Trypsin(active) form
-Angiotensinogen(Zymogen/Inactive)------Angiotensin(Active)
-Prothrombin(Zymogen/Inactive)------ Thrombin(active)

Similarly there are many enzymes in the digestive system(pancreatic enzymes) and in the coagulation system which are secreted as zymogens needing activation for their action... Hope this helps!

 

[teethie]

I will go with 2 because o f fluoroapatitie is most resistant to dissolutin than enamel. hence the answer.

The mechanism of fluoride action in reducing dental decay is most likely the result of

1-an increase in remineralization of enamel.
2-a reduction of solubility of enamel as fluoride content increases.
3-an influence on exchange of ions between body fluids and hard tissues.
4-a decrease in carbohydrate metabolism in the oral cavity as a result of a bacteriostatic effect.

ASDA's answer --> sometimes they say 2 and sometimes 4 ... which one should we mark ???!

 

[bratdoc]

I will go with 2 because o f fluoroapatitie is most resistant to dissolutin than enamel. hence the answer.

Agree 100% because fluoride displaces hydroxy in hydroxyapatite to form Fluoroapatite which is less soluble, making the enamel less soluble.
Also some other functions of fluoride also include increased remineraliztion of enamel!

 

[R19]

in short:
muscle spindles sense muscle length.
golgi tendon organs sense muscle tension.
the answer is muscle spindle b/c the question asks about SENSORY ORGAN.

muscle spindles are small muscle fibers innervated by GAMMA motor neurons & a stretch-sensitive AFFERENT neuron. when a muscle is stretched, there is a deformation of the muscle spindle, which causes the primary endings to synapse. this is thought of as a stretch reflex (like the knee-jerk reflex).

golgi tendon organ is thought of as a receptor in series with some skeletal muscle fibers. these are innervated by ALPHA motor neurons. so when the muscle contracts, there is a tendon that the muscle inserts in, which will lengthen & stretch the nerve endings of the afferent fibers, resulting in them firing. this is thought of like a "reverse stretch reflex" in order to protect against damage that can occur w/ excessive stretching of a muscle. what happens is muscle stretch causes an increased rate of firing from the spindle afferents resulting an increased firing of alpha motor neurons to cause muscle contraction.

try not to think of them as separate. they actually work together. so when a muscle is stretched, both of the afferents will fire. so the stretched muscle will contract, then the tendon organ will increase the discharge, & the muscle spindle will decrease the rate of discharge. input into the CNS through the gamma motor neurons can actually regulate muscle tone (or as you put it muscle tension) which can regulate contraction as well.

i am sorry if i confused you more. but from what i remember from the exam, you don't need to worry about this too much.

ibeflossin ur rite both work 2gether so i guess v choose d ans based on which one has a predominating role.although im not sure about only muscle spindle being a sensory organ,they both r sensory organs.

 

[butterfly22]

good luck!

hi Ibeflossin...can u plz explain what is subliminal fringe..neva hear of it

 

[Cindrella]

Thanks a lot bratdoc and teethie ..

 

[billys]

Acetlycholine is released in at all of the following junctions except

1.Sympathetic ganglia
2.Parasympathetic ganglia
3.Somatic efferents to skeletal muscles
4.terminal sympathetic fibers to the heart
5.terminal sympathetic fibers to the adrenal medulla

ans is 4.

can anyone explain please.