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Lecture 3

PSYC 2P35 Lecture Notes - Lecture 3: Grou, Macrophage, Glycogen

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Dawn Good

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PSYC 2P35 Lecture 3: Intro to the Neuron
-plasma membrane is important for resting potential of a neuron
-neurons generate and send electro chemical signals
-they can influence other cells
-they use a very small electrical signal
-current of a neuron = 70 microvolts
-the current of your home = 100 volts
-connections between neurons are dependent on programming experience after birth and
sensitive periods
-connections continue to be modified to greater or lesser degrees depending on the
structure/placement throughout our lives
Parts of a Neuron
Soma= cell body; contains the workings of the cell (nucleus etc)
Dendrite= receives neural messages via postsynaptic membrane
Dendritic spine= nodule on dendrite also has postsynaptic membrane
Axon= sends message to other neuron (.5-20 u diameter; few u to 1m in length)
Axon Hillock= summation of electrical message
Collaterals=branching of the axon; permits one axon to communicate with many synapses
Terminal Buttons= hold the vesicles for TS release across the presynaptic membrane
Myelin Sheath= insulation on many neurons; improves efficiency of signal
Nodes of Ranvier= gap between the sheaths; permits regeneration of the action potential
Synapse= 3 components: presynaptic membrane, synaptic gap 20-40mm, post synaptic
Microtubules help things make neurotransmitters; maintains structures of the cell (as a
Types of Neurons
-Multipolar neurons: a neuron with one axon and many dendrites
Pyramidal; Stellar; Purkinje
Stellar: found throughout the cerebral cortex as well as the cerebellum and spinal cord;
excitatory and inhibitory
Pyramidal: found throughout cortex, esp. prefrontal cortex as well as subcortical areas
(hippocampus, amygdala) and corticospinal tract; primarily excitatory; implicated in
(clustered, goes in groups)
Purkinje: (bunny ears) the largest of CNS neurons; found in the cerebellum; GABAergic
(specialized inhibitory transmitter)
-Bipolar neurons: a neuron with one axon and one dendrite attached to its soma
-Unipolar/Pseudounipolar: a neuron with one axon attached to its soma; the axon extends from
the soma and or divides with one branch receiving sensory information and the other sending
the information into the CNS
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Other means of classification is by function:
1. Sensory neuron= receptor neurons; sensitive to certain kinds of stimulation (light touch)
2. Motor neuron= conducts impulses to muscles and glands from the spinal cord
3. Interneuron= connections to other local neurons (has nucleus etc all in one space)
4. Projection neuron= connections to distal neurons
Efferent vs Afferent
-Efferent (exit) axons: carries info away from a structure
-Afferent (approach) axons: carries info to a structure
-Interneurons/Intrinsic neurons: dendrites and axon remain within a single structure
-it all depends on the point of view. An axon from A to B is an EFFERENT axon and from A and
an AFFERENT axon to B
Glial Cells
-neurons are supported functionally and structurally both in the CNS and PNS
-ratio of glia:neurons = 10:1 but their size is about 1/10th of a neuron; so occupy as much space
in the brain
-neurons in the CNS are those in the PNS
-glial cells in the CNS are not those in PNS
Glial Cells and White Matter
-Neurons: gray matter (ex cortex); the building blocks of thought, computation, memories,
communication etc
-Glial cells: white matter; functionally support neurons; the pathways for communication
-White matter (have same amount as animals)
Einstein: neuron density was no different but had a lot more and size of glial cells in the Parietal
lobe the area responsible for visuo-spatial, relational info; A smaller gray:white matter ratio may
indicate more efficient energy use and faster processing
White matter density is correlated with:
-learning: humans who have greater experience (ex music practice) have more white matter in
expected areas
-IQ: children who have experienced severe neglect have less white matter; rats in enriched
environments have proportionally more white matter
-Coherence of thought: disordered thought (schizophrenia) is associated with less white matter
-Environmental toxins: less/disrupted white matter is associated with fetal smoke exposure and
viral exposure
Glial Cells
-Support: structural- securing the synaptic gap; securing neurons
functional- enhance nutrient supply (dilates blood vessels during heightened activity)
-Transport: astrocyctes take up glucose and store it in either as glycogen for later use or break it
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