Transcript Ch. 35 Nervous System edit

Nervous System
Chapter 35
Vocabulary
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
muscle tissue
epithelial tissue
connective tissue
nervous tissue
negative feedback
neuron
cell body
dendrite
axon
myelin sheath
resting potential
action potential
synapse
neurotransmitter
15.
16.
17.
18.
19.
central nervous system
cerebrum
cerebellum
brain stem
reflex
I.
How Nerve Cells Communicate
Nervous system = controls and coordinates functions
throughout the body and responds to internal and external
stimuli
B. Neurons = cells that transmit electrical signals (impulses)
1. 3 types of neurons = sensory, interneurons, motor
2. Parts of neuron
a. cell body = contains nucleus and cytoplasm
b. dendrites = branched extensions that receive stimuli
from the environment or from other neurons, impulse
goes toward the cell body
c. axon = a long fiber that carries impulses away from
the cell body, ends in axon terminals
d. mylein sheath = insulating membrane around axon,
nodes (gaps) allow impulse to jumps from one to the
other increasing speed of impulse
A.
DRAW Figure 35-5, pg 897
Neuron
dendrites
cell body
nodes
axon terminals
axon
myelin
sheaths
C. Nerve Impulse
1. Resting Neuron
a. electrical charge of neuron is from charged ions
b. At rest, outside of the cell has a net “+”charge, and
the inside has a net “-” charge.
c. resting potential = electrical charge difference of a
neuron at rest btwn. the outside and inside is -70 mVolts
d. “sodium-potassium pump” in membrane
pumps Na+ ions out of the cell & K+ into the
cell by active transport (takes energy)
2. Moving Impulse
a. an impulse begins when a neuron is stimulated
by another neuron or by the environment
b. the gates within the sodium channels open,
allowing positively charged Na+ ions to flow
inside the cell, inside temporarily becomes more
“+” than the outside
c.
internal charge goes from -70 mVolts to +30 mVolts
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+
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+
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+
+_
d. action potential = reversal of charges, from negative
to positive, is called a nerve impulse
e. influx of sodium stimulates the opening of potassium
pores and K+ flows out
f. Now all of the sodium is inside and the
potassium is outside
 How does the cell go back to its original
condition?
g. The sodium/potassium pump kicks in to restore the
resting potential.
DRAW Figure 35-7, pg 899
+
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_
_
+
h.
The depolarization on one segment starts a
domino effect down the neuron.
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+
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+
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+
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+
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+
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+
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+
Movement of an Action Potential
3. Threshold
a. threshold = minimum level of a stimulus that
is required to activate a neuron
b. All-or-none nerve impulse  a stimulus
stronger than the threshold produces an
impulse, a stimulus that is weaker than the
threshold will produce no impulse
1) like a pushing over a row of dominoes
Direction of Impulse
Dendrite of
adjacent neuron
How an
Impulse
Moves
Between
Two
Neurons
Axon
Vesicle
Receptor
Axon
terminal
Synaptic cleft
Neurotransmitter
D. Synapse
1. synapse = gap between the axon of one neuron and
the dendrites or cell body of the next neuron
2. When the impulse reaches the end of the axon
chemicals called neurotransmitters are released
and carry the signal to the next neuron.
3. Overall impulse pathway:
Electrical --> Chemical --> Electrical
DRAW Figure 35-8, page 900
II. Divisions of Nervous System
A.
Overall Functions
1.
2.
3.
B.
Sensory input – vision, hearing, balance, smell, taste, and
touch
Motor output – muscle contraction and movement
Memory and integration of information
Central Nervous System (CNS)
1.
2.
Relays messages, processes info, analyzes info
Consists of brain & spinal cord
QuickTime™ and a
Sorenson Video 3 decompressor
are needed to see this picture.
C.
Brain
1. Cerebrum
a. Largest region; folds and grooves increase surface
area
b. Controls voluntary activities and all higher brain
functions (intelligence, learning and judgment)
c. Right and left hemispheres that are connected by
corpus callosum
Cerebrum
Corpus callosum
2. Cerebellum
a. Center for balance and coordination of
voluntary muscle movements.
Cerebellum
3.
Brain Stem
a. Relays information between brain and spinal cord
b. Comprised of the pons and medulla oblongata
c. Work together to control breathing, heart rate,
blood pressure, digestion, and swallowing.
Pons
Medulla oblongata
4. Thalamus
a. Relay station for all sensory input to the cerebrum.
5. Hypothalamus
a. Homeostatic center that controls endocrine system
(hormones), body temperature, thirst, hunger, anger
and fatigue
Thalamu
s
Hypothalamus
Cerebrum
Thalamus
Pineal
gland
DRAW Figure
35-9, pg 901
Hypothalamus
Cerebellum
Pituitary gland
Pons
Medulla oblongata
Spinal cord
D. Spinal Cord
1.
2.
31 pairs of nerves branch out from the spinal cord
Functions
a. Carries info to and from brain to body
b. Reflex center
Gray matter Central canal
Spinal nerve
White matter
Meninges
E. Reflexes
1.
reflexes = quick, automatic response to a
stimulus
2.
5-part reflex arc:
a. Sensory receptor reacts to stimulus (heat on
finger)
b. Impulse is carried to the spinal cord by a
sensory neuron
c. In the spinal cord, the impulse is transferred to a
motor neuron
d. Motor neuron conducts a nerve impulse to an
effector (arm muscles)
e. Effector responds to the impulses by contracting
(hand gets pulled away from the heat)
Reflexes:
DRAW Fig. 35-11
pg 904
F.
Peripheral Nervous System (PNS)
1.
2.
3.
Sensory neurons  transmits impulses from sense organs to
CNS
Interneurons  connect sensory and motor neurons in spinal
cord
Motor neurons  transmits impulses from CNS to the muscles
or glands
a.
Somatic NS (voluntary) responds to external
stimuli
1) Regulates activities that are under conscious control
(e.g. picking your nose)
2) Some reflex control
b.
Autonomic (involuntary) NS respond to internal
stimuli; two divisions:
1) Sympathetic - ↑ energy consumption (increase HR)
2) Parasympathetic - ↓ energy consumption (decrease
HR)
3) Both help maintain homeostasis by having opposing
effects
G. Nervous System Graphic Organizer
Nervous
System
is divided
into
Central
nervous
system
Motor
nerves
Somatic
nervous
system
that make
up
Sympathetic
nervous
system
Peripheral
nervous
system
which consists
of
Autonomic
nervous
system
which is divided
into
Parasympathetic
nervous system
Sensory
nerves
III. The Senses
A. 5 General Sensory Receptors: pain, thermo-, mechano-,
chemo- and photoreceptors.
 Where do you think these different types of receptors are
found and what is their function?
Take YOUR OWN NOTES on 35-4 pg 906-909
B.
C.
D.
E.
Vision
Hearing and Balance
Smell and Taste
Touch
IV. Drugs
A.
Drug = any substance, other than food, that changes
the structure or function of the body
1.
2.
3.
B.
The most powerful drugs affect the nervous system
Addiction = an uncontrollable dependence on a drug
Drug abuse = can be defined as using any drug in a way that
most doctors would not approve
Narcotics
1.
2.
3.
narcotic = substance that blunt the senses decreasing pain
ex: opium, morphine, codeine, heroin
Heroin - increases release of dopamine, over-stimulation of
neurons
a. Effects – intense rush, pleasure, decrease of heart rate and
breathing, decrease pain
b. Problems – receptors become used to this over-stimulation
and need more heroin just to work normally (rapid
addiction), overdose causes breathing to stop
C. Stimulants
1. stimulant = substance that increases heart rate,
blood pressure, and breathing rate
a. Increases the release of neurotransmitters; leads to
release of energy and feeling of well-being, relieves
pain
b. When effect wears off, brain’s supply is depleted
leaving the user depressed and fatigued
c. Ex: cocaine, amphetamines (crystal meth, speed, ice,
crank), ecstasy, ritalin, nicotine, and caffeine
2. Cocaine/crack – blocks dopamine reuptake by
neurons causing a “flood” of dopamine in the brain
a. Effects – euphoria and relaxation
b. Problems – highly addictive, heart attacks,
delirium, strokes, hypertension
Cocaine
Cocaine and Your Brain
In the synapse, or space
between neurons (area of
detail), cocaine binds to
dopamine reuptake
transporters, causing a
"flood" of dopamine in the
brain.
3. Meth / Speed - damages axon terminals
a. Effects – temporary mood elevation, exhilaration
(high), increased mental alertness, wakefulness
b. Problems -- extremely addictive (sometimes with just
one use), very jittery high, along with anxiety,
insomnia, sometimes paranoia, can cause
convulsions, heart irregularities, high blood
pressure, depression, restlessness, tremors, severe
fatigue, overdose can cause coma and death
4. Ecstasy - damages axon terminals
a. Effects – damages axon terminals, increased
energy, peacefulness
b. Problems – teeth clenching, water regulation,
increased heart rate and blood pressure, heart, liver,
or kidney failure, permanently damages axon
terminals affecting mood, sleep, and memory
ECSTASY
Serotonin travels
through the healthy
brain across the
synapse. Ecstasy
use damages the
axon terminals
(ends) of neuron
fibers. Chemical
messages relating to
mood, sleep,
memory, and more
are disrupted.
D. Depressants – suppresses CNS actions
1.
2.
3.
Effects – relieve anxiety, irritability, tension, produce a
state of intoxication
Ex: tranquilizers, barbiturates, marijuana, alcohol
Marijuana
a.
b.
4.
THC disrupts coordination of nerve impulses in the brain
long term – more lung damage than cigarettes, memory loss,
attention deficit, decreased levels of testosterone, abnormal
sperm
Alcohol
a.
b.
c.
d.
blocks receptors making the neuron less excitable &
increases dopamine
physical and mental impairment, depression, liver damage
destroys liver cells
involved in 1/3 of all automobile crashes, involved in 1/3 of all
homicides
E. Inhalants – decreases O2 to the brain,
poisons body
1. Effects – makes you feel light-headed or dizzy for
several minutes
2. Problems – death can result from 1st time, kidney
and liver damage, decreased muscle size, loss of
smell an hearing over time, brain damage
3. Ex: glue, gasoline, nail polish remover, aerosols
Inhalants
Cheap high, quick buzz
You can die the first time you try inhalants.
Sudden Sniffing Death – sudden heart failure
Asphixiation (lack of O2)
Inhalants damage or destroy myelin.
Healthy myelin
helps speed
messages from cell
to cell in your brain.
When myelin is
damaged, your
muscles won't be
able to obey your
brain.