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Samenvatting - Biologische Grondslagen: Cognitie
1.1.1 Structure and Function of the Neuron
What are the three components of neurons?1. Cell Body (Soma)
What contains the cell body and what is it involved in?The cell body contains the nucleus (and other organelles), which contains the genetic code which is involved in protein synthesis of certain neurotransmitters.
What is the function of dendrites and axons?They enable communication with other neurons. Dendrites receive information and the axon sends information.
Each neuron has many dendrites, but only a single axon.
How does communication by an axon work?The terminal of an axon flattens out into a disc-shaped structure. It is here that chemical signals enable communication between neurons via a small gap (synapse). The two neurons forming that synapse are reffered to as presynaptic (before the synapse) and postsynaptic (after the synapse), reflecting the direction of information flow.
What is an action potential and how does it works?When a presynaptic neuron is active, an electrical current (action potential) is propogated down the length of the axon. When the action potential reaches the axon terminal, chemicals (neurotransmitters) are released into the synaptic cleft.
What is a synaptic potential and how does it work?Neurotransmitters bind to receptors on the dendrites or cell body of the postsynaptic neuron and create a synaptic potential, which is conducted passively (without creating an action potential).
It is important to note that each postsynaptic neuron sums together many synaptic potentials, which are generated at many different and distant dedritic sites.
What is the range of the two potentials?Passive conduction tends to be short range because the electrical signal is impeded by the resistance of the surrounding matter.
Active conduction enables long-range signalingsignaling between neurons by the propogation of action potentials.
What is the sequence of events by producing an action potential?1. If a passive current of sufficient strenght flows across the axon membrane, this begins to open the voltage-gated Na+ channels.
2. When the channel is opened, then Na+ may enter the cell and the negative potential normally found on the inside is reduces (depolarize). At about -50 mV, the cell membrane becomes completely permeable and the charge of the inside of the cell momentarily reverses. This suddem depolarization and subsequent repolarization in electrical charge across the membrane is the action potential.
3. The negative potential of the cell is restored via the outward flow of K+ trough voltage-gated K+ channels and closing of the voltage-gated Na+ channels
4. There is a brief period in which hyperpolarization occurs (the inside is more negative than at rest). This makes it more difficult for the axon to depolarize straight away and prevents the action potential from traveling backwards.
What is the function of myelin?Myelin is a fatty substance that is deposited around the axon of some cells (especially those who carry motor signals). It blocks the normal Na+/K+ transfer and so the action potential jumps, via passive conduction, down the length of an axon at the points at which the myelin is absent (called 'nodes of Ranvier').
Destruction of myelin is found in multiple sclerosis.
How is a synaptic potential created?The electrical signal initiates a sequence of events leaing to the release of neurotransmitters into the synaptic cleft. Protein receptors in the membrane of the postsynaptic neurons bind to the neurotransmitters. Many of the receptors are transmitter-gated ion channels. This sets up a localized flow of Na+, K+ or Cl-, which creates the synaptic potential.
What is GABA?Neurons that have an inhibitory effect on the postsynaptic neuron. This can be achieved by making the inside of the neuron more negative than normal and hence harder to depolarize by opening transmitter-gated Cl- channels.
How do neurons code information?The amplitude of an action potential does not vary, but the number of action potentials propogated per second varies along a continuum. This rate of responding ('spiking rate') relates to the informational code carried by that neuron.
1.1.2 The Gross Organization of the Brain
What is white/gray matter and its location?Gray matter consists of neuronal cell bodies and its located at the cerebral cortex and the subcortex.
White matter consists of axons and support cells ('glia'). Its located beneath the cerebral cortex.
White matter tracts may project between different cortical regions within the same hemisphere (association tracts), may project between different cortical regions in different hemispheres (commmissures: corpus collosum) or may project between cortical and subcortical structures (projection tracts).
What are ventricles?Hollow chambers filled with cerebrospinal fluid (CSF). The CSF carries waste metabolites, transfers some messenger signals and provides a preotective cushion for the brain.
What are the terms of
referencing locationsby the brain?1. Anteriorand posteriorrefer to directions toward the front and the back of the brain.
2. Superior/dorsal and inferior/
ventralrefer to directions towards the top and the bottom of the brain.
3. Lateral and
medialrefer to directions toward the outer surface and the center of the brain.
What are the two types of sectioning the brain?1. Coronal cross-section refers to a slice in the vertical plane through both hemispheres. A saggital section refers to a slice in the vertical plane going through one of the hemisphers. When this lies between the hemispheres it is called a midline or medial section.
2. An axial section is taken in the horizontal plane.
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2. Direct experience
4. Cultural information