Transcript Central Nervous System Peripheral Nervous System

Nervous System
Nerves
• Hold out your hand in front of you
• Now wave at yourself
• Now, tap your head
• Put your arms down
• Say out loud to “Move Arm”…Just tell it to move
▫ Did it move?
▫ Why not?
Nerves
• How does our arm know when you want it to
move?
• Our experiment shows that your arm does not
understand spoken commands.
• So what does it understand?
• What tells it to move. If you think it is your
brain, you are correct.
Nerves
• But wait a moment. Your brain is clear up in
your head, while your arm is clear down on your
body.
• How does your brain talk to your arm? Somehow
they must be connected.
• The connection between your brain and your
arm, as well as every other part of your body is
known as your nervous system.
Nervous System
• How are messages transmitted along your
nervous system? Interestingly enough, messages
travel from your brain to your various body parts
via electricity, in much the same way cable
television signals travel from the cable company
to your house, or in the same way that this web
page traveled from our web servers to your
computer.
Are your Synapses Firing?
• Remember that the cells making
up your nervous system are called
neurons.
• Neurons are connected to other
neurons, as well as to other
tissues within the body via
synapses.
• The location where a neuron
connects to another cell is called a
synapse.
Brain neurons firing
• When a message is transferred
through a neuron it passes to the
next neuron via an amazing fast
chemical and electrical reaction.
• Because of its lightning speed, it is
often said that a person’s synapses
are firing when they are in deep
thought.
• Regardless of whether you are
solving a problem, or taking a nap,
your synapses are always busy
transporting messages.
The Central Nervous System (CNS)
• The Central Nervous System
is made up of your brain,
and your spinal cord.
• It is the main control center
of your body, and the center
of thought. Your Central
Nervous System controls
most of the actions within
your body.
Peripheral Nervous System
• 3 kinds of neurons connect
CNS to the body
▫ sensory
▫ motor
▫ interneurons
• Motor - CNS to muscles and
organs
• Sensory - sensory receptors
to CNS
• Interneurons: Connections
Within CNS
Brain
Spinal
Cord
Nerves
Peripheral Nervous System
Peripheral Nervous System
Skeletal
(Somatic)
Autonomic
Sympathetic
Parasympathetic
Neurons Generate Nerve Impulses
• A nerve impulse travels along the axon and
dendrites as electrical current caused by ions
moving in and out of the neuron through
voltage-gated channels
▫ these membrane channels open and close in response
to electrical voltage changes
• The impulse starts when pressure or other
sensory inputs disturb a neuron’s plasma
membrane, causing Na+ channels to open
Neurons Generate Nerve Impulses
• When Na+ channels open, Na+ floods into the
neuron from the outside
▫ for a brief moment, the inside of the neuron is
“depolarized,” becoming more positive
▫ the open Na+ channels in the small patch of
depolarized membrane remain open for only a
half a millisecond
▫ if the voltage change of the depolarization is great
enough, it causes nearby voltage-gated Na+ and K+
channels to open
Neurons Generate Nerve Impulses
• The Na+ channels open first, which starts a wave
of depolarization moving down the neuron
▫ this moving local reversal of voltage is called an
action potential
 an action potential follows an all-or-none law: a
large enough depolarization produces either a full
action potential or none at all
Neurons Generate Nerve Impulses
• The K+ voltage-gated channels open after a slight
delay, causing K+ to flow out of the cell
▫ this makes the interior of the neuron more
negative, causing the voltage-gated Na+ channels
to close
• The period of time after an action potential has
passed but before the resting potential is
restored is called the refractory period
Somatic System
• Nerves to/from
spinal cord
▫ control muscle
movements
▫ somatosensory inputs
• Both Voluntary and
reflex movements
• Skeletal Reflexes
Brain
Sensory
Neuron
▫ simplest is spinal reflex Skin receptors
arc
Motor
Neuron
Interneuron
Muscle
Autonomic System
• Two divisions:
▫ sympathetic
▫ Parasympatheitic
• Control involuntary functions
▫
▫
▫
▫
▫
heartbeat
blood pressure
respiration
perspiration
digestion
• Can be influenced by thought and emotion
Sympathetic
CENTRAL NERVOUS SYSTEM SYMPATHETIC
• “Fight or flight”
response
• Release adrenaline
and noradrenaline
• Increases heart rate
and blood pressure
• Increases blood flow
to skeletal muscles
• Inhibits digestive
functions
Brain
Dilates pupil
Stimulates salivation
Relaxes bronchi
Spinal
cord
Salivary
glands
Lungs
Accelerates heartbeat
Inhibits activity
Heart
Stomach
Pancreas
Stimulates glucose
Secretion of adrenaline,
nonadrenaline
Relaxes bladder
Sympathetic Stimulates ejaculation
ganglia
in male
Liver
Adrenal
gland
Kidney
Parasympathetic
CENTRAL NERVOUS SYSTEM PARASYMPATHETIC
Brain
• “Rest and digest”
system
• Calms body to
conserve and
maintain energy
• Lowers heartbeat,
breathing rate,
blood pressure
Contracts pupil
Stimulates salivation
Spinal
cord
Constricts bronchi
Slows heartbeat
Stimulates activity
Stimulates gallbladder
Gallbladder
Contracts bladder
Stimulates erection
of sex organs
Sensory Information sent to
opposite hemisphere
• Principle is Contralateral
Organization
• Sensory data crosses over
in pathways leading to the
cortex
• Visual Crossover
Left visual Right visual
field
field
Optic
nerves
▫ left visual field to right hemisphere
▫ right field to left
• Other senses similar
Left Visual Corpus Right Visual
Cortex Callosum
Cortex
Brain
• Your mind is a powerful and amazing organ. Its
ability to calculate, control and think exceeds
that of every computer on Earth put together.
• Your brain has three main parts.
▫ Cerebrum
▫ Cerebellum
▫ Brain Stem.
Cerebrum
• Largest portion of the brain
• Your cerebrum is responsible for all the
voluntary processes that you do each day,
including thought.
• Voluntary means that you want to do something,
or that you decide to do something, like hold
your hand in the air, wave to yourself, and tap
yourself on the head.
Cerebrum
• As you do these actions, your cerebrum sends
electrical messages out to your body using the
neurons of your nervous system.
• When the message reaches your arm, your
muscles obey, and do as they are instructed.
Cerebellum
• Your cerebellum aids your
cerebrum in the task of
moving your muscles.
• It helps to maintain balance,
moving the muscles you don’t
think to move, as you make
your arm wiggle around. This
allows you to move about
smoothly, with little effort.
Brain Stem
• Your brain stem sites at the
base of the brain, and
connects it to the spinal cord.
• The brain stem controls the
flow of information between
the brain and the rest of the
body, and also controls many
of the involuntary
movements that your body
does, every single day.
Localization of function
Frontal
Parietal
Occipital
Temporal
Occipital Lobe
Input from Optic
nerve
 Contains primary
visual cortex

 most
is on surface
inside central fissure

Outputs to parietal
and temporal lobes
Occipital
Lobe
Visual
Lobe
Temporal Lobe
 Contains primary
auditory cortex

Inputs are auditory, visual
patterns





speech recognition
face recognition
word recognition
memory formation
Outputs to limbic System,
basal Ganglia, and
brainstem
Auditory
Cortex
Temporal
Lobe
Parietal Lobe

Somatosensory
Cortex
Inputs from multiple
senses
 contains primary
somatosensory cortex
 borders visual &
auditory cortex
 Outputs to Frontal lobe
 hand-eye coordination
 eye movements
 attention
Parietal
Lobe
Frontal Lobe


Motor action/behavior
Contains primary
motor cortex
No direct sensory input
 Important planning and
sequencing areas
 Broca’s area for
organization/speech


Prefrontal area for
working memory
Frontal
Lobe
Working
Broca’s
Memory
Area
Motor
Cortex
Frontal Lobe Disorders
 Broca’s
area
productive aphasia--an acquired language disorder
affecting all modalities such as writing, reading, speaking, and
listening and results from brain damage
 Prefrontal
lose
area
track of ongoing context
fail to inhibit inappropriate responses
The Nervous System:
Summary

Major structures of the
nervous
 CNS,
Somatic, Autonomic
 Two hemispheres & 4 lobes

Organization
 contralateral
input & output
 primary sensory areas
 motor areas
 Commissure

Localization of functions
Central Nervous System
Peripheral Nervous System
Corpus Callosum
• What happens when the corpus
callosum is cut?
• Sensory inputs are still crossed
• Motor outputs are still crossed
• Hemispheres can’t exchange data
• Epileptic
The ‘Split Brain’ studies
• Surgery for epilepsy :
cut the corpus
callosum
• Roger Sperry, 1960’s
• Special apparatus
▫ picture input to just one side
of brain
▫ screen blocks objects on table
from view
Verbal
Nonverbal
left
right
hemisphere hemisphere
The ‘Split Brain’ studies

Picture to right
brain
 can’t
“What
“Using
“What
yourdid
left
did hand,
see?”
Pick you
up
you
what
see?”
you saw.”
name the object
 left
hand can identify
by touch
• Picture to left brain
▫ can name the object
▫ left hand cannot
identify by touch
??
I saw an
Verbal
Verbal
apple.
leftleft
Nonverbal
right
hemisphere
hemisphere
hemisphere
Super Highway
• Like a powerful broadband Internet connection, your
spinal cord can move a lot of data very quickly. Its job is
to carry messages to and from the body to the brain.
• There are 32 different nerves that connect directly into
the spinal cord, and that branch outward towards the
rest of the body.
• Reflexes are processed directly in the spinal cord,
allowing you to respond very quickly to danger, without
wasting time thinking about what you should do.
Addictive Drugs Act on Chemical
Synapses
• Emotional states (mood, pleasure, pain, etc.) are
determined by particular groups of neurons that
use special sets of neurotransmitters and
neuromodulators
▫ many researchers think that depression results
from a shortage of serotonin
▫ Prozac, an anti-depressant, inhibits the
reabsorption of serotonin
Drugs alter transmission of impulses
across the synapse
Addictive Drugs Act on Chemical
Synapses
• Nerve cells are particularly prone to the loss of
sensitivity when exposed to a chemical signal for
a long time
▫ if receptor proteins within synapses are exposed to
high levels of neurotransmitters for prolonged
periods, the nerve cell often responds by inserting
fewer receptor proteins into the membrane
Addictive Drugs Act on Chemical
Synapses
• Cocaine acts a neuromodulator, causing
abnormal amounts of neurotransmitters to
remain in the synapse for long periods
▫ it affect neurons in the brain’s pleasure pathways
 these cells transmit pleasure messages using the
neurotransmitter dopamine
▫ cocaine works by blocking transporter proteins on the
presynaptic membrane that normally reabsorb
dopamine
 because dopamine cannot bind to a transporter, it remains in
the synapse and continues to stimulate
Addictive Drugs Act on Chemical
Synapses
• When receptor proteins in the pleasure
pathways of the brain are exposed to high levels
of dopamine due to cocaine, the nerve cells
respond by lowering the number of receptor
proteins
▫ with so few receptors, the drug user needs the
drug to maintain even normal nerve activity levels
▫ this is addiction, the physiological adaptation of
the nervous system due to drug abuse
How drug addiction works
Addictive Drugs Act on Chemical
Synapses
• Nicotine, also an addictive drug, binds to
postsynaptic receptors in the brain that normally
bind to Ach
• The brain responds by
▫ making fewer receptors to which nicotine can bind
▫ altering the pattern of activation of the nicotine
receptors (i.e., their sensitivity to neurotransmitters)
• This leads to profound changes in the patterns of
release of many neurotransmitters, and
addiction results
How the Brain Works
• The cerebrum is the center for thought and
association and makes up about 85% of the
weight of the brain
▫ the cerebrum is divided into right and left halves,
called cerebral hemispheres
• Much of the neural activity of the cerebrum
occurs within a thin, gray outer layer called the
cerebral cortex
Senses
• We use our senses to get information about the world
around us into our brains.
• There are five main senses that most of us use each day.
▫ Sight
▫ Hearing
▫ Touch
▫ Taste
▫ smell
• Without senses, your brain would have no way of
knowing what was going on around you. Life would be a
very lonely, dark, and quiet place.
Eyes
• The human eye is an amazing
and powerful organ. As you read
the words on this screen, your
eyes see the shapes of the letters,
and transmit the information
back to your brain.
• Light travels from the computer
screen to your eyes, entering
them through a transparent layer
of tissue called the cornea.
Eyes
• The light of your computer screen then travels onward
through the lens. The lens of your eye focuses the light
onto a special tissue called the retina.
• The retina is lined with special photoreceptors called
rods and cones.
• Rods are more sensitive to light, but cannot distinguish
between colors.
• While cones are less sensitive, but can differentiate the
different colors, giving us color vision.
• Not all animals have cones. What does this mean? It
means that many animals see in black and white.
Eyes
• As light lands on the
rods and cones it is
converted into
electrical impulses and
is transmitted to the
brain, where it is
interpreted as the
beautiful images all
around us.
Sensing Light: Vision
• Color blindness occurs when individuals are
not able to perceive all three colors
▫ it typically occurs due to an inherited lack of one
or more types of cones
▫ it is a sex-linked trait, so men are more likely to be
colorblind than women
Test for color blindness
Sometimes your eyes can play
tricks on you…
Optical Illusion
• The brain also uses information learned in the
past to help it perceive the images that the eyes
send
• the brain can have a tendency to “force” an
image into something that the image is not, just
so the image looks more familiar. These are
called cognitive illusions
• optical illusion isn’t “real,” although the brain
interprets the illusion as being true
Hearing
• How do we hear?
• As objects move, or interact with other objects,
they cause the air to vibrate. Think of a
swimming pool.
• What happens if you jump in?
• First you make a big splash, followed by a series
of ripples. The harder you jump, the bigger your
ripples will be.
Hearing
• The air of our atmosphere works in much the
same way as a swimming pool.
• Even though we cannot see the ripples, every
time, we move they go traveling through the air.
• Some of these ripples, or vibrations reach our
ears. Inside of your ear is a thin tissue known as
the tympanum, or eardrum.
Hearing
• The vibrations in the air cause your eardrum to
begin vibrating.
• Behind your eardrum are three tiny bones called
• Hammer
• Anvil
• Stirrup
Hearing
• As your eardrum begins to vibrate, so do these
tiny bones.
• The last of these bones, the stirrup transmits
these vibrations into the fluid filled cochlea.
• This causes tiny hairs within the cochlea to
vibrate.
• The vibration of these hairs is converted into
electrical impulses, which are then transmitted
to the brain for interpretation.
Taste and Smell
• The senses of taste and smell are interpreted
from tiny objects on your tongue, and in your
nose.
• Receptors within your nose detect and transmit
smells to your brain, while your taste buds detect
and transmit flavors to your brain
Taste and Smell
• Much of what we think we are tasting is actually
smell.
• Try an experiment. Next time you are eating
something, plug your nose. What happens?
• Much of the flavor disappears.
Touch
• The senses we have discussed so far have been
located in one specific location, such as the eye,
or nose.
• However, your sense of touch is not restricted to
one small area, but covers your entire body.
• Your skin is sensitive to heat, to pressure, and to
pain.
• Within your body, there are also many nerve
endings that are sensitive to touch.
Things to keep your mind moving…
• Leave your comfort zone. Getting good at
sudoku? Time to move on. Brain teasers don't
form new neural connections once you've
mastered them. So try something that's opposite
your natural skills: If you like numbers, learn to
draw. If you love language, try logic puzzles.
• Curry up. The active ingredient in Indian
curry, turmeric, contains resveratrol, the same
powerful antioxidant that makes red wine good
for brain health. Eat curry once a week, or
sprinkle it on salads, to protect brain cells from
harmful free radicals.
• Redecorate and redesign your
environment. Plant new flowers in front of
your house. Redecorate the kitchen. Rearrange
your closets and drawers. Replace the candles in
your living room with some that have a different
scent. Making such changes can alter motor
pathways in the brain and encourage new cell
growth.
• Sleep. Shut-eye isn't a luxury. It's when your
brain consolidates memories. Poor sleep, caused
by medical conditions, worry, depression, or
insomnia, can interfere with your rest. So treat
yourself to relaxing scents like vanilla before
bed. They raise the chemical dopamine and
reduce cortisol, a stress hormone.
• Play Games Whether you choose Risk,
Pictionary, Scrabble, Sudouku, Wii, XBOX or
Boggle, games are associated with a lower risk of
developing dementia.
• They activate strategic, spatial, and memory
parts of the brain, and require you to socialize,
which can help form new neural pathways.
• Switch hands. It may be uncomfortable, but
writing with your nondominant hand or
operating a computer mouse with that hand can
activate parts of the brain that aren't easily
triggered otherwise.
• Anything that requires the brain to pay close
attention to a formerly automatic behavior will
stimulate brain-cell growth.