Neurotransmission Flashcards
What are the 4 parts of neurons?
- Nucleus
- Cell body
- dendrites
- axon
What are astrocytes?
Type of glial cell (insulation + support of neurons)
- Play an important role in physiological brain function; release/take-up of NT’s (eg glutamate), express receptors like NMDA, regulate synaptic transmission, conduct electrical events via gap junctions
- Also important in brain pathology; form scars (stop axonal regrowth), immune activation
Are Astrocytes homogenic or heterogenic?
Historically thought to be homogenic across brain regions but recently have been found to be different types and even neuroanatomical differences in differing regions!!
There are at least 4 different types in the human cortex
- Protoplasmic**
- Interlaminar
- Fibrous**
- Polarised
Describe the protoplasmic astrocyte…
- Most common type of astrocyte in layers 2-6 of the cortex
- Their GFAP -positive processes don’t overlap; instead have a domain organisation
- 1 astrocytes domain might cover 10 nerve cell bodies, many synapses and 5 blood vessels.
Therefore they’re in an important co-ord. position; eg to regulate blood flow in accordance to synaptic transmission.
**1 human astrocyte’s processes serves approx 2 mill synapses and spans 100-200micrometres!!
Describe the Fibrous astrocytes
- Found in the grey and white matter
- Their processes intermingle (Don’t form a domain structure)
- Probably serve more of a support role (rather then info processing; and also respond to brain injury
Describe the idea of gliotransmission..
“The process of release of transmitters from astrocytes and acting on neurons”
- This hugely expands astrocytes role in brainfunction; eg astrocytic adenosine release induces sleep via caffeine-sensitive receptors
What are Microglia? (note that a type of macroglia are astroytes)
Resident Macrophage of the brain that ‘survey’ the brains micro-environment; very sensitive to brain perturbations.
- Mediate the brains immune response
- Phagocytose debris/bacteria (could they PC amyloid to prevent alheizmers)
- Modulate NT
- Sculpt the brain during development (take-away incorrect connections) and may modulate synaptic transmission
What is the connection between brain endothelial cells and pericytes?
Pericytes encase endothelial cells in brain capillaries and maintain the blood-brain-barrier. (that prevents toxins coming into the brain)
It’s thought that any neurogical disorders like Alzheimers and stroke, the neurovascular unit and BBB are compromised!! (eg amyloid in brain in alzheimers)
How do drugs act on the brain and other organs?
By interacting with other target molecules.
- Enzymes (involved n NT synthesis or degredation)
- Structural Proteins
- ionchannels
- NT uptake proteins
- NT receptors
- Transducer proteins; G-proteins, 2nd messangers
The basic unit of the nervous system is the _______ (>1010) and they make contact with other _______ at _________.
A single ______ can have thousands of ___________.
A few of these convey info from one cell tot he other by ______.
The majority use _________ called ________ which are released (calcium dependent) from the ________ and diffuse across the _________ and act on __________ on the ________ target neuron.
Binding of the NT to the _______ then leads to an ______ in the _____, such as an ion channel opening or generation of a 2nd messanger.
The basic unit of the nervous system is the neuron (>1010) and they make contact with other neurons at synapses.
A single neuron can have thousands of synaptic contacts.
A few of these convey info from one cell to the other by Electrical info.
The majority use chemical messangers called Neurotransmitters (1st messangers) which are released (calcium dependent) from the pre-synaptic membrane and diffuse across the synaptic cleft and act on NT receptors on the post-synaptic target neuron.
Binding of the NT to the receptor then leads to an effect in the target neuron, such as an ion channel opening or generation of a 2nd messanger.
How is termination of transmitter action achieved?
Either:
- Metabolism
- Re-uptake into neurons and/or glial cells (astrocytes) by specific transporter proteins.
The brain is very complex and composed of many different anatomical regions (that serve different functions), therefore the drug action depends not only of the NT system it modulates, but also the __________________
Anatomical localization of the neurotransmitter system.
“Chemical Neuroanatomy”
What’s a neurotransmitter and what are the different types?
Molecule released from the pre-synaptic terminal to act on the post-synaptic terminal to produce an excitatory or inhibitory effect
- Monoamines: serotonin (rafa nuclei), NA, and dopamine
- Aminoacid derivatives: GABA, glutamate, glycine
- Acetyl choline
- Neuropeptides: neuromodulators and co-transmitters
Neuromodulators
Produce slower pre/post-synaptic responses. Released by nerve cells and astrocytes (eg; adenosine released by astrocyte, involved in sleep, stops seizures)
**not quite a neurotransmitter!
Neurotrophic Factors
Released by non-neuronal cells (astrocytes, microglia) and neurons; working over long time-scales.
Act on tyrosine-kinase type receptors to mediate growth, morphology, functional properties, survival promoting effect in the Nervous System (eg nerve growth factor).
*also NOT quite a NT
