THE STRUCTURE AND FUNCTION OF NEURONS
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THE STRUCTURE AND FUNCTION OF SENSORY, RELAY AND MOTOR NEURONS. THE PROCESS OF SYNAPTIC TRANSMISSION EXCITATION AND INHIBITION
NEUROTRANSMITTERS
Neurotransmitters are chemical messengers that your body can't function without. Their job is to carry chemical signals (messages) from one neuron to the next target. The next target can be other neurons, a muscle or a gland. Each neurotransmitter attaches to a different receptor. For example, dopamine molecules attach to dopamine receptors. When they attach, it triggers an action in the target cells.
WHAT DO NEUROTRANSMITTERS DO?
The brain needs neurotransmitters to regulate many necessary functions, including:
Heart rate
The fight or flight response
Breathing
Sleep cycle wake cycle
Digestion
Mood
Concentration
Regulating appetite
Muscle movement
Memory
Low levels of any neurotransmitter can lead to problems, including fibromyalgia, Parkinson’s disease and Alzheimer's disease. Imbalances can also cause psychiatric conditions such as anxiety, depression, Schizophrenia and violence.
Over 100 neurotransmitters have been identified and are still be identified but only seven do most of the work These seven neurotransmitters are acetylcholine, dopamine, gamma-aminobutyric acid (GABA), glutamate, histamine, norepinephrine, and serotonin).
After neurotransmitters deliver their messages, the body breaks them down or recycles them.
TYPES OF NEUROTRANSMITTERS
Neurotransmitters have different types of actions:
Excitatory neurotransmitters encourage a target cell to take action.
Inhibitory neurotransmitters decrease the chances of the target cell taking action. In some cases, these neurotransmitters have a relaxation-like effect.
Modulatory neurotransmitters can send messages to many neurons at the same time. They also communicate with other neurotransmitters.
Some neurotransmitters can carry out several functions depending on the type of receptor they connect to.
ACETYLCHOLINE
PRIMARY FUNCTIONS: Acetylcholine is an excitatory neurotransmitter with many roles. It is mainly responsible for stimulating muscles. It activates the motor neurons that control the skeletal muscles. It is also concerned with regulating the activities in certain brain areas, which are associated with attention, arousal, learning, and memory. Unlike other key neurotransmitters, acetylcholine is not made from amino acids. Its primary building block is choline, which doesn't have to compete for entry into your brain. Therefore, the more choline you consume, the more acetylcholine you can produce.
OPTIMAL LEVELS
Focus
Attention
Memory
Feelings of pleasure
Muscle contraction
Learning
IMBALANCE
People with Alzheimer's disease are usually found to have a substantially low level of Acetylcholine.
Mental and physical fatigue Inattention
ADD
ADHD
Mental fatigue
Loose skin
Brown spots on the brain
DOPAMINE
Dopamine is a very important chemical that regulates thought movement, attention, motivation and learning.
It’s synthesised by neurons in the middle of the brain, but it's released all over in small and large doses in small doses.
It activates d2 receptors which reinforces ongoing thoughts and movements. If you're eating pizza, pleasant tastes will activate dopamine neurons, raising dopamine concentrations in the brain, so you'll feel motivated and keep on eating.
If you're experiencing something new or expecting something good, dopamine levels can rise to 100%, and you'll feel excited and completely focused.
Being unfocused and easily distracted means your brain is low in dopamine; that's why Ritalin amphetamines and coffee help people with attention deficit disorder concentrate.
When something important, unexpected, or rewarding happens, large amounts of dopamine are released, which activate the D1 receptor and stimulate learning in the formation of new connections between neurons. Memories and habits all from this way.
All addictive drugs release large amounts of dopamine in the brain, but so does good food and drinking, sex and social pleasure and money.
Everything you want releases dopamine, and you want it because it releases dopamine.
Things are important and valuable only if they activate your dopamine neurons.
If you’re still reading this extract right now it’s because it's releasing dopamine.
Whatever you do when after reading this extract will be what releases most dopamine.
PRIMARY FUNCTIONS:
Dopamine has important roles in behaviour and cognition. Its primary function is to make humans move voluntarily because, unlike plants, most animals have to move to get food. If moving voluntarily and eating were not pleasurable, then humans would be reluctant to do either. Therefore, dopamine is also involved in pleasure, reward and punishment. In other words, everything that humans do that is pleasurable or rewarding results in dopamine production. As a result, addiction is a result of the dopamine reward pathway. All street drugs (illegal drugs) and psychotropic drugs (legal psychiatric medications ) work on the dopamine system as drugs are initially pleasurable.
Dopamine is also involved with motivation, punishment, sleep, mood, attention, working memory and learning.
Dopamine levels are depleted by stress or poor sleep. Alcohol, caffeine, and sugar all seem to diminish dopamine activity in the brain.
IMBALANCES
A LACK OF DOPAMINE CAUSES:
Anhedonia (no pleasure in life - world looks colourless); inability to love and/or no remorse about personal behaviour.
Attention deficits
Parkinson’s disease
Some types of Schizophrenia
Addiction to drugs (self-medicating)
EXCESS DOPAMINE CAUSES
Some types of Schizophrenia.
Hallucinations
Delusions
Paranoia
Mania
ENKEPHALINS AND ENDORPHINS
PRIMARY FUNCTIONS: These are opioids that, like the drugs heroin and morphine, modulate pain and inhibit pain signals. Endorphins and enkephalins have links to laughter, love, sex, and appetising food. Many people feel better after exercising. One reason for this may be that exercise boosts endorphin levels.
Endorphins and enkephalins are the body's natural painkillers. When a person is injured, pain impulses travel up the spinal cord to the brain. The brain then releases endorphins and enkephalins. Enkephalins block pain signals in the spinal cord and create and reduce stress. Endorphins are thought to block pain principally at the brain stem. Both are morphine-like substances whose functions are similar to those of illegal and legal opium-based drugs called opioids.
Opioids are a class of drugs that work on increasing endorphin and enkephalin availability in the brain they create a feeling of pleasure, reduce stress and promote a sensation of floaty, oceanic calm. They also depress physical functions like breathing and may produce physical dependence. Opioids either come from the opium poppy (The opium poppy is the key source for many narcotics, including morphine, codeine, and heroin) or are synthetic.
ILEGAL OPIATES:
Heroin
Fentanyl (a synthetic opioid 50–100 times more potent than morphine).
Desomorphine, known by the street name krokodil, is a powerful opioid derivative of codeine. Like heroin and other opioids, it has a sedative and analgesic effect and is highly addictive.
LEGAL OPIATES
Oxycodone (OxyContin®)
Hydrocodone (Vicodin®)
Codeine
Morphine
Methadone
ADRENALINE (USA = EPINEPHRINE)
PRIMARY FUNCTIONS:
Adrenalin (also known as epinephrine) plays a role in the body’s “fight-or-flight” response. It is both a hormone and a neurotransmitter. When a person experiences stress or fear, their body releases adrenalin. This increases heart rate and breathing and gives the muscles a jolt of energy. It also helps the brain make quick decisions. However, chronic stress can cause the body to release too much adrenalin. Over time, stress can lead to health problems such as decreased immunity, high blood pressure, diabetes, and heart disease.
Doctors can use adrenalin to treat some life-threatening conditions, including:
Anaphylaxis, a Severe Allergic Reaction (EPI PEN)
Asthma Attacks
Cardiac Arrest
Some Infections
Adrenalin’s ability to constrict blood vessels can decrease swelling that results from allergic reactions and asthma attacks. In addition, it can help the heart contract again if it has stopped during cardiac arrest.
OPTIMAL LEVELS
Arousal
Energy
Drive
Excitement
IMBALANCE
ADD
ADHD
Lack of ambition,
Lack of drive
Lack of energy Depression
NORADRENALIN (USA = NOREPINEPHRINE)
Noradrenalin is also utilised in the “fight or flight response. The brain requires noradrenalin to form new memories and to transfer them to long-term storage. This neurotransmitter also influences your metabolic rate.
GABA
Gamma-aminobutyric acid (GABA) is the central nervous system’s main inhibitor. It is a mood regulator, and experts have linked low levels of it with anxiety, depression, and schizophrenia.
Benzodiazepines, or “benzos,” are drugs that can treat anxiety. They work by increasing the action of GABA. This has a calming effect that can help treat anxiety attacks.
SEROTONIN
Serotonin is an inhibitory neurotransmitter. It is important for behaviour, sleep, and memory. It helps regulate emotional stability and maintains good mood, serenity and optimism. It promotes contentment and is responsible for normal sleep.
IMBALANCE
Low Serotonin levels produce insomnia, depression, lack of rational emotion, aggressive behaviour, increased sensitivity to pain, and sudden unexplained tears. It is also associated with obsessive-compulsive eating disorders and with increased carbohydrate cravings.
Anti-depressants such as selective serotonin reuptake inhibitors SSRIs boost serotonin levels by stopping the body from reabsorbing serotonin, leaving more serotonin to pass messages between nerve cells.
Doctors prescribe selective serotonin reuptake inhibitors (SSRIs) to treat a range of conditions, including:
depression
anxiety
post-traumatic stress disorder (PTSD)
obsessive-compulsive disorder (OCD)
migraine
KEYWORDS
ACTION POTENTIAL: An Impulse or nerve impulse is also known as an action potential; it is an electrical signal which travels along a nerve channel. Nerve impulse occurs due to the difference in electrical charge across the plasma membrane of a neuron.
AXON: Axon is a tube-like structure that carries electrical impulses from the cell body to the axon terminals that pass the impulse to another neuron.
AXON-TERMINALS: Axon terminals (also called synaptic boutons, terminal boutons, or end-feet) are distal terminations of the telocentric (branches) of an axon.
AXON-HILLOCK: The axon hillock acts as something of a manager, summing the total inhibitory and excitatory signals. If the sum of these signals exceeds a certain threshold, the action potential will be triggered, and an electrical signal will then be transmitted down the axon away from the cell body. The axon hillock connects to the axon, an important structure allowing the spread of an electrical signal called an action potential to travel down the axon.
CELL-BODY: Each neuron has a cell body with a nucleus, Golgi body, endoplasmic reticulum, mitochondria and other components.
DENDRITES: These are branch-like structures that receive messages from other neurons and allow the transmission of messages to the cell body.
EXCITATION & INHIBITION: A neurotransmitter is a signalling molecule secreted by a neuron to affect another cell across a synapse. The cell receiving the signal, any main body part or target cell, may be another neuron, but could also be a gland or muscle cell.
Mitochondria - produce energy to fuel cellular activities.
MYELIN-SHEAF: Myelin sheath is a substance which is found on neurons within the central nervous system (CNS) and the peripheral nervous system (PNS). Myelin sheath is the protective layer that wraps around the axons of neurons to aid in insulating the neurons and to increase the number of electrical signals being transferred.
NEURON: Neurons are the fundamental unit of the nervous system specialized to transmit information to different body parts. “Neurons are the building blocks of the nervous system. They receive and transmit signals to different parts of the body. This is carried out in both physical and electrical forms. Several different types of neurons facilitate the transmission of information. The sensory neurons carry information from the sensory receptor cells present throughout the body to the brain. Whereas, the motor neurons transmit information from the brain to the muscles. The interneurons transmit information between different neurons in the body.
NEUROTRANSMITTER: A neurotransmitter is a signalling molecule secreted by a neuron to affect another cell across a synapse. The cell receiving the signal, any main body part or target cell, may be another neuron, but could also be a gland or muscle cell. Neurotransmitters are released from synaptic vesicles into the synaptic cleft where they can interact with neurotransmitter receptors on the target cell. The neurotransmitter's effect on the target cell is determined by the receptor it binds. Neurotransmitters play a critical role in neural communication, influencing everything from involuntary movements to learning to mood. This system is both complex and highly interconnected. Neurotransmitters act in specific ways, but they can also be affected by diseases, drugs, or even the actions of other chemical messengers.
NODES OF RANVIER. Gaps between the myelin sheaf where the action potential jumps as it travels down the axon.
POST-SYNAPTIC CLEFT: Axon terminals where the neurotransmitters/signals are released from vesicles
PRE-SYNAPTIC CLEFT: Dendrites where neurotransmitters/signals are received.
RESTING POTENTIAL: A resting neuron −60 to −95 millivolts
ACTION POTENTIAL: An active neuron +30 millivolts. •
SYNAPSE: Synapse is also known as a neuronal junction, as it connects two neurons. They are the site of transmitting electric nerve impulses or chemical signals between the two neurons. It contains a small gap that separates neurons. It is the chemical junction between the terminal of one neuron and the dendrites of another neuron. Neurotransmitters are released from synaptic vesicles into the synaptic cleft where they can interact with neurotransmitter receptors on the target cell. The receptor determines the neurotransmitter's effect on the target cell it binds
VESICLES: Inside the axon terminal of a neuron 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.
NEURON STRUCTURE
A neuron varies in shape and size depending on its function and location. All neurons have three different parts – dendrites, cell body and axon.
PARTS OF NEURON
The following are the different parts of a neuron:
SENSORY NEURONS: The sensory neurons convert signals from the external environment into corresponding internal stimuli. The sensory inputs activate the sensory neurons and carry sensory information to the brain and spinal cord. They are pseudo-unipolar in structure.
MOTOR NEURONS: These are multipolar and are located in the central nervous system, extending their axons outside the central nervous system. This is the most common type of neuron and transmits information from the brain to the body's muscles.
RELAY NEURONS
They are multipolar in structure. Their axons connect only to the nearby sensory and motor neurons. They help in passing signals between two neurons.
CHEMICAL SYNAPSE
In chemical synapses, the action potential affects other neurons through a gap present between two neurons known as the synapse. The action potential is carried along the axon to a postsynaptic ending that initiates the release of chemical messengers known as neurotransmitters. These neurotransmitters excite the postsynaptic neurons that generate an action potential of their own.
ELECTRICAL SYNAPSE
When a gap junction connects two neurons, it results in an electrical synapse. These gaps include ion channels that help in the direct transmission of a positive electrical signal. These are much faster than chemical synapses.
WHAT IS A NEURON
Consciousness, mobility and sensory perception are all the result of brain activity. The brain is made up of cells called glial cells and astrocytes. Among these cells are neurons – specialised cells whose function is to communicate and process information from the environment to the brain and vice versa. It does this by getting neurone to pass information on to each with electricity and chemicals.
The human body is made up of trillions of cells. The average human brain contains 100 billion neurons and, on average, each neuron is connected to 1000 other neurons. This creates highly complex neural networks that give the brain its impressive processing capabilities. Neurons are an essential part of a massive communication system within the body.
Neurons are the oldest and longest cells in the body! You have many of the same neurons for your entire existence. Although other cells die and are replaced, many neurons are never replaced when they die. In fact, you have fewer neurons when you are old than when you are young. Neurons can be quite large - neurons that control the spine can be several feet long!
For communication between neurons to occur, an electrical impulse must trigger the release of chemicals. These chemicals, called neurotransmitters, allow other neurons in a circuit to be switched on or off. Ultimately, neurons communicating with each other are why humans can walk, talk, see, think, laugh, get angry breathe and sleep (amongst a zillion other things).
Neurons are cells that are specialised to carry neural information throughout the body. Neurons can be one of three types: sensory neurons, relay neurons or motor neurons. Neurons typically consist of a cell body, dendrites and an axon. Dendrites at one end of the neuron receive signals from other neurons or sensory receptors. Dendrites are connected to the cell body, the control centre of the neuron. From the cell body, the impulse is carried along the axon where it terminates at the axon terminal. In many nerves, including those in the brain and spinal cord, there is an insulating layer that forms around the axon – the myelin sheath. This allows nerve impulses to transmit more rapidly along the axon. If the myelin sheath is damaged, impulses slow down. The length of a neuron can vary from a few millimetres up to one metre.
HOW DOES TRANSMISSION WORK?
All things need energy to work
Cars need petrol, plants need sunlight, animals need food, and TVs need electricity. Neurons are no different; if they are going to be able to fire neurotransmitters (chemicals) at other neurons and pass on messages, some form of energy has to make them work.
LAYMAN VERSION
In essence, the neuron is run on electricity; it is the battery or power of a neuron. What triggers the electricity to fire neurotransmitters is strangely enough, other neurotransmitters, It is a never-ending cycle of neurotransmitters landing on the head of a neutron (dendrites), causing electrical spurge that travels down the neutron’s body (axon) that makes the tail of the neuron (axon terminals) release more neurotransmitters that float onto the head’s (dendrites of other neurons and effectively switch them on by causing them to send electricity (action potential) down the neutron and so on and on. In other words, brain chemistry.
SLIGHTLY MORE TECHNICAL VERSION
Neurotransmitters are received on the dendrites of a neutron these neurotransmitters will then be summed up at the top of the axon in a part called the axon Hillock if an insufficient amount of neurotransmitters are received on the Hillock they will not trigger an action potential (an bit like putting the wrong amount of AA batteries in a torch, if you put two batteries in the torch instead of 3, then the torch will not turn on..but if an adequate amount signals are built up at the axon hillock, then an action potential is triggered which sends electricity down the axon. When the electricity reaches the end of the axon, it travels to the axon terminals (also called the presynaptic terminals), where it will trigger the vesicles (holding tanks containing neurotransmitters) to release their contents into the synaptic cleft toward the dendrites (postsynaptic membranes) of other neurons in that connection/network.
SYNAPSES
so once an action potential has arrived at the terminal button at the end of the axon, it needs to be transferred to another neuron or to tissue/muscle. To achieve this, it must cross a gap between the presynaptic neuron and the post synaptic neuron. This area is known as the synapse. The physical gap between the pre and postsynaptic cell membranes is known as the synaptic gap.
At the end of the axon of the nerve cell are several sacs known as synaptic vesicles. These vesicles contain chemical messengers (the neurotransmitters - which are chemicals in the brain). As the action potential (electrical signal) reaches the synaptic vesicles, it causes them to release their contents. The released neurotransmitter (such as serotonin or dopamine) diffuses across the gap between the pre-and postsynaptic cell, where it binds perfectly to specialised receptors that recognise it (a bit like a lock and key) and that are activated by that particular neurotransmitter.
Once the neurotransmitter crosses the gap and has been taken up by the post-synaptic receptor site, i.e. the dendrites of the next neuron, the chemical message is converted back into an electrical impulse, and the transmission process begins again in this other neuron.
A single axon can have multiple branches, allowing it to make synapses on various postsynaptic cells. Similarly, a single neuron can receive thousands of synaptic inputs from many different presynaptic—sending—neurons. Until recently, it was thought that a neuron produced and released only one type of neurotransmitter. This was called "Dale's Law." However, no evidence exists that neurons can contain and release more than one kind of neurotransmitter.
SENSORY, RELAY AND MOTOR NEURONS
There are three main types of neurons: sensory, relay, and motor. Each of these neurons has a different function, depending on its location in the body and its role within the nervous system. Note: All three types of neurons consist of similar parts. However, their structure, location and function are somewhat different, which you need to be aware of.
Sensory neurons are found in receptors such as the eyes, ears, tongue and skin, and carry nerve impulses to the spinal cord and brain. When these nerve impulses reach the brain, they are translated into ‘sensations’, such as vision, hearing, taste and touch. However, not all sensory neurons reach the brain, as some neurons stop at the spinal cord, allowing for quick reflex actions.
Relay neurons are found between sensory input and motor output/response. Relay neurons are found in the brain and spinal cord and allow sensory and motor neurons to communicate.
Motor neurons are found in the central nervous system (CNS) and control muscle movements. When motor neurons are stimulated they release neurotransmitters that bind to the receptors on muscles to trigger a response, which leads to movement.
As you can see from the diagrams above, all three neurons consist of similar parts. The dendrites receive signals from other neurons or sensory receptor cells. The dendrites are typically connected to the cell body, which is often referred to as the ‘control centre’ of the neuron, as it contains the nucleus. The axon is a long, slender fibre that carries nerve impulses, as an electrical signal known as an action potential, away from the cell body towards the axon terminals, where the neuron ends. Most axons are surrounded by a myelin sheath (except for relay neurons) which insulates the axon so that the electrical impulses travel faster along the axon. The axon terminal connects the neuron to other neurons (or directly to organs), using a process called synaptic transmission.
EXCITATION AND INHIBITION
SCENARIO ONE
SCENARIO TWO
Imagine that you’re driving down a road undeterred, with no red lights or stop signs to slow you down. While that may seem like a very exciting idea, it is obviously very dangerous since our roads are not all parallel but interconnected in several different ways. For traffic to go smoothly in all directions, we have stop signs, red lights, speed bumps and police cars to ensure no accidents occur. In much the same way, our brain has a mechanism to keep the excitation in check. Information in the brain flows via excitatory neurons that have properties depending on their anatomical location. For example, a neuron in the visual cortex will respond to visual stimuli, and a neuron in the auditory cortex will respond to auditory stimuli. Since excitation cannot last forever, we must ensure it slows down or stops whenever required. This is known as inhibition. Inhibition is as important as excitation, if not more so. The neurons that perform this function are known as inhibitory neurons, and they have the special property of making sure our brain functions smoothly and is accident-free.
When activated, inhibitory neurons release the neurotransmitter GABA, which is known to hyperpolarize the postsynaptic neurons, i.e. it makes the membrane potential more negative, making it harder for the neuron to reach the threshold to fire an action potential, thereby causing ‘inhibition’. Most often, inhibitory neurons are also called GABAergic neurons for that reason. Although they constitute only 20-25% of all neurons in the cortex, they are strikingly diverse, with different morphologies, sizes, intrinsic properties, connectivity patterns, and protein expression. Based on their molecular properties, a significant effort
Excitatory and Inhibitory Neurotransmitters
Neurotransmitters can be classified as either excitatory or inhibitory in their action, having one of these two effects on the neighbouring neuron. For instance, the neurotransmitter serotonin causes inhibition in the receiving neuron, resulting in the neuron becoming more negatively charged and less likely to fire. Inhibitory neurotransmitters are like the nervous system’s “off switches” and are generally responsible for calming the mind and body, inducing sleep, and filtering out unnecessary excitatory signals. An inhibitory neurotransmitter binding with a postsynaptic receptor results in an inhibitory postsynaptic potential (IPSP), making it less likely to fire.
In contrast, neurotransmitters such as noradrenaline are excitatory; they are the nervous system’s “on switches”. These cause excitation of the postsynaptic neuron by increasing its positive charge and making it more likely to fire. It causes an electrical charge in the membrane of that cell, resulting in excitatory post-synaptic potential (EPSP), making it more likely to fire.
A nerve cell can receive both EPSPs and IPSPs at the same time. The likelihood of the cell firing is determined by adding up the excitatory and the inhibitory synaptic input. The net sum of this calculation (summation) determines whether or not the cell fires.
The nervous system controls the body’s organs and plays a role in nearly all bodily functions. Nerve cells, also known as neurons, and their neurotransmitters play important roles in this system. Neurons fire impulses. They release neurotransmitters, also known as the body’s chemical messengers. These chemicals carry signals to other cells.
WHY NEURONS CAN ONLY TRANSMIT INFORMATION IN ONE DIRECTION AT A SYNAPSE.
Answer: A Nerve electrical impulse only travels in one direction. There are several reasons nerve impulses only travel in one direction. The most important is synaptic transport.
For a "nerve impulse" to pass from cell to cell, it must cross synaptic junctions. The nerve cells are lined up head to tail all the way down a nerve track and are not connected but have tiny gaps between them and the next cell. These tiny gaps are called synapses.
When you get a nerve firing, you have probably heard that it is an electrical impulse that carries the signal. This is true, but it is not electrical like your wall outlet works. This is electrochemical energy. Neurotransmitters are molecules that fit like a lock and key into a specific receptor. The receptor is located on the next cell in the line. When the neurotransmitter hits the receptor on the next cell in line, it signals that cell to begin a firing as well.
This will continue all the way down the length of the nerve track. In a nutshell, a nerve firing results in a chain reaction down the nerve cell's axon, or stemlike section. Sodium (Na+) ions flow in, potassium (K+) ions flow out, and we get an electrochemical gradient flowing down the length of the cell. You can think of it as a line of gunpowder that someone lit, with the flame travelling down the length of it. Common electrical power is more like a hose full of water, and when you put pressure on one end, the water shoots out the other. Therefore, nerve impulses cannot travel in the opposite direction because nerve cells only have neurotransmitter storage vesicles going one way and receptors in one place.
QUESTIONS
Label a neuron: synapse, myelin-sheaf, nodes of Ranvier, axon-hillock, pre-synaptic cleft. Post-synaptic cleft, vesicles, cell-body, dendrites, axon, axon -terminals.
What is the chemical released into the synaptic gap called? Neurotransmitter
What is an action potential? Please draw an arrow above the neuron indicating.
What direction the action potential should travel down the axon.
What is the action potential of a neuron in milliseconds?
What is the axon hillock?
What role does the axon hillock have in an action potential?
Explain why neurons can only transmit action potential in one direction.
What is a:
Sensory neuron
Motor neuron
Relay neuron
Where are the three types of neurons located?
Information can only travel in one direction at a synapse. Explain why neurons can only transmit information in one direction at a synapse.
Answer: Because of the chemical nature of impulse and the axon-dendrite structure.