Download 5.1 Nervous System

Nervous System
Lesson 1: Structure of the Nervous System
Module Introduction
Module Introduction
Lesson 1: Structure of the Nervous System
Lesson 2: Organization of the Nervous
System
Lesson 3: The Senses
Lesson 4: Effects of Drugs
Module Wrap-Up
Learning Objectives
By the end of this lesson, you should be able to:
1. Describe the structure of a neuron
2. Explain the function of each part of a neuron
3. Analyze How does a nerve impulse move along a neuron
Discussion Question
If you step on several toy blocks, it’s
going to hurt.
Why is this response a good thing?
Key Vocabulary
•
•
•
•
•
•
Spinal Cord ‫الحبل الشوكي‬
Neuron ‫خلية عصبية‬
Dendrite ‫التغصنات‬
Axon ‫محور عصبي‬
Cell body ‫جسم الخلية‬
Reflex arc ‫قوس انعكاسي‬
• Review:
• Diffusion
Describe the structure of a neuron
Nervous System
A communication network that extends
throughout your body.
Nervous system is
made of :
1. Spinal cord
2. Brain
3. Nerve cells (Neurons)
Describe the structure of a neuron
Let’s have a look at the neuron structure by
watching this video!
Describe the structure of a neuron
Neurons
Neurons are specialized nerve cells:
 help you gather information about your environment
 interpret the information and react to it.
 Neurons consist of three main regions:
 Dendrites
 Cell body
 Axon
Describe the structure of a neuron
 Dendrites pass signals they receive on to the cell body in electrical
impulses.
 The axon passes those impulses on to the other neurons or muscles.
Synapse: A small gap
between axon of one
neuron and dendrite of
another neuron
Describe the structure of a neuron
Look at both neurons, what can you see different between them?
This is called the
Myelin sheath
The Myelin sheath is made up of protein
and fatty substances.
It allows electrical impulses to transmit
quickly and efficiently along the nerve cells.
Explain the function of each part of a neuron
Types of Neurons
Watch this video and
then write the three
types of neurons in
the chat box
https://teachers.boclips.co
m/videos/5c54da71d8eafee
cae225f23?referer=92403e0
0-a083-40dd-8372655757595907
CODE
40jq
Time: 3 minutes
Explain the function of each part of a neuron
Nervous System
Types of Neurons
1. Sensory neurons send impulses from receptors in the skin
and sense organs to the brain and spinal cord.
2. Interneurons carry impulses to motor organs
(found in the spinal cord and brain).
3. Motor neurons carry impulses away from the brain and spinal
cord to a gland or muscles, resulting in a secretion/movement
Explain the function of each part of a neuron
Think with me!
• How do you respond when you touch a hot object?
Move away from or drop the object.
Many reflexes are fast so that they occur before the
brain can interpret the situation.
• What would happen if you had to wait for the brain
to interpret the stimulus and signal an appropriate
response?
In this short amount of time, a severe burn could occur.
Explain the function of each part of a neuron
Reflex Arc: a nerve pathway of sensory neuron  interneuron  motor neuron
Brain is NOT
involved
Spinal cord
is involved
Fast response
involuntary
Explain the function of each part of a neuron
Explain the function of each part of a neuron
The impulse reaches the
spinal cord, which sends an
impulse to motor neurons in
response.
Assessment
Plenary
Let’s play Quizizz! 
https://quizizz.com/admin/quiz/61d3332e0d3278001d4f378a/neuron-structure
Learning Objectives
• By the end of this section, you should be able to:
1. Define the stimuli and nerve impulses
2. Explain How does a nerve impulse move along a neuron
3. Analyze the nerve impulse using a simulation.
Starter
Let’s label the parts of the neuron:
https://wordwall.net/resource/20348976/neuron
Define the stimuli and nerve impulses
Recall
We learned about
neuron structure in the
last class.
Can you guess how a
signal can travel through
it?
Define the stimuli and nerve impulses
1. Stimulus
A stimulus is any change in our
surroundings that can cause a
response.
How do we respond to a stimulus?
A stimulus
is created.
Our
receptors
detect this
stimulus.
Receptors
create
nerve
impulse in
our body.
Nerve
impulse
makes our
body
respond.
Define the stimuli and nerve impulses
Nerve Impulse
• Electrical charge (signal) that travels
along the neuron
• A nerve impulse results from a stimulus
Another name for
nerve impulse is
ACTION
POTENTIAL
Define the stimuli and nerve impulses
A Nerve Impulse: a Neuron at rest
 Neurons at rest do not conduct impulses.
 Na+ outside more
 K+ Inside more
Define the stimuli and nerve impulses
Action Potential
This is an electric
signal that travels
along a neuron.
Nerve impulse is also
called Action Potential.
How is this electrical
signal created?
It is because of
charged ions moving in
and out of the axon.
Explain How does a nerve impulse move along a neuron
Nervous System
Neuron at rest
 Sodium ions (Na+) collect on the outside of the cell membrane.
 Potassium ions (K+) collect on the inside of the cell membrane.
 Negative charged proteins actively transport sodium ions out of the
cell and potassium ions into the cell.
Explain How does a nerve impulse move along a neuron
Action Potential (nerve impulse)
Explain How does a nerve impulse move along a neuron
Neuron’s internal environment
What is happening inside a
neuron? Let's have a look.
The internal environment is
controlled by three factors:
1. Sodium (Na+) and
Potassium (K+) ions
2. Sodium and
Potassium Ion channels
3. Sodium/Potassium
Pumps
Explain How does a nerve impulse move along a neuron
1. Sodium (Na+) and
Potassium (K+) ions
2. Sodium and
Potassium Ion channels
3. Sodium/Potassium
Pumps
• They are positively
charges
• Present more outside
than inside the axon
• They are like door on
the axon cell
membrane that allow
the sodium and
potassium ions to pass
through (passive)
• They are pumps that
transport 3 Sodium for
every 2 potassium ions
(active)
Let’s visualize the action potential using this simulation:
Explain How does a nerve impulse move along a neuron
Threshold
Sometimes you don’t feel an insect land on you. Can you guess why?
 The minimum stimulus to
cause an action potential
is called a threshold.
Action potential are described as
“ALL or NOTHING”
Explain How does a nerve impulse move along a neuron
Threshold
If a stimulus is not strong
enough, no response is
created.
Only if the
stimulus is
strong enough
it can create an
action potential
in the neuron.
This is called
the threshold
stimulus.
Less than
threshold =
No
response
Higher than
threshold =
response
Nervous System
Action Potential (nerve impulse)
1. The stimulus causes sodium channels in the
neuron's membrane to open (Na+ ions from outside
the membrane enter the cell)
The cell's interior becomes more positive.
2.
Sodium channels close and potassium channels open
(K+ ions from inside the membrane move outside the cell)
The cell's exterior restores the positive charge.
The signal passes
down the length
of the axon like a
wave.
Activity 
• Go to this link:
https://www.liveworkshee
ts.com/c?a=c&sr=n&ms=u
z&l=ib&i=unznuzt&r=pb&
db=0&f=dzddzuzf&cd=klof
xlglxgzhf2ngnngxgexg
• You have 3 minutes to
finish the activity
Plenary
• Go to your LMS.
• Answer the POLL question there
• You have 2 minutes to answer.
Learning Objectives
By the end of this lesson, you should be able to:
Analyze How does a nerve impulse move along a neuron
Starter discussion
You miss your friends
from school.
How do you
stay in contact?
How does that
communication
happen?
LMS
• Go to your LMS.
• Answer the POLL question there
• You have 2 minutes to answer.
Key Vocabulary
• Node ‫عقدة‬
• Synapse ‫مشبك عصبي‬
• Neurotransmitter‫ناقل عصبي‬
• Myelin Sheath ‫غمد مايليني‬
• Review:
• Diffusion
Analyze How does a nerve impulse move along a neuron
Nervous System
Speed of an Action Potential
 Myelin Sheath
In certain neurons, the axon is surrounded by an
insulating lipid covering called myelin sheath.
Analyze How does a nerve impulse move along a neuron
Nervous System
Speed of an Action Potential
 Nodes along the axon allow ions to pass through the myelin layer to
the plasma membrane.
 The ions jump from node to node and increase the speed of the
impulse.
Analyze How does a nerve impulse move along a neuron
Think with me!
Knowing that the action potential in the neurons with Myelin sheath is faster than the
neurons without Myelin sheath
when a myelin sheath is useful and when is it not needed?
Neurons with Myelin
Carry impulses that are
associated with sharp pain
Neurons without Myelin
Carry impulses that are
associated with dull pain
Analyze How does a nerve impulse move along a neuron
How Neurons Communicate?
Let’s watch the video!
Analyze How does a nerve impulse move along a neuron
Nervous System
The Synapse
 The small gap between the axon of one neuron and the dendrite of
another neuron is called a synapse.
 An action potential is carried across these gaps by neurotransmitters.
Neurotransmitters
are chemicals that
bind to the receptors
Example:
Acetylcholine (Ach)
Analyze How does a nerve impulse move along a neuron
Neurotransmitter
1
Vesicles near to end of the axon terminal store
neurotransmitters.
2
A nerve impulse causes the vesicle to merge
with the cell membrane. It then releases the
neurotransmitters into the synapse through
exocytosis.
3
4
The neurotransmitter binds to receptors at the
end of the dendrites of the next neuron.
The binding of the neurotransmitter causes the
dendrites to generate a nerve impulse that
travels to the cell body.
Activity 
• Go to this link:
https://www.liveworkshee
ts.com/c?a=c&sr=n&ms=u
z&l=fz&i=dsxndns&r=ip&d
b=0&f=dzddzuzf&cd=klegn
pmlnlpoh2ngnngxgexg
You have 2 minutes to
finish the activity
Analyze How does a nerve impulse move along a neuron
Think with me!!
• Once the neurotransmitters have done their work, do you think they
need to be kept in the synapse?
Analyze How does a nerve impulse move along a neuron
Neurotransmitter
• Once the neurotransmitters
have done their work, they are
either:
1. destroyed enzymatically,
2. taken back into the terminal
from which it came
3. recycled and reused.
Let’s play Kahoot! 
https://create.kahoot.it/details/a1784810-bc52-4c4c-96876bac5f08a1da
Nervous System
Chapter Diagnostic
Questions
Another name for a nerve impulse
is _______.
A. synapse
B. threshold
C. reflex arc
D. action potential
1.
2.
3.
4.
A
B
C
D
CDQ 2
Nervous System
Section 1 Formative
Questions
What type of neuron begins a reflex arc?
A. interneuron
B. motor neuron
C. sensory neuron
D. transmitter neuron
1.
2.
3.
4.
A
B
C
D
Nervous System
Section 1 Formative
Questions
A stronger stimulus will cause a stronger
action potential.
A. True
B. False
1.
2.
A
B
FQ 3
Nervous System
Section 1 Formative
Questions
When a neuron is at rest, what
maintains the high concentration
gradients of potassium ions inside
the cell and sodium ions outside
the cell?
A.
B.
C.
D.
diffusion
osmosis
active transport
ion channels
1.
2.
3.
4.
A
B
C
D
FQ 4
Develop Concepts
Scaffolding
• ASK STUDENTS: Describe the distribution of ions inside and outside of a resting
neuron. There are more sodium ions outside the neuron and more potassium
ions inside the neuron. The distribution of these ions is unequal. There are more
negative ions in the cytoplasm than there are outside the cell. So, the inside of
the neuron is negatively charged in relation to the outside of the neuron.
• ASK STUDENTS:
• Explain the reversal of electrical charges that occurs as an action potential travels
along the neuron. An action potential results in the opening of channels in the
plasma membrane. Positively charged sodium ions rush into the cytoplasm,
causing a reversal of charges.
• Analyze what would be the effect if the sodium/potassium pump carried equal
numbers of sodium and potassium ions across the plasma membrane. There
would not be much of a difference in electrical charges inside and outside the
neuron.
• Develop a mechanism that would prevent an action potential from traveling
along the neuron. Accept any mechanism that prevents the influx of sodium
ions; some drugs bind to specific receptors on the dendrites, blocking a
substance that could trigger an action potential.