Cells of the Nervous System Review

Types of brain cells

1) Neurons 2) Glial Cells

Neurons

Receives input from cells, integrates it, and distributes it to other neurons, processing vast amounts of info

Glial Cells

Provide support for neurons and protects, insulates (with Myelin), and feeds them

Similarities between neurons and glial cells

Plasma membrane and organelles

Differences between neurons and glial cells

Morphology (shape), communication over long distances, and postmitotic

Camillo Golgi

Developed a staining method to see neurons under a light microscope

Santiago Ramon y Cajal

Developed the Neuron Doctrine

Neuron Doctrine

Neurons and other cells are independent

Synapses

The gaps in which neuron-to-neuron info is transmitted across

The 4 Principal Divisions of a Neuron

1) Input Zone 2) Integration Zone 3) Conduction Zone 4) Output Zone

Input Zone

Made of dendrites and soma, receives chemical signals from other cells, and converts chemical signals into electrical signals

Integration Zone

Located at the axon hillock, the soma combines all the electrical signals (the info) and decides whether or not to send out a signal

Conduction Zone

Made of the axon, carries the electrical signals away from the soma, occasionally aided by myelin and split into axon collaterals

Output Zone

Made of axon terminals, transmits the signals across synapses to other cells, releases neurotransmitters

Dendrites

Where neurons receive info via the synapses

Dendritic Spines

Projections from the dendrites that add more synapses

Soma

The cell body, combines received info and determines whether or not to send its own signal

Axon

The neuron's single extension that carries the electrical signals away from the soma

Myelin

The fatty, insulating sheath that speeds up electrical signals in the neuron

Axon Collaterals

Where the axon splits into multiple branches

Axon Terminals

The swellings at the ends of axons that transmit the neuron's signals across synapses

Motoneurons

Multipolar; Neurons that trigger movement, are large with long axons, reaching out to synapses on muscles

Sensory Neurons

Unipolar; Convey info from the sense organs to the brain

Interneurons

Most neurons (small); Receive Info from other neurons, process it, and pass it onto other neurons

Multipolar

Neurons have many dendrites and 1 axon; Most common

Bipolar Neurons

Have 1 dendrite and 1 axon at the end; brings smell, auditory, and light info

Unipolar Neurons

Have 1 axon, transmits touch, temperature, and pain

Neurotransmitters

Causes changes in the neuron; The chemical with which a presynaptic neuron communicates with postsynaptic cells

Synaptic Cleft

The tiny gap between two neurons where chemical signals pass from one to the other

Neuroplasticity

The capacity of neurons to constantly change their connections with other neurons

Axon Hillock

Decides action potential; the cone-shaped part of the soma

Oligodendrocytes

Myelinate axons in the CNS

Schwann Cells

Myelinate axons in the PNS

Astrocytes

Run in all directions of the neuron, star-shaped, help form tough outer membranes and secrete chemical signals that form synapses

Microglial Cells

Contain and clean up sites of injury

Oligodendrocytes and Schwann Cells

Wrap around segments of axons and insulate them with myelin

Nodes of Ranvier

The gaps between Myelin sheaths that are uninsulated axonal membrane

Phospholipid Bilayer

A double layer of fat molecules that form the cell membrane

Phospholipid

Phosphate head and fatty acid tail

Semipermeable

Some things flow freely through the membrane (oxygen, water, carbon dioxide)

Channel Proteins

Channels within the phospholipid bilayer that regulate what goes through the membrane (sodium, calcium, potassium, chloride)

Signal Protein

Located in the phospholipid bilayer, doesn't have a channel, but sends outside signals to the inside; it also doesn't move things in and out

Action Potential

Travels down the axon and causes the release of NT's from the terminal

Nervous System

CNS & PNS

CNS

Brain and spinal cord

PNS

Neural structures outside the brain/sc

Neural Tissue

Gray matter and white matter

Gray Matter

Made of Somas and dendrites; Less myelin

White Matter

Made of Axons; More myelin

Nucleus

Gray matter in CNS

Tract

White matter in CNS

Ganglion

Gray matter in PNS

Nerve

White matter in PNS

Blood-Brain-Barrier (BBB)

Helps supply neurons and protects them from toxins found in the blood of the brain

Endothelial Cells

Line the blood vessels and contain gases that allow things outside the blood

Tight Junctions

Formed by endothelial cells in the brain, making it more difficult to allow things inside

Pericytes

Constrict and dilate blood vessels

BBB lets through:

Oxygen, carbon dioxide, fat-soluble molecules (vit. A and D), glucose, water, and small uncharged molecules

BBB keeps out:

Charged molecules (sodium, chloride, etc.), viruses, bacteria, and medications

Circumventricular Organs

Brain regions that have incomplete BBB