The Wonderful World of

1
The Wonderful World of
THE NERVOUS SYSTEM
The Nervous System
Provided to you by
That lab group in the back.
Jaclynn Chen Katie Tang Winnie Tema
2
An Overview of Nervous Systems
The nervous system carries out actions in three
functions.
First a signal, such as flashing light, is
translated through the sensory receptors .
This sensory input relays the information
collected from the outside world to integration
centers.
The information is interpreted by the integration
centers and sends this interpretation to the
motor output, which gives an appropriate response
of the body through effector cells.
The Central nervous system (CNS) includes the
integration center.
The Peripheral nervous system (PNS) includes the
sensory input and motor output.
Its kind of like when your send a letter. When
you drop a letter you wrote to your friend in
your mailbox, your local postal carrier picks of
the letter (like a sensory receptor) and takes it
to the post office. At the office, your letter is
mixed with the rest of the mail sent that day and
sorted out to the appropriate carrier and sent
out to deliver (integration center). The carrier
then sends your letter directly to your friends
house where he or she can read the lovely letter
your wrote just for him or her (motor output).
3
What sends the signals through the nervous
system?
Nerves are what do this. Nerves consist of
ropelike structures in bundles of neurons tightly
wrapped in connective tissue.
Groups of neurons are what make up nerves.
Neurons (aka nerve cells) carry out the structure
and function of the nerves.
Main parts of a neuron
Cell Body contain the nucleus and organelles of
cell
Dendrites receive incoming messages from other
cells to the cell body (coming in)
Axons transmit signals to other cells (going out)
Neuron structure
Axon hillock is where the axon meets the cell body
Myelin sheath wrap around axons, insulates them
Synaptic terminals are the terminal branches of
axons that transmit signals by releasing chemical
signals called neurotransmitters.
Synapse is the site between a synaptic terminal
and a target cell
Presynaptic cell is the transmitting cell
Postsynaptic cell is the target cell
Nervous System Cells - http//library.thinkquest
.org/2935/Natures_Best/Nat_Best_Low_Level/Nervous_
page.L.htmlNervous_Sys_Cells
4
Can you label the structures of the neuron and
the direction of the neurotransmitter?
A.
Presynaptic Cell
B.
C.
H.
D.
E.
G.
F.
Postsynaptic Cell

• Answers
• Dendrites
• Cell Body
• Nucleus
• Axon Hillock

E. Axon F. Myelin Sheaths G. Synaptic Terminal H.
Synapse
5
Not all nervous systems are the same you know
The simplest animals with nervous systems have an
expansive nervous system, which are arranged in
diffused nerve nets
More complex animals have nervous systems with
systems of nerves.
6
Ever wonder what makes those knee jerking
reactions?
Go aheadTry it.
Tap the tendon connected to the quadriceps muscle
What causes this to happen? This is a perfect
example that will allow us to observe the
different parts of the nervous system.
See the movement on this site!
http//www.dushkin.com/connectext/psy/ch02/reflex.
gif
http//www.bbc.co.uk/science/humanbody/body/factfi
les/reflexes/reflexes.shtml
7
Reflexes are caused by the automatic responses of
the reflex arc between the spinal cord and brain.
There are two kinds of nerve cells involved
Sensory neuron transmits information from a
sensory receptor to a motor neuron, which signals
an effector cell to carry out the response.
The knee jerking reaction goes through the
sensory neurons which relays the information to
the stretch receptor in the thigh muscle, to
interneurons in the spinal cord, which finally
inhibit motor neurons to the flexor muscles.
Motor neurons and interneurons are located in the
gray matter of the CNS. Motor sensory axons are
in the white matter.
Outside the spinal cord structure is a ganglion
(a cluster of nerve cell bodies) in the PNS.
Nuclei are similar to ganglion but are in the
brain.
8
Glia supporting cells of the nervous system
Astrocytes support the structure of the neuron
and regulate the concentration of ions and
neurotransmitters.
These induces the formation of the blood brain
barrier which restricts the passage of substances
into the brain.
Radial glia create and track newly formed neurons
from stem cells
Oligogendrocytes and Schwann cells are glia that
support the axons in the mylein sheath.
These membranes are mostly lipids which are poor
conductors of electrical current. Multiple
Sclerosis is a disease the degrades the myelin
sheaths.
See more of a description of multiple sclerosis
also known as MS.
http//www.youtube.com/watch?vqgySDmRRzxY
9
Explore more of the world of the nervous system
reflexes
http//www.bbc.co.uk/science/humanbody/body/factfi
les/reflexes/reflexes.shtml
10
Neurotransmitters travel by electrical impulses
The membrane potential is the difference of
charges across the plasma membrane
When the membrane is at resting potential, there
is no transmitting of signals. The voltage is
usually around -70 mV.
This membrane potential is due to the
concentration of ions on the two sides of the
membranes. Sodium (Na) ions are usually outside
making it negatively charged while potassium (K)
are usually inside making it positively charged.
These concentrations are maintained by sodium ion
pumps
K Na have ungated ion channels that allow
them to diffuse all the time at resting
potential.
K is more permeable than Na. When this
permeability changes, the membrane potential
changes
When the electrical gradient exactly balances the
concentration gradient, an equilibrium is
established.
Types of ion pumps that effect the membrane
potential
Stretch gated ion channels- cells that sense
stretch and open when the membrane is
mechanically deformed
Ligand-gated ion channels- found at synapses and
open or close when a specific chemical, like a
neurotransmitter, binds to the channel
See these pumps in action!
http//highered.mcgraw-hill.com/sites/0072495855/s
tudent_view0/chapter2/animation__how_the_sodium_po
tassium_pump_works.html
11
In response to a stimuli the membrane potential
of a cell open and closes its channels

• Graded potentials
• Hyperpolarization- an increase in the magnitude
  of the membrane potential
• May be caused by opening of gated K
• Depolarization- reduction in the magnitude of the
  membrane potential.
• May be caused by opening gated Na

12
Production of Action Potentials

• Depolarizations are graded only up to a certain
  membrane voltage or a threshold
• Once a stimulus is strong enough to produce
  depolarization that reaches the threshold,
  action potential is then produced.
• Action Potential is an all or none phenomenon
• Once it is triggered it has a magnitude that is
  independent of the strength of the triggering
  stimulus.
• In most neurons, the action potential is very
  brief. This allows the neuron to produce them at
  high frequencies.
• LEARN MORE http//outreach.mcb.harvard.edu/animat
  ions/actionpotential.swf, http//bcs.whfreeman.com
  /thelifewire/content/chp44/4402002.html.

13
Conduction of Action Potentials

• As an action potential travels, it regenerates
  itself along the axon in order to not diminish
  the cell body.
• The action potential is usually initiated at the
  axon hillock.
• Here, the Na influx creates an electrical
  current that depolarizes the neighboring region
  of the axon membrane.
• Afterwards, Repolarization occurs due to K
  efflux (Na channels still closed)
• Prevents action potentials from traveling back
  toward the cell body

14
Conduction Speed

• Factors that affect the speed at which action
  potentials are conducted
• Diameter- the larger the faster, the resistance
  to the flow of electrical current is inversely
  proportional to the cross-sectional area of the
  conductor.
• Myelin sheath- by insulating the axon membrane,
  which causes the depolarizing current associated
  with an action potential to spread farther along
  the interior of the axon. This brings more
  distant regions of the membrane to the threshold
  sooner.
• Saltatory Conduction- action potential appears to
  jump along the axon from node to node. It speeds
  it up to 120 m/sec in myelinated axons.

15
Action Potentials are not transmitted from
neurons to other cells, but at the synapses
information is transmitted

• Electrical synapses- contains gap junctions
  allowing electrical current to flow directly from
  cell to cell.
• Chemical synapses- involves the release of
  chemical neurotransmitter by the presynaptic
  neuron.
• Presynaptic neuron synthesizes the
  neurotransmitter and packages it in synaptic
  vesicles.
• Stored in the neurons synaptic terminals
• Information transfer is more modifiable at
  chemical synapses than at electrical synapses
• LEARN MORE http//users.rcn.com/jkimball.ma.ultra
  net/BiologyPages/S/Synapses.html,
  http//faculty.washington.edu/chudler/synapse.html
  .

16
Direct Synaptic Transmission

• The binding of the neurotransmitter to a
  particular part of the channel, the receptor,
  opens the channel and allows specific ions to
  diffuse across the postsynaptic membrane.
• Result- postsynaptic potential- a change in the
  membrane potential of the postsynaptic cell
• Synapses that cause depolarizations bring the
  membrane potential toward the threshold are
  called excitatory postsynaptic potentials.
• Na and K diffuses here
• Synapses that causes hyperpolarizations are
  called inhibitory postsynaptic potentials, they
  move the membrane potential farther from the
  threshold.
• Channels that are selective for K only

17
Summation of Postsynaptic Potentials

• Postsynaptic potentials magnitude varies with a
  number of factors
• The amount of neurotransmitter released by the
  presynaptic neuron
• They do not regenerate themselves as they spread
  along the membrane of the cell
• Smaller with distance from the synapse
• Two EPSPs are needed to trigger an action
  potential in a posynaptic neuron
• Two EPSP temporal summation
• Two EPSPs produced nearly simultaneously by
  different synapses on the same postsynaptic
  neuron spatial summation

18
Indirect Synaptic Transmission

• Here, a neurotranmitter binds to a receptor that
  is not part of an ion channel.
• Activates a signal transduction pathway involving
  a second messenger in the postsynaptic cell
• A variety of signal transduction pathways play
  arole in indirect synaptic transmission.
• Cyclic AMP- activates protein kinase A
• Phosphorylates specific channel proteins in the
  postsynaptic membrane

19
Neurotranmitters

• Acetylcholine

• Biogenic Amines

• One of the most common in vertebrates and
  invertebrates
• Vertebrates- it activates a signal transduction
  pathway
• G proteins? 1) inhibition of adenylyl cyclase 2)
  opening of K channels in the muscle cell membrane

• Derived from amino acids
• Includes epinephrine, norepinephrine, dopamine,
  and serotonin
• Often involved in indirect synaptic transmission-
  most common in CNS.

20

• Amino Acids and Peptides

• Gases

• Gamma Aminobutyric Acid, Glycine, Glutamate, and
  Aspartate- all known to function as
  neurotransmitters.
• Several neuropeptides serve as neurotranmitters.
• Many produced by post translational modification
  of much larger protein precursors.
• Substance P mediates perception of pain
• Endorphins- decreases pain perception

• Nitric oxide(NO), and Carbon Monoxide(CO)- local
  regulators
• CO is synthesized by enzyme heme oxygenase
• In brain it regulates the release of hypothalamic
  hormones
• In PNS it acts as inhibitory neurotransmitter
  that hyperpolarizes intestinal smooth muscle cells

21
In vertebrates the nervous system shows
cephalization and distinct CNS and PNS components

• CNS
• Brain- provides integrative power
• underling the complex behavior of vertebrates
• Spinal Cord- integrates simple responses to
  certain kinds of stimuli, conveys information to
  the brain
• Derived form dorsal embryonic nerve cord
• In an adult- this is the narrow central canal of
  the spinal cord and the four ventricles of the
  brain
• Called cerebrospinal fluid
• Axons are often found in well-defined bundles, or
  tracts
• whose myelin sheath give them a whitish appearance

22
The Peripheral Nervous System

• Transmits information to and from the CNS
• Plays a large role in regulating vertebrates
  movement and internal environment
• Structure- left-right pairs of cranial and spinal
  nerves, they are associated with ganglia
• Cranial Nerves- originate in the brain and
  terminate mostly in the organs of the head and
  upper body
• Spinal nerves- originate in the spinal cord and
  extend to parts of the body below the head

23
PNS divided into two parts

• Somatic Nervous System- carries signals to and
  from skeletal muscles, mainly in response to
  external stimuli
• Autonomic Nervous System- regulates the internal
  environment by controlling smooth and cardiac
  muscles and the organs of the digestive,
  cardiovascular, excretory, and endocrine systems.

24
Autonomic Nervous System Broken into three part

• Sympathetic Division- corresponds to arousal and
  energy generation
• Parasympathetic Division- causes opposite
  responses that promote calming and a return to
  self-maintenance functions
• Enteric Division- consists of networks of neurons
  in the digestive tract, pancreas, and gallbladder
• Controls these organs secretions as well as
  activity in the smooth muscles that produce
  peristalsis

25
Embryonic Development of the Brain

• Vertebrates consist of 3 bilateral symmetrical,
  anterior bulges of the neural tube
• Forebrain, midbrain and hindbrain
• Fifth week of human embryonic development, five
  regions have formed from the three primary bulges
• Forbrain telencephalon( cerebrum? cerebral
  cortex) , diencephalon
• Midbrain- mesencephalon- give rise to brain stem
• Hindbrain- metencephalon, myelencephalon- give
  rise to brain stem

26
The Brainstem

• Consists of stalk with caplike swellings at the
  anterior end of the spinal cord
• Three parts medulla oblongata, pons, midbrain
• Functioning in homeostasis, coordination and
  movement, and conduction of information to higher
  brain centers
• Neuron cell bodies send axons to many areas of
  the cerebral cortex and cerebellum

27

• Medulla oblongata- contains centers that control
  several visceral functions
• The Pons- participates in some of the above
  activities

28
The Cerebellum

• Develops from part of the metencephalon,
  important for coordination and error checking
  during motor, perceptual, and cognitive functions
• Involved in learning and remembering motor skills
• Receives sensory information about the position
  of the joints and the length of the muscles

29
The Diencephalon

• Epithalamus- includes the pineal gland and chroid
  plexus
• Thalamus- main input center for sensory
  information going to the cerebrum and the main
  output center for motor information leaving the
  cerebrum
• Hypothatlumus- most important brain regions for
  homeostatic regulation

30
The Cerebrum

• Develops from the telencephalon
• Divided into right and left cerebral hemispheres
• Each consists of an outer covering of gray
  matter, the cerebral cortex
• Internal white matter, groups of neurons
  collectively called basal nuclei

31
Cerebral Cotex

• Sensory information is analyzed, motor commands
  are issued, and language is generated
• Neocortex- forms outermost part of mammalian
  cerebrum, consisting of six parallel layers of
  neuron arranged tangential to the brain surface

32
ACTIVITY TIME!!!!!

• On the next slide is a picture with colors on it,
  only there is a catch the words are colors and
  the words are written in different colors. Now,
  try the best you can to repeat the different
  colors of the words. Instead of reading out the
  words repeat what color it is written in. Good
  luck because it is not an easy task!! This game
  is great to challenge your memory which is
  developed by the cerebellum.

33
(No Transcript)
34

• Concept 48.6
• The cerebral cortex controls voluntary movement
  and cognitive functions
• Each side of the cerebral cortex is customarily
  described as having four lobes, called the
  frontal, temporal, occipital, and parietal lobes.
  
• These areas include primary sensory areas, each
  of which receives and processes a specific type
  of sensory information, and association areas,
  which integrate the information from various
  parts of the brain.

The human cerebral cortex.  Each side of the
cerebral cortex is divided into four lobes, and
each lobe has specialized functions. Some of the
association areas on the left side (shown here)
have different functions than those on the right
side.
35

• Information Processing in the Cerebral Cortex
• Most sensory information coming into the
  cortex is directed via the thalamus to primary
  sensory areas within the lobes
• visual information to the occipital lobe
• auditory input to the temporal lobe
• somatosensory information about touch, pain,
  pressure, temperature, and the position of
  muscles and limbs to the parietal lobe
• Information about taste goes to a separate
  sensory region of the parietal lobe

Body representations in the primary motor and
primary somatosensory cortices.  In these
crosssectional maps of the cortices, the
cortical surface area devoted to each body part
is represented by the relative size of that part
in the cartoons.
(http//www.emc.maricopa.edu/faculty/farabee/BIOBK
/BioBookNERV.html)
36

• Lateralization of Cortical Function
• During brain development after birth, competing
  functions segregate and displace each other in
  the cortex of the left and right cerebral
  hemispheres, resulting in lateralization of
  functions.
• The left hemisphere becomes more adept at
  language, math, logical operations, and the
  serial processing of sequences of information. It
  has a bias for the detailed, speedoptimized
  activities required for skeletal muscle control
  and the processing of fine visual and auditory
  details.
• The right hemisphere is stronger at pattern
  recognition, face recognition, spatial relations,
  nonverbal thinking, emotional processing in
  general, and the simultaneous processing of many
  kinds of information.

The two hemispheres normally work together
harmoniously, trading information back and forth
through the fibers of the corpus callosum.
(http//www.kidshealth.org/parent/general/body_bas
ics/brain_nervous_system.html)
37

• Language and Speech
• The systematic mapping of higher cognitive
  functions to specific brain areas began in the
  19th century when physicians learned that damage
  to particular regions of the cortex by injuries,
  strokes, or tumors can produce distinctive
  changes in a persons behavior.
• The French physician Pierre Broca conducted
  postmortem examinations of patients who could
  understand language but could not speak. He
  discovered that many of these patients had
  defects in a small region of the left frontal
  lobe.
• That region, now known as Broca's area, is
  located in front of the part of the primary motor
  cortex that controls muscles in the face.

Mapping language areas in the cerebral cortex. 
These PET images show regions with different
activity levels in one person's brain during four
activities, all related to speech.
(http//www.emc.maricopa.edu/faculty/farabee/BIOBK
/BioBookNERV.html)
38

• Emotions
• Emotions are the result of a complex interplay of
  many regions of the brain
• Prominent among these regions is the limbic
  system, a ring of structures around the brainstem
  
• The limbic system includes three parts of the
  cerebral cortexthe amygdala, hippocampus, and
  olfactory bulbalong with some inner portions of
  the cortex's lobes and sections of the thalamus
  and hypothalamus
• These structures interact with sensory areas of
  the neocortex and other higher brain centers,
  mediating primary emotions that manifest
  themselves in behaviors such as laughing and
  crying

The Limbic System Structures of the limbic
system form early in development and provide a
foundation for the higher cognitive functions
that appear later, during the development of
neocortical areas.
39

• Memory and Learning
• We hold information, anticipation, or goals for a
  time in shortterm memory locations in the
  frontal lobes and then release them if they
  become irrelevant
• Should we wish to retain knowledge of a face or a
  phone number, the mechanisms of longterm memory
  are activated in a process that requires the
  hippocampus.
• The transfer of information from shortterm to
  longterm memory is enhanced by rehearsal
  (practice makes perfect), positive or negative
  emotional states mediated by the amygdala, and
  the association of new data with data previously
  learned and stored in longterm memory.
• Consciousness
• Over the past few decades, however,
  neuroscientists have begun studying consciousness
  using brainimaging techniques such as fMRI
• It is now possible to compare activity in the
  human brain during different states of
  consciousness
• These imaging techniques can also be used to
  compare the conscious and unconscious processing
  of sensory information

40

• Concept 48.7
• CNS injuries and diseases are the focus of much
  research
• Unlike the PNS, the mammalian CNS cannot fully
  repair itself when damaged or assaulted by
  disease
• Surviving neurons in the brain can make new
  connections and thus sometimes compensate for
  damage
• Nerve Cell Development
• To reach their target cells, axons must elongate
  from a few micrometers to a meter or more
• An axon does not follow a straight path to its
  target cells rather, molecular signposts along
  the way direct and redirect the growing axon in a
  series of midcourse corrections that result in a
  meandering, but not random, elongation.
• The responsive region at the leading edge of the
  growing axon is called the growth cone
• Signal molecules released by cells along the
  growth route bind to receptors on the plasma
  membrane of the growth cone, triggering a signal
  transduction pathway

41

• Neural Stem Cells
• Mice that live in stimulating environments and
  run on exercise wheels have more new neurons in
  their hippocampus and perform better on learning
  tasks than genetically identical caged mice that
  receive little stimulation
• Mature neurons, with their extensive processes
  and intricate connections with other cells,
  clearly are not able to undergo cell division
• Therefore, the new brain neurons must have come
  from stem cells
• Stem cells are relatively unspecialized cells
  that continually divide
• Diseases and Disorders of the Nervous System
• Schizophrenia - a severe mental disturbance
  characterized by psychotic episodes in which
  patients lose the ability to distinguish reality
• Depression - Two broad forms of depressive
  illness are known bipolar disorder and major
  depression. Bipolar disorder, or manicdepressive
  disorder, involves swings of mood from high to
  low and affects about 1 of the world's
  population. In contrast, people with major
  depression have a low mood most of the time they
  constitute roughly 5 of the population
• Alzheimer's Disease - a mental deterioration, or
  dementia, characterized by confusion, memory
  loss, and a variety of other symptoms. Its
  incidence is age related, rising from about 10
  at age 65 to about 35 at age 85
• Parkinson's Disease - a motor disorder
  characterized by difficulty in initiating
  movements, slowness of movement, and rigidity

42
Activity!

• The nervous system is the master controller of
  the body. Each thought, each emotion, each
  action- all result from the activity of this
  system! Through its many parts, the nervous
  system monitors conditions both within and
  outside the body. The nervous system processes
  information and decides what the body should do
  in response. When the response is needed, the
  nervous system will send out electrical signals
  that will direct the body.
• Just like the game of telephone, if one neuron
  (or student) confuses the message, any neurons
  (or students) continuing down the chain will
  receive the incorrect message.
• To do this activity, you will need
• to get into a circle with your classmates
• Choose one person to start a message by
  whispering the message to the student on her
  right
• Continue this message until the same person who
  started the message hears it from the student on
  his/her left
• Is the message the same?

43

• If the message isnt the same, what do you think
  happened? Did one student confuse the message?
  What happens in the body, if a neuron confuses
  the message?
• To further understand the Nervous System check
  out these links!
• http//www.innerbody.com/image/nervov.html
• http//www.argosymedical.com/medical_ani_sys/nervo
  us.html
• http//health.howstuffworks.com/adam-200011.htm

44
Any Questions?