Nervous Tissue Flashcards
what is the structural and functional unit of the nervous system?
neuron
what do neurons constitute? (3)
most sensory receptors
conducting pathways
integration centers
where are most neuron cell bodies located?
CNS
all neurons terminally differentiated (Go)…
do not divide, although regeneration of axons is possible
what are the two basic cell types of nervous tissue?
neurons supporting cells (non-conducting)
what do supporting cells provide? (3)
physical support snd protection
electrical insulation
metabolic exchange
3 categories of supporting cells
neuroglia in CNS
Schwann cells in PNS
stellate cells in ganglia
soma contains
nucleus surrounded by cytoplasm
cell body
perikaryon
area around the nucleus
Kissel substance
rough ER
neurilemma
plasma membrane surrounding the cell
melanin, lipofuscin
age pigment within the cell body
neuronal dendrites
one or more highly branched neuron processes
dendrites receive stimuli from
other neurons or environment (afferent)
single axon
transmits stimuli to other neurons or effector cells (efferent)
axon arises from
Saxon hillock
axon hillock terminates in the distal swelling called the
terminal bouton
axonal transport
movement of products down the axon
slow axonal transport carries
cytoskeletal elements
fast exon transport carries
membrane bound organelles
anterograde transport
from cell body down the axon
used kinesis
retrograde transport
from axon to cell body
uses dynein
multi-polar neuron
most common, several dendrites
ex. motor neurons, interneurons
bipolar
single dendrite opposite axon
ex. receptor neurons of retina
unipolar
no dendrites on soma, axon only
ex. sensory neurons
pseudo unipolar
insult dendrite and axon fuse, soma off to one side
ex. dorsal root ganglion
Na+ and Cl- are higher – the cell
outside
K+ is higher – the cell
inside
resting membrane potential inside the cell
~80 mV
action potential is an – or none response
all
action potential arises in the cell body as a result of an
affect stimulus
causes region of the plasma membrane to
depolarize
causes reversal of resting potential, cells electrical potential
neutralized (goes to zero, or slightly positive)
during the refractory period,
na+ channels close and can’t reopen for another 1-2 msec
Na+ is unresponsive to the stimuli
refractory period is initially —, where response to stimulus is impossible, then —, where only a very strong stimulus can initiate depolarization
absolute
initial