Nervous System A&P Flashcards
nervous system definition
a highly specialized system responsible for control and integration of the body’s activities
components of nervous system
central nervous system (CNS) and peripheral nervous system (PNS)
CNS components
brain and spinal cord
PNS components
cranial/spinal nerves and autonomic nervous system
role of CNS ascending tracts
carry sensory information from the periphery, muscles, and organs to the higher levels of the CNS
role of CNS descending tracts
carry impulses from the brain and result in voluntary muscle movement
cells in the nervous system
neurons and neuroglia
neuron
primary functional unit of the nervous system
do not divide or replace themselves, but may generate from stem cells after a brain injury
neuroglia
–more numerous and supportive to the neuron
–can replicate
–when neurons are destroyed, the tissue is replaced by neuroglia cells
neuron structure
cell body, axon, and several dendrites
neuronal cell body
metabolic center of the neuron
dendrites
short extensions from the body that receive and conduct nerve impulses
axons
extend varying distances from the cell body and carry nerve impulses
myelinated or unmyelinated
myelin sheath
white lipid substance that insulates and helps conduct the impulses
role of neuroglia (glial cells)
provide support, nourishment, and protection to neurons
prevalence of glial cells
make up almost half the brain and spinal cord and are 5-10x more numerous than neurons
oligodendrocytes
produce the myelin sheath for nerve fibers in the CNS and help make up the “white matter” of the brain
Schwann cells
myelinate the nerve fibers in the periphery
astrocytes
provide structural support to neurons and form the BBB
where are astrocytes found?
“gray matter” of the brain
how does a nerve impulse work?
–initiation of a nerve impulse involves the generation of an action potential
–after the action potential is initiated, a series of action potentials travel along the axon
–when it reaches the end of the nerve fiber, it is transmitted across the junction between nerve cells by neurotransmitters
synapse
point at which the nerve impulse jumps from one neuron to another
neurotransmitter
chemical agent involved in the transmission of an impulse across this junction
examples of neurotransmitters
acetylcholine, epinephrine, norepi, serotonin, dopamine
