Neuroscience 2 - Cells of the Nervous System Flashcards
Describe the internal structure of the neurone.
- Large nucleus
- Prominent nucleolus
- Abundant rough ER
- Well developed golgi
- Many mitochondria
- Highly organised cytoskeleton
Describe the structure of the dendrites of neurones.
- They spread from the cell body and branch frequently
- Covered in protrusions called spines
- Spines recieve the majority of synapses
- Primary dendrites split into secondary dendrites and then these split into tertiary dendrites.
Describe the structure and function of axons of neurones.
- These conduct impulses away from the cell body
- Emerge from the axon hillock
- One per cell
- May branch after leaving the cell body and at the target
- Has prominent microtubules and neurofilaments (for structural support)
- Myelinated or unmyelinated
Describe the structure of axon terminals
- Axons branch extensively close to the target, forming a synaptic terminal
- Boutons are right at the end of the axon
- Varicosities are swellings on the axon containing neurotransmitters
Describe the structure of the synapse
- Synaptic vesicles are packaged in the golgi
- Many mitochondria, required for ion pumping.
List the types of synapse
- Axo-dendritic (excitatory)
- Axo-somatic (inibitory)
- Axo-axonic (modulatory)
Which part of the neurone do the axo-dendritic synapses communicate with?
The axon communicates with the dendrites
Which part of the neurone do the axo-somatic synapses communicate with?
They communicate with the cell body (soma)
Which part of the neurone do the axo-axonic synapses communicate with?
They reduce the action potential on the axon of another neurone, preventing stimulation of the following neurone.
Describe the process of transport across the axon.
- Vesicles are transported up or down the neurone via motor proteins on microtubules.
- The microtubules have different ends. One end is positive, and the other is negative. The positive end is at the bottom of the axon.
- Different constituents are used for retrograde transport (from + to -) and anterograte transport (from - to +)
Where are pseudounipolar neurones found?
Sensory neurones, they have one axon that splits into two
Where are bipolar neurones fond?
They are retinal, in the cerebral cortex white matter.
Describe the structure and function of golgi type 1 multipolar neurones.
- Highly branched dendritic trees
- Axons extend long distances
- Pyramidal cells of the cerebral cortex
- Purkinje cells of the cerebellum (15 mill)
- Anterior horn cells of the spinal cord
- Retinal ganglion cells
Describe the structure and function of golgi type 2 multipolar neurones.
- Highly branched dendritic trees
- Short axons
- Axons terminate quite close to cell body
of origin - Stellate cells of the cerebral cortex
and cerebellum
Describe the structure of astroglia
- Multiprocessed starlike shape
- Most numerous cell
type - Numerous
intermediate
filament bundles in
cytoplasm of fibrous
astroglia (GFAP) - Gap junctions
suggest astroglia-astroglia signalling
Describe the functions of astroglia
- Scaffold for neuronal migration and axon growth
during development. - Formation of blood-brain barrier.
- Transport of substances from blood to neurons.
- Segregation of neuronal processes (synapses).
- Removal of neurotransmitters.
- Synthesis of neurotrophic factors.
- Neuronal-glial and glial neuronal signalling
- Potassium ion buffering
- Glial scar formation
Describe the process by which astrocytes remove neurotransmitters.
- The end foot of astrocytes interfere with neurotransmitters in the synapse.
- They transport the neurotransmitters into the cell, alongside potassium and water.
Describe the structure of oligodendroglia.
- Small spherical nuclei
- Few thin processes
- Prominent ER and Golgi
- Metabolically highly
active
Describe the functions of oligodendroglia .
- Production and maintenance of the myelin sheath - Each cell produces multiple sheaths
Describe the structure of myelin.
- A lipid rich insulating membrane - Up to 50 lamellae (thin membranes) - Dark and light bands seen at EM level
Describe the function of microglia.
- Resident macrophage population of the CNS
- Involved in immune surveillance
- Present antigens to invading immune cells
- First cells to react to infection or damage
- Role in tissue modelling
- Synaptic stripping
Where are microglia derived from?
Bone marrow
Describe the structure of schwann cells.
- Schwann cells perform the function of the astrocytes and the oligodendrocytes
- They myelinate a single axon.
- They promote axon regeneration
Why cant axons be myelinated by single cells in the CNS as occurs in the PNS?
This would take up more space; the brain would need to be considerably bigger.
