Chapter 3

A genotype is an organism's constitution, or basically how a gene is made up at the time of conception. Phenotype is an organisms physical characteristics, resulting from outside influences such as the environment.

Motor neurons direct the muscles to contract or relax which will produce movement. Sensory neurons detect info from the physical world and send it to the brain, traveling through the spinal cord. Interneurons communicate within local or short distance circuits.

Dopamine serves as a neurotransmitter communicating which activities are rewarding or pleasurable. It also controls involuntary movement.

The amygdala serves as a tool for helping us associate things with emotional responses. It has the ability to sear a fearful into our mind for the rest of our lives'.

Learning is shown in the brain not by the number of connections in the brain, but by the strength of each connection. A faster firing connection means something is 'known better' than something with a slower connection.

Dizygotic twins are two zygotes that are closely related. Monozygotic twins are identical twins that can only be the same sex. They have the same chromosomes and genes on each chromosomes, which means the mono twins will have more similarities. One way to study whether or not behavior is genetically inherited is to study monozygotic twins who have been separated and raised by different families. If they have the same personality, behavior and traits, then chances are there are things that are inherited from biological parents.


Axons are the extended part of a neuron that is used for transmitting info to other neurons. They vary in length and carry messages from the brain to other parts of the body. Dendrites are short branchlike appendages that increase the neuron's receptive field and detect chemical signals from neighboring neurons. In other words, a dendrite specializes in receiving while an axon is used for sending.

Action potential (aka neural firing), is the electrical signal that passes along the axon and causes chemical releases that will send signals to other neurons. Resting potential is when a neuron is resting and the charges differ on the outside and the inside. During action potential, certain ion channels will open or close, thus altering the charges in the neuron.


A neurotransmitter is a chemical signal that will activate or inhibit a function of a neighboring cell. There are many types of neurotransmitters, such as endorphins and serotonin. Each type will trigger a certain thing. The neurotransmitter is sent into a microscopic gap, called a synapse from axons, which will be received by the dendrite.