Download Neurons & the Nervous System

Neurons & the Nervous
System
Chapter 2: The Brain and
Behavior
The Nervous
System
Peripheral
Somatic
Central
Autonomic
Sympathetic
Parasympathetic
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  You will be able to….
• Identify the parts of a neuron and
their functions in creating &
sending neural messages.
• http://www.youtube.com/watch?v=sX87g3
AHIbc
• http://www.youtube.com/watch?v=5uQZfa
URU_Y&feature=related
• http://www.youtube.com/watch?v=Y5nj3Zf
eYDQ
• http://www.youtube.com/watch?v=NqVeH
26i7Kg&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 pipecleaners represent?
• Which part of the neuron does the blue pipecleaner represent?
• Which part of the neuron does the black pipecleaner 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  You will be 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 impulses
Average 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  You will be
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…
C
• When is the neuron
insensitive to incoming
B
D
messages?
A
• When is the neuron
depolarizing?
E
• When is the neuron at its
resting potential?
• When is the neuron at its action potential?
• When is the neuron repolarizing?
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
Neurotransmitters
• Dopamine (DA)
Function: Voluntary movement,
sensations of pleasure & reward
Malfunctions: Too little  Parkinson’s,
Too much --> Schizophrenia
• Agonists  cocaine & amphetamines
• Antagonists  Ritalin, alcohol
Neurotransmitters
• Serotonin
Function: Mood, appetite, sleep,
impulsivity, concentration
Malfunctions: Depression,
Eating Disorders
• Agonists  LSD, Prozac
Neurotransmitters
• Norepinephrine
Function: Alertness, arousal,
mood, heart rate/appetite
Inhibitory & excitatory
Malfunctions: Depression
• Agonists  Cocaine, amphetamines
• GABA (most prevalent inhibitory NT)
Function: Anxiety, sleep, seizures
Malfunctions: Anxiety disorders,
tremors, insomnia
• Glutamate (main excitatory NT)
Function: Memory & learning
Malfunctions: Migraines, seizures, addictions
• Endorphins
Function: Pain control
Malfunctions: None
Neurotransmitter Song
• Choose a popular camp song or rhyme
• Change the lyrics to describe a
neurotransmitter or several
neurotransmitters