A&P Exam 4 Flashcards
What is the nervous system
the master controlling and communicating system of the body
structural classification
based on where a component is located
central nervous system
CNS composed of the brain and the spinal chord
acts as an integration and command center
peripheral nervous system
PNS anything outside the CNS mostly nerves (sensory cells) cranial nerves (spinal nerves)
What is the function of nerves
connect the body to the CNS
functional classification
based on how a component is regulated
somatic nervous system
targets the skeletal muscles
under conscious control
autonamic nervous system
targets smooth muscle and cardiac muscle
under unconscious control
neurons
a type of cell present in neural tissue
nervous tissue
highly cellular
high rate of metabolism
needs lots of glucose and O2
poor capacity for repair
what are neurons for
the functional unit of the nervous system
(smallest piece that still works
what is the structure of neurons
large cells with long processes
do not divide (amitotic) (few exceptions)
how many neurons does the body contain
10^12 neurons
where are neurons located
mostly in brain
what is the life of a neuron
long lived
cell body of a neuron
also called the soma
what does the cell body of a neuron do
portion that controls the bulk of the cytoplasm
what does the cell body of a neuron contain
most organelles
dendrites
short branching extensions of a neuron
where do you find dendrites
off of cell body
what are dendrites for
input end of the neuron
axon
long and thin single extension
how long is the axon in a neuron
up to 3 feet long
how many axons in a neuron
only one
what is the axon in the neuron for
output end of the neuron
where is the axon located
arises from the cell body at the axon hillock
what is the plasma membrane of an axon called
axolemma
how many major projections do neurons produce
3 or more (an axon and a cluster of dendrites)
bipolar neurons
optic relay
unipolar neurons
sensory
axon terminals
hold and release neurotransmitters (granules)
where are the axon terminals found
at the distal tip of the axon
where are the axon terminals
at the synapse which is a connection between two neurons
myelin sheath
white fatty segmented layer that can be around an axon
what does the myelin sheath do
electrically omsulates the axon
what is myelin sheet composed of
schwann cells which wrap around axon about 200xs and do not touch neighbors
nodes of Ranvier
spaces between cells in myelin sheath shcwann cells
cell structures particular to a neuron
cell body dendrites axon axon terminals myelin sheath
nucleus
a cluster of neuron cell bodies in CNS
ganglion
a cluster of neuron cell bodies in PNS
TRACT
a bundle of neuron extensions in the CNS
a bundle of axons or long dendrites
nerve
a bundle of neuron extensions in the PNS
white matter
portions of CNS that appear white to the naked eye composed mostly of myelinated axons
gray matter
portions of the CNS composed mostly of cell bodies or unmyelinated axons
where do neurons carry information
to or from the brain
afferent neurons
bring information to brain
efferent neurons
take information out of brain
interneurons
stay within the brain
neuroglia
cells in nervous tissue that support neurons
neuroglia characteristics
smaller than neurons but present in much greater number
astrocytes
found in the CNS most abundant
what do astrocytes to
very versatile
process extracellular fluid
connect neurons to capillary beds
support axonal growth and guidance
microglia
found in the CNS
a type of fixed macrophage
microglia function
immune cells to engulf and destroy
ependymal cells
found in CNS
line fluid filled cavities of brain and spinal chord
ependymal cells
cilia on these cels wave to circulate cerebral spinal fluid
olgodentrocytes
found in CNS
forms the myelin sheath in the brain
satellite cells
in the PNS
surround neuron cell bodies in ganglia
similar in function to astrocytes
schwan cells
in the PNS
wrap tightly around axons in nerves
forms myelin sheaths in PNS
basic principles of electricity
same for both natural and artificial circuits
manmade circuits
we transfer charge using electrons
the human body circuits
transfer charge using ions (electrolytes)
voltage
V measure potential energy of separated charges (+ - )
what does voltage measure in
volts
voltage aka
cell potential or membrane potential
current
I measures the flow of electrical charge from one point to another
what do currents measure in
Amperes
charge
Q measures the total number of charged particles moved by a current
what does charge measure in
coulumbs
resistance
R the hindrance or opposition to the flow of ions
resistance formula
1/R = G = CONDUCTANCE
conductance measure
it’s measures in suemens
what is conductance
how easy it is to flow charge through a channel
ohm’s law
voltage is linked to current resistance
what does ion flow lead to
voltage changes
ohm’s law process
no voltage change without a current
form a current by flowing ions
ions flow through open channels
ion channels in the plasma membrane
allow polar ions to cross the non polar membrane
how are channels named
by the substance that passes through them
or
channels are also named by how they open
examples of naming channels by their substance pass
Sodium channels or glucose channels
examples for channels named by how they open
upon the stimulus that opens them
channel types
ligand-gated
voltage-gated
mechanically-gated
leak
ligan-gated channels
binding of a chemical causes channel to open
different name for logan-gated channels
chemically gated
example of ligand-gated channels
acetylcholine receptor
voltage-gated channels
a large change in charge causes channel to open
example of voltage gated channels
calcium channel in t-tubule
mechanically-gated channels
a physical stimulus opens channel
example of mechanically-gated channels
channel in inner ear
leak channels
always open found on neurons
low conductance
leaks potassium
where is ligand dated channels found
axon dendrites
where are voltage-gated channels
axon hillock
ion movement
ions can cross the plasma membrane when a channel is open ONLY
what direction do ions from when a channel opens
either way in to cell or out of cell
how is the direction of flow predictable
using chemical gradient
electrical influence in predicting flow direction
charge interaction (+, -) opposites attract
chemical influence in predicting flow
concentration gradient - ions diffuse (move to lower concentration)
depolarization
event that moves voltage towards 0mV
hyperpolarization
event that moves voltage away from 0mV
repolarization
event that moves voltage back to its’ original resting value to -70mV
a neuron at rest
a neuron that is not being actively stimulated
sodium-potassium ATP-ase pump
pump is always on
pump establishes an imbalance of ions
pump is electrogenic
what does NA/K ATP-ase pump do at rest
forces out 3 NA while bringing in 2 K at the loss of 1 ATP
cations
possitively charged
anions
negatively charges
A-
large ions organic molecules too bigg to fit through channel
- proteins
- organic acids
- vitamins
Na distribution at rest
inside the cell 15mM
outside cell 140 mM
Potassium distribution at rest
140mM inside cell
5mM outside cell
Cl- distribution at rest
10mM inside cell
120 mM outside cell
A- distribution at rest
100mM inside cell
0.2 mM outside cell
resting cell potential
all gated channels are closed
leak channel is always open
pump is always on
resting voltage sits at -70mV
what will a stimulated neuron produce
an action potential
what is the interior of the cell like
negatively charged
what happens to unpaired ions
get left behind
resting neurons
sit at -70mV
all gated channels are closed and not producing currents
what happens when voltage-gated Na channels open
Na flows in to cell
causes voltage to move from -70mV all the way up to +30mV
What happens when voltage-gated K channels open
changes voltage from +30mV to -75 mV
K efflux
causes a short hyperextension period
- leak channel and NA/K ATP-ase reestablishes resting conditions from -75mV to -70 mV
Action potential conduction
when an action potential is produced it moves along a neuron
where do new axon potentials form at
always at the axon hillock
how do action potentials move
down axon, away from cell body
where does action potential arrive
at axon terminals
signaling strength
action potential does not change - it is all the same size
what do we do since we cannot send bigger action potentials
we must send more of them more often at an increased frequency
conduction velocity
the speed an action potential travels down the axon
factors of conduction velocity
axon diameter
degrees of myelination
axon diameter
bigger has faster conduction velocity
smalles is slower conduction velocity
degree of myelination
more myelin conducts faster
less myelin is slower
it’s possible to have no myelin
saltatory conduction
how an action potential moves down an axon with myelin present
what does myelin do to conduction
myelin increases the resistance of the membrane
forces action potential in to neuron and it travels much faster
how does an action potential travel in myelin
it reappears at plasma membrane in the nodes of Ranvier
action potential is allowed to jump ahead
multiple sclerosis
auto immune disease
what happens with multiple sclerosis
immune system kills schwan cells
causes demylenation of axones
what happens to action potential in multiple sclerosis
slows and can even stop
what does MS cause
causes progressive muscle weakness eventually paralysis
neuron classification
based on conduction velocity
group A fibers
large diameter axons
large amount of myelin
fastest conduction neurons (over 300 mph)
group B fibers
small diameter axons
some myelin
slower conducting neurons (at 30 mph)
what system are group A fibers used by
somatic nervous system
what system does group B fibers use
ANS
group C fibers
smallest diameter axon
no myelin
slowest conducting neurons (2 mph)
what are group C fibers used by
AND in local reflex arcs
synapse
junction between two neurons or between a neuron and muscle cell
electrical synapses
modified gap junctions
common during development
can be in CNS as adults
what do electrical synapses use
channel to allow ions to flow between two cells
little control over signaling
bidirectional communication
chemical synapses
uses a neurotransmitter
how much control is there in chemical signaling
a lot
what type of communication in chemical synapses
unidirectional
one particular neuron is always in charge
presynaptic cell
neuron before the synapse
cell has produced an action potential
axon terminals are at the synapse
postsynaptic cell
comes after the synapse
dendrites are at the synapse
cell is receiving neurotransmitter
signaling via chemical synapses for presynaptic cell
action potential arrives at axon terminals
Ca channels open
Ca enters Ca in neuron allow granules of neurotransmitter to fuse
neurotransmitter is released in to the synaptic cleft
signaling via chemical synapses in postsynaptic cell
neurotransmitter binds to its specific receptor on postsynaptic cell (acetylcholine)
the acetylcholine receptor is a ligan-gated channel
a small Na current moves in to the cell
the affect on postsynaptic cell ends when neurotransmitter goes away
how can a neurotransmitter go away
can be taken back into presynaptic cell
can be destroyed
What is the name of the enzyme that destroys neurotransmitter
Acetylcholinesterase
What is it called when a neurotransmitter is taken back in
Reuptake
graded potentials
release of neurotransmitter into the synaptic cleft causes the postsynaptic cell body to produce a current
what is a small current called
a graded current
what will a small current (graded current) cause
small changes in voltage called postsynaptic potentials or migrated potentials
graded potentials fading
they fade rapidly with time and distance
how are graded potentials produced
using ligand-gated channels
low conductance channels
where are graded potentials formed
in the dendrites and the cell body
graded potential strength
vary
it is directly proportional to the amount of neurotransmitter in synaptic cleft
EPSP
excitatory postsynaptic potential
what are EPSP for
always depolarizes postsynaptic cell and changed voltage toward threshold
IPSP
inhibitory postsynaptic potential
what are IPSP for
always hyper polarizes the postsynaptic cell and moves cell voltage away from threshold
summation
a postsynaptic neuron feels a greater effect from a presynaptic cell when the stimulus us strong or if stimuli are frequent
temporal summation
add graded potentials that are near in time
what do presynaptic neurons produce during temporal summation
many graded potentials in a row
spatial summation
add graded potentials that are near in distance
what do multiple presynaptic neurons produce in spatial summation
graded potential at the same time
result of input
postsynaptic neuron must decide whether or not to form its own action potential
how does a postsynaptic neuron decide to form its own action potential
based on the sum of graded potentials
can have EPSP or IPSPS
can sum several small graded potentials or only one
when will a postsynaptic cell for its own action potential
if it depolarizes to -55mV at axon hillock
subthreshold potential
some EPSP are too weak to trigger a new action potential -65mV to -56mV
synapse localization
a synapse that is closer to the postsynaptic axon hillock has a greater effect
axodendritic synapse
connects to dendrites
axosomatic synapse
connects to cell body
axoaxonic synapse
connects to axon hillock
neurotransmitters
are signaling chemicals released from the axon terminals
how many neurotransmitters can a neuron release
one or several
receptors
each neurotransmitter has its own
what does a direct acting neurotransmitter do
opens a channel
what does an indirect neurotransmitter do
activates second messenger pathways
no channels- intracellular signaling cascades - long lasting effects
acetylcholine
first neurotransmitter ever identified
what is acetylcholine used in
neuromuscular junction as part of the ANS
Norepinephrine
pleasure neurotransmitter in the CNS
used as part of the ANS
what can enhance norepinephrine release
amphetamines
what does cocaine and some antidepressants cause for norepinephrine
removal from synaptic cleft is inhibited
dopamine
pleasure neurotransmitter in CNS
linked to several disorders
what disease is dopamine deficient in
parkinsons disease
what disease is linked with increased activity of dopamine
schizophrenia
serotonin
regulates mood
more of it makes you happy
what does prozac and ecstacy cause to serotonin
blocks the removal of it from the synaptic cleft
what is serotonin released by
food mostly sugary foods
what are Biogenic Amines
Norepinephrine
dopamine
serotonin
GABA
gaba-aminobutyric acid
what does GABA do
major inhibitory neurotransmitter of the brain
opens CL channel - hyper polarizing - forms IPSPS
glutamate (MSG)
major excitatory neurotransmitter forms EPSPS
several subtypes of channels
one subtype of glutamate channels
involved with learning and memory
neurotoxicity
brain can suffer damage due to excessive glutamate release
return of O2 causes so much glutamate signaling that neurons die
type of amino acids
GABA
Glutamate
endorphins
inhibit pain under stressful conditions
examples of endorphins release
long strenuous exercise and childbirth
tachykinins
involved with pain transmissions
where are tachykinins released from
damaged tissues
the brain
one of the primary structures of the CNS
what does the brain do
acts as a major control center of the body
what is the brain composed of
very soft tissue
how much does the brain weight
3-4 lbs in an average adult
how is the brain composed
4 major regions
4 regions of the brain
cerebral hemisphere, brain stem, cerebellum, diencephalen
ventricles
fluid filled cavities with the brain
are continuous
what are the ventricles filled with
cerebral spinal fluid (CSF)
what are ventricles lined with
ependymal cells that help to circulate the CSF
lateral ventricle
longest C-shaped deep to cerebral hemisphere
third ventricles
deep to diencephalon
fourth ventricles
deep to brain stem
continuous with central canal of the spinal cord
single channel
cerebral hemispheres
form the superior and superficial portion of the brain
longest part of the brain 80% of brain mass composed of 3 different areas
cerebral cortex
superficial area of grey matter
absolute type of brain
cerebral white matter
composed of deep white matter myelinated axons
basal nuclei
deep islands of grey matter found within white matter
folding
the surface of the cerebral hemispheres is extensively folded
what is the purpose of folding in the brain
increases the surface area of the brain
holds more neurons in brain making us more intelligent
a gyros (many gyri)
an elevated ridge of brain tissue
a sulcus (many sulci)
a shallow groove in brain tissue
a fissure
deeper groove in brain tissue
lobes
each cerebral hemisphere is divided by sulci into five distinct lobes
4 superficial lobes
frontal
parietal
temporal
occipital
1 deep lobe
insula
central sulcus
separates the frontal lobe from the parietal lobe
lateral sulcus
outlines the top of the temporal lobe
cerebral cortex
the outermost layer of the cerebral hemisphere
mapping
an approximation
functional areas of the cerebral cortex
a map of the cerebral cortex localizes regions with different functions
what does the cerebral cortex control
most somatic processes
conscious portion of brain
3 major types of areas in the cerebral cortex
motor areas - sensory areas - association areas
sensory areas
vision, smell, taste, hearing, touch
cerebral cortex control
composed of two equivalent but not identical sides
left and right hemispheres
left and right hemispheres
each side is concerned with the opposite side of the body
called contra lateral control
ipsilated
same side
what is the left hemisphere for
more logical, better at math, controls language
what is the right hemisphere for
more artistic, visual side of brain, creative side, nonverbal language
motor areas
control voluntary (somatic) movements
primary motor cortex
used to stimulate skeletal muscles
- initiating voluntary movements
where is the primary motor cortex found
in the posterior portion of the lobe
what do the primary motor cortex contain
very large neurons (pyramidal cells)
what happens when the primary motor cortex is damaged
will result in paralysis
what do neurons that are located together do
move a particular body part
important parts are given more neurons
(hand, face, tongue)
homunculus
a distorted odd looking figure in the mapping
epilepsy what is it due to
excess electrical activity in the brain
usually from an overactive cluster of neurons
what does the excess electricity do during epilepsy
spill into areas of the brain
what happens when excess electricity spills in to brain
impair normal motor function
can affect motor and sensory functions
causes skeletal muscles to contract and false senses
severity of seizures
can vary
petit mal seizures
also called absence seizures
severity of petit mal seizures
less or lower in severity
characteristics of petit mal seizures
blank facial expressions and facial muscle twitches
who does petit map seizures affect
common in children up to 10 years of age
grand mal seizures
tonic clonic seizures
severity of grand mal seizures
more severe than other one
characteristics of grand mal seizures
false sensory information and convolutions
uncontrolled muscle contractions as signals reach the primary motor cortex
what precedes grand mal seizures
an aura, a flash of light
premotor cortex location
in frontal lobe
sits anterior to primary motorcortex
what does the premotor cortex control
learned motor skills that are pattered
- cycling, walking, chewing, typing
where does the premotor cortex send patterns to
the primary cortex
what happens when the premotor cortex is damaged
loss in patterned skills
can be relearned
Broca’s area location
in the frontal lobe
what are the broca area’s function
for muscles used for speech
usually active when we plan to speak
where is the broca area found
only in left hemisphere of the brain
frontal eye field location
in the frontal lobe
what does the frontal eye field control
voluntary movement of the eyes
sensory areas
involved with conscious perception of stimuli
primary somatosensory cortex location
in the parietal lobe
just posterior to the central sulcus
what does the primary somatosensory cortex do
spatial discrimination of somatosensory input
Locates the part of the body that is being touched.
what uses the primary somatosensory cortex the most
areas of the body that are more sensitive to touch
hands feet face tongue lips genitals
uses more neurons
appear larger on map and form a homunculus
somato
means touch
somatosensory association cortex location
parietal lobe behind primary somatosensory cortex
what does somatosensory association cortex do
integrates information coming into the brain in an attempt to understand an object that is being felt
somatosensory association cortex continued
allows for ID based on touch
texture size and shape
ID using prior experience
primary visual cortex location
located at the posterior tip of the occipital lobe
primary visual cortex
largest of all cortical sensory areas
vision uses the most brain power - color - depth perception
processes info from eyes to produce vision
visual association area location
also in occipital lobe
Auditory association area
allows us to identify current sounds
compares current sounds to known sound and using memories
Also in temporal lobe
gustatory cortex
association area identifies taste perceives taste, located in insula
olfactory cortex
perceives smell
located in temporal lobe
association area identifies smell
vestibular cortex
gives a sense of balance
located in insula
visceral cortex
located in insula
for crude sense of organ pain
Primary auditory cortex
Receives information from ears to produce sound
Primary auditory cortex location
In the superior margin of the temporal lobe
Just beneath lateral sulcus
