1.3/1.4 (Types of neurons and synapses + cortex) Flashcards
What is Dale’s principle
Dale’s principle states that a neuron releases the same set of neurotransmitters at all of its synaptic connections. This concept suggests consistency in neurotransmitter release across a neuron’s terminals, although exceptions and co-release of multiple neurotransmitters have been observed.
What does Dale’s principle suggest about the excitatory or inhibitory nature of neurons
According to Dale’s principle, the majority of neurons can be roughly classed as excitatory neurons whose outgoing synapses are all excitatory, or inhibitory neurons whose outgoing synapses are all inhibitory. It is important to un- derstand that the division relates to the outgoing signals, neurons usually receive a mixture of excitatory and inhibitory signals.
What is the difference in locality between inhibitory and excitatory neurons
In cortex, inhibitory neurons tend to be small and to have only local connec- tivity; they are also diverse with many different types: basket cells, stellate cells, fast-spiking PV cells, and many others. The excitatory neurons are usually larger, they tend to have local and distal connections and come in varieties of one main type: the pyramidal cell. It is tempting to think of the pyramidal cells as doing ‘the work’ and the inhibitory cells as helping modu- late and sculpt the activity of the pyramidal cells. It remains to be seen if that is a useful way of thinking of what happens. In other parts of the brain there are circuits where the principal cells, the ones tasked with signalling outside of the region, are inhibitory.
What is the main excitatory neurotransmitter
Glutamate
What are the primary glutamate receptor types
There are different receptor types for glutamate, the main ones are called NMDA and AMPA; the acronyms are short for complicated chemical names and we are, here, straying into more detail than we need. The main point is that NMDA and AMPA receptors have different behaviours, both in short-term in the time course of their binding to the transmitter, and in the longer term, in how they change in number and strength in response to what is happening at the synapse. A glutamate synapse will usually have a mixture of ligand-gated channels with NMDA and AMPA receptors.
What is the most common inhibitory neurotransmitter
GABA
What are the primary GABA receptor types
The story for inhibitory synapses is more complex even than the story of excitatory synapses: the two classes are ionotropic receptors and metabotropic receptors. Metabotropic receptors trigger biochemical signals, rather than modulating voltage dynamics via the conductance’s of ligand-gated ion channels.
What are neuromodulators (name the big five)
Neuromodulators are chemicals that can change the behaviour of a neuron or synapse; there are a lot of different neuromodulators, but the ‘big five’ are serotonin, dopamine, acetylcoline, histamine, and noradrene- line (also called norepinephrine).
How are neuromodulators typically released
Neuromodulators are released at synapses by specialised cells that are usu- ally found in specific brain regions but with axons that spread over the whole brain. Sometimes the neuromodulator is released to one post-synaptic cell, but often they are released into the extracellular fluid so that they affect a group of cells.
What is the effect of neuromodulators
It is common to think of neuromodulation as adjusting the computational circuit, like a series of knobs and levers which can up- or down-regulate the computational dynamics and they do so over different timescales. These neuromodulators are very interesting because they seem to link the quite low-level details of how circuits work, they are produced by neurons in re- sponse to signals to those neurons, and high-level behaviours. Changes in neuromodulation can be linked to different decision-making strategies and can, it is thought, be experienced as mood.
What is the cortex
How many neurons are in the cortex
14-15 billion neurons
Why is the cortex folded
How thin is the cortex. And how many layers does it have
2-5 mm. 6 layers
What is Broca’s area
Broca’s area is a region in the frontal lobe of the brain, typically in the left hemisphere, involved in language processing, speech production, and comprehension. Damage to this area can result in Broca’s aphasia, where individuals understand speech but struggle with producing fluent speech.
What was the only word that the patient with damage to Broca’s area could say
Tan
What do the layers of the cortex look like
What is expressive aphasia
Aphasia means a problem with speech and in expressive aphasia the problem is with the production of speech.
What is Wenicke’s area, and what does damage to it result in
Another part of the brain, Wernicke’s area, was soon identified with fluent aphasia. A patient with fluent aphasia can have a large vocabulary but produces what is called ‘word salad’, lots of words included many which are not related to the subject of speech.
Which section of the brain (visually) are the motor and somatosensory cortices
Does the brain have sensory nerve endings?
Sticking to the cortex, in the first half of the twentieth century the neurosur- geon Wilder Penfield pioneered a technique in neurosurgery, still important today, of waking the patient up during the surgery and stimulating parts of the brain: because the brain itself has no sensory nerve endings this is pain- less, though it must be alarming. This allowed him to work out which parts of the brain could be operated on, or removed, while causing the least damage to crucial abilities.
Does different parts of the somatosensory correspond to different parts of the body when stimulated
Yes
Note: Further along the pathway there is mixing (ie lip reading enhances hearing)
Where are memories stored in the cortex?
Trick question. We know now that accounts of cortical memory are not
so straight-forward, there are areas of the cortex linked to certain types of
memory and areas of the cortex more likely to store memories than others,
but it does indicate that there is no easy way to describe the localisation of
cortical function.
