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PSYB55: Introduction to Cognitive Neuroscience Lecture 2
Enjoy these class notes from University of Toronto Scarborough in the course PSYB55H3: Introduction to Cognitive Neuroscience from lectures 1-11.
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PSYB55- Lecture 2Neurons: Basic signalling units that transmit information throughout the nervous system
Glial cells: nonneural cells that have various functions in the nervous system
Dendrites: branching extensions of the neuron that receive inputs from other neurons
Axon: Output side of the neuron. Electrical signals travel along the length of the axon to the axon
terminals, where the neuron transmits the signal to other neurons.
Wrapped in a fatty substance called myelin, which protects the
strength of the signal being transmitted.
Synapse: Specialized structure where transmission occurs.
Two neurons come to close contact so chemical or electrical
signals can be passed from one cell to the next.
Node of Ranvier: gaps in the myelin
Most neurons are both presynaptic and postsynaptic.
Presynaptic: axon makes connection to other neurons
Postsynaptic: Other neurons make a connection onto dendrites.
Membrane Potential
Resting Membrane Potential: neuron’s resting state voltage. (-70 mV)
Inside of neuron is more negatively charged than the outside
Ion Channels: proteins with pores through their centers. Allows certain ions to flow down their
concentration gradients.
Selective permeability
More permeable to potassium ions than sodium ions.
Ion Pumps: use energy to actively transport ion across the membrane against their concentration
gradients. (Low Conc. to High Conc.)
Pumps sodium ions out of the cell and potassium ions into the cell.
Action Potential
The active or regenerative electrical signal required for synaptic communication.
Regenerates due to voltage-gated ion channels
1. Threshold potential is reached. Sodium channels open and flows into neuron
2. Neurons gets further depolarized, making sodium ions flow into the neuron. Potassium
ions flow out of the neuron down its conc. gradient.
, 3. Sodium ion channels close but Potassium ions continues to flow out the cell making the
neuron repolarize.
4. The neuron becomes more negative making it hyperpolarize, ultimately causing
potassium channels to close.
5. The membrane potential gradually returns to resting state during its refractory period.
Neurotransmitters and Synaptic Transmission:
Two types of transmission: Electrical and Chemical
Chemical transmission results the results in the release of neurotransmitters from the pre
synaptic neuron and the binding of those transmitters on the postsynaptic neuron.
o Can cause excitatory or inhibitory postsynaptic potentials
o EPSPs- ACh, catecholamines, glutamate, histamine, serotonin, some
neuropeptides.
o IPSPs-GABA, glycine, some peptides.
Neurotransmitters must be removed from the receptor after binding.
o This can be done by (a) active reuptake back into the presynaptic terminal
o (b) enzymatic breakdown of the transmitter in the synaptic cleft
o (c) diffusion of the neurotransmitter away from the region of the synapse.
Electrical synapses pass current directly from one neuron (presynaptic) to another neuron
(postsynaptic) via specialized channels in gap junctions that connect the cyto plasm of
one cell to the other.
Dopamine
Site(s) of production:
o Substantia nigra
Ventral tegmental area (VTA)
Select links to cognition/behavior:
o Higher-order cognitive functions
o Voluntary movement
o Reward/reinforcement learning
Dysfunctional levels associated with:
o Parkinson’s disease
o Psychotic thoughts/behavior Addiction
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