Untitled Quiz

Central Nervous System Histology

• The central nervous system (CNS) includes the brain and spinal cord.
• The brain and spinal cord are composed of gray matter and white matter.
• Gray matter contains nerve cell bodies, glial cells (excluding fibrous astrocytes), and blood cells.
• White matter contains myelinated axons, glial cells (excluding protoplasmic astrocytes), and blood vessels.
• The ventricles or central canal are also part of the CNS.

Brain

• The brain surface has protrusions called gyri and indentations called sulci.
• The brain is protected by membranes called meninges.
• The meninges consist of three membranes: dura mater, arachnoid mater, and pia mater.
• The dura mater is closely attached to the skull.
• The arachnoid mater is between the dura mater and pia mater.
• The subarachnoid space is between the arachnoid mater and pia mater.
• The pia mater is the innermost layer attached to the brain.
• The dura has two layers.
• The brain has gray matter and white matter.

Spinal Cord

• The spinal cord has gray matter and white matter.
  • Gray matter is centrally located and shaped like a butterfly.
  • White matter surrounds the gray matter.
• The spinal cord has a central canal filled with cerebrospinal fluid.
• The central canal is lined by ependymal cells.
• It contains afferent fibres (myelinated and unmyelinated) and efferent fibres (myelinated and unmyelinated), intermediate fibres (myelinated and unmyelinated) and neuroglial cells.
• The outer white matter contains bundles of axons that carry sensory and motor information.

Cerebellum

• The cerebellum is part of the CNS.
• The cerebellum has a cortex composed of three layers, the molecular layer, the Purkinje cell layer and the granular layer.
• The cerebellum has white matter.
• Different cell types found in different layers make up the cerebellum cortex.
• The cerebellum has a white matter core containing nerve fibers.

CNS in Microscopes

• Nerve cell bodies are in the gray matter.
• Microglia are also found in the different parts of the CNS -Astrocytes, oligodendrocytes, and microglia.

Blood-CSF Barrier

• Capillary endothelium of the choroid plexus, basement membrane of capillaries, and ependymal cells make up the blood-CSF barrier.

Blood-Brain Barrier

• The blood-brain barrier is formed by the capillaries in the CNS.
• The capillaries in the CNS consist of flat endothelial cells surrounded by a basement membrane.
• The endothelium is thin, continuous, and not fenestrated.
• Tight junctions are present between the endothelial cells.
• The perivascular feet of astrocytes extend to the basement membrane.

Cerebrospinal Fluid (CSF)

• CSF is found in the subarachnoid space.
• CSF helps protect the CNS from mechanical and gravitational effects.
• CSF distributes pressure equally throughout the brain to minimize tissue damage from impact.
• CSF flows from the lateral ventricles through the interventricular foramina into the third ventricle.
• Then CSF flows down the cerebral aqueduct to the fourth ventricle.
• CSF flows out of the lateral and median apertures.
• CSF is reabsorbed into the dural venous sinuses via arachnoid villi.

Ependymal Cells

• Ependymal cells are a type of glial cell that lines the ventricles and central canal of the spinal cord.
• They have a simple cuboidal to columnar shape.
• The cytoplasm is rich in mitochondria which makes it suitable for water transport.
• They have microvilli which increases the surface area.
• CSF is secreted through these cells.
• They have basal folds.

Neuronal Cells In Cortex

• Pyramidal neurons are the most prominent neurons in the cerebral cortex.
• They have a pyramid-shaped cell body.
• Their apical dendrites extend upward and outward.
• Their axons extend deep into the white matter and also re-enter the cortex.
• They are categorized according to their diameter (small, medium, large)
• The largest are Betz cells in the inner pyramidal layer.
• Other neurons in the cortex include granular neurons, fusiform neurons, and horizontal cells.
• Granular neurons are small, star-shaped, with many synapses with other neurons.
• Fusiform neurons are modified stellate neurons.
• They are usually found in the deepest layer of the cortex.
• Horizontal cells are located superficially, lying horizontally, and are fusiform.
• Martinotti neurons are small multipolar neurons that synapse with pyramidal neurons.

Cerebral Cortex

• Divided into six layers of neurons with unique morphologies.
• Different neurons are found in different layers.
• The layers are parallel to the brain surface. - The layers have various thicknesses and cell numbers.
• Layers I - VI have unique cell and nerve fibre morphology.
• Layers 1-3 are primarily involved in receiving signals , Layers 4-6 are involved in the sending of signals.
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Cerebellar Cortex

• The cerebellar cortex is made up of three layers- the molecular, Purkinje, and granular layer.
• The molecular layer contains stellate cells and basket cells.
• Purkinje cells are large flask-shaped structures.
• The granular layer contains small granule cells, Golgi cells, and neuroglial cells.

White Matter of Spinal Cord

• The outer part of the spinal cord contains white matter.
• White matter consists of bundles of myelinated and unmyelinated axons.
• These axons carry specific functions like sensory and motor information.

Gray Matter of Spinal Cord

• The inner part of the spinal cord contains gray matter.
• It has a butterfly-like shape.
• The anterior horn contains multipolar neurons with large polygonal nuclei.
• Dendrites and perikarya have Nissl bodies which contains rough endoplasmic reticulum and polysomes.

Spinal Cord

• The spinal cord has a central canal which is lined with ependymal cells.
• The spinal cord has a central canal with cerebrospinal fluid .
• The spinal cord has dorsal and ventral horns.