How nerves work Flashcards
Sensory information travels IN via
dorsal root
motor information travels OUT via
ventral root
afferent
sensory
dorsal
efferent
motor
ventral
dendrites
receive information
axon hillock
triggers action potential
Axon
sends action potential
Axon terminals
release transmitter
90% cells in the CNS are
glia
Astrocytes
maintain the external environment for the neurones
surround blood vessels and produce the blood brain barrier
Oligodendrocytes
form myelin sheaths in the CNS
Microglia
phagocytic hoovers mopping up infection
Graded potentials
decided when an action potential should be fired
Resting membrane potential
keeps cells ready to respond
the inside of a cell is ……….. relative to the outside
negative
RMP of most cells is
-70 mV
equilibrium potential
the membrane potential at which the electrical gradient is exactly equal and opposite to the concentration gradient
the concentration gradient determines the
equilibrium potential
Nernst equation predicts the
equilibrium potential
The RMP is dominated by the resting permeability of
potassium (K+)
interior of cell positively charged
depolarisation
interior of cell negatively charged
hyperpolarisation
the connection where one neuron modulates the activity of a target is called a
synapse
contraction is triggered by AP in the
sarcolemma
Can disrupt the NMJ
tetrodotoxin joro spider toxin botulinum toxin curare anticholinesterases
Anatomical arrangement of synapse
axo-dendritic
axo-somatic
axo-axonal
RMP is -70mV
threshold potential is usually
-55mV
depolarisation usually reaches
+40 mV
Large axons increase
conduction velocity
you can spread Na+ channels out further - the depolarisation from one will still be big enough to get to its neighbour to reach its threshold and make its neighbour open
Myelin
folds of membrane from Schwan cell or oligodendrocyte
de-myelination diseases
multiple sclerosis
de-myelination allows for the big local current to
decay quicker
conduction fails
Examples of graded potentials
Generator potentials
postsynaptic potentials
endplate potentials
pacemaker potentials
graded potentials are decremental therefore they are
only useful over short distances
Action potential properties
encoded by frequency cannot summate threshold self-propagating depolarising voltage-gated
Graded potentials
encoded by amplitude summate no threshold decremental ligand-gated
‘decides’ is a cell will fire an action potential
Inhibitory post synaptic potentials (IPSP)
hyperpolarising
can open Cl- to flow out or allow more K+ in
Excitatory post synaptic potentials (EPSP)
depolarising
more Na gets in than K gets out
post synaptic potentials are produced by a neurotransmitter opening of closing ion channels. therefore they are
ligand-gated
action potential are produced by depolarisation of the membrane potential opening ion channels. therefore they are
voltage-gated ion channels
