19.2 Structure and Function of Neurons and Glia Flashcards
Compare projection neurons and interneurons in terms of:
- Appearance
- Function
- Neurotransmitters
[IMPORTANT]
Projection neurons:
- Have long axons that project to distant areas of the brain and out of the brain also
- Usually excitatory
- Glutamatergic neurons
Interneurons:
- Have short axons that synapse onto local cells
- Usually inhibitory
- GABAergic
Compare the excitatory and inhibitory neurons in the cerebral cortex.
Excitatory
- 80% of neurons
- Usually glutamatergic
- Projection neurons tend to be excitatory
Inhibitory
- 20% of neurons
- Usually GABAergic
- Interneurons tend to be inhibitory
What are the different types of glial cells in the CNS and PNS?
- Macroglia:
- Astrocytes (in CNS), Satellite cells and enteric glial cells (in PNS)
- Oligodendocytes (in CNS), Schwann cells (in PNS)
- (Ependymal cells are sometimes considered macroglia too)
- Microglia (only in CNS)
What are radial glial cells?
The term can be used to mean two things:
- Progenitor cells that give rise to all neurons of the cerebral cortex, as well as astrocytes and oligodendrocytes
- Specialised astrocytes (Muller cells and Bergmann glial cells)
Define glial cells.
- Glial cells used to be defined by the fact that they (1) separate neuronal elements from mesodermal layers and (2) should originate from embryonic ectoderm.
- However, this excluded microglia, which are of mesodermal origin.
- Therefore, glia are not defined by the types of proteins they express.
Describe the shape of astrocytes.
They are star-shaped.
What are the functions of astrocytes?
In spec:
- CNS development
- Ion homeostasis
- Neurotransmitter uptake
- Local control of blood flow
- Blood brain barrier
- Inhibitory role in CNS repair
How are astrocytes involved in CNS development?
- Needed for neurogenesis
- Guide neuronal migration -> Cells can migrate along their radial fibres
- Aid formation of grey matter
- Involved in synaptogenesis
How are astrocytes involved in homeostasis?
They control levels of extracellular potassium, extracellular pH, water and are involved in neurotransmitter removal.
How are astrocytes involved in support?
- Metabolic support -> Provide lactate to neurons
- Structural support -> Formation of neuro-vascular unit (since they link the cells of the vessel with the neurons)
How are astrocytes involved in the blood brain barrier?
Astrocytes induce the blood brain barrier.
How are astrocytes involved in blood flow regulation?
- They secrete vasoconstrictors or vasodilators
- These act on the pericytes that surround capillaries (the mechanism is not known)
- This means that blood flow can be regulated depending on the requirements of the neurons
How are astrocytes involved in brain defence and post-injury remodelling?
Assist in:
- Scar formation
- Immune responses and secretion of pro-inflammatory factors (cytokines, chemokines and immune modulators)
Are astrocytes found in the CNS or PNS?
CNS -> Their PNS equivalents are satellite cells and enteric glial cells.
What are the myelin-expressing cells in the CNS and PNS?
- CNS -> Oligodendrocytes
- PNS -> Schwann cells
What is the function of oligodendrocytes and Schwann cells?
They are involved in myelination, which increases the speed with which action potential are propagated along the axon.
What are microglia?
[IMPORTANT]
They are the endogenous macrophages of the CNS.
- Remove cell debris from injury sites
- Modulate local inflammation
- Phagocytose excess neurons
What are the main functions of microglia?
They are the macrophages of the CNS, involved in:
- Brain development
- Maintenance of physiological homeostasis
- Pain
T/F - Inhibitory proteins on the surface of oligodendrocytes are a major reason why the CNS does not regenerate
True
What are the different types of neuron structure? (4)
- Unipolar
- Pseudounipolar
- Bipolar
- Multipolar
Which type of neuron is this?
Unipolar
Which type of neuron is this?
Bipolar
Which type of neuron is this?
Pseudounipolar
Which type of neuron is this?
Multipolar
How are projection neurons different to interneurons?
- Larger with longer axons and dendrites
- Slower to fire
- Greater frequency adaptation
Role of neurons vs glia?
Neurons: info processing, signalling
Glia: support, contribute to neural function
What are the two different sites of neurotransmitter release?
- Axonal presynaptic membranes
- Varicosities
What are the neuron cytoskeleton components (3)?
- Microtubules
- Neurofilaments
- Microfilaments
What are the origins of macroglia and microglia respectively?
Macroglia: from ectoderm
Microglia: from mesoderm
What cells fall under macroglia?
Astrocytes, oligodendrocytes, ependymal cells
Label each neuroglial cell type shown
How are astrocytes involved in scar formation?
After injury - astrocytes undergo morphological changes:
- Extend processes
- Increase synthesis of glial fibrillary acidic protein (GFAP)
- Overall, form a dense web of processes that fills empty space where dead neurons are
Name the parts that make up a neuron
Soma: Neuronal cell body
Axons
Dendrites
What type of neuron is this?
Anaxonic neuron
-Does not produce true action potentials
-Mediates local electrical changes in CNS of other neurons
What type of neuron is this?
Multipolar neuron
Includes most interneurons (only connect with other neurons) and other neurons in the CNS
Multiple neurites (axons and dendrites/two or more dendrites)
What is the role of astrocytes in the CNS immune response?
*regulation
*Modulation of BBB for immune cell entry
*Epigenetic modifications in teh case of specific stimuli/ autoimmune to form a more robust response
*Glial scar formation
