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64 Cards in this Set
- Front
- Back
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Neural signaling (4 processes)
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Reception
transmission untegration action by effectors |
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Reception
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-process of detecting a stimulus
-job of the neurons and of sensory receptors |
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Transmission
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process of sending messages along a neuron
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CNS
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-central nervous system
-brain & spinal cord -afferent neurons transmit info to CNS -contain interneurons |
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afferent neurons
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-transmit info to CNS
-sensory neurons -transmit info to interneurons |
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Interneurons
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-in CNS
-association neurons -integrate input and output |
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Integration
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sorting and interpreting incoming sensory info and determining correct response
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efferent neurons
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-transmit info from CNS to effectors (muscles & glands)
-motor neurons |
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PNS
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peripheral nervous system
sensory receptors, afferent, efferent neurons |
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Glial cells
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-provide metabolic & structural support
-make up the neuroglia -3 types |
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Microglia
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-glial cell
-phagocytic celss that remove cellular debris |
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Astrocytes
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-glial cell
-star-shaped cells that provide neurons w/glucose |
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Oligodendrocytes
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-glial cell
-envelop neurons in CNS consisting of myelin |
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Schwann cells
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-glial cell
-envelope neurons in PNS consisting of myelin |
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Cell body of Neuron
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-largest portion
-contains nucleus,cytoplasm, organelles |
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Dendrites
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-cytoplasmic extensions of cell body
-short, highly branched -receive stimuli and send nerve impulses to cell body |
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Axon
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-cytoplasmic extensions of cell body
-it ends by branching into synaptic terminals -have myelin sheaths |
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Synaptic terminals
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release neurotransmitters
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Nodes of ranvier
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-gaps in myelin sheaths
-occur b/t schwann cells |
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Nerve
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consists of a lot of axons wrapped together in connective tissue
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Tracts
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-Bundles of axons w/in CNS
-instead of nerves |
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Ganglia
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-Cell bodies grouped together in masses outside the CNS
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Membrane potential
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voltage measured across the plasma membrane
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Resting potential
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70 mV (millivolts)
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Factors determining membrane potential
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-diffrences in concentrations of specific ions inside the cell compared with exracellular fluid
-selective permeability of the plasma membrane |
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factors causing resting potential
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(1) Na-K pump
(2) membrane permeability (3) negative charge inside |
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Na-K pump
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-transports 3 Na+ outside for every 2 K+ inside.
Therefore: -outside of membrane has positive charge -Na+ higher on outside |
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Membrane permeabilty relative to resting potential
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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.
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Negative charge inside membrane relative to resting potential
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(-)charged Cl- ions accumulate on inside the p.m.
(-)charged proteins are trapped inside. Both Cl ions & proteins contribute to (-) charge inside membrane |
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Depolarization
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-when a stimulus causes the membrane potential to become less negative.
-excitatory |
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Excitatory
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brings a neuron closer to transmitting a neural impulse
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Hyperpolarized
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-membrane potential becomes more negative than resting potential.
-inhibitory |
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Inhibitory
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Decreases the ability of the neuron to generate a neural impulse
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Graded potential
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-local response that functions as a signal over short distances
-varies in magnitude; potential charge varies depending on strength of the stimulus |
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Action impulse
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If a stimulus is strong enough, a neuron fires a nerve impulse.
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Action potential
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electrical excitation that travels rapidly down the axon the axon into the synaptic terminals
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Threshold level
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-action potential generated
-when depolarization is greater than -55mV. |
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Spike
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-Neuron membrane reaches zero potential & overshoots to +35mV.
-IOW: momentary reversal in polarity takes place -the sharp rise & fall in action potential |
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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+. |
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Repolarization
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-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. |
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Absolute refractory period
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Axon membrane cannot transmit another action potential
-b/c Na+ channels are inactivated |
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Magnitude of Action potential
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"height of spike"
- weak stimulus will generate a spike of exactly the same size as a strong stimulus |
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Intensity of sensations
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-depends on # of neurons stimulated & freq. of discharge
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Continous Conduction
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wave of depolarization in unmyelinated neurons
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Saltatory conduction
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-Myelin: electrical insulator
-ion movement occurs at the nodes -action potential jumps from one node 2 another -conducts impulse 50X faster. -uses less ATP |
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Synapse
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-junction b/t 2 neurons
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Presynaptic neuron
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neuron that terminates at a specifc synapse
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Postsynaptic neuron
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Neuron that begins at a synapse
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2 kinds of synapses
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Electrical & chemical
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Electrical synapse
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presynaptic & postsynaptic neurons occure close 2 each other & form gap juntions
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Chemical synapses
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Presynaptic % postsynaptic cells are seperated by a synaptic cleft
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Neurotransmitters & action potential
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-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. |
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Ligand gated channels
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Neurotransmiiter binds to receptors
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acetylcholinesterase
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degrades acetylcholine (which aids neurotransmitter)
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Reuptake
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neurotransmitter is activley transported back to terminals and repackaged in2 vesicles
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EPSP
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-excitatory postsynaptic potential
-change in membrane potential that brings the neuron close to firing |
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IPSP
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inhibitory postsynaptic potential
- membrane potential more negative -takes neuron farther away from firing level |
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Temproal summation
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repeated stimuli cause new EPSPS's to develop.The summation of EPSP's brings neuron close to firing level
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Spatial summation
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occurs when several closely spaced synaptic terminals release neurotransmitters simultaneously.postsynaptic neuron is stimulated at once
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Neural cicruits
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neurons are organized into pathways
3 main types: -converging -diverging -reverberating |
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Converging circuits
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several presynaptic neurons synapse w/ one postsynaptic neuron
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Diverging circuits
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singlw presynaptic neuron synapses w/several postsynaptic neurons
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Reverberating circuits
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signal returns to original location
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Reverberating circuits
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signal returns to original location
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