Pareto Principle

80/20 rule; 50% output comes from 20% input.

Neurons

Highly specialized nerve cells of the nervous system.

Dendrites

Branching extensions of a neuron that receive information.

Soma

Cell body of a neuron; contains cell nucleus.

Axon

Extensions of a neuron through which impulses are sent.

Axon terminals

End point of neuron where neurotransmitters are stored.

Myelin

Tissue that protects the neuron and speeds up neural transmissions.

Action Potential

Nerve impulse; brief electrical charge that travels down the length of a neuron.

Refractory Period

Brief recharging period after an action potential.

Resting Potential

The state of a neuron when it is at rest and capable of generating an action potential.

All or None Principle

Fact that neurons always 'fire' with the same intensity regardless of the strength of the stimulation.

Synapse

Tiny, fluid-filled gap between the axon terminal of one neuron and the dendrite of another.

Neurotransmitter

Chemical messenger that travels across synapse from one neuron to the next.

Excitatory Effect

Neurotransmitter effect that makes it more likely that the receiving neuron will generate an action potential.

Inhibitory Effect

Neurotransmitter effect that makes it less likely that the receiving neuron will generate an action potential.

Receptor Cells

Specialized cells in every sensory system that turn other kinds of energy into action potentials.

Sensory Nerves

Nerves that carry information from the sense receptors to the spinal cord and brain.

Motor Nerves

Nerves that carry information from the brain to muscles and glands.

Interneurons

Nerve cells in the brain and spinal cord that process information.

Central Nervous System (CNS)

Brain and spinal cord; interneurons process information.

Peripheral Nervous System (PNS)

Sensory and motor nerves that connect the brain and spinal cord to the rest of the body.

Somatic Nervous System

Division of the PNS that controls the body's skeletal muscles.

Autonomic Nervous System

Division of PNS that controls the glands and muscles of the internal organs.

Sympathetic Division

Arouses the body to deal with perceived threats.

Parasympathetic Division

Calms the body.

Endocrine System

Set of glands that produce hormones.

Hormones

Chemical messengers that circulate throughout the body in the blood.

Pituitary Gland

Master gland; controls other endocrine system glands.