Features of red and white muscles

Red (slow) muscle	Pale (fast) muscle
1. Myoglobin content is more.	Myoglobin content is less
2. Sarcoplasmic reticulum is less extensive	Sarcoplasmic reticulum is more extensive
3. Blood vessels are more extensive	Blood vessels are less extensive
4. Mitochondria are more in number	Mitochondria are less in number
5. Response is slow with long latent period   period	Response is rapid with short latent period
6. Contraction is less powerful	Contraction is more powerful
7. This muscle is involved in prolonged and continued activity	This muscle is not involved in prolonged and continued activity
8. Fatigue occurs slowly	Fatigue occurs quickly
9. Depends on cellular respiration for ATP production	Depends on glycolysis for ATP production

 

TETANIC OR SUMMARIZED CONTRACTION

In reply to a rhythmic irritation (namely the such one our muscles are received) the muscle is reduced lengthly (for a long time). Such a contraction has received the name tetanic or summarized. If each subsequent stimulus approaches to a muscle in the period, when it began to be relaxed, there is an infused, dentate or incomplete tetanus. Impulsations rate is 30 in 1 min. It can be expressed under experimental conditions. Fits also are dentate tetanus example. So, it is not physiological. It requires much energy.

If the interval between irritations decreases so, that each subsequent stimulus comes to a muscle at that moment when it is in a contraction phase, there is a smooth or complete tetanus. Impulsations frequency is 60 in 1 min. Smooth tetanus is more physiologic. It requires less energy for its performance. Neck movements to the both sides can be example of such tetanus.

MUSCLE TONE DEFINITION

Muscle fibers always maintain a state of slight contraction with certain degree of vigor and tension. This property of muscle is called tone or tonus.

All skeletal muscles show little tonus. But antigravity muscles like extensors of lower limb, trunk muscles and neck muscles show tonus to a greater extent.

MAINTENANCE OF MUSCLE TONE

In Skeletal Muscle

Maintenance of tone in skeletal muscle is neurogenic. It is due to continuous discharge of impulses from gamma motor neurons in anterior grey horn of spinal cord. Gamma motor neurons in spinal cord are controlled by higher centers in brain.

ABNORMALITIES OF MUSCLE TONE

The abnormalities of muscle tone are:

1. Hypertonic State

When tone is increased, the muscle becomes spastic (rigid or stiff). This condition of the muscle is called spasticity. Upper motor neuron lesion causes spastic paralysis of muscles, because during upper motor neuron lesion, inhibition of lower motor neuron is lost. So, there is exaggeration of activity of lower motor neuron causing increased muscle tone.

2. Hypotonic State

If muscle tone is decreased or lost, the muscle becomes flaccid and the condition is called flaccidity. Lower motor neuron lesion causes flaccid paralysis of muscles. The muscles undergo wasting.

3. Myotonia

This is an inherited disease characterized by continuous contraction of muscle even after the cessation of voluntary act. The power of relaxation is decreased. Myotonia is due to some abnormal gene that affects the ionic channels in sarcolemma.

Tongue, lips muscles and masticatory muscles contractive types and regimes at conversation.

During mastication mandible displacement takes place due to masticatory muscles contractions occurring in tetanic regimen (mainly incomplete). Contraction type – auxotonic (accompanied by muscle length and tension changings). Lips participate in sounds formation; one can see isometric, isotonic and auxotonic (or auxometric) contractions. Regimen – tetanus.