Ch. 12 - cells

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central nervous system

brain and spinal cord

peripheral nervous system

cranial nerves and spinal nerves

afferent pathways

acending pathways, carry impulses toward CNS, part of PNS

efferent pathways

descending pathways, carry impulses away from CNS, part of PNS

somatic nervuos system

regulates voluntary motor control

autonomic nervous system

involuntary control of organ systems

neuron

primary nervous system cell

neuroglial cell

in CNS, provides structural support and nutrition

Schwann cell

in PNS, provides structuralsupport and nutrition

this cell type produces myelin sheeth

Schwann cell

this cell type conducts impulses to cell body

dendrite

myelin

insulator that allows ions to flow between segments rather than along entire length of membrane; increases velocity of ignal

saltatory conduction

Rapid transmission of a nerve impulse along an axon, resulting from the action potential jumping from one node of Ranvier to another, skipping the myelin-sheathed regions of membrane.

nodes of Ranvier

gaps between the myelin wrappings along the axon

divergence

ability of axonal branches to influence MANY neurons

convergence

branches of various neurons all influence a single neuron

unipolar neurons

have one process that branches shortly after leaving cell body

pseudounipolar neurons

have one process; the dendritic portion of each of these extends away from the CNS and axon projects into CNS

bipolar neurons

two distinct processes arising from cell body

multipolar neurons

most common type, have multiple processes capable of extensive branching

ex. unipolar neurons

neurons found in retina

ex. pseudounipolar neurons

sensory neurons in cranial and spinal nerves

ex. bipolar neurons

neurons connecting rod and cone cells of retina

ex. multipolar neurons

motor neurons

neurons: structural classifications

four types, based on number of processes extending from cell body

types of neurons

sensory, associational, motor

sensory neurons

afferent, mostly pseudounipolar (carry signals from peripheral sensory receptors to the CNS)

associational neurons

interneurons, multipolar (transmit signals from neuron to neuron)

motor neurons

efferent, multipolar (transmits signal away from CNS to an effector, such as skeletal muscle or organ

neuromuscular junction

end processes of motor neurons form in skeletal muscle

neuroglia

"nerve glue" - cells that support neurons of CNS

astrocytes

fill spaces between neurons and surround CNS blood vessels

oligodendroglia

deposit myelin within CNS, CNS equivalent of Schwann cells

microglia

phagocytosize debris in CNS

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