Nervous System
Regulates all body activities,
learning and memory.
How do you think nerve impulses travel along neurons?
Neurons: carry nerve impulses by way of electrical charges and
chemical reactions.
Nerve Cell
washington.edu
Axon
Dendrite
•Take Information away from
the cell body
•smooth surface
•Bring information to the cell
body
•Rough surface
•generally only 1 axon per cell
•Usually many dendrites per cell
body
•No ribosomes
•Have ribosomes
•Can have myelin
•No myelin insulation
•Branch further from the cell
body
•Branch near (close to) cell body
o MYELIN acts as a short cut—shortens
the time it takes for the impulse to
travel
daviddarling.info/encyclopedia/M/myelin.html
mtsinai.on.ca/EBFFRC/MS/default.htm
How it all works!
emc.maricopa.edu/faculty/farabee
more of
K+ inside
Na+ outside
•The inside of the neuron
is negatively charged
relative to the outside
•When Na+ enters the
neuron the charge
becomes positive and the
action potential begins
ucl.ac.uk/~sjjgsca/NerveActionPotential.html
at the synapse NEUROTRANSMITTERS carry
the signal to the next neuron, muscle, etc.
http://psychedelic-information-theory.com/neuron_bw
o once in motion the ACTION
POTENTIAL keeps the impulse
moving as K+ and NA+ switch
places all along the axon to the
SYNAPSE
•As the nerve impulse
travels along the axon
the charge inside the
axon changes from
negative to
positive
neugrowth.com/
Synapses…
What is happening?
nerve impulse
1. The action potential reaches the axon terminal
electric current transmits signals
1. As Ca+ enters.
2. Synaptic vesicle fuses with the plasma membrane
of the sending neuron.
3. Neurotransmitter molecules are released and bind
to receptors of receiving neuron.
4. Na+ diffuses into the receiving neuron.
All or None
• Depolarization and repolarization is known as
action potential
• once the threshold is reached… action
potentials are “all or nothing”. The intensity
of an action potential does not diminish as
depolarization spreads along the axon.
Threshold Potential
http://quizlet.com
Interesting Facts
• Neurons are the oldest and longest cells in the body!
You have many of the same neurons for your whole
life. Although other cells die and are replaced, most
neurons are never replaced when they die. In fact,
you have fewer neurons when you are old compared
to when you are young.
• Neurons can be quite large - in some neurons, such
as corticospinal neurons (from motor cortex to spinal
cord) or primary afferent neurons (neurons that
extend from the skin into the spinal cord and up to
the brain stem), can be several feet long!
How many neurons?
• 100,000,000,000 in the human brain
• Rate of neuron growth during
development of a fetus=
250,000 neurons/minute
• 100,000,000,000 neurons x 10 microns=
1000 km or about 600 miles!
Types of Neurons
• Sensory Neurons– Pick up sensory information from the sense organs and relay the
information to the interneurons.( brain and spinal cord)
• Interneurons– Relay information from sensory neurons to motor neurons .
• Motor Neurons– Stimulate muscles or glands in effect or organs to cause a
response.
Neuroglia
The Nervous System
Central Nervous System
brain & spinal cord
Peripheral Nervous system
everything else
nerves and ganglia that lie outside the CNS. (spinal nerves,
cranial nerves, ganglia, motor and sensory neurons.)
Sensory Neuron
Pick up sensory information from the sense organs and relay the
information to the interneurons.( brain and spinal cord)
Interneuron
Relay information from sensory neurons to motor neurons .
Motor Neuron
Stimulate muscles or glands in effector organs to cause a response.
Two Types of Motor Neurons
Somatic - voluntary - skeletal muscles
Autonomic - involuntary - smooth muscles, cardiac
muscle, and glands
Autonomic Nervous
Sympathetic - Fight or flight
Parasympathetic - sleep or snack
Central Nervous System
• Brain
Cerebrum
• CEREBRUM is the largest part of the brain.
• It takes care of conscious movement and
thought.
• It’s two hemispheres
are joined by the
CORPUS CALLOSUM

WRINKLES provide more surface area
Each hemisphere controls the opposite side of the body
Cerebellum
• CEREBELLUM is found below and to the back
of the cerebrum.
• It coordinates commands
from the cerebrum.
• This action is involuntary
Thalamus and Hypothalamus
• Relays sensory input to
the right places in the
Cerebrum
• Maintains Homeostasis
• hunger,thirst, body
temp, sleep, H20,
balance and blood
pressure
Brain Stem
• Coordinates and serves as port for
coming/going info
• regulates heart rate and respiration
Spinal Cord
•links the brain and PNS
•stimulates reflexes
SPEEDY REVIEW
Structures of PNS
SENSORY NEURON ~ senses stimulus and
alerts CNS
Gets its info from a RECEPTOR ORGAN
INTERNEURON ~ w/i CNS, tells brain what’s
going on
MOTOR NEURON ~ takes info from CNS and
initiates a reaction in the EFFECTOR ORGANS
GANGLIA ~ a group of neural cell bodies
that is found outside of the CNS (w/i the PNS)
Receptor organs
make up all our senses
(excepting ESP)
 Sight—eyes, rods and cones
 Hearing & balance—ears, eardrums &
bones & and semicircular canals
 Smell—nose, olfactory nerves
 Taste—tongue, taste buds
 Touch (heat/cold, pressure, pain)—
receptors in skin