Spinal Cord Organization

Question 1

what are segmental pattern generators?

Answer 1

eg. gait/walking reflex, complex patterns generated in only spinal cord

Question 2

spinal nerve at L5 longer or shorter than at T7?

Answer 2

Longer

Question 3

Where do to a lumbar puncture?

Answer 3

L3-4

Question 4

more or less white matter as you go caudally? rostrally?

Answer 4

caudally: less white matter
rostrally: more white matter for more tracts joining up

Question 5

nociceptors travel up which system on which side?

Answer 5

contralateral side

anterolateral system

Question 6

mechanoreceptors travel up which columns?

Answer 6

dorsal or posterior columns

Question 7

more ascending or descending tracts?

Answer 7

more descending

Question 8

lateral descending tract is for what?

Answer 8

motor

Question 9

communication within spinal cord?

Answer 9

yes, a lot of interneurons talk to each other

Question 10

as you move more later in ventral roots, what is innervated?

Answer 10

more distal muscles

Question 11

medial ventral horn innervated what?

Answer 11

proximal muscles

Question 12

what is a motor unit

Answer 12

a motor neuron connected to a collection of muscle fibers: varied in numbers

Question 13

what is an intrafusal muscle fiber?

Answer 13

sensory fiber embedded within muscle spindle to detect amount of muscle stretch

Question 14

can an intrafusal muscle fiber contract?

Answer 14

yes to adjust their position with surrounding muscles via gamma motor neurons (not alpha like the normal ones)

Question 15

What is the only exception where a muscle as no intrafusal muscle fiber?

Answer 15

extraoccular eye muscles

Question 16

What do golgi tendon organs do?

Answer 16

respond to force

placed in series

Question 17

How are intrafusal muscle fibers placed in spindle?

Answer 17

in parallel

Question 18

what is the ‘most important sign in neurology’?

Answer 18

monosynaptic stretch reflex

Question 19

When the spindle afferent sends signal after stretch reflex, where does it go what does it do?

Answer 19

Goes to dorsal horn splits:
activates agonist
interneuron to antagonist: inhibites antagonist

Question 20

is golgi organ afferent signalling monosynaptic?

Answer 20

Nope.

Question 21

what is intersegmental cross-extensor reflex?

Answer 21

usually in cats/dogs, withdraw one limb, extend other 3 to maintain stability

Question 22

are all interneurons short?

Answer 22

Nope, some really long can span multiple segments for complex reflexes

Question 23

do lateral of medial have short or long interneurons?

Answer 23

medial: longer interneurons
lateral: shorter interneurons

Question 24

spinal cord is in a usual state of?

Answer 24

inhibition until it’s lifted to allow excitation

Question 25

what is an upper motor neuron problem?

Answer 25

any neuron that affects excitability of lower motor neuron

Question 26

what is lower motor neuron?

Answer 26

ventral horn of spinal cord out to periphery

Question 27

most interneurons are excitatory or inhibitory?

Answer 27

inhibitory

Question 28

if you have a lesion in a descending upper motor neuron, what happens down stream?

Answer 28

increased tone/clonus cause lost inhibition

Question 29

if you have a lesion in a lower motor neuron what happens downstream?

Answer 29

flaccid

Question 30

What happens to muscles affected by stroke?

Answer 30

increased tone, exaggerated contractions where there is little inhibition