1. 9th Biology
The Nervous System

2. Structure of the Nervous System
Central Nervous System: CNS
Brain and Spinal Cord
Peripheral Nervous System: PNS
Everything else: peripheral nerves from the spinal cord to the limbs

3. Neurons
Neurons are specialized cells that help you gather information and react to it.

4. 3 Kinds of Neurons: 1. Sensory neurons- involuntary
Send impulses from receptors in skin and sense organs to brain and spinal cord
2. Interneurons- involuntary
carry impulse to motor neurons, which results in a response.
3. Motor neurons- voluntary
respond to stimulus; skeletal muscle

5. Neurons

6. Reflex Arc

7. Nerve Impulse: Action Potential
Electrical charge, traveling the length of the neuron.
Causes a message to be sent to other neurons to elicit a response
Neuron at rest: Resting potential

8. Action Potential
Na+ rushes into cell, changes charge from negative to positive. Causes neurotransmitters(chemicals) to be released at the terminal, to stimulate the next neuron in the chain.

10. Action Potential: One way only
Myelin- insulation on axon that helps signal’s rapid response
Multiple Sclerosis- disease where part of myelin sheath is worn away- nerve conduction no longer works properly

11. Synapse
Space between axon terminal of one neuron and dendrites of another.
Neurotransmitters in vesicles released in cleft either cause the cell to fire (excitatory) or not fire (inhibitory).

12. ORGANIZATION OF THE NERVOUS SYSTEM
1. Central nervous system: CNS
Brain and spinal cord
Relays messages, processes information, analyzes responses
The brain:
100 billion neurons
Cerebrum- Cognitive function
Cerebellum- balance, movement
Medulla oblongata- breathing rate, heart rate, blood pressure
Pons- breathing rate

14. ORGANIZATION, cont. 2. Peripheral nervous system: PNS
Everything outside the brain and spinal cord
A. Somatic nervous system:
Relays info to motor neurons
All voluntary except reflexes

15. ORGANIZATION, cont. B. Autonomic nervous system
Carries impulses from CNS to heart and other organs.
Fight or flight
Business as usual
Sympathetic branch- Active in times of emergency
Parasympathetic branch- Active when body is at rest