Spinal Cord II

Question 1

How are dorsal columns and anterolateral columns organized

Answer 1

somatotopically organized

Question 2

describe somatotopic organization

Answer 2

Like arm input = layered to outside
Axons highly organized
Very organized map of body onto different parts of dorsal column white matter = somatotopic
Map preserved all the way up to cerebral cortex

Question 3

describe somatotopic org for dorsal column pathway

Answer 3

arms lateral
Legs medial

Question 4

describe somatotopic org for anterlateral pathway

Answer 4

Legs lateral
Arms medial (arms push legs laterally)

Question 5

describe what happens when damage to only one side of spinal cord = generally

Answer 5

= causes deficits in ipsilateral fine touch but contralateral pain/temp below level of lesion
Due to the fact that fine touch and pain/temp take diff routes to brain

Question 6

deescibe lesions and dorsal column pathway = fine touch and proprioception

Answer 6

Damage to right side of thoracic spinal cord = causes loss of fine touch in right foot (lose sensation on side ipsilateral to lesion)
Normal fine touch in left foot

Question 7

describe lesions and anterolateral pathway = pain and temp

Answer 7

Damage to right half of thoracic spinal cord = causes loss of pain/temp in left foot (lose contralateral side only)
Normal pain and temp in right foot

Question 8

describe what spinal cord is part of

Answer 8

Part of a sensory motor hierarchy that includes brainstem, and higher brain regions like cerebral cortex, cerebellum and basal ganglia
Sensory systems and motor systems = sensory input connected to motor outputs at every level, always interacting and talking

Question 9

describe spinal cord in hierarchy

Answer 9

Protective reflexes, locomotion
Sensory - lowest level of processsing
Has built in programs

Question 10

describe brainstem in hierarchy

Answer 10

Higher level
Stereotyped behaviours like facial expressions and defensive behaviour

Question 11

describe cerebral cortex in hierarchy

Answer 11

Most complex
Complex, voluntary behaviour

Question 12

descibe ex of walking in context of hierarchy

Answer 12

Circuitry for walking contained In brain = does thinking for you
For movement control = hierarchy in diff direction, opposite
Decision to walk = at cerebral cortex —> do not have to think abut walkin, just think you want to walk = then it happens, don’t have to think about contraction of individual muscles or anything
Walking program built into circuitry of spinal cord gray matter (very complex circuitry) = central pattern generators that control walking, like dog itching, fish swimming

Building blocks fo walking already programmed into spinal cord and brainstem
Also have cpg in brain like for facial expression

Question 13

what are the simplest goal direct movements

Answer 13

Spinal reflexes
Lower level sensory motor integration
Spinal cord and peripheral nerves = below level of consciousness
Sensory motor loops

Question 14

name the 2 kinds of reflexes

Answer 14

Stretch (knee reflex)
Withdrawal reflex (remove hand from hot stove)

Question 15

describe spinal reflexes = gen

Answer 15

Involuntary coordinated patterns of muscle contraction and relaxation
Elicited by peripheral stimuli

Question 16

describe spinal reflexes = sensory stimuli

Answer 16

Sensory stimuli comes from receptors in msucles, joints and skin

Question 17

describe spinal reflexes = produce what

Answer 17

Produce complex movements that serve protective and postural functions

Question 18

what are reflexes = qualities

Answer 18

Complex and highly adaptive
Simplest ex of goal directed behaviour

EX = If hit hand with thumb tack - diff orientations, same stimulus but output is diff bc will move hand in diff directions
Adapted to position of body
Behaviorually adaptive - serves purpose

Question 19

Describe purpose of stretch reflex

Answer 19

Like if holding box and add another heavy box = hands lower and come back = help keep limb at specific positions/angles despite changes in load = top down control

Question 20

describe basic circuit of stretch reflex

Answer 20

Patellar reflex = tendon stretches across knee - attached to muscle on top of leg = muscle stretches —> activates sensory neurons
—> into dorsal column gray matter
= synapse with motor neurons = causes muscle contraction
Also synapses with inhibitory interneuron = helps other muscle relax
So leg kicks out

Question 21

are reflexes controlled only at level of spinal cord

Answer 21

Nawh
Can be adjusted by top down signals
Like if drop pan but baby on floor under it = will catch hot pan and set it down
If fall with hot coffee = hand wont go out to catch fall, but will protect coffee
= brain can interact with and modulate cpgs

Question 22

Describe reflexes= specifics about sensory signals

Answer 22

Discrete stimulus can produce large contractions of multiple msucles = suggest divergence of sensory signal

Question 23

what are reflexes modulated by

Answer 23

Extent and force of muscle contraction depend on stimulus intensity
= reflexes are modulated by properties of the stimulus

Question 24

are reflexes regulates or modified

Answer 24

Reflexes are regulated and modified by descending inputs form higher brain areas

Question 25

what utilizes reflex circuits

Answer 25

complex voluntary movements utilize existing reflex circuits

Question 26

why/how do reflexes work

Answer 26

Reflexes work bc of complex circuitry of gray matter

Question 27

what are central pattern generators

Answer 27

Cpgs are formed by intrinsic circuitry of spinal cord —> responsible for rhythmic movements like walking, stretching and motions of swimming fish

Question 28

what do higher brain regions do

Answer 28

Manipulate/utilize lower level programs