Tuesday, May 05, 2009

Physiology 101

In physiology, medicine, and anatomy, muscle tone (aka residual muscle tension or tonus) is the continuous and passive partial contraction of the muscles. It helps maintain posture, and it declines during REM sleep. It is not to be confused with the concept of toning in physical exercise.
Unconscious nerve impulses maintain the muscles in a partially contracted state. If a sudden pull or stretch occurs, the body responds by automatically increasing the muscle's tension, a reflex which helps guard against danger as well as helping to maintain balance.
The presence of near-continuous innervation makes it clear that tonus describes a "default" or "steady state" condition. There is, for the most part, no actual "rest state" insofar as activation is concerned.
In terms of skeletal muscle, both the extensor and flexor muscles, under normal enervation maintain a constant tone while "at rest" that maintains a normal posture.
Cardiac muscle and smooth muscle, although not directly connected to the skeleton, also have tonus in the sense that although their contractions are not matched with those of antagonist muscles; their non-contractive state is characterized by (sometimes random) enervation.

Physical disorders can result in abnormally low (hypotonia) or high (hypertonia) muscle tone. Another form of hypertonia is Paratonia, which is associated with dementia.

Paratonia or gegenhalten is classified as a form of hypertonia with an involuntary variable resistance (i.e reduced ability of a muscle to stretch) during passive movement (i.e a movement without effort). The disease develops during a period of dementia and the degree of effect is dependent upon the disease's progress. Paratonia was classified very recently by experts, and is unrelated to the much more typical spasticity associated with spastic diplegia and simlilar forms of cerebral palsy.
Clasp-knife response refers to a stretch reflex with a rapid decrease in resistance when attempting to flex a joint, usually during a neurological examination. It is one of the characteristic responses of a upper motor neuron lesion.
It gets its name from the resemblance between the motion of the limb and the sudden closing of a claspknife after sufficient pressure is applied.

Although seemingly a stretch reflex when flexing a joint, force from the muscle during the attempt to flex a joint is actually thought to be caused by the tendon reflex of the antagonistic muscle of that joint, which is an extensor muscle that becomes stretched. In upper motor neuron lesions, muscle tonus may increase and resistance of muscle to stretch increases. However, if sufficient force is applied, limb resistance suddenly decreases.


Limasa Family said...

I totally dig the creepy skull.

a little music said...

The Clasp-knife response - is that the same one exhibited by the catatonic patients in Patch Adams, when he started throwing them a baseball? Or am I way off base?

Jim Cobabe said...

As I recall, the Robin Williams scene with the ball was in ¨Awakenings¨ with all the encephalitis people who were categorized as ¨atypical¨ something-or-others, and he determined them to be similar.

a little music said...

Oh, yes, of course, "Awakenings". Now I remember My brain was short circuitinging much like in the movie.

The beautiful thing about that movie was that they all got better. That tragic thing was that it was short lived. But it does give one hope, doesn't it? There is always hope.

Patricia said...

My experience with these seemingly intractable conditions is that many have solutions. Folks tend to assume that because no solution has been found none exists.

Another problem arises in the quality of the pool of possible therapists. We paid many to try to help our daughter, but only one actually did anything that made a difference. The others made matters worse. Also, their attention spans were woefully short, in important ways, much shorter than my daughter's. After living with this child for 17 years, I understand she moves more slowly through time, but she does move. She was trying; they couldn't see it and some cut her off, saying she wasn't interested in improving. What they meant was that they were not interested in helping her figure out how to understand what her prospects were and then choose.

She still occasionally suffers clonus associated with her cerebral palsey. Her left foot turns in because of a shortening of muscles related to those involuntary contractions. Scholiosis has been another result of the clonus, a hemi-vertabrae in her neck, and deleterious treatment from therapists and one neurologist who really didn't know what she was doing but had a will to impose. We regret deeply following her advice.

But my main point is that experience has shown me that ways exist to resolve the unfortunate neurological, muscular, and skeletal effects of many disordering illnesses, but questions of profit, rather than exploration and charitable intelligence, often guide the professional's consideration.

Jim Cobabe said...


My experience with doctors and medicine parallels your own, judging from your comments. But I must confess, the search for medical help has not been wholly answered by those seeking to profit thereby. At least some were honest enough to confess their limitations. Several doctors directed me elsewhere. All still billed for services, nonetheless. In fact I am still getting statements from doctors whose names I do not recognize. I don't know what they claim to have done for me.

I'd like for one of them to try and describe me, just as a sort of sanity check.

a little music said...

Darrin is very sick.

He lost consciousness tonight, and after he regained consciousness I took him right to the hospital. They did a complete blood panel, and while waiting on that, they hooked him up to all kinds of monitors. His blood pressure was 90/30. He was near to death. When the blood tests came back, they showed that everything possible was messed up. His kidneys, liver, heart, etc., are all doing things they should not. He has mild hepatitis for no known reason, and his kidneys are failing. He is currently in the ICU and is receiving excellent care.

I am scared.

He is my whole world.

Please pray for him.


Patricia said...


I'm so sorry to hear this! My thoughts and prayers will be with you and your family.

Let us know what happens.