1. The Nervous System
Chapter 3.1

2. CNS vs. PNS
CNS: Central Nervous System
Brain and the spinal cord

3. PNS: Peripheral Nervous System
Nerve cells that send messages between central nervous system and other parts of the body

4. Neurons
Nerve cells that run through our entire body and communicate with each other
Messages relate to certain events
Ex.: memories, learning a new skill, injury

5. In case of injury or disease, the brain can reorganize itself by altering connection between neurons
Ability to reorganize neurons in brain = neuroplasticity

6. Parts of a neuron:
Cell body: produces energy to fuel neural activity

7. Dendrites: receive information from other neurons and pass the message through the cell body
Cell bodies have many dendrites; one axon

8. Axons: transmit messages away from the cell body
Vary in length: smaller than an inch to a several feet
Myelin: fatty sheath that covers and protects the axon
Speeds transmission of messages sent from neurons
Axon Terminals: fibers holding the axons

9. Communication between Neurons
Flow of message:
Axon Terminals  Dendrites
Messages move in one direction

10. Synapse: junction between the axon terminal of one cell and the dendrites of the next

11. Sensory Neurons: information received by senses to the CNS
Motor Neurons: nerve cells that carry information from the CNS to muscles and glands

12. Neurotransmitters
Neurotransmitters: chemicals that are stored in sacs in the axon terminals.
Chemical message between two neurons
Converted into an electrical impulse that travels through the neuron, triggers another release of neurotransmitter to go the next neuron, etc.
Process takes a fraction of a second

13. Numerous types of neurotransmitter each serves a different purpose
Each has its own structure; fits into receptor site on the next neuron
Imbalance of neurotransmitter can lead to certain diseases or mental disorders

14. Ex.: acetylcholine involved in memory; too little can impair the formation of new memories (possibly tied to Alzheimer’s)
Ex.2: dopamine involved in motor behavior; too little can cause trembling hands, problems with balance, and uncoordinated movements (Parkinson’s)

15. Central Nervous System
Brain and spinal cord

16. Spinal cord: column of nerves; extends from brain down the back
Protected by the spine
Transmits messages between brain and the muscles and glands

17. Spinal reflexes: automatic response to a trigger without input from the brain
Occurs when nerve impulses are received from the body’s sensory organs (eyes, ears, etc.)
Message is passed along to the brain but the reflex is carried out without direct input from the brain
Ex.: touching a hot stove; blinking; tapping the kneecap

18. Peripheral Nervous System
Transmits messages between CNS and everywhere else in your body
Divided between the somatic nervous system (SNS) and the autonomic nervous system (ANS)

19. Somatic Nervous System
Transmits sensory messages to the CNS
Carry messages from voluntary muscles and sense organs

20. Activated by touch, pain, temperature changes, and body position
Allows experiencing of heat/cold, pressure, pain
Ex.: Fuzzy Puppy—feeling warmth from sitting on your lap, soft fur, and pain if the puppy bites you

21. Alerts brain which parts of the body moved; maintains balance and posture

22. Autonomic Nervous System
“autonomic” = occurring involuntarily

23. Regulates body’s vital functions like heartbeat, breathing, digestion, blood pressure, etc.
Regulates involuntary muscles and internal organs

24. Two divisions: Sympathetic: Parasympathetic:
Prepares body for action under stress; “fight or flight”
Parasympathetic:
Restores body’s reserves of energy after intense activity; body returns to normal
“rest and digest”

25. Example of the communication:
You see a tiger outside of its cage at the zoo.

26. Sensory neurons relay message to the CNS
Sensory neurons relay message to the CNS. “I see a tiger outside of the cage! It’s almost like in nature!”

27. Brain processes the situation
Brain processes the situation. The tiger looks pretty cool outside its cage. You’re in a zoo so there has to be an employee near by, but you’re still a bit nervous—this is a new situation. CNS tells you to watch the tiger and look for the employee.

28. You see the employee. He’s laying on the ground, mauled by the tiger
You see the employee. He’s laying on the ground, mauled by the tiger. You panic. CNS freezes.

29. PNS (autonomic nervous system) kicks your adrenal glands into overdrive (fight or flight) and your legs begin to break into a run. OR your adrenal glands go into overdrive, you tackle a scared zoo employee, take his/her tranquilizer gun and stop the tiger.

30. After successfully fleeing or fighting the tiger, you feel a bit weak
After successfully fleeing or fighting the tiger, you feel a bit weak. Your adrenal glands have slowed down. You feel a need to sit down and eat. The gift shop is nearby; you walk in, get some ice cream and sit on a bench. Your body returns to normal (parasympathetic nervous system).

31. You save the princess.
Game over.

32. Until next tiger…