just lots of questions

[applicant2002]

Hi! I have been reading my material for class, and I have a few questions that seem to puzzle me.

I read in an a&p book that the T and b cells are not determined directly by antigens, but rather that the antigen affects the expression of certain genes. So my question is, do we have inherent in our genes the immunity to all possible antigens (or at least all the ones we can defend against) are no antigens ?totally? new?

I was reading in Guyton and hall about the crossed extensor reflex, and it was saying (at least in the illustration) that if you put a hot stimulus on one hand, it will flexed, but the other hand will extend?? I understand this for the legs (you would want to extend the other leg for balance), but does this really happen with the hands. All the tiems I can think of with myself, this doesn?t come to mind. Does anyone know what G&H was trying to say, or should I try it on myself

In OMM Class, when trying to explain strain-counterstrain, the instructor gave examples of muscle spindles and golgi tendon. He said that the Golgi tendon acted like the Course chair, while he was like the muscle spindle : the golgi tendon only came into effect if the muscle spindle couldn?t do enough.
But recently, I had to read about muscle spindles and Golgi tendon organs for class, and I read in Guyton and Hall that The muscle spindle is activated when the muscle is extended too much and the Golgi tendon is activated if you contract to fast. So are they controlling factors for the opposite imbalances, and less complementary to each other than they are in opposition.
So whose right? Or am I misinterpreting G&H.

All your responses are greatly appreciated.

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[Dr JPH]

First the T and B cell deal.
Your body has the ABILITY to produce T and B cells that are SPECIFIC for all antigens. This is done through splicing of the genes that encode the heavy and light chains of the MHC. It's called the CLONAL SELECTION THEORY. Your body randomly produces the cells that are specific to SOME antigen. Once an antigen invades, you proilferate more of that particular cell lineage...provided you are lucky enough to have the lineage to fight the bug.

I haven't had physio in quite some time (2 years), but from what I remember the crossed extensor reflex DOES indeed occur in the upper extremities. In the lower extremities it is better understood because the issue of balance is involved.

Again, remembering from physio...the muscle spindle monitors stretch on a bundle of muscle fibers. The Golgi does this well (tap inferior to the patella to stretch the tendon and leg pops forward) but not in the same manner.

The difference? The muscle spindle monitors muscle LENGTH while the Golgi monitors muscle TENSION. The primary action of the Golgi is to prevent muscle damage by sending inhibitory signals once the muscle tension reaches certain point...I don't remember all the details as far as thresholds, motor tracts, etc.

Again, the Golgi are located in the tendon of the muscle, rather than in the actual muscle bundles.


Hope this helps.

 

[applicant2002]

finally i found my thread! i had intended to post this in the osteo forum not the pre osteo, and i guess i messed up.

is there any way I, being, the original poster, can move my own thread?

anyways, thank you for your reply. I will look into the clonal selection theory.

I have a follow up question about the Golgi tendon and muscle spindle. If the golgi tendon controls muscle tension and the muscle spindle controls length--then it would be correct that the spindle increase conduction if your muscle is stretched?

Would golgi tendon would be activated(increase impulses) if it was contracted too much?

If that's the case, do the muscle spindle on the agonist and the Golgi tendon on the antagonist muscle work together in a given action?

thanks