Ch. 27 The Pons Flashcards
The pons is the bridge between
the midbrain and the medulla
the brainstem and the cerebellum
anterior/ventral half (or base) of the pons is full of
pontine nuclei
pontine nuclei
-anterior half of pons (base)
-share pons with axons from myelinated corticosponal tracts
-receive input from the motor cortex of the cerebrum about its intentions, on the same side (ipsilateral)
-signal intentions of the moo cortex of the cerebrum to the contralateral cerebellar cortex
(so, receive from same side cerebrum, project to opposite side in cerebellum)
retrotrapezoid nucleus
- detects CO2
- lies on the surface of the pons base anterior to the facial nucleus
- superior to the boundary of pons and medulla
- most caudal part of pons
motor cortex of the cerebrum
-axons synapse on neurons from the ipsilateral pontine nuclei
cerebellar cortex
receive axons from the contralateral pontine nucleus
the left cerebellar cortex
receive information from the right cerebral cortex from the right pontine nuclei of the bae of the pons
middle cerebellar peduncle
made up of axons from the neurons (pontine nuclei) on the opposite side of the base of the pons
superior cerebellar peduncle
-receives information from the same side of cerebellum
-projects to the opposite side of forebrain
-leaves cerebellum dorsal to the 4th ventricle
-remain in the lateral side of roof of the 4th ventricle until the lower midbrain
-crosses under the cerebral aqueduct to reach the
opposite side of forebrain
-cross each other ventral to the cerebral aqueduct in lower midbrain
cerebellum is _ to the 4th ventricle
dorsal (posterior)
crossing (decussation) of the superior cerebellar peduncles is prominent feature in the
lower midbrain
the ventral half of the pons is__
the dorsal half go the pons is the __
base; tegmentum
tegmentum of the pons
between the base and the 4th ventricle
the motor nucleus of trigeminal nerve
- dorsolateral corner of the tegemtnum of the pons
- present only at the mid pontine level
- decend from midpontine level in th lateral part of th tegmentum of the pons
- ventral to the lateral vestibular nucleus in the tegmentum of the lower (caudal) pons
mesencephalic tract of trigeminal
- ventral to superior cerebellar peduncle
- extends upward (rostrad) from the mid pontine level
- dorsal and lateral to the nucleus ceruleus
nucleus ceruleus
- ventral and medial to the mesencephalic tract
- essential alertness center in the dorsal tegmentum of the middle and upper pons
- neurons project to many other brain centers to stay awake
- projections release norepinephrine in several forebrain nuclei to increase alertness
- principle source of norepinephrine in CNS
medial leminiscus
- thick vehicle ribbon of white matter in the medulla, becomes thick ribbon of white matter in pons
- forms ventral (anterior) border of the tegmentum in pons
- thin white matter tract called ventral trigeminothalamic on the dorsal side
ventral trigeminothalamic tract
- thin ribbon of white matter in the dorsal side of medial leminiscus
- carries epicritc information from opposite side of the face
- recieves info from face from the principle sensory nucleus of trigeminal on the opposite side to the thalamus
- not present below mid pontine level (not in lower pons)
- ventral to the central tegmental tract
central tegmental tract
- dorsal to the ventral trigeminothalamic tract
- carries info from the red nucleus to tine inferior olivary nucleus
nucleus of the lateral leminiscus
- relay center for hearing
- lateral side of the central segmental tract
- at mid pontine level
- lateral leminiscus carries auditory information upward from superior olivary nucleus to the inferior colliculus on the lateral side of the tegmentum of the pons
- on lateral side of the central tegmental tract
- medial to the anterolateral system in the pons
central tegmental tract is dorsal to
medial leminiscus
lateral leminuscus is dorsolateral to
medial leminsicus
pontine reticular formation
- network of neurons and axons occupying most of the tegmentum of the pons
- some neurons have long axons that form the medial reticulospinal tract
- neurons project through medial reticulospinal tracts on the same side
medial reticulospinal tract
- synapse on internuncial neurons that controls lower motor neurons for extensors of the lower extremity
- projection for pontine reticular formation on same side
