Download Chapter 13: The Nervous System

Chapter 13: The Nervous System
 How does the human body react to changes in its internal environment?
 How do the senses enable us to detect sensory information and perceive
our environment?
 There are two main divisions of your nervous system:
o
o
 The central nervous system is used for what?
 What makes up the central nervous system?
 What is the peripheral nervous system?
 So what is the difference between the CNS and PNS?
 The PNS can be divided further into _________________________ and
_______________________.
 Somatic nerves control the skeletal muscles, bones, and skin.
 The autonomic system can be divided into the
_____________________________ and the
_________________________________________.
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 There are two different types of cells found in the nervous system, these
are ___________________ and ___________________.
 Glial cells are often called neuroglial cells, they are
______________________________________ cells. So what are they
important for?
 Individual neurons are organized into tissues called nerves.
 Neurons are the functional units of the nervous system.
 All neurons contain what?
 What are neurons specialized to do?
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Part
Dendrite
Function
Cell Body
Axon
 The axon carries the nerve impulse toward other neurons or to the
___________________________.
 Many axons are covered with a glistening white coat of fatty protein
called the myelin sheath.
 If they have myelin, they are said to be ___________________________.
 What does the myelin sheath do?
 Schwann cells are a special type of glial cell that produces
_____________________________________.
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 The areas between the sections of myelin sheath are known as the
____________________________________.
 Nerve impulses jump from one node to another, thereby speeding the
movement of nerve impulses. Myelinated = _____________________.
 The speed of an impulse along the nerve fiber is also affected by the
_____________________________________ of the axon.
 What is the relationship between the speed of the impulses and the
axon diameter?
 Neurilemma is a delicate membrane that surrounds the axon of some
nerve cells. What does neurilemma do?
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 Why is it that when you paper cut your finger, it starts to gain more
feeling as time goes on?
 What is the difference between white and grey matter?
Check your understanding:
 1. Define homeostasis.
 2. Explain why the nervous system is critical for maintaining
homeostasis.
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 3.Create a table to identify the different systems in the nervous system
and explain the structure and function of each.
 4. Compare the basic function of neurons and glial cells.
 5. Draw a neuron and label these parts: Dendrites, Schwann Cell, Myelin
Sheath, Axon, Nodes of Ranvier, Terminal End Branches
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 Nerves are categorized into 3 groups:
o
o
o
 Sensory neurons are also known as ______________________ neurons.
 What does a sensory neuron do?
 The cell bodies of sensory neurons are located in clusters called
______________________ that are located outside of the spinal cord.
 Interneurons link neurons to other neurons. They are only found in the
___________________ and __________________.
 What does an interneuron do?
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 Motor neurons are also known as
____________________________________.
 What does a motor neuron do?
Structure
Sensory Receptors
Sensory Neurons
Interneurons
Motor Neurons
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Funtion
Effectors
Label the following diagram using these terms: Sensory receptor, sensory
neuron, interneurons, motor neurons, effector, CNS, PNS
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 Imagine you are driving late at night and a deer jumps out in front of
your vehicle. Trace the pathway from sensory receptors to the effectors.
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 What types of cells have scientists been looking into to help rebuild
damaged cells?
Reflex Arc
 You should note that this is an ______________________________
movement but it is still part of the somatic NS.
 What is a reflex?
 Reflex arcs are known for being the simplest nerve pathway in our
bodies. This means that it doesn’t involve coordination from the brain.
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Check your understanding:
 1. List the three types of neurons and identify their primary function.
 2. Identify the basic neural pathway that is involved as you dodge a
wayward tennis ball. Compare this pathway with a a withdrawal reflex.
3. Label the following diagram.
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13.2: Electrochemical Impulses
 The action potential is the voltage difference across a nerve cell
membrane when the nerve is excited.
 The resting potential is the voltage difference across a nerve cell
membrane when it is not transmitting a nerve impulse. This is usually
___________________________.
 Like all cells, neurons have a huge supply of
___________________________________________________________
on both sides of the cell membrane.
 There is a higher the concentration of
___________________________________ ions inside the cell (+) and a
higher concentration of _______________________ ions (+) outside of
the cell.
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 Cell membranes are
___________________________________________.
 Ions pass through gated ion channels by the process of
_____________________________________.
 There are many more K+ channels than Na+ in the membrane, so more
K+ diffuses out of the cell than Na+ diffuses in.
 What is mainly responsible for creating the electrical potential?
 As K+ leaves the cell, it transfers the + charge outside of the cell in the
_________________________________________________________.
 Large protein molecules that are ________________________ charged
are present in the ___________________________________________.
 These large proteins are stuck inside the membrane and when K+ leaves
this creates an overall charge of what?
 So how is this electrochemical gradient maintained?
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 When a neuron receives a stimulus, the cell membrane becomes more
permeable to Na than to K.
 Na gates will open during an action potential and K gates will close.
 Why do the Na+ rush into the nerve cell?
 A rapid flow of Na+ causes a charge reversal or
________________________________________.
 Once the voltage inside of the nerve cell becomes (+), Na gates slam
closed and the inflow of Na+ is halted.
 K gates are now open and K+ once again begins to diffuse out of the
nerve cell.
 This restores the original polarity of the membrane and is called
___________________________________.
 K gates close relatively slowly and the outside of the cell becomes even
more positively charged than the resting membrane as K ions continue
to move out of the cell.
 This excessive diffusion is called
__________________________________.
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 How is the original high Na+ on outside and the high K+ on the inside
restored?
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 In order for a 2nd action potential to occur, the period of depolarization
must be completed and the nerve must repolarize.
 This is called the ____________________________________________.
 Conduction of an action potential is not like conduction of charge along a
wire conductor.
 The axon is actually a poor conductor of electrical charge.
 Many action potentials are generated one after another along the cell
membrane, causing a
__________________________________________________________.
 A good analogy of this would be what?
 A wave of depolarization is followed by a wave of what?
 Action potentials don’t decay in strength as they are conducted down
the axon.
 Unidirectional Propagation: Moving the electrical impulse one direction.
 It spreads from the ________________________________ to the
_________________________________.
 During repolarization, the Na+ gates are still closed so there is no
possible depolarization.
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 What is saltatory conduction?
 What provides the ability for saltatory conduction?
 What type of neuron conducts faster?
 What is a threshold level?
 What happens if we increase the intensity of a stimuli above that critical
threshold?
 What is an all-or-none response?
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 So how does your Nervous System detect various levels of stimuli?
Check your understanding:
 1. Summarize the events that occur as an impulse is transmitted along
the length of the neuron using diagrams and/or a flow chart.
 2. Why are action potentials only conducted in one direction?
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 3. Compare the structure and functions of myelinated neurons and
unmyelinated neurons.
 4. How does myelination of the axon speed up transmission of an action
potential? How are organisms containing neurons without a myelin
sheath cell’s structured to speed up transmission?
 5. What is the all-or-none response?
 Explain a high pain tolerance, in terms of threshold levels.
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 The synapse is a small space between neurons or between neurons and
effectors. This space contains small vesicles containing transmitter
chemicals.
 Chemicals are released from end plates as nerve impulses move along
the axon.
 Transmitter chemicals are released from presynaptic neuron and diffuse
across the synapse.
 How does this work on the postsynaptic neuron?
 Acetylcholine can act as an excitatory transmitter chemical. It opens Na+
channels. This causes ________________________________________.
 How is acetylcholine stopped so that the postsynaptic neuron would not
remain in constant depolarization?
 Acetylcholine can also act as an inhibitory transmitter. It opens more K
gates so that the K+ on the inside of the neuron follow the concentration
gradient and diffuse out of the neuron.
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 How does this work on the postsynaptic neuron?
 What are inhibitory transmitters?
 What is GABA used for?
 What is the principle of summation?
 What are the main purposes of serotonin?
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 What are the main purposes of dopamine?
 What do endorphins do?
 What is norepinephrine used for?
 When are endorphins released?
 How do opiates work?
 What is the problem with using opiates?
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 What are two examples of depressants and what do they do?
Check your understanding:
 1. What is the function of neurotransmitters in the nervous system?
 2. Compare the excitatory and inhibitory effects of neurotransmitters on
the postsynaptic membrane.
 3. Compare and relate the function of acetylcholine and cholinesterase.
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 4. Cocaine affects a synapse by blocking the re-uptake of the
neurotransmitters dopamine by the presynaptic neurons. Therefore, the
levels of dopamine continue to build in the synapse causing certain
affects on the body.
o Explain how cocaine interferes with the neural transmission
across the synapse.
o Describe the role of dopamine in the brain.
o Formulate a hypothesis about how cocaine could be addictive
after only one use.
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13.3: The Central Nervous System
 The CNS is made up of the
__________________________________________________________.
 The brain is surrounded by 3 protective membranes known as the
____________________________.
 These three layers are :
 Where is cerebrospinal fluid found?
 What does the spinal cord do? Where is it located?
 What is the difference between the dorsal nerve tract and the ventral
nerve tract?
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 There are three distinct regions of the brain:
 The forebrain is divided how?
 The midbrain is the smallest region of the brain and consists of mainly
what?
 The hindbrain joins with the spinal cord.
 What is the cerebrum?
 What is the cerebral cortex?
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 What is the corpus callosum?
 Each hemisphere can be further subdivided into 4 lobes:
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 Using your textbook, create a table as to what each lobe of the brain is
used for.
 There are three important parts of the forebrain:
 What does the thalamus do?
 What is the hypothalamus used for?
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 What are olfactory bulbs used for?
 What are the major regions of the hindbrain?
 What does the cerebellum control?
 What do the pons do?
 What is the function of the medulla oblongata?
Check your understanding:
 1. Identify the main structures of the CNS, and describe their general
function.
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 2. Explain how the blood-barrier and the cerebrospinal fluid protect the
brain and the spinal cord.
 3. Identify the major structures in the hindbrain, midbrain, and
forebrain, and the functions of these structures.
 4. Identify the four lobes of the cerebrum, and describe the function of
each.
 5. Describe the primary areas of the brain that are responsible for fine
motor control of the muscles, as well as the area that processes sensory
information from the skin.
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 6. Compare different technologies used for studying the brain.
 7. If the motor area of the right cerebral cortex was damaged in a car
accident, which side of the body would be affected? Why?
 8. Compare white and grey matter. Identify the location of each and
describe its function.
 9. Label the following diagram.
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 The peripheral nervous system is divided into 2 main systems:
 What does the sensory somatic do?
 What does the autonomic nervous system do?
 How is the autonomic nervous system divided?
 What is the sympathetic nervous system?
 What is the parasympathetic nervous system?
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 Copy table 1 on page 435 from your textbook.
Check your understanding:
 1. What generally triggers the sympathetic nervous system and what are
the effects on the body?
 2. What generally triggers the parasympathetic system, and what are the
effects on the body?
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