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44 Cards in this Set
- Front
- Back
Neuron
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Basic structural unit of the nervous system; nerve cell
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Parts of a neuron
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Cell body, dendrite, axon
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Cell body
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Contains the nucleus and other organelles
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Dendrite
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A short, branched, slender extension of the cell body that receives stimuli
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Axon
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A long, slender extension of the cell body that sends nerve impulses
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Three groups of neurons
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Sensory/afferent neurons, motor/efferent neurons, association/interneuron neurons
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Sensory/afferent neurons
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Receive the initial stimulus. Ex: retina neurons
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Motor/efferent neurons
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Stimulate effectors
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Association/interneuron neurons
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Located in the spinal cord or brain and receive impulses from sensory neurons or send impulses to motor neurons.
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Effectors
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Target cells that produce some kind of response.
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Integrators
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Interneurons; evaluate impulses for appropriate responses.
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Polarized
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A difference in electrical charge between the outside and inside of the membrane
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How is polarization established?
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By maintaining an excess of sodium ions on the outside and potassium ions on the inside
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Resting potential
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Describes the unstimulated, polarized state of a neuron at about -70 millivolts
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Action potential
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Complete depolarization of about 30 millivolts
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Depolarized
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More positive on the inside than the outside
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Repolarization
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Caused by movement of potassium out of the cell, restoring the original membrane polarization.
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Hyperpolarization
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More potassium is outside the cell than is necessary to establish the original polarized potential. About -80 millivolts
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Refractory period
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Sodium and potassium are on the wrong sides. The neuron will not respond to a new stimulus.
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Myelin sheath
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Consists of a series of Schwann cells that encircle the axon
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Schwann cells
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Act as insulators and are separated by nodes of Ranvier
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Nodes of Ranvier
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Gaps of unsheathed axon
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Saltatory conduction
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Action potential jumping from node to node
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Synapse/synaptic cleft
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The gap that separates adjacent neurons
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Flow of an impulse across a synapse
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Presynaptic cell to postsynaptic cell. May be electrical or chemical.
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Gap junctions
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Small tubes of cytoplasm that connect adjacent cells in which electric signals move along.
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Excitatory postsynaptic potential (EPSP)
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Na gates open, membrane is depolarized
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Inhibitory postsynaptic potential (IPSP)
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K gates open, membrane is hyperpolarized
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Acetyl choline
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Secreted at neuromuscular junctions, stimulates muscles to contract. Can produce an inhibitory postsynaptic potential.
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Cholinesterase
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Breaks down acetyl choline
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Epinephrine
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Derived from amino acids, mostly secreted between neurons of the central nervous system
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Norepinephrine
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Derived from amino acids and secreted between neurons of the central nervous system
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Dopamine
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Derived from amino acids and secreted between neurons of the central nervous system
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Serotonin
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Derived from amino acids and secreted between neurons of the central nervous system
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Parts of the vertebrate nervous system
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Central nervous system and peripheral nervous system
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Central nervous system (CNS)
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Consists of the brain and spinal cord
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Peripheral nervous system
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Consists of sensory neurons that transmit impulses to the CNS and motor neurons that transmit impulses from the CNS to effectors.
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Groups of the motor neuron system
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Somatic and autonomic
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Somatic nervous system
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Directs the contraction of skeletal muscles
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Autonomic nervous system
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Controls the activities of organs and various involuntary muscles, such as cardiac and smooth muscles
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Two groups of the autonomic nervous system
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Sympathetic and parasympathetic
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Sympathetic nervous system
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Involved in the stimulation of activities that prepare the body for action
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Parasympathetic nervous system
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Activates tranquil functions, such as secretion of saliva
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Reflex arc
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A rapid, involuntary response to a stimulus. Consists of a sensory and motor neuron, sometimes an interneuron.
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