neurons & the nervous system
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Neurons & the Nervous System. Chapter 2: The Brain and Behavior. Central v. Peripheral. Central contains brain & spinal cord In a computer, this is your central processing unit (CPU) Peripheral – sensory & motor neurons that transmit messages between brain and muscles & glands - PowerPoint PPT PresentationTRANSCRIPT
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Neurons & the Nervous System
Chapter 2: The Brain and Behavior
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Central v. Peripheral• Central contains brain & spinal cord
– In a computer, this is your central processing unit (CPU)
• Peripheral – sensory & motor neurons that transmit messages between brain and muscles & glands– In a computer, this includes your
keyboard, mouse, CD-ROM, printer, etc.
Spinal cord is about 43 cm long in women and 45 cm long in men;
¾ inches thick
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Autonomic v. Somatic• Somatic – voluntary - controls
purposeful body movements, movements for balance & posture– Consciously perceived sensations
• Autonomic – involuntary – automatic activities such as heartbeat, respiration, digestion, dilation of pupils, etc.– Some can be under conscious control
(i.e. respiration)– Smooth & cardiac muscle, some glands
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Sympathetic v. Parasympathetic
• Sympathetic = “Fight-or-flight” response– Uses energy reserves to cope with stress
or emergency– Adrenaline!
• Parasympathetic = “Rest and digest”– Conserves & builds up stored energy
reserves The Sympathetic & Parasympathetic systems work
together to maintain homeostasis.
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http://www.youtube.com/watch?v=Y5nj3ZfeYDQ
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Today’s Goal Today’s Goal You will be able You will be able to….to….
• Identify the parts of a neuron and their functions in creating & sending neural messages.
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• http://www.youtube.com/watch?v=sX87g3AHIbc
• http://www.youtube.com/watch?v=5uQZfaURU_Y&feature=related
• http://www.youtube.com/watch?v=Y5nj3ZfeYDQ
• http://www.youtube.com/watch?v=NqVeH26i7Kg&feature=related
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Parts of the Neuron• Neurons: nerve cells• Dendrites: branch-like end of neuron which
receives messages• Cell body (soma): contains nucleus • Axon: long tail-like end of neuron which
transmits (sends) messages
There are 100 billion neurons in the human brain
There are 300 billion neurons in the octopus brain
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• Myelin: fatty substance that speeds up transmission of impulse
• Terminal buttons: bulb-shaped structure at end of axon
The longest axon of a neuron belongs to what
animal?Giraffe – 15 feet! (from toe to neck)
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Dendrites
Cell body (soma)Axon
Myelin sheath
Terminal buttons
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There are more neurons in the brain than stars in the
Milky Way
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Neuron Activity• You will need:
– 1 black pipe-cleaner– 2 white pipe-cleaners– 1 blue or orange pipe-cleaner– 2 white beads
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Neuron Activity• Which part of the neuron do the white
pipe-cleaners represent?• Which part of the neuron does the blue
pipe-cleaner represent?• Which part of the neuron does the black
pipe-cleaner represent?• Which part of the neuron do the white
beads represent?
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Types of Neurons• Afferent (sensory) neurons:
send messages from sensory receptors to the spinal cord & brain
• Efferent (motor) neurons: relay messages from brain & spinal cord to muscles & glands
• Interneurons: transmits neural stimulus between sensory & motor neurons
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Today’s Goal Today’s Goal You will be You will be able to….able to….
• Describe how a neural impulse is generated and how neurons communicate in the brain and throughout the body.
• http://www.youtube.com/watch?v=90cj4NX87Yk&feature=related • http://www.youtube.com/watch?v=DF04XPBj5uc
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The Synapse• Synapse (synaptic cleft): gap between
dendrites of one neuron and axon of another
• Receptor sites: parts of dendrite which receive neurotransmitters
• Neurotransmitters: chemical substances involved in sending neural impulsesAverage neuron makes about 1,000 synapses and receives 10,000 synapses
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Axon of sending neuron
Terminal button
Synaptic cleft
Receptor sites
Dendrite of receiving neuron
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Neural Impulse: electrochemical firing of a nerve cell
• Resting potential: electric potential when neuron not firing (-70 millivolts)
• Depolarization: neuron reduces resting potential by becoming positively charged
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• Action Potential: neuron fires when it reaches +30-40 millivolts
• Repolarization: internal charge becomes more negative
• Refractory period: phase after firing an impulse, neuron will not fire
• All-or-none principle: neuron will fire or not fire, no in-between
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Velocity of neural impulse is 250 mph
Resting potential
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Today’s Goal Today’s Goal You will be You will be able to…able to…
• Discuss how the major neurotransmitters affect the body and one’s behavior
Learning Target: Describe neural communication and discuss the impact of neurotransmitters.
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Review• Which nervous system is most active during
stress or a “fight-or-flight” situation?Sympathetic NS
In the graph…• When is the neuron
insensitive to incoming messages?
• When is the neuron depolarizing?
• When is the neuron at its resting potential?
• When is the neuron at its action potential?• When is the neuron repolarizing?
A
B
C
D
E
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Substances that Affect Neurotransmitters
• Agonist: similar to the NT, mimics its effects
• Antagonist: inhibits the release of NT by sending neuron, or blocks receptor site for NT on receiving neuron
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Neurotransmitters• Excitatory NT: increases the
likelihood that postsynaptic neuron will fire
• Inhibitory NT: decreases likelihood that postsynaptic neuron will fire
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Neurotransmitters• Acetylcholine (ACh)
Function: Muscle contractions, learning, memory
EXCITATORY (sometimes inhibitory)Malfunctions: Alzheimer’s Disease
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• Dopamine (DA)Function: Voluntary movement,
sensations of pleasure & rewardMalfunctions: Too little Parkinson’s,
Too much --> Schizophrenia
• Agonists cocaine & amphetamines• Antagonists Ritalin, alcohol
Neurotransmitters
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• SerotoninFunction: Mood, appetite, sleep,
impulsivity, concentration
Malfunctions: Depression, Eating Disorders
• Agonists LSD, Prozac
Neurotransmitters
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• NorepinephrineFunction: Alertness, arousal,
mood, heart rate/appetiteInhibitory & excitatoryMalfunctions: Depression
• Agonists Cocaine, amphetamines
Neurotransmitters
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• GABA (most prevalent inhibitory NT)Function: Anxiety, sleep, seizuresMalfunctions: Anxiety disorders, tremors, insomnia
• Glutamate (main excitatory NT)Function: Memory & learningMalfunctions: Migraines, seizures, addictions
• EndorphinsFunction: Pain controlMalfunctions: None
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Neurotransmitter Song • Choose a popular camp song or
rhyme• Change the lyrics to describe a
neurotransmitter or several neurotransmitters