When a greater number of motor units are present in a muscle and are able to be simultaneously stimulated causing an increase in muscle force (Sherwood, and Kell 271-272).
True
In skeletal muscle contraction, summation means increasing the number of stimuli that is delivered to a given motor unit per time. This increases the Calcium concentration, which causes more tension and shortening of the muscles.
Wave summation releases more calcium and increases the force of contraction by increasing the firing rate of motor neurons (The second contraction takes place before the first is completely at rest) so each stimulation adds up. This is all within ONE MUSCLE FIBER. Recruitment is the calling up multiple MOTOR UNITS, in order to increase the force of contraction. t has a size principle (those with small diameters, the more delicate ones are called first, then the larger and so on.) There is no added calcium ions as in wave summation. They usually occur together. wave summation can cause tetanus, while recruitment cannot.
Asynchronous recruitment of motor units is used to prevent fatigue. While some motor units are active others are inactive. This pattern of firing of motor neurons prevents fatigue while maintaining contraction by allowing a brief rest for the inactive units.
Muscle recruitment
recruitment
There is no 'multi motor unit' to be different from a single motor unit!A single motor unit is all the muscle fibers controlled by a single motor neuron.Multiple motor unit summation is when a smooth and steady increase in muscle tension is produced by increasing the number of active single motor units.Notice that what's being described is not something having to do with a some non-existent thing called a 'multi motor unit', but rather is a summation of many active singlemotor units.
Motor unit = the single motor neuron and the multiple muscle fibers that it innervates.
Each muscle cell is only innervated by a single motor neuron, but each motor neuron innervates any number of muscle cells. When an action potential travels down the axon of an alpha motor neuron, it will depolarize several muscle cells at the same time, a phenomenon known as summation.
The amount of motor units that is needed to lift 160 pounds will be greater that the number required when lifting 80 pounds. This is due to the nervous system reading the situation and determining the number of units required. The smaller the muscle, the more delicate the control can be.
controlled output of action potentials, progressive recruitment of motor units, control of the rate of attachment/reattachment of actin and myosin heads and the power stroke rate
recruitment