8/22 Organization of CNS - Glendinning Flashcards
spinal cord : basic features
3 major features
extends from foramen magnum to L1 vertebral body
receive inputs/send outputs through spinal nerves
- inputs from sensory receptors
- outputs to muscles, glands, smooth muscle
- long and short pathways
- spinal nerves comprised of
- dorsal root : sensory inputs/afferents
- ventral root : motor outputs/efferents
- grey matter [non-myelinated], white matter [myelinated]
spinal cord circuits
- reflex circuits : feedback inhibition or negative feedback
- basic motor circuits : postural and locomotor outputs
- sensory circuits
features of brainstem
transition between spinal cord and brain
- existing (entering) cranial nerves
- long pathways
ventral surface : most cranial nerves & corticospinal tract
medulla
visceral center
transition between spinal cord and brainstem
- 4 CN : IX, X, XI, XII
- receives info from taste structures, skin of head, heart/lungs, major blood vessels, digestive system
- several nuclei (grey matter)
- regulation of homeostasis (HR, resp rate, vasomotor tone, gastric secretions)
- related reflexes: vomiting, coughing, sneezing, swallowing, gagging
pons
large pathway to cerebellum
- 4 CN : V, VI, VII, VIII
- several nuclei
- balance, localizing sound, coordinating eye movement, facial expression
- reflexes : eye movements, jaw jerk
midbrain
top of brainstem
- 2 CN : III, IV
- several nuclei
- control orienting to sound, visual reflexes, motor control
- projections to cortex : substantia nigra, ventral tegmental area, source of dopamine projections to cortical areas
- influence movement and “reward”
reticular formation
reticular activating system
nuclei and neuronal circuits
- net-like appearance
- run through core of brainstem
- many nuclei - origins of projections to cortex or spinal cord
reticular activating system
- comprised of rostral projections from pons and midbrain (pontomesencephalic) directly into cortex or through the thalamus
- control attention, arousal, sleep, wakefulness
- includes several nt systems
caudal reticular formation
centers that control:
- resp rhythms
- bp
- digestion
- reflexes: facial expressions, gag, yawn, swallow, vomit
all of the above - medulla
movement: reticulospinal tracts
cerebellum
motor control and learning, posture, orientation, balance
69/100B neurons in brain
3 layered cortex
feedforward control of movement
- builds a model of a movement; detects/corrects deviations from the model
damage to cerebellum → ATAXIA (disordered movement)
thalamus
thalamocortical radiations : projections of thalamus to cortex
- sensory info → lateral nucleus
- info from reticular activating system → reticular and intralaminar nuclei
major relay station for all inputs to the cortex
ex. sensory (except olfaction), motor (ex. cerebellum), reticular formation, limbic system
*thalamus + hypothalamus + subthalamus = diencephalon
cerebral hemispheres
CORTEX
outer surface is grey matter : 6 layers of cells
white matter (forms the internal cortex)
- cortex to subcortical areas
- subcortical areas to cortex
- cortex to cortex
BASAL GANGLIA (putamen & caudate)
- habit formation
5 lobes and general functions
- frontal : planning, organizing, controlling behavior
- parietal : sensory perception of self & world
- temporal : auditory (superior), visual (middle), memory (medial) processing
- occipital : visual processing
- limbic : emotional processing/memory consolidation
primary cortex
first cortical receiving area for sensory info
last cortical area to project to brainstem for motor info
R controls/perceives L, and vice versa (crossing happens)
displays topographical organization (somato/retino/tonotropic arrangement) → represent localization of function
ex.
- primary somato-sensory cortex (post central gyrus - parietal lobe)
- primary motor cortex (pre central gyrus - frontal lobe)
- primary visual cortex (occipital lobe)
- primary auditory cortex (temporal lobe/Sylvian fissure)
corticospinal tract
spinothalamic tract
major motor pathway from cortex to spinal cord
- crosses in medulla → control of contralateral muscles
major sensory pathway from spinal cord to cortex
- also crosses in medulla
association cortex
carries out higher-order processing (perceptions, judgment, organization, calculations, language)
