Nervous System Enteric Sensory (afferent) System – transmits impulses from organs to CNS Sympathetic Peripheral Nervous System Central Nervous System Somatic (controls voluntary muscles) Autonomic (involuntary nervous system) Parasympathetic Motor (efferent) System – transmits impulses from CNS to peripheral organs to cause an affect or action Human Nervous System Components
The Neuron: The Universe Inside You
Neurons vs. Other Cells Neurons have dendrites and axons to carry information back and forth. Neurons can communicate with other neurons. Neurons have specialized structures, like synapses and chemicals.
Classification of Neurons
Neurons Work Electrochemically Ions are the electrically charged chemicals in neurons. The most common ions are: Sodium Potassium Calcium Chloride Ions can be negatively (-) or positively (+) charged. Ions can be outside or inside a neuron’s membrane.
A Neuron’s Potential Depends on the Charge of the Ions The charge of the ions determines the type of potential a neuron has. This animated graph shows the sequence: resting potential, action potential, and back to resting potential.
Polarized/Depolarized Neurons Resting neurons are polarized. When they become depolarized, an action potential occurs. Depolarization Resting state
Animations to Review Propagation of the action potential http://www.blackwellpublishing.com/matthews/actionp.html Click the blue circles on the left to play. Channel gating during an action potential http://www.blackwellpublishing.com/matthews/channel.html Click the “Begin Depolarization” gold circle to start.
Conduction Velocity Conduction velocity is the speed of a nerve impulse and is measured in meters per second (msec).
The wave on this animated graph represents the amount of time it takes for the nerve impulse to travel from the beginning to the end of the time line.
Variations in Conduction Velocity Factors that can affect conduction velocity: Temperature Myelination Width of axon lower the temperature, the slower the conduction velocity wider the axon, thefaster the conduction velocity moremyelination, the faster the conduction velocity Salutatory conduction example:http://www.brainviews.com/abFiles/AniSalt.htm
The Big Picture Sensory Neurons Sensory Neurons Motor Neurons Motor Neurons Internal Environment External Environment Central Nervous System