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PSY 105
Kristin Vickers

How do scientists study the nervous system? 1. Examining autopsy tissue 2. Testing the behaviour of patients with damage to certain parts of the brain 3. Recording brain activity, or brain waves from the surface of the scalp 4. Animal studies Neuroimaging Techniques that allows the study of brain activity and structure by obtaining visual images in awake humans There are several methods used in neuroimaging: - Positron emission tomography (PET) small dose of radiation is injected and the radiation is used to scan the person’s brain - Functional magnetic resonance imaging (fMRI) allows the detection changes in blood flow, a presumed indicator of changes in the activity of neurons - Computerized axial tomography (CAT) shows the structure of the brain - Magnetic resonance imaging (MRI) shows the structure of the brain, however shows a more clearer resolution that CAT How does the nervous system work? Through the use of neuron and glia Neuron: a nerve cell Glia: the cell that, in addition to neurons, makes up the nervous system Neuron - human brain consists of 100 billion neurons - neurons have cell body filled with cytoplasm that contains a nucleus - contains organelles that enable the cell to make proteins and other molecues, produce energy and permits the breakdown and elimination of toxins - the neurons are different from other cells, they have specialized structures called dendrites and axons which helps with the communication of neurons The structure of the Neuron - Cell Body (C) contains nucleus, which provides energy for the neuron - Dendrites (B) The part of neurons that collect input from other neurons. - Axon (D) The part of the neuron that carries information away from the cell body toward other neurons - Axon terminal (E) transmit signals to the dendrites The end of a neuron’s axon, from which neurotransmitters are released Some axons are covered with myelin sheath. - Myelin Sheath (F) A substance that speeds up the firing of the neuron - Nodes of Ranvier (A) The small gaps on the neuron that have no myelin covering There are also many different kinds of neurons: Sensory neurons: in the skin; muscle responds to pressure, temperature, pain Motor neurons: stimulate our many muscle cells into action Interneurons: connects both sensory neuron and motor neuron In addition to neurons, the nervous system contains a large number of non-neuronal cells called, glia. Glia: the cells that, in addition to neurons, make up the nervous system. Glia buffers the neurons from the rest of the body, control the nutrient supply to the neurons, and destroy and remove diseased and dead neurons. The types of Glia Astrocytes: - Create blood-brain barrier, influences communication between neurons, and helps heal brain damage - One type of astrocytes is the stem cell, which creates new neurons Oligodendroglia: - Provide myelin to speed up transmission of neurons Ependymal cells: Create and secrete cerebrospinal fluid (CSF) Microglia: - Clean up dead cells and prevents infection in the brain How do Neurons work? - Neurons send messages to one another via electrochemical actions. (note: Neurons are not in direct contact with one another) - A sudden change in the electrical charge of a neuron’s axon causes it to release chemical that can be received by other neurons, therefore passing an electrical signal along from one neuron to the next Neurons communicate via, synaptic transmission between neurons… Resting potential - When a neuron is at rest - It is negatively charged inside and positively charged outside. This resting charge is maintained through the actions of sodium-potassium pumps. Action potential - Reaches end of axon & neurotransmitter is released into synapse, collected at receptors of receiving neuron. - Pores in the neuron (ion channels) open to let the positive charge come in and the negative charge go out. This shift in electrical charge triggers the axon terminals to release neurotransmitters. - An action potential triggers the release of neurotransmitters o Neurotransmitters are chemicals that help neighbouring neurons talk to each other. o These chemicals float from the synaptic vessel of one neuron and are taken up by the neurotransmitter receptors in a neighboring neuron. o Synapse—the small space between neurons - Plasticity—Repeated release of neurotransmitters can cause permanent change to the neurons - Either a neuron is sufficiently stimulated to start an action potential (all) or it is not (nothing). - Refractory period: After firing, a neuron can’t fire for 1000th of a second. - Absolute refractory period: a short time after an action potential, during which a neuron is completely unable to fire again - Relative refractory period: just after the absolute refractory period, during which a neuron can only fi
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