nervous system Flashcards
major divisions of the nervous system
CNS
peripheral
what is the CNS
brain and spine
what is the peripheral nervous system
subdivided into autonomic: sympatetic and parasympatetic
somatic motor control and conscous control
what are the three major regions of the brain
fore brain
mid brain
hind brain
what is the fore brain
prosencephalon
main large part
used for complicated motor movement and sensory pereption
parts in the fore brain
cerebral hemisphere
thalamus
hypothalmus
what is the mid brain
mesencepaton
smaller with nerve tracts
relays information for audio, visual and body movement
what is in the mid brain
substantial nigra
what is the hind brain
smaller brain
respiratory rate
heart rate
movement
what is in the hind brain
pons
medualla
cerebellum
the function of the spinal fluid
protection and provides nutrients
PET scans
uses radiolabelled emitters
coloursare seen for key structures
what is an MRI scan
functional magnetic ressonance image
measures change in blood flow relative to neural activity
grey scae
what are the colours on an MRI
grey areas nerve cell bodies
white matter is bundles of nerve fibres
what is CSF
cereobrospinal fluid
between
acts as a cushion, protection, homoetsatis barrier
surronded by special membranes for nutrient movement
structure of the spinal cord
central grey areas with 2 horns and surronding white matter
what is the central bit of the spine
grey matter
dorsal and ventral horns, doral is back, ventral front
what is the dorsal and ventra horns
in the centre spine
dorsal is back
ventral front
what is the function of the dorsal and ventral horns
control sensory function usign spinal nerves
communicate and used in reflexes
what goes into the dorsal horn
afferent nerves go in
taking information into the CNS
e. sensory pain
what comes out of the spine
efferent nerves
exit via the ventral route
go to skeletal muscles/somatic system
effectors
examples of non-neuronal cells
astrocytes
oligodentrocytes
micoglia
ependymal cells
what is an astrocyte
supportive function for CNS neurones
contribute to blood brain barrier
star shaped
what is an oligodendrocyte
form the myelin sheath around axons in the CNS
what are the microglial cells
carry out phagocytosis in the CNS
what are ependymal cells
epithelial cells in the fluid filled spaces of the brain and central canal of the spine
posess microvili to help circulate CSF around the CNS
functions of neurones
- rapid transmission of information from spesific sources to selected targets
- integration/summation of information from manny sources
key anatomical features of a spinal motor neurone
soma cotains nucleus main axon then diverges dendrites recieve info presynapticl terminals on dendrites nodes of ranvier axon hillock
name the functional units of the neurone
dendrites cell body axon hillock axon axon collaterlas nodes of ranvier myelin sheath terminal branches nerve terminals/synaptic boutons
what are the two processes in the nervous system
dendrites and axons
dendrites recieve convergent information
axons transmit divergent signalling
what is the resing potentail
-70 millivolts
how can you calculate the resting membrane potentail
Nerst equation
how does the nerst equation work
can caulte the equalibriu potentail of a ion
divides the extracellular ion conc by the intracellular conc
equibrium poteential for Na
+61
equilirium potetnail for K
-94
equlilibrium potentail for Ca
+12
what tyoe of channnel is Na
activation M gate
inactivation H gate
what type of channel is the K channel
activation N gate
describe the process of action potential changing channel openign
both closed initially K closed while Na open Na inside shit, inactivated K begins to open Na then closes fully while K ramins openw
what drive depolarisation
sodium coming inwards
what drives repolarisation
potassium current outwards
what is the all or nothing priciple
if the threhold is exceeded, all Aps have similar magnitiude and ruation
what is the absolute refractor period
Na channels are open or inactivated
AP cannot be eliticed
what des myelination determine
conduction elocity
what is myelin
phospholipid wrapping around and insulating the axon
in the CNS what myelinates axons
oligodenrocytes
in the PNS what myelinates axons
schwan cells
what doe myelin do
decreases the capacitance of the axon restricting the generation of APs to the nodes of ranvier
saltatory conductance, it junps from node to node
what is MS
neuromuscular disease involving the destruction of myelin
thought to be autoimmune
what do APs depend on
the exisiting resting membrane potential
what initiates and terminates Aps
initiaed by increased Na permeability which deppolarises the membrane
terminated by slower increase in K permeability whih repolarises the membrane
what causes the neurone to be unable to fire during the absoulute refractor period
Na channel inactivation
what is the relative refractor preiod
prolonged k channel acitvation makes it harder for an AP to fire
which axons conduct faster
large diameteris faster than small
what is firing frequency of neurones mesured in
Hertz
what are the types of connections in neuronal synapses
axodendritic
axosomatic
axoaxonmal
dendrodendtiric
what are the two types of synapses
chemical
electrical using gap junctions
how do chemical synapses work
axons of presynaptic neurons make contact with target psotsynaptic cells
neurotransmitters are released
how do neutotranmitters work
synthesied in nerve terminal and pacaged into vesicles
they are relased on the arriva of action potential at the presynaptic termial
what do excitatory neurotransmitters do
increase nerve activity
causing depolarisation
initiate EPSPs
what is an EPSP
excitatory post synaptic potential
increased excitability
examples of axcitatory neurotranmitter
glutamate
ecetylcholine
features of EPSPs
smaller
gradend, vary in amplitude
summate, add to each other
temporal, decay with distance
what does the binding of Ach do to acetylcholne receptors?
activates it
opens it allowing Na to flow through
what do inhibitory synapses do
decrease nerve activity
cause hyperpolarisation
initiate IPSPs
what is an IPSP
inhibitory post synaptic potential
examples of inhibitory neurotramitter
GABA
opoids
acetylcholine
what determines if there is an AP or not
the balance between EPSPs and IPSPS converging on a neurone at any one time
what do inhibitory neurtroraittesr do
GABA binds to the inactive receptor
it activated it allowing Cl- in
opposes the exictability of the neurone
features of IPSPs
small
gradent
temporal
summate
how do inhbitory NTs stop Aps
\Cl influx combined with K efflux make the neurone negative and thus inhbit the AP generation
how do electrical synapses work
open channels conudcting directly, gap junctions
what are two two ways acetlycholine works
nicotinic: excitatory
muscarlinic: inhibitory
if the number of synpses firing increases the 24, what will the maximun acheiveble voltage be?
+30mV
all or nothing priciple
which axon out of axosomatic and axodendtiic requires more pulses to depolarise the postsynaptic cel to the threshold?
axon on fthe distal dendrites
define convergence
many neuronal inputs convergin on a single neurone
what are the two major determinants of conduction veolcity in nerve axons?
axon diameter: large means lower intracelular resitance
- degree of myelination
what is divergence
once an xon has left the cell it may give rise of a few or many axon collateroal
this is called divergence
why are long axons not idea
all the ptoeins must be transported from the cell body and proteins for recycling returned to the cell body along with t
what is the equlibrium potential
potential at which the tendency of nion to move down its concentration gradient is equally balanced by the membrane potentials
