Central nervous system: Histology

Summary

This script explores the central nervous system (CNS), highlighting its key components: the cerebrum, cerebellum, brainstem, and spinal cord. It delves into the roles of neurons and neuroglia, emphasizing their functions in the nervous system. The script contrasts the CNS's white and gray matter, explaining their composition and appearance. It also discusses the meninges, cerebrospinal fluid, and various cell types, including astrocytes and microglia, detailing their unique characteristics and roles. The video provides a comprehensive look at the CNS's structure and function, crucial for understanding neurological processes.

Takeaways

• 🧠 The central nervous system (CNS) comprises the cerebellum, cerebrum, brainstem, and spinal cord.
• 🌐 Neurons are the fundamental working units of the nervous system, while neuroglia or glial cells provide support and protection.
• 🧬 Central neuroglia includes astrocytes, oligodendrocytes, endothelial cells, and microglia, whereas peripheral neuroglia includes Schwann cells, satellite cells, and other organ-associated cells.
• 🔍 The CNS is macroscopically divided into white matter, rich in myelinated axons, and gray matter, primarily composed of neuron cell bodies and dendrites.
• 👀 In the spinal cord, white matter is peripheral, and gray matter is central, creating an H or butterfly shape in cross-section.
• 🛡️ The meninges are connective tissue layers that envelop the CNS, with the dura mater being the thickest and outermost layer.
• 💧 The brain's ventricles and the spinal cord's central canal are filled with cerebrospinal fluid (CSF), produced by ependymal cells.
• 🔬 Astrocytes are the most abundant glial cells in the CNS, with processes that help form the blood-brain barrier and produce glial fibrillary acidic protein (GFAP).
• 🔍 Microglia are the immune cells of the CNS, capable of moving and migrating to remove damaged tissue and participate in immune responses.
• 🧠 Pyramidal cells are prominent in the cerebral cortex, integrating sensory information and initiating motor responses, characterized by a large cell body and a single axon.
• ⚖️ The cerebellar cortex has three layers: the white matter, the granular layer, and the molecular layer, with Purkinje cells situated between the molecular and granular layers.

Q & A

What are the main components of the central nervous system (CNS)?

The central nervous system (CNS) consists of the cerebellum, cerebrum, brainstem, and spinal cord.

What is the basic working unit of the nervous system?

The neuron is the basic working unit of the nervous system.

What role do neuroglia or glial cells play in the nervous system?

Neuroglia or glial cells are non-neuronal cells that support and protect the nervous system.

What are the differences between white matter and gray matter in the CNS?

White matter is composed of lipid-rich myelin sheaths covering axons, while gray matter consists mostly of neuron cell bodies, dendrites, astrocytes, and microglia.

How is the spinal cord's arrangement of white and gray matter different from the brain?

In the spinal cord, white matter is mainly in the periphery, and gray matter is closer to the center, forming an H or butterfly-shaped appearance in cross-section, which is the opposite arrangement found in the brain.

What is the function of the meninges in the CNS?

The meninges are layers of connective tissue that cover and protect the CNS, with the dura mater being the thickest and outermost layer.

What is cerebrospinal fluid (CSF) and what is its function?

Cerebrospinal fluid (CSF) is a clear fluid that fills the ventricles of the brain and the central canal of the spinal cord, providing cushioning and support to the CNS.

What are the characteristics of astrocytes and how do they contribute to the blood-brain barrier?

Astrocytes are star-shaped glial cells with long processes that surround capillaries, helping to maintain the blood-brain barrier by inducing and maintaining tight junctions between endothelial cells.

How do oligodendrocytes contribute to the CNS?

Oligodendrocytes are glial cells that wrap around axons to form myelin sheaths within the CNS, aiding in the speed of nerve impulse conduction.

What is the role of microglia in the CNS?

Microglia are the immune cells of the CNS, responsible for finding and removing damaged tissue and participating in the CNS immune response.

What are the characteristics of pyramidal cells and their role in the cerebral cortex?

Pyramidal cells are prominent neurons in the cerebral cortex with a large, pyramid-shaped cell body and a branching dendritic system. They integrate sensory information and initiate voluntary motor responses.

How does the cerebellum's cortex differ in structure from the cerebral cortex?

The cerebellum's cortex has a distinct three-layered structure with the molecular layer, a single layer of Purkinje cells, and the granular layer, which is different from the six-layered structure of the cerebral cortex.

Outlines

00:00

🧠 Central Nervous System Structure and Function

The Central Nervous System (CNS) is composed of the cerebellum, cerebrum, brainstem, and spinal cord. Neurons are the fundamental units of the nervous system, while neuroglia or glial cells provide support and protection. Glial cells are categorized into central neuroglia, which include astrocytes, oligodendrocytes, endal cells, and microglia, and peripheral neuroglia, which include Schwann cells, satellite cells, and others. The CNS is macroscopically divided into white and gray matter, with the former containing lipid-rich myelin sheaths and the latter primarily composed of neuron cell bodies and dendrites. The cerebrum and cerebellum have gray matter on the outermost layer, while the spinal cord has white matter peripherally and gray matter centrally, forming an H or butterfly shape in cross-section. The CNS is covered by meninges, with the dura mater being the thickest and outermost layer. The ventricles of the brain and the central canal of the spinal cord are filled with cerebrospinal fluid (CSF), produced by ependymal cells. Astrocytes are the most abundant glial cells in the CNS, with processes that extend in all directions, including foot processes that form part of the blood-brain barrier. They also produce glial fibrillary acidic proteins (GFAP), which can be used as a marker for immunostaining.

05:02

🔬 Microglia and Neurons in the CNS

Microglia are small antigen-presenting cells in the CNS, found in both white and gray matter, and are unique among glial cells for their ability to migrate to different parts of the CNS. They play a crucial role in finding and removing damaged tissue and are part of the CNS immune response. They can be visualized more easily using immunostaining techniques. Immunocytochemistry is a method where cells are immunostained after being isolated and suspended in liquid. Pyramidal cells are the most prominent neurons in the cerebral cortex, integrating sensory information and initiating voluntary motor responses. They are characterized by their large, pyramid-shaped cell bodies with an apex pointing towards the cortical surface. The cerebellum's cortex has three layers: the innermost white matter, the middle granular layer, and the outer molecular layer. Immunostaining can be used to clearly visualize Purkinje cells, which have large cell bodies, highly branched dendritic systems extending into the molecular layer, and axons extending through the granular layer.

Keywords

💡Central Nervous System (CNS)

The Central Nervous System (CNS) is the core of the nervous system, consisting of the cerebrum, cerebellum, brainstem, and spinal cord. It plays a crucial role in receiving, processing, and transmitting information throughout the body. In the video, the CNS is described as being composed of both white and gray matter, with the former being lipid-rich and the latter primarily consisting of neuron cell bodies and dendrites.

💡Neuron

Neurons are the fundamental working units of the nervous system, responsible for transmitting information through electrical and chemical signals. They are essential for the CNS's function, as they form complex networks that allow for communication within the brain and spinal cord. The video script mentions that neurons have cell bodies, dendrites, and axons, with the latter being surrounded by myelin sheaths in white matter.

💡Neuroglia or Glial Cells

Glial cells, also known as neuroglia, are non-neuronal cells that provide support and protection to the nervous system. They play various roles, including maintaining homeostasis, providing structural support, and guiding the development and function of neurons. The video script distinguishes between central neuroglia, which includes astrocytes, oligodendrocytes, endothelial cells, and microglia, and peripheral neuroglia, which includes Schwann cells, satellite cells, and other organ-associated cells.

💡White Matter

White matter in the CNS is composed mainly of myelinated axons, which give it a whitish appearance due to the lipid-rich myelin sheaths. These sheaths facilitate the rapid transmission of nerve impulses. The video explains that white matter is primarily found in the periphery of the spinal cord and in deeper regions of the brain, contrasting with the gray matter.

💡Gray Matter

Gray matter is made up predominantly of neuron cell bodies, dendrites, astrocytes, and microglia. It appears grayish due to the absence of myelin sheaths and is mainly located in the central areas of the spinal cord and the outermost parts of the cerebrum and cerebellum. The video script describes how gray matter contrasts with white matter in terms of both appearance and composition.

💡Meninges

The meninges are layers of connective tissue that envelop and protect the CNS. They include the dura mater, arachnoid mater, and pia mater. The video script specifically mentions the dura mater as the thickest and outermost layer, which is visible in the provided images. The meninges serve to cushion the CNS and protect it from physical damage.

💡Cerebrospinal Fluid (CSF)

Cerebrospinal fluid is a clear fluid that circulates within the ventricles of the brain and the central canal of the spinal cord. It provides cushioning and buoyancy to the brain and spinal cord, helping to protect them from mechanical shock. The video script describes the production of CSF by ependymal cells lining the ventricles and central canal, and its circulation facilitated by cilia and microvilli of these cells.

💡Astrocytes

Astrocytes are star-shaped glial cells that are the most abundant in the CNS. They play a role in maintaining the blood-brain barrier, providing structural support, and regulating the extracellular environment. The video script highlights astrocytes' role in inducing tight junctions between endothelial cells and their production of glial fibrillary acidic protein (GFAP), which can be visualized through specific staining techniques.

💡Microglia

Microglia are the immune cells of the CNS, acting as antigen-presenting cells and participating in the immune response. They are unique among glial cells in their ability to migrate and actively move, which aids in their function of identifying and removing damaged tissue. The video script notes that microglia can be visualized using immunostaining techniques, which is crucial for studying their role in the CNS.

💡Pyramidal Cells

Pyramidal cells are a type of neuron found in the cerebral cortex, characterized by their pyramid-shaped cell bodies with an apex pointing towards the cortical surface. They integrate sensory information and initiate voluntary motor responses. The video script describes how these cells have a large branching dendrite extending toward the cortical surface and an axon that synapses with other cells in the cortex or white matter.

💡Cerebellum

The cerebellum is a region of the brain that plays a key role in motor control, coordination, and balance. It has a distinct layered structure with the cortex composed of gray matter and underlying white matter. The video script discusses the cerebellum's histological features, including the presence of Purkinje cells, which are a type of neuron unique to this region.

Highlights

The central nervous system (CNS) comprises the cerebellum, cerebrum, brainstem, and spinal cord.

Neurons are the fundamental working units of the nervous system.

Neuroglia or glial cells provide support and protection to the nervous system.

Central neuroglia includes astrocytes, oligodendrocytes, endothelial cells, and microglia.

Peripheral neuroglia includes Schwann cells, satellite cells, and organ-associated cells.

The CNS is composed of white matter and gray matter, differentiated by the presence of myelin sheaths.

White matter contains axons with myelin sheaths, while gray matter is rich in neuron cell bodies and dendrites.

The cerebrum and cerebellum have gray matter on the outermost part with white matter in deeper regions.

The spinal cord has white matter in the periphery and gray matter closer to the center, forming an H or butterfly shape in cross-section.

The spinal cord's dorsal horns contain sensory neurons, and the anterior horns contain upper motor neurons.

The CNS is covered by meninges, with the dura mater being the thickest and outermost layer.

Ventricles of the brain and the central canal of the spinal cord are filled with cerebrospinal fluid (CSF).

Ependymal cells line the ventricles and central canal and are responsible for producing CSF.

Astrocytes are the most abundant type of glial cell in the CNS and play a role in the blood-brain barrier.

Oligodendrocytes can be identified by their small, round, and condensed nuclei and are responsible for myelin sheath formation in the CNS.

Microglia are the immune cells of the CNS, capable of migrating to different parts to remove damaged tissue.

Immunocytochemistry is a technique used to visualize cells, such as microglia, after they have been isolated.

Pyramidal cells are prominent in the cerebral cortex, integrating sensory information and initiating motor responses.

The cerebellar cortex has three layers: white matter, granular layer, and molecular layer.

Purkinje cells are a single layer of neurons between the molecular and granular layers in the cerebellar cortex.

Transcripts

the central nervous system or CNS

consists of the cerebellum cerebrum

brain stem and spinal cord the neuron is

the basic working unit of the nervous

system and the neuroglia or gal cells

are the non- neuronal cells that support

and protect the nervous system the

central neurog Gia includes asites

oligodendrocytes endal cells and microa

the peripheral neuroglia includes Schwan

cells satellite cells and a number of

cells associated with specific

organs macroscopically the CNS is made

of white matter and gray matter the

difference in appearance is from the

lipid Rich myelin sheaths that cover the

axons present in white matter whereas

the gray matter consists mostly of

neuron cell bodies dendrites asites and

microgo

cells in this high power image of white

matter from the SP final cord the axons

are surrounded by clear white space

which is where the myin was present

before the tissue was processed to

create the slide the outermost portion

of the cerebrum and cerebellum consists

of gray matter with their white matter

present mainly in the deeper regions of

the brain on the other hand the spinal

cord has the opposite arrangement with

white matter mainly in the periphery and

gray matter mostly located closer to the

center forming an H or butterfly shaped

appearance when looking at a

cross-section of the spinal spal

cord in this low power image we can see

the spinal cords two posterior or dorsal

horns closer to the top of the image and

two anterior or ventral horns at the

bottom the dorsal horns contain mostly

Sensory neurons and the anterior horns

contain mostly upper motor neurons a

simple way of remembering the location

of the motor neurons is to remember that

most cars also have their Motors in the

front or anterior part of the car the

entire CNS is also covered by layers of

connective tissue called the meninges

the portion of the meninges that can be

seen in this low power image is the

duramater which is the thickest and

outermost layer of the

meninges the ventricles of the brain and

the central Canal of the spinal cord are

filled with cerebral spinal fluid or CSF

and have a lining of cuboidal or

columnar cells called a anal cells these

cells are responsible for producing

CSF if we take a closer look at the

cells we can also faintly see that the

endal cells can have cyia which helps

circulate the CSF within the central

Canal the endal cells can also have

microvilli but they're typically too

small to be seen with light

microscopy now let's take a closer look

at the border between the spinal cords

white matter and gray matter on the left

is the white matter where we can

identify many any of the purple stained

axons by the myin sheaths that leave a

white space that surrounds each

axon on the right of this image is the

gray

matter although neuron cell bodies can

vary a lot in overall appearance they're

still usually recognizable by their

prominent nuclei with distinct

nucleoli they're also usually much

larger than gleo cells the different

gleo cells can be difficult to identify

and differentiate from each other when

using an h& stain except for

oligodendrocytes oligodendrocytes can be

identified by their small round and

condensed nuclei their cell bodies

aren't easily seen because their

cytoplasm is unstained since it contains

a lot of GGI complexes which don't

absorb the stain oligodendrocytes have

many processes that extend and wrap

around axons to form the myin sheath for

axons within the CNS the peripheral

nervous systems myin sheaths are

produced by Schwan cells instead

the gray matter surrounding all the

cells is called the neuropil which

consists of a dense network of fibrous

cellular branches or processes from gal

cells and

neurons in the CNS the star-shaped

asites are the most abundant type of gal

cell they have many long processes that

extend in all directions from their cell

body many of the processes have enlarged

terminal ends called foot processes

which surround capillaries as part of

the bloodb brain barrier the foot

processes help induce and maintain the

formation of tight junctions between

endothelial cells asites also produce

structural proteins called gleo

fibrillary acid proteins or gaps these

proteins can be used as a unique marker

for immunostaining to help visualize

asites in tissue samples in this high

power image the gfap specific staining

makes it easier to see the asites in

brown as well as the foot processing

that surround capillaries as we can see

them near the top of this

image microglia are small antigen

presenting cells of the CNS that are

found in both white and gray matter they

have short branching processes that

actively move and are the only gal cells

that also migrate to different parts of

the CNS which helps them find and remove

damaged tissue as well as function as

part of the CNS immune

response similar to asites microglia can

be visualized more easily using

techniques like amuno staining

immunocytochemistry is a form of

immunostaining where the cells are

immunostained after they've been

isolated and suspended in liquid which

is why the microa in this image are the

only cells present and they're also

spaced out relatively

evenly the paramal cells are the most

prominent neuron in the cerebral

cortex these eant neurons integrate

sensory information and initiate

voluntary motor responses

they get their name from their large

pyramid-shaped cell bodies that have an

apex that points towards the cortical

surface of the CeX at the top of this

image at the Apex there's a large

branching dendrite that extends up

toward the cortical surface the sides of

the cell have much smaller dendrites

that Branch out to the sides and its

single axon extends from the base of the

cell to synapse with other cells in the

cortex or even deeper into the white

matter together the direction of the

axon and the large dendrite give paramal

cells their appearance of being

vertically arranged within the cerebral

cortex moving to the cerebellum at low

power the cortex has three layers seen

with an h& stain the innermost layer

that stained dark pink is the white

matter the purple middle layer and outer

light pink layer are both a part of the

gray matter the outer layer is the

molecular layer and the dark purple

layer is the granular layer if we zoom

in closer to the border of these two

layers we can see that it actually has

three layers because of a single layer

of neurons called pereni cells that sit

between the upper molecular layer and

lower granular layer immunostaining was

performed on this section of tissue in

order to see the pingi cells more

clearly by staining them dark brown

these neurons have very large cell

bodies with a highly branched dendritic

system that extends into the molecular

layer and an axon that extends down

through the granular layer which is

often hard to to see even with

immunostaining helping current and

future clinicians Focus learn retain and

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