Nerve Tissue (BMD 310)

The central nervous system (CNS) consists of…

• cerebrum

• cerebellum

• spinal cord

The peripheral nervous system (PNS) consists of…

• cranial nerves

• spinal nerves

• ganglia

Central Nervous System branches out into the…

• Brain

• Spinal Cord

Peripheral Nervous System branches out into the…

• Motor

• Sensory

Motor nervous system branches out into the…

• Autonomic

• Somatic

Autonomic nervous system branches out into the…

• Sympathetic (“fight or flight”)

• Parasympathetic (“rest and digest)

Neurons

the ‘communication’ cells of the nervous system

Glial cells

the support cells

The glial cells of the CNS are…

• Astrocytes

• Microglia

• Oligodendrocytes

• Ependymal cells

***A MOE

The glial cells of the PNS are…

• Schwann cells

• Satellite cells

***SC times 2!

The “Typical Neuron”

be able to identify the various structures that make up a neuron

Neuron Histology

be able to identify the various structures

Synapse

be able to identify the various structures

multipolar neuron

identify

bipolar neuron

identify

unipolar neuron

identify

pyramidal neurons

• very large

• commonly found within the cerebral cortex

• have many large projections and triangular shaped bodies

• most often excitatory

sensory neuron

• transduce sensory input into electrical signal to be carried to brain for perception

• called cutaneous when referring to skin sensation

• afferent - carries information TO the CNS (Arriving to the nervous system)

motor neuron

• carry information to muscle cells to produce movement (skeletal, cardiac, and smooth)

• efferent - carries information AWAY from the CNS (Exiting the nervous system)

interneuron

• serve as connection between motor and sensory within the CNS

• example: reflex arc

excitatory function

• general function potentials

• locally or long range

• neurotransmitters: glutamate, epinephrine, norepinephrine, NO

• depolarize the post-synaptic neuron

• unidirectional or bidirectional information

• example: pyramidal neurons

inhibitory function

• decrease likelihood of action potentials

• localized within small regions

• neurotransmitters: GABA, glycine, serotonin, dopamine

• decrease likelihood of depolarization

• bidirectional information

• example: interneurons

Grey matter

• rich in neuronal cell bodies (soma) and dendrites\

• collections of cell bodies — called a nucleus

• also contains glial cells

• looks grey in color in dissection specimen

White matter

• rich in axons

• also contains glial cells and a few neuronal soma

• looks white in color (from the myelin covering the axons)

  • White matter named in several different ways: fasciculus, funiculus, lemniscus, peduncle, tract

nuclei

collections of grey matter within the CNS

ganglia

collections of grey matter within the PNS

microglia

• immune cells

  • respond to injury or disease

  • secrete and respond to many different cytokines and chemokines

  • recruit immune cells from the periphery into the CNS if needed

• Morphology

  • variable

  • small cell body with many processes that are scanning the environment

astrocytes

• support (physical, chemical, and metabolic)

• maintain the blood brain barrier (BBB)

• secrete and absorb neurotransmitters in the synaptic cleft

• store glycogen, providing glucose and lactate to neurons

• regulate the internal CNS environment, especially fluid surrounding axons and synapses, by controlling ion concentrations in the extracellular space

glioma

• upwards of 80% of brain tumors are gliomas

• tumor arising from glial tissue

  • typically, astrocytic or oligodendrocytic

• graded on severity I-IV (1-4)

  • glioblastoma is a grade IV malignant glioma

Oligodendrocytes

• myelinating cell of the CNS

• myelin electrically insulates an axon, increasing transmission speed

• one oligodendrocyte will wrap around several axons

ependymal cells

• line the ventricles and the central canal of the spinal cord

• act a bit like epithelium in the CNS, but lack a basement membrane

• Ependymal cells in the choroid plexus secrete cerebrospinal fluid

Schwann Cells

myelinating cell of the PNS

Satellite Cells

accessory cells in PNS ganglia, similar to astrocytes in the CNS

Axon Regeneration

• CNS

  • Inhibitors produced and found within the CNS prevent regeneration

    • Myelin-associated inhibitors from oligodendrocytes

    • CSPGs from astrocytes

• PNS

  • Schwann cells promote regeneration through a variety of molecules