Lecture 1: Cellular Components Flashcards
What are the different types of glia?
- Oligodendrocytes
- Microglia
- Astrocytes
- Ependymal cells
- Radial glia
How are Neurones classified?
- Structurally/Morphologically: Unipolar, Bipolar, or Multipolar neurones
- Location: eg. Cortical pyramidal cells as they are found in the cortex
Phenotypically
- Functionally: Sensory, motor, or interneurons, based on the direction of signal transmission and their role in the nervous system.
- Chemical: What type of neurotransmitters do they use to communicate with other cells.
What are the properties Neurones?
Excitability: They can respond to stimuli by generating an electrical signal.
Conductivity: Transmit signals over long distances through their processes.
Release Neurotransmitters: Allows them to communicate with other Neurones and cells.
Plasticity: Undergo structural and functional changes.
What does the functional phenotype of a neurone describe?
The functional phenotype of a neuron is like a “personality” for the neuron - it describes how the neuron behaves and what it does in the nervous system.
e.g. motor neurone which excites skeletal muscle cells for motor function
What are different types of functional phenotype?
motor neurone, excitatory neurone
How can the functional phenotype of a neurone be identified?
- Electrophysiologically (measuring and directly recording the activity)
- Observing the effect of exciting the neurone, i.e. What effect does exciting the neurone have on the synaptic target.
What does the chemical phenotype of a neurone describe?
which neurotransmitter is produced by the neurone e.g. acetylcholine (cholinergic neurone)
How can the chemical phenotype of a neurone be identified?
- Direct labelling (immunohistochemistry)
- mRNA (in situ hybridisation)
- Genetic markers
What are the most essential parts of a neurone
- Dendrites
- Cell body/Soma
- Axon hillock
- Axon
- Synapse
How does information flow occur in neurones?
Dendrites -> Cell body -> Axon
What is the role of the cell body of a neurone?
information is integrated and sent out through the axon
What are synaptic processes?
communication between neurones, can be axo-dendritic and axo-somatic
What is myelin characterised by?
specialised properties for electrical conduction
Are there more neurones or glia in the nervous system?
there are more glia in the nervous system
What is the role of satellite cells?
supports cell bodies
What is the role of Schwann cells (PNS) and oligodendrocytes (CNS)?
forms myelin sheaths
What is the role of microglia?
1.Immune cells found in the central nervous system.
2. Monitor the brain for damage, infection, and abnormal activity.
3. Can engulf and destroy harmful substances through phagocytosis.
4. They release cytokines and other molecules to recruit other immune cells to the site of injury or infection.
5. Help to shape the developing brain by removing weak or unnecessary synapses.
What is the role of ependymal cells?
Ependymal cells produce and circulate cerebrospinal fluid in the central nervous system.
What is the role of astrocytes?
- Involved in NT uptake as they have glutamate transporters
- Possess an array of ion transporters to clean up extracellular spaces between neurones (Extracellular homeostasis)
- Regulate local micro-vasculature and blood flow
important for the BBB - Release Gliotransmitters
- Help maintain the integrity of the blood brain barrier
Why do astrocytes depolarise after neurones?
levels of extracellular potassium increases dramatically following the depolarisation of neurones and is taken up by astrocytes which become activated
Why don’t astrocytes suffer from potassium toxicity?
- Astrocytes are connected to each other by channels called gap junctions.
- Gap junctions allow potassium to move between astrocytes.
- If one astrocyte has too much potassium, it can move through the gap junctions to another astrocyte with less potassium.
Why do arterioles dilate as neural activity increases?
activation of neurones results in increased metabolic demand, producing metabolic waste which needs to be excreted.
What is the role of astrocytic end-feet?
- Astrocytic end-feet help regulate blood flow in the brain
- They control the diameter of blood vessels they wrap around
- They aid in moving nutrients and waste products between blood vessels and brain cells to keep the brain healthy
What are tripartite synapses?
Astrocytic foot processes contact both pre- and post-synaptic areas
What are Gliotransmitters?
Chemical transmitters released by astrocytes -> not only are they passive cleaners but astrocytes actively participate in cellular communication in the brain
What stimulates the release of gliotransmitters?
- Increased activity in adjacent neurones and astrocytes
- Increased [Ca2+] in astrocyte
- Release Gliotransmitters (e.g. glutamate, ATP)
What are characteristics of a neural circuit?
essential for complex functions, output varies depending on constituent components
What is the functional phenotype of a neurone usually determined by?
the NT released -> effect on post-synaptic receptor (however exact effect of NT can depend on the post-synaptic receptor esp. GPCRs)
What is a convergent circuit?
when multiple neurones send axons to a single neurone
What is a divergent circuit?
when a neurone sends axons to multiple neurones
What are different types of circuits?
convergent, divergent, feedback, lateral excitation, feedforward inhibition, feedback inhibition and disinhibition
How was the Cholinergic Motor Neurone named?
Functional phenotype: Motor Neurone
Chemical Phenotype: Acetylcholine, thus it became Cholinergic
What is glutamate?
Glutamate is a neurotransmitter that is released into the synaptic cleft when a neuron fires.
What happens when there is excess glutamate in the synaptic cleft?
Excess glutamate in the synaptic cleft can lead to excitotoxicity and damage to the postsynaptic neuron.
What is glutamate uptake?
Glutamate uptake is the process by which astrocytes take up excess glutamate from the synaptic cleft and convert it into a non-toxic form.
What is excitotoxicity?
Excitotoxicity is a process that occurs when there is excessive stimulation of neurons by the neurotransmitter glutamate, leading to the over-activation of excitatory receptors on the postsynaptic neuron and subsequent damage or death of the neuron.
What is extracellular ion homeostasis?
Extracellular ion homeostasis is the maintenance of a balance of ions, such as sodium, potassium, and calcium, outside of cells in the body. Astrocytes are involved in the process.
What is the role of astrocytes in the neurovascular unit?
- Astrocytes regulate blood flow
- Maintain the blood-brain barrier
- Provide nutrients to neurones
- Regulate ion homeostasis.
