Chapter 3 Summary:
•Many of the genes in the human genome direct the development and ongoing
functions of the nervous system:
oA communication network that serves as the foundation for all psychological
•Neuron: the basic unit of the nervous system that operates through electrical
impulses, which communicate with other neurons through chemical signals.
oThree functions: Take in the information from neighbouring neurons
(reception), integrate those signals (conductions), and pass signals to
other neurons (transmission).
•Dendrites: First region- branchlike extensions of the neuron that detect information
from other neurons. Receive information from other neurons and transmit towards
the cell body. Information flows through a neuron from the dendrites to the axon
•Cell Body: Second region- in the neuron where information from thousands of other
neurons is collected and
processed. Keeps the neuron
alive. The DNA in the neuron
tells the neuron what to do.
Whether to ‘fire’ or not.
•Axon: Third region- a long
narrow outgrowth of a neuron by which information is transmitted to other neurons.
•Terminal Buttons: Small nodules at the ends of axons that release chemical
signals from the neuron to an area called the synapse Receives the action potential
from the axon and are involved in transmitting that information onto other neurons
through release of neurotransmitters to synapse.
•Synapse: The site for chemical communication between neurons.
oChemicals leave one neuron, cross the synapse and then pass signals along to
the dendrites of the other neurons.
•Three basic types of neurons are: Sensory neurons, motor neurons, and
•Sensory neurons detect information from the physical world and pass that
information along to the brain, usually via spinal cord.
oSensory neurons are often called afferent neurons because they send signals
from body to brain (AOR)
oSignals that travel from the brain to the body is known as efferent (ERO)
•Motor neurons direct muscles to contract or relax, thereby producing movements.
•Inter neurons communicate only with other neurons, typically within a specific
•Together sensory and motor neurons control movements.
•Action Potential: also called neuronal firing, is the electrical signal that passes
along the axon and causes releases of chemicals that transmit signals to other