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Nervous System RQ
1.
2.
3.
4.
What does white matter have that gray
does not?
Which two ions are necessary for nerve
impulse transmission?
Your senses of taste and ______ are
received by chemical receptors.
Which class of drugs slows the CNS?
1. What is the basic unit of the nervous system? List and
describe the three main categories.

1.
2.
3.
A “neuron”, or nerve cell is the basic unit
Sensory neurons: carry impulses from the
body to the brain & spinal cord
Interneurons: found within the brain &
spinal cord; process impulses & pass
response impulses to motor neurons
Motor neurons: carry response impulses
away from the brain or spinal cord to a
muscle or gland 
2. How many categories of neurons are there,
and what are their jobs?
3. How does your nervous system
relay an impulse?


Impulses (messages) travel electrically
within a neuron, and chemically between
neurons
Sensory information  sensory neurons 
spinal cord  brain  motor neurons 
movement/reaction
4. Describe a neuron at rest.

Neurons have three parts:




Dendrites – receive impulses from other
neurons
Cell body – process the impulses
Axon – send impulses to other neurons, muscles
or glands
At rest:

The neuron is “polarized” with higher [K+] inside
the membrane and higher [Na+] outside of the
membrane 
5. How is an impulse transmitted?
1.
2.
3.
A stimulus excites a neuron and Na+
channels in the cell membrane open & Na+
rushes in
This depolarizes the cell (which was
negatively charged compared to it’s
surroundings)
This depolarization travels down the axon
to the next neuron 
6. What is the difference between the
white and gray matter?

White matter (much of the brain & spinal cord)



Axons that have “myelin” insulating the plasma
membrane
Myelin hinders the movement of ions, which
move fast down the axon’s length (increasing
the speed of reactions
Gray matter (interior of brain)

Neurons whose axons are not myelinated 
7. Describe the connections
between neurons.
1.
2.
3.
The space between the axon of one
neuron and the dendrite of the next
neuron is called a synapse
Neurotransmitters are the chemicals
that diffuse across the synapse to link
neurons
Enzymes break down the
neurotransmitters after the impulse is
relayed 
8. How do the central and peripheral
nervous systems work together?

Central (CNS) – the brain & spinal cord



Coordinates all of your body’s activities
Receives & processes info from the PNS
Peripheral (PNS) – everything else

Senses the environment and with direction
from the CNS responds to that environment 
9. Overview the anatomy of the brain.
Cerebrum
1.



Two connected hemispheres
Controls conscious activities, language, skeletal muscles &
senses
It is folded and groovy to increase surface area
Cerebellum
2.


Back of your brain, all foldy looking
Controls balance, posture, coordination
Brain stem
3.



Made up of medulla oblongata, pons, and midbrain
MO controls involuntary stuff like breathing & heart rate
Pons & midbrain connect the different parts of the brain 
10. What does your peripheral
nervous system do?
PNS carries impulses to the CNS and
performs the reaction necessary (sensory 

interneuron  motor)
Two divisions:

1.
2.
Somatic NS
Autonomic NS 
11. Describe the somatic nervous
system and what it does.


Made up of 12 pairs of cranial nerves and
31 pairs of spinal nerves, all bundled
together
Usually in charge of voluntary reactions to
stimuli, like skeletal muscle movement

Exception: reflexes (next slide) 
12. What are reflexes?




Occur within the somatic NS
It is an automatic, unconscious response to
a stimulus
The sensory information goes to the spinal
cord or brain stem and is immediately
dealt with; the cerebrum gets the
information after the reflex has occurred
Why would this happen? 
13. Your autonomic nervous system is divided into two
parts. Name them and describe what they do.


In charge of the involuntary reactions (not
under conscious control)
Sympathetic NS



Control during stress
Causes the release of epinephrine &
norepinephrine that causes “fight or flight”
Parasympathetic NS


Controls during rest
Calms you down after stressful situations 
14. Describe the chemical senses
of smell and taste.

Smell



The chemical receptors in your nose are hairlike nerve
endings that signal the brain about certain chemicals
The brain processes this information as a particular
smell
Taste

Chemicals dissolve in saliva and contact the taste buds
(sensory receptors)


You have about 10,000 taste buds
Tastes are sour, sweet, bitter, salty, and most recently
umami (MSG) and fat! 
15. Describe the anatomy of an eye and
how this allows you to see.
Retina: thin layer of tissue at the back of
the eye that has light receptors and
sensory neurons

Rods  cells adapted to see in dim light

Cones  adapted for bright light & colors
Light enters through the pupil
It is focused by the lens
The focused picture strikes the retina which
comes together to form the optic nerve, which
sends the information to the back of the brain


1.
2.
3.
16. How are your senses of hearing and balance
related? What structures are associated?
Both are examples of how we sense mechanical stimulation

Both use structures of the ear
Hearing
1.
Sound causes vibrations (sound waves) which strike the
tympanic membrane
2.
These vibrations cause the middle ear to vibrate, and this
vibration travels along, deeper into the ear
3.
Vibration reaches the fluid in the cochlea which causes the
hair cells (sensory receptors) to produce electric impulses
4.
These travel along the auditory nerve to the brain where
the sound is interpreted
Balance
1.
Fluid-filled semicircular canals in the inner ear are lined
with hair cells also
2.
When you tilt your head it bends the hairs sending the
impulse to your brain 

17. How does your sense of touch work? Describe
what kinds of receptors your body has.


Sensory receptors in the dermis respond to
mechanical stimuli
Temperature



Pressure



Heat receptors are deep in the dermis
Cold receptors are close to the surface
Light pressure sensors found especially in the
fingertips, palms, eyelids, lips, and tip of the tongue
Heavy/deep pressure sensors found in muscle, joints,
some organs, palms and soles of feet
Pain (nocireceptors)

Found everywhere except brain 
18. What is a drug? How does it interact in
the brain or endocrine system?


Drug – any chemical that affects the
body’s functions
Most interact with neurotransmitter or
hormone receptors on cells 
19. How do pain relievers work on your body?
What is an example?

Two ways pain relievers (analgesics) work:
1.
2.
Inhibit the receptors that initiate the pain
impulse (ex: aspirin)
Narcotics manipulate the CNS that receives the
impulses (ex: opiates) 
20. Describe how drugs can also be used to
treat circulatory and nervous disorders.

Cardiovascular drugs…






High blood pressure (norvasc, lopressor)
Normalize heartbeat (Diltiazem)
Increase pumping capacity
Enlarge small blood vessels
Prevent blood clots (heparin, coumadin, warfarin)
Nervous disorders…

Stimulants (amphetamines)


Increase wakefulness and alertness
Depressants (sedatives)

Encourage calmness and sleep; reduce anxiety 
21. What happens when people misuse drugs? How do
addiction, tolerance, and withdrawal fit into
this?


Can cause death 
Misuse…




Taking someone else’s prescription
Not taking the drug as prescribed
Mixing contraindicated medicines
Abuse…


The inappropriate use of a drug for non-medical
purposes
Can be illegal or excessive use of legal drugs 



Addiction – when a person psychologically
needs a drug to function normally; or when
a person’s body has developed a chemical
need for a drug
Tolerance – when a person needs more and
more of a drug to get the same effect
Withdrawal – when a person stops taking
the drug and becomes ill 
22. Briefly describe stimulants, depressants, narcotics and
hallucinogens. How do these different classes of drugs
affect the body?

Stimulants: increase CNS activity



Depressants: slows down the CNS activity




Alcohol & barbiturates
Relieve anxiety, produce sedation
Can cause brain damage and liver cirrhosis; reduced
circulatory and respiratory function
Narcotics: opiates (most abused is heroin)



Caffeine, nicotine, cocaine
Can cause alertness, nervousness, anxiety and possible
convulsions
Acts directly on the CNS
Slows breathing, lowers heart rate, tolerance develops
quickly
Hallucinogens: alter perceptions of the CNS

Disorientation, high blood pressure, body temperature, even
convulsions 
23. Why is breaking a drug habit difficult? How do
smokers try to avoid nicotine withdrawals?


Addiction can be both physiological (body
is dependent) and psychological (you feel
like you need it)
Replacement therapies can help addicts


Nicotine patches and gum for smokers
Methadone for morphine and heroin addicts 