1. Nervous System

2. The Nervous Systems
Central Nervous System(CNS): Made up of the brain and spinal cord, the CNS acts as the coordinating centre for incoming and outgoing information.
Peripheral Nervous System(PNS): Consists of the nerves that carry information between the organs of the body and the central nervous system. The PNS can be divided further:
- Somatic – controls the skeletal muscle, bones, and skin
- Autonomic – controls the internal organs of the body

4. Anatomy of the Nerve Cell
The nervous system is made up of two different types of cells:
Glial Cells: These cells are not involved in the conduction of nerve impulses. Instead, they provide structural support and metabolic activity to the nerve cells. These metabolic activities include: nutrition, maintaining homeostasis, and formation of myelin.
Neurons: These are the functional units of the nervous system. They are what allow us to control both voluntary and involuntary activities of the body.
There are 3 different types of neurons cells:
Sensory Neurons, Interneurons, Motor Neurons

5. The Neuron
Dendrite: The section of the neuron which receives incoming information. The send the signal into the cell body towards the axon.
Axon: Continues the signal away from the cell body.
Myelin: A fatty protein that coats the axons allowing signals to travel faster between neurons.
Schwann Cells – a special glial cell that forms the myelin
Nodes of Ranvier – The areas between the sections of myelin

6. Sensory Neurons
Sensory Neurons (a.k.a Afferent neurons) sense and relay information from the environment to the CNS.

7. Each Sensory Neuron Has A Receptive Field
Receptive Field: Each sensory neuron has a specific sensory field where that one neuron will receive stimuli from. These receptive fields have the ability to overlap. These receptive fields are larger in our back and forearms, and much smaller in our lips, and finger pads.

8. Interneurons
These neurons lie completely within the central nervous system. These come in many forms and process the incoming signals by the sensory neurons and signal the appropriate motor neurons.

9. Motor Neurons
Motor neurons (a.k.a. Efferent neurons) receive information from interneurons. These neurons cause a response by the muscles, organs, and glands.

10. Neurons Travel in Bundles
Neurons travel throughout our body in bundles referred to as nerves.

11. Neural Circuits
When we feel pain, we don't stop to think about how much that pain hurts. For example if we touch a hot stove, we pull our hand away quickly without thinking about it. This is referred to as a reflex arc.
The reflex arc begins when a receptor picks up a painful stimulus, Sensory information is sent to the spinal cord, and interneurons relay this information directly to the motor neuron. The motor neuron activates the muscle, causing it to contract. This allows our bodies to react as quick as possible.

12. Notice there is still a signal to the brain, why might that be?