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stage in the repolarization time of an action potential when an additional repolarization event is not possible
what is the absolute refractory period?
sensory neuron, brings information in
what is an afferent neuron?
a branch of an axon
what is a collateral?
occurs in unmyelinated axons and is continuous along the length of the axon
what is continuous conductance?
motor neuron, information exits
what is an efferent neuron?
an event that results in the depolarization and formation of an action potential
what is excitatory post synaptic potential (EPSP)?
support cells of the CNS (not conducting cells)
what are glial cells?
an event that results in the hyperpolarization of a neuron and the prevention of an action potential
what is inhibitory post synaptic potential (IPSP)?
combining incoming and outgoing information
what is integration?
cell that myelinates neurons in PNS
what is a neurolemmocyte?
cell that myelinates neurons in the CNS
what is an oligodendrocyte?
the neuron leaving a synapse
what is a postsynaptic neuron?
the neuron leading up to a synapse (the one coming into the synapse)
what is a presynaptic neuron?
stage in the repolarization time of an action potential when an additional depolarization event is possible, but the threshold level will be higher than during a resting transmembrane potential
what is the relative refractory period?
movement of an action potential along a myelinated axon where the action potential only occurs at the nodes
what is a saltatory conductance?
electrical value at which the voltage-gated sodium channels will be stimulated to open resulting in depolarization
what is threshold?
electrical charge difference across a membrane
what is transmembrane potential?
channels that open and close based upon the charge difference across the membrane
what are voltage-activated channels?
nerve and muscle cells
what are the types of excitable cells?
receptive region, conducting region, secretory region
what are the three main functional regions of a neuron?
dendrites and cell body
what makes up the receptive region?
axon
what makes of the conducting region?
axon terminal
what makes of the secretory region?
to produce and transmit electrical signal
what is the function of a neuron?
soma, nucleus, most of cytoplasm, and most organelles
what is the cell body?
cell body and cytoplasmic extensions
what are the parts of a myelinated neuron?
dendrites and axons
what are the cytoplasmic extensions?
receive stimuli, conduct toward cell body
what do dendrites do?
conduct impulses away from cell body to effector
what do axons do?
Sufficient stimulation initiates action potential along axon, at base of cell body
what is the axon hillock?
insulating membrane around axon (separate cell)
what is the myelin sheath?
neurilemmal node, gap in myelin
what is the node of ranvier?
branches from an axon (along length) one way a single neuron is able to innervate multiple things
what are axon collaterals?
divisions at end of axon, each branch can innervate something
what are terminal branches?
end of terminal branches, neurotransmitter released (transmits signal to an effector)
what are synaptic terminals?
junction between two neurons, a neuron and an effector, or two cells
what is a synapse?
afferent (sensory), interneuron (association), efferent (motor)
what are the three functional types of neurons?
in the CNS, connection
where are interneuron neurons and what do they do?
multipolar, bipolar, pseudo unipolar
what are the kinds of neurons classified by structural feature?
reception, transmission to CNS, integration, transmission from CNS, action by effectors
what are the neural signaling processes?
have a single axon and multiple dendrites, over 99% of all neurons
what are multipolar neurons?
one axon, one dendrite, and a cell body between them
what are bipolar neurons?
eye and olfactory epithelium (nasal cavity)
what is an example of a place you can find a bipolar neuron?
lack dendrites, bipolar neuron that changes structure, only one projection from cell body, cell body off to side
what are pseudo unipolar neurons?
one carries sensory information from sensory receptors to cell body, one carries sensory information from cell body to spinal cord
what are the two processes of the extension from the cell body in pseudo unipolar neurons?
dorsal root ganglia of spinal nerves
what is an example of a pseudo unipolar neuron?
75%
what percentage of the CNS cells are glial cells?
support, maintenance, protection
what are the functions of glial cells?
astrocytes, ependymal cells, microglial cells, oligodendrocytes
what are the types of glial cells in the CNS?
neurolemmocytes (Schwann cells), satellite cells
what are the types of glial cells in the PNS?
glial cells in CNS, large star-shaped cells with many processes, majority of glial cells
what are astrocytes?
anchor neurons and blood vessels in place, transport nutrients and gases between blood vessels and neurons, form blood-brain barrier (makes brain capillaries impenetrable to most polar compounds and proteins), repair damaged brain tissue
what are the functions of astrocytes?
glial cells in CNS, line internal cavities of the CNS and have cilia
what are ependymal cells?
produce and circulate cerebrospinal fluid (CSF), might function as neural stem cells
what are the functions of ependymal cells?
glial cells in the CNS, found near blood vessels
what are microglial cells?
specialized macrophages, clean up cells, respond to injury or disease - remove bacteria and cell debris, signaling molecules that mediate inflammation
what are the functions of microglial cells?
glial cells in CNS, myelinate CNS axons, multiple axons
what are oligodendrocytes?
glial cells in PNS, Schwann cells, myelinate PNS neurons, individual axons
what are neurolemmocytes?
glial cells in the PNS, surround cell bodies of neurons in PNS, provide supportive functions
what are satellite cells?
component of CNS, clusters of neuron cell bodies
what are nuclei?
component of CNS, bundles of axons
what are tracts?
component of PNS, clusters of neuron cell bodies
what are ganglia?
component of PNS, bundles of axons
what are nerves?
in PNS, nearly nonexistent in CNS
where does nerve regeneration occur?
when the cell body and support cells associated with the axon are still intact (must have Schwann cells!)
when can nerve regeneration happen?
axon and myelin sheath degenerate distal to injury, growth processes form from proximal end of axon, Schwann cells and basal lamina form regeneration tube that directs new axon toward target cell, new axon reconnects to its target cell
how does nerve regeneration occur?
polarized
neurons are ___ cells
there is an electrochemical gradient across the semipermeable membrane
what does it mean that a neuron is polarized?
electrical potential (charge difference) across cell membrane
what is membrane potential?
10x greater inside than outside cell
what is the normal resting K+ ion concentration?
10x greater outside than inside cell
what is the normal Na+ ion concentration?
ion channels and the Na/K pump
how is the ion distribution maintained?
Na+, K+, Cl-
what are the major ions involved in transmembrane potential?
in millivolts, value expressed is inside relative to outside
how is the transmembrane potential measured?
-70 mv
what is the typical neuron resting potential?
K tries to leak out, Na tries to leak in
how to K and Na try to move across the membrane of a neuron?
more K+ leaks out than Na+ leaks in (more K+ channels than Na+ channels)
why is the resting membrane potential negative?
when voltage difference across plasma membrane does not equal 0 mV
when does cell polarization occur?
pumps 3 Na+ out and 2 K+ in, requires ATP, at steady rate, net Na+ diffusion is greater than net K+ diffusion out
how does the sodium potassium pump work?
K+ channels
what kind of passive ion channels are most common?
concentration of ions
what activates passive ion channels?
passive ion channels, chemically activated (ligand-gated) ion channels, voltage activated (voltage-gated ion channels), mechanically gated channels
what kind of ion channels are in neuron membranes?
driven by concentration gradient (Na+, K+, Cl-)
describe ion movement in passive ion channels
activator (ligand) binds to channel (ex. Neurotransmitter), channel changes conformation
how are chemically activated (ligan-gated) ion channels activated?
down concentration gradient (when open)
describe ion movement in chemically activated (ligand-activated) ion channels
voltage difference across membrane, channel changes conformation
how are voltage activated (voltage-gated) channels activated?
down concentration gradient (when open)
describe ion movement in voltage activated (voltage-gated) ion channels?
respond to mechanical stimulation (membrane distortion), ex: pressure, stretch, or vibration
how are mechanically gated channels activated?
when neuron reaches threshold value, voltage-activated ion channels activated, Na+ into neuron followed by K+ out, transmembrane potential becomes more positive
when does action potential occur?
voltage-activated ion channels have charge regions (gates) that sense level of change in transmembrane potential, open or close
why does an action potential occur?
activation and inactivation gate
what kind(s) of voltage-gated Na+ channel(s) are there?
only activation gate
what kind(s) of voltage-gated K+ channel(s) are there?
by pump activity and leak channels
how is resting membrane potential reestablished?
closed
describe the Na+ activation gate at resting
open
describe the Na+ inactivation gate at resting
closed
describe the K+ activation gate at resting
Na+ activation gate opens, Na+ flows through, K+ activation gate stays closed
how is threshold reached?
is becomes more positive (depolarization)
what happens to the transmembrane potential when threshold is reached?
repolarization
at what point during an action potential is there the peak positive value?
Na+ inactivation gate closes, K+ activation gate opens
what happens during peak positive value?
