Transcript Nervous System Central Nervous System • The central nervous system is divided into two parts: the brain and the spinal cord. • The average adult human.

Nervous System
Central Nervous System
• The central nervous
system is divided into
two parts: the brain
and the spinal cord.
• The average adult
human brain weighs
1.3 to 1.4 kg
(approximately 3
pounds).
Central Nervous System
• The spinal cord is about 43 cm
long in adult women and 45 cm
long in adult men and weighs
about 35-40 grams.
• The vertebral column, the
collection of bones (back bone)
that houses the spinal cord, is
about 70 cm long. Therefore, the
spinal cord is much shorter than
the vertebral column.
Peripheral Nervous System
• The peripheral nervous system is
divided into two major parts: the
–Somatic Nervous System
–Autonomic Nervous System.
Peripheral Nervous System
• Somatic Nervous System - Controls
voluntary muscles movement
• Autonomic Nervous System - Controls
glands and muscles related to our organs.
Although possible to override by conscious
thought, for the most part these reactions
occur spontaneously.
– Sympathetic Nervous System - Arouses the
person to get ready for fight or flight.
– Parasympathetic Nervous System - Calms and
relaxes the person and conserves energy.
1. Somatic Nervous System
• The somatic nervous
system consists of
peripheral nerve fibers that
send sensory information to
the central nervous system
AND motor nerve fibers that
project to skeletal muscle.
• The picture on the left shows
the somatic motor system.
The cell body is located in
either the brain or spinal
cord and projects directly to
a skeletal muscle.
2. Autonomic Nervous System
• The autonomic nervous system is divided
into three parts: the sympathetic nervous
system, the parasympathetic nervous
system and the enteric nervous system.
The autonomic nervous system controls
smooth muscle of the viscera (internal
organs) and glands.
• This picture shows the general organization of the
autonomic nervous system. The autonomic nervous
system is divided into three parts: the sympathetic
nervous system, the parasympathetic nervous system
and the enteric nervous system. The autonomic nervous
system controls smooth muscle of the viscera (internal
organs) and glands.
• Notice that the somatic nervous system has only one
neuron between the central nervous system and the
target organ while the autonomic nervous system uses
two neurons.
Sympathetic Nervous System
• Think about a time you've been in a really
dangerous or frightening situation. In that
situation your body responded by, for example,
increasing your heart rate, raising your
respiration, moving blood from one place (e.g.,
your digestive system) to another (your
muscles), etc.
• These responses are all "arousal" responses
which get you ready to fight or flee in times of
danger. Your physical reaction is called a reflex.
Sympathetic Nervous System
• It is the sympathetic nervous system that
is responsible for these responses that get
your body aroused to respond. This
system works with the parasympathetic
nervous system which is responsible for
then calming your body after the arousal
(to get you back to normal). Both of these
are actually part (subparts) of the
autonomic nervous system.
Parasympathetic Nervous System
• The parasympathetic nervous system is
part of the autonomic nervous system. Its
main function is to conserve/restore your
body's energy.
• For example, the parasympathetic nervous
system is responsible for sending signals
to slow your heart rate and breathing, and
speed up your digestive tract in order to
digest calories and save energy.
ANS The 2 Divisions
The roles of the
sympathetic and
parasympathetic
nervous system are
opposing. Generally the
sympathetic nervous
system has a
stimulatory affect and
prepare the body for
action while the
parasympathetic system
returns the body
functions to normal.
sympathetic
parasympathetic
Pupil dilation; tear
production not
affected
Pupil constricts; tear
production stimulated
Heart rate increase
Heart rate decrease
Bronchi dilate
Bronchi constrict
Gastric+pancreatic
activity inhibited
Gastric+pancreatic
activity stimulated
Glycogen converted Glucose converted
into glucose
into glycogen
Release of
adrenaline+noradre
naline
Release of
adrenaline+noradrenal
ine cease
Peristalsis inhibited
Peristalsis stimulated
Bladder relaxes
Bladder constricts
Enteric Nervous System
• The enteric nervous system
is a third division of the
autonomic nervous system
that you do not hear much
about.
• The enteric nervous system is
a meshwork of nerve fibers
that innervate the viscera
(gastrointestinal tract,
pancreas, gall bladder).