Understanding the Nervous System and Sensory Organs

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Peripheral Nervous System

Consists of nerves and supports it collects info about the body's external and internal environment.

Central Nervous System

Consists of the brain and spinal cord, processes info, and creates a response.

Cell Body

The largest part of the typical neuron.


Short branched extensions that receive impulses from other neurons and carry them to the cell body.


Long fiber that carries impulses away from the cell body.

Myelin Sheath

Insulating membrane that surrounds a single, long axon.

Resting Potential

Electrical charge across the cell membrane of a resting neuron.

Action Potential

A nerve impulse that charges more negatively charged to more positively charged.


The minimum level of a stimulus that is required to cause an impulse in a neuron.


The point at which a neuron transfers an impulse to another cell.

  • Neurotransmitters: Chemicals that transmit an impulse across a synapse to another cell.
  • Reflex: A quick, automatic response to a stimulus.
  • Cerebrum: Responsible for the voluntary activities of the body.
  • Cerebral Cortex: The outer layer of the cerebrum that consists of densely packed nerve cell bodies.
  • Thalamus: Located between the brain stem and the cerebrum that receives messages from sensory receptors throughout the body and relays info on the proper region of the cerebrum.
  • Hypothalamus: The control center for recognition and analysis of hunger, thirst, fatigue, anger, and body temperature.


The second largest region of the brain; info about the muscle and joint position and sensory impulses are sent there.

Brain Stem

Connects the brain and spinal cord regulates the flow of information between the brain and the rest of the body.


Neurotransmitter that is associated with the brain's pleasure and reward centers.

Somatic Nervous System

Regulates body activities that are under conscious control.

Reflex Arc

The sensory receptor, sensory neuron, motor neuron, and effector that are involved in a quick response to a stimulus.

Autonomic Nervous System

Regulates activities that are involuntary, or not under conscious control.

Taste Buds

Sense organs that detect taste.


Contains nerve that detects sound.

Semicircular Canals

One of three structures in the inner ear that monitor the position of the body in relation to gravity.


A tough transparent layer of cells where light enters the eye.


A disk-shaped structure; the colored part of the eye.


A small opening in the middle of the iris that regulates the amount of light that enters the eye.


Structure in the eye that focuses light rays on the retina.


Innermost layer of the eye; contains photoreceptors.


Photoreceptor in the eyes that is sensitive to light but can't distinguish color.


Photoreceptor that responds to light of different colors, producing color vision.

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