UNIVERSITY OF LAGOS, AKOKA YABA.

A TERM PAPER ON THE NUERAL COMMUNICATIONS EXPLAINING THE

FOLLOWING;

● Pressures Operating (Hydrostatic and electrostatic)

● Potential Operating (Membrane, Action) Thresholds; refractory period

● Myelinated vs Unmyelinated Conduction

● Axonal vs Synaptic Transmission

● Transmitter Substances (neurotransmitter)

NAMES: MATRIC NO:

IKPONMWOSA ESOSA A. 130904049

ONIKOSI SANDRA A. 199085036

OGUNJIMI JOEL O. 199085025

TAYO-BALOGUN DEBORAH 199085090

LECTURER: Dr. ISRAEL

INTRODUCTION

The entire workings and operations of the human body is the responsibility of the nervous

system. Nervous system coordinates the internal and external actions of the body by transmitting

signals to and from different parts of the bodies. The nervous system is divided into two parts:

the Central Nervous System (CNS) and the Peripheral Nervous System (PNS). The CNS is

further comprised of two parts: the brain and the spinal cord.

The brain, which is one of the most complex and largest organs in the human body, serves as the

center of the nervous system. It contains billions of nerve cells or neurons with the cerebral

cortex (the thin layer of the brain that covers the cerebrum) alone containing about 14 to 16

billion neurons. These neurons, classified mainly into afferent (sensory) neurons, efferent

(motor) neurons and interneurons perform specialised tasks. The sensory neurons help receive

information from the sensory systems (auditory, visual, olfactory, somatosensory and gustatory)

and send it to the CNS while motor neurons convey information from the CNS towards muscles

or glands, thereby helping the body perform actions such as eating, walking, speaking, etc. The

interneurons process the sensory information received from the environment into meaningful

representations, plan the appropriate behavioural response and connect to the motor neurons to

execute the plan.

Each neuron is connected to several thousand other neurons by the synapses and thus

communicates with them by means of its axons. The axon transports signals called the action

potentials from the neuron towards other connected neurons.

This communication between neurons involves sending chemical messengers called

neurotransmitters from one neuron to another, as well as movement of ions across the neural

membrane.

Pressures Operating

The process of ionic movement across the neural membrane occurs in two basic ways:

1. Passive transport: the movement of substance from one area to another occurs due to

forces that do not require the cell to particularly use up any energy. One of such forces is

diffusion. An ion in high concentration in one area will tend to move (or diffuse) to an

area of lower concentration if the membrane is permeable to the ion. This may also be

referred to as hydrostatic pressure.

Another force in passive transport is electrostatic pressure.Ions are either positively or

negatively charged. As it is well-known that “like charges repel and unlike charges

attract, through electrostatic pressure, an ion that is on a side of a membrane where the

charge is the same (e.g., negative with negative) will be propelled by a force to the other

side of the membrane (if the membrane is permeable) where the charge is different.

2. Active transport: an ion can be actively moved (or “forced”) by some mechanism against

the concentration or electrostatic gradient. This means that, even if an ion has been

moved to a side of the membrane through diffusion or electrostatic pressure, it can still be

moved back to the other side through active transport.

The electrostatic force is associated with electromagnetic force

Electrostatic forces are attractive or repulsive forces between particles that are caused by their

electric charges.

This force is also called the coulomb force or coulomb interaction and is so named for french

physicist Charles Augustin de Coulomb who described the force in 1785.

How the electrostatic force works

The electrostatic force works over a distance of about one tenth the diameter of an atomic

nucleus or 10~ 16m . Like charges repel one another while unlike charges attract one another.

For example two positively charged protons repel each other as do two cations, two negatively

charged electrons or two anions. Protons and electrons are attracted to each other and so are

cations and anions.

Why protons don't stick to electrons

While protons and electrons are attracted by electrostatic forces, protons don't leave the nucleus

to get together with electrons because they are bound to each other and to neurons by the strong

nuclear force . The strong nuclear force is much more powerful than the electromagnetic force

but it acts over a much shorter distance.

Calculating the electrostatic force using coulomb's law

The strength or force of the attraction or repulsion between two charged bodies can be

calculated using coulomb's law.

F= Kq1q2/r2
Here F is the force, K is proportionality, factor, q1 and q2 are the two electric charges and r is the

distance between the centre's of the two charges in the centimetre-gram-second system of units k

is set to equal 1 in a vacuum. In the meter-kilogram- second( si) system of unit, k in a vacuum is

8.98 × 109 Newton square meter per square coulomb. While protons and ions have measurable

sizes, coulomb’s law treats them as point charges.

It is important to note the force between two charges is directly proportional to the magnitude of

each charge and inversely proportional to the square of the distance between them.
SUPPORTING CELLS OF THE PERIPHERAL NERVOUS SYSTEM

Schwann cells perform the same functions the Oligodendrocytes perform but in the Peripheral

Nervous System. The myelin sheath produced by Schwann cells consists of single-cell segments

thus; a Schwann cell provides myelin for only a section of a single axon.

Myelin produced by Schwann cells is tough, elastic connective tissues which aid in the digestion

of dead or dying axon. They arrange themselves in a series of cylinders that act as a guide for

growth of damage but damaged beyond repair, Schwann cells may proliferate to fill the gap.

BLOOD BRAIN BARRIER

If one injects a blue dye into the bloodstream, all tissues except the brain and spinal cord would

be tinted blue. This simply shows that certain materials in the blood cannot get into the brain.

The Blood-Brain Barrier is a barrier that exists between the blood and fluids that encompasses

the brain, and that prevents a direct constant between the blood and the brain. The blood-brain

barrier however selectively permeable and this allows substances that can dissolve in liquids to

simply dissolve along the cell membrane while others such as glucose have to be actively

transported by special proteins. The stage where the cell membrane is Negative ad not passing

any message is known as the RESTING POTENTIAL.

A neuron receives messages or stimulations at the cell body or dendrite, the message is

conducted along the axon and it is communicated to other neurons through the synapse by means

of a chemical substance. The message is then conducted down the axon is electrical. It is

conducted by means of “alternations” in the membrane of the axon. This causes the exchange of

various chemicals between the axon and the fluids surrounding it. This exchange produces an
electrical current. It has been discovered that the inside of an axon is negatively charged with

respect to the outside. The inside of the membrane is -70mv (MilliVolts). Imagine taking two

electrodes and placing one on the outside and the other on the inside of the plasma membrane of

a living cell. If you did this, you would measure an electrical potential difference, or voltage,

between the electrodes.

The difference between the inside and the outside of the membrane is 70mv, and this electrical

charge is known as the membrane potential.

When a stimulator is used to deliver a positive charge inside the membrane it causes it to

depolarize and the membrane potential would then be reduced but it could occur if the amount

of stimulation reaches a certain point known as the threshold of stimulation

MEMBRANE POTENTIAL

This is maintained by the balance between two forces. Normally, molecules diffuse from the

region of high concentration to the region of low concentration and is usually or constantly in

motion and their rate of movement is proportional to the rate of temperature. These molecules

are always in motion colliding and veering off in different directions and pushing each other in

various directions. The process whereby molecules distribute themselves evenly throughout the

medium is called DIFFUSION.

The membrane potential is created by a cell to facilitate the transmembrane transport of ions,

nutrients, etc. Different signs exist that the presence of membrane potential throughout the

biological membrane greatly influences the membrane structure. Fundamental experiments

have been performed on fungal cells in this area.

Firstly, it is important that the membrane potential renders the membrane more permeable, that

is, it affects its primary purpose as a barrier between two different media.

Suppose you have a dead frog, what would happen if you applied an electrical stimulus to the

nerve that feeds the frog's leg? As ridiculous as it sounds, the dead leg would kick!

The Italian scientist Luigi Galvani discovered this fun fact back in the 1700s, somewhat by

accident during a frog dissection. Today, we know that the frog's leg kicks because neurons

(nerve cells) carry information via electrical signals.

How do neurons in a living organism produce electrical signals? At a basic level, neurons

generate electrical signals through brief, controlled changes in the permeability of their cell

membrane to particular ions.

Because there is a potential difference across the cell membrane, the membrane is said to be

polarized.

● If the membrane potential becomes more positive than it is at the resting potential, the

membrane is said to be depolarized.

● If the membrane potential becomes more negative than it is at the resting potential, the

membrane is said to be hyperpolarized.

All of the electrical signals that neurons use to communicate are either depolarizations or

hyperpolarizations from the resting membrane potential.

Where does the resting membrane potential come from?

The resting membrane potential is determined by the uneven distribution of ions (charged

particles) between the inside and the outside of the cell, and by the different permeability of the

membrane to different types of ions.

ELECTROLYTES

These are often split into two (2) when dissolved in water. The result of the split discharges

particles called ions.

Types of ions found in neurons

In neurons and their surrounding fluid, the most abundant ions are:

● Positively charged (cations):

● Negatively charged (anions): Chloride and organic anions

In most neurons, organic anions (such as those found in proteins and amino acids) are present at

higher concentrations inside the cell than outside.

Ions of the same charge repel each other and those with opposite charges attract one another,

therefore; Cations attract Anions and vice versa. The force encased by the attraction or repulsion

is known as Electro-static Pressure. As the force of diffusion moves molecules so also does that

of the electrostatic pressure move ions and the fact that the membrane is somewhat permeable

gives room to the membrane potential.

ACTION POTENTIAL
When a cell membrane has been stimulated more than enough, it greatly becomes permeable to

Sodium and this is due to the forces of diffusion and electrostatic pressure and as a result of this,

Sodium gushes into the cell, the sudden rush of position ion ultimately changes the membrane

potential. After this occurs, the resistance of the cell membrane to Potassium reduces greatly

which rushes outside the cell. The electrochemical reaction is what is known as the action

potential.

STAGES OF ACTION POTENTIAL

1. When the threshold of excitation is derived, the sodium ion pathways in the

membrane open and Sodium gushes in (i.e Depolarization of the membrane

potential) the influx of positively charged ions produces a rapid change in the

potential from negative to positive

2. As depolarization occurs, the Potassium ions channel begin to open and potassium

rushes out of the cell

3. As the action potential is about to reach its peak, the sodium ion channel closes and

Sodium cannot gain entry into the cell

4. Potassium ion channels most likely open and it is free to roam out of the

membrane. Here, the inside of the cells become charged positively. The outward

movement of cations cause the membrane potential to return to its original state soon

after the potential pathways close

5. When potassium ions pathways close, it can no longer leave the cell, therefore; the

membrane will overshoot its resting potential of -7-mV, the hyper-polarized

condition is due to the storage of potassium outside the membrane, although the
 excess soon diffuses away giving room for the potential to return to its original

equilibrium(i.e inside Negative and outside Positive)

After the potential, ions are much less stable and they reflect the changes in the excitability of the

nerve cell rather than the passage of the Nerve impulse.

Refractory Period:

This is defined as the period whereby the membrane potential overshoots the resting potential.

Absolute Refractory Period:

This is the period whereby the nerve cell cannot transmit another impulse.

Relative Refractory Period:

During this period, only a greater than normal stimulus can excite the cell.

SuperNormal Refractory Period:

This happens when a less than normal stimulus may excite the cell.

Sub Normal Period:

This usually happens before the neuron goes back to its normal state, the excitability to the nerve

cell is lower than normal.

AXONAL VS SYNAPTIC TRANSMISSION

Synaptic transmission is the process by which one neuron communicates with another.

Information is passed down the axon of the neuron as an electrical impulse known as the action

potential. Once the action potential reaches the end of the axon, it needs to be transferred to

another neuron or tissue.

It must cross over the synaptic gap between the presynaptic neuron and postsynaptic gap neuron

( in the axon terminal ) and the synaptic vesicles, which contain chemical messengers known as

neurotransmitters. When the electrical impulse (action potential) reaches these synaptic vesicles,

they release their contents of neurotransmitters Neurotransmitters then carry the signal across

the synaptic gap. They bend to receptor sites on the postsynaptic cell, thereby completing the

process of synaptic transmission.

Types of synaptic transmission

There are two types of synapses found in the body:

Electrical Synapses and Chemical Synapses.

Electrical Synapses allow the direct passage of ions and signalling molecules from cell to cell

whereas chemical synapses do not pass the signal directly from the presynaptic cell to the

postsynaptic cell, In a chemical synapse, an action potential in the presynaptic neuron leads to

the release of a chemical messenger called a neurotransmitter. The neurotransmitter then diffuses

across the synapse and binds to a receptor on the postsynaptic cell.

Electrical Synapse

Binding of the neurotransmitter leads to the production of an electrical signal in the postsynaptic

cell.

An electric synapse passes the signal very quickly which allows groups of cells to act in unison.

Chemical Synapse
Chemical synapse takes much longer to transmit the signal from one cell to the next; however

chemical synapses allow neurons to integrate information from multiple presynaptic neurons,

determining whether or not the postsynaptic cell will continue to propagate the signal.

Electrical Synapses transmit action potentials via the direct flow of electrical current at gap

junctions.

Gap junctions are formed when two adjacent cells have transmembrane pores that align. The

membranes of the two cells are linked together and the aligned pores form a passage between

cells.
Chemical synapses comprise most of the synapses in our body. In a chemical synapse, a

synaptic gap or cleft separates the pre and the postsynaptic cells. An action potential propagated

to the axon terminal results in the secretion of chemical messengers, called neurotransmitters

from the axon terminals. The Neurotransmitter molecules diffuse across the synaptic cleft and

bind to receptor proteins on the cell membrane of the postsynaptic cell.

The function of axon is to transmit information to different neurons, muscles and gland. In

certain sensory neurons such as for touch and warmth, the electrical impulse travels along an

axon from the periphery to the cell body and from the cell body to the spinal cord along another

branch of the same axon.

Inside the axon terminal of a sending cell are many synaptic vesicles. These are membrane-

bound spheres filled with Neurotransmitter molecules

There is a small gap between the axon terminal of the presynaptic neuron and the membrane of

the postsynaptic cell, and this gap is called the synaptic cleft.

When an action potential or nerve impulse arrives at the axon terminal, it activates voltage-gated

calcium channels in the cell membrane. Ca2+ which is presented at a much higher concentration

outside the neuron than inside, rushes into the cell.

The Ca2+ allows synaptic vesicles to fuse with the axon terminal membrane releasing

neurotransmitter into the synaptic cleft.

MYELINATED VS UNMYELINATED CONDUCTION

To recap, an axon is the part of the neuron that is threadlike that serves as an extension through

which electrical signals received through the dendrite into the soma travel down to the terminal

buttons. The terminal buttons contain the synaptic vesicles which house neurotransmitters.

When signals are received into the soma, they are processed at the axon hillock, the area just

before the axon that controls the initiation of the neuron’s chemical impulse after the processing

of the incoming signals.

In some axons, glial cells form a fatty substance known as the myelin sheath. Invertebrate axons

or small vertebrate axons are normally unmyelinated while larger vertebrate axons are often

myelinated.
Figure 1 Propagation of the action potential in unmyelinated and myelinated axons

MYELINATED CONDUCTION

In myelinated axons, the myelin sheath acts as a coat for the axon and insulates it from the

extracellular fluid, thereby increasing the speed at which the signal travels down the axon.

Sensory and motor axons of the peripheral nervous system are myelinated by specialised cells

known as the Schwann cells.

The Schwann cells wrap around an axon along its length. There are several nodes between the

ends of successive Schwann cells called the nodes of Ranvier. It is at these nodes that the axon

is exposed to the extracellular fluid (that is, the nodes are unmyelinated spaces). These nodal

spaces are ∼2 μm long and are located ∼1mm intervals along the axonal surface. Between two

nodal spaces is a myelinated internodal space.

In myelinated axons, the nodal spaces have voltage-gated sodium channels. It is only at these

nodal spaces that activation is required during the action potential propagation as the Na+

channels are concentrated at the nodes of Ranvier.

The propagation of an action potential at each node thus results in depolarization of the next

node and subsequently, the generation of action potential with an internode delay of only ∼20

μs.

When an action potential is generated at the axon hillock, the signal is conducted passively (that

is, instantly and in a decreasing manner) to the first node of Ranvier. Even though the signal is

slightly reduced by the time it reaches the first node, it is still strong enough to open voltage-
activated sodium channels at the node, thus generating another action potential which is

conducted in a similar manner to the next node.

Conduction in myelinated axons thus occurs instantly making the signal “jump” down the axon

from one node to another. This is referred to as saltatory conduction (from the Latin saltare,

meaning “to leap”). And while there is a slight delay at each node of Ranvier, conduction in

myelinated axons is still much faster than the conduction in unmyelinated axons.

UNMYELINATED CONDUCTION

The unmyelinated axons are usually loosely surrounded by a glial cell in some cases and not

covered at all in other cases (such as in parallel fibres in the cerebellar molecule layer). Here, the
speed of conduction of an action potential is proportional to the square root of the diameter of the

axon.

In unmyelinated axons, the Na+ and K+ channels take part in the propagation of the action

potential. Here, the action potential propagates along the length of the axon through local

depolarisation of each neighbouring patch of membrane. This causes the patch of membrane to

also generate an action potential.

NEUROTRANSMITTERS

What are Neurotransmitters: They refer to the body’s chemical messengers. They are molecules

used by the nervous system to transmit messages between neurons, or from neurons to muscles.

Communication between two neurons happens in the synaptic cleft (the small gap between the

synapses of neurons). Here electrical signals that have travelled along the axon are briefly

converted into chemical ones through the release of neurotransmitters, causing a specific

response in the receiving neuron.

It is also called chemical transmitters, any of the chemical agents released by neurons (A neuron

is a nerve cell, a basic cell of the nervous system, it has a body containing a nucleus and two or

more fibres), to stimulate neighbouring neurons or muscle or gland cells, thus allowing impulse

to be passed from one cell to the next throughout the nervous system. They are substances which

neurons use to communicate with one another and with their target tissues in the process of

synaptic transmission (neurotransmission).

A neurotransmitter influences a neuron in one of three ways, viz: Excitatory, Inhibitory or

Modulatory. An excitatory transmitter promotes the generation of an electrical signal called

action potential in the receiving neuron, on the other hand, if it inhibits the target cell, it is an

inhibitory neurotransmitter acting in an inhibitory synapse. So the type of the synapse and the

response of the target tissue depends on the type of neurotransmitter.

Most neurotransmitters are either small amine molecules, amino acids, or neuropeptides. There

are about a dozen known small molecule neurotransmitters and more than 100 different

neuropeptides, and neuroscientists are still discovering more about their interactions are involved

in countless functions of the nervous system as well as controlling bodily functions.

NEUROTRANSMITTERS SIGNALING

Neurons communicate with their target tissues at synapses into which they release chemical

substances called neurotransmitters (ligands). As this communication is mediated with chemical

substances, the process is called chemical neurotransmission and it happens within chemical

synapses. Each synapse consists of the;

● Presynaptic Membrane: membrane of the terminal bouton ( axon ending) of the

presynaptic nerve fibre.

● Postsynaptic membrane: membrane of the target cell.

● Synaptic cleft: a gap between the presynaptic and postsynaptic membranes.

Neurotransmitters are synthesized by neurons and are stored in vesicles, which typically are

located in the axon’s (an axon also called fibre nerve, is a portion of a nerve cell that carries

nerve impulses away from the cell body) terminal end, they are also known as the presynaptic

terminal. (Pre-synaptic neuron, this is a neuron also called nerve cell that fires the

neurotransmitter as a result of an action potential entering its axon terminal). The presynaptic
cleft, presynaptic terminal, and receiving dendrite of the next cell together form a junction

known as the synapse.

When a nerve impulse arrives at the presynaptic terminal of one neuron, neurotransmitter-filled

vesicles migrate through the cytoplasm( the semifluid substance of a cell that is external to the

nuclear membrane and internal to the cellular membrane) and fuse with the presynaptic terminal

membrane. The neurotransmitter molecules are then released through the presynaptic membrane

and into the synaptic cleft. In milliseconds, they travel across the synaptic cleft to the

postsynaptic membrane of the adjoining neuron, where they then bind to receptors. Receptor

activation results in either the opening or the closing of ion channels in the membrane of the

second cell, which alters the cell’s permeability. In many instances, the change in permeability

results in depolarization, causing the cell to produce its own action potentials, thereby initiating

an electrical impulse. In other cases, the change leads to hyperpolarization, which prevents the

generation of an action potential by the second cell.

The termination of neurotransmitter activity happens in several different ways, the molecules

may diffuse out of the synaptic cleft, away from the receptive cell. They also can be taken back

up into the presynaptic terminal via transporter molecules, or they may be metabolized by

enzymes in the synaptic cleft.

TYPES OF NEUROTRANSMITTERS
Different types of neurotransmitters have been identified and there are more than 40

neurotransmitters in the human nervous system; Based on chemical and molecular properties, the

major classes of neurotransmitters include amino acids, such as glutamate and glycine;

monoamines such as dopamine and norepinephrine; peptides such as adenosine triphosphate

(ATP). Some gaseous substances, such as nitric oxide, can also act as neurotransmitters, as can

endogenous substances are known as trace amines, which are related chemically to the

monoamines; examples include tryptamine and the phenethylamines.

The first neurotransmitter to be discovered was a small molecule called acetylcholine. It plays a

major role in the peripheral nervous system, where it is released by motor neurons of the

autonomic nervous system. It also plays an important role in the central nervous system in

maintaining cognitive function. Damage to the cholinergic neurons of the CNS is associated with

Alzheimer disease.

Glutamate is the most powerful excitatory neurotransmitter of the central nervous system which

ensures homeostasis with the effects of GABA. It is also the primary excitatory transmitter in the

central nervous system. Conversely, a major inhibitory transmitter is its derivative Gama-

aminobutyric acid (GABA), while another inhibitory neurotransmitter is the amino acid called

glycine, which is mainly found in the spinal cord. It is secreted by neurons of the many sensory

pathways entering the central nervous system, as well as the cerebral cortex.
Dopamine these are monoamines, it is secreted by the neurons of the substantia nigra. It is

considered a special type of neurotransmitter because its effects are both excitatory and

inhibitory. Which effect depends on the type of receptor that dopamine binds to. There are

several dopamine pathways in the brain, and this neurotransmitter is involved in many functions,

including motor control, reward and reinforcement, and motivation.

Noradrenaline (or norepinephrine) is another monoamine, it is an excitatory neurotransmitter

produced by the brainstem, hypothalamus, and adrenal glands and released into the bloodstream,

it is the primary neurotransmitter in the sympathetic nervous system where it works on the

activity of various organs in the body to control blood pressure, heart rate, liver function and

many other functions. It increases the level of alertness and wakefulness.

Neurons that use serotonin (another monoamine) project to various parts of the nervous system.

As a result, serotonin is involved in functions such as sleep, memory, appetite, mood, and others.

It is also produced in the gastrointestinal tract in response to food.

Histamine, the last of the major monoamines, plays a role in metabolism, temperature control,

regulating various hormones and controlling the sleep-wake cycle, amongst other functions.

DISORDERS ASSOCIATED WITH NEUROTRANSMITTERS

● Alzheimer’s Disease: This disease is a neurodegenerative disorder characterized by

learning and memory impairments. It is associated with a lack of acetylcholine in certain

regions of the brain.

● Depression: it is believed to be caused by depletion of norepinephrine, serotonin, and

dopamine in the central nervous system. Hence, pharmacological treatment of depression

aims at increasing the concentrations of these neurotransmitters in the central nervous

system.

● Schizophrenia: Schizophrenia, which is a severe mental illness, has been shown to

involve excessive amounts of dopamine in the frontal lobes, which leads to psychotic

episodes in these patients. The drugs schizophrenic conditions.

● Parkinson’s disease: the destruction of the substantia nigra leads to the destruction of the

only central nervous system source of dopamine. Dopamine depletion leads to

uncontrollable muscle tremors seen in patients suffering from Parkinson’s disease.

● Epilepsy: some epileptic conditions are caused by the lack of inhibitory

neurotransmitters, such as GABA, or by the increase of excitatory neurotransmitters, such

 as glutamate. Depending on the cause of the seizures, the treatment is aimed to either

increase GABA or decrease glutamate.

● Huntington’s Disease: Besides epilepsy, a chronic reduction of GABA in the brain can

lead to Huntington’s disease. Even though this is an inherited disease related to an

abnormality in DNA, one of the products of such disordered DNA is the reduced ability

of the neurons to take up GABA. There is no cure for Huntington’s disease, but we still

can treat symptoms by pharmacologically increasing the amount of inhibitory

neurotransmitters.

● Myasthenia gravis: it is a rare chronic autoimmune disease characterized by the

impairment of synaptic transmission of acetylcholine at neuromuscular junctions, leading

to fatigue and muscular weakness without atrophy.

Most often, myasthenia gravis results from circulating antibodies that block acetylcholine

receptors at the postsynaptic neuromuscular junction. This inhibits the excitatory effects of

acetylcholine on nicotinic receptors at neuromuscular junctions. In a much rarer form, muscle

weakness may result from a genetic defect in parts of the neuromuscular junction which is

inherited, as opposed to developing through passive transmission from the mother’s immune

system at birth or through autoimmunity later in life.

REFERENCES

Electrochemical gradient. (2016, April 15). Retrieved April 23, 2016 from Wikipedia:

https://en.wikipedia.org/wiki/Electrochemical_gradient.

Fundamental Neuroscience, Third Edition.

John P. J. Pinel (1996). Biopsychology. Allyn & Bacon.

Kandel, E.R., Schwartz, J.H., and Jessell, T.M. (1995). Nerve cells and behavior. In Essentials of
neuroscience and behavior (pp. 31-35). Norwalk, CT: Appleton & Lange.

Kandel, E.R., Schwartz, J.H., and Jessell, T.M. (1995). Membrane potential. In Essentials of
neuroscience and behavior (pp. 133-147). Norwalk, CT: Appleton & Lange.

Larry R. Squire, Darwin Berg, Floyd Bloom, Sascha du Lac, Anirvan Ghosh (2008).

Luigi Galvani. (2016, April 16). Retrieved April 23, 2016 from Wikipedia:

https://en.wikipedia.org/wiki/Luigi_Galvani.

Mauricio J. Giuliodori, and Stephen E. DiCarlo (2004). Myelinated Vs. Unmyelinated Nerve
Conduction: A Novel Way Of Understanding The Mechanisms. Advances in Physiological
Education.

Nicholls, J.G., Martin, A.R., Wallace, B.G., and Fuchs, P.A. (2001). Ionic basis of the resting
potential. In From neuron to brain(4th ed., pp. 77-90). Sunderland, MA: Sinauer Associates.

Nicholls, J.G., Martin, A.R., Wallace, B.G., and Fuchs, P.A. (2001). Signaling in nerve cells. In
From neuron to brain (4th ed., pp. 9-15). Sunderland, MA: Sinauer Associates.
Openstax College, Biology. (2015, September 29). Nerve impulse transmission within a neuron.
In OpenStax CNX. Retrieved from http://cnx.org/contents/GFy_h8cu@9.87:cs_Pb-GW@5/How-
Neurons-Communicate.

Purves, D., Augustine, G.J., Fitzpatrick, D., Katz, L.C., LaMantia, A.-S., McNamara, J.O., and
Williams, S. M. (1997). How ionic movements produce electrical signals. In Neuroscience (2nd
ed.). Sunderland, MA: Sinauer Associates. Retrieved from
http://www.ncbi.nlm.nih.gov/books/NBK11054/.

Purves, D., Augustine, G.J., Fitzpatrick, D., Katz, L.C., LaMantia, A.-S., and McNamara, J.O.
(1997). Electrical signals of nerve cells. In Neuroscience (pp.37-50). Sunderland, MA: Sinauer
Associates.

Reece, J. B., Urry, L. A., Cain, M. L., Wasserman, S. A., Minorsky, P. V., and Jackson, R. B.
(2011). Ion pumps and ion channels establish the resting potential of a neuron. In Campbell
biology (10th ed., pp. 1064-1066). San Francisco, CA: Pearson.

Richard H. Hall (1998). Neural Communication

Sadava, D. E., Hillis, D.M., Heller, H.C., and Berenbaum, M.R. (2009). How do neurons

generate and transmit electrical signals? In Life: The science of biology (9th ed., pp. 948-956).

Sunderland, MA: Sinauer Associates.