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Chapter 4

Chapter 4.docx

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Lawrence Murphy

Chapter 4- the brain: source of mind and self The central nervous system: o Central nervous system (CNS) – receives, processes, interprets, and stores incoming sensory information (sends out messages to muscles, glands, organs) o Peripheral nervous system (PNS)- handles input and output from the CNS (all portions of nervous system outside brain and spinal cord) o Spinal cord- bridge between brain and parts o body below neck, spinal nerves protected by spinal column (enables spinal reflexes) Peripheral Nervous System o Contains two subdivisions (messages carried through sensory and motor nerves) o Somatic nervous system nerves connected to sensory receptors and skeletal muscles o Autonomic nervous system regulates functioning of blood vessels, glands, internal organs- contains sympathetic (mobilize- increased heart rate etc.) and parasympathetic (conserve- decreased heart rate etc.) division Communication in the nervous system o Nervous system made up of… ‒ Neurons: cells that conduct electrochemical signals; basic unit of nervous system ‒ Glia: cells that support, nurture and insulate neurons, remove debris when neurons die, enhance formation and maintenance of neural connections, and modify neural function Structure of the neuron o Approximately 100 billion neurons in the brain Dendrites Branch like fibres that receive information from other neurons and transmit towards cell body Cell body Keeps neuron alive and plays key role in determining whether neuron will “fire” Axon Extending fibre that conducts impulse away from cell body and transmits to other cells Branches at end called axon terminals May be collected in bundles called nerves Myelin sheath Many axons insulated by surrounding layer of fatty material In CNS, this is made up of glial cells Constrictions in covering nodes divide myelin into segments Purpose to speed conduction of neural impulses and prevent interference from neighboring signals Neutron in the news o Neurogenesis: production of new neurons from immature stem cells o Stem cells : o Immature cells that renew themselves and have potential to develop into mature cells o Stem cells from early embryos can develop into any cell type o Stem cell research o Embryonic stem cells can differentiate into any type of cell; adult stem cells limited o Use is controversial and surrounded by ethical debates regarding extraction* o Most promising in developing treatments fro cancer, blood, organ, and brain disorders (ex. Parkinson’s) o Canadian researchers have had some success with adult stem cells transforming to brain cells How neurons communicate o No direct contact between neurons o Communicate through synapse- includes axon terminal, synaptic cleft, and receptor sites in membrane of receiving cell o Communication occurs through electrical and chemical signals o Stimulation causes change in charge between inside and outside of cell o Inflow of sodium ions causes and action potential o Synaptic vesicles release chemicals called neurotransmitters o Neurotransmitters bind to receptor sites on receiving neuron and causes changes in cell membrane o Excitatory changes: voltage shift in positive direction (increases probability of receiving neuron firing) o Inhibitory changes: a voltage shift in negative direction (decreases probability of receiving neuron firing) Brain plasticity o Plasticity: o Brains ability to change and adapt in response to experience (reorganizing or growing new neural connections) o Behavioral deficits that occur as result of brain damage may be lessened by enriching environments people live in Chemical messengers o Neurotransmitters o Chemical substance that is released by transmitting neuron at synapse and that alters activity of a receiving neuron o Neurotransmitters and their different effects: Serotonin sleep, appetite, sensry perception, temperature regulation, pain suppression, mood dopamine voluntary movement, learning, memory, emotion, pleasure or reward, response to novelty acetylcholine muscle action, cognitive functioning, memory and emotion norepinephrine Increased heart rate, slowed intestinal activity during stress, learning, memory, dreaming, waking, emotion GABA Major inhibitory neurotransmitter Glutamate Major excitatory neurotransmitter in brain Endorphins Chemical substances in nervous sytem that are similar in structure and action to opiates Involved in pain reduction, pleasure and memory Technically known as endogenous opioid Hormones Chemical substances, secreted by organs called endocrine glands that affect functioning of other organs Regulate growth, metabolism, sexual development and behavior etc. Major hormones: ‒ melatonin- regulate daily biological rhythms, sleep ‒ Oxytocin- childbirth contractions, milk ejection ‒ Adrenal hormones- emotion, stress, epinephrine ‒ Sex hormones- androgens and estrogens Mapping the Brain o Ways scientists study the brain: ‒ Patients with brain damage ‒ Lesion method- involves damaging or removing section of brain i
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