Nervous System - Microanatomy (block 4)

Meninges

- a series of CT sheaths that envelop the brain, spinal cord, roots of peripheral nerves, and optic nerve (considered CNS tissue)

The layers of the meninges

- dura mater

- arachnoid

- pia mater

- leptomeninges

- subarachnoid space

dura mater

outermost layer (in contact with the bones)

arachnoid

membrane attached to dura mater

pia mater

highly vascular, adherent to brain and spinal cord

leptomeninges

arachnoid + pia mater

subarachnoid space

contains CSF

When does the nervous system first make an appearance in the embryonic stage?

becomes evident at the embryonic disk stage as an elongated thickening (neural plate)

neural plate

consists of neuroectoderm and becomes the neural tube

neural tube gives rise to

- all cells in CNS

- all nerves that innervate skeletal muscle

Neural crest cells

cells along the lateral border of the neural plate that undergo differentiation

neural crest cells give rise to:

- arachnoid and pia mater

- enteric parasympathetic ganglia

- schwann cells

- dorsal root ganglia

mesoderm layer gives rise to ?

- dura mater

- CT around peripheral nerves

embryonic brain division: forebrain

- telencephalon

- diencephalon

embryonic brain division: mid brain

mesencephalon

embryonic brain division: hindbrain

- metencephalon

- myelencephalon

telencephalon major derivative

cerebral cortex

metencephalon major derivative

cerebellum and pons

myelencephalon major derivitive

medulla oblongata, spinal cord

cerebrum

- largest portion of the brain

- contain: sulcus, gyrus, and fissures

sulcus

groove of cerebral hemisphere

gyrus

ridge on the cerebral hemisphere

fissure

a deep cleft or groove on the surface of the cerebral cortex separating major regions, lobes, or hemispheres

cerebellum

contains the vermis and folia

vermia

narrow midline region

folia

narrow, parallel, leaf like folds on the surface of the cerebellar cortex

How can the spine be functionally divided?

1. C1-C5

2. C6-T2

3. T3-L3

4. L4-S1

5. S1-S3

#1

central canal

#4

ventral median fissure

#5

dorsal horn

#6

ventral horn

#7

dorsal funiculus

#8

lateral funiculus

#9

ventral funiculus

cells of ectodermal origin

- neurons

- astrocytes

- oligodendrocytes

what are cells of ectodermal origin very sensitive to?

hypoxia: a decrease in O2

cells of mesodermal origin

- microglia

- vascular endothelium

neurons

- part of CNS

- responsible for transmitting electrical signals throughout the body

glial cells

- part of the CNS

- neuroglia

- support system in which neurons are embedded and serve many critical functions

- astrocytes, oligodendrocytes, ependymal cells, and microglia

anatomy of a neuron

- perikaryon / soma: contains the nucleus and the organelles

- axon and dendrites branch off the cell body

What two properties are developed from neurons?

irritability and conductivity

neuron nucleus

euchromatic (dispersed, active DNA) nucleus with prominent nucleolus

neuron cytoplasm

basophilic cytoplasm = nissl substance

- RER and ribosomes

what is a synapse ?

synapse is the small, specialized junction or gap where a neuron communicates with another cell

Neurons are long living cells, what type of pigment is present because of this?

Lipofuscin - "wear and tear"

groups of neurons in the CNS vs. PNS

CNS: groups of neurons are nuclei

PNS: groups of neurons re ganglia

types of glial cells in the CNS

- oligodendrocytes

- microglia

- astrocytes

- ependymal cells

Oligodendrocytes

- provide support to neurons

- for myelin sheaths for SEVERAL axons at once

- "octopus" shape

Oligodendrocytes - microscopic appearance

- small dark nuclei

- can be visualized with silver stains, OTAN, and IHC stains

Microglia

- resident macrophage of CNS

- immunosurveillance (includes antigen presentation)

- immunoregulation

- phagocytic function during inflammation and repair

Glitter cells

microglial cells activated during conditions causing inflammation of cell death secondary to permanent cell damage (necrosis )

Astrocytes

- CNS counterpart of the fibroblast

- two types: protoplasmic (grey matter) and fibrillar (white matter)

- visualized with IHC stain that reacts with GFAP

glial fibrillary acidic protein

- GFAP

- a protein made in abundance by astrocytes

astrocyte functions

- cell communication

- crucial component of the blood brain barrier

- transport of nutrients

- antigen presentation

white matter

- made up of dense accumulations of myelinated axons along with other glial cells

- no neuronal cell bodies reside here

- myelin surrounding axons are rich in lipids and has a white appearance in HE stained tissues

Grey matter

- neuronal cell bodies along with the glial cells

- the neurophil represents the axons, dendrites, and cytoplasmic projections of glial cells that form the background matrix to neuronal cell bodies within the grey matter

white matter contains:

- myelinated axons

- glial cells

- blood vessels

grey matter contains:

- neuron cell bodies and processes (axons, dendrites)

- glial cells

- blood vessels

White matter is peripheral in ____, central in the ____

spinal cord; brain

Grey matter is peripheral in ____, central in the ____

brain; spinal cord

silver stains

- allow for more detailed visualization of oligodendrocytes

- stain them black

OTAN stain

stains normal myelin brown-organge and damaged myelin black

IHC (immunohistochemical) stain

to detect Olig2