Session 6: Organisation of the Nervous System Flashcards
What are the four structural classes of neurons?
Multipolar, bipolar, pseudo-unipolar, unipolar
What are the three functional classes of neurons?
Sensory neurons, interneurons, motor neurons
Sensory neurons transmit information ___ the CNS. Their axons form ___ fibres.
Sensory neurons transmit information towards the CNS. Their axons form afferent fibres.
Motor neurons transmit impulses ___ from the CNS and towards ___ organs. Their axons form ___ fibres.
Motor neurons transmit impulses away from the CNS and towards effector organs. Their axons form efferent fibres.
Interneurons are the smallest neurons, and they have a ___-polar morphology. They make up at least ___% of the neurons of the nervous system, and are contained mostly within the brain or spinal cord, but also in the ___ nervous system.
Interneurons are the smallest neurons, and they have a multi-polar morphology. They make up at least 95% of the neurons of the nervous system, and are contained mostly within the brain or spinal cord, but also in the enteric nervous system. (gut)
High densities of neuron cell bodies form an outer layer of ___ matter in the brain.
High densities of neuron cell bodies form an outer layer of grey matter in the brain.
Neurons are the functional units of the nervous system, comprising about ___% of its total cell number. The remaining ___% are support (glial) cells.
Neurons are the functional units of the nervous system, comprising about 10% of its total cell number. The remaining 90% are support (glial) cells.
Inner ___ matter is comprised largely of myelinated axons.
Inner white matter is comprised largely of myelinated axons.
In the CNS, collections of neuronal cell bodies are known as ___
In the CNS, collections of neuronal cell bodies are known as nuclei.
In the PNS, collections of neuronal cell bodies are known as ___
In the PNS, collections of neuronal cell bodies are known as ganglia.
The vast majority of primary brain tumours are tumours of ___ cells.
The vast majority of primary brain tumours are tumours of glial cells.
What are the glial cells of the CNS?
Astrocytes, Oligodendrocytes, Ependyma, Microglia
Astrocytes: Support in the transfer of nutriets and waste products between neurones and blood.
Oligodendrocytes: Myelinate axons
Microglia: Act as immune cells in the CNS (macrophages)
Ependymal Cells: Line brain ventricles and produce cerebrospinal fluid (CSF).
What do astrocytes do?
- Assist in transfer of nutrients and waste products between neurons and blood
- Provide physical support for neurons
- Their foot processes constitute the BBB along with pericytes
What do oligodendrocytes do?
- Myelinate axons (~up to 250 different axons simultaneously)
What do ependyma do?
- Line ventricles and central canal of spinal cord for production and circulation of CSF
Why is grey matter - grey?
Neuromelanin - conducting polymer
What are the glial cells of the PNS?
Schwann cells, satellite cells, microglia
What do Schwann cells do?
- One Schwann cell myelinated one axon
- Axon repair
What do satellite cells do?
Physical support to neurons in PNS (particularly in ganglia)
What do microglia do?
Macrophages, phagocytic
In the PNS, what are axons wrapped in to produce myelin?
Schwann cells
In the CNS, what are axons wrapped in to produce myelin?
Oligodendrocytes
What is myelin sheath?
A layer of insulating fatty tissue segmentally encasing the fibers of many neurons; enables vastly greater transmission speed of neural impulses as the impulse hops from one node to the next. High lipid content (contains cholesterol, glycolipids, sphingomyelin).
What is saltatory conduction?
The jumping of action potentials from one node of Ranvier to the next. These gaps have a high concentration of voltage-gated Na+ channels, recapitulating an action potential.
