1. The Nervous System

2. The Control Center Complex network of neurons and glial cells
Stores and processes information taken in from the environment
Invokes responses according to the information
Broken into:
Central
Peripheral

3. Neurons
Cells that electrically excitable and are used to transmit electrical and chemical signals (neurotransmitters)
Comprised of cell body, dendrites, axon(s), myelin, and Nodes of Ranvier
Classified by the number of processes*
1) Unipolar
2) Bipolar
3) Multipolar
4) Pseudomultipolar

4. Central Nervous System (CNS)
Composed of the brain and the spinal cord
Holds information in the form of electrical patterns
Brain is made up of the cerebrum and cerebellum

5. Parts of the Brain
The brain is composed of many specialized lobes and cortexes in order to perform the tasks of your everyday life
Hemispheres
Right and Left brain
Lobes
Frontal, Parietal, Occipital, Temporal
Other
Midbrain, Pons, Corpus Callosum

6. Peripheral Nervous System (PNS)
Networks extend to every part of the body
Collects sensory information and relays the info to the brain
5 “main” senses (you were lied to, there are more)
Sight, Smell, Hearing, Taste, Touch
Pain, Balance, Temperature, Kinesthetic (Proprioception)

7. Parts of the PNS
Neurons can extend up to 1 meter from the spinal cord to the leg or arm, etc.
Glial cells are support cells that provide a range of functions to aid the nervous system
They hold neurons in place
Supply nutrients to neurons
Can kill pathogens invading the neurons

8. Transmitting Messages
The nervous system uses electric charges in the membrane (membrane potential) to send and retain information.
The potential is created by the gradient of sodium and potassium on either side of the membrane of an axon
This gradient is controlled using various ion pumps to depolarize and repolarize the membrane for transmissions

9. Action Potentials
The result of these electric transmissions are called action potentials
Resting: -70 mv
Threshold: -55 mv
Peak: sometimes up to +100 mv
Overshoot: -90 mv (prevents backwards transmission)

10. Chemical Messages
Neurons also send chemical messages using neurotransmitters
Dopamine, Serotonin
These molecules travel across the synaptic cleft from the axon of one neuron to the dendrite of another
After crossing the gap, the
signal is once again transferred
to an electrical signal

11. Responding to stimuli
The CNS and PNS communicate through afferent and efferent neurons
Afferent: carries signals from sensory receptors to the CNS
Efferent: carries signals from CNS to motor neurons and autonomous systems
Interneurons carry signals exclusively within the CNS

12. Example: It’s too bright!
When you are inside of a building, your eyes are accustom to (relatively) weak electric lighting. The pupils dilate to let in more light.
When you step outside, the sunlight is much brighter and this information is sent to the brain (afferent).
The brain recognizes the issue and sends a signal to constrict the pupil so less light is taken in.

13. Reflex Arc
Depending on the message, an action can be issued by the spinal cord before it reaches the brain. This is called a reflex.
Natural reflexes
Lifting your foot if you step on a sharp object
Learned reflexes
Catching a ball
After the body has reacted, the signal will still continue to the brain so the experience can be stored and remembered for the future.

14. References
The Nervous System: CrashCourse

15. End