Ap Biology Nervous System Vocabs

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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.