Exam I - Units I, II, & III

the nervous system plays a dominant role in

coordination, association, and integration of body responses to internal and external demand
cost of specialization is high

mature nervous tissue

has little capacity to store oxygen or glucose, maintains little mitotic capacity

not every cell or tissue of the body is

directly "wired" into the nervous system

neuroanatomy definition

study of structure

chiropractic work

directly influences anatomy to change

neurophysiology

studies the function of the nervous system

neuropathology

studies diseases associated with the nervous system

the CNS consists of what 2 structures

brain and spinal cord

how many cranial nerves are there?

12 pairs

how many spinal nerves are there?

31 pairs

what are ganglia?

groups of neuron cell bodies clustered together in the PNS

anatomical subdivisions

central and peripheral

functional subdivisions

somatic and autonomic

somatic component of NS

part of the NS that innervates skeletal musculature
voluntary component
includes both efferent and afferent nerve fibers, efferent emphasized
involves both CNS and PNS
axon endings are cholinergic(release ach), only action is being excitatory

efferent/motor

outgoing from CNS

afferent/sensory

incoming towards CNS

autonomic part of NS (ANS)

innervates the glandular epithelum, smooth, and cardiac musculature
involuntary
involves both CNS and PNS
uses 2 efferent neurons and 1 afferent neuron
parasympathetic subdivision of visceral component of NS

parasympathetic subdivision of visceral nervous system

rest and digest, cholinergic system
slows heart rate, speeds up peristalsis, constricts the pupil and respiratory tree

craniosacral subdivision of parasympathetic subdivision of visceral NS

nerves limited to C3,C4, C9, C10 and S2, S3, S4

nerve fibers of parasympathetic subdivision

2 efferent neurons used
preganglionic- 1st, long, cholinergic
postganglionic- 2nd, short, cholinergic

sympathetic subdivision of visceral nervous system

fight or flight, adrenergic system
speeds up heart rate, decreases peristalsis, dilates pupil and respiratory tree

nerves of the sympathetic subdivision

2 efferent neurons used
preganglionic- 1st, short, cholinergic
postganglionic- 2nd, long, adrenergic
exceptions: ach released at target in sweat glands and arrector pili muscles

parasympathetic vs sympathetic

often (not always) have opposite effects on the same organ/muscle (antagonists)

actions of the sympathetic are more widespread because

the ratio of pre:post ganglionic neurons- sympathetic ratio is 1:17, parasympathetic ratio is 1:2
parasympathetic is more limited and precise

how many nervous system are there?

1

there are 2 neurons in an ANS series and where do they synapse?

in a ganglion

what is week 1 called and what develops?

pre-embryonic stage, zygote, morula, blastocyst, inner/outer cell mass form

what forms in week 2?

bilaminar disc (ectoderm and endoderm), primitive streak(node, pit, groove), mesoderm

what forms in week 3 ?

notochord(primary and definitive), neural plate (fold, groove), neural crest and tube

the neural tube becomes

the 3 primary brain vesicles and the spinal cord

3 primary brain vesicles

prosencephalon - forebrain
mesencephalon- midbrain
rhombencephalon- hindbrain

prosencephalon gives way to the

telencephalon- cerebral cortex, basal ganglia, lateral ventricles
diancephalon- thalamus, hypothalamus, pineal gland, 3rd ventricle

mesencephalon gives way to the

nothing, it stays the mesencephalon

rhombencephalon gives way to the

metencephalon- cerebellum, pons, 4th ventricle
myelencephalon- m.o., 4th ventricle, continuous with spinal cord

the brain in the adult is how heavy and uses how much oxygen?

2-2.5% body weight, uses 20% O2

the brain takes how much of the normal cardiac output?

14-17% when at rest

the brain is responsible for __ of the body's total metabolic activity

15%

neural plate becomes the

neural tube

neural crest folds become the

neural crest cells

neuroepithelial cells give rise to

neuroblasts, ependymal cells, glioblasts

glioblasts

undifferentiated cells, and undergo mitosis, give rise to astrocytes and oligodendrocytes
functional connective tissue of CNS- help guide neurons to proper positions during early development
5-10x more glioblasts than neurons

astrocytes

most numerous cell of adult CNS, maintain mobility potential
ubiquitous structural support cells, sandwiched between blood vessel capillaries and neuron cell bodies, said as part of the BBB (don't form it, but make it function)
2 types - protoplasmic and fibrous
stores excess glucose in CNS
dominant role in forming scar tissue
may directly influence neurotransmitters at synaptic gaps

protoplasmic astrocytes

present in gray matter

fibrous astrocytes

present in white matter

oligodendrocytes

numerous, less amount than astrocytes
perineuronal- found in gray matter, function unclear- may serve nutrient role in CNS
interfascicular- found in white matter, form myelin sheaths around most CNS neuron axons

ependymal cells

line central canal and ventricles of CNS, leaky barrier between CSF and CNS parenchyma
most are simple cuboidal, some taller cells with microvillus borders are present in all 4 ventricles- secrete csf and form choroid plexus in ventricles
cilia present only at young age, go away with age

tanycytes

an ependymal cell only present in 3rd ventricle
help transport csf to hypophyseal portal system

glioma

used to classify solid tumors derived from glioblasts, astrocytes, or oligodendrocytes

astrocytoma

composed of astrocytes, malignant

glioblastoma

composed of glioblasts, most common and lethal primary brain tumor

ependymoma

composed of ependymal cells

less common gliomas

oligodendrogliomas, oligoastrocytomas, gliosarcomas, choriod plexus tumors

white matter

has lots of activity and information passing through
axons grouped together in the CNS

gray matter

synapses firing off

microglia

mesodermally derived, arise from fetal macrophages and invade from bloodstream during embryonic and fetal development
very tiny and have many processes in resting state
become activated when neural tissue is injured
only cells in CNS that can be productively infected by HIV- they then infect other cells

functions of microglia

phagocytic- responsible for clearing dead and damaged tissue, may wall off damaged areas with astrocytes
mediate immune responses within CNS

neuroblast

neuroepithelial origins (along neural tube), show little mitotic activity but undergo growth/maturation and adaption
depend on glial cells to help guide them as they migrate and spread through CNS
radiation and alcohol exposure can cause under/over shooting of designated targets

dorsal root ganglia

autonomic ganglionic cells

neuron doctrine

coined in 1891 by wilhem von waldeyer
neuron is the genetic, anatomical, and functional unit of the nervous system

neuron classifications

anatomical and physiological

anatomical neurons

based on appearance - unipolar, bipolar, multipolar

physiological neurons

based on function - sensory, motor, internuncial

how many axons can a neuron have?

only 1

how many dendrites can a neuron have?

as many as it wants

unipolar neurons

1 dendrite and 1 axon enter/exit at same place, found in dorsal root ganglia

bipolar neurons

1 dendrite and 1 axon attach to cell body on opposite ends
used for senses including smell, vision, hearing, and equilibrium

multipolar neurons

most abundant, golgi type I- long axon, golgi type II - short axon
the axon can have multiple branches coming off of it
multiple dendrites and 1 axon

where is the cell body in sensory neurons?

in the PNS

internuncial neurons

entirely within CNS structures- messengers
messengers/connectors between incoming sensory and outgoing motor neurons

commisural neuron

runs between equivalent structures on opposite sides of CNS e.g. left pre central gyrus to right pre central gyrus

projection neuron

begins in 1 structure and terminates in another within the CNS

ipsilateral

stays on the same side of cerebellum
e.g. left side of pons to left side of midbrain

contralateral

crosses to opposite side of cerebellum
e.g. right side of cerebellum to left side of midbrain

intra segmental

internuncial neuron in spinal cord that begins and ends at the same cord level

inter segmental

internuncial neuron in spinal cord that beings in one cord level and terminates at another

what is the diameter of a neuron's perikaryon?

between 4-130μ (microns)

what shapes do perikarya take?

star, round, oval, pyramidal, fusiform(football)

how long can a process be?

between a few microns (μ) - 40" in adult humans
variable depending on characteristics such as height

what structures meet to form a synapse in the CNS?

axoaxonic (lease common), axodedritic (most common),axosomatic

what are typical organelles and structures found in a neuron?

cell membrane, nucleus, nucleolus, mitochondria, golgi apparatus, ER and ribosomes, centrosome, barr body

why have a nucleus or centrosome if there's little to no cell division?

because they were undergoing division at some point and they have more functions than mitosis
e.g. nucleus acts as a control center

where are mitochondria most abundant?

the cell body and telodendria

what are Nissl Bodies (tigrid bodies)?

clumps of rough ER, free ribosomes, and iron deposits
found in dedrites and cell body only

function of Nissl bodies

chromatolysis- respond quickly to injured neurons and appear to dissolve, but they actually disperse and don't dissolve
often confused with retispersion

retispersion

fragmentation of the golgi apparatus when neurons are damaged
often confused with chromatolysis

are neurofibrils real?

yes, there are 3 types that are hollow, filamentous, and made of protein units, constitute about 25% of dry weight of a neuron's cytoplasm

microtubules

largest neurofibril, help maintain cell shape and have diameter between 20-30nm

microfilaments

smallest neurofibril, run longitudinally and circumferentially, are often associated with the axolemma (3-5nm)

neurofilaments

moderate diameter filaments, 9-10nm

what is axoplasmic cell transport?

the movement of raw materials within the cell
slow and fast

slow axoplasmic transport (boat)

intracellular, move protein blocks and mitochondria,
slow, moving only 0.1-3 mm/day, no atp
occurs in anterograde direction (forward, away from cell body)
speed directly related to axon length
boat- no energy needed but goes slow and only 1 direction

fast axoplasmic transport (airplane)

intracellular, move synaptic vesicles, lysosomes, enzymes
fast, moving 100-400 mm/day, atp needed
can occur in both anterograde or retrograde directions
speed not related to axon length
airplane- requires energy but goes faster and 2 ways

axoplasmic transport as involved in subluxation

what chiropractors do for a living, live in manipulating subluxations

neuron

anatomical and functional unit of nervous system
each neuron is a single nerve cell

neuron process

an extension of neuron away from cell body
ex. axons and dendrites

dendrite

neuron process conducting an impulse (or charge) toward cell body, there can be several
- carry info toward cell body
there can be as many as it wants

axon

single neuron process carrying impulse away from cell body toward synaptic or neuromuscular junction
- carry info away from cell body
- can only have 1
secretory in nature- neurotransmitters, neurohormones, co-transmitters, and more

neurochemicals

create excitatory or inhibitory influences on target sites (or play a modulating role)
brain disorders associated with over/under production (parkinson's, and huntington's chorea)
drugs and neurotoxins may act on these or their target sites

common CNS neurotransmitters include

ach, norepinephrine, dopamine, serotonin, gaba, glycine, glutamate

what was the first neurotransmitter identified?

acetylcholine