1. Nervous System

2. Structures  Brain, spinal cord, peripheral nerves Function  Recognizes and coordinates the body’s response to changes in its internal and external environment

3. Neurons Basic unit of structure & function in the nervous system The messages carried by the nervous system are electrical signals called impulses. Neurons – cells that transmit the signals (impulses) 3 Types of Neurons: 1. Sensory neurons – carry impulses from the sense organs to the spinal cord & brain 2. Motor neurons – carry impulses from the brain & spinal cord to muscles & glands 3. Interneurons – connect sensory & motor neurons and carry impulses between them

4. Diagram of Neuron CELL BODY NUCLEUS AXON AXON TERMINALSAXON TERMINALS DENDRITES MYELIN SHEATH

5. 2 Divisions of the Nervous System 1. Central Nervous System  Consists of the brain and spinal cord  Relays messages, processes information and analyzes information 2. Peripheral Nervous System  Consists of all the nerves and cells not part of the brain and spinal cord (includes ganglia)  Transmits impulses from sense organs to the central nervous system  Transmits impulses from the central nervous system to muscles or glands

6. Reaction to a Stimulus The peripheral nervous system transmits impulses from sense organs to the central nervous system and back to muscles or glands. Reflex – a quick, automatic (involuntary) response to a stimulus; allows your body to respond to danger immediately without spending time thinking about a response Example: When you step on a tack, sensory receptors in your foot stimulate a sensory neuron, which relays the signal to an interneuron within the spinal cord. The signal is then sent to a motor neuron, which in turn stimulates a muscle in your leg to lift your leg.