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Lecture 7

PSYC20008 Lecture Notes - Fall 2017 Lecture 7 - Apoptosis, White matter, Dentate gyrus

6 pages94 viewsFall 2017

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Katherine Johnson

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The adult human brain
o Definitions
Central nervous system (CNS) brain + spinal cord
Peripheral nervous system (PNS) nerves attached to the CNS that lie outside of the CNS
Soma cell body of a neuron (contains the nucleus)
Dendrite a branched, tree-like structure attached to the soma; receives information from
terminals of other neurons
Synapse junction between the terminal of the axon and the membrane of another neuron
Neural junctions through which cells communicate to each other
Axon long thin cylindrical structure that conveys information from the soma of a neuron to
its terminal
Multipolar neuron neuron with one axon and many dendrites attached to its soma
Neurotransmitter chemical released by the nerve terminal that has an excitatory or
inhibitory effect on another neuron
o Human brain makes up about 2/3 of the neuronal mass of the body and contains almost ¾ of all
our synapses
o Enteric nervous system (gut) consists of sheaths of neurons embedded in the walls of the gut
Contains ~100 million neurons (more than the spinal cord or peripheral nervous system)
The brain outsources the digestion process to this nervous system
90% of the fibres in the vagus nerve carry information from the gut to the brain
Uses more than 30 neurotransmitters
95% of the body’s serotonin is found in the bowels
o Brain growth
At birth weighs 25% of adult weight
Age 2 weighs 75% of adult weight
Massive development of the brain from birth to 2 years of age
7th prenatal month to 1st birthday brain increases in weight by ~1.7g/day
Brain growth spurt last 3 prenatal months and first 2 years after birth
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Neurons and glia
o Neurons basic unit of the brain and CNS
3 basic types sensory neurons, motor neurons and interneurons
All neurons have cell body, dendrites and axon
Cell body (aka soma) contains all the information needed to keep the cell functioning
Dendrites fibres that receive information from other cells and conduct that information
towards the cell body in the form of electrical impulses
Axon fibre (range from a few micrometers to over a meter in length) that conducts electrical
signals away from the cell body to connections with other neurons
Receives and transmits neural impulses across the synapses
Product of the neural tube of the developing embryo
o Neurons migrate along pathways laid down by a network of guiding cells to form the major parts
of the brain
o End of second trimester of pregnancy vast majority of the neurons a person will ever have would
have been formed by then
o Formations of new neurons occur in the hippocampus (responsible for learning and memory) and
new neurons are formed throughout life
o Neuron specialisation
Neurons assume specialised functions depending on where they migrate
Pluripotency any neuron has the potential to serve any neural purpose (neurons can be
transplanted from one area of the body to another and they can perform the same function)
o Glial cells perform a variety of critical functions (esp. communication within the brain)
Influence the formation and strengthening of synapses
Produce myelin which helps neurons conduct electrical messages along the neural network
Schizophrenia & bipolar disorder may have a defect in a gene that regulates the production
of myelin
Five key types of glial cells Astrocyte, Oligodendrocyte, Schwann cells, Microglia & NG2 cells
Most common of the glial cells
Mop up excess neurotransmitters emitted from synapses
Feed neurons by supplying nutrients and neurotransmitter precursors
Control where and when neurons will make new synapses
Wrap tips around the axons of neurons and extrudes myelin, creating sheaths that help
speed conduction of electrical activity along the axon
Myelin “white matter’ of the brain
Schwann cells
Form a layer around the axon, helping conduct electrical impulses
The only glial cells found in the PNS, therefore they also act like astrocytes (eg. clean up
extra neurotransmitters)
Microglia serve as the immune system in the brain
NG2+ cells precursor cells to oligodendrocytes, astrocytes and neurons
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