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Big Neuron and Synapse Foldable – Answer Key
What you expect your students to produce will depend on their grade level and their academic level.
The detailed information provided in the answer key is to give you a more thorough understanding
about this topic. You most likely do not require your students to know all the details, so for your ease
of use, highlight which details you would like students to know and use these to guide your lessons.
Note: Structures with an asterisk * next to it are not found in plant cells.
Step
Function
1.
The action potential arrives at the axon terminal and depolarizes the pre-synaptic membrane.
2.
The action potential triggers voltage-gated Ca2+ channels to open on the pre-synaptic
membrane.
3.
Ca2+ enters the pre-synaptic neuron.
4.
The presence of Ca2+ within the pre-synaptic neuron activates synaptic vesicles.
5.
Synaptic vesicles containing neurotransmitters (e.g. acetylcholine) to migrate to and fuse with
the pre-synaptic membrane.
6.
Vesicles are released into the synaptic cleft through exocytosis.
7.
Neurotransmitters diffuse across the cleft (20nm wide) and bind to receptors (e.g. acetylcholine
receptor) on the post-synaptic membrane. This either excites (acetylcholine excites) or inhibits
the post-synaptic membrane by generating excitatory post-synaptic potentials (EPSPs) or
inhibitory post-synaptic potentials (IPSPs) respectively.
8.
In some pre-synaptic neurons, autoreceptors are present that help regulate the function of the
pre-synaptic neuron. Autoreceptors bind to the neurotransmitters to provide a feedback loop
that regulates the amount of neurotransmitter that is released. The more the autoreceptors
bind, the less neurotransmitters are released.
9.
Transporter proteins on the pre-synaptic membrane help with the reuptake of
neurotransmitters from the cleft back into the pre-synaptic neuron. This helps to reverse the
effects of the neurotransmitter.
10.
Enzymes (e.g. acetylcholinesterase) in the synaptic cleft break down the neurotransmitter to
reverse its effects. The products of this breakdown (e.g. acetate and choline) will get
reabsorbed back into the pre-synaptic neuron to get reformed into active neurotransmitters
again.
Structure
11. dendrites
Function
These are branched projections off of the cell body that receive information from
the axon terminals of other neurons through synaptic transmissions. The dendritic
tree (post-synaptic membrane surface) provides a large surface area for
communication with other neurons and it is here that EPSPs and IPSPs are
generated.
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12. axon hillock
This is a specialized part of the cell body that connects to the axon. This is where
post-synaptic potentials (the EPSPs and IPSPs) are summated before being
transmitted down the axon. Summation determines whether or not an action
potential will be triggered by the combined effects of the post-synaptic potentials.
13. Schwann cell
These are the primary glial (non-neuronal) cells of the nervous system. There are
two types of Schwann cells – myelinating and non-myelinating. The myelinating
type wraps itself around the axons of sensory and motor neurons and produce a
fatty white substance called myelin. This forms the myelin sheath.
14. axon terminals
These are the terminal branch points at the end of an axon. They are also called
synaptic boutons. Between an axon terminal and the surface of the next
neuron/cell is a small gap called the synaptic cleft. These three structures together
form the synapse. The axon helps promote the electrical transmission of the nerve
impulse, and the synapse promotes the chemical transmission of the nerve impulse
through the use of neurotransmitters.
15. cell body
This is the part of a neuron that contains the nucleus and the majority of the
organelles. It is also called the soma.
16. nodes of
Ranvier
These are the gaps found in the myelin sheath (between Schwann cells) and are 1
micrometer wide. Only in these areas, where the axon is not insulated by the
myelin sheath, can the electrical impulse jump from node to node. This is called
salutatory conduction and it speeds up the conduction of the electrical impulse
down the axon.
17. myelin sheath
This is formed by the numerous myelinating Schwann cells wrapped around
peripheral (sensory and motor) neurons. It functions to support and conserve the
electrical impulse generated down an axon, it provides nutrients to the neuron and
it plays a role in nerve development and regeneration.
18. axon
A long projection away from the cell body that conducts electrical impulses away
from the cell body and towards another neuron or an effector (e.g. muscle/gland).
Axons can be either myelinated or unmyelinated. Some cells do not have axons
and transmit electrical impulses through their dendrites.
Note: Nerve impulse and electrical impulse are synonymous. Neuron and nerve cell are also
synonymous.
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Created by Anh-Thi Tang – Tangstar Science
Copyright © 2015 Anh-Thi Tang (a.k.a. Tangstar Science)
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