Lecture 5: Spinocerebellar Pathway

Question 1

What info does the spinocerebellar pathway transmit?

Answer 1

Unconscious proprioception to cerebellum

Question 2

Clarke’s Column

Answer 2

C8-L3; where first order spinocerebellar neurons synapse in that area

Question 3

How do spinocerebellar neurons below L3 run in the spinal cord?

Answer 3

They run in the fasciculus gracillis until they synapse in L2/L3

Question 4

How do spinocerebellar neurons above C8 run in the spinal cord?

Answer 4

They run in the fasciculus cuneatus until synapse in accessory cuneate nucleus

Question 5

How do 2nd order spinocerebellar neurons in Clarke’s column get to the cerebellum?

Answer 5

Run ipsilaterally into cerebellum via inferior peduncle

Question 6

How do neurons from the accessory cuneate nucleus get to the cerebellum?

Answer 6

Ipsilaterally through the inferior cerebellar peduncle

Question 7

What types of nerves innervate golgi tendon organs?

Answer 7

1b

Question 8

Golgi tendon organs

Answer 8

Sense muscle tension or change in tension; sit in tendons at end of muscles

Question 9

What types of nerves innervate muscle spindles?

Answer 9

1a- muscle length and change in length, II- muscle length, gamma motor fibers- changes length of spindle to better match muscle length

Question 10

How do intrafusal muscle spindles work?

Answer 10

Tension causes mechanoreceptors send action potentials on nerves

Question 11

Static nuclear bag fibers

Answer 11

Sense muscle length only; innervated by 1a and II

Question 12

Dynamic nuclear bag fibers

Answer 12

Sense change in muscle length; 1a only

Question 13

Nuclear chain fibers

Answer 13

Sense muscle length only; Innervated by 1a and II

Question 14

Type II muscle fibers

Answer 14

Only respond to muscle length

Question 15

Type 1a muscle fibers

Answer 15

Respond to muscle length and change in length

Question 16

Gamma motor neurons

Answer 16

Change length of intrafusal fibers to better match length of muscle

Question 17

Myotactic/stretch reflex

Answer 17

Muscle stretch activates 1a fibers; go to spinal cord and alpha motor neurons cause that muscle to contract; antagonistic muscles to relax

Question 18

Renshaw cells

Answer 18

Alpha MNs activate these which then calm the muscle stretch reflex by calming contracting muscle and inhibiting inhibition of antagonistic muscles

Question 19

Inverse stretch reflex

Answer 19

Heavy load activates 1b fibers which inhibit alpha MNs, 1b also activate alpha MNs of opposing muscles; active under normal conditions

Question 20

Flexor Reflex

Answer 20

Spinocerebellar tract neurons both activate and inhibit muscles to move away from a painful stimulus without falling down, via alpha MNs