Download Neurology Midterm

Neurology Midterm
Summer 2009
Cerebrum
Largest single component of human brain
Diencephalon
Anything containing something called
thalamus
Brainstem
Where the brain gets narrow
Midbrain
Cranial part of the brain stem
Pons
Middle part of the brain stem
Cerebellum
Sits behind the pons
Medulla oblongata
Caudal part of the brain stem. Continues as
spinal cord
Brain
Everything enclosed in the skull (brain
stem is part of the brain)
Cervical, thoracic, lumbar, sacral,
coccygeal nerves
Nerves coming off the spinal cord are
named by the portion of the boney spine
they exit
Cervical curve
Lordotic. C1-C7. Spinal nerves C1 thru
C8 (one more cervical nerve than bone)
Thoracic curve
Kyphotic. T1-T12. Spinal nerves T1 thru
T12.
Lumbar curve
Lordotic. L1 thru L5. Spinal nerves L1
thru L5.
Sacral curve
Kyphotic. Sacrum and coccyx. Spinal
nerves S1 thru S5 and Cox 1.
Central Nervous System (CNS)
Brain and spinal nerves. That part of the
nervous system that is encased in bone
(skull and bony spine).
Peripheral Nervous System (PNS)
Nerves coming off of CNS – Cranial and
spinal nerves.
Cranial nerves
Twelve pair designated I thru XII
Spinal Nerves
31 pair - 8 cervical: C1 exits above C1 bone. C2
above C2 bone down to C7. C8 exits
below C7 / above T1
- 12 thoracic: Exit below named vertebrae.
- 5 lumbar: exit below named vertebrae.
- 5 sacral: S1 thru S4 nerves exit below
named segment thru anterior and posterior
foramen
- S5 and 1 coccygeal nerve: Exits thru
sacral hiatus
Neural tube
Hollow structure formed from ectoderm
(outer skin of body) in early development
of nervous system.
Forebrain vesicle / prosencephalon
“Top” of brain. Formed from neural tube
in nervous system development.
Midbrain vesicle / mesencephalon
“Middle” of the brain. Formed from neural
tube in nervous system development.
Hindbrain vesicle / rhombencephalon
“Bottom” of the brain. Formed from
neural tube in nervous system
development.
Telencephalon
Develops from the prosencephalon. Most
cranial portion – will turn into cerebrum.
Cerebral hemispheres
Large region. Center of advanced mental
processes. (cerebrum)
Diencephalon
The higher brain in lower organisms.
Things with the word “thalamus” in the
name come from the diencephalon.
Mesencephalon
Remains as structure called “midbrain”
Metencephalon
Develops from the rhombencephalon.
Pons
Sits below the midbrain. From
metencephalon.
Cerebellum
Myelencephalon
Sits behind the pons. From metencephalon
Turns into medulla oblongata.
Remainder of neural tube
Turns into spinal cord
Neurites
Extension off cell body that carries nerve
impulse. Length varies.
Dendrites
By definition, carries nerve impulse toward
cell body. Short multiple neurites.
Axon
By definition, carries nerve impulse away
from cell body. Long single neurite.
Axon hillock
Area of cell body where an axon extends
off cell body. Nissl substance not found at
the hillock.
Sodium Potassium Pump
The physiologic mechanism that all cells of
the body use to keep sodium on the outer
surface of the cell and potassium on the
inner surface. There is always more Na on
outer surface than on the inner surface.
This means that there is a relative positive
charge on the outer surface vs the inner
surface.
Polarization
The term for this normal state of Na on the
outer surface and K on the inner with outer
surface being relatively positive to the
inner surface
Resting membrane potential
-80 mV (with variation). Polarized state
with potential of depolarization.
Depolarization
Momentary disruption of the Na / K pump
in which Na starts to pour into the cell.
This causes a momentary disruption in
which the outer side of the cell membrane
becomes negative relative to the inner
surface. It reverses itself almost
immediately. *nerve impulse
Action Potential
Not exactly the same thing as
depolarization but close enough for our
purposes. Inner membrane is about +40
mV.
Nerve impulse
Series of action potentials (areas of
depolarization traveling down length of
neuron).
Repolarization
Area of depolarized neuron will return to
its normal polarized state almost
immediately.
Refractory period
Period of time when another action
potential cannot be elicited (microsecond).
Absolute refractory period
No matter how strong the stimulus another
AP cannot depolarize the neuron.
Relative refractory period
Period of time toward the end of the
refractory period in which a stronger than
normal stimulus may initiate an action
potential.
Similar to concept of multiple stimuli
depolarizing a neuron at the same time
(domino analogy).
Summation
Myelin sheath
Fatty tissue that surrounds and insulates the
neuron axon. Not found on cell body or
dendrites.
Nodes of Ranvier
Bare areas found along the axon devoid of
myelin.
Salutatory conduction
In myelinated axons, the action potential
jumps from node to node vs traveling down
entire axon.
White matter
Composed of myelinated axons
Gray matter
Composed of unmyelinated cell bodies and
dendrites.
Synapse
Where the above structures meet.
Neurotransmitter
Chemical secreted by one of the structures
that crosses the synaptic cleft and
depolarizes the other structure.
Presynaptic membrane
Little vesicles (bags) that contain the
neurotransmitter and are located in the
presynaptic membrane.
Blood brain barrier
Most substances in blood supply to brain
are unable to exit the capillaries of the
brain itself. Oxygen, carbon, amino acids,
some sugars, and many lipid structures
CAN enter. Higher molecular weight
substances CANNOT. Small things can
enter. Large things cannot.
Capillary endothelium
Helps create blood-brain barrier. Much
tighter cell-to-cell junctions of the single
layers squamous epithelial cells.
Glial Cells
Term means “glue” – the glue that holds
the brain together. Special cells in the CNS
(and PNS to some extent) that function as
white blood cells, connective tissue cells,
etc in the brain. They never cross the
blood-brain barrier to leave brain and help
maintain blood-brain barrier. Total mass of
brain is about 50% glial cells / neuroglial
cells (w variation among texts). Glial cells
outnumber neurons by 5:1 or more.
Astrocytes
Glial Cells: CT, star shaped, perivascular
feet and BB braier. Found in CNS
Fibrous astrocytes
Glial cells in white matter
Protoplasmic astrocytes
Glial cells in gray matter
Oligodendrocytes
Glial cells found along myelinated nerve
and forms the myelin (covering on nerves)
in the CNS
Microglial
Smallest of the glial cells. Inactive most of
the time. They act like WBCs in disease
states. Found in CNS.
Ependymal cells
At least three types, all of which are
involved with cerebrospinal fluid. Found
in CNS.
Schwann cell
Myelin formation in the peripheral nervous
system.
Satellite cell
Wrapped around nerve cell bodies in the
PNS. Acts as connective tissue.
Efferent nerve fibers
Motor from the brain to the body
Afferent nerve fibers
Sensory from the body to the brain
Functions of spinal cord
-
Highway for nerves between the
body and brain
Center for spinal reflexes
Cervical enlargement
C3 to T2. Extra nerves coming off to
supply upper extremities.
Lumbar enlargement
L1 to S3. Extra nerves coming off to
supply the lower extremities.
Cauda equina
Translates to “horse’s tail”. Nerves
become increasingly elongated to reach
their intervertebral foramen level. This
forms a leash of long nerves traveling
inside the spinal canal.
Meninges
Three layers of protective tissue covering
the outside of spinal cord.
Meningeal layers
Drua mater, Arachnoid mater, Pia mater.
These three layers cover the spinal cord for
its entire distance. Each spinal nerve is
covered by extension of drua & arachnoid
Outer layer of meninges. Toughest,
strongest. Attached to inner surface of
skull. “Kinda” attached to vertebrae in
spine.
Spider mother. Thin delicate membrane
Drua mater
Arachnoid (mater)
Subarachnoid space
Space between the pia and arachnoid.
Contains cerebrospinal fluid
Pia mater
Delicate mother – even more delicate than
the arachnoid. Pia is firmly attached to
brain in the skull and spinal cord in spine.
Denticulate ligaments*
Stringlike projections that connect the pia
to the drua. Spinal cord is well anchored
by these ligaments and the cerebrospinal
fluid that helps hold cord in place and
protect it.
Conus medullaris
Bottom of the cord proper. Pointy tip of
the cone. The three layers of meninges and
CSF continue down to S2.
Lumbar cistern
The dural sac that lies below L1 and
contains CSF. “Safe” place to do spinal
tap.
Filum terminale
“Terminal thread.” Extension of pia mater
from the conus medullaris to the coccyx.
This anchors the spinal cord to the tail
bone.
Anterior median fissure
Deep
Posterior median sulcus
Shallow
Spinal nerves
31 pairs. Spinal nerve made up of two
roots coming off the cord that merge to
form a spinal nerve just before it exits the
IVF. The dorsal (posterior) roots are all
sensory and the ventral (anterior) nerves
are all motor which would make the spinal
nerve a “mixed” nerve.
Dorsal root ganglion
Enlargement of the dorsal root. Cell bodies
of all sensory neurons entering the cord at
that level. Ganglion = group of nerve cell
bodies. Motor neurons don not have
ganglia as they eit spinal cord. Their cell
bodies are located in the cord.
Gray matter
Shape of “H” or butterfly. Center of the
cord. Unmyelinated material / nerve cell
bodies, glial cells, dendrites and
unmyelinated association neurons (very
short neurons). Center of all sentient
(awareness) functions.
White matter
Surrounds the gray “H”. Composed of
mylenated axons traveling to and from the
brain….
Motor nerve
Leaving the cord and going to body.
Sensory nerve
Entering cord and leaving body.
Anterior horns
Cell bodies of motor neurons
Posterior horns
Neurites of sensory neurons
Lateral horns
Found only at levels T1 thru L2 and S2
thru S4 where the autonomic nervous
system neurons exit the cord.
Commissures (white and gray)
Areas of crossing of neurons from one side
of the cord to the other. Spinal cord is
bilateral.
Nerve
Groups of axons in the PNS.
Ganglion
Groups of nerve cell bodies in the PNS and
CNS
Tract
Name for nerves as they travel inside the
CNS
Anterior columns (left and right)
White matter (axon pathways) at front of
spinal cord.
Posterior columns (left and right)
(Funiculi) White matter at the back of the
spinal cord.
Lateral columns (left and right)
Right and left sides of the spinal cord.
General neuron pathway
The 1º neuron is peripheral neuron. It
enters cord where it will synapse with 2º
neuron somewhere in the cord. The 2º
neuron will travel up to brain stem where it
will synapse with a 3º neuron (most often
in the thalamus of the diencephalons) that
will run to the postcentral gyrus of the
parietal lobe.
Dermatome / dermatome levels
Area of surface skin supplied by one
specific spinal nerve
Bifurcate
To split into two segments
Decussate
To cross over to opposite side
Ipsilateral
Same side
Contalateral
Opposite side
Special senses
Sight, sound, taste, hearing, balance
Precentral gyrus
Motor. In frontal lobe. Where most of
motor neuron pathways originate
Postcentral gyrus
Sensory. In parietal lobe. Where most
sensory neuron pathways that travel up
spinal cord terminate.
Pain / Temp Pathway (from dermis &
epidermis)
First order neurons enter spinal cord via
dorsal root ganglia of spinal cord. Cell
bodies located in the dorsal root
ganglion. There they synapse with second
order neuron in the posterior (dorsal) horn
of the spinal cord (in the gray H) at the
appropriate dermatome level. The axon of
the second order neuron decussates and
runs up the contralateral side of the spinal
cord. The second order neuron travels up
to the thalamus where it synapses with a 3rd
order neuron. The third order neuron then
travels up to the postcentral gyrus of the
parietal lobe (termination point for sensory
neuron pathways).
Lateral spinothalamic tract*
The pain and temp (sensory) tract that
goes up the lateral white column
Internuncial neuron
Second neuron that synapses in the lateral
spinothalamic tract (ascending pathway) in
the spinal cord. The function of this
second neuron is to form a reflex arc back
to the area of pain and cause muscles in
that area to move the body away from the
source of pain.
Reflex
Subconscious muscular response to a
stimulus. Internuncial neuron is one
example. Associated with pain and
temp!
Internal capsule
In the medulla the lateral spinothalamic
tract picks up other fibers and ascends thru
the pons through this structure. It is a
compacted area of axons going to and from
the cerebral cortex to and from the much
smaller brainstem.
Corona radiata
The radiating out of the axons from the
internal capsule of axons to and from the
cerebral cortex.
Pressure and crude touch pathway (dermis)
First order neuron enters the spinal cord via
the dorsal root ganglion where the cell
bodies are located. When it enters the
dorsal horn it will bifurcate (split) and
90% will enter the dorsal root and synapse
with a second order neuron in the gray H of
the dorsal horn at that dermatome level.
The second part will ascend as much as 10
spinal cord levels via the dorsal white
column and then decussate and enter the
dorsal horn and synapse with the second
order neuron in the gray H. Once the two
have re-joined, they travel together up to
the brain stem where they will synapse
with a third order neuron in the thalamus.
The third order neuron will travel up to the
postcentral gyrus of the parietal lobe (the
termination point for most sensory neuron
pathways)
Ventral spinothalamic tract
The pressure and crude touch (sensory)
tract that goes up the ventral (front) white
column
Fasciculus
Another word for column.
Fasciculus gracilis
The more medial fibers in the dorsal white
column of the spinal cord that contain
axons from the lower portion of the body.
Fasciculus cuneatus
The more lateral fibers in the dorsal white
column of the spinal cord that contain
axons from the upper portion of the body.
Location of proprioception receptors
Muscles, tendons, joints
Location of touch & vibratory sense
receptors
Dermis
Proprioception, fine touch, vibratory sense
pathway
The first order neurons run up the dorsal
white columns (fasciculus gracilis and
cuneatus) to the medulla where they
synapse with second order neuron,
decussate, synapse with a third order
neuron in the thalamus, which then runs up
to the postcentral gyrus of the parietal lobe
(termination point for most sensory neuron
pathways)
Trigeminal nerve
Cranial Nerve 10 (CN V). Carries sensory
information to anterior half of head
Crainial Nerve I
Olfactory – smell
Cranial Nerve II
Optic – sight
Cranial Nerve III
Occulomotor – contract pupil. Stimulates
movement of 4-6 extra ocular muscles.
Cranial Nerve IV
Trochlear – moves eye muscle. One extra
ocular myo. Stimulates movement of
superior oblique
Cranial Nerve V
Trigeminal – sensation to face / chewing
Cranial Nerve VI
Abducens – abducts eye. Stimulates
movement of one extra ocular myo – lateral
rectus
Cranial Nerve VII
Facial – muscles of face (facial expession)
Cranial Nerve VIII
Acoustic / Vestibulocochlear – balance /
hearing
Cranial Nerve IX
Glossopharyngeal – swallow and pharynx
(stimulates stylopharyngeus)
Crainial Nerve X
Vagus – parasympathetic nerve supply
from head to pelvic area (remember
“vagrant” or “vagabond” – someone who
carries a lot of baggage with them).
Stimulates most of the muscles of talking
and swallowing.
Cranial Nerve XI
Accessory / Spinal accessory – accessory to
SCM and trapezius
Crainial Nerve XII
Hypoglossal – tongue. Stimulates all
tongue muscles except the
stylopharyngeus.
Saying to help remember:
On Old Olympus’ Towering Top a Finn
and German Viewed a Hop
Alternative saying to help remember:
Oh, Oh, Oh, To Touch And Feel Vaginas
Gets Vinnie All Hard
Efferent neurons
Brain to body
Motor
Cause an effect like motion of a myo or
secretion of gland, etc
Precentral gyrus
Frontal lobe anterior to central sulcus.
Major center for initiation of voluntary
movement as the postcentral gyrus is for
somatosensory reception.
Upper motor neuron
Starts at the precentral gyrus (or closely
associated region) and travels down to the
cord.
Lower motor neuron
Neurons that synapse with the upper motor
neuron in the anterior horn of the gray H
and travels out into the body.
Cerebellum
Located behind pons
Functions of cerebellum
-
Coordination of voluntary muscle
activity
-
Equilibrium
Muscle tone
Example of injury to cerebellum
Frankenstein
Vestibulo cerebellar tract
Tract tells cerebellum about position of
head and acceleration / deceleration
Cortico ponto cerebellar tract
(cortex pons cerebellum). When cortex
fires off nerve impulse to body, the
cerebellum must know what cortex is
saying to body in order to coordinate the
movement.
How cerebellum works with other
structures:
Somewhere in pons an upper motor nerve
synapses with a second order neuron that
travels to the cerebellum. The above 3
tracts talk to the cerebellum. The
cerebellum now must take that information
and talk to the voluntary muscles of the
body to establish correct muscle tone and
equilibrium. Uses basal ganglion and
vestibular system by the above pathways.
Cerebellum does not serve as reflex center
but reinforces some reflexes while
inhibiting others.
Archicerebellum
Oldest portion of cerebellum. Associated
with vestibular system (earthworm –
balance). Contains flocculonodular lobe
which is composed of paired focculus and
central nodule.
Paleocerebellum
Second oldest portion of cerebellum.
Associated with gross movement of head
and body. (shark – gross movement).
Contains anterior lobe and part of vermus.
Neocerebellum
Newest section of cerebellum. Related to
fine motor skills (primate – fine
movement). Contains the posterior lobe
and most of vermus.
Visceral body
Includes everything not under voluntary
control: seating heart rate, goose bumps,
speed of GI emptying, breathing,
contraction of bladder, etc.
Tissues under autonomic nervous system
control:
ANS divided into two parts with opposite
functions
- Smooth muscle
- Cardiac muscle
- Most glandular tissue (epithelial)
Sympathetic and Parasympathetic.
Systems always work together – never pure
SNS or PSNS.
Sympathetic Nervous System
Dominant system for stressful situations.
Includes both physical and psychological.
(Fight or Flight). Also called catabolic –
burns energy and material.
Parasympathetic Nervous System
Dominant system in conserving energy,
building up body tissue, etc.