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The Human Nervous System

Explore the complexities of the human nervous system, including the Central Nervous System, Peripheral Nervous System, and autonomic divisions. Learn about sensory receptors, reflex arcs, and different types of reflexes, from intrinsic to acquired, with a focus on spinal reflexes and Babinski's sign.

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The Human Nervous System

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  1. The Human Nervous System Central Nervous System (CNS) Peripheral Nervous System (PNS) Brain Spinal Cord Sensory (afferent) Motor (efferent) Autonomic Nervous System (ANS) (involuntary) Somatic Nervous System (voluntary) Sympathetic Nervous System Parasympathetic Nervous System

  2. Sympathetic and Parasympathetic Divisions • Sympathetic- “fight-or-flight”- rapid heart rate; deep breathing; dry mouth; cold, sweaty skin; dilated pupils • During vigorous physical activity- constricts blood vessels, bronchioles dilate, liver releases more glucose to blood, all nonessential activities are slowed • Parasympathetic- “resting & digesting”- keeps body E use as low as possible as it directs vital activities (digestion, elimination of wastes, etc) • Blood pressure & heart rate regulated at low normal levels while gastrointestinal tract actively digests

  3. Sensory Receptors • Specialized to respond to changes in environment (stimuli) • Mechanoreceptors- touch, pressure, vibration, stretch • Thermoreceptors- temp • Photoreceptors- light E • Chemoreceptors- chemicals in solution • Nociceptors- pain receptors- respond to potentially damaging stimuli

  4. Reflex Arc • Highly specific neural pathways- 5 components • 1) Receptor- site of stimulus action • 2) Sensory neuron- transmits afferent impulses to CNS • 3) Intergration center- always in CNS • may be 1 synapse between sensory & motor neuron or multiple synapses with chains of interneurons • 4) Motor neuron- transmits efferent impulses • 5) Effector- muscle fiber or gland that responds

  5. Reflexes • Intrinsic (inborn) reflexes • Usually rapid, predictable motor response to stimulus • Many cases we are aware of reflex, some go without awareness (visceral reflexes are regulated by lower regions of CNS- brain stem & spinal cord) • Acquired (learned) reflexes • Result from practice & repetition • Pavlov’s Dog (conditioned reflexes)

  6. Types of Reflexes • Spinal Reflexes (Ch 12) • Superficial reflexes- elicited by gentle cutaneous stimulation • Plantar reflex- elicited by drawing a blunt object downward along lateral aspect of the plantar surface • Normal response: Downward curling of toes, tests integrity of spinal cord from L4 to S2 • Babinski’s sign- great to dorsiflexes & smaller toes fan laterally • Seen in infants up to about 1yr, nervous system is not completely mylineated yet Plantar Reflex Babinski’s sign- damage on right side Babinski’s sign- Infant

  7. http://www.aqnt.com.au/images/SRA_Graph.gif

  8. http://classes.midlandstech.edu/carterp/Courses/bio210/chap13/210_figure_13_20_labeled.jpghttp://classes.midlandstech.edu/carterp/Courses/bio210/chap13/210_figure_13_20_labeled.jpg

  9. http://2.bp.blogspot.com/-Hdz81mh8s70/VeQGZKHIz-I/AAAAAAAAA6E/yy7XPPMIEw4/s1600/babinski.jpghttp://2.bp.blogspot.com/-Hdz81mh8s70/VeQGZKHIz-I/AAAAAAAAA6E/yy7XPPMIEw4/s1600/babinski.jpg https://classconnection.s3.amazonaws.com/467/flashcards/941467/png/picture26-13F5AA29F40344BC330.png

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