U2- Nervous Tissue Flashcards
nervous system function
maintains homeo.
w/ electrical + chem. signals
stages
1- detects change (sensor)
2- CNS decodes message
3- CNS ignites muscl. + gland cells
peripheral nervous system (PNS) parts
to or away from CNS
inc. sensory and motor
then visceral and somatic
nerve
bundle of nerve fibers wrapped in CT
fun- carry signals btw organs
gangilia
swelling of nerve
sensory branch of PNS
carries sig to CNS
motor branch of PNS
sign to CNS that ignite muscle and gland cells
visceral motor branch of PNS- parts
“autonomic”
sympathetic and parasympathetic
visceral motor branch PNS- sympathetic
arouses body for action
visceral motor branch PNS- parasympathetic
calming affect
stim. digestion
visceral motor branch PNS- function
sign to glands
cardiac + smooth muscl.
adipose tissue
somatic motor branch PNS
sign to skeletal musc.
somatic sensory branch PNS
sig from skin, musc. and bones
visceral sensory branch PNS
sign from heart, lungs, stomach, bladder…
neuron charac.
excitability
conductivity
secretion
neuron excitability
respond to environ. changes (stimuli)
neuron conductivity
respond to stimuli w/ electrical sig.
classes of neurons
sensory
interneurons
motor
sensory neurons
“afferent”
toward
detect stim. + transfer to CNS
exterorecptors + proprioreceptors
interneurons
makes decisions
only in CNS
motor neurons
“efferent”
away
send sig. from CNS to musc. + gland cells
dendrites
receive sig. from o/ neurons
node of ranvier
space on axon btw internodes
internode
thick protein structures
soma
control center of neuron
neurofibrils
actin filament
organize rough ER
penkaryon
cytoplasm of soma
produces neurotrans.
axon
conduction of nerve sig. away from soma
long tail
axon terminal
forms synapse w/ next neuron
where neurotransm. released
axonal transport
anteograde
retrograde
anteograde
performed by kinesins
soma to axon
reterograde
performed by dyneins
axon to soma
neurogilia
“microgilia”
protect neurons and provide framework
types of cells in CNS
ependymal
microgllia
astrocytes
oliogodendrocytes
types of cells in PNS
schwann + satellite cells
ependymal cells
line brain and spine
produce cerebral spinal fluid (CSF)
microglia
destroy foreign bodies (not very effective)
immune cells of brain
astrocytes
supportive structure
stim. neurons
regulate comp of ICF
maintain blood-brain barrier
oligodendrocytes
myleination of axons
schwann cells
regen of damaged nerve fibers
form sheath around PNS axons
satellite cells
surround soma in ganglia
electrical insulator
myelin sheath for PNS and CNS
CNS- oliogodendrocytes
PNS- Schwann
multipolar neuron
form all motor systems
very long
bipolar neuron
long axons
unipolar neuron
horizontal
cell body off to one side
found in afferent- sensory neurons
anaxonic neuron
no axon
alters act. of o/ neurons
found in brain
act as junction box
schwann cells
wrap around axon like toothpaste tube
cytoplasm forced to one end
if unmyleinated
folds only once around axon
oligodendrocytes
cannot migrate
have centrifugal myleination (away) and centripetal myleination (towards center)
factors of nerve conduction speed
diameter of fiber
presence of myelination
nerve regeneration (only PNS)
1- fiber cut + degenerated by macrophages
2- soma swells
nucleus moves off center
axon makes new terminals
3- near cut, schwann cell make re-gen tube
4- tube guides terminals to target cell
synapse reestablished
5- soma shrinks
reinnervated musc. fibers grow
5-
electrical potential
diff in conc. of charged part. btw points
form potential energy
potential energy
can produce a current (flow of charged par.)
polarized
if has poten. voltage
resting mem. pot. (RMP)
charge diff. across plasma mem.
through ele. currents
ion flow through ion gated channels
RMP factors
diffusion of ions down conc. gradient
selective permeability of mem. for ions
attraction of cations and anions
mvmnt of Na and K across mem.
3 Na out- mre conc. in ECF
2 K in- most permeable to mem.
sensors
rxn in PNS
change RPM
effectors
sensors send signal to effectors in CNS
current flow diagram
resting
graded
action pot.
neurotransmitter
(disturbes resting mem. again)local potential location
dendrites and soma
local pot. charact.
graded
decremental
reversible
graded
vary in volt. based on stim. (Ex. hyper, or re/depolarization)
higher stim- channel open for more time
decremental explanation
as Na charge reaches surr. K it quickly gets repolarized (more negative)
reversible
mem. returns to resting
excitatory or inhibitory
excitatory reversibility + postsynaptic pot.
depolarize by ACh
neuron more likely to reach action potential
inhibitory reversibility + postsynaptic pot.
hyperpolarize (extra neg.)
neuron less likely make action pot.
ways to open and close gated channels
chemically
mechanically
voltage
local pot. channels charac.
graded
mech. and chemically controlled
action potential location
axon
action pot. charac.
all or none rule
if depolar. to threshold- fires max voltage
NOT GRADED
nondecremental
not reversible
action pot. cannot be stoppedaction pot. channel charac.
gated
vol. gated
need density of vol. to work
can be caused by excitatory local pot. if reaches trigger zone
how action pot. move in one direction (transfer)
action pot. steps
1- depolar. of mem by current (local pot.)
2- threshold met
3- neuron produces action pot.
Na enters cells + depolar.
mem. vol. inc
4- Na flow stops
polarity flipped from RMP
ICF mre + and ECF mre -
5- K ions repelled by positive charge and exit cell
repolar. mem. to -
6- mre K channels open than Na
causes mre neg. repolarization (hyperpolar.)
simplified action pot. steps
1- RMP 2- Local pot. 3- Threshold 4- depolar (Na in) 5- Na channels close and K channels open @ top 6- repolar (K out) 7- RMP passed negatively (hyperpolar.) 8- Na K pump compensates and returns mem. to RMP
refractory period
resistance against restimulating an action pot. after neuron fires
absolute period
as long as Na gates open
no amnt of stim will trigger neuron
relative period
from Na gates closure to hyperpol.
strong stim. wil trigger neuron
has to overcome output of K+ ions w/ Na (hard to do)
signal conduction- unmyleinated
uninterrupted chain rxn of current
“continuous conduction”
channels along entire length
signal conduction- myelinated
faster
“salatory conduction”
current not continuous
only gated channels at node of ranviers
continuation of signal in myelinated neuron
Na enters node of ranv. + repelled by o/ Na
moves dwn axon like repelling magnets
dec. strength w/ distance
roll of synapses
if delay signal speed
used bc are processing componet
temporal summation
stim from only one synapse
stim regen before 1st current fades
build up overtime
triggers action pot. w/ threshold vol.
spatial summation
stims from many synapses
meet at hillock
presynaptic facilitation
one neuron enhances effects of o/ neurons
presynaptic inhibition
one neuron suppresses effects of o/ neurons
synpatic plasticity
synapses can be added and taken away in responce to experience
allows signals to travel easier
maintenance of RMP
Na K pump
ion gated channels
why is RMP negative if K and Na are +
k mre permeable to mem.
mem. favors K at -90 v Na at +50
Na ion mvmt across mem
originally- moves into cell along conc. gradient
lessens negative - charge of ICF
since not opposite anymore
Na channels close
equilibrium = +50K ion mvmnt across mem
K more permeable
moves along conc. gradient to less conc. which is outside of the cell
cell becomes more neg.
since not opposite charges anymore
K channels close
equilibrium = -90
RMP voltage amount
-70
