Transcript Nervous System - We Heart Science

Nervous System
Young Woman or Old?
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That depends on your
interpretation. Young
people tend to see a
young girl; older people,
an elderly lady. With
effort, you can switch
from one to the other:
the young woman's chin
becomes the old
woman's nose; the old
woman's mouth, a band
on the neck of the
young woman.
Words and Colors
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Read the image aloud-but rather than reading
the words, say the color
of the ink that was used
to write each word. It's
not easy; the written
words have a
suprisingly strong
influence over the
actual color.
Faces or Vases?
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The answer depends on
what you perceive as
the background--the
black spaces or the
white. Photographer
Zeke Berman has
created this intriguing
collage using
silhouettes of real
people. "Goblet
Portraits" by Zeke
Berman ©1978
Do you see the Phantom Spots?
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You may see spots where the white lines intersect,
but if you try looking right at one, it will disappear.
The spots, of course, aren't really there. They're
caused by the way your eyes respond to light and
dark areas. When an area is surround by light, your
eye compensates by "turning down" the brightness a
bit, making you see darkened blobs. In this grid, the
areas surrounded by the most white are at the
intersections of the white lines. Since this
phenomenon works best in your peripheral vision, the
spots disappear when you look right at them.
VISUAL ACUITY:
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A person who has
sufficient visual
acuity should see
the number twelve
in the circle on the
left whether or not
they have normal
color vision.
COLOR BLINDNESS:
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A person with
normal color vision
sees a number
seven in the circle
on the left. Those
who are color blind
usually do not see
any number at all.
RED-GREEN
COLORBLINDNESS
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People with redgreen color
blindness see either
a three or nothing at
all. Those with
normal color vision
see an 8.
PROTANOPIA &
DEUTERANOPIA
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Those with normal
vision see the number
thirty-five in the circle
above. A person with
protanopia sees only he
number five. A person
with deuteranopia sees
the number three.
People who are partially
color blind will see both
numbers but one more
distinctly than the other.
Test for Macular Problems:
Amsler Grid
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Make sure your room
lights are on. Put on
your reading glasses if
you wear them, and test
each eye separately
(cover one eye at a
time). Concentrate on
the center spot . If the
lines appear wavy, or if
their are spots or holes
in the grid, then you
may have a macular
problem
Complimentary Colors:
• Study complimentary colors using the
ExploreSciences shockwave experiment.
With one eye covered, stare at the center
of the diagram below with the other eye for
30 seconds. Then click on the flag and see
what you see with the same eye (keep the
other one covered.)
Complimentary Colors
Nervous systems
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Nerves~ bundles of
neurons wrapped in connective
tissue
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Central nervous
system (CNS)~ brain
and spinal cord
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Peripheral nervous
system (PNS)~
sensory and motor neurons
Structural Unit of Nervous System
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Neuron~ structural and functional unit
Cell body~ nucelus and organelles
Dendrites~ impulses from tips to neuron
Axons~ impulses toward tips
Myelin sheath~ supporting, insulating layer
Schwann cells~PNS support cells
Synaptic terminals~ neurotransmitter releaser
Synapse~ neuron junction
Simple Nerve Circuit
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Sensory neuron: convey information to
spinal cord
Interneurons: information integration
Motor neurons: convey signals to
effector cell (muscle or gland)
Reflex: simple response; sensory to
motor neurons
Ganglion (ganglia): cluster of nerve cell
bodies in the PNS
Supporting cells/glia: nonconductiong
cell that provides support, insulation,
and protection
Reflex Action
1.
2.
3.
A sense neuron is
stimulated
The cell body
sends a signal to
the axon and then
to an interneuron
The signal then
goes to the brain
4. The brain sends a
signal to the motor
neuron
5. The motor neuron
causes the muscle
to contract
Sensory neurons, interneurons,
and motor neurons
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The pathways of
impulses from
dendrite to cell body
to axon of sensory
neurons,
interneurons, and
motor neurons link
the chains of events
that occur in a reflex
action.
Similar paths of neural
connections lead to the
brain, where the sensations
become conscious and
conscious actions are
initiated in response to
external stimuli. Students
might also trace the path of
the neural connections as
the sensation becomes
conscious and a response to
the external stimulus is
initiated. Students should
also be able to identify gray
and white matter in the
central nervous system.
Neural signaling, I
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Membrane potential (voltage differences across the plasma membrane)
Intracellular/extracellular ionic concentration difference
K+ diffuses out (Na+ in); large anions cannot follow….selective
permeability of the plasma membrane
Net negative charge of about -70mV
Transmission of Nerve
Impulses
– Transmission of nerve impulses involves
an electrochemical “action potential”
generated by gated ion channels in the
membrane that make use of the
countervailing gradients of sodium and
potassium ions across the membrane.
– Potassium ion concentration is high inside
cells and low outside; sodium ion
concentration is the opposite.
Nerve Impulses continued
– The sodium and potassium ion
concentration gradients are restored by an
active transport system, a pump that
exchanges sodium and potassium ions
across the membrane and uses ATP
hydrolysis as a source of free energy.
– The re-lease of neurotransmitter chemicals
from the axon terminal at the synapse may
initiate an action potential in an adjacent
neuron, propagating the impulse to a new
cell.
Multiple Sclerosis
Is a disease of the nervous system
 It is caused by hardening of the myelin
sheath of the axons
 Due to the hardening of the axons the
nerve impulse travels slower
 Symptoms include weakness, loss of
coordination, problems with vision and
speech
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Neural signaling, IV
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“Travel” of the action potential is self-propagating
Regeneration of “new” action potentials only after refractory period
Forward direction only
Action potential speed:
1-Axon diameter (larger = faster; 100m/sec)
2-Nodes of Ranvier (concentration of ion channels); saltatory conduction;
150m/sec
Synaptic communication
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Presynaptic cell: transmitting cell
Postsynaptic cell: receiving cell
Synaptic cleft: separation gap
Synaptic vesicles: neurotransmitter
releasers
Ca+ influx: caused by action
potential; vesicles fuse with
presynaptic membrane and
release….
Neurotransmitter
The cellular and molecular basis
of muscle contraction
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Controlled by calcium ions and powered by
hydrolysis of ATP, actin and myosin filaments in a
sarcomere generate movement in muscles.
Striated muscle fibers reflect the filamentous
makeup and contraction state evidenced by the
banding patterns of those fibers. A sketch of the
sarcomere can be used to indicate the functions of
the actin and myosin filaments and the role of
calcium ions and ATP in muscle contraction.
Neurotransmitters
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Acetylcholine (most common)
•skeletal muscle
Biogenic amines (derived from amino acids)
•norepinephrine
•dopamine
•serotonin
Amino acids
Neuropeptides (short chains of amino acids)
•endorphin
Vertebrate PNS
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Cranial nerves (brain origin)
Spinal nerves (spine origin)
Sensory division
Motor division
•somatic system
voluntary, conscious control
•autonomic system
√parasympathetic
conservation of energy
√sympathetic
increase energy consumption
The Vertebrate Brain
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Forebrain
– •cerebrum~memory, learning,
emotion
– •cerebral cortex~sensory and motor
nerve cell bodies
– •corpus callosum~connects left and
right hemispheres
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– •thalamus; hypothalamus
Midbrain
•inferior (auditory) and superior
(visual) colliculi
Hindbrain
•cerebellum~coordination of movement
•medulla oblongata/ pons~autonomic,
homeostatic functions