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Nervous system cells Chapter4 (Regional anatomy of CNS (Spinal cord…
Nervous system cells
Chapter4
Cellular components
Neurons
Neuroblastoma or retinoblastoma
Soma, dendrite, axon
Axonal transport
Has motor protein kinesin
Dynein for axonal transport
Anterograde
Retrograde
Virus like chickenpox
Travel by axonal transport
Neuroglia
Can form meningiomas
Astrocytes
Regulate microenvironment
Isolate synaptic endings from adjacent
Contact cappilaries in paimater
Provide mechanical support
Transform to reactive astrocytes on injury
Slw growing tumor astrocytoma
Fast one is glioblastoma multiforme
Oligodendrocytes
Like Schwann cells
Surround axons with myelin
Myelin increases speed of actionpotential conductance
ODC helps myelinate multiples axons in cns while schwann cells only 1 in pns
Cns has unmyelinated axons but pns does not
Form oligodendroglioma schwannoma
Microglia
Derived from erythromyeloid stem cells which migrate early into CNS
Phagocytose damaged cells
Pruning excess synapses formed during early development
Ependymal cells
Form epithelium lining ventricular spaces of brain
Ependymal cells of choroid plexus secrete csf
Ependymoma
IN CNS:-
IN PNS:- Schwann cells
Satellite cells
Satellite cells encapsulate dorsal root and CN ganglion cells and regulate microenvironment
Peripheral nervous system
Takes sensory info to CNS
Take motor commands to body
Sensory pathway
Motor pathway
Autonomic motor pathway
CENTRAL NERVOUS SYSTEM
Axons pathways called white matter coz myelin refraction
Regions of neurons and dendrites called grey matter
Axons travel with tracts nd if have specific function called pathway
Grey matter
Nucleus in cns
Thalamic cerebellar and cranial nerve nuclei
Ganglion in pns
Regional anatomy of CNS
Spinal cord
Sensory input, reflex circuits, somatic and autonomic motor output
Medulla
CN 8 to 12 cvs and respi control auditory nd vestibular input brainstem reflexes
Pons
CN 5 to 8 respi urinary control control of eye movement facial sensation motor control
Cerebellum
CN 8 motor coordination motor learning equilibrium
Midbrain
CN 3 nd 4 acoustic relay control of eye including movement lens and pupillary reflexes and pain modulation
Thalamus
CN 2 sensory and motor relay to cortex regulation of cortical activation visual input
Hypothalamus
Autonomic and endocrine control motivated behaviour
Basal ganglia
Shape patterns of thalamocortival motor inhibition
Cortex
CN 1 sensory perception cognition learning and memory motor planing and voluntary movement language
CSF
30ml in ventricles
125 ml in arachnoid space
filtrate of capillary blood formed from choroid plexus
Escapes thru ventricular system by 2 foramen in 4th ventricle
Foramen of magendie and laterally foramen of luschka
Where csf space is expanded known as cisterns like lumbar cistern which is site of lumbar puncture
Has high Na and Cl than blood
Pressure 120 to 180mm in recumbant position
BLOOD BRAIN BARRIER
Large molecule movement into brain restricted
Due to tight junctions
Astrocytes also take up excess K+
Radiologist use this barrier to see if substance introduced penetrate it indicating tumor
INJURY
When ribosomes appear disorganized and nissls bodies are weakly stained by aniline dyes means there is nerve injury and discontinuity. Chromatolysis occurs.
Nucleus eccentric. New axon from cell body develop projections and form connection with dendrites
In cns myelin sheath also phagocytosed. In pns schwann cells that form myelin sheath remain viable and undergo cell division. Known as wallerian degeneration.
If the axons who supplys the dependent muscle or tissue or neuron are interrupted
Postsynaptic cell undergo degeneration. For eg muscle atrophy in motor neuron disease.
Regeneration may occur if sprouts from axons develop and reinnervate original target schwann cell remyelinate the axon.
In cns reinnervation might be difficult since oligodendrocyte might interfere as it supplies many myelin sheaths not in pns where there is one