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– 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
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
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.
http://www.youtube.com/watch?v=Y5nj3ZfeYDQ
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.
• 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
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
• 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)
Dendrites
Cell body (soma)Axon
Myelin sheath
Terminal buttons
There are more neurons in the brain than stars in the
Milky Way
Neuron Activity• You will need:
– 1 black pipe-cleaner– 2 white pipe-cleaners– 1 blue or orange pipe-cleaner– 2 white beads
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?
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
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
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
Axon of sending neuron
Terminal button
Synaptic cleft
Receptor sites
Dendrite of receiving neuron
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
• 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
Velocity of neural impulse is 250 mph
Resting potential
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.
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
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
Neurotransmitters• Excitatory NT: increases the
likelihood that postsynaptic neuron will fire
• Inhibitory NT: decreases likelihood that postsynaptic neuron will fire
Neurotransmitters• Acetylcholine (ACh)
Function: Muscle contractions, learning, memory
EXCITATORY (sometimes inhibitory)Malfunctions: Alzheimer’s Disease
• Dopamine (DA)Function: Voluntary movement,
sensations of pleasure & rewardMalfunctions: Too little Parkinson’s,
Too much --> Schizophrenia
• Agonists cocaine & amphetamines• Antagonists Ritalin, alcohol
Neurotransmitters
• SerotoninFunction: Mood, appetite, sleep,
impulsivity, concentration
Malfunctions: Depression, Eating Disorders
• Agonists LSD, Prozac
Neurotransmitters
• NorepinephrineFunction: Alertness, arousal,
mood, heart rate/appetiteInhibitory & excitatoryMalfunctions: Depression
• Agonists Cocaine, amphetamines
Neurotransmitters
• 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
Neurotransmitter Song • Choose a popular camp song or
rhyme• Change the lyrics to describe a
neurotransmitter or several neurotransmitters