BIOL 319 Lecture: Motor Units

What are the 2 components of motor units?

neuronal and fiber

How many fibers are usually contained in small motor units?

5-10, 6-12 fibers

How many neurons are contained in one motor unit?

only one

What happens when a neuron fires an action potential 

NMJs have AP at the same time 

Activation of the synapse at the same time 

Contraction at the same time 

How big is an intermediate motor unit?

tens and tens of fibers (20s,50s,100s)

Is there a range of intermediate motor units?

yes: some small, some intermediate some large

How many fibers are in a large motor unit?

1000s of fibers

What units does the average muscle contain?

all of them: some small, some intermediate, some large

Which units are found in muscles responsible for precise movement of the fingers?

small motor units

What is the function of small motor units?

precision NOT power or strength

How many fibers can small motor units add or subtract at a time? 

6 at a time 

What units are contained in powerful muscles? 

large motor units 

What are some examples of large motor units?

quadriceps, hamstrings, gastrocnemius

What is the function of large motor units?

power and speed

Which muscles are needed to endure?

torso and neck: for posture

How do neck muscles not get tired?

motor units have shift work: some inactive and some active

What are the motor units in the muscle analogous to?

workers in factory 16 hours a day

What is the treatment for myasthenia gravis?

acetylcholinesterase inhibitors: lead to increase in Ach

What is the treatment for spastic paralysis?

botulinum toxin: prevents uncontrolled motor neuron firing in the spinal cord