Why this is a CLASSIC PAPER?
There are three major reasons why this paper is considered a classic paper. Firstly it was the first paper to directly investigate the functional significance of motor neuron size and was one of a series of five papers published in 1965 linking many different neuromuscular concepts together such as recruitment, usage and motor neuron pool. (cite Amanda paper)
Secondly it was the first paper to establish a set of rules that defined orderly recruitment of motor units coined the size principle. This relatively simple and seemingly logical principle was easy to quantify and is one of the major reasons why this paper has been cited over 1600 times and can be found published in physiology textbooks all around the
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Collectively these 3 major factors have ensured that Henneman’s pioneering work on muscle control and recruitment will remain classical.
Section 2:
Experimental Aim:
Henneman (1965) investigated the relationship of neuron excitability and its size in the stretch reflex of the triceps surae muscle of the decrebrated cat. His finding lead him to believe there is a set of principles dictating the order of muscle unit recruitment as dictated by size which he coined the size principle. While his work was ground breaking at the time, and as previously mentioned, the size principle has been confirmed many times over the years. It is important to understand exactly the scope and limitations of the size principle. We wanted to extend Henneman’s work by investigating whether the size principle is consistent in the older adult. In their experiment they didn’t indicate the age of the cats only mentioning that they were adults. It is well understood that the ageing process causes a shift in motor unit physiology. Beyond the ages of 60-70 years there is a loss of motor neurons, predominately larger ones with higher recruitment thresholds, which in turn causes a decrease in muscle fibres, specifically the type 2 fibres. Many of the muscle fibres will atrophy and die, however some will be re-innervated by the mainly existing small motor neurons, which results in larger motor
The years proceeding these individuals mentioned above others paved more of the road that lead us to what we know of this science today. Some of the major players many are familiar with are Leonardo da Vinci and Galileo where others we may not know include Girmaldi, Oster, William Harvey, Niels Stensen to name a few. Kinesiology is an ever growing field and contributions to its science are made even today. Let us not be fooled into thinking that this field of science only dates back to the mid 20th century. After some research I have uncovered the very origins and roots to the area in which I have decided to study. I hope by learning of the early contributions and discoveries that I can learn from them with the hopes of one day making a contribution of my
The results in Figure 2. show that increasing the stimulus strength (V) from 0 to o.40V will result in an increase of Active Muscle force generated by the gastrocnemius muscle in the Buffo Marinus, confirming the hypothesis. The force generated plateaus when the stimulus is beyond o.40V.
The power stroke is responsible for the contraction of the muscle and force generation. ATP binding to the myosin head detaches the myosin head from the actin filament and allows the cycle to repeat. The coordinated contraction and relaxation of many muscles in an antagonistic fashion is the basis for the kinematics of any movement.
Martini, F. H., Nath, J. L., and Bartholomew, E. F. “Muscle Tissue.” Anatomy & Physiology. 9th
Motor Unit Recruitment - the successful activation of the same and more motor units with larger strength and voluntary muscle contraction
A simple spinal reflex is a reflex—involuntary, graded, patterned response to a stimulus—that is produced via a single synapse between sensory axons and motor neurons and confined to the spinal cord. In this experiment, two simple spinal reflexes—the myotactic reflex and the H-reflex—were stimulated. We compared a) the latency period—the amount of time between a stimulus and the effector response— and the amplitude—magnitude of an electrical signal—of each reflex; then, b) the effect of the Jendrassik Maneuver (JM) upon the latency period and amplitude of each respective reflex. For the myotactic response, a mechanical stimulus, a sharp strike of the patellar tendon, was utilized to elicit a signal in stretch receptors; however, to trigger the H-reflex, an electrical impulse was applied. These reflexes originate from an action potential produced by a sensory neuron when a stimulus is applied. Sensory neurons transmit the action potentials to an integrating center—the spinal cord—where a response is determined. Then, this response is taken back to the effector organ via motor neurons. The reflex occurs while the brain is becoming aware of the stimulus. Furthermore, the myotactic reflex is
O B J E C T I V E S 1. To define these terms used in describing muscle physiology: multiple motor unit summation, maximal stimulus, treppe, wave summation, and tetanus. 2. To identify two ways that the mode of stimulation can affect muscle force production. 3. To plot a graph relating stimulus strength and twitch force to illustrate graded muscle response. 4. To explain how slow, smooth, sustained contraction is possible in a skeletal muscle. 5. To graphically understand the relationships between passive, active, and total forces. 6. To identify the conditions under which muscle contraction is isometric or isotonic. 7. To describe in terms of length and force the
Undoubtedly, this article is pertinent to science because it contributes to the development of muscles in
In the late nineteenth century and early twentieth century there had been some effort made towards finding the difference between the primary and secondary myopathies. It was then that they discovered that this muscular disorder was primarily in the muscles itself and that the atrophy may have been secondary and neurogenic in origin. The confusion between the two had persisted further in to the twentieth century.
The Number of motor units we have stays constant beginning at 5 years all the way to 50 years of age, but then they decrease continuously.
3:1 eplain the sliding filament theory of muscle contraction with reference to the antagonistic muscles of the upper arm.
found that motor unit twitch force remains constant or is even slightly increased following chronic denervation, challenging the theory that denervated muscle cannot be re-innervated, as believed since the findings of Gutmann. (Gutmann 1948, Fu and Gordon 1995a) Compensatory enlargement through the incorporation of denervated muscle fibers into adjacent motor units, by collateral sprouting, can make up for a loss of up to 80% of motoneurons of a muscle, as motor unit expand their size 3 to 5 fold. (Gordon, Yang et al. 1993) After 6 months of denervation maximal motor unit expansion through collateral sprouting was found, even though functional recovery was poor. (Fu and Gordon 1995b) These findings demonstrate that both the reduced number of axons reaching denervated motor endplates and atrophic muscle changes, respectively, influence poor functional outcomes after nerve injury. (Fu and Gordon 1997, Furey, Midha et al.
In the gastrocnemius muscle of the B. Marinus used, there are two types of myofilaments that are inside the muscle fibres. These myofilaments are thick filament protein called myosin, and a thin filament containing three different proteins; actin, tropomyosin and troponin. These myofilaments are arranged in myofibrils in a structure known as a sarcomere (Hopkins. M, P. 2006). The muscle in this experiment was stretched and forced to contract through an ATP-driven interaction between myosin and action called crossbridge cycling. In this process, the head of the myosin molecule extends laterally and binds with an actin molecule to form what is known as the crossbridge. The contraction of the muscle in this experiment occurs through a process called a power stroke (Hopkins.
As women age, muscle control begins to slowly decline. The choice in loss of muscular velocity seems to be voluntary due to the lack of strength training in older women. In order for muscles to strengthen, activation through endurance is necessary. The study done by Andre Gurjao, and his colleagues, suggest the use of strength training (ST) has a positive correlation on rate force development in women, specifically older women. Neuromuscular changes take affect on the power contributed within muscles that are accompanied with aging. Strength training reverses the effects of muscular power deterioration by improving neuromuscular performance in older adults (Gurjão, Gobbi,Carneiro et al., 2012).
Exercise 2: Skeletal Muscle Physiology: Activity 3: The Effect of Stimulus Frequency on Skeletal Muscle Contraction Lab Report Pre-lab Quiz Results You scored 100% by answering 4 out of 4 questions correctly. 1. During a single twitch of a skeletal muscle You correctly answered: b. maximal force is never achieved. 2. When a skeletal muscle is repetitively stimulated, twitches can overlap each other and result in a stronger muscle contraction than a stand-alone twitch. This phenomenon is known as You correctly answered: c. wave summation. 3. Wave summation is achieved by You correctly answered: a. increasing the stimulus frequency (the rate of stimulus delivery to the muscle). 4. Wave summation increases the force produced in the muscle.