L2/L3 Flashcards
What is the brain made of?
- neurons account for only about 10% of our brain cells.
* Glial cells account for about 90% of our brain cells, but their role is mainly supportive.
what does communication between neurons in the brain enables
• Communication between neurons in the brain enables our behaviours and thoughts.
what does cognition depend on
• Cognition depends on the activity of neurons as well as the transmission of information between
neurons.
what is the role of neurons
- Neurons are the basic signalling unit.
* Neurons receive information, process it, and then transmit the output to other neurons.
what is the function of neurons
• Function: Communication via electrical and chemical signals
how are neurons distinguished
• Neurons are distinguished by their function, location, and interconnectivity.
describe the structure of neurons
• Structure: – Dendrites – Soma (or cell body) – Axon – Axon terminals
describe dendrites
- Dendrites extend from the cell body.
* Dendrites are (usually) treelike processes that receive inputs from other neurons.
what is the central part of the neuron
• The soma is the central part of the neuron.
describe the soma and its function
• The soma contains metabolic machinery that maintains the neuron; this machinery is suspended in fluid and surrounded by the cell membrane.
what is the axon
• The axon extends from the cell body.
what is the function of the axon
• The axon functions like a telegraph wire, sending electrical impulses to distant sites in the nervous system.
describe axons
• The axon extends from the cell body. • Axons vary in length from less than a millimetre to over a metre. • Some axons are covered in myelin. • Axons often branch
in the CNS what is myelin formed by
• Myelin is formed by oligodendrocytes.
what is myelin
• Myelin is a fatty substance that surrounds and insulates nerve fibres (i.e., axons). therefore it appears white.
what is the function of myelin
• Myelin facilitates the conduction of nerve impulses (i.e., speeds up the signal).
what is the relationship between myelin and MS
• The importance of myelin becomes obvious when you consider the pathology and symptoms of multiple sclerosis (MS). • The pathology associated with multiple sclerosis causes the destruction of myelin.
describe a synapps
- The synapse is where the axon terminal of one neuron contacts another neuron in order to transmit information.
- The synapse has two sides: presynaptic and postsynaptic (information flows from the presynaptic neuron to the postsynaptic neuron).
describe the terms pre and postsynaptic
- Presynaptic = before the synapse, with respect to the flow of information (e.g., axon terminals are presynaptic because they are positioned before the synapse)
- Postsynaptic = after the synapse, with respect to the flow of information (e.g., dendrites are postsynaptic because they are positioned after the synapse)
At most synapses, information in the form of electrical impulses travelling down the axon is converted
in the axon terminal into a chemical signal that crosses the synaptic cleft.
what s this chemical signal called
a neurotransmitter.
what happens on the postsynaptic membrane when it receives the chemical signal
• On the postsynaptic membrane, this chemical signal is converted back into an electrical signal.
describe neurotransmitters
- Neurotransmitters are stored in and released from synaptic vesicles within the axon terminal.
- Different neurotransmitters are used by different types of neurons.
glial cells account for how much of the brains volume
Glial cells account for more than half of the brain’s volume.
what is the role of glia
• Glial cells support neurons.
what are the main types of glia
• Main types of glial cells in the CNS:
– Astrocytes
– Oligodendrocytes
– Microglia
what is the role of astrocytes
• Astrocytes form a barrier between neuronal tissue
and blood, called the blood-brain barrier (BBB).
what is the role of the BBB
• The BBB protects the CNS from some molecules in
the bloodstream.
what is the role of oligodendrocytes
• Oligodendrocytes myelinate axons
• Oligodendrocytes form myelin by wrapping their cell
membranes around the axon during development.
• The myelination of one axon requires many oligodendrocytes.
what is myelin
(myelin is a fatty substance that surrounds the axons of many neurons and speeds neural communication).
what is the role of microglia
• Microglia devour and remove debris left by dead or degenerating brain cells.
what happens once microglia have cleaned up by the debris
Once the microglia have cleaned up by the debris you end up with a fluid filled hole much like a ventricle because cells there have died and it becomes filled with CSF
what causes an AP to be propagated
• Note that each neuron can receive input from many other neurons and can output to many other neurons.
• Sufficient input to the postsynaptic neuron can trigger an action potential, causing the electrical signal to
be conducted down the axon.
what do AP trigger
• Action potentials trigger synaptic transmission.
what is synaptic transmission
• Synaptic Transmission = Neuronal Communication
what is a AP
• An action potential is a rapid change in the voltage of the cell’s membrane.
What normally causes action potentials?
- Sufficient input can trigger an action potential.
* For example, moving a whisker on a rat can cause somatosensory neurons to fire rapidly.
what is a single cell recording
• Single cell recording involves recording action potentials from an individual neuron.
what do single cell recording measure
• Using single cell recording, we can measure the activity of an individual cell while different stimuli are
viewed.
what is a receptive field
All visually sensitive cells only respond to stimuli in a limited region of space.
• This region of space is referred to as that cell’s receptive field
How many neurons participate in the representation of a single visual image?
• Functional imaging techniques, such as fMRI, provide an opportunity to explore this issue because they
allow the simultaneous detection of the entire neuronal population responding to each stimulus.
• fMRI is an adaptation of MRI that records changes related to metabolic activity in order to produce a
functional view of the brain.
• Because the signal from fMRI is approximately proportional to neuronal activity, this method can be
used to estimate the number of neurons involved in a specific cognitive process.
• Using a complicated calculation, the researchers determined that at least two hundred million neurons in
the visual cortex are involved in the representation of a single image.
what is the difference between fMRI and MRI
• fMRI is an adaptation of MRI that records changes related to metabolic activity in order to produce a
functional view of the brain.
what defines the tonotopic map
• In primary auditory cortex, the frequency tuning properties of the cells define a tonotopic map.
what is seen when looking at the activity of neurons in the olfactory bulb
- The activity of many neurons in the olfactory bulb was recorded.
- Different scents evoked different spatial patterns of neural activation in the olfactory bulb.
- The different patterns of activity can account for the ability to discriminate these three scents.
- Consider two distinct scents that cannot be distinguished.
what are other examples of topographic maps in the brain
• Topographic maps are also seen in primary motor cortex and primary somatosensory cortex.
