Ch. 3 Paragraphs

1. What are monozygotic and dizygotic twins, and how can we compare them to determine whether some behavior is partly caused by genetic factors?
    Monozygotic twins are identical twins that resulted from one fertilized egg dividing into two zygotes. Each zygote has the same chromosomes and the same genes. Research has proved that monozygotic twins' DNA might not be so identical. Dizygotic twins or fraternal twins result from two separate eggs being fertilized and developing in the womb simultaneously. Studies have found that identical twins, raised separate or not, end up being much more alike than dizygotic twins.
2. What is the difference between axons and dendrites, and what functions do they serve in neurons?
    Dendrites are the short branch-like appendages of a neuron that increase the neuron's receptive field and detect chemical signals from neighboring neurons. Axons are the long narrow outgrowth of a neuron that transmit information to other neurons. Axons can vary in length between a millimeter to more than a meter. Neurons do not touch each other; instead they communicate and transmit information by sending chemical signals and electrical impulses through the terminal buttons that protrude from one end of a neuron to the dendrites of another neuron through a small gap called the synapse.
3. Describe the resting potential and the action potential. What ion movements occur during the action potential?
    Resting membrane potential is when a neuron's inside and outside differ electrically while it is inactive. Action potential (neural firing) is the electrical signal that passes along the axon and causes the release of chemicals that transmit signals to other neurons. In its inactive state, a neuron is slightly negatively charged. When a neurons fires, sodium gates in the cell membrane open allowing sodium ions in which cause the neurons to become slightly more positive because of depolarization. A fraction of a second later potassium channels open causing the neuron to return to its negative state (repolarization).
4. How do neurotransmitters allow one neuron to communicate with another?
    Every terminal button has vesicles that contain neurotransmitters, a chemical substance that carries signals across the synaptic cleft. after an action potential, the vesicles release the neurotransmitters which then span across the synapse and attach themselves to the postsynaptic neuron.
5. List the four lobes that form each brain hemisphere, and describe the areas of the cortex that process seeing, hearing, touch, and movement.
    The frontal lobe of the brain is basically the front upper third of the brain and is responsible for the ability to think, plan, and move. The temporal lobe is a large majority of the bottom rear side of the brain. It deals with the ability to hear, which makes sense considering the ears are right on top of it. The parietal lobe is the back upper half of the brain and deals with touch and spatial relations. The occipital lobe is the back lower little corner of the brain which deals with vision.