The Brain Stem Flashcards
principle functions of the Brain Stem
relay/ conduit
integration & regulation of sensory info
cranial nerve origin & termination
rostral limit of brain stem
midbrain-diencephalon junction, below optic tracts
Cerebral Peduncle
links brainstem to thalamus/cortex
contains ascending/descending tracts
Crus Cerebri
location of motor tracts in cerebral peduncles
Tectum
superior/inferior colliculi - “roof” of midbrain
Tegmentum
“floor” of midbrain
contains red nucleus and substantia nigra
Red Nucleus
motor coordination and fine hand movement
origin of rubrospinal extra-pyramidal descending motor tract
Periaqueductal Gray
receives pain/temp info from lateral spinothalamic ascending tract
(gray matter in tegmentum)
Superior Cerebellar Peduncles
connects to midbrain
carries Anterior Spinocerebellar tracts
Middle Cerebellar Peduncles
connects to pons contralaterally
brain tracts
Inferior Cerebellar Peduncles
connects to medulla
posterior and cuneocerebellar tracts
Superior Colliculi
vision
Inferior Colliculi
sound
Gracile and Cuneate Fasciculus
Dorsal Columns of DCML ascending tract
synapse on second order neurons in medulla
decussate and forms medial lemniscus
Cerebral Peduncles (location)
ventral surface
only midbrain
Cerebellar peduncles
dorsal surface
all levels
Pyramids
pyramidal tracts descending from motor cortex
Olives
relay sensory and motor info
Inferior Olives
cerebellar motor learning
Pontine Nuclei function
allows unconscious modification of motor actions and error correction
Pontine Nuclei pathway
receives info from ipsilateral primary motor cortex –> relays info to contralateral cerebellum
Dorsal Column Medial Lemniscus - Cuneate Fasciculus
Discriminative touch, joint position, vibration, pressure of UPPER BODY
Dorsal Column Medial Lemniscus - Gracile Fasciculus
Discriminative touch, joint position, vibration, pressure of LOWER BODY
Decussation of DCML tracts
DCML tracts decussate in the medulla from the dorsal columns into the medial lemniscus to travel to thalamus
Spinothalamic tracts (lateral vs anterior)
lateral: pain & temp
anterior: light touch & pressure
Spinocerebellar tracts (3)
Posterior Spinocerebellar tract
Cuneocerebellar tract
Anterior Spinocerebellar tract
Posterior Spinocerebellar tract
lower body
stays ipsilateral
enters cerebellum through inferior cerebellar peduncles
Cuneocerebellar tract
upper body
stays ipsilateral
enters cerebellum through inferior cerebellar peduncles
Anterior Spinocerebellar tract
lower body
decussates twice
enters cerebellum through superior cerebellar peduncles
Descending Tracts (2)
Corticospinal tract
Reticulospinal tract
Reticular Formation function
modulates pain info from lateral spinothalamic tracts,
muscle tone, reflexes, motor control, and autonomic functions (eg respiration)
Ascending Reticular Activating System (RAS) function
functions in arousal/consciousness by sending continuous input to cortex
acts as filter to dampen repetitive, familiar or weak sensory input activity (about 99% of stimuli regarded as unimportant)
Reticular Formation location
located in tegmentum
axonal projections from cerebrum –> brainstem
includes RAS and descending pathways via reticulospinal tracts
Reticular Formation descending motor neurons
maintain skeletal muscle tone, balance and posture