Download Nervous System Notes

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Biology
The Nervous System
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
Neurons
• Neurons are specialized cells that help you
gather information and react to it.
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
Neurons
Reflex Arc
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
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.
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
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).
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
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
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