Week 5 Learning Issues Part 2 Flashcards
3 major categories of somatosensory receptors
- Mechanoreceptors
- Proprioceptors
- Nociceptors/ Thermoceptors
Major CNS destinations for somatosensory information
- Local Reflexes
- Cerebellum
- Brainstem
- Forebrain
Local Reflexes at level of
brainstem and spinal cord
local reflexes provide mechanism for
quick, stereotyped responses, to primary afferent input
Cerebellum receives
all types of somatosensory input, particularly proprioceptive input, via spinocerebellar pathways
cerebellum processes
sensory and motor information to regulate on-going motor programs
processing in cerebellum is
subconscious
brainstem circuitry for
generating/ controlling gait depends on somatosensory information
brainstem neuromodulatory systems
- include ascending reticular activating system (ARAS)
and monoaime pathways - activity in the systems controlled in part by incoming sensory info
brainstem neuromodulatry systems influence activity in many other areas of the brain including
brainstem, hypothalamus, thalamus, limbic structures, cerebellum, and neocortex
neuromodulatory systems play a role in
general activation of the brain (arousal), affect, emotion, motivation, and modulation in pain pathway
forebrain
diencephalon (thalamus and hypothalamus), Basal Nuclei, Cerebral Cortex, and Limbic Structures
Somatosensory pathways to forebrain
- Specific pathways
2. Non specific pathways
Specific pathways
- relay information such that brain can interpret location, sub modality, intensity, and quality of stimulus
- these pathways utilize somatosensory relay nuclei in lateral thalamus to reach primary somatosensory area of neocortex in parietal lobe
what are the specific somatosensory pathways to forebrain
- DC-ML
- Spinocervicothalmic
- Direct Spinothalamic Pathways
Non-specific pathways
- relay information about the stimulus location, submodality, and quality, other than perhaps intensity, is less faithfully relayed
what is the non-specific pathway
indirect spinothalamic pathway
where does non-specific pathway synapse
- synapses in a number of nuclei in the reticular formation of cd brainstem as well as in intralaminar nuclei of medial thalamus and terminates diffusely throughout the cerebral cortex, basal nuclei, and hypothalamus
specific information is processed in
forebrain structures for conscious awareness, memory, learning, decision making, motor planning, and other complex behaviors
non-specific sensory information
plays an important role in regulating emotion, affect, motivation, and aspects of autonomic fx by influencing activity in reticular formation, intralaminar nuclei, hypothalamus, cerebral cortex, and limbic pathways
visceral afferents
- not part of somatosensory system
- sensory info from viscera utilized in CNS in many of same ways somatosensory info is used
visceral afferents regulate
spinal cord, brainstem reflexes, influence activity in neuromodulatory pathways, may be consciously perceived, and afferent complex behaviors via pathways involving hypothalamus cortex and limbic structures
signal from visceral receptors
often not consciously perceived; involved in visceral reflexes and homeostatic regulations
info from visceral receptors
relayed to CNS predominately via Vagus Nerve to the Nucleus of the Solitary Tract or to sacral spinal cord via pelvic nerves
conscious perception of pain or discomfort
can be from distention of viscera and stimulation of some visceral chemoreceptors -> conscious perception of pain
distention of bladder and rectum
can be consciously perceived; visceral afferents
referred pain
CNS less accustomed to interpreting visceral pain than somatic pain, stimulation of visceral nociceptors can be misinterpreted by CNS as somatic pain and then pain is perceived to arise in regions of muscle or skin innervated by same spinal cord segments as stimulated visceral tissue (ex pain in arm during heart attack)
DC-ML
Dorsal Column- Medial Lemniscal Pathway
DC-ML mediates
conscious perception of touch and pressure from mechanoreceptors and cortical processing of body position via proprioceptors
collaterals from DC-ML pathway
terminate in brainstem where provide input for motor coordination fo gait and other brainstem controlled motor function
DC-ML pathway pathway
- primary afferent axons ascend spinal cord in dorsal funiculus (Fasciculus Gracilis and Fasciculus Cuneatus)
- Synapse in cd medulla on Nucleus Gracilis or Nucleus Cuneatus
- Axons from projection neurons in Nucleus Gracilis or Nucleus Cuneatus decussate in cd medulla and ascend through brainstem in md leminiscus
- Projection neurons synapse in somatosensory thalamic relay nucleus
- Axons from thalamus project to somatosensory cortical areas in parietal lobe
fasiculus gracullis
carry axons from cd half of body
fasiculus cuneatus
carry axons from rostral half of body
Spinocerebellar pathways
carry proprioceptive and other SA information from spinal cord to ipsilateral cerebellum
cuneocerebellar pathway
spinocerebellar pathways; carries info from thoracic limb
dorsal spinocerebellar pathway
spinocerebellar pathways; carries information from pelvic limb
axons of spinocerebellar pathways travel in
dorsal lateral and dorsal funiculi of spinal cord
spinocerebellar pathways reach cerebellum via
cd cerebellar peduncle
spinocerebellar pathways may be disrupted by lesions impacting
- dorsal lateral funiclus
- cd medulla
- cd cerebellar peduncle