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Nervous System
Central
Nervous
System
(CNS)
Peripheral
Nervous
System
(PNS)
Organization of the nervous system
Organization of the nervous system
The Nervous System
Nervous System: Consists of all the nerve cells.
**It is the body’s speedy, electrochemical
communication system.
Central Nervous System (CNS): the brain and
spinal cord.
Peripheral Nervous System (PNS): the sensory and
motor neurons that connect the central nervous
system (CNS) to the rest of the body.
Organization of the nervous system
4
The central nervous system
Brain
Spinal cord
A collection of neurons and
supportive tissue running from the
base of the brain down the center of
the back
Protected by spinal column
Central Nervous System –
The Spinal Cord and Reflexes
Organization of the nervous system
The Nerves
• Nerves consist of neural “cables” containing
many axons.
• They are part of the peripheral nervous system
and connect muscles, glands, and sense organs
to the central nervous system.
Divisions of the Peripheral
Nervous System
• There are two divisions of the peripheral nervous system:
– the somatic, or voluntary portion
– the autonomic, or involuntary portion
 Somatic Nervous System: The division of the peripheral
nervous system that controls the body’s skeletal muscles
(voluntary).
 Autonomic Nervous System: Part of the PNS that controls
the glands and other muscles (involuntary).
Organization of the nervous system
Autonomic Nervous System (ANS)
• The autonomic portion of the peripheral
nervous system governs involuntary,
visceral functions…such as heart and
breathing rate, blood pressure, etc.
• It is divided into two systems:
– Sympathetic Nervous System: Division of the
ANS that arouses the body, mobilizing its
energy in stressful situations.
– Parasympathetic Nervous System: Division of
the ANS that calms the body, conserving its
energy.
Organization of the nervous system
The Sympathetic Nervous System
• Mobilizes the
body’s
resources for
emergencies
and creates
the fight-orflight
response.
• “Arouses”
Organization of the nervous system
The Parasympathetic Nervous System
• Activates
processes
that conserve
bodily
resources…
slowing
heart rate,
reducing
blood
pressure, etc.
• “Calms”
(rest and
digest)
Recap
See “Fight or Flight” in action in this
short cartoon:
http://cmhc.utexas.edu/stressreces
s/Level_One/fof.html
Review
• In everyday situations the sympathetic and
parasympathetic nervous system work
together to keep you in a steady internal
rate.
• What happens if these are out of wack?
–.
Journal
• How does information flow through your
nervous system as you pick up a fork?
Summarize this process.