Lecture 30: Spinal Reflex Circuits

What type of force do intrafusal muscle fibers have and what do they contain?

negligible amounts of force but they contain the muscle spindles

What happens to the intrafusal muscle fibers when alpha motor neurons are activated?

gamma motor neurons contract the intrafusal muscle fibers

What happens to a muscle if you stimulate the alpha motor neuron?

contraction

What happens if the alpha motor neuron is stimulated but the gamma motor neuron is not?

intrafusal muscles don’t monitor the stretch and end up hanging limp

Passive stretch

(Where is the info sent)

when a muscle is stretched unexpectedly, or not due to input from motor neurons

* info is sent to spinal cord

What types of feedback do stretch reflexes have?

both positive and negative

What is the main similarity between golgi tendon organs and muscle spindles?

both give us proprioceptive information

What is the main difference between golgi tendon organs and muscle spindles?

both fire in response to different events

* Muscle spindles react to passive stretch
* GTOs respond to active contraction

Whats the importance of the crossed extension reflex?

If you stepped on a tack, when you picked your foot up to stop the pain, the crossed extension reflex made sure that your other leg was there and balanced before you picked the one foot up

Lou Gherig’s disease

A neuro degenerative disease that results in the weakness of all your muscles

* symptoms: muscle weakness, often in the limbs