Nervous system Flashcards
Hydra (cnidarian)
neurons in nerve nets control the gastrovascular cavity
sea star (echinoderm)
Central nerve ring with radial nerves to each arm
cephalization
clustering of neurons in a brain near anterior (front) of animals with bilaterally symmetrical bodies
Planarian (flatworm)
small brain and longitduinal nerve cord define simplest CNS
Insects (arthropod)
brain+ventral nerve cord, segmental ganglion make PNS
Squid (upper molluscs)
brain+extensive ganglia
chordate
brain+dorsal spinal cord+sensory ganglion
dendrite
highly branched extensions that receive signals from other neurons
axon
transmits signals to other cells and may be over a meter long
astrocytes
in CNS, they provide structural support for neurons and regulate extracellular concentrations of ions and neurotransmitters
blood brain barrier
astrocytes induce tight junctions between cells that line capillaries in brain and spinal cord
radial glia
form tracks which newly formed neurons migrate from neural tube
oligodendrocytes
CNS glia that form myelin sheaths around axons with lipids like insulation
schwann cells
PNS glia that form myelin sheaths around axons with lipids like insulation
Na+ gradient
15mM cytosol; 150 mM extracelluar
K+ gradient
150 mM cytosol; 5mM extracellular
Cl- gradient
10mM cytosol; 120mM extracellular
ungated ion channels
resting potential is regulated by diffusion of K+ and Na+
ligand gated ion channels
found at synapses and open or close when neurotransmitter binds to channel
voltage gated ion channel
in axons, dendrites, cell bodies; open or close when membrane potential changes
hyperpolarization
increase in magnitude of membrane potential; inside becomes more negative and commonly caused by opening K+ channels
depolarization
inside of membrane becomes less negative due to opening Na+ channels
resting state gates
Na+: inactivation gate open-activation gate closed; K+: gate closed
depolarization gates
Na+: inactivation gate open-some activation gate open; K+: gate closed
rising action potential gate
Na+: inactivation-activation gate open; K+: gate closed
falling action potential gate
Na+: inactivation gate open-activation gate closed; K+: gate open
undershoot gate
Na+: inactivation-activation gate closed; K+: some gates open
refractory period
during undershoot no new action potential can occur
saltatory conduction
action potential moves from node of ranvier to node in myelin sheaths
node of ranvier
many voltage gated ion channels are present to transmit action potential to next segment
synaptic vesicles
presynaptic neuron synthesizes the neurotransmitter and is packaged here
presynaptic membrane-chemical
voltage gated Ca2+ goes into presynaptic terminal and causes synaptic vesicle fusion with presynaptic membrane
postsynaptic membrane-chemical
vesicles release neurotransmitter into synaptic cleft
synaptic cleft depolarization
action potential reaches synapse and triggers voltage gated Ca2+ channel
direct synaptic transmission
binds directly to receptor on ion channel that allows specific ions to diffuse across postsynaptic membrane
excitatory postsynaptic potential
neurotransmitter binds to Na+-K+ channel and membrane potential depolarizes so it is excitatory
inhibitory postsynaptic potential
neurotransmitter binds to K+ channel and membrane potential hyperpolarizes so it is inhibitory
temporal summation
EPSP happening closely together produces action potential
graded postsynaptic potential
since the postsynaptic cleft is at dendrite or cell body 1 EPSP is not able to produce action potential
spatial summation
EPSP produced by 2 different synapses can produce action potential