lecture 10 nervous sys Flashcards
define radiata
a major grouping that includes more or less radially symmetrical animals, as coelenterates (jellyfish, sea anemones, corals), ctenophores (comb jellies), and echinoderms (starfish, sea urchins, sea cucumbers)
what type of nervous sys does radiata have?
basic radially arranged network of nerves.
integration
receives input and decides what should be done about i
name 3 jobs of the central nervous system
consists of brain and spinal cord receives and integrates sensory input from the PNS sends commands (based on PNS input) back to the PNS
peripheral nervous system divides
divides into the sensory and motor division
motor sys divides into the
somatic and autonomic
autonomic divides into the
sympathetic and parasympathetic
effector
an organ or cell that acts in response to a stimulus
name 3 effectors of the pns?
muscle cells
secretory cells
any organ that can respond to a neural signal
propogate
to transmit or spread from one generation to the next
dendrites
receive signal input from other neurons
soma
integrates synaptic potentials
axon (= nerve fiber)
conducts signal away from the soma
axon terminals
propagate the signal to the next neuron
afferent
sensory signals from receptors –> CNS
CNS integrative centers process the input.
efferent
control signals from the CNS –> effectors
Effectors (targets such as muscle or secretory cells) effect a response
interneurons
connect neuron to neuron within the CNS.
synapse
The space between the axon terminal of one neuron
and the dendrite of another
excitatory synapse
increases probability of propagation to a postsynaptic cell.
inhibitory synapse
decreases probability of propagation to a postsynaptic cell.
innervate
Neurons with synaptic terminals connected to a cell
glial cells
provide neurons with support and protection.
name the 4 roles of glial cells
surround neurons and hold them in place
supply neurons with nutrients and oxygen
insulate neurons from each other
destroy pathogens and remove dead neurons
oligodendrocytes
form myelin sheath for cns
astrocytes
form communication link between capillaries and neurons
ependymal cells
ciliated; line ventricles of brain and spinal cord central canal
microglia
macrophages that mediate CNS immune response
name the 3 type of ganglias of somas that satellite cells wrap themselves around?
sensory
sympathetic
parasympathetic
what does mylin really do?
forms an insulating sheath around nerve fibers
sheath increases speed of action potential transmission
composed of proteins and phospholipids
it prevents electrical signals that travel down the axons from decaying due to electrical current leaking out through the axon membrane
invertebrates have myelin precursors but is it the same as the myelin of vertebrates?
no because the precursor does not spread long and last for up to 1 milisec while vertebrates have 20 to 100 milisec
nerve
bundle of axons and their myelin sheaths in the PNS
endoneutrium conn tiss
surrounds each axon/myelin sheath
fasicle
Sheathed axons are bundled
perineutrium con tiss
encases each fascicle.
epineurium conn tiss
encases all the fascicles together.
tracts
In the CNS, the structures analogous to fascicles
ascending tracts
carry impulses along the spinal cord toward the brain.
descending tracts
carry impulses from the brain (or higher spinal cord)
to lower spinal cord regions.
ganglion
- cluster of nerve cells OR nerve cell bodies occuring somewhere along a nerve. Ganglia
- form communication connections between neurological structures.
- may interconnect with each other to form a plexus
dorsal root ganglia
(a.k.a. spinal ganglia) are made up of afferent neuron bodies.
cranial root ganglia
are made up of cranial nerve neuron bodies.
Autonomic ganglia
contain autonomic neuron bodies.
Preganglionic nerve fiber
travels from the CNS to the ganglion
axons are myelinated
are less numerous than postganglionic fibers
Postganglionic fibers
travel from the ganglion to the effector
axons are NOT myelinated
are more numerous than postganglionic fibers
Ganglial autonomic neurons are
dendritic
Ganglial sensory neurons are mostly
unipolar
intracellular charge is decreased by
less k+ which leaves more proteins that have a neg charge
cl ions
resting potential and charge
it is the unstimluation of a nerve cell
potassium pump but sodium pump is closed
about 70 mv
equilibrium potential
the flow of potassium ions are equal inside and outside
creates a voltage
as the electric gradient inceases
the chemical gradient will decre
define action potential
is a momentary reversal of membrane potential
from its resting state.
three typicals of action potential
- causes internal charge to change from -70mV to ~ +40mV
- lasts about one millisecond
- ends when membrane potential is restored to its resting state
what part of the action potential is always the same and what part of it always changes
the magnitude is always the same.
the frequency always changes and depends on how strong the stimuli is
what is the threshold for the depolarization and what is the peak of the depolarization for an action potential that also resembles the absolute refractory period?
threshold is (-) 55 depolarization peak is (+) 40
value for hyperbolize
-75 mv
the less sodium channels that are closing due to the relative refractory period,
the more strength is needed to get a depolarization for an action potential
depolarization of voltage-gated channels along the length of the axon is what direction?
unidirectional
relative refractory period (RRP)
After peak depolarization, K channels open,
allowing K+ to repolarize the cell.
This takes a few milliseconds to stabilize.
define electronic conduction and what happens
Change in voltage decreases exponentially with distance from the point of stimulation.
This is known as electrotonic conduction
(= passive or decremental spread).
As current flows away from the point of stimulation,
some K+ leaks out of ion through channels, reducing voltage.
length constant
distance at which the decaying voltage change is 37% of its value at the point of stimulus/origin.
Three factors can increase conduction velocity:
increase in axon diameter
lower resistance
smaller length constant
myelination
prevents leakage at internode regions
sodium channels open at nodes, restoring lost potential
increase in temperature
higher temperatures increase molecular motion
but above 40o, there is the risk of ion channel denaturation
Homeothermy allows shorter axons with higher velocity conduction.
ventral root
root is the efferent motor root of a spinal nerve.
