Nervous System Flashcards
Meninges
Brian and spinal cord and the roots of peripheral nerves are enveloped by a series of connective tissue sheaths:
Dura mater: outermost (attached to skull)
Arachnoid: membrane attached to dura mater
subarachnoid space: contains CSF
pia mater: highly vascular, adherent to brain and spinal cord
Leptomeninges: Arachnoid + Pia Mater
Brain Divisions (embryonic)
Forebrain (telencephalon, diencephalon)
Midbrain (Mesencephalon)
Hindbrain (metencephalon, myelencephalon)
Forbrain
Cerebrum, Basal nuclei, Hippocampus, Amygdala
Thalamus and hypothalamus
Midbrain
Midbrain
Hindbrain
Pons and cerebellum
Medulla oblongata
CNS cells
Astrocytes, Oligodendroglia, Microglial Cells, Ependymal Cells
PNS cells
Schwann Cells
Satellite Cells
White Matter
Formed by dense accumulations of myelinated axons. The myelin sheath is rich in lipids and has a white appearance
Contains myelinated axons and glial cells, blood vessels. Peripheral in spinal cord, central in brain
Grey Matter
Rich in neuronal cell bodies, glial cells, and neuropil. The neuropil represents the axons, dendrites and cytoplasmic projections of glial cells that form the background matrix to neuronal cell bodies within the grey matter
Contains neurons, glial cells, and axons, blood vessels. Peripheral in brain, central in spinal cord
CNS: ectodermal origin
Sensitive to hypoxia: neurons, astrocytes, oligodendrocytes
CNS: Mesodermal origin
Not as sensitive to hypoxia: Microglia, vascular endothelium
Neurons
The functional cells of the nervous system in which two protoplasmic properties are highly developed:
Irritability (generation of an impulse) and
Conductivity (ability to transmit such an impulse from one locality to another
Neurons are dispersed throughout the CNS and grouped in specific areas in PNS
Neurons Structure
Cell body/perikaryon/soma
The cell body of the neuron contains the nucleus and the organelles. The axon and the dendrites branch off the cell body
Neuron Soma Structure
Euchromatic nucleus with prominent nucleolus
Basophilic cytoplasm = Nissl substance: RER and ribosomes
They are long living cells -> aging pigment=lipofuscin
Synapses
Specialized junctions with other cells that are along the length or at the end of an axon
Act as transmission points for electrical impulses
Can trigger the generation of an action potential in the postsynaptic cell; they can be excitatory or inhibitory
Synapses at end of an axon or axon branches are swollen into a club shape (boutons terminaux)
Those along the length of axon result in varicosities (swellings) in the axon (boutons en passant)
Synaptic Knob Structure
Presynaptic part= termination of axon Intersynaptic cleft Postsynaptic part (dendritic thorn)
Synaptic Vesicles
Contain different types of neurotransmitters (Ach, Noradrenaline, and adrenaline, GABA, Dopamine, etc)
Neurons Synapse with:
Neuron
Muscle
Gland
Stimulatory Synsapse
Synaptic vesicles contain ACh
Inhibitory Synapse
Synaptic oval vesicles contain GABA
Oligodendrocytes
Provide support and the myelin sheath to axons within the CNS
Unlike schwann cells (PNS), these can form myelin sheaths for several axons at once (octopus)
Produce and can repair myelin sheath
Small dark nuclei (between myelin sheaths or around neurons)
Can be destroyed by viruses/toxins resulting in primary demyelination
Microglia
Private security system of CNS- CNS is very particular
Functions: Immunosurveillance, Immunoregulation, Reparative (phagocytic), Gitter cells (myelophages)
Derived from blood-borne monocyte
Resident macrophage of CNS
Gitter Cells
Microglial cells that are activated during necrosis or inflammation -> globular and swollen after having phagocytized debris from injured cells
Note the cytoplasmic vacuolation due to ingestion of cellular debris (foamy cytoplasm)
Astrocytes
Star shaped
CNS counterpart of the fibroblast
Involved in cell communication and the functioning of the BBB
2 types: protoplasmic (grey matter) and fibrillar (white matter)
Glial fibrillary acidic protein staining
Astrocytes Functions
Transport of nutrients
Part of BBB
Antigen presentation
Ependymal Cells
Form an epithelium that lines ventricular cavities within the brain and the central canal of the spinal cord
The cells are typically cuboidal or columnar with numerous motile cilia on their apical surfaces
Central canal ependymal cells have cilia to help the circulation of the CSF
Ependymal Cells Function
Important barrier function that protects neural tissue from potentially harmful substances by mechanisms that are still incompletely understood
Have only limited regenerative capacity and this typically do not undergo mitotic proliferation