What can neuroglia be divided into?
- Microglia
- Macroglia
What types of nerve cells are there?
- Glia (90%)
- Neurones (10%)
Describe the types of Macroglia
- Astrocytes: comprise the blood brain barrier, assist in transfer of nutrients and waste, phagocytic functions, physical support for neurones, found in CNS
- Oligodendrocytes: myelinated up to 250 axons per cell in CNS
- Ependyma: Line ventricles and central canal of spinal chord, found in CNS
- Swann cell: myelinated 1 axon per cell in PNS
- Satellite cells: physical support of neurones in PNS
What is the function of glial cells?
- Support neurones
- Maintain homeostasis
- Form myelin and insulate neurones
What is the function of Microglia?
- Immune and inflammatory functions
- Found in both CNS and PNS
What do neurone cell bodies contain?
- Nissl substance (protein synthesis)
- Nucleus and nucleolus
- Golgi apparatus (packaging transmitters into vesicles)
- Dendrites
Where is the nucleus in healthy neurones?
- Central
What is grey matter?
- Collections of neuronal cell bodies
- Nuclei in CNS
- Ganglia in PNS
What is white matter?
- Collections of axons eg a peripheral nerve
- Fibre tracts in CNS
- Nerves in PNS
How are peripheral nerves arranged?
- Singular axon is covered by endoneurium
- Group of axons in a fascicle is covered by a perineurium
- Group of fascicles and blood vessels in a peripheral nerve is surrounded by an epineurium
What happens if a neurone is severed?
- Nerve stump is formed (proximal segment of axon seals to prevent leakage of cell contents)
- Distal segment dies and undergoes Wallerian degeneration as is cut off from nutritional support of cell body
- Cell body puffs up with increased contents
- Nucleus displaced to the periphery
- Process is chromatolysis
What is an afferent neurone?
- Carries signals from periphery to CNS
- Sensory neurone
What is an efferent neurone?
- Neurone that carries signals from the CNS to the periphery
- Motor or autonomic neurone
How do Schwann cells insulate neurones?
- Doesn’t conduct electricity due to lipid content
How can efferent nervous system (signals from CNS) be divided?
- Somatic
- Autonomic:
~ Sympathetic
~ Parasympathetic
Describe the structure of the somatic NS
- 1 neurone carries signal directly to effector organ
- Effector organ: always skeletal muscle
- Efferents are under-developed at birth but fully developed by puberty
What are the functions of the autonomic nervous system?
- Homeostasis of the internal environments through regulation of systems in the body eg cardiovascular, respiratory, digestive, thermoregulative
- Promotes excretory mechanisms of the body as and when necessary
What are the effector organs of the autonomic nervous system?
- Visceral organs
- Smooth muscle
- Secretory glands
- Cardiac muscle
Compare the sympathetic and parasympathetic systems within the autonomic nervous system
- Common standard anatomical layout eg same number of synapses
- Differ in detail of respective anatomy eg lengths of neurones
- Equal number of synapses in a series arrangement
- Various synapses use different neurotransmitters
What is the general layout of the autonomic nervous system?
- 2 neurones meet at a ganglion in the PNS
- One cell body in the CNS (pre-ganglionic neurone)
- One cell body in the PNS (post-ganglionic neurone)
- Post-ganglionic neurone ends at the effector organ
- Meninges is the barrier between CNS and PNS
What is the outflow for the sympathetic nervous system?
- Thoraco-lumbar outflow
What is the outflow for the parasympathetic nervous system?
- Cranial-sacral outflow
Describe the structure of the sympathetic nervous system
- Nerve fibres have cell bodies in all 12 thoracic sections and the first 2 lumbar sections
- Have short pre-ganglionic neurones and long post-ganglionic neurones
Describe the structure of the parasympathetic nervous system
- Long pre-ganglionic neurones and short post-ganglionic neurones
