Download Neurology—midterm review

Neurology—midterm review
*terms associated with the development of the brain
-neural tube—hollow structure formed from ectoderm that expands into three
primary vesicles
1. forebrain vesicle/prosencephalon—top of the brain, develops into:
*telencephalon—most cranial portion, will turn into cerebrum
-cerebral hemispheres—large region, center of advanced
mental processes
*diencephalon—the higher brain in lower organisms, anything
with “thalamus” in the name comes from the diencephalon
2. midbrain vesicle/mesencephalon—middle of the brain, stays as a
structure called the midbrain
3. hindbrain vesicle/rhombencephalon—bottom of the brain, develops
into:
*metencephalon—leads to the development of the:
-pons—sits below the midbrain
-cerebellum—sits behind the pons
*myelencephalon—turns into the medulla oblongata
*remainder of the neural tube turns into the spinal cord
*names/descriptions/functions of the glial cells (4 found in the brain, 2 found in the
periphery)
-glial cells—glial means “glue,” special cells in CNS (and PNS to some extent)
that function as white blood cells, connective tissue, et cetera in the brain. Never
cross blood-brain barrier and actually help to maintain it
-the total mass of the brain in 50% glial cells
-4 glial cells in the CNS (central nervous system—part of nervous system encased
in skull and bony spine)
1. astrocytes—CT, star shape, perivascular feet and BB barrier
*fibrous astrocytes—in white matter
*protoplasmic astrocytes—in gray matter
2. oligodendrocytes—found along myelinated nerves and forms the
myelin (covering on nerves) in the CNS
3. microglia—smallest of the glial cells, inactive most of the time, act like
WBC’s in disease states (immune response)
4. ependymal cells—at least 3 types, all of which are involved with
cerebrospinal fluid
-2 glial cells found in the PNS (peripheral nervous system—nerves coming off of
the CNS)
1. schwann cell—myelin formation in the PNS
2. satellite cell—wrapped around nerve cell bodies in the PNS
*cerebellum and functions
-cerebellum is located behind the pons, it’s the coordination center for motor
activity and equilibrium
-3 functions
1. coordination of voluntary muscle activity
2. equilibrium
3. muscle tone
*cerebellum doesn’t initiate movement, but fine tunes and modifies it
*cerebellum does NOT serve as a reflex center but instead reinforces some
reflexes while inhibiting others
*Frankenstein monster is a classic example of what a cerebellum injury
would look like
-anatomy of the cerebellum
*archicerebellum—oldest portion, associated with the vestibular system
*paleocerebellum—second oldest, related to gross movement of the head
and body
*neocerebellum—newest section, related to fine motor skills
*3 meninges—3 layers of protective tissue that cover the brain and spinal cord
-the 3 layers of meninges and the CSF (cerebrospinal fluid) continue down to
about the level of S2
1. dura mater—means “tough mother,” the outer, strongest layer
*in the skull attached to the inner surface of the skull
*in the spine “kinda” attached to vertebrae (foramen magnum and sacrum
at S2)
2. arachnoid mater—spider mother, thin delicate membrane
*subarachnoid space—space between the arachnoid and the pia and
contains cerebrospinal fluid
3. pia mater—delicate mother, even more delicate than the arachnoid
*firmly attached to the brain in the skull and the spinal cord in the spine
*structures that hold the spinal cord in place
-inner diameter of bony spinal column is about the diameter of an index finger
-spinal cord is about the diameter of a pencil
-the bony spine outgrows the spinal cord (stops at L2)
-denticulate ligaments—string like projections that connect the pia to the dura
(these and the cerebrospinal fluid help hold the cord in place and protect it)
-conus medullaris—bottom of the cord proper, the pointy tip
-lumbar cistern—the dural sac below L1 that contains CSF
-filum terminale—means “terminal thread,” extension of the pia mater from the
conus medullaris to the coccyx, this anchors the spinal cord to the tail bone
*spinal cord
-spinal cord—everything enclosed in the bony spine
-cone shaped (wide at one end and tapers down to a point at the other end)
-begins at C1 and ends at about L2
-cervical enlargement—C3 to T2, extra nerves coming off to supply the upper
extremities
-lumbar enlargement—L1 to S3, extra nerves coming off to supply the lower
extremities
-cauda equine—means “horses tail,” nerves become increasingly elongated to
reach their intervertebral foramen level, this forms a leash of long nerves traveling
inside the spinal cord
-dorsal root ganglion—an enlargement of the dorsal roots, cell bodies of all the
sensory neurons entering the cord at that level
*spinal cord terminology
-anterior median fissure—deep
-posterior median sulcus—shallow
-gray H—center of the cord, unmyelinated material/nerve cell bodies, glial cells,
dendrites, and unmyelinated association neurons
*anterior horns of the gray H—cell bodies, et cetera of motor neurons
*posterior horns of the gray H—neurites (extensions off the cell body
that carry the nerve impulse) of sensory neurons
-dorsal and ventral roots
*a spinal nerve is made up of two roots coming off the cord that merge to
form a spinal nerve just before it exits the intervertebral foramen
*dorsal (posterior) roots—sensory (same as in gray H)
*ventral (anterior) roots—motor (same as in gray H)
-white matter of the spinal cord
*surrounds the gray H, composed of mylinated axons traveling to and
from the brain
*divided up into areas called columns or funiculi for descriptive purposes
*ventral (anterior) columns—L and R, white matter (axon pathways) at
the front of the spinal cord
*lateral columns—L and R, left and right sides of the spinal cord
*dorsal (posterior) columns—L and R, here we usually use the term
“funiculi,” back of the spinal cord
-tract—one of the many names for nerves as the travel inside the CNS
-ganglion—a group of nerve cell bodies in the PNS and CNS
*Cranial nerve numbers, names, functions
-On old Olympus’s towering top a Finn and German viewed a hop
-CN I—Olfactory, smell (On)
-CN II—Optic, sight (Old)
-CN III—Occulomotor, moves the eyeball (Olympus’s)
-CN IV—Trochlear, one muscle that moves the eyeball (Towering)
-CN V—Trigeminal, chewing and feeling the face (Top)
-CN VI—Abducens, one muscle that moves the eye (A)
-CN VII—Facial, moves the face (Finn)
-CN VIII—Acoustic (aka vestibulochochlear), hearing and balance (And)
-CN IX—Glossophyarngeal, stimulates one muscle the stylopharyngeus
(German)
-CN X—Vagus, carries parasympathetic nerves down the trunk and stimulates
muscles of talking and swallowing (Viewed)
-CN XI—Accessory (aka spinal accessory), stimulates sternocleidomastoid
muscle and upper traps (A, or Some)
-CN XII—Hypoglossal, stimulates tongues muscles (Hop)
*pathways for pain and temperature/pressure and crude touch/proprioception, fine touch
and vibratory sense
-pain and temperature pathways (from the dermis and epidermis)
*aka “lateral spinothalamic tract”
*reflex—subconscious muscular response to stimulus
*this pathway is distinct from the other two in that in synapses with
another neuron in the cord (internuncial neuron) which functions to form a
reflex arc back to the area of pain and causes the body to move away from
the source of pain
-pressure and crude touch (from the dermis)
*when the 1º neuron enters the dorsal horn, it will bifurcate (split)
-90% does same thing as in pain and temperature pathways
-10% ascends the cord via the dorsal white column then enters to
the dorsal horn to synapse with a 2º neuron
-proprioception, fine touch and vibratory sense
*these pathways take up the entire dorsal white columns of the spinal cord
*unlike the other two pathways, this one does not have a 2º neuron in the
spinal cord, instead the 1º neurons synapse with the 2º in the medulla)
The following notes were organized from the week 1 and 2 review guides that Doc gave
us. Plenty of terms and concepts to be found!
*efferent-vs-afferent nerves
-efferent/motor nerves—travel from brain to the body (cause a motor effect in
the body, so they are efferent)
-afferent/sensory nerves—travel from the body to the brain
*3 terms to describe nerve coverings (not myelin) of a peripheral nerve
-nerve fibers travel in groups called nerves
1. epineurium—connective tissue wrapped around a nerve (outermost of these 3,
like epidermis is the outermost layer of skin)
2. perineurium—protective sheath of connective tissue around the bundles of
nerve fibers known as fascicles
3. endoneurium—delicate connective tissue that wraps around each individual
nerve fiber (innermost of these 3)
*major brain structures and locations
-brain—everything enclosed in the skull and the brain stem
-cerebrum—largest single component of the human brain, made up of 4 large
lobes (frontal, parietal, occipital, temporal)
-diencephalon—anything containing the thalamus (buried deep inside the lower
part of the cerebrum)
-brainstem—where the brain gets narrow
*midbrain—cranial part of the brainstem
*pons—middle part of the brainstem
*cerebellum—sits behind the pons
*medulla oblongata—caudal (lowest, most inferior) part of the brainstem
*blood-brain barrier definition and function
-blood-brain barrier—most substances in the blood supply to the brain are
unable to exit the capillaries of the brain itself (smaller, more lipid-soluble
substances like O2, CO2, amino acids, some sugars can pass through the
capillaries into the brain while larger, more water soluble substances cannot)
-2 things that help create blood-brain barrier
1. capillary endothelium—much tighter cell to cell junctions of the
epithelial cells
2. astrocyte—the type of glial cell that helps to maintain the blood-brain
barrier
*bony spine curves, number of bones in each region
-cervical curve—lordotic, C1 through C7, 7 bones
-thoracic curve—kyphotic, T1 through T12, 12 bones
-lumbar curve—lordotic, L1 through L5, 5 bones
-sacral curve—kyphotic, sacrum (5 bones fused together) and coxxyx (number of
bones fused together varies)
*spinal nerves (31 pairs)
-names (follow the spine) and how the nerves exit the bony spine (the name of the
hole through which they exit is the intervertebral foramen)
*8 cervical—spinal nerves C1 through C8
-C1 exits above C1 bone, C2 above C2 bone and so on down to
C7, then C8 exits below C7
*12 thoracic—spinal nerves T1 through T12
-exit below named vertebrae
*5 lumbar—spinal nerves L1 through L5
-exit below named vertebrae
*5 sacral—spinal nerves S1 through S5
-S1 through S4 nerves exit below named segment through an
anterior and posterior foramen, S5 exits through the sacral hiatus
*1 coccygeal—spinal nerve Cox1
-exits through the sacral hiatus
*vertebral foramen-vs-intervertebral foramen
-vertebral foramen—opening that allows passage of the spinal cord
-intervertebral foramen—opening that allows the passage of spinal nerves
*myelin covering of the nerves
-myelin sheath—fatty tissue that surrounds and insulates the neuron axon, not
found on the cell body or dendrites
-nodes of ranvier—bare areas found along the axon devoid of myelin
-salutatory conduction—in myelinated axons, the action potential
(depolarization) jumps from node to node instead of traveling down the entire
axon
-white matter—composed of myelinated axons (fat is white)
-gray matter—composed of unmyelinated cell bodies and dendrites (has a darker
color)
-speed of nerve transmission
*unmyelinated nerve impulse—1 m/sec
*myelinated nerve impulse—100 m/sec (speeds things up by a factor of
100 times)
*microscopic neuroanatomy
-neuron—a single nerve cell which usually contains the following structures
*cell body—where you find most of the things you find in any other cell
*axon—carries a nerve impulse away from the cell body and is a long
single neurite (extension off the cell body that carries nerve impulse)
*dendrite—carries a nerve impulse toward the cell body and has short
multiple neurites
*nissl substance—large numbers of RER granules to reflect all the
protein synthesis activity in the neuron
*axon hillock—area of the cell body where an axon extends off the cell
body, nissl substance is not found at the axon hillock
*appearance of of multipolar, bipolar, and unipolar neurons
-multipolar neuron—multiple dendrites attached to the cell body and one long
axon on the other end
-bipolar neuron—two extensions from the cell body, one axon and one dendrite
-unipolar—a single axon attached to the cell body
*neuron physiology
-cells of the body are polarized—plasma membrane is positive on outside surface
and negative on the inside surface
-Sodium-Potassium pump—physiological mechanism used by the cells of the
body to keep Na on the outer cell surface (positive) and K on the inner surface
(negative)
-resting membrane potential—similar to polarization, the normal state of Na
on the outer surface and K on the inner with the outer surface being relatively
more positive to the inner surface, -80 mV, potential energy, the neuron is
polarized so it can depolarize
-action potential—similar to depolarization, a momentary disruption of the
Na/K pump in which Na starts to pour into the cell causing the outer side of the
cell membrane to become negative relative to the inner surface, inner membrane
is now about +40 mV, kinetic energy
-nerve impulse—series of action potentials (areas of depolarization traveling
down the length of a neuron
-repolarization—area of depolarized neuron will return to its normal polarized
state almost immediately
-refractory period—period of time in which another action potential cannot be
elicited
*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
-domino analogy of nerve impulse—tipping the first domino in a line starts a
chain reaction knocking over each succeeding domino, a nerve impulse is a wave
of depolarizion traveling the length of the neuron turned on by anything that
momentarily disrupts the Na/K pump
*terms
-thalamus—a section of the diencephalon, a relay point for almost all sensory
nerve pathways from the body to the postcentral gyrus of the parietal lobe
-diencephalon—buried deep in the cerebrum, first structure below cerebrum,
contains the thalamus
-brainstem—where the brain gets narrow, includes midbrain, pons, medulla
oblongata
-3 types of fibers (axons) located in the cerebrum
-projection fibers—refers to the afferent/sensory and efferent/motor
fibers going to and from the cerebrum
-association/associative fibers—connect areas in the same hemisphere
-commissural fibers—side to side of the two hemispheres of the
cerebrum
-precentral gyrus
*motor, everything we do
*in the frontal lobe, where most of the motor neuron pathways originate
-postcentral gyrus
*sensory, everything we feel
*in the parietal lobe, where most of the sensory neuron pathways that
travel up the spinal cord will terminate
-2 fissures and a sulcus
*median longitudinal fissure—separates the two halves of the brain
*lateral fissure—separates temporal lobe below from the frontal and
parietal above
*central sulcus—separates the frontal and parietal lobes
-special senses—sight, smell, taste, hearing, balance
-contralateral—opposite side
-ipisilateral—the same side
-decussate—to cross over to the opposite side
-bifurcate—to split into two segments
-vibratory sense—exactly what it sounds like
-proprioception—knowing your location in space, a function of nerve receptors
in muscles/tendons/joints
-stereognosis—identification of 3D by touch
-two point discrimination—ability to distinguish being touched by two objectsvs-one
-fine touch—being able to identify an object simply by feeling it, mostly
restricted to fingertips, somewhat less by lips and tongue
-crude touch—aware of being touched by an object, but not being able to identify
it simply by touch, level of touch over most of the body
-pressure—light to heavy touch
-dermatomes/dermatome levels—area of skin surface supplied by one specific
spinal nerve
-exteroceptive—sensation from outside the body (the sensation is external)
-proprioceptive—sensation from inside the body, gives us our “location in
space”
*ascending nerve pathway terminology and general layout of sensory input from the body
-a three neuron system from start to finish
-first order neuron—body to spinal cord, a peripheral neuron
-second order neuron—spinal cord to the thalamus
-third order neuron—thalamus to gray matter of the brain
-the thalamus will be the most likely site of synapse between the second and third
order neurons
-postcentral gyrus (of the parietal lobe)—the final destination for the 3º neuron,
a major sensory center for conscious sensation
-The peripheral 1º neuron enters the cord where it will synapse with a 2º neuron
somewhere in the cord (most of the time). The 2º neuron will then travel up to the
brain stem where it will synapse (most often in the thalamus of the diencephalon)
with a 3º neuron that runs to the postcentral gyrus of the parietal lobe.
*cerebral terms
-cerebral cortex—outer few millimeters of the cerebrum, gray matter
-gyrus—surface convolutions that give the brain more room for gray matter
*sulcus—the shallow “valleys between the hills” (hills are called gyri)
*fissures—the deeper valleys
-4 lobes of the cerebrum
1. frontal lobe—the most anterior lobe of the brain
2. parietal lobe—the middle lobe (between the frontal lobe in front and
the occipital lobe behind)
3. occipital lobe—the most posterior lobe
4. temporal lobe—on the side of the cerebrum below the other lobes
-4 dividers
1. middle/median longitudinal fissure—divides the cerebrum into
identical right and left halves
2. central sulcus—divides the frontal lobe from the parietal lobe
3.parieto-occipital sulcus—divides the parietal from the occipital
4. lateral fissure—runs below the frontal and parietal and separates them
from the temporal lobe below
*sulcus is more shallow than fissure, but terms are mostly interchangeable
-internal capsule and corona radiata
*I didn’t find specific definitions for these in the notes from Doc, but a
reference to them under projection fibers as well as a few notes I took in
class and definitions I found online
*projection fibers—the afferent and efferent fibers traveling to and from
the cerebrum (in structures called the internal capsule, corona radiata, et
cetera
*corona radiata—means “radiating crown,” the bundle of white fibers
which spreads out like a fan and connects the cortex of the brain with the
basal ganglia and spinal cord
*internal capsule—where the fibers squeeze together, proceeding
downward from the cortex the corona radiata becomes smaller and forms a
band called the internal capsule that separates the caudate nucleus and the
thalamus from the lenticular nucleus