what is the nervous
master controlling and communicating system of the body
whats the three functions of the nervous system
sensory
integration
motor output
sensory
info. gathered by sensory receptors about internal and external changes
integration
processing and interpetation of sensory input
motor output
activation of effector organs(muscles and glands) produces a response
what two parts is the nervous sytem divided into
CNS
PNS
CNS
Brain and spinal cord
integration and control center
-interprets sensory input and dictates motor output
PNS
portion of nervous system outside the CNS
whats the two major neuroglia in the PNS
satellite cells
Schawnn cells
satellite cells
- surround neuron cell bodies in PNS
- function similar to astrocytes of CNS
Schawnn cells(neurolemmocytes)
surround all peripheral nerve fibers and form myelin sheaths in thicker nerve fibers
whats the structural units of the nervous system
neurons(nerve cells)
whats the special characteristics of neurons
extreme longevity(lasts a person’s lifetime)
Amitotic, with few exceptions
high metabolic rate: requires continous supply of oxygen and glucose
all have soma and one or more processes
biosynethetic center of neuron
- synthesizes proteins,membranes, chemicals
- rough ER(chromatophilic substance, or NIssl bodies)
what can some neurons contain
pigments
whats the receptive region in most neurons
plasma membrane, is the receptive region that receives input info from other neurons
where are most neuron somas located
cns
nuclei
clusters of neuron cell bodies in the CNS
Ganglia
clusters of neuron cell bodies in PNSs
tracts
bundles of neuron processes in CNS
nERVES
budles of neuron processes in PNS
describe the arm-like processes that extend from the the soma in the CNS and PNS
cns- contains both neuron cell bdies and their processes
pns- contains chiefly neuron processes
Dendrite
motor neurons can contain 100s
-contain same organelles as in cell body
what does Receptive (input) region of the neuron do
converys incoming messages toward cell body as GRADED POTENTIALS(short distance signals)
what are finer dendrites needed for
in many brain areas, finer dendrites are highly specializes to collect info
- contain dendritic spines, appendages w/ bulbous or spiky ends
what does seach neuron have
an axon.
each neuron has one axon that starts at cone-shaped area called the axon hillxox
what are long axons called
nerve fibers
whats the side branches on an axon called
collateral
whats the conducting region of the neuron
axon
-generates nerve impulses and transmits them along neuron cell membrane to axon terminal
axon terminal
region that secretes neurotransmitters, which are released into extracellualr space
-can excite or inhibit
what does axons rely on to renew proteins
axons rely on cell bodies to renew proteins and membranes
-they can quickly decay of cut or damaged
describe and axons transport mechanism
molecules and organelles are moved along axons by motor proteins and cytoskeletal elements
anterograde
away from the cell body
ex: mitochondria, cytoskeletal elements, membrane components, enzymes
retrograde
towad cell body
ex: organelles to be degraded,signal molecules, viruses and bacterial toxins
what the function of mylein
protect and electrically insuate axon
increase speed of nerve impulse transmission
myelinated fibers
segmentated sheath surrounds most long ot large diameter axons
nonmyelinated fibers
do’nt contain sheath
conduct impulses more slowly
neuron are highly____
excitable
when gated channels are open, ions diffuse quickly:
along chem concentration graients from higher concentration to lower concentration
-along electrical gradients toward opposite electrical charge
what can measure potential(charge) difference across th emembrane of a resting cell
voltmeter
whats the resting membrane potential (RMP)
approx. -70mV
cytoplasmic side of membrane is negatively charged relative to the outside
whats the differences in onic composition
1)ECF has higher concentration of Na+ than ICF
- balanced chiefly by chloride ions (Cl-)
2) ICF has higher concentration of K+ than ECF
-balanced by negatively charged proteins
3) K+ plays most important role in membrane potential
differences in plasma membrane permeability