{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

47 knes 462 fk 08 the froce your muscele create during

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: muscle fiber is correlated with axonal conduction speed. 47 KNES 462 ©FK ‘08 the froce your muscele create during motor activities--its not a binary signal off or on- you cant tune the force over a very whide range The Motor Unit: Force Grading I • Two ways to grade force of muscle contraction: – recruitment of muscle cells is ranked (size principle): 2 mechanisms • slow units first, respond to weak synaptic input • fast fatigue-resistant next size principal--- the slow twitch activate first.then int--then fast twitch • fast fatigable last modulation--at 100 hz the muscel goes into fused tetonous-- aka muscel cramp. – modulation of firing rate of motor neurons: • lowest firing rates for steady contraction: ~ 8 Hz • higher rates for more intense contractions: ~ 25-80 Hz 48 KNES 462 ©FK ‘08 The Motor Unit: Force Grading II • Other scenario: constant low force needed over long period of time – Approx. half of muscle fibers are active; – With ongoing contraction, some fatigue, and some ‘rested’ ones jump in and assist; – Fast fatigue resistant fibers are additionally recruited ; – Large units (fast fatigue) kick in; – This scenario is only valid for fairly low contraction only works if blood flow is not affected forces (<25% maximum voluntary muscle contraction [MVA]) 49 KNES 462 ©FK ‘08 KNES 462 The Motor Unit: Size Principle 50 KNES 462 ©FK ‘08 recpetor-records the state of something Sensors / Receptors 53 KNES 462 ©FK ‘08 Muscle Receptors they are called proprioceptors--...
View Full Document

{[ snackBarMessage ]}