nervous system

CNS

brain and spinal cord

interprets incoming sensory info

issues instructions based on past experiences

PNS

cranial nerves(12), spinal nerves(31 root pairs), ganglia(cell bodies), sensory receptors

communication lines carrying impulses toward(sensory) or away from(motor) CNS

Sensory division

PNS

Afferent/incoming

sensory info toward CNS

cell bodies OUTSIDE CNS

Motor division

PNS

Efferent/outgoing

motor info away from CNS to cause contraction

cell bodies INSIDE CNS

Somatic

PNS

voluntary

controls skeletal muscles

Autonomic

PNS

involuntary

controls smooth muscle, cardiac muscle and glands

sympathetic(Epi-adrenergic) and parasympathetic(Ach-cholinergic)

NS tissue population

neuroglia

neurons

neuroglia(glial cells)

90% of NS cells

support/helper cells

function: phagocytes, myelination, capillary-neuron exhange, control chemical environment

NO nerve impulse generation or transmition

CNS: astrocytes, oligodendrocytes, microglia, ependymal cells

PNS: Schwann cells, satellite cells

Neurons

generate and transmit nerve impulses

10% of NS cells

Cell body- makes up gray matter

dendrites- receive info

axons - conduct impulses bc its a nerve fiber

Axons

conduct impulses

end as axon terminals in synaptic cleft

in PNS are discontinuously myelinated by schwann cells to speed up communication

myelinated axons in CNS = white matter

Association neurons

interneurons

situated between and contribute to pathways connecting sensory and motor neurons

cell bodies INSIDE CNS

Nerve

bundle of neuron fibers wrapped in connective tissue coverings(fibers→fascicles→nerve)

can be sensory, motor or mixed(both ways)