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64 Cards in this Set

  • Front
  • Back
Neural signaling (4 processes)
Reception
transmission
untegration
action by effectors
Reception
-process of detecting a stimulus
-job of the neurons and of sensory receptors
Transmission
process of sending messages along a neuron
CNS
-central nervous system
-brain & spinal cord
-afferent neurons transmit info to CNS
-contain interneurons
afferent neurons
-transmit info to CNS
-sensory neurons
-transmit info to interneurons
Interneurons
-in CNS
-association neurons
-integrate input and output
Integration
sorting and interpreting incoming sensory info and determining correct response
efferent neurons
-transmit info from CNS to effectors (muscles & glands)
-motor neurons
PNS
peripheral nervous system

sensory receptors, afferent, efferent neurons
Glial cells
-provide metabolic & structural support
-make up the neuroglia
-3 types
Microglia
-glial cell
-phagocytic celss that remove cellular debris
Astrocytes
-glial cell
-star-shaped cells that provide neurons w/glucose
Oligodendrocytes
-glial cell
-envelop neurons in CNS consisting of myelin
Schwann cells
-glial cell
-envelope neurons in PNS consisting of myelin
Cell body of Neuron
-largest portion
-contains nucleus,cytoplasm, organelles
Dendrites
-cytoplasmic extensions of cell body
-short, highly branched
-receive stimuli and send nerve impulses to cell body
Axon
-cytoplasmic extensions of cell body
-it ends by branching into synaptic terminals
-have myelin sheaths
Synaptic terminals
release neurotransmitters
Nodes of ranvier
-gaps in myelin sheaths
-occur b/t schwann cells
Nerve
consists of a lot of axons wrapped together in connective tissue
Tracts
-Bundles of axons w/in CNS
-instead of nerves
Ganglia
-Cell bodies grouped together in masses outside the CNS
Membrane potential
voltage measured across the plasma membrane
Resting potential
70 mV (millivolts)
Factors determining membrane potential
-diffrences in concentrations of specific ions inside the cell compared with exracellular fluid
-selective permeability of the plasma membrane
factors causing resting potential
(1) Na-K pump
(2) membrane permeability
(3) negative charge inside
Na-K pump
-transports 3 Na+ outside for every 2 K+ inside.
Therefore:
-outside of membrane has positive charge
-Na+ higher on outside
Membrane permeabilty relative to resting potential
The membrane is more permeable to K+. K+ moves easily outside passing down the concentration gradient. This contributes to the positive charge outside the cell.
Negative charge inside membrane relative to resting potential
(-)charged Cl- ions accumulate on inside the p.m.
(-)charged proteins are trapped inside.

Both Cl ions & proteins contribute to (-) charge inside membrane
Depolarization
-when a stimulus causes the membrane potential to become less negative.
-excitatory
Excitatory
brings a neuron closer to transmitting a neural impulse
Hyperpolarized
-membrane potential becomes more negative than resting potential.
-inhibitory
Inhibitory
Decreases the ability of the neuron to generate a neural impulse
Graded potential
-local response that functions as a signal over short distances
-varies in magnitude; potential charge varies depending on strength of the stimulus
Action impulse
If a stimulus is strong enough, a neuron fires a nerve impulse.
Action potential
electrical excitation that travels rapidly down the axon the axon into the synaptic terminals
Threshold level
-action potential generated
-when depolarization is greater than -55mV.
Spike
-Neuron membrane reaches zero potential & overshoots to +35mV.
-IOW: momentary reversal in polarity takes place
-the sharp rise & fall in action potential
Voltage-activated Na+ channels
(action potential)
-when volt. reaches threshold activation gate opens
-Na+ flows thru channel making inside neuron positive.
-Inactvtn gate closes, stopping Na+.
Repolarization
-when inactvtn gates close & membrane returns to resting level.
-volt-gated K+ channels open. K+ leaks out of neuron.
-the decrease in intracellular K+ returns the interiorof the membrane to (-) state, repolarizing.
-K+ channels remain open until resting potential is restored.
Absolute refractory period
Axon membrane cannot transmit another action potential
-b/c Na+ channels are inactivated
Magnitude of Action potential
"height of spike"
- weak stimulus will generate a spike of exactly the same size as a strong stimulus
Intensity of sensations
-depends on # of neurons stimulated & freq. of discharge
-
Continous Conduction
wave of depolarization in unmyelinated neurons
Saltatory conduction
-Myelin: electrical insulator
-ion movement occurs at the nodes
-action potential jumps from one node 2 another
-conducts impulse 50X faster.
-uses less ATP
Synapse
-junction b/t 2 neurons
Presynaptic neuron
neuron that terminates at a specifc synapse
Postsynaptic neuron
Neuron that begins at a synapse
2 kinds of synapses
Electrical & chemical
Electrical synapse
presynaptic & postsynaptic neurons occure close 2 each other & form gap juntions
Chemical synapses
Presynaptic % postsynaptic cells are seperated by a synaptic cleft
Neurotransmitters & action potential
-neurotransmitters are stores in terminals w/in vesicles.
-volt.-gated Ca+ channels open. Ca+ flows from outside
-Ca+ ions aid in fusing vesicles with membrane.
-Neurotransmiiters diffuse across cleft to next neuron.
Ligand gated channels
Neurotransmiiter binds to receptors
acetylcholinesterase
degrades acetylcholine (which aids neurotransmitter)
Reuptake
neurotransmitter is activley transported back to terminals and repackaged in2 vesicles
EPSP
-excitatory postsynaptic potential
-change in membrane potential that brings the neuron close to firing
IPSP
inhibitory postsynaptic potential
- membrane potential more negative
-takes neuron farther away from firing level
Temproal summation
repeated stimuli cause new EPSPS's to develop.The summation of EPSP's brings neuron close to firing level
Spatial summation
occurs when several closely spaced synaptic terminals release neurotransmitters simultaneously.postsynaptic neuron is stimulated at once
Neural cicruits
neurons are organized into pathways
3 main types:
-converging
-diverging
-reverberating
Converging circuits
several presynaptic neurons synapse w/ one postsynaptic neuron
Diverging circuits
singlw presynaptic neuron synapses w/several postsynaptic neurons
Reverberating circuits
signal returns to original location
Reverberating circuits
signal returns to original location