Transcript Nervous System PPT

Why Do Animals Need a Nervous System?
• Because the world
is always coming at
you!
Many animals have nervous tissue, but mammals have the
most organized and efficient nervous system.
Nervous System
• Central nervous system
– brain & spinal chord
• Peripheral nervous
system
– nerves from senses
– nerves to muscles
cerebrum
cerebellum
spinal cord
cervical
nerves
thoracic
nerves
lumbar
nerves
femoral
nerve
sciatic
nerve
tibial
nerve
Nerve Cells
• Neuron
– building blocks of the nervous system
– sends signals so your body can respond to the
environment
Labeling A Nerve Cell
1. Cell Body
2. Nucleus
3. Dendrites
9. Terminal branch
4. Axon
7. Node of Ranvier
5. Schwann cell nucleus
6. Schwann cell
10. Synaptic knobs
8. Myelin Sheath .
Fun Facts about Nerve Cells
• Most specialized cell in
animals
• Longest cell
– blue whale neuron
• 10-30 meters
– giraffe axon
• 5 meters
– human neuron
• 1-2 meters
Nervous system allows for
1 millisecond response time
Myelin Coating
• Axon coated with insulation
made of myelin cells
– controls speed of signal
• signal hops from node to node
myelin coating
Multiple Sclerosis
 immune system (T cells) attacks myelin coating
 loss of signal
Synapse
• Junction between nerve cells
– Can be electrical or chemical
Each axon may have
synapses with up to 1000
other neurons
Synapse
• A chemical synapse
involves release of a
neurotransmitter.
• Neurotransmitters are
removed from a synapse
by enzymes, or they are
reabsorbed from the presynaptic neuron.
• This is where drugs effect
the system.
Reflexes
• Now that we know about neurons…how
do they work in the system as a whole?
• They work by reflexes, or automatic
response
Sensory Neuron - RECEPTORS
• Sensory Neuron neurons activated by
sensory input (vision,
touch, hearing, etc.),
which send external
stimuli to the central
nervous system
• A receptor is a structure
which receives
something
Interneuron
• A neuron that forms
a connection
between other
neurons.
• These neurons
receive signals in the
brain and spinal cord.
Motor Neuron - EFFECTORS
• Neurons that receive signals
from the brain to perform motor
functions.
– Movement
– Twitch
– Run/Walk/Etc
• The effectors are the
organs which respond to
the signals
sensory neuron
(from senses)
interneuron
(brain & spinal cord)
motor neuron
(to muscle)
Simplest Nerve Circuit
• Reflex, or automatic response
rapid response
 automated
 signal only goes to
spinal cord
 no higher level
processing
 advantage
 essential actions
 don’t need to think or
make decisions about
 blinking
 balance
 pupil dilation
 startle

Testing Your Reflexes - Video
Nerve Potential
• Nerve cells use IONS to function.
Nerve Potential
• Membrane Potential – difference in electrical
charge (caused by ions) across cell membrane.
• How many ions on each side?
• Action Potential – causes a nerve impulse –
uses ions
• Resting Potential – membrane potential of a
neuron at rest, neuron not working – but can
when needed (all or none response).
Human Brain
Primitive Brain
• The “lower brain”
– medulla oblongata
– pons
– cerebellum
• Functions
– basic body functions
• breathing, heart, digestion, swallowing,
vomiting
People in
– homeostasis
– coordination of movement
“vegetative” states
only use their
primitive brain.
Higher Brain
• Cerebrum
– 2 hemispheres
– left = right side of body
– right = left side of body
• The right side of your brain
perceives and controls the
left side of your body
• Left side of brain perceives
and controls right side of your
body
Higher Brain
• Corpus callosum
– connection
between 2
hemispheres
– When your corpus
callosum is severed,
you can use each half
of the brain
independently
These two sides work
together. It’s difficult to use
only one side of the brain.
For example: Have your
right hand tap your head
while your left hand rubs
your stomach
Division of Brain Function
• Left hemisphere
– “logic side”
– language, math, logic
operations, vision & hearing
details
– fine motor control
• Right hemisphere
– “creative side”
– pattern recognition, spatial
relationships, non-verbal
ideas, emotions, multi-tasking
Activity – Left or Right Test
• Clockwise = Right
Dominant
• Counter-Clockwise =
Left Dominant
• Lets take a Paper Test
to see if this is
TRUE…
Cerebrum Specialization
• Regions specialized for different functions
• Lobes
parietal
frontal
– frontal
• speech,
control of emotions
– temporal
• smell, hearing
– occipital
• vision
– parietal
• speech, taste
reading
temporal
occipital
Limbic System
Controls basic emotions (fear, anger), involved in emotional
bonding, establishes emotional memory
Memory Loss and
Amnesia is due to
Limbic System
Damage
Speaking of Memory….
• Do you really pay attention? How much
stuff do you miss when you think you’re
observing carefully…
The Ear
• Your ears convert sound waves into electrical signals
that are interpreted by your brain
• The cochlea is the auditory portion of the inner ear. It is
shaped like a snail shell.
• Bones of the ear:
– Anvil
– Hammer
– Stirrup
The Eye
• Eyes enable us to see in color and to distinguish fine details and
movement.
• The retina is the lining on back inner surface of the eye – consists of
photoreceptors.
• The optic nerve exits the back of the eye and connects in the brain
to the thalamus. It contains many neurons that process visual
information.
•
– Rods - respond to dim light and black and white shading.
– Cones- respond to bright light and enables the sight of the
colors.
The Eye
Lens
Cornea
Iris
Pupil
The Tongue