Download Addendum to brainstem

3/20/16
The Brain Stem
The brain stem is the
extension from thalamus
towards the spinal cord. It
is a pathway for ascending
and descending tracts.
It also is an area containing
specific "primitive" ( but
crucial) reflex centers as
well as nuclei that form the
basis of our cranial nerves.
Elements of the brain stem
are the Midbrain, Pons and
Medulla oblongata.
1
The Brain Stem
2
1
3/20/16
The Brain Stem
Midbrain or Mesenencephalon
•  Peduncles are tracts , bundles
of axons, that send information
from either cerebrum to the
spinal cord (and back again) or
relay information to and from
the cerebellum.
•  on anterior side are the
cerebral peduncles •  on posterior side are the
superior cerebellar peduncles
3
The Brain Stem
Midbrain
•  Dorsal area of the midbrain (also
called the tectum) contains nuclei
within the white matter . They are
collectively named the corpora
quadrigemina
•  Superior colliculi : reflex center
for movement of eyes, neck, head
to visual stimuli •  Inferior colliculi : reflex center for
head trunk movement in response
to auditory stimuli 4
2
3/20/16
The Brain Stem
Midbrain
•  The Floor of the Midbrain
(inner area) contains cerebral
aqueduct and several internal
gray matter nuclei with
specific functions.
•  Red nuclei : subconscious
control of upper limb and
background muscle tone
•  Substantia nigra : regulates
activity of basal nuclei
•  Reticular formation: helps to
filter in-coming stimuli and
maintains consciousness. Present
along all brainstem areas.
5
The Brain Stem
Pons
•  Anterior region contains mostly
longitudinal conduction tracts for
motor activities on ventral side
(extension of the cerebral
peduncles)
•  Dorsal side contain lateral tracts
that connect to cerebellum :
middle cerebellar peduncles •  Internally are the nuclei of
Apneustic and pneumotaxic center
(aid in control of respiration
center located in Medulla) and
RAS
6
3
3/20/16
The Brain Stem
Pons
7
The Brain Stem
Medulla oblongata
•  Inferior part of brain stem and blends
into the spinal cord •  Ventral side contains the two large
extension of the cerebral peduncles,
descending from motor cortex. •  They are also called the pyramids. •  Pyramids cross over to opposite side
right above the Spinal Cord. This is
called the 'decussation of pyramids' .
8
4
3/20/16
The Brain Stem
Within the Medulla are several
important regions of gray matter
reflex centers •  Cardiovascular center : regulates
force and rate of heartbeat, diameter
of blood vessels (relates to origin of
Vagus nerve) •  A Respiratory center that adjust
basic rhythm of breathing •  Extensions of Reticular activating
Center (RAS)
•  Olivary nuclei : relay motor
information to the cerebellum
•  Other centers for swallowing &
vomiting (relates to CN IX), hiccups,
coughing, sneezing.
9
The Brain Stem
•  Dorsal side of the medulla
contains the Inferior cerebellar
peduncles: •  It connects medulla to
cerebellum and relays
information from motor cortex
to cerebellum via the olivary
nuclei
10
5