Topic 16 Nervous System Basics Part 1

Properties of Neurons

Excitability, Conductivity, Secretion

Excitability

Secretion

2 types of neural tissue cells

nuerons and supporting cells

nuerons

the basic functional units of the nervous system - the communicators

supporting cells

cns and pns

cns

neuroglia - astrocytes, microglia, ependymal cells, oligodendrocytes

pns

satellite cells, schwann cells

major organelles of the cell body

large and nucleolus, cytoplasm, mitochondria, nissl bodies, cytoskeleton

nissl bodies

mechanism for creating our neurotransmitters

cytoskeleton elements

nuerofilaments and nuerotubules, neurofibrils

nuerofilaments abd nuerotubules

in place of microfilaments and microtubules

neurofibrils

bundles of nuerofilaments, support dendrites and axon

axon

only one per neuron

carries electrical signal to target

structures of the axon

axoplasm and axolemma, axon hillock and initial segment, collaterals, telodendria, and synaptic terminals

axoplasm

cytoplasm of axon, contains nuerotubules, neurofibrils, enzymes, organelles

axolemma

specialized cell membrane, covers the axoplasm

axon hillock

thick section of cell body, attaches to initial segment

initial segment

attaches to axon hillock

collaterals

branches of a single axon

telodendria

fine extension of distal axon

synaptic terminals

tips of axon

myelin

oligodendrocytes in CNS and Schwann cells in pns

nodes of ranvier

gaps between myelin segments

bundling of a nerve

endometrium surrounds each fiber, groups of fibers are bound into fascicles by perineurium, fascicles are bound together by epineuriumm

multiple sclerosis

oligodendrocytes and myelin sheaths of cns degenerate, replaced by hardened scar tissue

CNS Support Cells - astrocytes

create the blood bone barrier, wrap around blood vessels, pull up glucose, secrete nerve growth factor promotes synapse formation

sclerosis

damaged neurons replace by hardened mass of astrocytes

CNS Supporting Cells - microglia

spider like phagocytes, dispose of debris in areas of infection, trauma, or stroke

CNS Supporting Cells - ependymal cells

lines the spaces of ventricles and produce and circulate cerebrospinal fluid

CNS Support Cells (nueroglia)

satellite cells and schwann cell

satelite cells

protect neuron cell bodies

schwann cells

form myelin sheath in the peripheral nervous system

speed of nerve signal

diameter of fiber presence of myelin

different fiber types

fiber types - type a

large diameter : 268 mph

position, touch, pressure, motor control

fiber types - type b

medium diameter : 40 mph

Visceral sensory

fiber types - type c

small diameter and unmyelinated : 2 mph

temp, pain (burning, aching pain)

diameter of fiber presence of myelin

large fibers have more surface area for signals, myelinated faster than unmyelinated

2 methods of propagating action potenitals

continuous propagation and saltatory propagation

continuous propagation

action potentials along unmyelinated axons

affects 1 segment of axon at a time

saltatory propagation

action potential along myelinated axons

faster and uses less energy