Organisation of peripheral nervous system Flashcards
What comprises the CNS?
Brain + spinal cord
What comprises the PNS?
Axons, ganglia and supporting cells
What comprises neural tissue?
Neurons + supporting cells
Describe neurons
Highly differentiated cells with almost no capacity for cell division + limited capacity for repair after injury.
Vary in length from a few mm to over a metre
Neuroglial cells
Non-nervous cells within the CNS;
Astrocytes (maintains blood-brain barrier)
Oligodendrocytes (supports axons, myelination)
Microglia (macrophages of CNS)
Ependymal cells (lines ventricles of brain)
Astrocytes
Maintains blood-brain barrier
Contains microfilaments which provide structural strength for the CNS
Stabilises structure after injury - produces scar tissue
Directs neural growth during development
Controls the interstitial environment; recycles neurotransmitters
Microglia
Macrophages of brain, make up 5% of neural tissue but this can increase during infections.
Has 5 branches
Ependymal cells
Lines the chambers and passageways of the CNS, which are filled with cerebrospinal fluid.
Has processes that make contact with glial cells, monitors the CSF and makes contact with other cells to regulate it.
Oligodendrocytes
Myelinates axons; wraps axons together in a bundle
Neuroglia
Support cells; satellite cells + Schwann cells
Satellite cells
Surrounds neuron cell body in ganglia
Schwann cells
Myelinates peripheral axon + helps with repair after injury
How does the neuroglia work in PNS
Satellite cells support the cell body, while the Schwann cells support the axons (either by myelination, or by bundling)
Ganglia
Group of nerve cell bodies which lie outside the CNS
What are the meninges layers?
Dura
Arachnoid
Pia
(DAP/PAD)
Dura
Tough and fibrous; 2 layers outermost of which fuses with periosteum and lines cranial cavity. Venous sinuses run in the gap between the two layers.
Arachnoid
Covers surface of brain, superficial to subarachnoid space, which is filled with CSF - contains a network of collagen and elastic fibres which link it to the pia matter..
Pia
Tightly attached to the brain by astrocytes; follows contours of the brain
Where is supplied by the somatic nervous system
Body wall, skin and skeletal muscle
What differs between the motor and sensory ganglia?
Sensory have no synapses; motor always has synapses
What is a plexus
redistribution of nerve fibres like a tree.
