This preview shows pages 1–3. Sign up to view the full content.
This preview has intentionally blurred sections. Sign up to view the full version.View Full Document
Unformatted text preview: 0B X X X X X X X X X I I I X X X . . . N N N e e e r r r v v v e e e C C C o o o n n n d d d u u u c c c t t t i i i o o o n n n 1B N N N e e e u u u r r r o o o n n n s s s 4B F F F u u u n n n c c c t t t i i i o o o n n n The role of the nervous system is to collect, process, and respond to external and internal stimuli. The cells comprising the nervous system, neurons, are highly specialized for the one of these three functions they perform. sensory neurons take information in; interneurons are responsible for transmittal of information into and out of the central nervous system; motorneurons transmit information to effectors like muscle and glands. 5B S S S t t t r r r u u u c c c t t t u u u r r r e e e o o o f f f n n n e e e u u u r r r o o o n n n s s s Nerve cells have a variety of morphologies, but they are all variations on a common theme. Fig. 48-4 Dendrites Stimulus Nucleus Cell body Axon hillock Presynaptic cell Axon Synaptic terminals Synapse Postsynaptic cell Neurotransmitter The cell body, called the soma, contains the nucleus, mitochondria, and other organelles. The cell body has long projections that transmit electrical impulses. These projections transmit the impulses either toward the cell body or away from it. The former (on the receiving end) are called dendrites, and the latter (on the outgoing end) are referred to as axons. Axon ends are split into terminal boutons. The terminal boutons make contact with other cells. These intercellular contacts are called synapses. Axons can be very long (e.g. a meter in an elephant), and a bundle of axons is commonly referred to as a nerve. 2B G G G l l l i i i a a a l l l C C C e e e l l l l l l s s s Apart from neurons, the nervous system also has a variety of support cells. Neuroglia, in the brain, amount to 90% of all cells; among other things, they mop up excess ions. Schwann cells are the “insulation tape” of axons. They are thin and flat and wrap around the axons forming a lipid blanket, a myelin sheath. Oligodendrocytes have a similar function in the brain Astrocytes are responsible for selective metabolite transport from blood capillaries to neurons....
View Full Document