Module 5: Neurons Thursday, September 14, 2023 8:49 PM The Structure of the Neuron Neurons: nerve cells are the basic elements of the nervous system • 100 billion in the human brain and 1 trillion neurons throughout the body are involved in the control of behaviour • Can communicate with other cells and transmit information across relatively long distances Where Neurons Meet: Bridging the Gap Synapse: chemical connection that bridges the gap between two neurons. • Space between two neurons. The nucleus incorporates the hereditary material that determines how a cell will function NOTE: messages travelling within are transmitted in electrical form, whereas messages travelling between neurons travel via chemical means Neurons are physically held in place by glial cells. Glial cells provide nourishment to neurons, insulate them, help repair damage, and generally support neural functioning. Dendrites: a cluster of fibers (located at the end of the cell body) • Receives messages from other neurons Axon: long, slim, tube-like extension. Carries messages received by the dendrites to other neurons Terminal buttons: at the end of the axon; sends messages to other neurons Impulses: are electrical messages. Generally moves across neurons in one direction only Dendrites -> cell body -> axon • Dendrites detect • Axon carry away from the cell body Myelin Sheath: insulates the axon; a protective coat of fat and protein. • Speeds up thinking; allows electrical impulses to move more quicky down the neuron How Neuron Fire All-or-none law: They are either on or off. The intensity of the firing does not vary. Resting state: the neuron has a negative electrical charge of about –70 millivolts (one one-thousandth of a volt). • IS caused when there are more negatively charged ions within the neuron than outside (ion: an atom that is electrically charged). When the positive charge reaches a critical level, the "trigger" is pulled. The action potential: electrical impulse that travels along the axon. Changes the charge of ions from negative to positive... Absolute refractory period: resting states after a neuron fires. It is a cooldown Relative refractory period: after cooldown the neuron can fire but a stronger stimulus is needed. The intensity of a stimulus determines how much of a neuron's potential firing rate is reached. • a bright light or loud sound Mirror Neurons: many of the same neurons fire whether you are simply observing an action or acting yourself Neurotransmitters: the chemical courier that the terminal button releases. • Are brain chemicals that carry messages across the synapse to the dendrites of receiving neurons. Excitatory messages: make it more likely that a receiving neuron will fire and an action potential will travel down its axon Inhibitory messages: they provide chemical information that makes it less likely that the receiving neuron will fire. Reuptake: chemical recycling; terminal button reabsorbs the NTs SSRI or Selective serotonin reuptake inhibitors: allows certain NTs to remain, increasing the availability of serotonin. (antidepressants) Neurotransmitters: Multitalented Chemical Couriers NTs are an important link between the nervous system and behaviour Endogenous: substances our body creates Exogenous: are substances created outside of our bodies and then introduced to our bodies Dopamine pathways: neurons that use dopamine as their NTs Dopamine stabilizer drugs can do 2 things 1. Reduce activity in the dopamine pathways when dopamine levels are too high 2. Mildly increase activity in the dopamine pathways when dopamine level are too low. Endorphins: another class of NTS, a family of chemicals produced by the brain that are similar in structure to painkillers. (our body's morphine) • Production of endorphins reflect the brain's effort to deal with pain and to elevate mood Opiate drugs: drugs thar relieve pain and cause feelings of euphoria (e.g., morphine. Heroin. Opium) • Activate receptor sites powerfully (that's why it leads to addiction) Serotonin: another major NTs, it is associated with regulation of sleep, eating, mood and pain NTs can be blocked from their receptor sites, they can be mimicked, or their reuptake can be blocked All NTs function based on the same basic principles of release, reception, and reuptake More NTs: • Acetylcholine: found throughout our nervous system. It transmits messages relating to skeletal muscles, and involved in memory capabilities. A lack of it may be related to Alzheimer's disease • Glutamate: plays a role in memory. In the process where specific biochemical changes at particular synapses. • Gamma-amino butyric acid (GABA): found in the brain and spinal cord, is the nervous system's primary inhibitory NT. Moderates a variety of behaviors, ranging from eating to aggression. Chapter 2 Page 1 Indigenous Perspectives Intergenerational trauma: phenomenon of trauma being transmitted from one generation to the next Attachment: the positive emotional bond that develops between a child and a particular individual Post-traumatic stress disorder (PTSD): phenomenon which victims of major catastrophes or stressors feel long-lasting effects that may in include reexperiencing the event in vivid flashbacks or dreams The Developing Brain Myelination: the development of myelin on the axon, allows the neuron to send messages more rapidly • A huge rush occurs from the age of 6 months to one year. It is referred to naming explosion Pruning: The process of weakening or removing synaptic connections between neurons in order to increase the efficiency of a system of neural pathways within the brain. • Makes the brain more efficient; removes/weakening unnecessary branches while also strengthening some of our synaptic connections • Visual happens around 4 months • Language happens at the age of three
