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
muscle tone
passive resistance to stretch during non contractile state of a muscle
- continuous contraction of muscle even when you aren’t using them
- to test muscle tone- tell a person to relax their wrist and put it into dorsiflexion, and you’ll get resistance as you push it back. That’s due to normal muscle tone.
Diencephalon
4 parts
- thalamus (left and right lobes, the biggest structure of diencephalon)
- hypothalamus
- epithalamus
- subthalamus (2 lobes)
hypothalamus is connected to
pituitary stalk (connects to pituitary gland)
epithalamus includes your
pineal gland
3rd ventricle boundaries
between the 2 thalamic lobes
hypothalamus forms the floor
corpus collosum forms the roof
thalamus:
consists of ___ lobes
the space between these lobes is the ___ ____
80% of us have a thin strip of tissue that goes across the midline, through this space of the two lobes, and this tissue is called the
consists of 2 lobes
The space between the two thalamic lobes is the 3rd ventricle.
80% of us have a thin strip of tissue that goes across the midline, through this space of the two lobes, and this tissue is called the massa intermedia
each tier of the thalamus consists of
different nuclei (see definition on a different card)
3 functional clusters of thalamic nuclei
- relay
- diffuse
- association
Hypothalamus:
- integrating center for ___ ___ ___
- innervation to the ____
- controls ___ function
integrating center for autonomic nervous system
- innervation to the viscera
- controls visceral function (muscles like heart, longs , stomach)
hypothalamic sulcus
a small indentation that separates the hypothalamus from the thalamus. Above it is the thalamus, below it is the hypothalamus.
hypothalamic nuclei
anterior - initiates parasympathetic response
posterior- initiates a sympathetic response
the pituitary is hung by the floor of the hypothalamus by this
pituitary stalk and gland
optic chiasm-
where is it found?
what happens here?
What happens if you have a tumor here?
this is found right in front of your hypothalamus / pituitary
this is where your two optic nerves cross
if you have a tumor or something that compresses the chiasm, you’ll only see straight down the middle, you’ll lose some of your lateral field of vision (tunnel vision)
diaphragma sellae
Dura Mater that covers pituitary gland as it passes through the hypophyseal fossa
The pituitary stalk runs through it. If you take a brain out of a head, the diaphragm sellae prevents the pituitary from coming with it.
mammillary bodies
towards the posterior end of hypothalamus this is an external relay nucleus that can be seen. There is one on the right and one on the left
the pituitary gland has 3 parts
pars anterior
pars posterior
pars intermediate
these all secrete hormones
pars anterior stimulates:
- thyroid stimulating hormone (TSH)- which stimulates the thyroid gland
- adrenocorticotropic hormones (ACTH)- stimulates adrenal gland
- follicle stimulating hormone) FSH- stimulates maturation of the ovum in females, and testis in males
- Lutinizing hormone (LH) - causes ovulation in females, testosterone production in males
- growth hormone/ STH- promotes growth
- Prolactin (PRL)- causes lactation of the breast
epithalamus
lies posterior to thalamus
has pineal body and pineal gland
-secretes melatonin
-calcifies in adults
subthalamus:
has the ____ ____ (Luys) which refines ____ ____ and prevents _____ (poor movement, bad movement). A type of this is hemiballismus- which is movement of the limb at all times. It’s different than a cerebellum tremor because it is going at all times, whereas cerebellum issues happen when you try to do something
has the subthalamic nucleus (Luys), which refines voluntary movement and
prevents dyskinesia- (poor movement, bad movement). A type of dyskinsia is hemiballismus- a limb that is moving at all times. It’s different from cerebellum tremor because its going at all times, whereas cerebellum issues happen when you are trying to do something.
substantia nigra lesion
Lesion of substantia nigra of sub thalamus, causes Parkinson’s disease- tremor at rest
masked face- eyes droop, don’t show much expression
might have forward tilt when standing,
might not have an arm swing when walking
shuffling gate- short steps kind of shuffle along
can’t always get themselves started or stopped walking
muscle rigidity
neuro plate develops from
neuroectoderm
notochord eventually develops into
nucleus pulpous that we find in our intervertebral discs (the inner squishy portion)
The brainstem is the cephalic continuation of the ___ ___ ___ through the foramen magnum of the skull
cervical spinal cord
The brainstem and cerebellum are closely associated with each other and lie in the ___ ___ ___
posterior cranial fossa
The brainstem continues upward to the
diencephalon, or thalamus
The brainstem is connected to the cerebellum via the
three cerebellar peduncles (superior, middle, and inferior)
The cerebellar peduncles consist of
groups of axons which carry information back and forth between the cerebellum and brainstem.
the 4th ventricle of brain makes a diamond between which structures
cerebellum and pons
cerebral peduncles
run on either side of the midbrain
they are fibers of what is called the pyramidal system which is a motor system that we start to notice between 18 months and 2 years of age. So before that, babies rely on other motor pathways.
the basis pontis
a bulging ventral belly of the pons which is an extension of the cerebral peduncles fibers. Once a lot of fibers get to the pons, they collaterize off and cross to the other side where they’ll connect to a cerebellar peduncle. It’s this crossing over that creates the bulge of the basis pontis. The ones that don’t cross over goto the medulla.
Pyramidal Decussation
crossing over of 85% of corticospinal fibers towards the bottom of the pyramids in the medulla
If someone gets damage to their right side of the brain, which side will this effect?
their left side because of the fibers crossing over
the olive of the medulla
used more as just a landmark. It lies dorsolaterally to the pyramids
The motor fibers that originally cross over in the medulla (the 85%) go
all the way to the bottom of the spinal cord
what happens to the the minority of the fibers that don’t cross over until the cervical spinal cord (where they do cross over)
they end. They run out.
the pyramidal motor pathway controls
fine motor skills (i.e, play an instrument or type)
the anterior and posterior cerebellum are separated by
the primary fissure
why is the posterior cerebellum so big?
it gets it’s input primarily from the cerebral cortex.
what does the vermis of the cerebellum get most of it’s input from?
the vestibular system because it works hand and hand with the inner ear.
the anterior lobe of the cerebellum receives input from:
from spine
Posterior Lobe: receives input from
cerebral cortex
the vermis is formed… and it’s function is for
formed first. Equilibrium and balance.
Tonsils
squeeze brainstem during swelling causing circulation to brainstem to stop.
past pointing
symptom of cerebellum lesion
poor ability to point at something on themselves or out in space
dysmetria
symptom of cerebellum lesion
poor ability to gage distance- see this when past pointing
ascending portion of reticular formation - (aka reticular activating system)-
these fibers go up to cerebral cortex and what they do is waxing and wayning. They regulate level of consciousness and awareness. When RAS has a lot of activity, your cerebral cortex is aroused. Low activity you might actually goto sleep.
When you have a troph- cerebral cortex = unstimulated and you are likely asleep
When you have a peak in cerebral cortex = you likely are awake
the descending portion of reticular formation
drives respiration, integrates cardiovascular reflexes and maintains muscle tone
the corpus collosum allows
one cerebral hemisphere to communicate with another hemisphere
Dysmetria
a cerebellum lesion resulting in lack of coordination by overshoot or undershot of limb
-past pointing
internal medullary lamina
heavily militated fibers that divides each thalamus into three tiers (zones):
an anterior tier
a medial tier
a lateral tier
thalamus nuclei
clusters of neurons with axons projecting to a common destination (i.e. cerebral cortex) & have a common function.
Lateral geniculate body of thalamus is for
for vision
medial geniculate body of thalamus
for hearing/ auditory
functional cluster of thalamus : relay
carry general or special sensation from incoming systems to the cerebral cortex; most specific
ex. lateral geniculate body- vision
functional cluster of thalamus : diffuse.
Carry information from and to?
Who would struggle if this isn’t working
carry information from the ascending reticular formation to the relay nuclei (and hence to cerebral cortex); help to screen out excess info. ADD!
functional cluster of thalamus : association
interconnect various portions of the cerebral cortex with each other. Helps you to know what incoming info is. 90% of nuclei are association nuclei; performs independently of the other two. (helps us understand how hot was it? how cold was it etc)
autonomic nervous system has two parts
has a sympathetic (fight and flight) and parasympathetic (feed & relax)
pars posterior pituitary gland controls
- oxytocin- facilitates labor in females
2. vasopressin (ADH)- inhibits urine production by the kidneys with reduced urine volume (retain water)
pars intermedia pituitary gland controls
melanocyte stimulating hormone (MSH)- maintains normal skin pigmentation
hemiballismus
sub thalamus issue which is movement of the limb at all times
