Neuro: Sensory & motor

Question 1

what are the 5 types of sensation receptors:

Answer 1

1. touch- mechanoreceptors
2. proprioception
3. temp
4. nociceptors- pain
   fast: extremes of thermal and mechanical
   slow: polymodal/unmyelinated- slow throbbing/delayed

Question 2

what are the types of touch- mechanoreceptors

Answer 2

2-point discrimination
velocity/direction across skin
stretch/joint rotation
stretch/indent in skin

Question 3

sensory unit arrangments: 1st, 2nd and 3rd order neurons

Answer 3

1st: spinal: PNS–> CNS
2nd: spinal: reflex networks –> thalamus
3rd: thalamus –> cortex in the brain
most interneurons process and modify info @ 2nd and 3rd

Question 4

trigeminal sensory neurons

Answer 4

“dorsal root ganglia” of the face and cranial features. true dorsal root ganglia do limbs and trunk

Question 5

what are the 2 other neuronal pathways that an axon entering the CNS could take other than going to do local spinal cord reflexes and initiate movement? aka what are the sensory ones? what feelings do they transmit?

Answer 5

1. posterior dorsal column - medial leminiscus path: rapid transmission for 1. descriminative touch (2-point), proprioception, stereogenesis, vibrations
2. Anterolateral pathway:
   - lateral spinothalamic: rapid, sharp pain to thalamus
   - anterior spinothalamic: slow throbbing pain, thermal sensation, crude touch, pressure

Question 6

where do the pathways crossover to the other side? Medial-Lem vs Anterolateral?

Answer 6

Dorsal Column- medial Lem. : in medulla

Anterolateral: in the spinal cord

Question 7

what does the RAS system do for antero-lateral pathways?

Answer 7

in the anterior branch (RAS developed in midbrain where anterior processes through)
–>pain = increased wakefullness = inc. BP and HR

Question 8

where does the central processing of somatosensory info take place?

Answer 8

in the somatosensory cortex in the parietal lobe (just behind the central fissure/sulcus)

1. primary somatosensory cortex (just posterior to sulcus)
2. somatosensory assoc. cortex (just posterior to hommunculus)

Question 9

what does the primary somatosensory cortex do vs the somatosensory assoc. cortex?

Answer 9

primary: input from afferents in corresponding peripheral areas
assoc cortex: transforms raw material of sensation into meaningful experience

Question 10

UMNs vs LMNs

Answer 10

upper motor neurons: originate in motor cortex of brain- voluntary movement –> spinal cord: control LMNs
lower motor neurons: muscles/tendons –> spinal cord

Question 11

3 parts of the motor system

Answer 11

1. descending spinal tracts (brain stem, cerebellum, basal ganglia, motor cortex)
2. spinal cord (reflexes- posture, movement)
3. Neuromuscular (motor neurons, NM-junction, muscle fibers)

Question 12

two parts of a motor unit/ LMN

Answer 12

motor neuron (in ventral horn) and muscle it innervates

Question 13

where is the motor cortex/motor strip located?

Answer 13

posterior portion of frontal lobe, anterior to central sulcus

Question 14

what do the premotor cortex and supplementary motor cortex do?

Answer 14

pre-motor: located anterior to primary motor cortex, does patterned movements (throwing a ball)
supplementary (SMA): complex, skilled movements, involved BOTH sides of body

Question 15

what does the primary motor cortex do? what is the path of UPN down for this action?

Answer 15

voluntary movement. UMNs start here –> internal capsul (between thalamus and Basal Ganglia–>midbrain –>pons –>meduall (w/ pyramids) –> spinal cord

Question 16

what are the multiple places that output motor neurons project from the motor cortex project?

Answer 16

• premotor and somatosensory on the same side
• opposite side of the cortex
• descend to thalamus and BG
• brain stem and spinal cord (voluntary movement path)

Question 17

output neuron/ UMN –> LMN from motor cortex, where does the axon cross over?

Answer 17

in the medulla via the pyramids THEN goes into the spinal cord

Question 18

pyrimidal system vs extrapyrimidal system

Answer 18

both have UPN and LMN

pyrimidal: come from motor cortex, voluntary movement and muscle tone inhibition, go through pyramids at the base of the medulla
extrapyramidal: EVERYTHING ELSE- comes from places other than motor cortex (premotor, supplementary, BG), InVoluntary movement, does NOT go through pyramids of medulla

Question 19

decusation

Answer 19

“crossing over”

Question 20

what do the pyramidal paths branch off into after leaving the base of the medulla?

Answer 20

1. 80% lateral corticospinal

2. 20% anterior corticospinal

Question 21

what do the lateral and anterior corticospinal tracts of the pyrimidal system do?

Answer 21

lateral: crosses in pyramids (complex) - controls distal muscles, fine motor skills
anterior: axial and proximal muscles (balance, walking, climbing)

Question 22

if you lose voluntary muscle control, what takes over?

Answer 22

involuntary control…no muscle tone (weakness) = increase tone (excitatory –> reflex )

Question 23

lesion of UMN vs LMN?

Answer 23

UMN: weakness in all areas, increased spastic and reflexes
aka RIGID- no inhibition
LMN: weakness in more specific area, wasting/atrophy, reduced tone, fasicultation (involuntary movement)
aka FLACID- no reflex

Question 24

how are reflexes checked?

Answer 24

control of muscle tone and maintenance of posture (UMN on LMN action)

Question 25

spinal reflex

Answer 25

senses a stretch = contracts muscle
path: 1A afferent muscle to spinal cord (dorsal horn) –> (ventral horn) Alpha motor neuron –>muscle fiber

(also has a UMN coming to and from brain and spinal cord- talking to gamma neuron to coordinate twitch of intrafusal muscle fibers)

Question 26

golgi tendon reflex

Answer 26

opposite of spinal reflex
excess contraction on muscle = automatic relaxing of muscle
(tennis ball on leg)
1b afferent from tendon senses contraction –> dorsal horn of spinal cord –> tells inhibitory neuron in spinal cord –> inhibits Alpha motor neuron coming from ventral horn into muscle fiber

Question 27

flexor withdrawal reflex

Answer 27

postsynaptic reflex >1 sensory and motor acting together
-response to EXTREME pain stimuli
-one side pulls away from stimulus (contracts) and the other side extends to counteract and keep balance
(hand pulling away from hot plate, other arm extends)