Neuro: Sensory & motor Flashcards
what are the 5 types of sensation receptors:
- touch- mechanoreceptors
- proprioception
- temp
- nociceptors- pain
fast: extremes of thermal and mechanical
slow: polymodal/unmyelinated- slow throbbing/delayed
what are the types of touch- mechanoreceptors
2-point discrimination
velocity/direction across skin
stretch/joint rotation
stretch/indent in skin
sensory unit arrangments: 1st, 2nd and 3rd order neurons
1st: spinal: PNS–> CNS
2nd: spinal: reflex networks –> thalamus
3rd: thalamus –> cortex in the brain
most interneurons process and modify info @ 2nd and 3rd
trigeminal sensory neurons
“dorsal root ganglia” of the face and cranial features. true dorsal root ganglia do limbs and trunk
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?
- posterior dorsal column - medial leminiscus path: rapid transmission for 1. descriminative touch (2-point), proprioception, stereogenesis, vibrations
- Anterolateral pathway:
- lateral spinothalamic: rapid, sharp pain to thalamus
- anterior spinothalamic: slow throbbing pain, thermal sensation, crude touch, pressure
where do the pathways crossover to the other side? Medial-Lem vs Anterolateral?
Dorsal Column- medial Lem. : in medulla
Anterolateral: in the spinal cord
what does the RAS system do for antero-lateral pathways?
in the anterior branch (RAS developed in midbrain where anterior processes through)
–>pain = increased wakefullness = inc. BP and HR
where does the central processing of somatosensory info take place?
in the somatosensory cortex in the parietal lobe (just behind the central fissure/sulcus)
- primary somatosensory cortex (just posterior to sulcus)
- somatosensory assoc. cortex (just posterior to hommunculus)
what does the primary somatosensory cortex do vs the somatosensory assoc. cortex?
primary: input from afferents in corresponding peripheral areas
assoc cortex: transforms raw material of sensation into meaningful experience
UMNs vs LMNs
upper motor neurons: originate in motor cortex of brain- voluntary movement –> spinal cord: control LMNs
lower motor neurons: muscles/tendons –> spinal cord
3 parts of the motor system
- descending spinal tracts (brain stem, cerebellum, basal ganglia, motor cortex)
- spinal cord (reflexes- posture, movement)
- Neuromuscular (motor neurons, NM-junction, muscle fibers)
two parts of a motor unit/ LMN
motor neuron (in ventral horn) and muscle it innervates
where is the motor cortex/motor strip located?
posterior portion of frontal lobe, anterior to central sulcus
what do the premotor cortex and supplementary motor cortex do?
pre-motor: located anterior to primary motor cortex, does patterned movements (throwing a ball)
supplementary (SMA): complex, skilled movements, involved BOTH sides of body
what does the primary motor cortex do? what is the path of UPN down for this action?
voluntary movement. UMNs start here –> internal capsul (between thalamus and Basal Ganglia–>midbrain –>pons –>meduall (w/ pyramids) –> spinal cord
what are the multiple places that output motor neurons project from the motor cortex project?
- 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)
output neuron/ UMN –> LMN from motor cortex, where does the axon cross over?
in the medulla via the pyramids THEN goes into the spinal cord
pyrimidal system vs extrapyrimidal system
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
decusation
“crossing over”
what do the pyramidal paths branch off into after leaving the base of the medulla?
- 80% lateral corticospinal
2. 20% anterior corticospinal
what do the lateral and anterior corticospinal tracts of the pyrimidal system do?
lateral: crosses in pyramids (complex) - controls distal muscles, fine motor skills
anterior: axial and proximal muscles (balance, walking, climbing)
if you lose voluntary muscle control, what takes over?
involuntary control…no muscle tone (weakness) = increase tone (excitatory –> reflex )
lesion of UMN vs LMN?
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
how are reflexes checked?
control of muscle tone and maintenance of posture (UMN on LMN action)
spinal reflex
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)
golgi tendon reflex
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
flexor withdrawal reflex
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)
