nervous system Flashcards
(38 cards)
neurons
nerve cells that conduct signals, nucleated body, dendrites= nerves receptive apparatus, axon= long+carries away impulses, myelin= fatty sheath covered axon
central nervous system
brain + nerve cord= interneurons conduct impulses= 99% of all neurons
peripheral nervous system
afferent and efferent
afferent (sensory) neurons
conduct sensory info from body to CNS
efferent (motor) neurons
conduct motor info from CNS to the body
nerves
collections of axon bound together by connective tissue
ganglia
collections of neuronal cell bodies lying in the PNS
neuroglia
(glial=glue) non-nervous cell support neurons (keep glued together)
Schwann cells
forms myelin in the PNS
oligodendrocytes
forms the myelin in the CNS
nerve action potential
all nerve signals use electro-chemical message, relies on ion exchange across neuron membrane alter change inside cell
action potential
all or none phenom- either conducting signal or not
membrane potential
difference in electrical charge between inside/outside cell at rest neuron= more (-) than fluid
sodium-potassium pump
moves sodium and potassium in opp. directions against its concentration gradient (channels specific to either)
voltage gated= open v. closed depends on membrane potential
depolarization (rising phase)
Changes in membrane potential causes voltage-gated Na+ channels to open.
Na+ rush into the axon from the outside.
Interior becomes slightly positive with respect to exterior, membrane is depolarized.
repolarization
Na+ gates close.
K+ gates open and K+ ions move out.
Reestablishes the resting membrane potential.
Interior once again negative with respect to the exterior.
A new action potential cannot occur because the sodium is inside and the potassium is outside.
Sodium-potassium pump re-establishes the resting potential
synapse
Junction between two neurons or a neuron and an effector (muscle or gland).
An action potential passing down an axon must cross a small gap, the synapse
presynaptic knobs release neurotransmitters.
One of the most common is acetylcholine
Neurotransmitters
Diffuse across the gap in a fraction of a millisecond.
Bind to receptor molecules on ion channels in the postsynaptic membrane.
Causes a voltage change in the postsynaptic membrane.
conduction and myelination
Nodes of Ranvier are exposed areas of the axon between adjacent regions of myelin.
Myelin insulation prevents depolarization, which, therefore, only occurs at the nodes.
Increases the speed of conduction.
saltatory conduction
describes jumping behavior of the action potential which leaps from node to node.
bilateral nervous system
sponges lack nerves or true neural cell types
cnidaria have a nerve net
flatworms= simplest system
nervous system of arthropods
annelids= advanced to segments ganglia ganglia are larger, better developed sense organs
encephalization
Increase and elaboration in size of the brain.
The brain and spinal cord compose the central nervous system.