Download Chapter 12 The Nervous System

Chapter 12
The
Nervous
System
Biology 3201
Unit I - Maintaining
Homeostasis II
Interesting Brain Facts
• The average adult human brain weighs three pounds, has a texture like
firm jelly and is made up of 75 percent water.
• Every time your heart beats, your arteries carry 20 to 25 percent of your
blood to the brain.
• Every time you recall a memory or have a new thought, you create a
connection in the brain.
• There are 100 billion neurons (nerve cells) in the brain
• There are 100,000 miles of blood vessels in the brain. The distance
around the world at the equator is 24,900 miles
• The average number of thoughts a person has each day is 70,000
What makes our brain different?
1. The ratio of the brain to body mass increases
2. A large cerebrum, which is involved in higher
mental abilities.
Over the past two
million years, the
human brain has
doubled in size.
What is the nervous system?
• The system made up of your brain, spinal
cord, and a network of nerves that thread
throughout your body.
• It's the control center for your entire body.
• Your brain uses information it receives from your nerves
to coordinate all of your actions and reactions. Without
it, you couldn't exist!
1.) It maintains homeostasis in living organisms
•Homeostasis – The process of maintaining a
relatively constant internal environment despite
changing external conditions
•Ex: when you get too hot,
you sweat
2.) It transmits electrical impulses as a
form of communication to and from
all parts of the body
3.) Coordinates movement
Two Major Parts of the Nervous System
• Central Nervous System (CNS)
– Made up of the brain and spinal cord
• Peripheral Nervous System (PNS)
– Made up of all the nerves that lead into and
out of the CNS.
• See Fig. 12.2 , Page. 392
CNS
Central Nervous System
• This system receives sensory information and
begins motor control
• This system is extremely important and
therefore must be well protected
How is the CNS protected?
1. Bone - skull around the brain and vertebrae
around the spinal cord
2. Protective membranes called meninges
surround the brain and spinal cord
3. Cerebrospinal fluid fills the spaces between
the meninges membranes to create a cushion
to further protect the brain and spinal cord.
• Worksheet: Phineas Gage
• Video: Phineas Gage
http://www.youtube.com/watch?v=c6kRP41ygrI
The Structure and Function of the Brain
 The brain processes information transmitted from the
senses so that the body can react to changes in the
external and internal environment.
 The brain makes up 2% of the body weight but may contain
15% of the blood supply and consumes 20% of the body’s
oxygen and glucose.
 The functioning of the brain is not entirely understood but
it involves neurons and an internal hormone system
http://www.brainline.org/multimedia/interactive_brain/the_human_brain.html?gc
lid=CLn4gvuCq7ICFTN0Mgod4WAAIA
Parts of the Brain (Figure 12.11 p.399)
Cerebrum
• the part of the brain where all information
from our senses is sorted and interpreted
• Voluntary muscles that control movement and
speech are stimulated from this part of the
brain
• Memories are stored and decisions are made
in this region. It is the center of human
consciousness
• The cerebrum is divided into two halves:
– Right and left hemispheres.
– Each hemisphere is covered by a thin layer
called the cerebral cortex. This cortex contains
over one billion cells.
• The cerebrum is also divided into four lobes.
See Fig. 12.12, P. 400
The 4 lobes are:
• Frontal Lobe – involved in the control of muscles,
helps us reason, think critically and plan.
• Temporal Lobe – receives info from our ears
• Occipital Lobe – receives info from our eyes
• Parietal Lobe – receives info from our skin &
skeletal muscles, and is associated with our
sense of taste
Cerebellum
• controls muscle coordination
• It contains 50% of the brain’s neurons but only
makes up 10% of brain volume
• It controls our balance. We do not have to
think about certain skills as we get older
because they are controlled by the cerebellum
Damage to the cerebellum video
• http://www.youtube.com/watch?v=5eBwn22
Bnio
Medulla Oblongata
• It is attached to the spinal cord at the base of the brain
• It controls:
• The cardiac center which controls heart rate
and force of contractions.
• The vasomotor center which adjusts blood
pressure by controlling blood vessel diameter.
• The respiratory center which controls rate and
depth of breathing.
• It also contains reflex centers for hiccupping,
vomiting , coughing and swallowing.
Damage to this part of the brain is usually fatal
Hypothalamus
• a complex bundle of tissue that acts as the main
control center for the autonomic nervous system.
• It enables the body to respond to external threats
by sending impulses to various organs via the
sympathetic nervous system.
• After the threat has passed, it reestablishes
homeostasis by stimulating the parasympathetic
nervous system.
Thalamus – the sensory relay centre.
• It receives sensations of touch, pain, heat and
cold, as well as information from the muscles
– Mild sensations are relayed to the cerebrum
– Strong sensations triggers an immediate reaction
& sends info to the hypothalamus
Midbrain – involved in sight and hearing. It is a
short section of brainstem between the cerebrum
and the Pons.
Pons - works with the medulla to regulate
breathing rate and has reflex centers involved in
head movement. It contains bundles of axons
traveling between the cerebellum and rest of
CNS.
Corpus Callosum - a series of nerve fibers that
connects the left and right hemispheres of the
brain.
http://www.youtube.com/watch?v=6Zd6IECeKs&feature=related
Structure of the Spinal Cord
• The function of the spinal cord is to provide
communication between the brain and the
peripheral nervous system (PNS).
• It is protected by vertebrae
• Spinal nerves pass through the vertebrae and out
to the PNS
What does the spinal cord look like?
• A cross section of the spinal cord shows:
1. Central canal which contains cerebrospinal fluid
2. Grey matter
3. White matter
See Fig.12.4 (page 393)
What is Grey Matter?
•
Grey matter is made of neural tissue which contains
three types of nerve cells or neurons:
1. Sensory neurons
2. Motor neurons
3. Interneurons
•
Grey matter is located in the center of the spinal
cord in the shape of the letter H.
What is White Matter?
• The white matter is found around the grey matter
• It contains the myelinated axons of interneurons that
carry information to and from the brain.
• Spinal Cord Anatomy
http://www.spineuniverse.com/anatomy/spinalanatomy-animation
Worksheet: Spinal Cord Injuries
2. Peripheral Nervous System
• Made up entirely of nerves
• The PNS is made up of two subsystems:
2a.Autonomic Nervous System (think of an automatic car)
2b.Somatic Nervous System (think of a standard car)
The Nervous System Simplified Video:
http://www.youtube.com/watch?v=sq9qfSusNmA
2a.) Autonomic Nervous System
• Not consciously controlled and is often called
an involuntary system.
• It is made up of two subsystems:
i) Sympathetic Nervous System
(think of speed)
ii) Parasympathetic Nervous System
(think of a parachute)
i.) Sympathetic Nervous System
• The sympathetic nervous system sets off what is known
as a “fight - or - flight” reaction. This prepares the body
to deal with an immediate threat.
• Stimulation of the sympathetic nervous system causes a
number of things to occur in the body:
1. Heart rate increases
2. Breathing rate increases
3. Blood sugar is released from the liver to provide
energy which will be needed to deal with the threat.
http://www.youtube.com/watch?v=jdJpLvSTZMU
ii.)Parasympathetic Nervous System
• The parasympathetic nervous system has an
opposite effect to that of the sympathetic nervous
system.
• It returns the body to its normal state of rest
• The parasympathetic system does this by:
1. Decreasing heart rate
2. Decreasing breathing rate
3. A message is sent to the liver to stop releasing
blood sugar since less energy is needed by the
body
Fight or Flight Response
• http://www.youtube.com/watch?v=m2GywoS
77qc
2b.) Somatic Nervous System
• The somatic nervous system IS under conscious control.
• It is made up of sensory nerves that carry impulses from
the sense organs to the CNS.
• It is also composed of motor neurons that transmit the
commands of the CNS to the muscles.
• The somatic nervous system will also involve reflex
actions that are not under conscious control.
Activity
• Create a flow chart to illustrate the division of
the nervous system (CNS and PNS)