Nerve Cells (neuron and glia)

Radial Glia

• Found in developing nervous system during embryonic stage
• Function: Guides the migration of neurons and their axons and dendrites.

Unipolar

• Located in the ganglia of the spinal nerves and some cranial nerves

Synaptic Receptors (part of dendrites)

lines the dendrite's surface, receives information from other neurons

Presynaptic Terminal (part of axon) BULB

points where axon releases chemicals that cross through the junction from one neuron to another cell.

Unipolar (structural classification)

• Single process, the axon

Sensory / Afferent (Functional classification)

Organs or sensory receptors to CNS
• Every sensory neuron is afferent to the rest of the nervous system
• Mostly unipolar

Motor / Efferent (Functional classification)

Away from CNS to organs, muscle, or glands.
• Every motor neuron is efferent from the nervous system.
• Mostly multipolar

Intrinsic / Interneuron (Functional classification)

Neurons between sensory and motor neurons.
• Dendrites and axons are within a single structure.
• Most abundant
• Mostly multipolar

Central Nervous System (CNS)

• Astrocytes
• Oligodendrocytes
• Ependymal Cells
• Microglial

Peripheral Nervous System (PNS)

• Satellite Cells
• Schwann Cells

Oligodendrocytes (CNS)

Function: Myelinate axons
in CNS
• Myelinate multiple axons (30-60 axons)
• Damages cannot be regenerated.
• Demyelination leads to multiple sclerosis -> potentially disabling disease of the brain and spinal cord (central nervous system

Schwann cells (PNS)

Myelinates axons in PNS
• 1 Schwann cell to 1 axon or multiple Schwann cells to 1 axon
• Damages can be regenerated.
• Demyelination leads to Guillian-Barre Syndrome (immune system attacks the nerves)

Epemdymal cells (CNS)

part of Blood Cerebrospinal Fluid Barrier
- Controls movement across the Blood CSF Barrier - Creates CSF
- Helps circulate CSF

Neurons

some of the longest-lived cells in the body.
• Cells in the cerebral cortex has the same life span as you currently have.

Neurons

vary in size, shape, and function.
• The shape determines its connection to other cells which determines its function.

Neurons

are irreplaceable.
• Most are amitotic (cannot divide).

Neurons

have huge appetite.
• need constant and abundant glucose and oxygen.

Astrocytes

Shields neurons from chemicals surrounding it.

Mitochondria

- Contains genes separate from nucleus

Central Nervous System (CNS)

has brain and spinal cord

Peripheral Nervous System (PNS)

Connects brain and spinal cord to the rest of the body (cranial, spinal, and autonomic nerves)

Neurons (nerve cells)

Receive information and convey the information to other cells.

Glia (nerve cells)

Enhance and modify the activity of neurons in many ways.

Neurons (nerve cells)

- There are small gaps between the tips of two neuron fibers. separated from each other

soma (cell body of neuron)

Metabolic center of neurons

nucleus (part of soma)

contains chromosomes

ribosomes (part of soma)

synthesize new protein molecules

mitochondria (part of soma)

- performs metabolic activities/energy provider.

Axon Hillock (part of soma)

connects soma to axon

Dendrites (part of neuron)

- Receives nerve impulses (toward cell body)
- Always naked/not myelinated
• Shorter, mostly microns and seldom
more than a millimeter

Dendric Spines (part of dendrite)

increase surface of dendrites.

axons (part of neuron)

- Transports impulses towards neurons/organs/muscle.
- AWAY FROM CELL BODY
- Myelinated or with myelin sheath
- Longer, Microns to meters

myelin sheath (part of axon)

insulating material

Nodes of Ranvier (part of axon)

interruptions between myelin sheaths

Classifications of neuron

structural and functional

Multipolar (Structural classification)

• 1 axon, multiple dendrites (2-12)

Bipolar (Structural classification)

• 1 axon, 1 dendrite

glia (type of nerve cell)

- Component of nervous system that has many functions
- From Greek word "glue"
- old idea that glia glue neurons together.

Astrocytes (part of CNS)

• Star-shaped

Satellite Cells (PNS)

- Sensory and Autonomic ganglia (cluster of nerves)
• Astrocytes of PNS

Microglia (CNS)

• Function: Part of immune system
- Destroys pathogens (viruses and fungi) that attacks or damages the neurons.
- Removes damaged neurons
- Removes weakest synapses (synaptic pruning)

Astrocytes

Regulates ions and transmitters that helps in synchronized sending of messages in waves.

Astrocytes

Part of Blood Brain Barrier (BBB).

Astrocytes

Secretes growth factors that stimulates endothelial cells to make more tight junctions (controls permeability)

Astrocytes

3. Glycogen reserve that helps in bringing nutrients to the brain.

Astrocytes

Increase interactions of synapses between neurons by releasing chemicals that magnify or modify the message to next neurons

Multipolar

• Located in all remaining nerve cells.
• Most common type

Bipolar

• Located in special sensory organs or visual, auditory and vestibular pathways: retina, olfactory nerves, inner ear.

Santiago Ramon y Cajal

(in 1800s) found out that by staining cells from infant brains using Golgi's method (staining nerve cells with silver salts)