AP BIOLOGY

Detailed explanation-1: -The nervous system uses tiny cells called neurons (NEW-ronz) to send messages back and forth from the brain, through the spinal cord, to the nerves throughout the body. Billions of neurons work together to create a communication network.

Detailed explanation-2: -A neuron sending a signal (i.e., a presynaptic neuron) releases a chemical called a neurotransmitter, which binds to a receptor on the surface of the receiving (i.e., postsynaptic) neuron. Neurotransmitters are released from presynaptic terminals, which may branch to communicate with several postsynaptic neurons.

Detailed explanation-3: -The afferent division of the peripheral nervous system carries impulses to the CNS; the efferent division carries impulses away from the CNS.

Detailed explanation-4: -Specialized projections called axons allow neurons to transmit electrical and chemical signals to other cells. Neurons can also receive these signals via rootlike extensions known as dendrites.

Detailed explanation-5: -The dendrites carry impulses toward the cell body. The axon carries impulses away from the cell body. Axons and dendrites are sometimes called nerve fibers.