AP Biology: Nervous Systems
Chapters 48 and 49.2 partly and 50.1 partly
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Big idea 3:
3.E.2. Animals have nervous systems that detect external and internal signals, transmit and integrate
information, and produce responses.
Chapter 48 and 49.2
Illustrative examples:
• Acetylcholine
• Epinephrine
• Norepinephrine
• Dopamine
• Serotonin
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• GABA
• Vision
• Hearing
• Muscle movement
• Abstract thought and emotions
• Neuro-hormone production
• Forebrain (cerebrum), midbrain (brainstem), and hindbrain (cerebellum)
• Right and left cerebral hemispheres in humans
4.A.4: Organisms exhibit complex properties due to interactions between their constituent parts.
Chapter 48.4
Illustrative examples:
• Stomach and small intestines
• Kidney and bladder
• Root, stem and leaf
• Respiratory and circulatory
• Nervous and muscular
• Plant vascular and leaf
Start with this:
http://www.ted.com/talks/neil_burgess_how_your_brain_tells_you_where_you_are.html
Activity: Neuron Structure
BioFlix: How Neurons Work
Activity: Nerve Signals: Action Potentials
Investigation: What Triggers Nerve Impulses?
BioFlix: How Synapses Work
Activity: Signal Transmission at a Chemical Synapse
What is the fundamental difference between communication via nerves and communication via
hormones? ____________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
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Neurons are nerve cells that transfer information within the body.
Communication by neurons is based on two distinct types of signals: long-distance electrical
signals and short-distance chemical signals.
The specialized structure of neurons allows them to use pulses of electrical current to receive,
transmit, and regulate the long-distance flow of information within the body.
To transfer information between cells, neurons use a chemical signal that acts over very short
distances.
http://www.ted.com/talks/jill_bolte_taylor_s_powerful_stroke_of_insight.html
Various sensory receptors detect both external and internal stimuli and relay sensory information
via sensory neurons of the
peripheral nervous system to the
central nervous system for
integration. In nervous systems,
information is processed in three
stages:
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Here is a
simple reflex
arc, which
shows the
three stages
of
information
processing:
The cells that conduct impulses are called neurons One neuron communicates with the next
neuron at the synapse. The first cell in the sequence is called the pre-synaptic neuron/ cell, and
the second one is called the ______post synaptic neuron/_ cell.
What is the difference between an axon and a dendrite? ________________________________
__axons transmit messages away from the cell body and are coated in myelin sheath, singular,
long. Dendrites take the message to the cell body, are branched and many and are not coated in
myelin sheath are short. _____________________________________________
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Cells that wrap around long axons or dendrites are called Schwann cells. The membrane of these
cells contains a white, fatty material called ___myelin__. What is the function of this myelin
sheath? 1. Increases speed of impulse transmission
2. Insulates axons from each other.
3. May be necessary for neuron repair.
Excellent visual for Schwann cell wrapping axon: http://www.siumed.edu/~dking2/ssb/neuron.htm#glia
This is what the myelin sheath looks like with the electron microscope:
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Complete the table
Neuron
Structure
Function
Sensory neuron
Long dendrite, short axon.
Myelinated dendrite and
axon.
Cell body is just outside
CNS.
Cell body is like a bulb.
Carries nerve
impulses from a
receptor to the CNS.
Motor neuron
Short dendrite, long axon.
Myelinated axon.
Cell body is just inside the
CNS.
Cell body has short
dendrites attached to it.
Carries nerve
impulses (messages)
from the CNS to an
effector (eg muscle).
Interneuron
Short dendrites, long or
short axon.
Long axons are myelinated.
Carries nerve
impulses within the
CNS.
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Concept 48.2 Ion pumps and Ion channels establish the resting potential of a neuron.
What do we mean when we say that a neuron has a ‘resting potential’? What is the size of the
potential? _____________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
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How is the membrane potential established?
______________________________________________________________________________
______________________________________________________________________________
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The K+ and Na+ protein channels are ‘gated channels’. Various stimuli can open these channels
to varying degrees to cause a graded potential. What is the difference between hyperpolarization
and depolarization of the membrane? _______________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
When an impulse is generated in a neuron, the membrane potential reverses itself in a particular
pattern called an ‘action potential’. Concept 48.3
______________________________________________________________________________
______________________________________________________________________________
_________________________________________________
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Here is what is happening on a molecular level during an action potential:
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
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The action potential is propagated down the neuron because the influx of Na+ ions depolarizes
the next part of the membrane to the threshold potential and triggers the action potential there.
___________________________________________
___________________________________________
___________________________________________
___________________________________________
___________________________________________
Action potentials are said to be ‘all or nothing’
because: ___________________________________
___________________________________________
___________________________________________
The action potential ‘leap frogs’ down the myelinated
axon/dendrite because the depolarization is able to
spread from one node of Ranvier to the next. This makes the impulse travel much faster than it
would if the myelin sheath were not present.
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Concept 48.4: Neurons communicate with other cells at synapse.
What happens when an action potential reaches the end of the axon? How does the message pass
to the postsynaptic cell? _________________________________________________________
_____________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
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The postsynaptic cell receives synapses from many other neurons. Some of the synapses are
inhibitory and some are excitatory. What will determine whether or not an action potential will
be generated in the postsynaptic cell?
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
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There are many different neurotransmitters.
http://thebrain.mcgill.ca/flash/i/i_03/i_03_m/i_03_m_par/i_03_m_par_cannabis.html#drogues
The same neurotransmitter can produce different effects on different types of cells.
 There are more than 100 known neurotransmitters.
 Nearly all these neurotransmitters fall into a small number of groups based on chemical
structure.
 The major classes of neurotransmitters are acetylcholine, biogenic amines, amino acids,
neuropeptides, and gases.
 A single neurotransmitter may have more than a dozen receptors.
 The receptors for a specific neurotransmitter can vary significantly in their effects on
postsynaptic cells.
o For this reason, many drugs used to treat nervous system diseases or affect brain function are
targeted to specific receptors rather than to particular neurotransmitters.
 Acetylcholine is one of the most common neurotransmitters in both invertebrates and
vertebrates.
 Except in the heart, vertebrate neurons that form a synapse with muscle cells release
acetylcholine as an excitatory transmitter.
• Acetylcholine
• Epinephrine
• Norepinephrine
• Dopamine
http://on.aol.com/video/the-link-between-dopamine-and-drug-addiction-297703220
• Serotonin
• GABA
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The same neurotransmitter has different effects depending on its location in the nervous
system. Here is a list of some of the main neurotransmitters:
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Overview: Command and Control System
The human brain contains an estimated 1011 (100 billion) neurons.
The circuits that interconnect these brain cells are enormously complex.
The human nervous
system is organized into a
central nervous system
and a peripheral nervous
system.
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Concept 49.1 Nervous systems consist of circuits of neurons and supporting cells.
How do various animal nervous systems compare?
In vertebrates, the brain and the spinal cord form the CNS; the nerves and ganglia make up the
peripheral nervous system (PNS).
Regional specialization is a hallmark of both systems.
Peripheral nervous are either sensory or motor:
How do somatic motor nerves and autonomic motor
nerves differ in function?
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
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How does the function of the sympathetic division of the autonomic nervous system differ from
the function of the parasympathetic division? ________________________________________
______________________________________________________________________________
______________________________________________________________________________
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Which neurotransmitter is found in sympathetic neurons? epinephrin
In the parasympathetic? ____acetyl choline____________________________
The brain is divided into a number of regions, each with its own functions:
The cerebrum is highly organized, with specific functions in specific regions:
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http://www.youtube.com/watch?v=_e60_4ZV0zs Blood brain barrier interest only
https://www.youtube.com/watch?v=86NDMfxU4ZU Development of the embryonic brain
interest only
MP3 Tutor: The Human Brain (28.15)
Medulla oblongata controls autonomic, homeostatic functions including: breathing, heart and
blood vessel activity, swallowing, digestion and vomiting
Cerebrum (cerebral cortex)
integrating centre for memory, learning, emotions, and other highly complex
functions of the central nervous system; initiation of somatic motor responses
(sketetal muscle contractions)
Thalamus is the “main input center for sensory information going to the cerebrum and the main
output center for motor information leaving the cerebrum. Incoming information from all the
senses is sorted in the thalamus and sent to the appropriate cerebral centers for further
processing. The thalamus also receives input from the cerebrum and other parts of the brain that
regulate emotion and arousal.”
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Cerebellum unconscious coordination of movement and balance, including hand-eye
coordination _________________
Hypothalamus maintenance of homeostasis, particularly in coordinating of endocrine and
nervous systems (neuroendocrine control center - ; secretes hormones of the posterior pituitary
and releasing factors, which regulate the anterior pituitary - involved in osmoregulation,
contractions of uterus, control of sexual cycles, milk production, control of thyroid gland, etc.)
Corpus callosum a thick band of nerve fibres that connect the right and left cerebral hemispheres.
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Concept 50.1 Sensory receptors transduce stimulus energy and transmit signals to the
central nervous system.
All stimuli represent forms of energy.
Sensation converts this energy to a change in the membrane potential of sensory receptor cells, thereby
regulating the output of action potentials to the central nervous system.
Sensory pathways have four basic functions in common: sensory reception, transduction,
transmission, and integration.
Sensory pathways begin with sensory reception, the detection of a stimulus by sensory cells.
Most sensory cells are specialized neurons or epithelial cells that exist singly or in groups with other cell
types in sensory organs, such as eyes or ears.
All sensory cells and organs, as well as structures within sensory cells that respond to specific stimuli,
constitute sensory receptors.
Many sensory receptors detect stimuli from outside the body, including heat, light, pressure, and
chemicals.
There are also sensory receptors for stimuli from within the body, such as blood pressure and body
position.
In a crayfish, stretch-sensitive
dendrites in stretch receptor
cells open ion channels in
response to bending of body
muscle.
In other sensory receptors, ion channels open or close when substances outside the cell bind to proteins
on the membrane or when pigments in the sensory receptor absorb light.
The resulting flow of ions across the plasma
membrane generates a membrane potential.
The conversion of a physical or chemical
stimulus to a change in the membrane potential
of a sensory receptor is called sensory
transduction; the change in the membrane
potential is known as a receptor potential.
Receptor potentials are graded potentials; their
magnitude varies with the strength of the
stimulus.
o
o
Many sensory receptors show extreme
sensitivity and can detect the smallest
physical unit of stimulus possible.
Most light receptors can detect a single quantum (photon) of light; chemical receptors can detect a
single molecule.
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Sensory information is transmitted through the nervous system in the form of nerve impulses, or action
potentials.
For many sensory receptors, transduction of the energy in a stimulus into a receptor potential initiates
transmission of action potentials to the central nervous system (CNS).
Sensory receptor cells, such as the crayfish stretch receptor, are neurons that produce action potentials
and have an axon that extends into the CNS.
Other sensory receptor cells release neurotransmitters at synapses with sensory neurons.
At almost all such synapses, the receptor releases an excitatory neurotransmitter.
The magnitude of a receptor potential
controls the rate at which action potentials are
produced by a sensory receptor.
Integration of sensory information begins as soon as the information is received.
Receptor potentials produced by stimuli delivered to different parts of a sensory receptor cell are
integrated through summation, as are postsynaptic potentials in sensory neurons that synapse with
multiple receptors. The CNS further processes all incoming signals.
Processing of action potentials from sensory neurons generates perception of stimuli.
When action potentials along sensory neurons reach the brain, circuits of neurons process this input to
generate the perception of stimuli.
o Perceptions—including colors, smells, sounds, and tastes—are constructions formed in the brain and
do not exist outside it.
Sensory receptors are categorized by the type of energy they transduce.
Mechanoreceptors respond to mechanical energy such as pressure, touch, stretch, motion, and sound.

Chemoreceptors respond to chemical stimuli.

Electromagnetic receptors detect electromagnetic energy such as visible light, electricity, and
magnetism.
o Photoreceptors respond to visible light and are often organized into eyes.

Thermoreceptors respond to heat or cold and help regulate body temperature by signaling surface and
body core temperature.

Pain receptors, or nociceptors, are a class of naked dendrites in the epidermis.
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