Lecture 3-spinal cord pt 3

Question 1

what does gray matter contain

what does white matter contain

Answer 1

• cell bodies and their dendritic processes and synaptic connections
• myelinated fibers/axons going longitudinally

Question 2

what is a tract/fasciculus

Answer 2

collectoin of axons w/ a common origin, course, and termination

Question 3

what is a funiculus/column

Answer 3

2 or more fasciculi

Question 4

what does the dorsal funiculus contain?

Answer 4

fasciculus gracilis (all lvls)
fasciculus cuneatus (C1-T6)

Question 5

what do the ventral funiculus contain?

Answer 5

the ventral white commissure

Question 6

where is the dorsal intermediate sulcus found

Answer 6

midthoracic segments and above (C1-T6)

-notably absent in lumbar regions, only found where there is fasiculus cuneatus

Question 7

which fissure/sulci is very deep?

Answer 7

ventral median fissure unlike the dorsal median sulcus

Question 8

what receives dorsal roots white

Answer 8

dorsal lateral

Question 9

where do ventral roots emerge white

Answer 9

ventral lateral

Question 10

what does the dorsal horn gray contain

Answer 10

sensory

Question 11

what does the ventral horn gray contain

Answer 11

motor nuclei

Question 12

waht does the lateral horn gray contain? where is it present at?

Answer 12

autonomic motor

only present w/ symp pre gang cell body (T1-L3 only)

Question 13

what is the substantia gelatinosa homologous to?

Answer 13

spinal trigeminal nucleus

Question 14

where is clarke’s nucleus found?

Answer 14

T1-L3

Question 15

what information does substantia gelatinosa carry?

Answer 15

senosry in function, temperature
substance P
these are nuclei

Question 16

where is clarke’s nucleus prominent at

Answer 16

lower thoracic levels

Question 17

where is clarke’s nucleus located? why is it located there?

Answer 17

dorsal horn gray bc of its function in sensory prcoessing

Question 18

waht does substance P act liek a cap to

Answer 18

dorsal horn

Question 19

what does the ventral horn contain

Answer 19

cell bodies for lower motor neurons and found at all levels of the cord

Question 20

what are the two types of lower motor neurons

Answer 20

alpha motor neurons: innervate extrafusal striated skeletal muscle fibers (“do work” when lifting)

gamma motor neuron: innervate intrafusal muscle fibers of muscle spinkles (keeps muscle spindle receptor sensitive to new changes in lenght)

Question 21

what happens when alpha motor neurons are lesioned

Answer 21

cant contract skeletal muscle which leads to paralysis

Question 22

why do alpha motor neurons have enormous cell bodies and dendritic trees?

Answer 22

bc everyone wants to influence them. there are lots of descending tracts and reflex pathways that will want to synapse on them in order to influence their final decision as to whether to “fire” to contract msucle

Question 23

how do alpha motor neurons leave the ventral horn gray? what do they eventually merge w/ and innervate?

Answer 23

via ventral roots and will eventually merge into the spinal nerve and go out to the periphery to innervate skeletal muscle

Question 24

what do alpha motor neurons that are located more medially tend to innervate

Answer 24

axial muscles or ones that are considered proximal like shoulder and arm

Question 25

in the chunk of ventral horn that is located more lateral, what do those alpha motor neurons tend to innervate/

Answer 25

the appendicular or distal muscles like the forearm and hand (limbs)

Question 26

where are flexor motor neurons located at in the ventral horn ? where are extensor motor neurons located in the ventral horn?

Answer 26

more dorsally in the ventral horn more ventral in the ventral horn

Question 27

where is the intermediolateral cell column found | what do they contain

Answer 27

lateral horns | preganglionic sympathetic fibers

Question 28

where does the oculosympathetics originate from? and wehre at

Answer 28

the ciliospinal center of budge at C8-T2

Question 29

how are the cervical regions shaped? and why?

Answer 29

oval shaped and contain the largest absolute amount of white matter. -all of the descending tracts, destined for cervial, thoracic, lumbar, and sacral have to go through the cervical region -sensory ascending tracts starting in the sacral region go up, from lumbar and adding on thoracic, adding on cervical, etc. SO...dorsal columns are more fully present at the cervical levls

Question 30

why is the cord enlarged in the lower cervical and lumbosacral regions

Answer 30

to accommodate innervation of the arms and legs

Question 31

In C5-T1, why is there more gray matter than just above or below those levels?

Answer 31

bc gray matter has to service the upper extremity (the arms) and we need more gray matter to service the lower extremity (L2-S3)

Question 32

where is the lateral horn present

Answer 32

T1-L3

Question 33

what is the origin of the brachial plexus? | lumbosacral plexus?

Answer 33

``` cervical enlargement (C5-T1) lumar enlargement (L2 - S3) ```

Question 34

in the afferent limb, what does it start out w/ ? | what is this specialized receptor aligned in parallel to?

Answer 34

sensory stretch receptor IN THE MUSCLE ITSELF | -muscle spindle: reports on muscle length

Question 35

what are the largest and fastest nerve fibers in the nervous system called how are they so fast where are their cell bodies located

Answer 35

Ia. - large diameter and highly myelinated for fast conduction velocity - these afferent fibers going to the cord have their cell bodies in the dorsal root ganglion and they enter the cord through the dorsal roots

Question 36

in the efferent limb after arriving in the cord, where does it make its ONE synapse? what kind of reflex is this? what do they innervate?

Answer 36

alpha motor neuron aka lower motor neuron monosynaptic reflex homonymous muscle that was stretched in the first place

Question 37

what happens when someone taps your patellar tendon

Answer 37

1. you quickly and efficiently stretch the muscle 2. this simultaneously stretches the stretch receptor buried inside it 3. you get a burst of activity, a direct excitatory synapse on the alpha motor neuron 4. this results in contraction of the extrafusal fibers of the same muscle that was stretched

Question 38

what are the small muscle fibers at the extreme ends of the spindle called

Answer 38

intrafusal fibers they change the lengthof the spindle apparatus itself to keep the receptor "taut" so that it's always responsive to changes in muscle length or increased loads .;......basically make the spindle receptor a better receptor, making it more sensivitve

Question 39

what innervates intrafusal fibers | what innervates extrafusal fibers

Answer 39

own innervation-by gamma motor neurons which are located in the same place in the cord as the alphas alpha motor neurons

Question 40

when you use your muscles voluntarily, what do you activate to shorten the muscle what are you keeping the same length

Answer 40

alpha motor neurons and gamma motor neurons to shorten the poles of the spindle receptor so you keep the central region the same lenght

Question 41

what are stretch reflexes important for

Answer 41

maintaining appropriate muscle tone

Question 42

what does the extra stretch on your bicep increase

Answer 42

the activity of your Ia's causing an instantaneous monosynaptic connection w/ efferents to shorten the length of that bicep and overcome the unexpected load

Question 43

waht is hyporeflexia | waht is hyperreflexia

Answer 43

sometimes, due to pathology tapping the tendon doesn't do much -othertimes, due to other types of pathology, reflexes are exaggerated or display hyperreflexia (from a loss of inhibitory influence on these pool of cells

Question 44

what is another type of sensory muscle receptor that is not a length receptor wehre is it located

Answer 44

force receptor-the golgi tendon organ (GTO) and is located not w/in the msucle but w/in the tendon

Question 45

why do skeletal muscles and tendons have proprioceptors

Answer 45

to give information about body sense | they use fast fibers

Question 46

what does the dorsal column medial lemiscus pathway use for proprioceptors what about anterolateral system?

Answer 46

larger diameter fibers having faster conduction velocity | -uses the second 2, smaller diameter fibers w/ slower conduction velocity

Question 47

what is the withdrawal reflex

Answer 47

polysynaptic. its a protective reflex in helping you withdraw a limb from a painful stiumus

Question 48

what cause the withdrawal reflex

Answer 48

nociceptive (pain) receptors in the skin

Question 49

what is crossed extension reflex

Answer 49

also increase extensor tone on the opposite leg via interneurons that cross the midline to have the opposite effect in the other leg so the pt has something to stand on - active extensor on the other leg and inhibit those flexors - involves the entire lumbar cord -adpated, won't see this reflex in the upper limbs

Question 50

what are the 3 destintions that a single incoming axon will supply

Answer 50

reflex, cerebellum, and cerebral cortex

Question 51

what else do afferents do other than reflexes

Answer 51

send info up the cord to the brain