Anatomy Test #3 Lecture #2 Flashcards
The CNS
INCLUDES BRAIN AND SPINAL CORD
PNS
nerve axon bundles and ganglia (a neuron cell body that is aggregated into a little knot)
Rostral
toward the front of the head
cephalic
towards the head
caudal
towards the tail
ipsilateral
same side
contralateral
opposite side
CNS forms from
the embryonic outer covering called ECTODERM
-neural and epithelial(skin) come from ectoderm
CNS and cardiovascular system are
the first two systems to develop in an embryo
When does the CNS develop
within the first 3 weeks following conception
how does the CNS develop?
Week 1- it begins as a neural plate (a thickening of ectoderm)
Week 2- neural plate invaginates into a neural groove
Week 3-
A. neural groove closes to form neural tube. Epidermis covers the neural tube.
B. Neural crest cells come off of the neural tube and form the dorsal root ganglia.
C. Notochord forms in the nucleus pulposus
development of the brain happens when?
in the 4th week
3 primary brain vesicles are formed from the neural tube
(listed cephalad to caudal)
- forebrain (aka prosencephalon)
- midbrain (aka mesencephalon)
- hindbrain (aka rhombencephalon)
2nd brain vesicles
They have grown since from primary vesicles
forebrain :
telencephalon
diencephalon
midbrain:
mesencephalon
hindbrain:
metencephalon
myelencephelon
telencephalon turns into
cerebral cortex
dincephalon develops into the
thalamus and hypothalamus
mesoncephalon turns into the
midbrain
metencephalon turns into the
pons and cerebellum
myelencephalon turns into the
medulla
can you live without your brainstem?
NO! Especially not without your medulla
parts of the brainstem
midbrain
pons
medulla
where is the cerebellum
posterior to the brainstem
brainstem- corpora quadrigeminae
the 4 colliculi of the midbrain-
2 superior colliculi
2 inferior colliculi
this can also be called the tectum. The 4 colliculi are a dorsal covering for the midbrain. They are reflex centers for vision and audition (auditory)
2 superior colliculi
orientation for visual stimuli
if something flies by in your visual path you lock onto it and you follow it
2 inferior colliculi
auditory startle reflex - loud nose you tern and look at it
cerebellum peduncle
paired superior, middle and inferior peduncles
carry information between the cerebellum and the brainstem
medulla dorsal columns
carry tactile sensation to the brain:
- kinesthetic sense- knowing where your limbs are without looking at them
- vibratory sense- being able to detect a vibrating object
- 2 point discrimination - be able to tell two different points when touched on body
- stereognosis- can tell the shape of something without looking at it
pons
the 4th ventricle
the top half of a diamond shaped depression overlays the brainstem
medulla- shape (in terms of width), what do it’s dorsal columns do? and what is it part of?
-widens rostrally
-dorsal columns carry sensory information upwards
-the 4th ventricle
the bottom half of diamond shaped depression that overlays the brainstem
cerebellum has 3 hemispheres
- anterior lobe
- posterior lobe (much larger than anterior lobe)
- vermis- the central region which can be separated into a superior and inferior portion
folia
cerebellar folds
parts of vermis
uvula, nodule and flocculi
Note the cerebellum has tonsils
they are part of posterior lobe. When pressure builds up in the brain, the brain will begin to push down towards the foramen magnum. The brainstem, cerebellum and the tonsils will be pushed down, and the tonsils will start to push into the brain stem. This will reduce the persons ability to breath and is called a tonsil herniation.
function of cerebellum
- it coordinates muscular activity- it makes muscles and muscle fibers work together and synergistically
- IT ALSO CONTROLS posture and equilibrium
ataxia
a muscular control problem that relates to the cerebellum
- it leads to you not being able to coordinate movements
- this results in jerky, unsteady to and fro movements of the trunk
- unsteady walking style - usually spread feet wide
truncal vs gait ataxia
Truncal – difficulty in controlling the trunk and holding the trunk upright.
Gait – difficulty in walking and appears to fall toward the side of the lesion.
dysnergia
cerebellum lesion - inability to coordinate voluntary muscles movements.
-intention tremor
intention tremor
a symptom of cerebellum lesion
-the tremer manifests itself when they’re trying to do something (i.e trying to reach for something)
Dysdiadochokinsea
a symptom of a cerebellar lesion
inability to perform a repetitive task (turn hand over and up again and again)
brainstem reticular formation
two neurons that run laterally in brainstem that run to medulla/midbrain (sometimes even to thalamus) and all the way down again
There are 2 directions that it can flow:
- ascending portion
- descending portion