Download Action potential - Solon City Schools

Neurons
I bet your neurons are all fired
up now!
The Nervous System
NEURON = 1
cell

Afferent, Efferent
and Interneurons
Example:
Optic Nerve, Auditory
Nerve
Example:
Nerve =
a bundle of neurons
Types of Neurons
• Efferent (Motor) Neurons
carry outgoing messages from the brain
and spinal cord to the muscles and glands
• Interneurons -
neurons within the
brain and spinal cord that communicate
internally and between sensory inputs
and motor outputs
• Afferent (Sensory) Neurons carry messages from tissues and sensory
organs to the brain and spinal cord for
processing
Neurons
Neurons
Neurons
Neurons
Neurons
Neurons
Neurons
Parts of a Neuron
Synapse
(space
between
the neuron
where
chemical
messages
are sent to
dendrites
of other
cells)
Neurons
How neurons communicate
Neurons use an electro-chemical process to
send messages
• Why electrical?
– Pushing information through axon is based on
process of positive and negative charges of
electrical atoms (ions)
• Potassium (K+), Sodium (Na+), Chloride (Cl-)
• Why chemical?
– Neurotransmitters (chemicals) cross the synapse:
different ones send different impulses and need to
find receptors
– It can either excite (fire) or inhibit (prevent
firing)
•
Messages are sent at a speed of 2-200 mph
• Neurons are altered with use (learning) – unused
neurons die (“neural sculpting)
How does a neuron fire
The electrical impulse is called the action potential
Step 1 - Resting potential – neuron is charged and
ready to fire
Polarized – positive outside, negative inside
–
(Na+)
(Cl- & K+)
Selectively permeable – gates do not allow sodium
ions to pass through the cell membrane
–
Step 2 - Action potential – brief electrical charge
that travels down the neuron
Transmits neural messages to other neurons,
muscles or glands
When stimulated – depolarizes
–
–
•
Sodium (Na+) rushes in
Step 3 - Repolarization
–
Potassium (Ka+) flows out repolarizing the Axon.
Step 4 – Refractory Period – brief period of time
when neuron won’t fire no matter how much
stimulation
• Sodium/Potassium pumps push Sodium (Na+) out and
Potassium in (Ka+) bringing axon back to a resting state
Action Potential
Action Potential
Action Potential
Action Potential
Action Potential
Electrical Transmission –
The Action Potential
http://outreach.mcb.har
vard.edu/animations/ac
tionpotential_short.swf
How to generate a neural impulse
1. Neuron is stimulated by light, heat,
pressure or chemical messages
(neurotransmitters) from other neurons.
2. Signals from other neurons are either
–
–
–
Excitatory - tell neuron to fire (brings neuron closer to
firing
Inhibitory - tell neuron not to fire (brings neuron further
away from firing)
(excitatory) – (inhibitory) reach minimum threshold,
(minimum energy needed for a neuron to fire) an action
potential will occur
3. All or None Law – once the neuron fires the
impulse moves down the action potential at
the same intensity—it can’t be stopped
Synapse
Agonist
Action Potential
Resting Potential
Refractory period
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Po
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2.
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A brief electrical charge that travels
down the axon of a neuron is called
the
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What disease is related to degeneration
of the neuron’s myelin sheath?
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A. parkinson’s disease.
B. Multiple sclerosis.
C. Alzheimer’s disease.
D. schizophrenia.
Huntington’s Disease
1.
2.
3.
4.
5.
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The function of dendrites is to
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1. receive incoming signals from other
neurons.
2. release neurotransmitters into the
spatial junctions between neurons.
3. coordinate the activation of the
parasympathetic and sympathetic
nervous systems.
4. control pain through the release of
opiate-like chemicals into the brain.
5. transmit signals to other neurons.
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The movement of positively charged
ions across the membrane of a neuron
can produce a(n)
Action potential
Synapse
Neurotransmitter
Myelin sheath
Interneuron
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The axon of a resting neuron has gates that do
not allow positive sodium ions to pass through
the cell membrane. What is this characteristic
called?
1. Myelin sheath
2. Threshold
3. Selective
permeability
4. Action potential
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5. Refractory period
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The minimum level of stimulation
required to trigger a neural impulse is
called the
Reflex
Threshold
Synapse
Action potential
All-or-none
response
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Dendrites are branching extensions of
Neurotransmitters
Endorphins
Neurons
Myelin
Endocrine Glands
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How do neurons communicate with
each other?
The chemical process
How Neurons Communicate
How Neurons Communicate
How Neurons Communicate
How Neurons Communicate
How Neurons Communicate
Inhibition and Excitation
Excitation – the process of making the neuron
receiving neurotransmitters more likely to
generate an action potential (fire)
Inhibition – the process of making the neuron
receiving neurotransmitters less likely to
generate an action potential
Excitation>Inhibition for neuron to fire
Threshold – minimum stimulation for neuron to
fire (-55 mV)
Synaptic Transmission
http://learn.genetics.utah.e
du/content/addiction/rewar
d/neurontalk.html
Neurotransmitters
Neurotransmitters – Chemical messengers
in the brain. Different types affect the
brain and behavior in various ways
Excitatory neurotransmitters bring the
dendrite closer to threshold by allowing
positive ions to rush in. (ex. Glutamate)
Inhibitory neurotransmitters take the
dendrite further away from threshold by
allowing negative ions to rush in (ex. GABA)
Drugs can be…..
• Agonists- mimic
neurotransmitters
• Antagonists- block
neurotransmitters
• Reuptake Inhibitors- block
reuptake
Acetylcholine (ACH)
• Deals with motor movement,
memory and learning.
• Too much and you will….
• Too little and you will…
• Lack of AcH has been linked
to Alzheimer’s disease.
• Black widow – increased AcH
• Botox – decreased AcH
• Curare – decreased AcH
Dopamine
• Deals with motor
movement and
alertness/attention,
emotion, rewards.
• Lack of dopamine linked to Parkinson’s
disease.
• Too much - linked to
schizophrenia.
Serotonin
• Regulates sleep,
dreaming, mood,
pain, aggression,
appetite and sexual
arousal
• Depression - Lack of
serotonin
• Anorexia = too much
• Bulimia – too little
Endorphins
• Involved in pain
control.
• “endorphins make
you happy” – runners
high (emotions)
• Drugs that mimic = .
Agonists - Heroine,
morphine, codeine
Norepenephrine
• Fight or flight
response
• Helps control
alertness and arousal
• Undersupply can
depress mood
GABA
• Major inhibitory
neurotransmitter
meaning it keeps the
neuron from firing
(slows CNS)
• Undersupply linked
to seizures, tremors,
insomnia
• Alcohol consumption
causes an increase in
Gaba
Glutamate
• Major excitatory
neurotransmitter
Meaning…
It causes neurons to
fire – overactive
CNS
• Oversupply can over
stimulate brain,
producing migraines
or seizures
• MSG
Drugs can be…..
• Agonists- mimic
neurotransmitters
• Antagonists- block
neurotransmitters
• Reuptake Inhibitors- block
reuptake
Agonists and Antagonists
http://thebrain.mcgill.ca/flash/i/i_03/i_03_m/
i_03_m_par/i_03_m_par_cocaine.html#dro
gues
Agonist and Antagonists
Examples:
Agonists – Opiate Drugs Heroine,
Morphine (Endorphins)
Black Widow Spider Venom (AcH)
Antagonists – Botulin (AcH), Botox
(AcH), Curare (AcH)
Reuptake refers to the
1. movement of neurotransmitter
molecules across a synaptic gap.
2. release of hormones into the
bloodstream.
3. inflow of positively charged ions
through an axon membrane.
4. reabsorption of excess
neurotransmitter molecules by a
sending neuron.
5. the ending of the refractory
period.
Antidepressants such as Prozac
target which neurotransmitter?
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A. serotonin.
B. glutamate.
C. GABA.
D. acetylcholine.
Dopamine
A.
1.
2.
3.
4.
5.
Lindsey has just played a long volleyball match after
injuring her ankle in the first game, but feels little
fatigue or discomfort. Her lack of pain is most likely
caused by the release of
Glutamate
Dopamine
Acetylcholine
Endorphins
Insuline
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5.
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A person with schizophrenia may have an overactive dopamine
system. Drugs used to treat this disorder prevent the action of
dopamine by keeping it from binding to its receptors. These
drugs are
1.
2.
3.
4.
5.
Agonists
Reuptakes
Action Potentials
Antagonists
Synapses
Neurotransmitters that bring a
neuron closer to firing are called
1.
2.
3.
4.
5.
Agonist
Antagonists
Inhibitory
Reuptake
Excitatory
The Nervous System
Central Nervous System
• Brain
• Spinal chord
• Interneurons
Peripheral Nervous System
• All nerves that are
not encased in bone.
• Everything but the
brain and spinal
cord.
• Motor and Sensory
Neurons
• Autonomic and
Somatic
Somatic Nervous System
• Controls voluntary
muscle movement.
• Uses motor
(efferent) neurons.
Autonomic Nervous System
• Controls the
automatic functions
of the body.
– Lungs, stomach,
intestines, liver,
kidney, heart
• sympathetic and the
parasympathetic
Sympathetic Nervous System
• Fight or Flight Response.
– Arouses and expends
energy
• Causes:
– Increase in heart rate,
breathing, dilates pupils,
slows down digestion,
relaxes bladder
Parasympathetic Nervous System
• Rest and Digest
Response
• Automatically slows
the body down after
a stressful event.
• Causes:
– Heart rate and
breathing slow down,
pupils constrict and
digestion speeds up.
The peripheral nervous system
consists of:
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D.
association areas.
the spina chord.
the reticular formation.
sensory and motor neurons.
as
.
A.
B.
C.
D.
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As Allison reaches for a box in her garage, out jumps a big spider. Her
heart immediately begins to race as she withdraws her hand, but soon
she realizes that the spider is harmless, and she begins to calm down.
Which part of her nervous system is responsible for brining her back to
a normal state of arousal?
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C.
A. sympathetic nervous system
B. somatic nervous system
C. parasympathetic nervous
system
D. skeletal nervous system
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Reflexes
• Reflex - a simple, automatic,
inborn response to a sensory
stimulus
– Normally, sensory (afferent)
neurons take info up through
spine to the brain.
– Some reactions occur when
sensory neurons reach just the
interneurons in the spinal cord
= reflex
– Survival adaptation.
A Simple Reflex
A Simplified Neural Network
Neurons learn to work together as a team.
Neurons that fire together, wire together = learning
The Endocrine System
•A system of glands that secrete
hormones.
•Hormones are similar, but work a lot
slower than neurotransmitters.
•Neurotransmitter
Neurotransmitters
•nervous system
•Speed = fraction of a second
•Hormones
•blood stream
•Speed = several sec to travel
from gland to tissue
Hormones
•Messages outlast neurotransmitters
Master Gland:controls other
glands
Responsible
for releasing
growth
hormones
Controls
pituitary gland
Sends info to
CNS
Overactive = too
thin
Underactive = too
fat
Adrenaline or
epinephrine and
norepinephrine
Hypoglycemia
– low blood
glucose/sugar
Hyperglycemia
-High blood
glucose/suger
(diabetes)
Estrogen
Testosterone
Figure 3A.11 The endocrine system
© 2011 by Worth Publishers