Nervous System Flashcards
myelinating glia in the CNS are called ______ while in the PNS they are _____
CNS : Oligodendroglia
PNS : Schwann cells
Describe the structural components of the peripheral nervous system
cranial and spinal nerves (all other NS structures that connect CNS to body)
-develop from neural crest cells
spinal nerve = mixed nerve (mixed with different neuronal axons) that carry motor, sensory and autonomic signals between the spinal cord and the rest of the body.
-pattern: dermatomes
Describe the meninges (CT) covering the CNS from external to internal layers
Dura (thick, overlying, most external dense connective tissue under skull - continuous with periosteum in bone)
Arachnoid (delicate sheet of connective tissue; subarachnoid: blood vessel supply, CSF fluid circulates to protect brain; arachnoid trabeculae-loose connective tissue)
Pia (innermost layer, directly adherent to the brain and spinal cord which is continuous with the perivascular connective tissue sheath of blood vessels of the brain and spinal cord.)
Somatic NS provides sensory and motor innervation to all parts of the body except?
viscera
smooth and cardiac muscle
glands
Sympathetic nervous system vs. Parasympathetic nervous system
S (fight or flight)
P (rest and digest)
Describe the functional components of the peripheral nervous system
Autonomic (visceral) NS (excitatory and inhibitory) communicates with INTERNAL organs and glands (autonomic = visceral = organs = internal)
Somatic (body) NS (excitatory) communicates with sense organs and voluntary muscles -receives info from and responds to EXTERNAL world (somatic = parietal = body = external)
- Sensory Afferents (INPUT)
- mostly along dorsal spine
- Motor Efferents (OUTPOUT)
- mostly along ventral body
(SAME DAVE!)
Sensory Afferent Motor Efferent
Dorsal Afferent Ventral Efferent
Describe the functional components of the peripheral nervous system
Autonomic (visceral) NS (excitatory and inhibitory) communicates with INTERNAL organs and glands (autonomic = visceral = organs = internal)
Somatic (body) NS (excitatory) communicates with sense organs and voluntary muscles -receives info from and responds to EXTERNAL world (somatic = parietal = body = external)
- Sensory Afferents (INPUT)
- mostly along dorsal spine
- Motor Efferents (OUTPOUT)
- mostly along ventral body
(SAME DAVE!)
Sensory Afferent Motor Efferent
Dorsal Afferent Ventral Efferent
How do the somatic and visceral nervous systems differ, both structurally and functionally?
The visceral (autonomic/organs) NS communicates with internal organs and glands after detecting information within the body in order to respond, and is broken down into: -Sympathetic (fight or flight) and -Parasympathetic (rest and digest) divisions
The Somatic (body) nervous system communicates with voluntary muscles and sense organs, and contains sensory afferents for input (receives info from external world) and motor efferents (responses to sensory info from external world) for motor output. -Innervates structures that develop from somites.
Sensory input is along the dorsal spine/coming up your back, while motor output is primarily ventral
Which cells are found in the CNS? the PNS?
CNS
- Neuron (functional cells)
- group of neuronal cell bodies = nucleus
- Glia (supporting cells): Astrocyte, Oligodendroglia (myelinating axons), Microglia
PNS
- Neuron
- group of neuronal cell bodies = ganglion (DRG)
- Glia (Schwann cells)
Describe the PNS connective tissue layers
3! epi! peri! endo!
Epineurium: vascularized, dense irregular connective tissue surrounding nerve fascicles into common bundle of nerve fibers (adipose is associated with epineurium in large nerves)
Perineurium: Vascularized, specialized connective tissue surrounding a nerve fascicle that contributes to the formation of the blood-nerve barrier by serving as a metabolically active diffusion barrier
Endoneurium (around each axon and its schwann cell, nerve fiber): loose connective tissue surrounding each individual nerve fiber, visible at EM (collagen fibrils)
Epineurium
PNS
densest layer*- what we see as the nerve in lab
vascularized, dense irregular connective tissue surrounding nerve fascicles into common bundle of nerve fibers (adipose is associated with epineurium in large nerves)
Perineurium
PNS
Vascularized, specialized connective tissue surrounding a nerve fascicle that contributes to the formation of the blood-nerve barrier by serving as a metabolically active diffusion barrier
-surrounds functional group of axons
Endoneurium
PNS
around each axon AND its associated schwann cell, nerve fiber): loose connective tissue surrounding each individual nerve fiber, visible at EM (collagen fibrils)
Autonomic system is primarily “input”, true or false?
FALSE
-the bigger part of autonomic is OUTPUT to communicate with internal organs and glands
major divisions of output are sympathetic and parasympathetic nervous systems
Neural crest cells give rise to PNS, true or false?
TRUE
Which functional part of the nervous system drives and balances homeostasis?
VISCERAL (organs)
-bc it innervates both the organ systems AND their corresponding elements to respond to information it has detected within the body
True or False, the somatic nervous system innervates structures that develop from somites, which originate from paraxial mesoderm in embryonic development.
TRUE
paraxial mesoderm > somites > somatic (body)
Glia are the functioning cells and neurons are the supporting cells in the NS, True or False?
FALSE
neurons are the functioning cells, glia support
What are the different names for a group of neuronal cell bodies in the CNS vs PNS?
CNS: Nucleus
PNS: ganglion (think DRG=dorsal root ganglia)
True or False, the Schwann cell is doing pretty much everything to support the PNS neurons, but in the CNS this support is divided between several different cells.
TRUE
Dura mater
from the mesenchyme cells surrounding neural tube
thick, overlying, most external
-dense connective tissue of the 3 meninges in the CNS
-has component very closely associated with inner lining of the bone (skull, vertebrae) called the periosteum
under skull - continuous with periosteum in bone
Arachnoid
from neural crest cells
delicate sheet of connective tissue; subarachnoid: blood vessel supply, CSF fluid circulates to protect brain; arachnoid trabeculae-loose connective tissue
Pia
from neural crest cells
Innermost layer, directly adherent to the brain and spinal cord which is continuous with the perivascular connective tissue sheath of blood vessels of the brain and spinal cord
Pia-think pea (smallest/thinnest meningeal layer, it’s usually ONE CELL thin)
The outer lining of the dura mater is usually in close association with or adherent to the periosteum of the skull but not the vertebrae, True or False?
FALSE, adherent or close proximity to both the skull and the vertebrae periosteum
-specifically the VERTEBRAL CANAL (cause that’s where we find the cord, dura is covering cord)
True or False, There is a significant space between the dura mater layer and the arachnoid layer with a weblike network
FALSE
weblike network extends between arachnoid and pia layers, filled with CSF
An axon has to be myelinated to have an endoneurium associated with it, True or False?
FALSE
The endoneurium is around: A. each axon B. each axon and its associated Schwann cell C. only myelinated axons D. myelinated or unmyelinated axons E. Both B and D F. Both A and C
E. Both B and D
In both the PNS and CNS, there are 3 layers of connective tissue, and vasculature can be found between the 2nd and 3rd layer in both cases. True or False?
TRUE
PNS: vessels between epineurium and perineurium (1 and 2) AND endoneurium and perineurium (2 and 3)
CNS: vessels between arachnoid and pia layers (in subarachnoid space)
Vessels in the PNS are more discretely defined than in the CNS, True or False?
FALSE
Vessels are going everywhere in the PNS (between both epi and perineurium, as well as endo and perineurium), however in the CNS they are more restricted (think higher and more complex organization in brain, causes further compartmentalization- needs to be more restricted) and are only between pia and arachnoid layers
Name the general structure of a neuron
- Dendrites (sensing, stimulated by environment or activities of other cells)
- Cell body (contains all the stuffz: nucleus, mitochondria, ribosomes, other organelles and inclusions)
- Axon (conducts the nerve impulse -action potential- toward the synaptic terminals/terminal boutons)
- Terminal boutons (look like buttons, affect another neuron OR effector organ, ie muscle or gland)
Dendrites
INPUT END
sensing end of a neuron that is stimulated by the environment or the activities of other cells
Cell body of neuron
contains all the structures like nucleus, mitochondria, ribosomes, other organelles and inclusions, want them all concentrated in one area and then thinner extended processes (like axon) can conduct APs (nerve impulses) toward the synaptic terminal faster
Axon
conducts the nerve impulse -action potential- toward the synaptic terminals/terminal boutons
Terminal boutons
OUTPUT END
SYNAPTIC boutons/SYNAPTIC ends/Terminal ends
A neuron functions via signal transduction, True or False?
TRUE
signaling is how neurons talk and sensory info is passed from dendritic sensory input to terminal bouton output
Neurons talk to other neurons both chemically and electrically, true or false?
TRUE
electrically: propagation of polarity continued
chemically: NTs like acetylcholine (ACh)
What are the three types of neurons we discussed?
Multipolar- multiple dendritic inputs and multiple terminal outputs
Bipolar- one long process coming in as input, one long process coming out, cell body usually in center
Pseudounipolar neurons- cell body in center with one long process that quickly bifurcates (branches) with one input branch and one output branch
Multipolar neuron
multiple dendritic inputs and multiple terminal outputs (multipolar = motor efferents in somatic- spinal cord)
-in somatic NS
EFFERENT/MOTOR: multipolar
AFFERENT:pseudounipolar
Dorsal Root Ganglion (DRG)
PNS (Outside CNS) = ganglion
-clusters with somatic and visceral (autonomic) sensory (AFFERENT) cell bodies (presynaptic sensory/afferents)
shape: PSEUDOUNIPOLAR cell
dorsal = back = primary afferent neuron
Ventral (Anterior) Horn
contain Somatic MOTOR nuclei (CNS) (IN COLUMN up and down spinal cord), axons come out and coalesce with ventral root
SAME DAVE (VE = ventral EFFERENT (Motor efferent))
-going to a MUSCLE
Somatic sensory and visceral sensory fibers start in the ___ and synapse in the _____
DRG (ganglion = PNS) Dorsal horn (of spinal cord = CNS)
Lateral Horn
- with ventral horn = ventral = efferent
- contain nuclei of VISCERAL (AUTONOMIC) SYMPATHETIC PRESYNAPTIC/PREGANGLIONICs (aligned in cell columns up and down spinal cord/connected)
OUTPUT for visceral/autonomics efferents (in cord)
right above ventral horns, VE = ventral efferent= LEAVING CNS to go to PNS
contains visceral MOTOR efferents
-going to an ORGAN or gland
Somatic efferents and visceral efferents both exit through the ventral root, true or false?
TRUE
SAME DAVE
efferent, motor, going away from CNS to body/PNS, VENTRAL
True or False, the lateral horn is the output for all of the visceral or autonomic efferents in the CNS?
FALSE
its the output center for the autonomic efferents in the CORD (only part of CNS)
-the brain also contains autonomic or visceral efferent outputs
The gray matter in the spinal cord is located in the _____layer while the white matter is located in the ____ layer
Gray matter: inner layer/INSIDE: cell bodies (nuclei)
White matter: outer layer/outside: tracts and pathways running up and down spinal cord located here
Ventral root
Anterior root = ventral = front = motor efferents, contains MOTOR fibers (OUTPUT) leaving spinal cord
Dorsal root
Posterior root = back = SENSORY afferents (DAVE, DA = dorsal afferent “you get stabbed in the back, you feel it = sensory”)
The spinal nerve is formed when the dorsal root and ventral root come together, and exit the vertebral canal via intervertebral foramen, true or false
True
Remember: spinal nerves are MIXED, sensory and motor components together
Once a spinal nerve exits the intervertebral foramen, it no longer remains functionally and structurally mixed (with both sensory and motor), and instead you see a bifurcation that gives rise to the posterior and anterior ____
Rami (posterior ramus, anterior ramus)
The dorsal ramus is a much larger component than the ventral ramus, true or false?
FALSE - the ramus is where the exiting spinal nerve (which was mixed with sensory and motor as it exited through the intervertebral canal) is now divided again anteriorly and posteriorly. Since the nerve is EXITING (OUTPUT) the VENTRAL or ANTERIOR ramus will be much larger, as output (EFFERENTS) are predominantly along the ventral surface
ventral ramus also has
Anterior rami connect to the _____
sympathetic ganglia (outside cord, body = ganglia = PNS) of the sympathetic trunk
-AUTONOMIC/VISCERAL NS
There are ___ pairs of spinal nerves
31 (Think vertebrae here- there are 7C + 12T + 5L + 5S + ~2C = 31, as the vertebrae develop, the spinal nerves follow in development)
There are ___ cranial nerves
12
How do NS projections/tracts/pathways cross the midline?
- decussation
- commissure
Ipsilateral
cell body and axon terminal on same side
Bilateral
cell body someplace, with axon terminals going to BOTH sides
Contralateral
cell body on opposite side of axon terminal
contralateral or bilateral indicates that what is happening?
some sort of crossing of the midline is occurring (so think decussation or commissure [=communication] is happening)
What are the functions of general afferent (sensory) neurons?
touch, vibration, pain, temperature, proprioception (spatial awareness)
-segmented innervation, follows DERMATOMES
Vision, olfaction, audition, taste, balance and equilibrium are examples of:
A. Special sensory efferent neuron functions
B. General motor efferent neuron functions
C. Special sensory afferent neuron functions
D. Special motor efferent neuron functions
E. General sensory afferent neuron functions
C. Special sensory afferent neuron functions
senses/INPUTS/AFFERENTS
Motor (efferent) neuron functions
General (somatic)
-segmented, follows myotomes
Visceral (AUTONOMIC NS)
- sympathetic
- parasympathetic
- enteric (GI)
Sympathetic chain ganglion
PREganglionic sympathetic cell bodies and fibers from lateral horn will go through white ramus communicans (myelinated) and enter the sympathetic chain ganglion. These axons then will either:
a) synapse at the sympathetic chain ganglion and exit through the gray ramus communicans
b) go up OR down the sympathetic trunk to synapse somewhere else
c) exit sympathetic chain ganglia as SPLANCHNIC NERVE (go affect an organ, but has NOT synapsed yet)
Axons that enter and then exit the sympathetic chain ganglia as splanchnic nerves have to reach a _____ to synapse.
collateral sympathetic ganglion
like in aorta
True or false, the collateral sympathetic ganglia are much closer to the target organ than the sympathetic chain ganglia?
True
Both the parasympathetic and sympathetic nervous systems of the autonomic NS have a two neuron chain, true or false?
TRUE
Autonomic NS has 2 neuron chain no matter what
What is the location of the sympathetic preganglionic cell body?
SYMPATHETIC: SPINAL CORD (lateral horn)
T1 to L2 (thoracolumbar)
What is the location of the parasympathetic preganglionic cell body?
Spinal cord OR brainstem (craniosacral)
-CNs (Cranial nerves) (brainstem)
AND S2-S4 (spinal cord)
Postganglionic cell body location is where the preganglionic cell and postganglionic cell body synapses, true or false?
TRUE
What is the location of the sympathetic postganglionic cell body?
sympathetic chain ganglia
OR collateral (prevertebral ganglia)
-via splanchic nn.
What is the location of the parasympathetic postganglionic cell body?
- 4 different cranial ganglia (head)
- all the rest reside in ganglia with organs (IN THE WALLS OF THE ORGANS THEY INNERVATE)
Preganglionic sympathetic cell bodies are located in the thoracolumbar region, while preganglionic parasympathetic cell bodies originate in the craniosacral region, true or false?
TRUE
Postganglionic parasympathetic reside in the head and the walls of the organs they innervate, true or false?
TRUE
Somatic nerve plexuses
Cervical plexus (C1 to C4) Brachioplexus (C5 to T1) Lumbar plexus (anterior rami L1 to L4) Sacral plexus (anterior rami L4 to S4)
NO THORACIC (some to brachioplexus but thats it)
Visceral nerve plexuses
going to all organs and cavities, from sympathetic chain
Vagal trunk (vagus-innervate the internal organs)
Prevertebral plexus:
a) splanchnic nn. to Greater, b) Lesser, and Least
c) Lumbar Splanchnics (shorter, smaller)
d) Sacral Splanchnics
What is the difference between myelinated and unmyelinated axons in the PNS?
BOTH have Schwann cells, but in the…
myelinated: the Schwann cell is wrapping around one axonal node each, enwrapping ONE axon via a series of Schwann cells; creating insulated thick layer of myelin and cell membranes for transduction down the axon
unmyelinated: non myelinating Schwann cell CYTOPLASM associates with MULTIPLE axons, but only engulfing it (not wrapping it); simply protects and supports axon
What is the difference between myelinated and unmyelinated axons in the CNS?
BOTH have oligodendrocytes
myelinated: series of oligodendrocytes line up along ONE axon, then each dendrite creates a wrapped coating of myelin insulating the axon nodes
unmyelinated: nonmyelinating oligodendrocyte CYTOPLASM encases/associates with/engulfs MULTIPLE axons
(no wrapped coating of myelin surrounding axon)
What gives rise to Schwann cells?
NEURAL CREST CELLS
PNS
True or false, one schwann cell can myelinate one axon?
FALSE
one Schwann cell per one INTERNODAL SEGMENT of one axon (takes multiple Schwann cells to myelinate one axon; vs. takes one nonmyelinating Schwann cell to associate with/engulf/encase multiple axons)
Oligodendrocytes are derived from which cells?
Neuroepithelial cells of the spinal cord (CNS)
True or false, one oligodendrocyte can myelinate only one axon?
FALSE, one oligodendrocyte can myelinate up to 50 axons!
*Oligodendroctyte = like an *Octopus - can go grab multiple axons to myelinate them
Neural groove (embryonic)
formed from the embryonic ectoderm, laterally we have neural folds that move medially until tops of folds join together and pinch off to form neural crest cels
Neural crest cells
neuroectoderm (most lateral portion of that embryonic ectoderm that thickened up to become neural plate)
at the top of the neural folds, pinch off when neural folds join together in the form of a tube
Form most of PNS:
- DRG/autonomic/CN ganglia
- bones of face (viscerocranium)
- melanocytes
- Schwann cells
- Leptomeninges (pia and arachnoid mater)
- Adrenal medulla cells
neural tube
neuroectoderm with inner neural canal
form brain and spinal cord
Embryonic ectoderm
forms the epidermis
epidermis and dermis come from embryonic ectoderm, true or false?
FALSE
epidermis: embryonic ectoderm
dermis: dermatomes, from paraxial MESODERM
Where is the neural canal and what does it give rise to?
inside neural tube, inner fluid filled region
-goes on to form central canal of spinal cord and VENTRICLES of the brain
When does the spinal cord develop? When does the brain develop?
spinal cord: Weeks 3-5
brain: almost entire span of pregnancy, up through your 20s
Spinal cord/neural tube is made up of what cells?
PSEUDOstratified columnar NEUROepithelium
Neuroepithelial cells
make up the neural tube and spinal cord
- act as stem cells (divide and give rise to cells that make up our CNS)
- first proliferate and give rise to Neuroblasts
Neuroblasts
will become neurons
come from neuroepithelial cells in spinal cord dividing (shows stages of mitosis in histo slide, closest to the lumen)
-will first migrate to mantle layer of spinal cord
Cell bodies of neuroblasts reside in the mantle layer of the spinal cord while their axons extend out into the marginal layer, true or false?
True
After neuroblast cell formation has seized, neuroepithelial cells continue to divide and derive _____, which migrate and develop into _____ in the mantle layer and _____ in the marginal layer of the spinal cord.
gliablasts:
ASTROCYTES in mantle
OLIGODENDROCYTES in marginal layer (myelinate axons of neurons)
After neuroblast formation stopped, neuroepithelial cells will become what and reside where?
Ependymal cells, residing closest to the lumen (centrally located)
Ependymal cells
from neuroepithelial cells
-reside closest to lumen (centrally located), produce and move CSF (central canal of spinal cord provide nutrients)
mesenchymal cells surrounding the neural tube give rise to what meningeal covering?
Dura mater
Describe development of spinal cord
Neurulation > Neural tube (neuroepithelial layer, mantle layer, marginal layer) > neuroblast formation and migration > swellings of alar and basal plates > gliablast formation and migration > gliablast developing into astrocytes and oligodendrocytes (contribute to growing/larger marginal layer aka white matter) > swellings become ventral, dorsal, and lateral horns aka gray matter > neuroepithelial cells become ependymal cells and line central canal (CSF fluid production/movement)
Neural Tube:
- neuroepithelial cells proliferate > give rise to neuroblasts > neuroblasts (become neurons)
- neuroblasts migrate to mantle layer, make up majority of mantle layer (axons in marginal layer)
- after neuroblast cell production is over, neuroepithelial cells (closest to lumen) continue growing and migrate to mantle (become astrocytes) and marginal layer (becoming oligodendrocytes)
As neuroblasts proliferate, we get dorsal and ventral swellings in mantle layer (MIDDLE layer almost ALWAYS functional): Alar plates (2): Afferent (sensory/dorsal swellings/posterior) functions
Basal plates (2) Efferent (motor/ventral/anterior) functions
As neuroblasts proliferate, we get dorsal and ventral swellings in mantle layer. Describe the difference between these two swellings
(remember: mantle = middle, MIDDLE layer almost ALWAYS functional in 3 layer structures)
Alar plates (2): Afferent (sensory/dorsal swellings/posterior) functions
Basal plates (2) Efferent (motor/ventral/anterior) functions
Alar plates
spinal cord development
dorsal swellings, afferent sensory functions
-smaller in spinal cord development (before butterfly shape) than basal plates
will become dorsal horns
Basal plates
spinal cord development
ventral swellings, (2) Efferent (motor/ventral/anterior) functions
will become ventral and lateral horns
sulcus limitans
spinal cord development
between alar and basal plates
How do spinal nerves develop?
Motor neurons:
- basal plate start with motor neuron cell bodies, send axons out of anterior region to collect and form ventral nerve root
- motor nerve fibers collect into ventral nerve roots
sensory neurons:
- a little more complicated
- dorsal nerve roots = primary sensory cell bodies = pseudounipolar (from neuroblasts from neural crest cells) are in DRG (in PNS outside spinal cord), with peripheral processes coming from receptors located in skin and joints and muscles and central processes going into the spinal cord at the dorsal horns, into alar plate where they’ll synapse into alar plate neuron
-distal processes of dorsal root fibers (sensory) join ventral root fibers (motor) to form a spinal nerve (remember: MIXED)
Where would you perform an epidural? Why?
L4-L5
L1-L2 is where spinal cord ends, but some peoples’ ends at L3
originally, embryonic spinal cord = length of vertebral canal allowing spinal nn to exit correct origin level in the vertebral column
as we age, vertebral column lengthens more rapidly than spinal cord, pulling roots down with it as it lengthens so they continue to exit their intervertebral foramen (pull dura down with it)
-cauda equina at L5
conus medullaris
spinal cord ends around L1-L2 in adults
spina bifada
“split spine” neural tube defect
vertebral arch doesnt form correctly, never fuses
- Spina Bifida Occulata
- Meningocele
- Myelomeningiocele
Spina Bifida Occulata
vertebral arch doesnt form but meninges and neural tube remain within vertebral canal
goes unnoticed until back xray (need radiography)
usually S2-S4, identified by patch of hair overlying that region
Meningocele
meninges protrude out of where vertebral arch should’ve kept them in, creating sac
Myelomeningiocele
meninges and the neural tube protrude out of where vertebral arch should’ve kept them in, creating sac
Parts of the brain
cerebrum
cerebellum
brainstem (midbrain, pons, medulla oblongata)
Brain development follows the same basic organization as the spinal cord, true or false?
TRUE
-distinct alar and basal plates
BUT: higher centers, accentuation of alar plates and regression of basal plates
Are alar or basal plates more prominent in the development of the brain?
ALAR =afferent, SENSORY
you’re in the fucking brain, of course the sensory part is bigger
What 3 swellings form in the neural tube during the 4th week of development in regards to the brain developing? Which brain vesicles are these called?
Prosencephalon (forebrain)
Mesencephalon (midbrain)
Rhombencephalon (hindbrain)
primary brain vesicles
Prosencephalon
=forebrain
becomes 2 secondary brain vesicles:
1) Telencephalon
- cerebrum: cerebral hemispheres (cortex, white matter, basal nuclei)
- contains lateral ventricles
2) Diencephalon
- Diencephalon (thalamus, hypothalamus, and epithalamus)
- contains third ventricle
Mesencephalon
=midbrain
becomes secondary brain vesicle Mesencephalon
- brain stem: midbrain
- contains cerebral aqueduct
Rhombencephalon
=hindbrain
becomes 2 secondary brain vesicles:
1) Metencephalon
- brain stem: pons
- cerebellum
2) Myelencephalon
- brain stem: medulla oblongata
both Met and Myelencephalon contain the fourth ventricle
Which adult neural canal is within the spinal cord?
central canal
In what primary AND secondary brain vesicles does the brain stem reside?
primary: mesencephalon (midbrain) and rhombencephalon (hindbrain)
secondary: Mesencephalon, Metencephalon, Myelencephalon
What are the parts of the brain stem?
midbrain, pons, medulla oblongata
-through 3 different secondary vesicles (mes-, met-, and myel- encephalons)
The cerebellum is part of the myelencephalon, true or false?
FALSE
METencephalon
Around which week do the primary brain vesicles derive the secondary brain vesicles?
WEEK 5
pro > tel and dien
mes > mes and met
rhomb > met and myel
(-encephalon after each)
The fourth ventricle connects to the third ventricle via tiny narrowing called _____
the aqueduct of the midbrain
Name the ventricles of the brain
Lateral ventricles ("1 and 2")
Interventricular foramen
Third ventricle
Aqueduct of midbrain
Fourth ventricle
contain CSF
Lateral ventricles
two largest cavities of ventricular system of brain in each cerebral hemisphere (inside cerebrum)
contain CSF
What connects the lateral and third ventricles?
interventricular foramen
Myelencephalon formation
MEDULLA OBLONGATA (brain stem)
- shift of medulla walls changes position of plates so basal plates (motor) become medial to alar plates (sensory)
- roof plate moves laterally to make room for 4th ventricle
- cells in alar plate cluster to form 3 bilateral cell columns = afferent (sensory) nuclei
- cell bodies in basal plate also cluster to form 3 bilateral cell columns = efferent (motor) nuclei
Metencephalon development
PONS (brain stem)
-cell bodies in basal plate cluster to form 3 bilateral cell columns = efferent (motor) nuclei
-cell bodies in alar plate cluster to form 3 bilateral cell columns =
afferent (sensory) nuclei
MARGINAL LAYER BIGGER (increases/grows)
Why is the marginal layer bigger going from the myelencephalon (medulla) to the metencephalon (pons)?
Cerebellum develops posterior to the pons (sits directly behind the pons)
marginal layer filled with oligodendrocytes surrounding axons that communicate from cerebellum into cerebrum and spinal cord (exiting in pons = BRIDGE)
Mesencephalon development
Basal plate contains two groups of motor nuclei
-Marginal layer of basal plate enlarges to form crus cerebri
Alar plate (sensory) initially two longitudinal elevations -Eventually divides into superior & inferior colliculi
crus cerebri
marginal layer of basal plates enlarged, efferent neurons travel down them
MESENCEPHALON midbrain
superior & inferior colliculi
relay centers in mesencephalon
Diencephalon
Contains Thalamus, Hypothalamus, and Epithalamus
-three pairs of swellings in lateral wall of 3rd ventricle
epithalamus is formed in diencephalon from ______
caudal part of roof plate
Alar plates in diencephalon form which structures
Thalamus and hypothalamus
Telencephalon/Cerebrum
forms two cerebral hemispheres, contains 2 lateral ventricles
-surface grows rapidly to form lobes as well as gyri (elevations) separated by fissures (deep grooves) and sulci (shallow grooves)
Visceral or autonomic NS still has visceral afferents, true or false?
true, just smaller portion
sympathetic and parasympathetic branches of autonomic/visceral NS are OUTPUT
sympathetic chain is in the ____ NS, and has two connections from the ____ that connect to the sympathetic trunk at the ____
PNS anterior rami (VENTRAL-motor efferent)
sympathetic chain ganglia
-part of autonomic or visceral NS
preganglionic parasympathetic cell bodies are located in
brainstem or spinal cord
- CNs cranial nerves (CNS nuclei)
- S2-S4 (craniosacral)
sympathetic preganglionic cell bodies are located in
spinal cord
Thoracolumbar
T1-L2
postganglionic sympathetic cell bodies are located in
sympathetic chain ganglia
or
collateral (prevertebral) ganglia (via splanchnic nerves)
postganglionic parasympathetic
- think parasympathetic: craniosacral
- 4 cranial ganglia
- AND in the walls of the organs they innervate (ganglia with organs)
