the muscular system. 3 types of muscles a muscle is composed of a variety of tissues
TRANSCRIPT
Muscular Responses
• Twitch – a brief period of contraction followed by a period of relaxation
• Phases 1. Latent Period – muscle tension is beginning2. Period of ContractionMuscle fibers shortening3. Period of RelaxationCa2+ renters the sarcoplasmic reticulum
Relaxation –1.acetylcholinesterase decomposes ACh in the synapse
2. Ca2+ pump quickly moves Ca2+ back into sarcoplasmic reticulum
Figure 9.14b
Latent period
Extraocular muscle (lateral rectus)
Gastrocnemius
Soleus
Singlestimulus
(b) Comparison of the relative duration of twitch responses of three muscles
• Summation – The force of individual twitches combines• Incomplete tetanus – Ca2+ increases in sarcoplasm results in
quivering response• Complete Tetanus – no period of relaxation
The force that a muscle can generate is dependent on the length that it is stretched before stimulation
The force that a muscle develops depends on:
1. The frequency at which individual muscle fibers are stimulated
2. How many fibers take part in the overall contraction - RECRUITMENT
Types of Contractions
Isotonic Contraction – muscle changes length and moves a load
– Concentric contraction – a muscle shortening contraction– Eccentric contraction – a muscle lengthening contraction
Isometric contraction – tension in muscleincreases but the muscle does not lengthenor shorten
Muscle Fatigue
• Exercise for a long period of time may cause a muscle to lose the ability to contract - FATIGUE
• Why?1. decreased blood flow2. ion imbalances across sarcolemma from repeated
stimulation3. psychological loss of the desire to exercise4. increase in lactic acid = lowered pH which prevents
muscles from responding to stimulation
What is a Cramp?
• A sustained, painful, involuntary muscle contraction• Result from decreased electrolyte concentration in
extracellular fluid which triggers uncontrolled muscle stimulation
Sliding Filament Theory
• http://www.blackwellpublishing.com/matthews/myosin.html
http://www.mhhe.com/biosci/esp/2002_general/Esp/folder_structure/su/m4/s11/sum4s11_9.htm