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Crash course: Nervous system

Crash course: Nervous system. Three Functions. 1. Sensory input: signals conducted from sensory cells in body (heat, touch, hearing, balance, vision, smell, taste, etc.) 2. Integration: information interpreted and processed (in brain and spinal cord).

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Crash course: Nervous system

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  1. Crash course: Nervous system

  2. Three Functions • 1. Sensory input: signals conducted from sensory cells in body (heat, touch, hearing, balance, vision, smell, taste, etc.) • 2. Integration: information interpreted and processed (in brain and spinal cord). • 3. Motor output: signals carried to muscles and glands.

  3. Two Parts • Central nervous system – processes information; brain and spinal cord; covered by protective meninges layers and bathed in cerebrospinal fluid. • Spinal cord incased in vertebral column; simple stimuli and responses (reflexes); carries info to brain. • Human brain divided into forebrain, midbrain, and hindbrain.

  4. Brain Structure • Forebrain:cerebrum right and left hemispheres (center of intelligence) connected by corpus callosum; thalamus (relay station); hypothalamus (regulates heart rate, bp, temp, and pituitary hormones). • Hindbrain:medulla (controls heart and breathing); cerebellum (balance and coordination); pons (connects cerebellum to cerebrum).

  5. Nervous system cells • 1. Neurons – nerve cells made up of dendrites (receive signals), cell body (contains organelles), and axons (carries signals away from cell body). • a. Sensory neurons gather sensory info. • b. Motor neurons carry out action signals. • c. Interneurons integrate input and output. • Synapses “connect” neurons by electrical or chemical means (neurotransmitters).

  6. Nervous system cells cont. • 2. Supporting cells -- help neurons function; 10-50 times more than neurons. • a. Glial cells found in CNS; form blood-brain barrier and myelin sheath. • b. Schwann cells found in PNS; form myelin sheath.

  7. Nerve Impulse • Nerve impulses are electrical signals. • Depends on flow of electrons across the neuron’s cell membrane. • Neuron at rest has higher numbers of Na+ outside, higher number of K+ inside, and high numbers of Cl- outside. • Membrane potential is about –70 mV. • Sodium-potassium pump keeps ions in these concentrations so neuron can be ready to fire.

  8. Nerve impulse cont. • Electrical stimulus at the dendrites causes a shift in the ion balance as Na+ enters the cell (depolarization). • When membrane potential rises +15-20 mV, the action potential is triggered. • Na+ continues into the cell and K+ exits the cell as protein channels open (more depolarization); total +100 mV change. • Action potential moves like a wave down the axon to the end of the cell. • Membrane proteins will then reset the Na+/K+ balance.

  9. Animations • Nerve impulse http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter14/animation__the_nerve_impulse.html • Synapse http://www.mind.ilstu.edu/flash/synapse_1.swf

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