1. Development/Anatomy of NS

Question 1

CNS: bathed in fluid (____) and protected by Meninges and bone

PNS:
____ pairs of cranial nerves

____ pairs of spinal nerves

How do we organize the entire NS?
• it is formed by 2 interconnected parts
◦ CNS which consists of brain and spinal cord, which extends partway to the vertebral column
◦ PNS are 12 pairs of cranial nerves and 31 pairs of spinal nerves
‣ All spinal nerves are fundamentally similar, in that every branch of every spinal nerve is ____
‣ Any time you see a branch of a spinal nerve, regardless of where it is going or what its doing, it s got
BOTH motor and sensory fibers
‣ Cranial nerves are annoying bec they are all special cases; some of them will be ____, some are entirely
____ and some of them are entirely ____
‣ We are going to go over how the cranial nerves are organized in the brain stem

Answer 1

CSF
12
31

mixed
mixed
motor
sensory

Question 2

• Note that the entire CNS has the consistency of a jellyfish; its basically semi-solid mass, with very little if any ____ for support because fundamentally its just nerve cells and variety of glial cells
◦ This jelly fish needs to be heavily protected from trauma
◦ the bulk of the brain is protected by the inner-connected bones that make up the skull, but the spinal cord is also comparably protected by the bones that make up the vertebral column
• Inside the skull and the vertebral column are 3 layers of connective tissue that form the meninges:
◦ outermost and thickest layer (refer to label above) –> called ____ (which literally means tough
mother)
◦ Inside that is a delicate ____ layer
◦ an intimately investing all parts of the brain is a 3rd layer called ____
• Note that her entire jellyfish of the brain floats in a fluid bath of cerebrospinal fluid CSF in the ____
• To reiterate –> Some of the bony coverage, meningeal coverage and the fluid bath protect the brain from trauma

Answer 2

connective tissue
dura matter
arachnoid
pia
subarachnoid space

Question 3

The entire nervous system forms from ____, the same germ layer that forms skin.

____ forms CNS, ____ forms certain neurons in cranial and spinal nerves

Open neural tube defects result when tube does not close.

• Now how do we make a brain or where does the entire NS develop?
◦ Answer: it develops from a single primary germ layer known as ectoderm ◦ Early embryology establishes 3 overlapping germ layers, known as
‣ Ectoderm (in blue)
‣ Mesoderm (in red)
‣ Endoderm (in yellow)
◦ So then this initial process where these 3 germ layers are established is in the future ____body wall of the developing embryo
• Note that the entire NS (CNS and PNS) is formed from ____, same germ layer on the surface of the body the will give rise to skin, the largest organ in the body

Answer 3

ectoderm
neural tube
neural crest

dorsal midline
ectoderm

Question 4

• So where does neurlation take place?
◦ in the future ____ parallel to where the vertebral column develops
◦ basically the major event of neurlation is when this midline ectoderm thickens and becomes ____ (pic a–
>b)
◦ ..and through various inductive processes, the neural-ectoderm separates itself from overlying ectoderm and fuses and
forms a completely hollow ____
◦ this neural tube will form the entire ____ (brain and spinal cord)
• Note that during the process of neurlation, the neural tube not only closes, but it also separates itself from the overlying ectoderm and the ectoderm grows over the site where neurlation took place
◦ So there is no ____ in post-natal life that the entire brain developed from the same germ layer that gave rise to skin
• At the same time as the neural tube is developing, the ____ is developing on the outside at the edges of each the neural fold…
◦ when the neural tube closes, the neural crest cells also separates from the overlying ectoderm and occupy this original developmental position, ____ to the developing neural tube (see pic D)

Neural tube –> forms CNS
• Neural crest –> forms certain but not all neurons in spinal and cranial nerves
…but then what happens when there is severe defects in neurlation, known as open neural tube defects –> occur when one or other end of neural tube fails to close
◦ we are not gonna document the diff forms of these defects ◦ but just know that they are not compatible with life

Answer 4

dorsal midline
neuro-ectoderm
neural tube
CNS
evidence
neural crest
dorsal-lateral

Question 5

Neural Tube and Neural Crest

• Refers to pic on right
◦ Neural tube completely closed
◦ you can see the purple neural crest outside the neural tube in this dorsal-lateral position
◦ the ____ develops over the site where neurlation took place
• Following its formation, the neural tube induces ____ to grow around and induces the formation of bones of the skull and induces the formation of vertebra of the neural arch, to protect it from trauma in the subarachnoid space
• Note that even at its earliest formation, the presumptive neurons in the neural tube acquire a functional ____
◦ All the neurons that develop in the dorsal half of the neural tube closest to the dorsal midline –> will develop
into ____ plate –> develop into ____ neurons (neurons that respond sensory input)
◦ By contrast, all the neurons that develop in the ventral half lof the neural tube –> develop in the ____ plate
–> form ____ neurons (neurons that enervate skeletal muscles)
• To recap: Post-natal spinal cord replicates this pattern by having sensory neurons dorsally positioned and motor neurons ventrally positioned

Answer 5

ectoderm
bone
polarity

alar
sensory

ventral
motor

Question 6

Neural Tube: further development. Tube remains hollowed by ventricles and canals that connect them. They contain CSF.

• On left side: is a section thru our hollow neural tube –> developing into CNS maintains its hallow caliber throughout life
(your entire CNS is still hallow by ventricles and channels that connect these ventricles)
• Note that cranial end of the neural tube undergoes significant elaborations by forming initially 3 primary brain vesicles, known as:
‣ ____
‣ ____
‣ ____
◦ these 3 primary vesicles undergo additional elaborations to form 5 secondary vesicles
‣ read labels below
‣ ____ does not differentiate
• Note that the ____ end of the neural tube does not change much

Answer 6

forebrain
midbrain
hindbrain
mesencephalon
caudal

Question 7

• Recognize that despite the significant elaboration of the cranial end of the neural tube, it still maintains it ____ caliber
◦ by being hallowed out by neural canal remnants that form ventricles dilated space or channels that interconnect all of these ventricles and include a narrow central canal that extends all the way the length of the spinal cord
• whats significant about these ventricles ?
◦ they contain specialized ____ epithelial cells that secretes cerebral spinal fluid into their lumen and the
secreted fluid is a circulated fluid –> finds a way to exit from some opening, specifically from the ____ ventricle, and circulate around the brain in the ____ space and drain back into the ____ system
• Note that we are going concentrate in terms of organization on a number of these parts of the neural tube, specifically regions of these secondary brain vesicles that form the 3 parts of the brains stem cause they would be home for most of our cranial nerves

Answer 7

hollow
choroidal plexus
fourth
subarachnoid
venous

Question 8

Diencephalon parts
Thalamus: relays ____ information to cortex
Hypothalamus: controls ____ function

Cerebellum: ____

Brainstem: ____ nerves

So what are the parts of the post-natal brain stem?
◦ the largest component of the brain gives rise to a pair of ____ cortical areas
◦ cerebral hemispheres are formed by a series folds of cortical tissues, known as the ____
◦ Those gyri are separated by little indentations called the ____
‣ He did not show these on the diagram, but I looked them up so see labels of gyrus and sulcus below
•
◦ Green area –> diencephalon; has 2 major components
•‣ thalamus –> means inner chamber; relay all sensory and motor information to specific areas of the cerebral hemispheres
‣ hypothalamus –> job is to control autonomic and endocrine function ‣ SO now how does it do that?
• through the help of the ____ gland (not shown on pic below), which is suspended directly below the hypothalamus allowing the hypothalamus to control all pituitary secretions

Answer 8

motor and sensory
endocrine and autonomic

coordination

cranial

cerebral hemisphere
gyrus
sulcus

pituitary

Question 9

•
• The most important area of the brain for todays discussion is the brainstem, which has 3 parts:
◦ ____ –> directly continuous with the ____
◦ ____
◦ ____
Note that right above the pons is a little brain, or the ____ –> promote smooth execution of skeletal muscle contraction; called a motor coordination center; ex: walking, writing, etc..

Answer 9

midbrain
pons
medulla
cerebellum

Question 10

• Again, we know that the entire nervous system is derived from neural ectoderm, a subset of the surface ectoderm –> it forms the neural tube, which gives rise to the CNS
◦ but note that is a direct outgrowth pf the neural tube –> the optic nerve is NOT A ____!! because
◦ it is never ____ of the brain; invested by the same 3 meningeal layers as the entire CNS
◦ we can also see other parts of the CNS: pineal gland, neurohypophysis (part of the pituitary), astrocytes (supporting cells of CNS), Oligodendrocytes (glial cells that make myelin for functionally- specific bundles of axons that are running up or down of the CNS called tracts or fasciculi)
‣ ____ make ALL of myelin for neural systems parts as: tracts, fasciculi, and axons of the optic nerve

Answer 10

nerve
outside
oligodendrocytes

Question 11

Derived from Neural Crest:
All primary ____ neurons
in ____ nerves ex optic nerve, All ____ neurons

Outgrowth of Neural tube:
All ____ axons in CN’s andSN’s and all ____axons

whats derived from neural crest?
◦ gives rise to certain neurons that are found outside the CNS in cranial and spinal nerves
‣ what kind of neurons? –> virtually all primary sensory that are responding to a receptor stimulus somewhere in a skin or muscle are derived from neural crest, except for ____ NERVE
‣ other kind of neurons? –> post-ganglionic autonomic neurons
Bottom line is –> any neuron that has its cell body in a ____ has to be derived from neural crest bec ganglia by definition are collection of functionally-specific neurons found outside the brain
All ganglia are either sensory ganglia or post-ganglionic autonomic ganglia –> all are derived from neural crest
◦ (a) Sensory ganglia -> are simply containing sensory cell bodies of sensory components that are carrying sensory information into the spinal cord or into the brain stem …
‣ so there are NO ____ in a sensory ganglion; tend to be ____ ; found outside the CNS

Answer 11

sensory
cranial and spinal
postganglionic autonomic

skeletal motor
preganglionic autonomic

optic
ganglion
synapses
unipolar

Question 12

◦ (b) autonomic ganglia –> are ____ in function; are sites of ____ bec autonomic ganglia are receiving a synapse from a pre-ganglionic neuron inside the brain and it gives rise to axon of a post- ganglionic autonomic neuron that enervates glands, smooth muscles and heart

Note that neural crest cells migrate great distances from their original developmental location:
◦ into basal layers of skin –> form ____
◦ ____ cells –> make all myelin of any nerve except of optic nerve
◦ 2 layers of the ____
◦ virtually all of the pharyngeal arches
◦ odontoblasts
◦ ____cels
◦ play sign role in ____ development; faulty neural crest leads to many of the common congenital malformation of
heart

Answer 12

motor
synapse

melanocytes
schwann
meninges
parafollicular C
heart

Question 13

• What kind of neurons in peripheral nerves are not derived from neural crest?
• > all of the ____ neurons that innervate skeletal muscles everywhere, does not matter if a cranial or spinal nerve

‣ ..this is because the cell bodies of these neurons is found inside the ____ somewhere –> send their axons out in the peripheral nerves to enervate the skeletal muscles somewhere
◦ other kind of neuron that we will find in peripheral nerves is a pre-ganglionic autonomic axon
‣ outgrowth of the ____ as wel, bec their cell bodies are found somewhere inside the neural tube

• we can say that certain neurons in cranial and spinal nerves are derived from neural crest but other kind of neurons where we only find axons in peripheral nerves are not derived from neural crest

Answer 13

skeletal motor
brain
neural tube

Question 14

Terminology

• Nucleus -> a collection of functionally-specific neuron cell bodies in the ____
• Ganglion –> a functionally specific collection of neuron cell bodies found outside the ____; derived from ____; either sensory or autonomic ganglion
• Tract (read all the other synonym names) –> group of functionally specific CNS axons going from one place to another in the brain or spinal cord; might be going up, down, side-by-side, cross the midline, going from one side to the other
• Nerve –> a bunch of axons that are projecting from the CNS to PNS or in the other direction; are what we found in cranial or spinal nerves;
◦ myelinated sensory axons, or myelinated motor axons; all tract axons are myelinated by ____
◦ all axons in the peripheral nerves except for the optic nerves are myelinated by ____
• Afferent –> ____ a defined source; used to mean ____, in a nerve carry sensory axons from a receptor somewhere into the brain
• Efferent –> synod w/ motor; skeletal ____ axons are axons that leave the brain to enervate skeletal/ smooth muscles
• Somatic –> means whats in the body wall: skin, bones, cartilage, and muscle; gets both ____ innervation
• Visceral –> means organ systems in the body cavities; that might be cardiovascular, GI, respiratory, renal, reproductive, ect..; all of the organ structures are receiving ____ enervation, largely autonomic and also visceral structures send ____ info back to CNS

Answer 14

brain or spinal cord
CNS
neural crest

oligodendrocytes
schwann cells
toward
sensory
motor
motor and sensory
motor
sensory

Question 15

What glial cells make myelin?

Oligodendrocytes: Myelinate up to 50 segments of 50
different axons in the ____

Multiple sclerosis: Autoimmune destruction of CNS myelin; affects tracts and the ____ nerve

Schwann cells: Myelinate a single segment of one axon
in the ____

Guillain-Barre Syndrome: Autoimmune destruction
of ____ Myelin; affects Nerves except the ____ nerve

• Without going in any details, glial cells that make myelin have clinical significance due to the degree of autoimmune reactions that destroy the myelin that is formed by them
◦ The most common autoimmune demyelinating disease in CNS –> MULTIPLE SCLEROSIS
‣ myelin inflammation rxns that affect ____ axons that are running up and down of the brain
• Schwann cells are much more restricted in how much myelin they form- myelinate a single segment of a single segment, while oligodendrocytes can myelinate up to 50 segments of 50 axons
◦ a common autoimmune destruction of PNS myelin is known as Guillain-Barre Syndrome–
‣ mostly affects ____ nerves, and to a lesser degree spinal nerves but certainly the ____ nerve will not be
affected if there is an autoimmune destruction of Schwann cells

Answer 15

CNS
optic
PNS
PNS
optic

sensory or motor
cranial
optic

Question 16

Neural Systems:
How does muscle contract voluntarily? Need ____ neurons: an upper and a lower motor neuron

UMN: ____ ToLMN
UMN axons in a ____

LMN:
____ to Innervated muscle
LMN axons ina
____ nerve

Answer 16

two
contralateral
tract

ipsilateral
spinal

Question 17

• Lets look at the LMN first:
◦ will exit all sides of the spinal cord and basically is found in a spinal nerve
◦ this is an example of a motor axon whose ____ is inside the brain whose axon goes out to the ____ and makes the skeletal muscle contracts
◦ LMN is always the neuron in a nerve that s leaving the brain to enervate a skeletal muscle directly
• Note that in this example we are simply generating contractions of the skeletal muscle on the left side of the body
◦ Also all parts of the LMN (cell body and axons) are ipsilateral to the innervated muscle and are found on the left side of the spinal cord ***
◦ since we have 31 pairs of spinal nerves so we have ____ pairs of LMNs that generating voluntary contractions on the ipsilateral side

Answer 17

cell body
neuromuscular junction
31

Question 18

•
•
Now where do we find the cell bodies of UMNs?
◦ answer: in a region way up in the cerebral hemisphere, called as ____
◦ note that the cell bodies of the UMNs are on the opposite side of the brain from the LMNs that they enervate; meaning
that they are contralateral to the LMNs that they enervate
Summary of this slide: In order to generate a voluntary contraction of any muscle on the left side of the body, we have to activate UMNs in the right motor cortex and LMNs in the left side of the spinal cord

Answer 18

motor cortex

Question 19

How do the axons of the UMNs get from motor cortex to the spinal cord?
◦ answer: they run in a tract of axons called ____
◦ these axons leave the motor cortex to go all the way down to the brainstem through finding their place to cross from the right side to the left side
‣ where they cross is very close to the brainstem-spinal cord junction called the
____ (an oblique crossing; synonym to corticospinal tract)
‣ (Follow the yellow arrow pathway in the above pic) Corticospinal tract –> carries axons of the UMNs out of motor cortex, cross the midline and run the entire length of spinal cord and synapse on LMNs, depending on where I want to generate a voluntary contraction

Now what kind of neurons do we find in cranial nerves?
◦ Here in this pathway, we were talking about spinal nerves –> all spinal nerves LMNs are receiving a contralateral UMN enervation
◦ Answer is more ____ bec many cranial nerves are also innervating skeletal muscles directly (eyes muscles, jaw muscles, pharyngeal, palatal muscles contain LMNs)
◦ Virtually, all cranial nerves are enervating ____ muscles

How many neurons do you think ou need to generate a voluntary contraction of a cranial nerve muscle?
◦ ANSWER is ____ neurons; need the cortex to tell you when to stick your tongue out, when to swallow, when to elevate your palate; need a cortical input to tell them when to contract
◦ something is gonna be different about this pathway (will see in the next slide)

Answer 19

corticospinal tract
pyramidal decussation
LMN
ipsilateral
two

Question 20

Corticobulbar or Corticonuclear axons

Lower motor neurons in
Cranial nerves are driven
by upper motor neurons (____ UMN) but the innervation is ____ not contralateral.

•
What we just showed on the previous slide was how LMNs in spinal nerves got a contralateral UMN enervation but here (see slide below) is different ..
◦ there is a random motor neuron in a cranial nerve and most of our CN are exiting from the f ____ and if exiting from left side of the brain then they are enervating muscles of the left side of the body… I ◦ Look at how UMNs enervation of LMNs in cranial nerves is different ..its not
contralateral ..its ____ …why this functional difference??
‣ Answer: you wanna have the ability to move your ____ upper limb w/o moving your
right upper limb ..some individual control to move one limb w/o the other

Answer 20

corticobulbar or corticonuclear
bilateral

brainstem
bilateral
left

Question 21

◦ but whats the thing that is similar about cranial nerves ?
‣ many of the structures that are enervated by the cranial nerve span across the ____
‣ when you stick your tongue, you don’t stick half of it, you stick out the whole thing…same thing w/ muscles of mastication, you are not just elevating the mandible one side, you are elevating it symmetrically
‣ Most of the cranial nerves enervate muscles that are located across the midline so that demands a ____ enervation
◦ We call UMNs in cranial nerves—> ____ axons bec where the axons synapses will be in cranial nerve nuclei somewhere in the brain stem

Answer 21

midline
bilateral
corticobulbar or corticonuclear

Question 22

• Lets put a clinical spin on this..what area are we gonna see hypothetically in a stroke pt with a blood supply block in UMNs in the right motor cortex, where will the pt have weakness?
◦ Answer: if I have a right side cortical stroke, the Pt is gonna have have weakness of muscles in the ….____ SIDE!
• Lets say I have a right side cortical stroke where I have destroyed all of these cortical nuclear axons on one side, will this pt have any weakness in the ability to contract CN enervated muscle?
◦ answer is ____ bec they will still have the intact motor cortex giving enough drive to generate contraction of cranial nerves enervated muscles
◦ so there is a very different clinical scenarios in stroke its depending what part of motor cortex you disrupt in a vascular insult.
◦ …however this is anatomy, there is always an exception! …which is illustrated on the next slide !!!

Answer 22

left

no

Question 23

Corticobulbar fibers: bilateral UMN to LMNs in cranial nerves. Exception: CN ____

• the EXCEPTION is how LMNs in the facial nerve get their UMNs enervation.,
• so what does the facial n. do?
◦ enervates all muscles of facial expression..
◦ for ex: the right facial n. gives you the ability to flare the right nostril, wrinkle the right side of forehead, purse lips on the right side …bec again all LMNs are ipsilateral!!
• In our example below, we are talking abt the left facial n.
◦ the LMNs of facial n. are largely found in the ____ nucleus in the brainstem
◦ but here is the interesting twist…it turns out that ONLY SOME of LMNs in the facial n. are getting a simultaneous
____ cortical input…which ones?
‣
ONLY the facial motor neurons that allows you to wrinkle the forehead and shut the eyes ..only those that are going to the ____ half of the face are getting a simultaneous lateral cortical enervation, like all of the other CNs

Answer 23

VII
facial
bilateral
upper

Question 24

◦ But now look whats different about the lower face muscles that give you the ability to flare your nostrils, frown, smile and purse your lips.
‣ the lower face muscles are ONLY being driven by the ____ motor cortex; a one-sided enervation like spinal nerves
‣ What does this means clinically??
• the comparison is shown in the diagram above
• if we have a complete lesion of left facial n. –> pt has ____: complete ipsilateral weakness of muscles of facial expression
‣ Whats the difference if we have a cortical stroke that destroys in this example in right motor cortex all of the
corticobulbar fibers? –> its NOT gonna have any effect on all of our cranial nerves enervated muscles …but basically where will the pt have facial weakness? only in their ____ face..still be able to shut both eyes and wrinkle forehead bec upper face muscles are getting bilateral bulbar enervations
‣ nobody understand why this phenomena is present!!

Answer 24

contralateral
bell’s palsy
contralateral lower

Question 25

Two Body and Limb Sensory Pathways that begin in thecord: each consists of ____ Neurons that project to contralateral cortex.

• Now having said all that how do we process sensory information?
◦ answer: we utilize THREE neurons!
◦ we are saying that basically when your brain responds consciously to a sensory stimulus, your sensory cortex is at the end of a 3-neurons pathway
◦ Each of these pathways is similar which is why we have this simple diagram on the left ..each will begin at same receptor …maybe receptor in skin, muscles, in response to smell, taste, proprioreceptors
• So now the first neuron in all sensory pathways –> is a sensory neuron derived from ____ thats carrying the sensation in either a spinal or cranial n.
◦ so our story now really is to process sensory information that is entering in all 31 pairs of spinal nerves that is coming from sensory receptors from skin or skeletal muscles
• so whats the goal of first neuron in a sensory processing pathway –> enter the ____ and find and synapse with a second neuron

Answer 25

neural crest

spinal cord

Question 26

• Second neuron –> in a sensory processing pathway is ALWAYS ____ to the first neuron
◦ but now look what happens to the axons of the second neurons?
◦ they cross the ____ whether in the spinal cord or brainstem depending on where their cell bodies are…they coalesce
and form a tract of axons with the goal of finding a third neuron
• Third neurons –> are mainly in the ____ (part of the diencephalon; relays sensory information so we can perceive the nature of the sensation consciously )
◦ Sensory processing pathways are similar to contralateral pathway involved when we generate voluntary contractions of skeletal muscles enervated by spinal nerves
◦ …so all of the sensory information that is entering the spinal nerves from the left side of the body is gonna end up projecting to ____ side somatosensory cortex, where we perceive a conscious awareness of whatever the sensation was

Answer 26

ipsilateral
midline
thalamus
contralateral

Question 27

Two Body and Limb sensory systems: one carries touch and proprioception; ____ System

the other carries pain and temperature; ____ System

• The first neuron in both pathways is the ____ that has its cell body in a dorsal root ganglion (all first neurons are derived from ____)
◦ the axons project in and look for second neuron that is ____ to the entry point…second neurons are in very different positions inside the CNS …
◦ but then look what happens to axons of second neurons of both of these pathways –> they project across the ____ up to a specific nucleus that contains the third neuron in the ____
◦ and then all of these 3 neuron sensory pathways project up to conscious levels of ____ cortex so you perceive the nature of the sensory stimulus consciously
• In summary: We are using 2 parallel 3-neuron pathways that are processing all of our body wall, limb, trunk and cutaneous muscular sensations and using 3 neurons that begin by sensing whats going on the left side of the body, ultimately influencing cortical activity in the right hemisphere
‣ bec all of these sensory pathways have a second neuron that is crossing the midline of the brain

Answer 27

dorsal column medial lemniscal
anterolateral

dorsal root
neural crest
ipsilateral
midline
thalamus
cerebral

Question 28

Brainstem is
home to 9 of 12
Cranial Nerves;
CN’s ____ but not CN ____

This slide shows entry and exit points of cranial nerves.
• 9 out of 12 cranial nerves enter/exit at ____(exceptions: CN I, II, XI)
◦ Cranial XI is really a misplace cervical spinal cord nerve that becomes a cranial nerve not because it exits from brain stem, but because it exits from a ____ in the skull.

There is a linear ascending nomenclature numerically of cranial nerves based on where they are entering and exiting the brain stem

____ contains CN3, 4
____ contains CN 5, 6, 7, 8 ____ contains CN 9, 10, 12

Answer 28

3-12
11
brain stem
hole
midbrain
pons
medulla

Question 29

Brainstem has separate medial and lateral vascular territories.

CN’s V, VII, VIII IX and X
are ____ nerves that enter/ exit ____

CN’s III, IV, VI, XII are ____ nerves that exit ____

Another important note: brainstem has separate medial and lateral vascular territories.
• If a patient has a brain stem stroke, it will give rise to either a lateral brain stem stroke or a medial brain stem
stroke, because those regions of brain have different ____ supplies.
There is a similar feature about the cranial nerves
• Purely motor cranial nerves are entering/exiting near the medial/ventral midline of the brain stem aka medial
brainstem vascular territory (CN 3, 4, 6, 12).
• Mixed cranial nerves are entering/exiting the brainstem laterally
◦ 4 major mixed cranial nerves (CN5, 7, 9, 10) are derivatives of ____ apparatus (embryology) i.e. skeletal muscles, skin, mucosa of pharyngeal apparatus.
◦ CN 8 is also mixed even though it’s not involved in ____ apparatus, which is why it’s positioned ____ near the pons-medulla junction.

Answer 29

mixed
laterally
motor
medially

blood
pharyngeal
pharyngeal
laterally

Question 30

Neural Tube
Tube and cord:
S- Sensory- ____
M- Motor- ____

Functional components of cranial nerves are classified using
3 letter codes.
SVE (middle column) and GSA (Spinal nucleus of V) migrate

Section through 1/2 of neural tube
1. Because of polarity in neural tube, sensory neurons are in ____ position, motor neurons are in ____
position
2. Postnatally, spinal cord looks similar to this organization.
3. In brainstem, the previous organization is rotated 90 degrees so that the motor neurons are positioned
____, and the sensory neurons are positioned ____.
A. This explains why motor CNs enter/exit medially, and mixed CNs enter/exit more laterally.

Answer 30

dorsal
ventral
dorsal
ventral

medially
laterally

Question 31

Global picture of where we are going
• we see all 12 CNs
◦ 3 are ____ nerves
◦ CN 8 is ____
◦ 5 purely ____ nerves
◦ 4 ____ pharyngeal arch nerves
• As you can see, mixed CNs can have a wide variety of combination of functional components i.e. 2 kinds of motor components and 1~3 kinds of sensory components
• Purely sensory CNs are straight forward. Motor CNs only innervation skeletal muscles, except CN3, which also carries parasympathetics.
We are going to organize these functional components of CNs into a series of functional column, but we are identifying these functional columns by some sort of 3 letter sensor or motor components

Answer 31

sensory
mixed
motor
mixed

Question 32

Cranial nerve nuclei:
Most have the same name as the nerve!
Most are at entry or exit point of the nerve

Dorsal view of Brainstem
Motor nuclei are ____; Sensory nuclei are ____

Schematic view of brainstem from above
• Again, motor neurons are positioned medially (M) and sensory neurons are positioned laterally (S)
• In terms of memorizing CN nuclei: most nuclei have the same name as the nerve i.e. facial nuclei, trigeminal
nuclei, trochlear, oculomotor, abducens, hypoglossal
• Most of the nuclei associated with CNs are located in the same part of the brainstem where that CN is going
in or going out
◦ Midbrain has nuclei associated with CN 3, 4. Pons has nuclei associated with CN 5, 6, 7, 8. Medulla has
nuclei associated with CN 8, 10, 12

Answer 32

medial

lateral

Question 33

Notice 3 discontinuous motor columns, and 3 almost continuous sensory columns
• Closest to the midline, we have lower motor neurons that will exit the brainstem in purely ____ CNs (CN ____).
◦ Fortunately, names of these nuclei are the same as the names of the CNs
• 2nd column in grey is a discontinuous column of ____ neurons. We know that 4 CNs carry parasympathetics out of the brainstem (CN ____)
◦ The location of parasympathetic nuclei is near the point where their respective CN that carries the parasympathetic axons will leave the brainstem
• Pink column is an additional population of ____ neurons, but because they develop somewhat differently, they are in a different column
◦ These lower motor neurons are going to innervate muscles that develop in the ____ arches.
◦ Histologically, the skeletal muscles in pharyngeal arches are not different from skeletal muscles found in
other part of the body. They just have a different ____ origin (CN ____)

Answer 33

motor
3, 4, 6, 12

parasympathetic
3, 7, 9, 10

lower motor
pharyngeal

embryologic
5, 7, 9, 10

Question 34

Names of the motor nuclei
• In addition to showing the names of nuclei, Dr. White highlighted their basic functions
• Note that the names of the ____ neurons in column #1 (red) has the same name as the nuclei.
◦ i.e. lower motor neurons in the midbrain are named ____ nucleus and trochlear nucleus, abducens nucleus in pons, and hypoglossal nucleus in medulla
Reads the basic functions associated with each nucleus

GSE- Regular Skeletal Muscle: Where do these nerves exit?

III Nuc.
____ eye
Raise ____

IV Nuc.
____ eye

VI Nuc.
____ eye

XII Nuc.
Move ____

Answer 34

lower motor
oculomotor

adduct and elevate
eyelid

depress adducted

abduct

tongue

Question 35

GVE- Parasympathetic

Nuc. of Edinger Westphal (____)
Pupil ____
____ response

Superior Salivatory Nuc. (____)
____
Saliva

Inferior Salivatory Nuc. (____) ____

Dorsal Motor Nuc. of ____
____

Answer 35

III
constriction
near

VII
tears

IX
saliva

X
gut

Question 36

Discontinuous column of parasympathetic neurons
• These parasympathetic nuclei have funny names..
• Parasympathetic nucleus of CN3 is know as Edinger Westphal
◦ it contains preganglionic parasympathetics that exits CN3 and facilitates pupillary constriction and near
response (changing the shape of lens reflexively

• Parasympathetic nucleus of CN7 is known as Superior Salivatory Nucleus
◦ Parasympathetics of facial nerve innervate many ____. All of nasal cavity mucous glands, salivary glands, and the lacrimal gland are all controlled by superior salivary nucleus
◦ These are preganglionic neurons that have to find a way to synapse at two of the parasympathetic ganglia of CN7, which are ____ and ____.

Answer 36

glands

pterygopalatine
submandibular

Question 37

• Parasympathetic nucleus of CN9 is known as Inferior Salivatory Nucleus
◦ Also a 2-nerve pathway (pre & post ganglionic) system that generates saliva out of the ____ gland.
‣ what does parotid mean? it means par (near) otic (ear). so it means near the ear.

• Parasympathetic nucleus of CN10 is know as Dorsal Motor Nucleus
◦ it’s a major generator of parasympathetics because the vagus nerve wanders throughout the thorax and most of the abdomen, innervating ____, lungs, and most of the GI tract.

This is our 2nd discontinuous column of, in this case, ____ neurons.

Answer 37

parotid
heart
pre-ganglionic parasympathetic

Question 38

SVE - Pharyngeal Arch Motor

Motor Nuc. of V:
____

Motor Nuc. of VII:
____ expression

Nucleus Ambiguus (IX, X):
\_\_\_\_, Pharynx, Larynx muscles

These are the pharyngeal arch lower motor neurons (pink column)
• They develop same kinds of skeletal muscles, but they develop in the ____ arch
• They have the same names as the nerves that carry them Reads the list of nuclei
• Motor Nucleus of V
◦ Mastication
• Motor Nucleus of VII
◦ discussed in the last hour that it has a different ____ drive than all these other cranial nerve innervated nuclei
◦ facial expression
• Nucleus Ambiguus
◦ contains lower motor neurons of CN____ and ____ that goes to all of our ____ muscles, pharynx muscles, and larynx muscles that we use in ____ and phonation

Answer 38

mastication
facial
palate

pharyngeal
cortical
9
10
soft palate
swallowing

Question 39

Solitary Nuc. SVA-Taste (____)

GVA-Carotid sinus, Carotid body
(____)

The ____ side
• It has continuous columns of sensory neurons
The first group (green) is called ____
• it’s a visceral sensory nucleus
◦ The upper end of the nucleus (a) is responding to ____
‣ What is carrying taste into solitary nucleus? CN7(anterior 2/3 of tongue), CN9 (posterior 1/3), and CN10 (beyond tongue)
◦ Caudal end of solitary nucleus is involved in ____ function
‣ responds to changes in receptors in carotid sinus and carotid body.
• carotid sinus is a ____ receptor
• carotid body is a ____
‣ CN9 and 10 (some controversy over this) sensory input to the caudal end of solitary nucleus

Answer 39

7, 9, 10
9, 10

sensory
solitary nucleus
taste
cardio-respiratory
blood pressure
chemoreceptor

Question 40

SSA-____ nuclei
SSA-____ nuclei

Light Blue
Vestibular nuclei and cochlear nuclei
• They receive cochlear and vestibular input conveyed by the ____
• “we don’t have to worry about how the brain is processing such information”

Answer 40

vestibular
cochlear
CN8

Question 41

GSA-Trigeminal Nuclei

Mesencephalic: ____

Main, Chief or Principal Nucleus: ____

Spinal:
____

Section

Elongated column of blue neurons that spans the entire length of the ____
it contains 3 different populations of sensory neurons associated with the ____ nerve (largest CN with many branches)

Mesencephalic nucleus
A. The word mesencephalic means midbrain
B. Responds to ____ sense - innervates muscle stretch receptors mainly but not exclusively in the
____

Main, Chief or Principal nucleus (3 synonymous names)
A. located at the exit/entry point of CN5 at the upper part of ____
B. Just responds to ____ touch, or mucosal touch, and touch sensation in the ____ part of tongue

Spinal nucleus of V
A. Extends through pons and through the length of ____
B. Almost exclusive just responds to ____ (face, anterior 2/3 tongue, oral cavity mucosa)

Answer 41

proprioception
touch
pain and temperature

brainstem
trigeminal

jaw position
muscles of mastication

pons
facial
anterior

medulla
pain and temperature

Question 42

How does the brain process facial touch, pain and temperature
using the Trigeminal nerve?

Borders between V1, V2, and V3 are ____, unlike Dermatomes
V1 ophthalmic division
V2 maxillary division
V3 mandibular division

For pain and temperature, the face has an ____ skin topography a-d in the spinal nucleus of V (____)

There are 3 separate divisions, hence the name trigeminal, that are carrying sensory information from skin of the face.
• 3 divisions of CN5 innervate 3 rigid dermatome-like regions that don’t ____ (much of the dermatomes through out the body has overlaps)
• We see V1 (ophthalmic), V2 (maxillary), and V3 (mandibular) and the relative cutaneous areas of skin that they serve in a non-overlapping fashion.
• All other cutaneous innervation of head and neck is by ____ nerves, beginning with C2, C3, C4 so
forth.

Answer 42

sharp
onion
nucleus caudalis

overlap
cranial spinal

Question 43

Not only do we see a division-like rigidity associated with these dermatomes, there is also what we call an onion skin topography of how certain parts, particularly the spinal nucleus of V, is processing facial ____.

There is a small area of cutaneous distribution of CN____ that are in around the external auditory meatus, the pinna, and to some degree skin extending to behind the ear.

Answer 43

pain and temperature

7, 9, and 10

Question 44

The Trigeminal system also utilizes ____ neurons to convey facial pain and temperature to somatosensory cortex.

First neuron in ____ ganglion

Second neuron in ____ of V for facial pain and Temperature Spinal nucleus of V descends down through caudal ____

Axons of spinal nucleus cross and course with ____ tract

Third neuron in ____

Answer 44

3
trigeminal
spinal nucleus
pons and medulla
spinothalamic
VPM thalamus

Question 45

How does this work?
• We see 2 parallel 3 neuron pathways.
• Note where the first neurons in trigeminal sensory processing pathways are.
• derived from ____
• found in trigeminal ganglia (lies in the base of the skull) (it’s analogous to ____ ganglia which are the first
neurons of our body wall processing pathways)
◦ If these trigeminal neurons, if they are responding just to facial, mucosal, or tongue touch, they project in
trigeminal nerve and synapse on 2nd neurons in ____ of V.
‣ The axons of the 2nd neurons cross. They synapse on the 3rd neurons in the ventral posteromedial
nucleus (VPM) of thalamus, and they project to somatosensory cortex.
◦ Note there is also a series of 3 neuron pathways that are responding to facial pain and temperature
‣ Cell bodies are in V ganglia, but the axons descend down and synapse at various parts of the spinal nucleus that extends all the way down the length of the brainstem and basically use the 2nd neurons
to process pain and temperature
So again, parallel 3 neuron pathways conveying all of our facial sensory input to the contralateral cortex, which is analogous in every way to our ____ processing

Answer 45

neural crest
dorsal root
main sensory nucleus
body wall

Question 46

Trigeminal Nerve

What does CN5 look like?
• “we are not going to talk about all of its branches. We only point we wanna make here is…”
• Trigeminal ganglion - responds to all of our ____ sensations (touch, pain, and temperature)
• Only V3 (mandibular division) has ____ root containing lower motor neurons that come from the ____ nucleus
◦ These lower motor neurons that innervate the muscles of mastication are getting a simultaneous
____ cortical input
‣ “That was the theme of how lower motor neurons in CNs got their input. It was bilateral except for
our lower face muscles.”

Answer 46

facial
motor
trigeminal motor
bilateral

Question 47

Nucleus caudalis part of Spinal nucleus
of V

How does this onion skin topography actually relate?
• Different regions of teeth, gums, mucosal, and sensory innervation just for ____ has this onion skin array that predicts where in this spinal nucleus of V the information will synapse.
• Zone 1: related to ____ pain generated in the maxillary and mandibular teeth
• Zone 2: also some tooth pulp pain from maxillary and mandibular, certain skin in ____, V2, V3 divisions…(he
stops explaining zones at this point)
• Notice how Zones ____ are synapsing at the cranial end of spinal nucleus of V
• The further back we move out on the onion skin (angle of mandible and forehead), those pain and temperature sensations are receiving trigeminal inputs way down at the ____ end of the spinal nucleus of V.
• Regardless of where the 2nd neurons are, they must ____ on their way to thalamus

Answer 47

pain and temperature
tooth pulp
V1
1 and 2
caudal
cross

Question 48

Functional anatomy and blood supply of cerebral hemisphere
• This will give us an opportunity to organize and indicate where we find primary motor cortex and where we find somatosensory cortex that were the end points of or the beginning point of all our neural systems

Note that the entire brain has a dual blood supply
• we identified the sources of blood supply as being ____ circulation or the ____
artery circulation
• As we will see shortly, the branches of these circulations ____ together so that brain has readily
available source of collateral blood supply. If we block one artery overtime, we can develop collateral circulation through anastomoses circulations between these two separate circulations.

Answer 48

anterior/carotid
posterior/vertebral
anastamose

Question 49

Brain blood supply

What do these circulations look like?

Running up the ____ surface of the brainstem are the beginnings of posterior circulation.

Posterior circulation is provided by a pair of ____ arteries that join together to form the ____ artery.
Therefore, the posterior circulation supplying the brainstem and cerebellum with medial and lateral branches is called the ____ or ____ circulation

Each internal carotid artery, as it approaches the base of the brain, gives rise to a ____artery, supplying the ____ aspect of the hemisphere.

Arising more acutely from the internal carotid is the ____ artery that will head much more ____

Answer 49

ventral

vertebral
basilar
vertebrobasilar
posterior

middle cerebral
lateral

anterior cerebral
medially

Question 50

The 4 anatomic lobes are
named for the bones that cover the hemispheres; more later

Each lobe of a hemisphere was named based on the ____ that covered it • Not functionally logical, but anatomically logical
Note the lateral aspect of each hemisphere is partially divided by a pair of deep indentations.
• Central sulcus - separate ____ lobe from ____ lob
• Lateral sulcus - very deep, separates the tongue-like ____ lobe below from from frontal, parietal, and
occipital lobes.
This was the initial way neuroscientists named the lobes of the brain

Answer 50

bone
frontal
parietal
temporal

Question 51

Blood supply to cerebral hemisphere
A) Note the lateral aspect of each hemisphere is mainly supplied by branches of ____ artery. Anterior and posterior cerebral arteries creep over the top and sides of each hemisphere to help with blood supply, but the predominant blood supply of the lateral aspect is the ____ artery.
B) Note the medial aspect of each hemisphere is mainly in the vascular territory of the ____ artery, and little less so of the posterior cerebral artery

Answer 51

middle cerebral
middle cerebral

anterior cerebral

Question 52

Corticobulbar or corticonuclear neurons

Corticospinal neurons

We can now visualize how motor and somatosensory cortex is organized.

In a moment we will see that some stuff we see in the lateral aspect of one hemisphere is different from that of the other hemisphere because of a feature called ____.
We find primary motor cortex in red and primary sensory cortex in blue.
• The primary motor cortex is the home of the cell bodies of ____ neurons
◦ since we are look at a left hemisphere, we know they generate voluntary contraction on the right side of the body

Answer 52

dominance

upper motor

Question 53

Corticobulbar or corticonuclear neurons

Corticospinal neurons

Functional specificity of the lateral side of the hemisphere upper motor neurons are organized topographically
◦ close to the lateral fissure (area that says face), we find all of our ____ neurons that
are mainly bilaterally innervating ____ neurons in CNs.
Extending from that, we have upper limb and trunk motor neurons that are reflected on the ____ aspect of the hemisphere (these act contralaterally as well)
Note right next to the primary motor cortex is the primary sensory cortex
• similarly the left side represents half of the face, one limb, one arm, half of trunk contra laterally (right side)

Where is the rest of the body? The extension of these cortical areas on the ____ aspect of the hemisphere.
Since the rest of the body is found on the medial aspect, it has a different ____ blood supply from the two cortical areas seen on the lateral aspect of the hemisphere (red and blue on diagram)
• Recall that middler cerebral artery is the main blood supply of the lateral aspect, while the anterior cerebral artery
is the main blood supply of the medial aspect

Answer 53

corticobulbar or corticonuclear
lower motor neurons
lateral

medial
arterial

Question 54

Here is the ____ limb that’s extending to the medial aspect of the hemisphere. Note that it is in the blood supply of the ____ artery.
This disproportionate representation in both primary motor and primary somatosensory cortex forms what we call motor or ____.
• What is a homunculus? A little disproportionate person where we see a ____ representation of the contralateral side of the body for both sensory processing and motor function

What we also see in the medial aspect of the hemisphere is what we call ____ cortex is in the vascular territory of the ____ artery (area in pink)

Answer 54

lower
anterior cerebral
somatosensory homunculus
disproportionate
primary visual
posterior cerebral

Question 55

Coronal section
• Again, for both motor and somatosensory cortex, we are seeing draped out across the lateral aspect of the hemisphere, the ____ half of the body contra laterally.
• Extending down the medial aspect of the hemisphere, we see the upper motor neuron and somatosensory
function of contralateral ____ limb.
• This view also shows the dual blood supply
◦ upper half of the homunculus (lateral aspect) is in the vascular territory of ____ artery
◦ lower half of the homunculus (medial aspect) is in the vascular territory of the ____ artery.

Answer 55

upper
lower
middle cerebral
anterior cerebral

Question 56

Blockage of the Middle cerebral artery will result in a contralateral ____ limb and ____ face weakness and/or a contralateral face and upper body sensory loss

Blockage of the Anterior cerebral artery will result in a contralateral ____ limb
weakness and/or a contralateral lower body sensory loss.

Clinically what does this mean? Reads slide
• For middle cerebral artery blockage, why only the lower face weakness? Because the corticobulbar neurons ____ innervate all of our lower motor neurons in CNs, except for the contralateral lower face

Answer 56

upper
lower

lower

bilaterally

Question 57

The major language centers are in the ____ hemisphere.

Broca’s area
____

Wernicke’s area
____

Angular gyrus
____

Answer 57

left
motor speech
oral comprehension
written comprehension

Question 58

Lateral aspect of the left hemisphere has been statistically shown to be the dominant hemisphere for language.
• The later aspect of the left hemisphere contains our major language centers that give us the ability to
communicate verbally in complete sentences and also give us the ability to understand what someone else is saying to us.
• Our major motor speech area and our major areas of language comprehension are statistically found on the
____ aspect of the left hemisphere.
• What is the blood supply to these regions? Since they are located on the lateral aspect, they are supplied by
the ____ artery.
• Therefore, ____ MCA stroke has the potential to cause language disorders, whereas a ____ MCA stroke
statistically do not.
• So left MCA stroke can cause not only motor and sensory problems, but also ____ (disorders of language)

Answer 58

lateral
middle cerebral
left
right
aphasia

Question 59

Is there a correlation between the language centers of left hemisphere and handedness?
• In 95% of right handers, the language centers are located on the lateral aspect of the ____ hemisphere
• In 75% of left handers, the language centers are still located on the ____ hemisphere
• So almost regardless of handedness, your language centers are localized on the lateral aspect of the left
hemisphere (although the left handers seem to have more ____ representation of the location of the language centers).
◦ Left handers with MCA stroke have don’t have as ____ aphasia as an individual who is right handed
• Does the right hemisphere have a language function? Yes.
◦ The right hemisphere gives you the ability to add ____ content to your speech and the ability to understand the emotional content of someone else’s speech. So we have the emotional content centers in the ____ hemisphere, but the most important language centers for literally giving you the ability to speak in complete sentences and understand what is being said to you statistically are on the lateral aspect of the ____ hemisphere.

Answer 59

left
left
bilateral
severe
emotional
right
left