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56 Cards in this Set

  • Front
  • Back
Major cell types in nervous system (2)
Glial cells and neurons
Classes of glial cells (2)
Microglia and Macroglia
Function of Glial Cells
-Surround and support neurons
-Produce Myelin
-Occasionally take up neurotransmitters
-Scavenger function
-Guidance of migrating neurons during development
-Help for blood-brain barrier
-Nourish neurons (growth factors)
Microglia
-Phagocytes which are mobilized after injury, infection, disease
-Secrete signaling molecules that modulate local inflammation
-Increase following neural injury
Diseases Microglia are involved in
AIDS related dimentia, Parkinson's, Alzheimer's, MS
Macroglia Types (Small and Large)
Small - Oligodendrocytes and Schwann Cells
Large - Astrocytes
Where Macroglia Are Found
Oligodendrocytes - CNS
Schwann Cells - PNS
Astrocytes
-Most numerous
-Potential role in nutrion of neurons
-Help maintain proper ion concentration in extra-cellular space (K+)
-Take up Neurotransmitters from synaptic zone
Action Potential
Rapid, transient, all-or-none impulses w/constant amplitude of 100mV and duration of 1ms
Myelin Sheath
-Increase speed of conduction
-Nodes of Ranvier
Principle of Dynamic Polarization
-Unidirectional flow of electrical signals within neurons
-from dendrites to axon hillock
-from trigger region, action potential propagated through length of axon to presynaptic terminals
Principle of Connectional Specificity
-Each cell makes specific connections wiht certain postsynaptic target cells
-Specific pattern of connections mediate function
Unipolar Neuron
-Simplest, single process that serves as receptor and releasing terminal
-Afferent and efferent
-Autonomic Nervous System
Biopolar Neuron
-Two processes (Dendrite and axon), seen in sensory system
Pseudo-unipolar Neuron
-Develops as bipolar cells; processes fuse to form one axon, one peripheral and one central (Seen in mechanoreceptors)
-Somatosensory system
Multipolar Neuron
Single axon, many dendrites; most common
Sensory Neurons
-Afferent
-Monitoring of internal state of body
-Monitoring external environment (Perception and motor coordination)
-Away from stimulus
Motor Neuron
-Efferent
-Carry signals TO muscles and glands
-Cause muscular contraction
Interneurons
-Largest class of cells
-Local information processing
-Axons remain within CNS
-Two types - Projection and Local
Projection Interneuron
-Golgi Type I
-Connect to regions in CNS
-Relay information across great distances
Local Interneuron
-Golgi Type II
-Relay information locally
-Example: within same segmental level
Principle of Divergence
-Each sensory neuron connects with 100-150 motor neurons
-Common input stage of nervous system
Principle of Convergence
Single motor neuron recieves input from many sensory neurons
Feed-Forward Inhibition
-Inhibitory connection of sensory neuron with antagonist of quadriceps
-Inhibit muscles so only appropriate muscles are recruited
Feedback Inhibition
-Excitatory connection between sensory neuron and motor neuron innervating quadriceps dampened by inhibitory connection to pathway
-Self regulation to ensure stimulation does not have prolonged motor output
Resting Membrane Potentail
-Negative potential inside neuron at rest compared to outside of cell
-Typically between -40 to -90mV (-65mV)
Ionic Basis of Resting Membrane Potential is Based on Two Factors:
-Unequal distribution of positive (Na+/K+) ions and negatively charged amiono acids and proteins across membrane
-Selective permeability of membrane to K+
Unequal Distribution of Ions Maintained By:
-Na+/K+ Pump that pumps Na+ Out and K+ In.
Negative Resting Potential is Due to?
-Membrane potential more permeable to K+ at rest; causes leakage of K+ from inside to outside of cell
-More negative charge inside
Depolarization
-Reduction in membrane potential from -65mV (to -55mV)
-Enhances ability of cell to generate action potential
-Excitatory
Hyperpolarization
-Increases in membrane potential from -65mV (to -75mV)
-Decreases ability to generate action potential
-Inhibitory
Receptor Potentials
-Occur in Sensory Neurons
-Response to stimuli
-Resting potential changed for fraction of a second
-Response is graded-depends on stimulus amplitude
-Local signal-decays within certain distance (1-2mm)
Synaptic Potentials
-Receptors on receiving neuron uptake neurotransmitters from synaptic cleft
-Brief change in resting membrane potential
-Response graded-depends on number of synapses activated
Conductile Component
-Action Potential
-All-or-None
-Brief (1ms), Fast (100m/s)
-Does not decay with travel due to regeneration
-AP is stereotypical
How Action Potentials Differ?
Number of potentials per unit time (frequency) and overall duration of stimulation
Multipolar Neuron
Single axon, many dendrites; most common
Sensory Neurons
-Afferent
-Monitoring of internal state of body
-Monitoring external environment (Perception and motor coordination)
-Away from stimulus
Motor Neuron
-Efferent
-Carry signals TO muscles and glands
-Cause muscular contraction
Interneurons
-Largest class of cells
-Local information processing
-Axons remain within CNS
-Two types - Projection and Local
Projection Interneuron
-Golgi Type I
-Connect to regions in CNS
-Relay information across great distances
Local Interneuron
-Golgi Type II
-Relay information locally
-Example: within same segmental level
Principle of Divergence
-Each sensory neuron connects with 100-150 motor neurons
-Common input stage of nervous system
Principle of Convergence
Single motor neuron recieves input from many sensory neurons
Feed-Forward Inhibition
-Inhibitory connection of sensory neuron with antagonist of quadriceps
-Inhibit muscles so only appropriate muscles are recruited
Feedback Inhibition
-Excitatory connection between sensory neuron and motor neuron innervating quadriceps dampened by inhibitory connection to pathway
-Self regulation to ensure stimulation does not have prolonged motor output
Resting Membrane Potentail
-Negative potential inside neuron at rest compared to outside of cell
-Typically between -40 to -90mV (-65mV)
Ionic Basis of Resting Membrane Potential is Based on Two Factors:
-Unequal distribution of positive (Na+/K+) ions and negatively charged amiono acids and proteins across membrane
-Selective permeability of membrane to K+
Unequal Distribution of Ions Maintained By:
-Na+/K+ Pump that pumps Na+ Out and K+ In.
Negative Resting Potential is Due to?
-Membrane potential more permeable to K+ at rest; causes leakage of K+ from inside to outside of cell
-More negative charge inside
Depolarization
-Reduction in membrane potential from -65mV (to -55mV)
-Enhances ability of cell to generate action potential
-Excitatory
Properties of Action Potential
-Active influx of Na+ at Nodes of Ranvier leading to depolarization
-Passive flow of Na+ ions along axon towards axon terminal
-Since node of Ranvier is only point of Na+ influx, action potential seems to jump from node to node
Electrical Synapse
-Presynaptic and postsynaptic cells linked at gap junction
-Gap junction have aligned channels in both cells
-Allow for flow of passive ionic current
-Flow of current is bidirectional
Gap Junction
-Transmission is very fast
-Help in synchronizing activity across neurons
-Gap junctions used by glial cells
Neurotransmitters
-Either small molecule or peptides
-Small molecules synthesized in axon terminal
-Peptides synthesized in cell body
-Both can be released from same axon terminal
Release of Neurotransmitter
-At neuromuscular junction - specialized region of muscle fiber called end plate - motor neuron axon terminal contact
-Action potential in motor neuron causes depolarization of muscle fiber (end plate potential)
Role of Calcium
-Action potential causes opening of Ca++ channels
-Increase of Ca++ causes binding of vesicles to membrane and release of neurotransmitters
-Decrease of presynaptic Ca++ decreases the amount of neurotransmitter released