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The Brain- Source of Mind and Self.docx

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Lawrence Murphy

The Brain: Source of Mind and Self The Nervous System: A Basic Blueprint  2 main parts: o Central nervous system: receives, processes, interprets & stores incoming sensory information  Sends out messages to muscles, glands, organs  Two components: brain & spinal cord  Spinal cord: a bridge b/t the brain and parts of the body below the neck  Spinal nerves protected by the spinal column  Enables spinal reflexes o Peripheral nervous system: handles input & output from the CNS  Moving & sensing things  Contains 2 subdivisions (messages carried through sensory & motor nerves):  Somatic nervous system: nerves connected to sensory receptors and skeletal muscles  Autonomic nervous system: regulates functioning of blood vessels, glands & internal organs o Sympathetic Division: engaged when something shocks/ frightens you  to conserve o Parasympathetic Division: engaged to settle things down  to mobilize Communication in the Nervous System  Nervous system made up of o Neurons: cells that conduct electrochemical signals; basic unit of the nervous system  Structure: approx. 100 billion in brain, varies in shape & size  Dendrites: branch-like fibre that receives information from other neurons & transmit towards cell body  Cell body: keeps neuron alive & plays key role in determining whether the neuron will “fire”  Axon: extending fibre that conducts impulse away from cell body and transmits to other cells o Branches at end called axon terminals o May be collected in bundles called nerves  The Myelin Sheath o Many axons are insulated by surrounding layer of fatty material called myelin sheath  In the CNS, this is made up of glial cells  Constrictions in covering (nodes) divide myelin into segments  Purpose to speed conduction of neural impulses & prevent interference from neighbouring signals o Glia: cells that support, nurture, and insulate neurons, remove debris when neurons die, enhance the formation & maintenance of neural connections, and modify neural functioning Neurons in the News  Neurogenesis: production of new neurons from immature stem cells  Stem cells o Immature cells that renew themselves & have the potential to develop into mature cells o Stem cells from early embryos can develop into any cell type Stem-Cell Research  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 for cancer, blood, organ, and brain disorders o Canadian researchers had some success with adult stem cells transforming to brain cells How Neurons Communicate  No direct contact b/t neurons  Communicate through the synapse o Includes the axon terminal, synaptic cleft, and receptor sites in the membrane of the receiving cell  Communication occurs through electrical and chemical signals o Stimulation causes change in charge b/t inside and outside of cell o Inflow of sodium ions causes an action potential o Synaptic vesicles release chemicals called neurotransmitters  Neurotransmitters bind to receptor sites on receiving neuron and causes changes in the cell membrane o Excitatory change: a voltage shift in a (+) direction  Increases probability of receiving neuron firing o Inhibitory change: a voltage shift in a (-) direction  Decreases probability of receiving neuron firing Brain Plasticity  Plasticity: the brain’s ability to change and adapt in response to experience (eg. Reorganizing or growing new neural connections) o Behavioural deficits that occur as a result of brain damage may be lessened by enriching environments people live in Chemical Messengers  Neurotransmitters o A chemical substance that is released by a transmitting neuron at the synapse and that alters the activity of a receiving neutron o Serotonin: sleep, appetite, sensory perception, temperature regulation, pain suppression, mood o Dopamine: voluntary movement, learning, memory, emotion, pleasure or reward, response to novelty o Acetylcholine: muscle action, cognitive functioning, memory, emotion o Endorphins: chemical substances in the nervous system that are similar in structure and action to opiates  Involved in pain reduction, pleasure and memory o Hormones: chemical substances, secreted by organs called endocrine glands, that affect the functioning of other organs  Regulate growth, metabolism, sexual development & behaviour, and other functions  Major hormones  Melatonin: regulate daily biological rhythms, sleep  Oxytocin: childbirth contractions, milk ejection  Adrenal hormones: emotion, stress, epinephrine  Sex hormones: androgens & estrogens o Norepinephrine: increased heart rate, slowed intestinal activity during stress, learning, memory, dreaming, waking, emotion o GABA: major inhibitory neurotransmitter o Glutamate: major excitatory neurotransmitter in brain Mapping the Brain  Many ways scientists can study the brain: o Patients with brain damage  Lesion method: involves damaging o
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