HB+Nervous+System

=**Nervous System Questions**=

What are the three parts of a neuron?

 * All neurons have three parts: a cell body, dendrites, and an axon.

What is a nerve impulse and how does it spread?

 * The two nerve impulses are the Resting potential and the Action potential The resting potential is more Na+ outside the axon and more K+ inside the axon. the axon does not conduct an impulse.
 * The action potential is a change in polarity across axonal membrane as a nerve impulse occurs: When Na+ gates open, Na+ moves to the inside of the axon, and a depolarization occurs. When K+ gates open and K+ moves to outside the axon, a repolarization occurs.

Since neurons don't physically touch, how is an impulse transmitted from one neuron to the next?

 * When a neurotransmitter is released into a synaptic cleft, transmission of a nerve impulse occurs. Binding of the neurotransmitter to receptors in the receiving membrane causes excitation or inhibition. Integration is the summing of excitatory and inhibitory signals.

What are the two main functions of the spinal cord?

 * The spinal cord serves to conduct nerve impulses to and from the brain, and to carry out reflex action.

What are the four major parts of the brain and the general function of each?

 * The cerebrum had two central hemispheres connected by the corpus callosum. Controls thinking and sensation.
 * The Diencphalon: The Hypothalus controls homeostasis. The thalmus sends sensory input on to the the cerebrum.
 * The Cerebellum coordinates skeletal muscle contractions.
 * The brain stem: the medulla oblongota and the pons have centers for breathing and the heartbeat