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THE NERVOUS SYSTEMExploring a Few Chords

Ruth DuBois, BScN, MA

2018

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FUNCTIONS OF THE NERVOUS SYSTEM

u Senses changes inside and outside body

u Integrates incoming information

u Effects responses (i.e. muscles and glands)

u Works with the endocrine system

u Highly complex, rapid electrical impulses

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CENTRAL NERVOUS SYSTEM

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PERIPHERAL NERVOUS SYSTEM

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AUTONOMIC NERVOUS SYSTEMSYMPATHETIC

ü “FIGHT OR FLIGHT”

ü Increased heart & blood pressure

ü Dilation of respiratory passages

ü Stimulates epinephrine release

ü Sweat glands stimulated

ü Dilated pupils

ü Liver releases glucose (from glycogen)

ü Inhibition of digestion, urination, and defecation (sphincters tighten)

ü Causes ejaculation of semen

PARASYMPATHETIC

ü “MAINTENANCE, HOUSEKEEPING”

ü Stimulates digestive, urinary functions

ü Slows heart rate

ü Constricts respiratory passages

ü Constricts pupil, bulges lens of eye for close vision

ü Causes erection of the penis

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SUPPORTING CELLS

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NEURON§ Over 100 billion neurons in the brain and spinal cord; represents over 965 km. in length

§ Excitable: Receives stimuli and transmits impulses by electrical and chemical means, up to 100 meters/second

§ Neurons transmit sensory information towards the CNS, and motor information away from the CNS to effectors (muscle, gland)

§ Transmission: unidirectional, all-or-none action potentials

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The SYNAPSE

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NEUROTRANSMITTERS

u Neurotransmitters act to carry a message from the axonal end of a neuron across the synapse to another neuron, muscle cell, or gland

u Response of the post-synaptic cell is either stimulation or inhibition of post-synaptic transmission of impulse

EXAMPLES:

u Norepinephrine (adrenaline)

u Acetylcholine

u Dopamine

u Serotonin

u GABA (gamma-aminobutyric acid)

u Endorphins

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u https://www.youtube.com/watch?v=GIGqp6_PG6k

Dance of the Neurons

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‘NEW’ UNDERSTANDING OF THE BRAIN

u NEUROPLASTICITY vs. a locationist view of the brain

u ‘The ability of the brain to form and reorganize synaptic connections, especially in response to learning or experience or following injury’

u Lifelong capacity though plasticity is most highly reflected during early development of the brain

u Debate surrounds whether new neurons can be ‘born’ and integrated into the hippocampus of human brains after infancy

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Brain Mapping

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THE BRAIN

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THE BRAIN

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REFLEX ARCS

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Normal Aging of the Nervous System

u Gradual decrease in sensory neurons

u Decreased position sense affecting balance and coordination

u Reduced sensations of thirst, objects in the throat, urine in the bladder, and feces in the rectum

u General gradual decline in # motor neurons, leads to reduced muscle mass (age 60+)

u Slowed reflexes

u Slight decrease in short term memory after age 70+

u Long term memory may even improve

u Sleep changesThis Photo by Unknown Author is licensed under CC BY-SA

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PAIN

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Perception of Acute Pain—A Warning

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Gate Control Theory Melzack & Wall

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COMPARISON: ACUTE AND CHRONIC PAIN

u Purposeful, warning sign of danger

u Associated with muscle spasm and sympathetic nervous system response

u Usually a NORMAL response to inflammation, tissue injury, disease process

u Self-limited until healing, or resolution of the disease

u If treated effectively, pain goes away in days or weeks as healing proceeds

u No biologic purpose

u Disease of ‘pain’

u May result from inadequate relief of acute pain, influenced by physical and psychological factors

u No end-point

u Elicits on-going stress response

u Treatment must be multi-modal, involving multi-disciplinary team

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Acute and Chronic Pain Presentations

Face of a Person in Acute Pain

Face of a Person With Chronic Pain

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Understanding Pain as a Disease

u https://www.ted.com/talks/elliot_krane_the_mystery_of_chronic_pain/discussion?ga_source=embed&ga_medium=embed&ga_campaign=embedT

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What importance might the information provided by Dr. Elliot

Krane have for you?

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LEARNING IN ALMONTE: THE NERVOUS SYSTEM

RECOMMENDED READING/VIEWING

BOOKS YOU MIGHT REALLY LIKE

u Doidge, N. (2007). The Brain That Changes Itself: Stories of Personal Triumph from the Frontiers of Brain Science

u Doidge,N. (2016). The Brain’s Way of Healing: Remarkable Discoveries and Recoveries from the Frontiers of Neuroplasticity

Internet Programs

u https://ed.ted.com/lessons/the-mystery-of-chronic-pain-elliot-krane

u http://www.cbc.ca/natureofthings/episodes/the-brains-way-of-healing