Neurons & Glia

Neuron functions? 4 lines answer :v

Process infor

Sense environment change

Communicate changes to other neurons

Command body response

Glia functions?

Support, insulate, nourish neurons

2 Types of histology stain technique

Nissl (Cresyl violet) and Golgi stain

Nissl / Cresyl Violet stain

Target negatively charged molecule, DNA, RNA.

Good for figuring out anatomical neuronal cell body distribution / density

Golgi stain

Apply to preserved fixed tissues.

Good for figuring out detailed cell morphology (shape/ structure)

The Neuron Doctrine

Neuron is the smallest building block of the nervous system

Neural circuitry (same with cell theory)

Neurons communicate by contact, not continuity

Special characteristics of neurons

Longevity

Amitotic, with few exceptions

High metabolic rate: require continuous supply of oxygen and glucose.

Neuron cell body - soma contain:

Cytosol

Organelles: Ribosomes, sooth ER and Golgi apparatus, mitochondria

Cytoplasm

Nucleus

The cytoskeleton made up of 2 structures:

Microtubules: associated proteins MAPS implicated in dementia

Microfilament: actin protein for change shape

Neurofilaments: the strongest & most rigid.

2 types of processes

Dendrites

Axon

Dendrites characteristics:

Receptive input region of neuron.

Some dendrites are highly specialized to collect information by contain dendritic spines

The Axon structure

Cone-shaped called axon hillock.

Branches called axon collaterals

Distal endings called axon terminals or terminal boutons

Axon functional characteristics

Conducting region of neuron

Generates nerves impulses and transmits them along axolemma to axon terminal.

Rely on cell body to renew proteins and membrane

Quickly decay if cut or damaged.

Axolemma

neuron cell membrane

Axon terminal

region that secretes neurotransmitters, which are released intro extracellular space

Anterograde

means away from cell body.

ex: mitochondria, cytoskeletal, membrane components, enzymes

Retrograde

toward cell body

ex: organelles to be degraded, signal molecules, viruses, bacterial toxins.

Rabies, polio, herpes, tetanus damage neural tissue by using retrograde exonal transport.

Synaptic transmission

the way neurons communicate to each other.

Electrical-to-chemical-to-electrical transformation

What is the classification of neuron by number of processes?

Multipolar: most abundant, major type in the CNS.

Bipolar: rare, found in special sensory organ

Unipolar: found in the PNS

What is the classification of neurons by the direction of nerve impulse travel relative to CNS?

Sensory

Motor

Interneurons

What is the newest way to classify neuron?

Based on gene expression: transgenic mice; green fluorescent protein

What is the classification of neuron based on neurotransmitter type?

Cholinergic

Serotonergic

Dopaminergic

Name the 4 main neuroglia support CNS neurons?

Astrocytes

Microglial cells

Ependymal cells

Oligodendrocytes

Tell me anything about ASTROCYTES?

Most abundant, versatile, highly branched

guide migration of young neuron, respond to nerve impulse

influence neuronal functioning

What can we say about MICROGLIAL CELLS?

Small, migrate toward injured neurons

Can transform to phagocyte

What do EPENDYMAL CELLS do?

Ciliated to circulate CSF. (cerebrospinal fluid)

they clean up debris in cavities and tissue fluid while we sleep

line the central cavities of the brain and spinal column

What do OLIGODENDROCYTES do?

Branched cells, wrap around CNS nerve fibers insulating forming myelin sheaths

White matter

Region of brain and spinal cord with dense myelinated fibers

Gray matter

Mostly neuron cell bodies and nonmyelinated fibers

What are the 2 major neuroglia in PNS?

Satellite cells

Schwan cells

What do Satellite cells do?

Wrap around cell body in PNS

Function similar to Astrocyte of CNS

What do Schwann cells do?

Forming myelin sheaths in thicker nerve fibers

Similar function with Oligodendrocytes

Vital to regeneration of damaged peripheral nerve fibers.