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Neurobiology summary DT1 book
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summary: all the material you need to know for dt1 in the neurobiology course to study biology at the UU
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Chapter 1:Broad categories of nervous cells:
1. Nerve cells / neurons:
a. They generate electrical signals over long distances.
2. Glial cells / neuroglia / glia
a. Support the signaling functions of nerve cells rather than generating
electrical signals themselves.
b. Contributing to repairing nervous system damage, acting as stem cells in
some brain areas where they promote regrowth of damaged neurons in
regions where regeneration can usefully occur.
c. They prevent regeneration in areas where regrowth could do more harm
than good.
Mitochondria are more concentrated at synapses in neurons, while protein-synthetic
organelles are excluded from the axons and dendrites.
Convergence: the number of inputs to a single neuron.
Divergence: the number of targets innervated by any one neuron.
Relatively short axons are a feature of local circuit neurons, or interneurons. While the
axons of projections neurons are longer.
Types of glial cells:
1. Astrocytes: They are restricted to the central nervous system. An important
function is to maintain, in different ways, an appropriate chemical environment for
neuronal signaling, including the formation of the blood-brain barrier.
2. Oligodendrocytes: they are restricted to the central nervous system and are
surrounded with a wrapping called myelin. Myelin increases the speed of the
transmission of electrical signals. The cells that provide the myelin are called
Schwann cells.
3. Microglial cells: are derived from hematopoietic precursor cells. Their main
function is to remove cellular debris from sites of injury or normal cell turnover.
Furthermore, they secrete cytokines to modulate local inflammation and influence
whether cells live or die.
Another type of glial cell is the glial stem cells that are found throughout the adult brain.
These cells retain the capacity to proliferate and generate additional precursors or
differentiated glia and sometimes even neurons.
1. Subset of astrocytes found primarily near the ventricles (in a region called the
subventricular zone). They can give rise to stem cells, neurons and mature
astrocytes and oligodendrocytes and thus are the key to proliferation, self-renewal
and the capacity to make a lot of different cell types.
2. Oligodendrocyte precursors scattered throughout the white matter. They give rise
primarily to mature oligodendrocytes.
Neuronal circuits: neurons are organized in different groups that process specific
information.
Neuropil: dense area with unmyelinated axons, dendrites and glial cells.
Afferent neurons: nerve cells that carry information from the periphery toward the brain
or spinal cord.
Efferent neurons: nerve cells that carry information away from the brain or spinal cord.
Interneurons: participate in the local aspects of the circuit.
Afferent, Efferent and interneurons are the basic constituents of all neural circuits.
Ways to study the neural circuits:
1. Extra- / intracellular recording
2. Calcium imaging: records the changes in intracellular concentration of calcium
ions that are associated with action potential firing.
, 3. Optogenetics: a molecular genetic tool by which they incorporate bacterial opsins
to modify the neuronal excitability: bacteriorhodopsin, halorhodopsin and
channelrhodopsin.
Extracellular recording: an electrode is placed near the nerve cell of interest. This is
useful for detecting temporal patterns of action potential activity and relating those
patters to stimulation by other inputs.
Intracellular recording: an electrode is placed inside the cell of interest. This is useful for
detecting the smaller, graded changes in electrical potential that trigger action potential
and thus allows a more detailed analysis of communication among neurons within a
circuit.
The central nervous system (CNS) comprises of the brain and the spinal cord.
The peripheral nervous system (PNS) includes the sensory neurons. The motor neurons
make op the somatic motor division of the PNS. The cells and axons that innervate
smooth muscles make up the visceral or autonomic motor division.
Grey matter: an accumulation of cell bodies and neuropil in the brain and spinal cord.
- Nucleus: a local accumulation with neurons that have similar connections and
functions. They are found throughout the cerebellum, diencephalon, brainstem
and spinal cord.
- Cortex: sheetlike arrays of nerve cells. They are found in the cerebral hemispheres
and the cerebellum.
White matter: this consists of axon tracts and commissures.
Commissures: tracts that cross the midline of the brain, like the corpus callosum.
Genetic analysis of neural systems:
1. GWAS: a genetic variant will occur more than chance in a big study for a disorder
thus will stand out and be associated with the disorder of interest.
2. Genetic engineering: a method in which the genomic information will be
manipulated.
a. Homologous recombination: knock-in and knock-out mice are made by
using DNA repair to put a specific sequence in the DNA.
b. Cre/lox system: exogenous recombinase recognizes unique DNA and will
break down the existing DNA with this specific sequence.
c. CRISPR-Cas: a genetic tool to insert a specific sequence at a specific place
in the genome.
Brain-imaging techniques:
- Computerized tomography (CT): uses a narrow X-ray beam and a row of sensitive
detectors on opposite sides of the head. CT scans can distinguish the gray and
white matter. Brain lesions can be recognized with CT if they are not visible with
standard X-ray methods.
Magnetic resonance imaging (MRI): uses nuclei of atoms and a magnetic field to
turn the nuclei to three different directions. Almost all MRI scanners use detectors
that are tuned to the frequency of hydrogen nuclei, which creates imiages based
on the distribution of water in different tissues.
- Positron emission tomography (PET): unstable positron-emitting isotopes are
incorporated into different reagent and injected into the bloodstream. This can be
used to visualize activity-dependent changes in bloodflow, tissue metabolism of
biochemical activity.
- Singe-photon emission computerized tomography (SPECT): Similar to PET by
injecting a radialabeled compound and it is visualized by a gamma camera moving
rapidly around the head.
- Functional-magnetic tomography (fMRI): relies on the fact that hemoglobin slightly
distorts the magnetic resonance properties of hydrogen nuclei. When a brain area
is active, it uses more oxygen and is thus visible. The changes that are visibleare
blood oxygen level-dependent changes (BOLD).
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