Neurophysiology Worksheet
Myelinated Neurons
Glial cells, either Schwann cells in the PNS or olgiodentrides in the CNS, form a myelin sheath around a
neuron. A myleinated neuron is called white matter while a non-myleinated neuron is called grey
matter. The myelin lines up on the neuron like beads. Gaps exist, called nodes of Ranvier where neuron
membrane is exposed. Action potentials move across the myelin sheath by jumping from node to node in
a process called saltatory conduction. Unmyleinated neurons conduct their action potentials in what is
known as continuous propagation. Saltatory conduction is much faster and efficient since less ATP is
needed to restore the ion distribution at resting membrane potential.
1. Functionally, what is the difference between neurons and neuroglia?
Neurons are responsible for information transfer and processing in the nervous system. Neuroglia
are specialized cells that provide support throughout the nervous system.
2. What is the primary difference between continuous propagation of an action potential and
saltatory conduction of action potentials?
In continuous propagation, an action potential spreads across the entire excitable membrane
surface in a series of small steps. In salutatory prorogation, an action potential appears to leap
from node to node, skipping the intervening membrane surface. Saltatory propagation carries
nerve impulses many times more rapidly than continuous propagation.
3. Guillain-Barre syndrome is a degeneration of the myelin sheath that ultimately may result In
paralysis. What is the relationship between degeneration of the myelin sheath and muscular
paralysis?
In myelinated fibers, saltatory conduction transmits nerve impulses at rates over 300 mph,
allowing the impulses to reach the neuromuscular junctions fast enough to initiate muscle
contraction and promote normal movements. In a demyelinating disease, the nerve impulses can't
’propagate along the demyelinated axon; therefore, the muscle is not stimulated, leading to
paralysis. Eventually, the muscles atrophy because of a lack of adequate activity involving
contraction.
Synapse and Neurotransmitters
Neurons do not actually touch each other. Instead they communicate through gaps known as synaptic
clefts with chemicals called neurotransmitters. These chemicals signals can excite the neuron or inhibit
the neuron. It is the receptors on the neuron and not the neurotransmitter that determines the
excitability/inhibition.
Neurotransmitters are released from a presynaptic cell to a post synaptic cell. When an action potential
arrives at a presynaptic cell, it allows for extra cellular calcium ions to enter. This triggers the release of
a neurotransmitters held within the presynaptic cell. These neurotransmitters enter the synaptic cleft
and bind to receptors on the post synaptic cell. These post synaptic cell receptors are typically
chemically gated Na+ or Cl- channels. These chemically gated channels eventually lead to
depolarization or hyperpolarization of the post synaptic cell.
Acetylcholine, commonly abbreviated Ach, can have one of two effects on a cell. If the cell is excitatory
receptors, they called nicotinic receptors. If the receptor is muscarinic, the response will be inhibitory.
The neurotransmitter must be removed from the postsynaptic cell in order to allow for recovery. The
neurotransmitters are often reabsorbed in a process called reuptake. Acetylcholine is broken down by
enzymes in the synapse called acetyl cholinesterase. It is broken down into acetate and choline. Choline
is reabsorbed to create more Ach.
Norephine is another neurotransmitter. It is generally excitable in nature and commonly occurs within the
sympathetic division. Gamma amino butyric acid, commonly abbreviated GABA, is typically inhibitory
in nature. Dopamine is a neurotransmitter that is involved in the reward pathway. Serotonin is involved
in happiness.
1. What would be the effect on neurons if a person was hypocalcaemia (lack of calcium)?
A person with hypocalcaemia might not be able to properly prorogate action potentials. If they do
not have enough calcium, there might not be enough calcium to enter a neuron. If this calcium
cannot enter the neuron, there is no way to release neurotransmitters. If neurotransmitters cannot
be released, an action potential could not be generated from neuron to neuron.
2. Of the three neurotransmitters discussed, which combinations of neurotransmitters and receptors
would produce EPSP? Which would produce IPSP? Why?
An EPSP results in a depolarization. Norephine or Ach with nicotinic receptors would result in an
EPSP because they are excitable.
An IPSP results in a depolarization. GABA or Ach with muscarinic receptors would result in an
EPSP because they are excitable.
3. How does the nicotine in cigarettes ultimately trigger action potentials and led to addiction?
The nicotine in cigarettes stimulates postsynaptic Ach nicotinic receptors, producing prolonged
EPSP that facilitate action potentials in neurons. Nicotine also increases the release of the
neurotransmitter dopamine, producing feelings of pleasure and reward and may lead to addiction.
Myelinated Neurons
Glial cells, either __________________ in the PNS or __________________ in
the CNS, form a myelin sheath around a neuron. A myleinated neuron is called
_____________________ while a non-myleinated neuron is called
________________. The myelin lines up on the neuron like beads. Gaps exist,
called ______________________ where neuron membrane is exposed. Action
potentials move across the myelin sheath by_________________ from node to
node in a process called ___________________________. Unmyleinated neurons
conduct their action potentials in what is known as
____________________________________. __________________________ is
much faster and efficient since less _______ is needed to restore the ion
distribution at resting membrane potential.
1. Functionally, what is the difference between neurons and neuroglia?
2. What is the primary difference between continuous propagation of an action
potential and saltatory conduction of action potentials?
3. Guillain-Barre syndrome is a degeneration of the myelin sheath that
ultimately may result In paralysis. What is the relationship between
degeneration of the myelin sheath and muscular paralysis?
Synapse and Neurotransmitters
Neurons do not actually touch each other. Instead they communicate through gaps
known as _____________________ with chemicals called _________________
These chemicals signals can____________ the neuron or ____________ the
neuron. It is the ___________ on the neuron and not the neurotransmitter that
determines the excitability/inhibition.
Neurotransmitters are released from a ___________________ cell to a
________________ cell. When an ________________________ arrives at a
presynaptic cell, it allows for extra cellular _______________ ions to enter. This
triggers the release of a _______________ held within the presynaptic cell. These
neurotransmitters enter the __________________ and bind to _____________ on
the post synaptic cell. These post synaptic cell receptors are typically
_______________________________ Na+ or Cl- channels. These chemically
gated channels eventually lead to _____________ or _________________of the
post synaptic cell.
Acetylcholine, commonly abbreviated _______, can have one of two effects on a
cell. If the cell is excitatory receptors, they called _______________ receptors. If
the receptor is ______________, the response will be inhibitory. The
neurotransmitter must be removed from the postsynaptic cell in order to allow for
recovery. The neurotransmitters are often reabsorbed in a process called
__________. Acetylcholine is broken down by ____________ in the synapse
called _____________________________________. It is broken down into
acetate and choline. ______________ is reabsorbed to create more Ach.
___________________ is another neurotransmitter. It is generally excitable in
nature and commonly occurs within the sympathetic division. Gamma amino
butyric acid, commonly abbreviated GABA, is typically ____________ in nature.
______________________ is a neurotransmitter that is involved in the reward
pathway. _______________ is involved in happiness.
1. What would be the effect on neurons if a person was hypocalcaemia (lack of
calcium)?
2. Of the three neurotransmitters discussed, which combinations of
neurotransmitters and receptors would produce EPSP? Which would
produce IPSP? Why?
3. How does the nicotine in cigarettes ultimately trigger action potentials and
led to addiction?