1. What makes us feel, act, and think?
The Nervous System
What makes us feel, act, and think?

2. How is the Nervous System Broken down?

4. Central Nervous System

5. Brain

6. Spinal Cord

7. Neurons
The neuron is the basic working unit of the brain, a specialized cell designed to transmit information to other nerve cells, muscle, or gland cells.
Neurons are the key component of the nervous system. There are two main types: sensory and motor.

8. What about Neurons?
Neurons come in many sizes. For example, a single sensory neuron from your fingertip has an axon that extends the length of your arm, while neurons within the brain may extend only a few millimeters.
Sensory neurons carry signals from the outer parts of your body (periphery) into the central nervous system.
Motor neurons (motorneurons) carry signals from the central nervous system to the outer parts (muscles, skin, glands) of your body.
Interneurons connect various neurons within the brain and spinal cord.

9. Neurons

10. How Neurons Work

11. How Neurons Send Messages

12. Neurotransmitters

13. Neurotransmitters
Acetylcholine is a very widely distributed excitatory neurotransmitter that triggers muscle contraction and stimulates the excretion of certain hormones. In the central nervous system, it is involved in wakefulness, attentiveness, anger, aggression, sexuality, and thirst, among other things. 
Dopamine is a neurotransmitter involved in controlling movement and posture. It also modulates mood and plays a central role in positive reinforcement anddependency. 
GABA (gamma-aminobutyric acid) is an inhibitory neurotransmitter that is very widely distributed in the neurons of the cortex. GABA contributes to motor control, vision, and many other cortical functions. It also regulates anxiety. 

14. More neurotransmitters
Glutamate is a major excitatory neurotransmitter that is associated with learning and memory. It is also thought to be associated with Alzheimer’s disease, whose first symptoms include memory malfunctions. 
Norepinephrine is a neurotransmitter that is important for attentiveness, emotions, sleeping, dreaming, and learning. Norepinephrine is also released as a hormone into the blood, where it causes blood vessels to contract and heart rate to increase. Norepinephrine plays a role in mood disorders such as manic depression. 
Serotonin contributes to various functions, such as regulating body temperature, sleep, mood, appetite, and pain. Depression, suicide, impulsive behaviour, and agressiveness all appear to involve certain imbalances in serotonin.