Structure and Function of the Cells in the Nervous System

The four structures of a neuron

1.)Cell body, or soma, 2.) dendrites, 3.) axon, 4.) terminal buttons

Ion

A charged atom, their are 2 types. Particles with the same type of charge repel each other. While the opposites attract.

ligand

A chemical that attaches to a binding site. Neurotransmitters are naturally occurring _____, produced and released by neurons. But other chemicals found in nature (primarily in plants or in the poisonous venoms of animals) can serve as ____too. In addition, artificial ____ can be produced in the laboratory. Its attaching qualities can be equated to glue.

multiple sclerosis

A chronic disease of the central nervous system.It damages the myelin protein produced by Oligodendrocytes, thus, the myelin of PNS are spared.(ex of symptoms: experiencing double vision, feeling unsteady on one's feet, and tingling sensations in one's hands, heart attaches are perhaps the most serious symptom). MRI scan might show white matter tracks that will be cleaned up by axons.

Cytoplasm

A jellylike fluid inside the cell in which the organelles are suspended. It fills the space outlined by the membrane. It is a semi-liquid component

threshold of excitation,

A set point for depolarization to trigger the main electrical event in an axon,which is the Action potential

Golgi apparatus

A special form of smooth endoplasmic reticulum. some complex molecules made up of simple molecules are assembled here. Alsoseres as a wrapping or packaging agent. (Ex. secretory cells (such as those that release hormones) wrap their product in a membrane produced by the ____

Electrolyte

A substance that is dissolved in solution and some of its molecules split or dissociate into electrically charged atoms or ions

endomembrane system

A system of intracellular membranes that exchange material with one another, consisting of the Golgi apparatus, endoplasmic reticulum, and lysosomes when present.

Axon

A threadlike extension of a neuron that carries nerve impulses away from the cell body. It is a long slender tube, often covered by myelin sheath. The outer surface of this unit carries information from the cell body to the terminal buttons. (ex. It functions like an electrical cord carrying an electrical message from an outlet to an appliance)

voltage-dependent ion channels

Another name for this is the sodium channels. they are only opened by changes in the membrane potential. At this point, the interior of the cell starts to become much more positive. Only opens up for a breif second, about 1 ms. then they close and cannot open up again until the next action potential.(refractory)

Membrane potential

Any difference in charge (positive or negative) across the membrane

1st step in generating an action potential

As soon as the threshold of excitation is reached, the so- dium channels in the membrane open, and Na+ rushes in, propelled by the forces of diffusion and electrostatic pressure. The opening of these channels is triggered by reduction of the membrane potential (depolarization); they open at the point at which an action potential begins: the threshold of excitation. Because these channels are opened by changes in the membrane potential, they are called voltage-dependent ion channels. The influx of positively charged sodium ions produces a rapid change in the membrane potential, from -70 mV to +40 mV.

3rd step in generating an action potential

At about the time the action potential reaches its peak (in approximately 1 msec), the sodium channels become refractory—the channels become blocked and cannot open again until the membrane once more reaches the resting potential. At this time, no more Na+ can enter the cell.

Dendrites

Branchlike parts of a neuron that are specialized to receive information. (Have receptors). They are the receiving component of a neuron. (ex. antennas that detect radio or wifi signals)

4th step in generating an action potential

By now, the voltage-dependent potassium channels in the membrane are open completly, letting K+ ions move freely through the membrane. At this time, the inside of the axon is positively charged, so K+ is driven out of the cell by diffusion and by electrostatic pressure. This outflow of cations causes the membrane potential to return toward its normal value. As it does so, the potassium channels begin to close again.

Mitochondria

Cells that are shaped like oval beads and are formed from a double membrane. The inner membrane is wrinkled, and the wrinkles make up a set of shelves (cristae) that fill the inside of the bead. It performs a vital role in the economy of the cell; many of the biochemical steps that are involved in the extraction of energy from the breakdown of nutrients take place on the cristae, controlled by enzymes located there. Cells provide ____ with nutrients and ___ provide cells with a special molecule adenosine triphosphate (ATP). Power house of cell (in this case neuron)

Interneurons

Central nervous system neurons that internally communicate and intervene between the sensory inputs and motor outputs. (Fun fact: They reside only in the CNS)

Genes

DNA segments that serve as the key functional units in hereditary transmission. They are active portions of the chromosomes, which cause production of mRNA

Nucleolus

Found inside the nucleus and produces ribosomes (small structures involved in protein synthesis)

Exocytosis

Happens after the Golgi Apparatus wraps certain cells with a membrane. This happens when a cell secretes its product. The membrane-wrapped product migrates to the inside of the cell, fuses with the membrane, and bursts, spilling its content into the fluid surrounding the cell. Neurons communicate with one another by secreting chemicals by this means.

role of inhibition

Inhibitory signals arising from the brain can prevent the withdrawal reflex from causing the person to drop the casserole

local interneurons

Interneurons that form circuits with nearby neurons and analyze small pieces of information. Short axons

Nucleus

It can be found inside of the soma. It gives demands to all of the organelles in the body. It is enclosed by nuclear membrane. The nucleolus and the chromosomes reside inside the ______.

Peripheral Nervous System (PNS)

It consist of the nerve tissue located outside of the brain and spinal cord. The sensory organs of muscles, and motor neurons that connect the central nervous system (CNS) to the rest of the body(PNS).

Action potential

It is a a burst of rapid depolarization followed by hyperpolarization. This spread of depolarization followed by hyperpolarization begins at the point where the soma meets the axon and propagates like a wave all the way to the end of the terminal buttons, informing the terminal buttons to release neurotransmitters into the synapse. This electrical charge is the result of a balance between two opposing forces: diffusion and electro static pressure. The ____consists of a series of changes in opening and closing of ion channels and the resulting distribution of ions. First, the ___ must reach the threshold of excitation. Then, sodium channels in the membrane open, and Na+ rushes in, propelled by the forces of diffusion and electrostatic pressure. Remains constant as it travels down the axon. That is, its size remains undiminished.

Astrocytes

It is also known as the star cell. It provides physical support to neurons and clean up debris (when certain cells in CNS die.These cells are able to travel around the CNS; they extend and retract their processes (pseudopodia, or "false feet") and glide about the way amoebas do. ) within the brain. They produce some chemicals that neurons need to fulfill their functions. They help to control the chemical composition of the fluid surrounding neurons by actively taking up or releasing substances whose concentrations must be kept within critical levels. Finally, ____ are involved in providing nourishment to neurons. Some of the processes (arms for the cell) of the cell wrap around blood vessels. Other processes are wrapped around parts of neurons, so the somatic and dendritic membranes of neurons are largely surrounded by ______. Camillo Golgi insinuated that this cell supplied neurons with nutrients from the capillaries and disposed of their waste products (Golgi, 1903). He thought that nutri- ents passed from capillaries to the cytoplasm of the ____ and then through the cytoplasm to the neurons. (Supplies cell with most nutrients). They receive glucose from capillaries and break it down to lactate,They then release lactate into the extracellular fluid that surrounds neurons, and neurons take up the lactate, transport it to their mitochondria, and use it for energy.this process provides neurons with a fuel that they can metabolize even more rapidly than glucose. They store a small amount of a carbohydrate called glycogen that can be broken down to glucose and then to lactate when the metabolic rate of neurons in their vicinity is especially high. They also serve as the matrix that holds neurons in place—the "nerve glue," so to speak. These cells also surround and isolate synapses, limiting the dispersion of neurotransmitters that are released by the terminal buttons.

Microelectrodes

It is an electrical recording technique using very small sensors. They can be inserted into a neuron to record changes in electrical activity across the axon membrane. When inserted into an axon at rest, the ____ will detect a negative charge inside the membrane. Most neurons are approximately 70 units, or -70 mV, more negatively charged inside the axon compared to outside.

Synapse

It is an empty space, dendrites transmit neural messages across this space. It is located between the terminal buttons

Endoplasmic Reticulum (ER)

It is an extensive membrane that has 2 forms. Rough and Smooth. Both types consist of parallel layers of the same membrane that encloses the cell.

postsynaptic potential

It is produced by neurotransmitters. The procedure consist of a brief depolarizations or hyperpolarizations—that increases or decreases the rate of firing of the axon of the postsynaptic neuron.

Soma

It is the cell body, it also processes all of the input received from the dendrites within a cell. It contains the nucleus.

Cytoskeleton/Microtobules

It resides within the interior of the neuron. It is network of fibers (strands of proteins) that holds the cell together, helps the cell to keep its shape, and aids in movement. It is made up of 3 kinds of proteins strands, linked together. They form a cohesive mass. The thickest of these strands is known as ______, which are bundles of 13 protein filaments arranged around a hollow core.

rate law

Law the refers to the principle of variations in the intensity of a stimulus or other information being transmitted in an axon are represented by variations in the rate at which the axon fires

upper motor neurons

Motor neurons that are located from the brain and spinal cord

afferent neurons

Nerve cells that carry impulses towards the central nervous system. (PNS to CNS)

efferent neurons

Nerve cells that conduct impulses away from the central nervous system. (CNS to PNS)

saltatory conduction

Nerve impulse regeneration Rapid transmission of a nerve impulse along an axon, resulting from the action potential jumping from one node of Ranvier to another, skipping the regions of membrane that have myelin sheath. It has 2 advantages. 1.)The first is economic. Sodium ions enter axons during action potentials, and these ions must eventually be removed. Sodium- potassium transporters must be located along the entire length of unmyelinated axons because Na+ enters everywhere. However, because Na+ can enter myelinated axons only at the nodes of Ranvier, much less gets in, and consequently much less has to be pumped out again. Therefore, myelinated axons expend much less energy to maintain their sodium balance. 2.) The second advantage to myelin is speed. Conduction of an action potential is faster in a myelinated axon because the transmission between the nodes is very fast. Increased speed enables an animal to react faster and (undoubtedly) to think faster.

5th step in generating an action potential

Once the membrane potential returns to normal, the sodium channels reset so that another depolarization can cause them to open again. The potassium channels are closed completly

2nd step in generating an action potential

Potassium channels open and k+ begins to leave the cell

Schwann cells

Supporting cells of the peripheral nervous system responsible for the formation of myelin. Most axons in the PNS are myenelated. Each segment of myelin sheath in PNS consists of a single ____ cell wrapped many times around the axon. In the PNS a ____ provides myelin for only one axon, and the entire _____cell not merely a part of it surrounds the axon. If nerves are damaged ____ cells aid in the digestion of dying and damaged axons. Then they arrange themselves in a series of cylinders that act as guides for regrowth of the axons. The distal portions of the severed axons die, but the stump of each severed axon grows sprouts, which then spread in all directions. If one of these sprouts encounters a cylinder provided by a ______ cell, the sprout will grow through the tube quickly (at a rate of up to 3-4 mm a day), while the other, nonproductive sprouts wither away. If the cut ends of the nerve are still located close enough to each other, the axons will reestablish connections with the muscles and sense organs they previously served. Unfortunately, the glial cells of the CNS are not as cooperative as the supporting cells of the PNS. If axons in the brain or spinal cord are damaged, new sprouts will form, as in the PNS. However, the budding axons encounter scar tissue produced by the astrocytes, and they cannot penetrate this barrier. During development, axons have two modes of growth. The first mode causes them to elongate so that they reach their target, which could be as far away as the other end of the brain or spinal cord. _______ provide this signal to injured axons. The second mode causes axons to stop elongating and begin sprouting terminal buttons because they have reached their target.

Rough Endoplasmic Reticulum

The ___ endoplasmic reticulum contains ribosomes. The proteins produced by the ribosomes that are attached to the ___ endoplasmic reticulum is destined to be transported out of the cell or used in the membrane. Unattached ribosomes are also distributed around the cytoplasm; the unattached variety appears to produce protein for use within the neuron

Down side of the blood-brain barrier

The blood-brain barrier can prevent therapeutic molecules from entering the CNS. Development of drug molecules that target sites in the brain is often complicated by the difficulty of getting the molecules past the blood- brain barrier. Crossing the blood-brain barrier is consid- ered a key obstacle in developing drugs to treat diseases such as Alzheimer's and Parkinson's.

axon hillock

The conical region of a neuron's axon where it joins the cell body; typically the region where nerve signals is generated. It determines whether an action potential gets fired or not. active conduction happens at this place. (It also happens at the nodes of raniver)

mRNA (messenger RNA)/Protein production

The form of RNA which is created as a blueprint from DNA; carries instructions for making a protein. It receives a copy of the genetic code for DNA. It leaves the nuclear membrane and attaches to ribosomes. _____are produced through a two-step process. In the first step transcription, information from DNA (which cannot leave the nucleus) is transcribed into a portable form _____.____ takes this information to the ribosomes for the second step of the process "translation". During translation, the ribosomes use the information from _____ and create proteins. (EX. Cook book cannot move on its own( represents DNA in nucleus), you take a pic and make recipe's portable in phone, go, take recipes home and assemble material to make complete cake). ____ proteins are important in cell functions

6th step in generating an action potential

The membrane actually overshoots its resting value (-70 mV) and only gradually returns to normal as the potassium channels finally close. Eventually, sodium- potassium transporters remove the Na+ ions that leaked in and retrieve the K+ ions that leaked out.

Glia

The most important supporting cells of the central nervous system. Glues the CNS together and more. They buffer neurons physically and chemically from the rest of the body. They surround neurons and hold them in place, controlling their supply of nutrients and some of the chemicals they need to exchange messages with other neurons; they insulate neurons from one another so that neural messages do not get scrambled; and they even act as housekeepers, destroying and removing the carcasses of neurons that are killed by disease or injury. Their are several types, each of which play an important role in the CNS

enteric nervous system

The nervous system of the gastrointestinal tract. It controls secretion and motility within the intestines, and is linked to the central nervous system. It is also known as the intrinsic nervous system. Makes up the second brain. Has its own reflexes, sensory fibers, etc. 90% of what is going on in the gut is due to serotonin.

synaptic transmission

The primary means of communication between neurons. it is the transmission of messages from one neuron to another across a synapse. This happens because of neurotransmitters that go from 1 neuron to the other.

Depolarization

The process during the action potential when sodium is rushing into the cell causing the interior to become more positive. This is precisely what causes the action potential: A brief increase in the permeability of the membrane to Na+. K+ opens up and releases the k+ from the cell, which makes the cell more positive. Reduction of membrane potential

Diffusion

The process whereby molecules distribute them- selves evenly throughout the medium in which they are dis- solved. This only happens when their are no forces preventing the molecules from ______. Molecules typically move from areas of high concentration to low concentration. Molecules are constantly in motion. Only at absolute zero do molecules lose the ability to move. They typically push one another away.

blood-brain barrier

Their is a barrier that exist between the blood and the fluid that surrounds the cells of the brain. (Over one hundred years ago, Paul Ehrlich discovered that if a blue dye is injected into an animal's bloodstream, all tissues except the brain and spinal cord will be tinted blue. However, if the same dye is injected into the fluid-filled ven- tricles of the brain, the blue color will spread throughout the CNS). Some substances can cross the _____. Thus it is selectively permeable. In most of the body the cells that line the capillaries do not fit together absolutely tightly. Small gaps are found between them that permit the free exchange of most substances between the blood and the fluid outside the capillaries that surrounds the cells of the body. In the CNS the capillaries lack these gaps; therefore, many substances cannot leave the blood. Thus, the walls of the capillaries in the brain constitute the _____. Other substances must be must be actively transported through the capillary walls by special proteins. (ex. glucose transporters bring the brain its fuel, and other transporters rid the brain of toxic waste products). The major fxon of the ____ is to facilitate the regulation of extracellular fluid in the brain to help for the transmission of messages between neurons, so that brain fxon will be good and not disrupted. The__ prevents chemicals from food to reach our brain.

Lyosomes

These are small sacs, which are created in the golgi apparatus. They contain enzymes that break down substances no longer needed by the cell. These products are then recycled and excreted by the cell

Voltage-dependent potassium channels

These channels begin to open, allowing potassium to leave the cell. These ______ are less sensitive than voltage-dependent sodium channels. That is, they require a greater level of depolarization before they begin to open, and they begin to open later than the sodium channels.

Enzymes

They direct the chemical processes of a cell by controlling chemical reactions. They are proteins that act as biological catalysts. They cause a chemical reaction to take place without becoming a part of the final product themselves. Each ____ is customized to correlate with each protein in order to create a compound. Some ____ break down molecules. While others put them together.

cranial nerves

They emerge directly from the brain; technically part of the PNS. However, the optic nerves are an exception to this rule. CN2 is located in CNS

dendritic spines

This is where most synapses occur. It is the smooth surface of a dendrite. small protrusions that stud the dendrites of several types of large neurons in the brain. Some synapses can occur on the soma and on other axons.

binding site

This is where neurotransmitters exert their effects on cells by attaching to this region. It is connected t a receptor molecule. A molecule of the chemical fits into the _____ the way a key fits into a lock: The shape of the ______ and the shape of the molecule of the neurotransmitter are complementary.

all-or-none law.

This law states that an action potential either occurs or does not occur, and, once triggered, it is transmitted down the axon to its end. An action potential always remains the exact same size, without growing or diminishing. High rates of firing of an action potential equal strong muscle contractions. While low rates of firing of an action potential equal weak muscle contractions.

Chromosomes

This unit consist of long strands of DNA. It contains the organisms genetic makeup.

Membrane

This unit defines the boundary of the neuron. It consist of a double layer of lipids (fat like) molecules. Embedded in the _____ are a series of different protein molecules that have special functions.

Nerves

This unit is needed to help the CNS communicate with the rest of the body through ____ attached to the spinal cord and brain. They are bundles of thousands of individual neurons, all wrapped in a tough, protective membrane. (ex. looks like cables underneath microscope)

Grey matter and White matter

Together both of these substances can make up tracts

Oligodendrocytes

Type of glial cell that provides support to axons and to produce the myelin sheath. The sheath is roughly 1 mm long, with a small (1-2 nano meter) portion of uncoated axon between segments. A given ______ produces up to 50 segments of myelin. During the development of the CNS, _____ form processes shaped something like canoe paddles. Each of these paddle-shaped processes then wraps itself many times around a segment of an axon and, while doing so, produces layers of myelin. Each paddle thus becomes a segment of an axon's myelin sheath.

Terminal buttons/Neurotransmitter

When an action potential traveling down an axon reaches the ______, they secrete a chemical called a _____. This chemical (there are many different ones in CNS) either excites or inhibits the receiving cell and thus helps to determine whether an action potential occurs in its axon. (Ex. spray bottle releasing chemicals into the synapse). Individual neurons receive information from the ____ of axons of other neurons. It forms synapses with other neurons.

Phagocytosis

When astrocytes contact a piece of debris from a dead neuron, they push themselves against it, finally engulfing and digesting it. If there is a considerable amount of injured tissue to be cleaned up, astrocytes will divide and produce enough new cells to do the task. Once the dead tissue has been broken down, a framework of astrocytes will be left to fill in the vacant area, and a specialized kind of astrocyte will form scar tissue, walling off the area.

Hyperpolarization

When the inside of an axon becomes more negative relative to the outside. (ex. -80 mV)

Depolarization

When the inside of the axon becomes more positive. (ex. -50mV is less than -70mV, so it is more positive)

Everything else In neuron

_______ is composed of grey matter

Neuron

a specialized cell of the nervous system that initiates, integrates, and conducts electrical signals. The information processing and the information transmitting element of the nervous system. constitute only about half the volume of the CNS. have a very high rate of metabolism but have no means of storing nutrients, they must constantly be sup- plied with nutrients and oxygen or they will quickly die.

axoplasmic transport

an active process that propels substances along microtubule "tracks" that run inside the length of the axon

ion channels

channel proteins that transport ions through passages (pores) that can open or close when an_____ is open, specific ions can flow through the pores and thus enter and leave the cell. Neural membranes contain thousands of ____. (ex. For example, each sodium channel can admit up to 100 million ions per second when it is open. Thus, the permeability of a membrane to a particular ion at a given moment is deter- mined by the number of ____ that are open. The action potential consists of a series of changes in opening and closing of _____ and the resulting distribution of ions.

amyotrophic lateral sclerosis (ALS)

condition of progressive deterioration of motor nerve cells resulting in total loss of voluntary muscle control; symptoms advance from muscle weakness in the arms and legs, to the muscles of speech, swallowing, and breathing, to total paralysis and death; also known as Lou Gehrig disease. (Both the upper and lower neurons start dying and affects motor function)

relay interneurons (Projection)

connect circuits of local interneurons in one region of the brain with those in other regions. They are the largest class of neurons. They have longer axons to connect. Circuits connect from interneurons within different regions of the brain. (These circuits are needed to perform functions essential to tasks such as perceiving, learning, remembering, deciding, and controlling complex behaviors)

lower motor neurons

connected with muscles and glands. From the spinal chord down to the body

Central Nervous System (CNS)

consists of the brain and spinal cord. Encased within the skull and spinal column.

sodium-potassium pump

continuously pushes Na+ out of the axon. consists of a large number of protein molecules embedded in the membrane, driven by energy provided by molecules of ATP produced by the mitochondria. These molecules, known as sodium- potassium transporters, exchange Na+ for K+, pushing three sodium ions out for every two potassium ions they push in.

withdrwal reflex...

contraction of a muscle that causes it to pulll away from an irritating stimulus.

myelin sheath

covers the axon of the neurons and helps speed neural impulses. This happens because of 3 things. 1.) It provides insulation for the axon. 2.) An electrical signal that has passive transmission underneath the ______, also conduction (Salutatory conduction) and regeneration of AP'S between the nodes. This is ethical because conserves energy for the neuron. 3.) Lastly, it widens diameter, which allows for better passage of the action potential, with less resistance. It is also made up of white matter.

spinal nerves

emerge from segments of the spinal cord; PNS. The dorsal root is on the back. While the ventral root is on the stomach. It carries a mixture of afferent and efferent nerve signals. They are located at each segment of the spinal cord.

extracellular fluid

fluid outside the cell. (Na+ and Cl- are predominantly found here. The force force diffusion pushes Cl- outside). Typically this part of the cell is more negative.

Retrograde axoplasmic transport

mechanism responsible for transporting a protein known as dynein to the soma, which enter through the terminal buttons of the axon. This type of transport is slower than anterograde transport

anterograde axoplasmic transport

movement down the axon away from soma and towards the terminal buttons. The form of transport is accomplished by molecules of a protein called kinesin. In the cell body, kinesin molecules (the molecules resemble a pair of legs) attach to the item being transported down a microtubule, carrying cargo to its destination. Energy is supplied by ATP molecules produced by mitochondria. It is very fast, up to 500 (mm) per a day

Anions

negatively charged ions (ex.Cl-)

presynaptic neuron

neuron that sends the signal

sensory neurons (afferent)

neurons that carry incoming information from the sensory receptors to the brain and spinal cord. (PNS to CNS) (Ex: Getting hit will make you feel pain. That is your peripheral nervous system sending a message to your central nervous system. It is saying that you are in pain). (Biological example: information in the form of light, sound waves, odors, tastes, or contact with objects, is gathered from the environment with these neurons). Movements are contracted following the four structures: 1.) cell body(soma), 2.)dendrites,3.) axon, 4.) terminal buttons

motor neurons (efferent)

neurons that carry outgoing information from the brain and spinal cord to the muscles and glands. (CNS to PNS). (Ex: You are reaching for an apple. In doing this, your Central nervous system is sending a demand to your peripheral nervous system. (nerves, skeletal muscles). This results in you to physically pick up the apple). PNS is controlled by

area postrema

part of the brain that controls vomiting. The blood-brain barrier is much weaker there, permitting neurons in this region to detect the presence of toxic substances in the blood. (A barrier around the area prevents substances from diffusing from this region into the rest of the brain.) A poison that enters the circulatory system from the stomach can thus stimulate the area to initiate vomiting.

Cations

positively charged ions (ex.Na+)

Microglia

smallest of the glial cells. Like some types of astrocytes, they act as phagocytes, engulfing and breaking down dead and dying neurons. But, in addition, they serve as one of the representatives of the immune system in the brain, protecting the brain from invading microorganisms. They are primar- ily responsible for the inflammatory reaction in response to brain damage.

Smooth Endoplasmic Reticulum

the ___ endoplasmic reticulum provides channels for the segregation of molecules involved in various cellular processes. Lipid (Fat-like) molecules are also produced here

electrostatic pressure

the attractive force between atomic particles charged with opposite signs or the repulsive force between atomic particles charged with the same sign. When substances are dissolved in water, they split into 2 parts. Each with an opposing electrical charge.moves ions from place to place: Cations are pushed away from regions with an excess of cations, and anions are pushed away from regions with an excess of anions.

sympathetic nervous system

the division of the autonomic nervous system that arouses the body, mobilizing its energy in stressful situations. Fight or Flight.

parasympathetic nervous system

the division of the autonomic nervous system that calms the body, conserving its energy. Rest and Digest.

somatic nervous system

the division of the peripheral nervous system that controls the body's skeletal muscles

intracellular fluid

the fluid contained within cells.(ex. K+ is predominantly found here, but the force of diffusion tends to push it out ) Typically this part of the cell is more positive.

corpus callosum

the large band of neural fibers connecting the two brain hemispheres and carrying messages between them. It is also a colossal projection neuron

postsynaptic neuron

the neuron on the receiving end of the synapse

autonomic nervous system

the part of the peripheral nervous system that controls the glands and the muscles of the internal organs (such as the heart). Its sympathetic division arouses; its parasympathetic division calms. Human is not consciously aware of what is going on.

Resting potential

when the neuron is at rest and not involved in communicating with any other neurons . The membrane potential remains at approximately -70mV