Cells and tissues of the nervous system Flashcards
What are the 2 main types of cells associated with the nervous system
Neurons:
- Structural and functional unit
- Excitable cells
- Impulses carried as action potentials
Glial cells:
- Non-excitable supporting cells
- Much smaller than neurons
A typical neurone has _______ dendrite(s) and ______ axon(s)
Multiple dendrites and one axon
Identify the parts of a neuron
In which direction do action potentials travel in a neuron?
In one direction only, from the cell body to the synaptic terminals at the end
What are the 3 types of neuron?
Multipolar, Bipolar, Pseudounipolar
What types of nerves use Multipolar neurones?
Motor neurones
Interneurons
What nerves use pseudounipolar neurones?
Sensory neurones are pseudounipolar
Cell bodies are contained in Ganglia
What are bipolar neurones used for?
Olfactory mucosa
Retinal nerve fibres
What is contained in the cell body of neurones?
Describe the main features of each
Nucleus:
- Loose chromatin, prominent nucleolus
Organelles:
- Mitochondria (v metabolically active so needs them)
- Ribosomes
- rER (Nissl bodies)
- Diffuse Golgi apparatus
What is the cytoplasm called in the cell body and axon?
Cell body = Perikaryon
Axon = axoplasm
Neurones are long-living but are ‘amitotic’
What does this mean?
They don’t regenerate
What is the purpose of myelin?
The Myelin sheath envelopes the axon to increase the conduction speed through ‘saltatory conduction’
Axons can be myelinated or un-myelinated
What types of Glial cells produce the myelin sheath around neurones?
PNS = Schwann cells
CNS = Oligodendrocytes
De-myelination of axons is associated with what disease?
Multiple sclerosis
MRI will show white patches of demyelination
Identify the labels in the cross section of the spinal cord
What is mainly found in the white matter of the spinal cord?
Why is this area white?
Bundles of myelinated axons
Myelin comes from the cell membranes of oligodendrocytes that are in the white matter
Cell membranes are made of phospholipids which is whitey in colour
What is found in the grey matter of the spinal cord?
Neuronal cell bodies
These aren’t enveloped in myelin - so are grey instead of white
Identify the labels
Remember that nuclei show up as deep purple on stains. You can see the nuclei in the cell bodies.
The axons are lighter purple and have a white band around them. The white band is the myelin sheath
In the white matter of the spinal cord, you will find tracts.
What are these?
Axons with Different modalities of sensory and motor impulses are bundled together to form tracts in the white matter
Different tracts carry impulses up/down at different speeds related to what they carry information for.
EG - One of the ascending (sensory) tracts carries touch and pressure impulses
What are these arrows pointing at?
Nuclei in the brain
This name is given to any collection of grey matter (cell bodies) within the Central nervous system
What are the types of Glial cells in the CNS?
Astrocytes (most common)
Oligodendrocytes
Microglia
Ependymal cells
What do astrocytes do?
Astrocytes (‘star-cells’) are the most numerous glial cells in the CNS that have projections that have ‘end feet’
These surround synapses and localise the release of neurotransmitters (stop the activation of other neurons/leaking etc)
They also surround capillaries and help in K+ buffering (blood-brain barrier)
What do Oligodendrocytes do?
These are large glial cells that produce myelin to envelop axons in the CNS
The myelin is just taken from their cell membrane.
What is the function of Microglia?
Microglia are CNS glial cells that are involved with immune defence and repair. Their functions are:
- Phagocytosis
- Scar tissue formation
They look similar to astrocytes but are smaller
