Overview of the Nervous System and the CNS Flashcards
central nervous syst
the brain and spinal cord
integration/command center
peripheral nervous system
axons outside the CNS
PNS sensory/afferent fibers
carry impulses from skin, muscles, joints, special senses (somatic afferent), and visceral organs (visceral afferent) to the brain
PNS motor/efferent fibers
exit the CNS to the effectors
PNS motor/efferent SOMATIC
somatic motor fibers for voluntary ctrl of skel muscles
PNS motor/efferent AUTONOMIC
visceral nerve fibers for involuntary ctrl of smooth muscle, cardiac muscle, and glands
sympathetic
parasympathetic
how the nervous system communicates
thru electrical and chemical signals that are rapid and specific and usually cause immediate response
CNS neuroglia ASTROCYTES
highly branched star cells
most abundant and versatile
cling to neurons and synaptic endings, cover capillaries they support the neurons and anchor them to nutrient supplies
ctrl chem envt by regulating ionic composition of CNS extracellular fluid
can pick up neurotrans and remove them from synapse
CNS neuroglia MICROGLIA
brain macrophages that monitor the health of neurons and clean up the micro organisms (immune funct) or dead nerve cell debris
there are no _________ in the CNS so the brain needs microglia
T or B cells
CNS neuroglia EPENDYMAL CELLS
line the central cavities of the brain/cord
some are ciliated to help circulate CSF
CNS neuroglia OLIGODENDROCYTES
branched cells that wrap CNS nerve fibers and produce myelin sheaths around many axons
PNS neruoglia SCHWANN CELLS
surround and form myelin sheaths in PNS fibers
PNS neuroglia SATELLITE CELLS
thought to act as PNS astrocytes
found around neurons in cord (dorsal root ganglion), autonomic ganglia, and schwann cells
cell body
major biosynthetic center contains nucleus, nucleolus, well dev nissl bodies (rough ER), and axon hillock
it is the focal pt for outgrowth of neuronal processes
clusters of CNS cell bodies
nucleus
clusters of PNS cell bodies
ganglion
dendrites
short branched processes that provide enormous surface area for receiving signals from other neurons
axons
long processes that arise from the hillock and ends in many terminals
generates and transmits AP and secretes neurotransmitters at the terminals
bundles of axons in CNS
tract
bundles of axons in PNS
nerves
myelin sheath
whitish fatty protein lipid sheath around most long axons that protects it and electrically insulates from others and increases transmission speed
nodes of ranvier
gaps in the sheath bt adj schwann cells/oligodendrocytes that produce saltatory/jumping of the action potential
where voltage gated Na+ channels are concentrated
myelination in PNS
each schwann cell forms 1 segment as it coils itself around axon w plasma membrane
sheath= concentric layers of membrane
neurilemma=remaining nucleus/cytoplasm that was forced towards the end
CNS myelination
oligodendrocytes coil around up to 6 axons at a time forming segments
lack an outerlayer of perinuclear cyto because cell extensions do coiling and squeezed out cytoplasm is forced back to the centrally located nucleus
myelinated neurons
covered in a whitish protein lipid sheath
unmyelinated neurons
surrounded by a non coiled schwann cell that only lightly covers to protect small diameter axons
causes slower action potential and no jumping
unipolar neurons
single short process that transmits impulses towards the CNS
typically sensory neurons in the skin
bipolar neurons
2 processes an axon and a dendrite
sensory neurons that transmit impulses towards the CNS
found only in retina and olfactory mucosa
multipolar neurons
3+ processes
most common type of neuron, major neuron in CNS
motor neurons+ interneurons that carry impulses away from the CNS
graded potential
ORIGIN: dendrites/cell bodies moves in both directions
TYPE OF CHANNEL: mechanical/chemical
PROPAGATION: small distances/short lived
AMPLITUDE: depend on strength of stimulus no more than 50mv decrease in intensity as carried
POLARITY: hyperpol (inhibits) depol (excites)
Action potential
ORIGIN: axon hillock in one direction TYPE OF CHANNEL: voltage gated Na+ PROPAGATION: long distances- remain strong AMPLITUDE: all or none 100mv POLARITY: depol thru repol phase
conduction velocity of the axon depends on
axon diameter (larger the faster; less resistance) myelination (saltatory conduction; prevents leakage of ions; insulates AP)
synapse
connections bt neurons thru which info flows from one neuron to another presynaptic neuron (release of neurotrans/ info sender) postsynaptic neuron (binds neurotrans/recieves info) results in graded potentials
electrical synapse
common during dev but disappear later in life
connected thru GAP JUNX for extra fast trans
syncronization-important in funct that require instantaneous resp like reflexes and pace makers
chemical syapse
specialized for the release/reception of neurotrans
composed of axon terminal of presynaptic (synaptic vesicles) and the receptor region of post synaptic neurons dendrites
synaptic cleft prevents nerve impulses from directly passing from one neuron to the next (ensures it is a chemical event for unidirectional transfer bt neurons
process of chemical transmission across a synapse
neurotransmitter is released into the synaptic cleft. crosses and binds to receptors of post synaptic neurons
post synaptic neuron membrane permeability changes causing excitatory/inhibitory effect (graded potential)
Excitatory Post Synaptic Potentials (EPSP) graded pot
POLARITY: depolarization
CHANGE IN MM POT: more +
ION MVMT: more Na+ in, less K+ out
CHANCES OF AP: increased
Inhibitory Post Synaptic Potentials (IPSP) graded pot
POLARITY: hyperpolarization
CHANGE IN MM POT: more -
ION MVMT: Cl- in, K+ out
CHANCES OF AP: decreased
EPSP cannot generate a single AP because
it is not enough to reach the threshold need at least 2 or more to reach AP
neurotransmitter
chem used for neuronal communication w the body and brain (language of the nervous system)
excitatory neurotrans cause depol
inhibitory neurotrans cause hyperpol
both cause excitatory/inhibitory
GABA
amino acid
main inhibitory neurotrans of brain
significant mood modulator, helps neurons recover after transmission, reduces anxiety and stress
glutamate
amino acid
main excitatory neurotrans of brain
required for learning and memory
the stroke neurotransmitter
norepinephrine
noradrenaline
biogenic amines excitatory/inhibitory produced by adrenal medulla or dopamine ctrls alertness, rest cycles, attention, and memory concentration as a hormone-fight/flight
serotonin
biogenic amine
inhibitory neurotransmitter
found in platelets, mast cells, and 1-2% in brain
key to feelings of happiness, defends against anxiety, and depression
role in sleep, clotting, appetite, migraines, mood regulation
dopamine
biogenic amine
excitatory/inhibitory feel good neurotrans
in substantia nigra (high melanin cont very dark)
resp for motivation, interest, and drive
positive stress states (sex, love, music, excersise)
works w norepinephrine to supply energy to body in times of stress and delivering messages
increases urine/excess fluid-role in heart failure
nitric oxide
Excitatory gas involved in learning and memory artery dialating properties promotes relaxation of smooth muscle protects artery lining causes damage in strokes used in viagra
neurotransmitters cause their effect on other neurons by
chemically linked receptors (quick)
G-protein linked receptors- receptors+neurotransmitters activate G protein- atp is converted to cAMP
causes slow indirect complex, prolonged responses
termination of neurotransmitters effects are caused by
reuptake
degredation by astrocytes/enzymes
diffusion
ACH can be excitatory or inhibitory because
it depends on the receptor type on the post synaptic neuron
all neurons that stim skel musc are excitatory (nicotinic)
some in ANS can be E or I (muscarinic)
why would a neuron not send an impulse after binding a neurotransmitter
because it might not be enough or it could be inhibitory
gyrus
ridges of the brain that triple the surface area
precentral gyrus
postcentral gyrus
sulcus
shallow grooves
central sulcus- bordered by pre/post central gyri and separates the frontal/parietal lobes
parieto occipital sulcus: separates parietal/occip lobes
lateral sulcus: separates parietal/temporal lobes
fissure
deep grooves
longitudinal fissure: separates hemispheres
transverse fissure: separates hemispheres from cerebellum
deep sulci divide the hemispheres into 5 lobes of the brain
frontal parietal temporal occipital insula (inside)
white matter of the brain
deep myelinated fibers and their tracts
responsible for communication between cerebral cortex and lower CNS center and areas of cerebrum
gray matter of the brain
superficial cortex of cell bodies arranged in 6 layers
has dendrites/glial cells/bv to enable sensation, communication, memory, understanding and voluntary movements
no pain in superficial cortex
gray matter of brain (basal nuclei)
islands of gray matter imbedded deep within the white matter function in muscle tone, attention, cognition, slow movements, habit formation, and role in OCD
white matter in spinal cord
surrounds the gray matter
gray matter in spinal cord
butterfly like central shape surrounded by white matter at its circumference
contains soma, unmyelinated processes, and neuroglia
connected by gray commissure and encloses cc
has 3 horns (dorsal, ventral, lateral)
cerebral hemispheres
CORTEX
WHITE MATTER- commissures, association fibers, projection fibers
BASAL NUCLEI
diencephalon
THALAMUS
EPITHALAMUS
HYPOTHALAMUS
brain stem
MIDBRAIN
PONS
MEDULLA OBLONGATA
cerebellum
arbor vitae
anatomy of cerebral hemispheres
cortex of gray matter, internal white matter, basal nuclei
cerebral dominance
hemisphere that is dominant for language determines which hemisphere is dominant
usually ppl w left cerebral dominance are left handed
cerebral white matter
deep myelinated fibers and their tracts
funct in comm bt cerebral cortex, lower CNS and areas of the cerebrum
tracts classified as commissures, association fibers, and projection fibers
commissures
cerebral white matter tracts that connects the corresponding gray areas of the two hemispheres
association fibers
cerebral white matter tracts that connect different parts of the same hemisphere
projection fibers
cerebral white matter tracts that enter the hemispheres from the lower brain or cord centers
function of basal nuclei
muscle tone
regulation of cognition/attention
ctrl intensity of slow mvmts (arm swinging)
habit formation and ocd
parts of the diencephalon
central core of the forebrain
thalamus, epithalamus, hypothalamus
thalamus
part of diencephalon
inner room/gateway relay station to cerebral cortex
mediates sensation, motor activities, cortical arousal, learning, and memory
hypothalamus
part of diencephalon
most important homeostatic part
loc below the thalamus/caps brain stem
main visceral ctrl center of the body- reg bp, heartbeat, digestion, breathing, hunger, sleep
heart of limbic syst/center for emotional response-pleasure, fear, rage
endocrine funct-release hormones for pituitary, produce ADH and oxytocin
epithalamus
part of diencephalon-most dorsal portion; forms roof of third ventricle
pineal gland secretes melatonin involved w sleep/wake and mood
parts of brain stem
ctrls autonomic behaviors for survival and provides pathway for tracts bt higher and lower brain centers
midbrain
pons
medulla oblongata
midbrain
part of brain stem loc bt diencephalon and pons
cranial nerves III (oculomotor) and IV (trochlear)
cerebral peduncles little feet w motor tracts
corpora quadrigemina- visual reflex, startle reflex, auditory relay center
substantia nigra-linked to basal nuclei
pons
bulging bridge region of the brain stem between midbrain and medulla oblongata
nuclei to ctrl bp
deep fibers- connect higher brain centers w cord
superficial fibers- relay impulses bt motor cortex and cerebellum
cranial nerves V (trigeminal), VI (abducens), VII (facial), VIII (vestibulocochlear)
medulla oblongata
most inferior part of the brain stem
cranial nerves IX (glosopharyngeal), X (vagus), XI (accessory), XII (hypoglossal)
cardiovascular ctrl center, resp center
reg vomiting, hiccupping, swallows, coughs, sneezing
cerebellum
called the small brain
largest part of the brain where activity occurs subconsciously
provides precise timing and approp patterns of skeletal musc contract
blueprint of coordinated mvmt
evaluates how well mvmt initiated by motor areas in cerebrum is carried out
limbic system
primitive emotional brain located on medial aspects of cerebral hemispheres and diencephalon
connected thru fornix
collectively process and experience emotions/ resp to odors
interacts w prefrontal cortex feeling and thought
amygdala-limbic
anger, danger, fear responses
hippocampus-limbic
where memory/new information goes to solidify in permanent storage areas of the cortex
ability to generate new brain cells (neurogenesis)
connected by fornix to other diencephalon limbic system
reticular activating system (RAS)
responsible for alerting the cerebrum to incoming sensory information
keeps cerebrum conscious and alert
filters repetitive and weak stimuli- strong impulses reach consciousness and play role in alertness and sleep
damage can cause irreversible coma
neuroglia
more abundant than neurons
non-neuronal
non-excitable
char of neurons
long lived- 100+yrs w good nutrition
no centrioles-amitotic (except olfactory epithelium+ hippocampus)
high metabolic rate requires high amt 02
plasma memb funct mainly in electrical signaling
produce AP to be carried along length of axon
always the same regardless of stimulus or sorce
most neuron bodies loc in CNS or vert column
to be protected
ElectroEncephaloGram EEG
printed report of the brains electrical activity measured by placing electrodes on the scalp
alpha waves
regular, rhythmic, low amplitude, synchronous waves
in healthy awake but relaxed adults resting with eyes closed
beta waves
rhythmic, less regular waves
occur when mentally alert, concentrating, under stress/tension
theta waves
irregular waves
common in kids, intensely frustrated adults
transient during sleep
delta waves
high amplitude waves of deep sleep
or during anesthesia, or when RAS is damaged
stages of memory
short term/working
long term
short term memory
temporary holding of seven plus/minus one pieces of information
long term memory
limitless capacity of near permanent memory storage
factors affecting stm-ltm transfer
emotional state- alert, motivated, aroused, suprised
rehearsal- repetition and practice
assoc- tied w old memories
automatic-subconcious ltm info
dura mater
strongest meninx- 2 layer fibrous ct
periosteal layer- attached to skull
meningeal layer- external brain covering
arachnoid mater
middle meninx forming loose covering
lg subarachnoid space below filled w CSF and large bv
villi protrude superiorly and allow CSF to be absorbed in venus blood
pia mater
deepest meninx
delicate and transparent
clings tight to brain richly invested w sm bv
functions of the meninges
cover and protect the CNS
protect/enclose bv and sinuses
form partitions in the skull
cerebrospinal fluid
watery solution similar to blood plasma-made from blood filtration in choroid plexus but with less protien and diff ion conc
loc bt arachnoid+pia mater
circulates freely thru ventricles and central canal
bathes outer surfaces of brain and cord
functions of CSF
liquid cushion for buoyancy of CNS organs
reduces brain weight 97% and prevents brain from crushing under its own weight
protects CNS from blows and other trauma
nourishes the brain
blood brain barrier
selective barrier made up of continuous capillaries and astrocytes that make it difficult for chemicals to get into the blood thru plasma memb
shields brain from harmful substances
why is blood brain barrier absent in places like vomiting center and hypothalamus
allows these areas to monitor the chemical composition of the blood
the blood brain barrier is ineffective against substances that can diffuse thru plasmas membranes like
alcohol, nicotine, caffine
and if stressed it is easier for other chemicals to pass thru
functions of the spinal cord
provide 2 way communication to and from the brain
carries sensory info from somatic and autonomic PNS to the brain
carries motor info from brain to effectors
minor reflex center for withdraw and stretch
protections of the spinal cord
bone, meninges, csf
epidural space- fat and veins bt vertebrae and dura mater for cushioning
filum termninale- fibrous extension of the pia mater that anchors the spinal cord to the coccyx
anterior median fissure
separates anterior funiculi
posterior median sulcus
divides posterior funiculi
gray matter
soma, unmyelinated axons, neuroglia
gray commissure connects masses of gray matter and encloses the central canal
posterior dorsal horns
interneurons that carry sensory information
anterior ventral horns
interneurons and somatic motor neurons that carry motor info
lateral horns
only in thoracic and lumbar regions
contain sympathetic nerve fibers
spinal cord ends
L1 or L2
spinal cord size
1-1.5 cm in diameter
43 cm long in women 17 in
45 cm long in men 18 in
conus medullaris
terminal portion of the spinal cord
cauda equina
collection of nerve roots at inferior end of vertical canal
enlargements of the spinal cord
where nerves serving upper and lower limbs emerge
cervical enlargement C3-T1
lumbar enlargement L1-S2
