Bio Ch 37 Flashcards
(72 cards)
Nerve net
composed of neurons in contact with one another and with contractile cells of the body wall in cnidarians
Cephalization
concentration of nervous tissue in the anterior or head region
Ganglion
cluster of neuron cell bodies
Central Nervous System (CNS)
brain, spinal cord
Peripheral Nervous System (PNS)
nerves, ganglia that lie outside the CNS
Neurons
nerve cells; functional units of the nervous system
Neuroglia
supporting cells, providing support and nourishment to the neurons
Cell body
contains a nucleus and a variety of organelles
Dendrites
short, highly branched processes that receive signals from the sensory receptors or other neurons and transmit them to the cell body
Axon
portion of the neuron that conveys info to another neuron or to other cells; can be bundled to form nerves
Nerve fibers
axons are often called this; many are covered by a myelin sheath
Myelin sheath
white insulating layer covering axons
Microglia
phagocytic cells that help remove bacteria and debris
Astrocytes
provide metabolic and structural support directly to the neurons
Schwann cells
cells that surround a fiber of a peripheral nerve and forms the myelin sheath
Nodes of Ranvier
gaps in the myelin sheath
Oligodendrocytes
in the CNS, these neuroglial cells form the myelin sheath
Motor (efferent) neurons
take nerve impulses from the CNS to muscles or glands
Sensory (afferent) neurons
take nerve impulses from sensory receptors to the CNS
Interneurons
occur entirely within the CNS; typically multipolar; convey nerve impulses between various parts of the CNS
Resting potential
membrane potential of an inactive neuron
Action potential
rapid change in polarity across a portion of an axonal membrane as the nerve impulse occurs
Saltatory conduction
action potential “jumps” from node to node (saltar in Spanish = to jump)
Refractory period
time following an action potential when a neuron is unable to conduct another nerve impulse