Section 4.1 Neuro-histology & Neurophysiology

what is the basic functional unit of the nervous system called

nerve cell/neuron

where are the nerve cells/neuron located

throughout the nervous system

several diff kinds of neurons in the human nervous system.

the neuron

what are the 3 basic parts of a neuron?

• axon

• neurosoma

• dendrite

the cell body & control center which contains the nucleus with a large nucleolus, cytoplasm, mitochondria, golgi apparatus, lysosomes, an extensive endoplasmic reticulum (ER), etc

neurosoma

a slender & long projection that rapidly conducts the signal away from the neurosoma; nerves only have 1 of these, but some nerves don’t even have 1, such as the one in the retina (sensory layer in the eyeball)

axon

primary site for receiving signals from other neurons, named for resembling tree branches; some neurons have only 1 dendrite & some have thousands, thus the more dendrites it has, the more information it can receive & incorporate into its decision making

dendrite

what are smaller branches arising from big & thicker dendrites called?

dendritic branches

in a cross-section of a nerve branch, superficially, it will show that it is covered by a layer of dense irregular connective tissue called?

epineurium

at low magnification, what is the group of neurons found inside the nerve branch that is similar to skeletal muscles

bundles of fascicles

what is the bundles of fascicles covered by?

layer of connective tissue called the perineurium

what do each separate neuron are covered by?

delicate thin layer of connective tissue called the endoneurium

axons may be what?

myelinated or unmyelinated

spiral layer of insulation around the nerve fiber & produced through myelination

myelin sheath

when present, a myelin sheath does wut?

• insulates the nerve axon from surrounding tissue

• increases the speed & efficiency of conduction

what is the name for the distal end of a axon?

axon terminal

the axon terminal is also a wut?

synapse

what happens in the axon terminal?

where a neurotransmitter such as acetycholine, epinephrine & serotonin is released & the next cell in the circuit responds to the neurotransmitter, just like in a neuromuscular junction

what are the 3 major categories that neurons can be grouped?

• multipolar neurons

• bipolar neurons

• pseudounipolar neurons

have multiple dendrites & 1 axon; the most common type

multipolar neurons

have 1 long dendrite & 1 axon; seen in the nerves of the retina

bipolar neruons

appears to have 2 branches & is shaped like a T, but in reality, it has a single axon with dendrites at 1 end & a synapse at the other; pseudo—means false

pseudounipolar neurons

what are some unique cellular structures of a multipolar neuron?

• axon hillock

• initial segment of axon

• neurofibrils

• telodendria

• axon terminal

• nissl bodies

a mound where the axon originates

axon hillock

the very first part of the axon coming out of the axon hillock

initial segment of axon

part of the cytoskeleton (cell framework) made up of bundles of actin filaments

neurofibrils

extensive complex fine branches that gives rise to the axon terminals

telodendria

a bulbous end, which forms the synapse to the next nerve

axon terminal

dark staining regions, made up of rough endoplasmic reticulum (ER) & free ribosomes; unique to neurons, which in turn helps with identifying them easily

nissl bodies

aka glial cells; they make up the majority of cells in the nervous system; glia means “glue”.

the neuroglia

what are the 5 glia cells that have various roles, which protect & support the structure & function of neurons

• astrocytes

• ependymal cells

• microglia

• oligodendrocytes

• schwann cells