Download 2-3 nervous sys Sp13

Bio11:
The Nervous System
Body control systems
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Nervous system
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Endocrine system
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What parts of your brain are you
using right now?
Frontal lobe
x
orcy
or
te
x
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ns
Moto
rco
r te
Somat
ose
area
Senses;
reading
Work together to regulate body
activities
Speech Somatosensory
association
area
Reading
Taste
The brain processes
and acts on
information
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Each of the Speech
four lobes has distinct functions
Hearing
Smell
Auditory
association
area
Hearing and smell
Temporal lobe
Visual
association
area
Vision
Sends a hormone as a messenger to
the target organ
Can target several organs
Slower acting
Longer lasting response
The human brain
Parietal lobe
Movement and
conscious
thought;
Frontal
speech
association
Quick
Sends message directly to target
organ
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Vision
It receives information
from nerves and the
spinal cord
integrates it
and generates the
appropriate response.
Occipital lobe
Figure 27.12
The human brain
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Cerebrum – largest part of
the brain
Central processing center
where learning,
remembering and
reasoning takes place
The cerebral cortex
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a highly folded layer of tissue
that forms the surface of the
cerebrum
The Cerebrum
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Cerebrum
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Right and left cerebral
hemispheres
Connected by the corpus
callosum
Are you left-brained or rightbrained?
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Right = artistry
Left = logic
Little about life is that clear
and distinct. The traits
associated with each side of
the brain are matters of
degree
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White matter:
the brain’s connections
The Cerebrum
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Gray matter
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makes up the cerebral
cortex
mainly cell bodies and
nonmyelinated (naked)
axons and dendrites.
White matter
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Myelinated axons that
connect neurons in
different regions of the
cerebral cortex
MRI scan
The brain: Cerebellum
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Coordinates basic
movements:
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Maintains posture and
balance
Essential for motor
coordination and precision.
Learns and remembers new
motor skills (tying a shoe,
playing the piano or hitting a
baseball)
The brain stem
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The central
nervous system
(CNS)
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Breathing
Heart rate
Temperature control
Brain stem
What protects the CNS?
The Central Nervous System
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Connects the brain to
the spinal cord
Controls basic body
functions:
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brain
spinal cord
Bone and protective
membranes called the
meninges
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a series of 3 coverings
between the nervous
tissue and bone
Spaces filled with
cerebrospinal fluid
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Liquid shock absorber
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Cerebrospinal fluid provides a
constant environment
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CSF protects the brain
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Superhighway for
nerve impulses
traveling between
the brain and rest of
body
Vertebra protect the
spinal cord
Signal
direction
astrocyte
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Protects the brain from bacterial
and viral infections
Glucose is actively transported
across the barrier
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Neurons are unique cells
Direction of
Signal
Movement
nerves
Structure of a neuron
Signal
direction
Dendrites
Cell
body
Separates the circulating blood
from the brain CSF
Tight junctions around the
capillaries restrict the entry of
bacteria and large molecules
into the cerebrospinal fluid
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Cushions the brain
Prevents the fragile
surface of the brain from
striking the skull
Maintains consistent
chemical environment
Allows the brain to be
bathed in CSF rather than
blood, to avoid bloodborne infection
Spinal cord relays information
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Blood-brain barrier
Direction of electrical signal:
Dendrite → cell body → axon
Can be many feet in length!
Conduct electrical signals
Dendrites, Cell Body, Axon
Dendrites
Cell
body
An axon ends in a cluster
of branches, each with a
bulb-like synaptic
terminal that relays
signals to
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Axon
Supporting cell
Signal
pathway
Axon
Synaptic
terminals
Supporting cell
Another neuron
A muscle
Signal
pathway
Synaptic
terminals
Nucleus
Nucleus
Myelin sheath
Forms insulating material around an axon
Increases the speed of the electrical signal
Myelin sheath
Figure 27.2
3
Types of neurons
Bring messages into
brain/spinal cord
SENSORY INPUT
Sensory receptor
Sensory
neuron
INTEGRATION
SENSORY INPUT
Sensory
neuron
Sensory receptor
Interneuron
MOTOR OUTPUT
Motor
neuron
Effector cells
Types of neurons
MOTOR OUTPUT
Motor
neuron
Brain and spinal cord
Peripheral nervous
system (PNS)
Central nervous
system (CNS)
Effector cells
Types of neurons
Peripheral nervous
system (PNS)
INTEGRATION
Interneuron
Transfer
Brain and spinal cord
messages within
brain/spinal
cord
Central nervous
system (CNS)
Nerves
SENSORY INPUT
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Sensory receptor
Sensory
neuron
INTEGRATION
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Interneuron
MOTOR OUTPUT
“Cables” or bundles
of axons
Extend from the
CNS to various parts
of the body.
Motor
neuron
Effector cells
Take messages
Brain and spinal cord
from brain/spinal
cord to muscles or
Peripheral nervous
Central nervous
glands
system (PNS)
system (CNS)
The other brain cells
(Neurons are not alone)
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Neurons
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Neuron
carry electrical signals
100 billion in brain
Myelin sheath
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Glia
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Trillions of support cells
Several different types
of glia cells help
optimize brain function
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Insulates axons
Covering formed by a
type of glia called
Schwann cells
Cells wrap themselves
around the axon
several times
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What happens if the myelin
sheath is damaged?
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Nerves no longer
conduct impulses
normally
Multiple sclerosis
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Central Nervous
System (CNS)
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Inflammatory
disease that destroys
the myelin sheath
The brain
Spinal cord
Peripheral nervous
system
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All nervous tissue outside
the CNS
MS “short circuits”
the nervous system
Peripheral Nervous System:
sensory and motor nerves
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The nervous system has two
parts
Sensory nerves bring
info from the body to
the CNS
Information is
integrated by
interneurons in brain
and spinal cord
Response
PNS: motor nerves
Other nerves serve muscles and glands
But not skeletal muscle
Controls “automatic”
functions of the body’s
internal organs
Involuntary
Autonomic Nervous System
Peripheral Nervous System
Voluntary
Carries signals to
and from skeletal
muscles
Involuntary
Fight or flight
Neurons work by carrying
electrical signals
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Neurons are
specialized for
carrying electrical
signals from one
part of the body to
another
axon
cell body
Rest and digest
Controls smooth and cardiac
muscles, organs and glands
dendrites
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The electrical signals are
called action potentials
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An action potential
is a brief change in
electrical charge at a
membrane
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When a neuron
“fires”, the charge
across the neuron’s
membrane suddenly
reverses polarity
Action potentials are
“all or nothing” events
axon
cell body
dendrites
http://www.youtube.com/watch?v=R0TdXkxBOkE&NR=1
Action potentials spread down
the axon
What happens when a neuron
“fires”?
Outside Cell
Inside Cell
At rest, the Na+
When the neuron fires,
channels are closed. the Na+ channels
Inside of cell has
open
negative charge
Electrical currents involve movement
of charged (+ or -) particles
Analogy:
Power Plant Creates Charge
Power Lines Move that Charge
(electrical current)
To Your House
Signal is propagated down
the axon like an electrical
current down a wire
How is the action potential
passed to the next cell?
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Particles don’t move much, they hand
their charge off to the next particle
What happens at the Synapse?
Electrical  Chemical  Electrical
Electrical signals can’t cross
the gap between two neurons
or synapse
The signal is transmitted by
chemicals called
neurotransmitters
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Stored in vesicles at the end
of the axon
Bind to receptors on the next
cell
Neurotransmitters
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Synaptic
terminal of
sending
neuron
Neurotransmitters
Dendrite of
receiving neuron
SYNAPSE
Sending neuron
Action
potential
arrives.
Vesicles
Synaptic
terminal
What happens
after the action
potential is passed
to the next
neuron?
Neurotransmitter
Receptor
Ions
Vesicle fuses
with plasma
membrane.
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More than 100 small molecules
Either excite or inhibit the receiving neuron
Most widely studied
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Acetylcholine (ACh), norepinephrine (NE), dopamine, serotonin,
and GABA
Neurotransmitter
is released into
synaptic cleft.
Synaptic
cleft
Receiving
neuron
Ion channels
Neurotransmitter
molecules
Neurotransmitter
binds to receptor.
Ion channel opens and
triggers or inhibits a
new action potential.
Ion channel closes.
Neurotransmitter is
broken down and
released.
Dendrites
Myelin
sheath
Receiving
cell body
Axon
Synaptic
terminals
Neurons
integrate
many
signals
Neurons and how they work 4:43
http://www.youtube.com/watch?v=FR4S1BqdFG4&feature=endscreen&NR=1
SEM
A neuron may
receive input from
hundreds of other
neurons via
thousands of
synaptic terminals
Recap: How neurons work
How do motor nerves control
muscle contraction?
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Motor neurons carry
nerve impulse to a
muscle fiber
Neurotransmitter
ACh is released,
diffuses across the
synapse and binds to
receptors on muscle cell
Muscle fiber contracts
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