Physiology 500A

Lecture # 11

Dr. H. Rasgado-Flores

Available Now:

LINEAR MOTOR

Rugged and dependable: design optimized by world-wide field testing over an extended period. All models run on a wide range of commonly available fuels. Low stand-by power, but can be switched within msec to as much as 1KW mech/Kg. Modular construction, and wide range of available subunits.

Choice of two control systems:

1) Externally triggered mode. Versatile, general-purpose units. Digitally controlled by picojoule pulses. Energy amplification 106 approx.

2) Autonomous mode with integral oscillators. Especially suitable to pumping applications. Modules available with frequency and mechanical impedance appropriate for solids and slurries, liquids and gases.

Many optional extras e.g. built-in servo (length and velocity) where fine control is required. Direct piping of oxygen. Thermal generation. Etc.

GOOD TO EAT !

(Notice of a lecture on Muscle Presented by Professor D.R. Wilkie to the Institution of Electrical Engineers in London)

PURPOSE

1) To describe the cellular components of skeletal muscle

2) To describe the cellular and molecular processes of muscle contraction

3) To describe the basic mechanical variables in muscle contraction

4) To describe in the force-length relationship in isometric contractions

5) To describe the velocity-load relationship in isotonic contractions

I) INTRODUCTION

The ability to move is one of the fundamental characteristics of a living organism. Muscle contraction is an specialized example of this phenomenon. The main functions of skeletal muscle tissue are development of tension and shortening. The nervous system coordinates the activity of various muscles and of different parts of one or more muscles to produce useful movements and postures. The effect of muscle activity is transferred to the skeleton by means of tendons. The basis for movement is a biologic energy transformation called chemomechanical transduction. In this process most of the body's metabolic production of adenosine triphosphate (ATP) is converted into force or movement by muscle cells. For example, the musculature of an adult man in the resting state utilizes some 30 % of the total ATP energy generated by respiration. During very intense muscular activity, as in a sprint, the muscles consume 85% or more of the total ATP generated.

The performance of mechanical work is by no means limited to a few specialized tissues such as muscle. Actin and myosin are ubiquitous within eukaryotic cells. These proteins are involved in the movement of cells and the organelles within them. Indeed a striated muscle cell might be viewed as one end of a spectrum in which the myofibrils are relatively permanent structures, whereas in non-specialized cells the contractile components are assembled and dissolved as required. Evolution has led to specialization of muscle cells to minimize the ATP consumption required for specific functions.

It is constructive to consider why muscle, the striated variety in particular, has been such an appealing system for investigation. Firstly, a large proportion of the cell material is devoted to the contractile function. The two fundamental proteins involved, actin and myosin, comprise 80% of the structural proteins and are therefore available in large amounts for chemical characterization. Secondly, these proteins are arranged in a regular way which provides a clue to their mechanism of interaction. Thirdly, the contraction occurs on a macroscopic scale.