What are the main types of nervous tissue cells?
- Glial Cells
Glial cells are split into:
- satellite Cells
- Schwann Cells
- Ependymal Cells
Whats the difference between neurons and glial cells?
Neurons are excitable and carry action potentials.
Glial cells are supportive and non-excitable, they have other functions
How do neurons divide?
Can neurons grow back?
If you cut the axon it can grow back
But if you crush the cell body in the spine or ganglia then its permanent
Whats the function of myelin?
Reduces loss of electrical signals as they pass down the axon, so they can travel further faster. (Also known as saltatory conduction)
What do we call the spaces between myelin sheaths?
Nodes of Ranvier
What forms the myelin sheath?
Schwann cells in the PNS
Oligodendrocytes in the CNS
How do schwann cells produce a myelin sheath?
They wrap around the axon and extrude their cytoplasm.
So the cell membrane becomes the myelin sheath
What are the different types of neurons?
- Motor neurons
- Lots of dendrites
- Olfactory or retinal nerve fibres
- One dendrite
- Sensory Neurons
- Cell body sits off to the side of the axon
Neurons are organised into different types/locations e.g. white vs gray matter or ganglia vs nuclei. What are they?
Myelinated axons are referred to as white matter when diffuse.
Or Tracts when bundled together by modality
Neuronal Cells bodies localised within the CNS are called nuclei, within the PNS they’re called Ganglia
Diffuse Cell bodies or non-myelinated axons are known as grey matter
Divide Glial cells by PNS vs CNS:
- Satellite Cells
- Schwann Cells
- Ependymal cells
What do satellite cells do?
surround neuronal cell bodies in the PNS
What do Ependymal cells do?
Type of Glial cell that line ventricles in the brain
What do microglia do?
Type of glial cell in the CNS that phagocytose and form scar tissue
What do astrocytes do?
Glial cells in the CNS that surround synapes and capillaries to buffer ions.
They contribute to the BBB
How do the ventricles of the brain develop?
- Neural tube above 4th somite develops into 3 primary vesicles
- From there into 5 secondary vesicles
Telencephalon & Diencephalon
Myelencephalon & Metencephalon
- These 5 vesicles form the ventricles
Which cavity forms which ventricle?
Telencephalon (part of forebrain) –> Lateral ventricles in cerebral hemispheres
Diencephalon (part of forebrain) contains 3rd ventricle
Mesencephalon (Midbrain) –> Cerebral Aqueduct
The two division of the rhombencephalon form the 4th ventricle
Whats contained in the ventricles?
Lined by ependymal cells
Filled with CSF
List the folds of the dura mater?
Attaches to Crista Galli & dips between cerebral hemispheres
Seperates cerebellum form occipital lobes
What layer of meninges contains CSF?
The subarachnoid space
Where is CSF produced/absorped?
Produced in the choroid plexus of the ventricles
Its absorbed by arachnoid villa
List the layers of the head
Scalp - Skin - Connective Tissue - Aponeurosis - Loose Connective Tissue - Pericranium Cranium Meninges - Dura - Arachnoid - CSF - Pia
What does the blood brain barrier do?
Maintains a stable homeostatic environment for the brain, preventing harmful amino acids/ions/blood cells from reaching the brain
What makes up the blood brain barrier?
Thick Basal Lamina
Foot Processes of the Astrocytes
Where are the different fold of dura mater?
Falx Cerebri is a verticle fold between the cerebral hemispheres
Diaphragma Sellae lines the Sella Turcica, wrapping around the pituitary gland
Tentorium Cerebelli is a horizontal fold dividing the cerebellum and cerebrum
Falx Cerebelli between cerebellar hemispheres