Exam 3 Review:  Chapter 09:  General Properties of Muscle Tissue

thermogenesis - The generation or production of heat by physiological processes; in humans the main source of heat comes from contractions of skeletal muscles (muscle tone and shivering); additional modest increases in general metabolism are regulated by the thyroid hormones, T3 and T4.

shivering - The irregular involuntary contractions of skeletal muscles which produce vibrations of the muscles rather than coordinated movements of limbs; triggered in response to cold or fear or in some inflammatory responses such as fevers; a mechanism for thermogenesis

excitability = irritability - The property manifested by living organisms, and certain of their tissues (e.g., nervous, muscular, and glandular tissues), of responding to a stimulation of some sort, generally a response to some sort of kinetic energy, (e.g., light, sound, motion, etc.)

conductivity - The ability of a tissue to receive a stimulus and transmit a wave of excitation (electrochemical activity), an impulse, over the rest of the structure,and perhaps to adjacent cells in the tissue; a property of nervous, muscular, and glandular tissues.

contractility - The power possessed by the fibers of living (skeletal, cardiac and smooth) muscle of contracting or shortening in length which is achieved by the interaction of cytoplasmic contractile proteins, e.g., actin and myosin.

extensibility - The term used to describe the ability of a muscle to be stretched after a contraction, even to a length greater than the resting length.

elasticity - The inherent property in tissues by which they recover their former shape and dimensions, after the removal of external pressure or altering force; springiness; tendency to rebound; as, the elasticity of muscle tissue.

List:

2. Three functions of skeletal muscle tissue.

         
motion: external (walking, running, talking, looking) and internal (heartbeat, blood pressure, digestion, elimination) body part movements stabilization: maintain body posture, stabilize joints – muscles have tone even at rest thermogenesis: generating heat by normal contractions or by shivering

3. Five physiological characteristics of muscle tissue.

          excitability = irritability, conductivity, contractility, extensibility, elasticity 

Sketch and Label:

5. A diagram illustrating homeostatic thermogenesis by the shivering mechanism.

The figure below illustrates the complete control of thermogenesis.  To answer this question on an exam, you only need to note that when internal body temperature drops below normal, the hypothalamus will generate motor commands.  Some of those commands, by indirect pathways, will lead to an increase in uncoordinated motor commands to most of the skeletal muscles which leads to uncoordinated muscular contractions ("shivers").  The increased metabolism required to generate the ATPs to power this uncoordinated muscular contraction generates "waste heat" as a by-product.  That waste heat will warm the body.  When the body temperature returns to normal, the shivering will cease.