Lecture 4 part 2 Flashcards
study slide 4
ye
study slide 5
ye
what are the three main functions of the somatosensory system?
- conscious perception
- modulation of movement (cerebellar) – regulates quality of movement
- arousal & alertness (via brainstem & thalamus)
what are the two sensory/ascending somatosensory pathways?
posterior/dorsal column or medial lemniscal –> also called the fasciculus grascilis and fasciculus cuneatus as it ASCENDS
anterolateal pathway–spinothalamic tract aka trigeminal thalamic
both are LONG pathways, so they DECUSSATE
what does the posterior ascending pathway sense?
vibration, joint position, and fine touch
what does anterolateral pathway sense?
pain, temp, and crude touch
describe the neurons in a somatosensory pathway
usually a 3-neuron system
1st neuron: runs from the periphery to spinal cord or medulla
2nd neuron: either a) gets input fromthe spinal cord/medulla to thalamus & cerebellum or b) input to motor neuron on effector organ (= reflex)
3rd neuron: input from the thalamus to cerebral cortex
study slide 12
ye
after the ascending tract has entered the spinal cord, either in the dorsal or anterolateral column, it will decussate:
the dorsal column decussates in the MEDULLA, and has two-point discrimination–fine touch (remember, it has vib, proprioception, and fine touch) whereas the ANTEROLATERAL decussates in the SPINAL CORD (remember it has nociception and temperature)
slide 14
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study slide 15
ye
if someone cannot feel light touch, proprioception, or lacks 2 pt discrimination –> they have a problem with dorsal column/medial lemniscal
if someone can’t feel pain or temperature, but can feel that a sharp object is touching them, they have anterolateral pathway problems (slide 16)
ye
study slide 18 and 19
ye
the spinothalamic tract mediates the DISCRIMINATORY aspects of pain –> e.g. dull, aching
ye
where does the anterolateral tract enter?
dorsal horn…??
anterolateral tract decussates right away–in spinal cord, to the anterolateral horn??
ye
study slide 24
ye
primary somatosensory functions in concious perception–it allows for two point discrimination, identification of objects by palpation (stereognosis); if someone cannot identify object by palpation (astereognis) = ISSUE WITH SOMATOSENSORY PATHWAY; also helps with identifying writing on skin
-requires both the use of the unimodal and multimodal association cortices
ye
describe the difference in roles of A-delta to C-type fibres
A-delta– functions in ACUTE (A = acute = A-delta); less discriminative sensation (sharp)
C fibre = CHRONIC = least discriminative sensations (dull pain, unmyelinated fibres)
describe gate control theory
–transmission of impulses from AFFERENTS (to spinal cord neurons) controlled by a GATE
–gate is influenced by relative amounts of activity –> dependent on large and small fibres
the SMALL fibre activity is nociceptive, and opens the gates = feel pain
the LARGE fibres are NON-nociceptive, and their activation CLOSES the gates–>blocks transmission of pain via inhibitory neurons in the substantia gelatinosa of the spinal cord
study slide 30
ye
pain vs nociception
pain = unpleasant sensory and emotional experience; does not need to be tied to a stimulus (may feel even if there is no tissue damage)
while nociception:
- sensory component of pathway, the activation of nociceptors; IS tied to a stimulus
- involved anterolateral pthway
define noxious
a type of stimuli that could cause tissue damage if exposure is prolonged
study slide 32
ye
