There are three types of intrafusal fibers: dynamic bag fibers, static bag fibers, and chain fibers. When muscle lengthens (think about when a muscle is stretched), the intrafusal fibers send signals to the spinal cord through the Group Ia and Group II afferent neurons, which relays information about how much the muscle is lengthening and how fast the muscle is lengthening. The greater the lengthening or speed of lengthening, the more signals will be sent. The gamma motor neurons send signals to the muscle spindles from the CNS (central nervous system) that can increase or decrease the sensitivity of the muscle spindle. The gamma motor neurons help the CNS control the gain of the muscle spindles.
Why are muscle spindles important? There are two big reasons. 1) The muscle spindles send information to the CNS about muscle length, which helps the nervous system know how joint angles are changing and where the different body parts are located in space. For example, if you extend (straighten) your elbow, this lengthens the biceps brachii muscle. The muscle spindles in the biceps will send signals to the CNS, indicating that the muscle is lengthening. If the biceps is lengthening, then the elbow has to be moving into an extended (more straight position). Also, if you were to flex (bend) your knee, this would lengthen the quadriceps, which activate the muscle spindles, indicating that the muscle is lengthening and the knee if flexing. 2) Muscle spindles also help protect the muscle from injury due to the muscle lengthening too much and too fast. If a muscle is lengthening too much and too fast, the CNS can send signals to the muscle for it to contract and shorten.
So, muscle spindles play a crucial role in providing feedback to the CNS about muscle length and speed of lengthening. This information helps the body know how joint angles are changing, and it can serve to help protect the muscle against injury.
I was wondering if you had an opinion on how muscle treatment techniques work via spindle cells and golgi reflex cells.
ReplyDeleteFirst I was wondering if you knew how protective muscles spasms were triggered.
First, lets say that someone stands on one foot for 2 hours and the foot stiffens up.
Second, the patients walk becomes abnormal as they compensate for the abnormal movement in the foot.
Thirdly, the abnormal walk creates abnormal spasm pattern in muscles from the foot to the head.
First, what is the neurologic pathway that creates the spasms?
Second... When a health care provider applies direct pressure to muscles the pressure causes an immediate pain which as time goes by begins to subside until you only fell pressure. It seems to plateau for 10 - 15 seconds then drops 2-4 levels on the Borg pain scale until it becomes just the pressure.
When you go through this painful spasm pattern inch by inch about 10 passes the spasms are no longer there. It is an estimate but its about that amount of time on average.
What do you think is happening to cause this change in the painful muscle spasm?
1. It could be that the pressure is pushing out inflammatory chemicals. Its a logical assumption which could mean that since the inflammation is pushed out that the healthy blood with oxygen and nutrients enters the muscle and lessens the afferent response to the brain of injury.
2. It could be that the spasm causes an increased afferent response with every movement due to the restriction of motion. You move through this and it tubs on tissues or irritates the spindle cells increasing the afferent response that triggers the spasm
3. Does the gamma motor neuron create the muscle spasm contraction?
When you are compressing the intrafusal fibers causing a reduction in the afferent response rate to the brain. If so, compression could be reducing the gamma motor neuron response for contractile spasm.
When muscles are compressed they relax but when there is contraction that compresses the muscle and contraction is desired the gamma motor neuron maintains the tension on the muscle fibers so the contraction can be completed.
Im thinking that the compression of the spindle creates a reduction in the afferent nerve response leading to a reduction in the gamma motor neuron response.
I appreciate your input on this I know a lot of what is required is not known by scientists on this.
Thank you,
Dr James Stoxen DC
Team Doctors
Hi Doc! This image is great and i'm hoping to use it for educational purposes. Do you have the source for it so we can avoid copyright infringement? If so, I would be grateful for it!
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