brain learning and motivation: neural communications Flashcards
typical neuron structure
neutrons are basic building blocks of nervous system
nucleus cell membrane dendrites sona *cell body Myelin sheath node of ranvier axon axon terminals
informaion passing through neutrons
information passes down neutron by electrical impulse
information is transmitted within neutrons
through axonal conduction
information transmitted between neutrons
through synaptic transmission
how they communicate
the neuron generates an electrical impulse that travels down the axon and into the axon terminals
3 main neuron types
sensory
motor
interneuron
purkinje neutron found by
costandi
Ramon V Cajal in 1899
neuron structure: soma
the ell body
neuron structure: dendrites
specialised receiving units that collect messages from neighbouring neutrons and send them on to the cell body
neuron structure: Axon
cunducts electrical impulses away from cell body to other neutrons muscles or glands
neuron structure: Myelin Sheath
series of fatty wrappers formed by Glial cells
surrounds axons of neutrons that communicate over long distances in nervous system
allow fast propagation of action potentials along those axons
MS
De-Myelination occurs
neuron structure: nodes of Ranvier
Gaps between the Glial cell wrappers of Myelin Sheath around axons
nodes are crucial to the speed of electrical impulses along Myelinated axons
electrical signal is slow even in Myelinated neutrons its around 1-91m per sec
the ways in which neutrons pass information
electrical impulses
chemistry
Myelinated neurons appearance
white matter
whitish appearing particles and paths in the brain
composed of Myelinated neurons in particular Axons
gray matter
the absence of myelination gray matter is: Dendrites cell bodies unMyelinated axons ...these are the nervous systems microcircuitry
Glial cells
act as a guide wire for growing neurons
provide a supportive scaffolding for mature neutrons
form Myelin Sheath and blood brain barrier
the blood brain barrier
protects the brain from:
noxious substances
some drugs
blood vessels in brain
selectively permeable barrier
have a protective lining
allows in nutrients but keeps out toxious substances
prescription drugs for brain conditions must be able to pass through barrier
Neuron communication: Axon membrane
Axon membrane is semi permiable so some chemicals can pass through freely others cat
When Axon membrane is stable there is an excess of positive ions on outside making a negative charge difference
recording voltage within a neutron
an electrode is inserted into axon
the other records from Axons outside
at rest a -70 millivolt different ewill be detected
at firing the voltage will shift slightly before returning to resting voltage
Neuron communications: electrical communications and voltage changes
when membrane is stimulated it deeplarises
and sodium ion channels open
this leads to an action potential
ion movement leads to an excess of positively charged particals inside the membrane
this produces a positive voltage swing
the excitation spreads leading to propagation of the action potential along the axon
immediately there is a refraction period
potasium channels open causing hyper polarisation
electrical communications: hyperpolarisation
more negatively charged inside than the resting potential
electrical communications: duing refractory period
cells are less sensitive to stimulation than they are normally
electrical communications; return to resting potential
there are pumps that actively use energy to move sodium ions out of the neutron for every two potassium ions it puts in
At rest, again there are rela;vely more sodium ions outside the neuron and more potassium ions inside that neuron
electrical communications: sequence of events of action potential
neuron membrane is disturbed
sodium channel opens and sodium floods in
when voltage reaches -55 the neutron fires sending a wave of electrical impulse along the neutron
sodium channels close and potasium opens reversing depolarisation
potasium channels close
ack to resting potential