Written by Elijah Dave M. Cordova

Reviewed by Dr. Reuben J C. Los Baños, Ph.D.

Neurotransmitters allow brain cells to communicate with each other. They enable the transfer of information across gaps among neurons. Among the major neurotransmitters in the CNS are acetylcholine and catecholamines. Serotonin and GABA (γ-aminobutyric acid) complete the list.

Before we go into each of them, let us first classify neurotransmitters.

1. Excitatory. They cause neuron firing of an action potential to a receiving neuron.
2. Inhibitory. It is the opposite of excitatory action. It inhibits the firing of action potentials across synapses.
3. Neurohormones. Neurons synthesize and secrete them into the bloodstream. Oxytocin and vasopressin are examples.
4. Neuromodulators. They influence other neurotransmitters and affect several neurons at once.

Acetylcholine (Ach) is a neuromodulator that affects your attention and memory. It also impacts how you learn things through integration. Ach cells originate in your brainstem and midbrain. They then travel to every area of the CNS through synapses.

In the Peripheral Nervous System (PNS), Ach is an excitatory neurotransmitter. Neuromuscular junctions often use Ach to send signals between your nerves and muscles. For example, acetylcholine signals parasympathetic smooth muscle movement.

Choline acetyltransferase catalyzes the production of acetylcholine. It separates the acetyl part of acetyl coenzyme A (acetyl-CoA). It then joins this acetyl part to choline to form the product.

Catecholamines are neurohormones crucial to maintaining homeostasis in your body. Your adrenal glands on top of your kidneys produce them. Dopamine is a catecholamine. So, too, are norepinephrine (NE) (i.e., noradrenaline (NA)) and epinephrine (adrenaline) catecholamines.

Dopamine is a neuromodulator across many brain regions. One of its main functions is in the prediction and learning of rewards. Axons of your midbrain house dopamine.

L-amino acid decarboxylase (i.e., DOPA decarboxylase) synthesizes dopamine from L-Dopa. It is a precursor chemical. This same enzyme also facilitates the synthesis of histamine and serotonin, another neurotransmitter.

Dopamine β-hydroxylase synthesizes noradrenaline from dopamine. Its cells originate from your brainstem. Its main function is regulating the sympathetic nervous system. It helps regulate your body systems based on specific situations.

You can think of it as what regulates your arousal to specific situations. In times of stress, norepinephrine increases your alertness or wakefulness. It is so that you can respond in a proper manner and ensure your survival.

Epinephrine is the hormonal equal to norepinephrine. They work together to form your “fight or flight” response which you need to survive.

During stress, norepinephrine constricts your blood vessels to raise your blood pressure. Meanwhile, epinephrine forces your heart to contract with much greater strength. Its actions increase blood pressure and cardiac output.

Your body releases noradrenaline to your blood circulation at a low dose. Your body releases adrenaline in stressful moments alone.

Serotonin uses the amino acid L-tryptophan in its synthesis. Hence, it is also known as 5- hydroxytryptamine (5-HT). Most of it is in the raphe nucleus of your brain stem. Serotonin also cannot pass through your blood-brain barrier. It performs its functions in your brain alone.

Serotonin, like dopamine, is a neuromodulator. Unlike adrenaline and noradrenaline, it does not have a specific function. Instead, it affects many brain regions and body systems in consequence. Serotonin affects your mood, sleep, circadian rhythms, and body temperature, among others.

GABA is a derivative of glutamate (glutamic acid), a non-essential amino acid. It is the main inhibitory neurotransmitter of your brain. This means it inhibits the transmission of messages along neural pathways. It makes sure that your brain does not send random messages.

The enzyme glutamic acid decarboxylase (GAD) synthesizes GABA from glutamic acid. It demands cofactor pyridoxal phosphate (derived from Vitamin B6) in its synthesis. As GABA increases in your brain, it inhibits the action of GAD. With this, it manages its own synthesis.

GABA-A and GABA-B are its two receptors. They act on both receiving and transmitting targets. They do this to fine-tune the responses of your CNS. GABA cells work through lateral inhibition. This mechanism ensures the highlighting of important information in your brain.

In essence, GABA blocks noise or irrelevant message transmission. GABA also promotes sleep but inhibits brain regions that promote awakening. Abnormalities in GABA contribute to anxiety disorders which unnecessary brain activity often causes.

What triggers neurotransmitter release?

You have now come to appreciate the role of neurotransmitters in your body. Now, we ask how they travel across synapses. The opening of voltage-gated calcium channels triggers the release of neurotransmitters. These neurotransmitters travel to your synapses.

Your brain cells have dendrites that receive information and axons that conduct information. A myelin sheath can protect your axons and speed up its message transmission. Degradation of this myelin sheath leads to multiple sclerosis. It leads to a lack of muscle control.

Nerve cells also have the soma or cell body. It contains all things your nerve cell needs. The information your dendrites receive may belong from the environment or other neurons. Most neurons have one axon and many dendrites. These are multipolar neurons.

Each axon terminates on the next neuron at a synapse. These synapses are less than a millionth of an inch apart. A synapse is a specialized structure for transferring information.

The tip of each axon is the axon terminal. This part of your neuron contains synaptic vesicles that house neurotransmitters. Meanwhile, the postsynaptic membrane of the target cell has receptors for those neurotransmitters.

Your axon terminal also contains voltage-gated calcium channels. An action potential travels from your dendrites to your axons. When an action potential reaches your axon terminal, it changes its membrane potential. This action potential also opens these voltage-gated calcium channels.

Now, calcium flows into your axon terminal through diffusion. This event increases the concentration of calcium in your axon terminal. This calcium causes the fusing of vesicle and axon terminal membrane proteins.

This fusion allows your neurotransmitters to communicate outside the neuron through the synapse. These neurotransmitters diffuse into the synapse and bind to target cell receptors. They fit the receptors like a key to a lock.

Three things affect this process.

The frequency of action potentials fired down your axon opens more calcium channels. More calcium would flow in the axon terminal. More synaptic vesicles would fuse with the membrane of your axons. Hence, more neurotransmitters would travel into the synapse.

The duration of action potentials fired down your axon means longer neurotransmitter release.

Third, the blockage of target cell receptors causes failure of message transmission. It can also show the presence of a disease. Myasthenia gravis is muscle weakness due to circulating antibodies that block acetylcholine receptors.

When the train of action potentials stops firing, your calcium channels will close. Calcium stops flowing into your axon. The fusion between your vesicles and axon membrane stops. Hence, there are no more neurotransmitters that travel down your synapses.

Where can you find vesicles of neurotransmitters?

Neurotransmitter vesicles are also known as synaptic vesicles. These vessels store neurotransmitters for transport across synapses. They are in the neuron region known as the axon hillock or axon terminal. This region is the release zone.

Synaptic vesicles contribute a great deal toward the transmission of neurotransmitters across neurons. They aid in facilitating the communication between the CNS and the rest of your body.

When an action potential travels down your axon terminal, it generates a set of reactions. This results in the release of neurotransmitters kept by your synaptic vesicles. These neurotransmitters travel through synapses to communicate with target cells.

Removal of neurotransmitters from the synapse entails either of the following:

1. Reuptake.

Here, uptake pumps take your neurotransmitters from the synapse. Then, your axon terminal membrane would close off. An example of this would be serotonin uptake pumps. Selective serotonin reuptake inhibitors (SSRIs) induce serotonin buildup in your body.

• Deactivating Enzymes.

These enzymes break down your neurotransmitters. An example of this would be acetylcholinesterase (AchE). It breaks down acetylcholine in your synapses. Inhibition of its action or production builds up acetylcholine in your synapse.

How does neurotransmission affect human behavior?

Everything psychological is biological. Our biological condition affects our ideas, impulses, and moods. Our neurons communicate with neurotransmitters. This communication leads to motion and emotion. They make us move and feel.

Endorphins make you feel good. They are like opium in that they associate with the control of pain and pleasure. Your systems would flood with endorphins after exercising or eating delicious food. Falling in love can make you feel good too.

Norepinephrine controls alertness and arousal as discussed in a previous section.

Glutamate, from which we derive GABA, is also a neurotransmitter. It helps manage memory. Having too much glutamate in your CNS could cause migraines or seizures. Hence, some people sensitive to glutamate avoid monosodium glutamate (MSG). It is an ingredient you can find in ramen.

Serotonin affects your feelings of hunger, your mood, and your sleep. We link depression to low amounts of serotonin. Some antidepressants like SSRIs treat depression by increasing serotonin levels in the brain.

Acetylcholine affects learning, memory, and muscle action. Deterioration of acetylcholine-producing neurons causes Alzheimer’s. It is a progressive neurological degradation due to brain degeneration.

Dopamine affects attention, emotion, and learning. It also impacts movement and pleasure. An excess of dopamine causes schizophrenia. It is a chronic psychiatric illness where you disassociate behavior, emotion, and thought. Excess dopamine also causes other addictive or impulsive behaviors.

Acetylcholine and dopamine neurotransmitters can be excitatory or inhibitory. It depends on the type of receptors they encounter.

Like neurotransmitters, hormones act on the brain. Some hormones are even identical to certain neurotransmitters. Hormones also affect our arousal, mood, and circadian rhythms. Besides this, they can impact physical growth and aid in sexual reproduction. They can also control your metabolism.

Neurotransmission occurs at high speeds. Hormones take their time and deliver slow communications through glands. Hence, hormones linger. This explains why it takes time to calm down after having a bout of severe stress or trauma.

Adrenaline works with noradrenaline for the fight or flight response.

Your endocrine and nervous systems work together to affect your behavior.

What neurotransmitter causes happiness?

Does happiness make you healthy? Does being healthy make you happy? We may go different ways here but we can agree that both are important. Hence, we now concern ourselves with what neurotransmitter causes happiness.

Seven neurotransmitters provide a general feeling of well-being. Adrenaline, dopamine and endocannabinoids are among them. So, too, do endorphin, GABA, oxytocin, and serotonin belong.

Adrenaline elicits an exhilarating feeling. It also creates a surge in energy. It makes you feel alive.

Dopamine drives behaviors driven by rewards and seeking pleasure. Several addictive drugs act on the dopamine system. These drugs block dopamine reuptake, leaving it in your synapses longer.

Endocannabinoids that include anandamide have similar effects to marijuana. They prevent anxiety and burnout. They contribute to the runner’s high you would get after sustained running.

Endorphins resemble opiates. They are painkillers in essence.

GABA creates a sense of calmness by inhibiting the firing of neurons. Benzodiazepines are anti-anxiety medications that work by increasing GABA.

Oxytocin is a neurohormone linked to feelings of intimacy and affection. Couples distant from each other for a long time have decreased oxytocin levels.

Serotonin affects your appetite, mood, social interaction, and performance. High serotonin levels mean increased self-esteem and feelings of worthiness.

Where is GABA neurotransmitter produced?

GABA is the brain’s main inhibitory neurotransmitter. It is also a major inhibitory neurotransmitter in the spinal cord. Glutamate decarboxylase uses Vitamin B6 (pyridoxine) to synthesize GABA from glutamate. GABA production happens in the brain and β-cells of the pancreas.

Several diseases exhibit GABA deficiencies:

1. Dystonia and spasticity.

Dystonia is involuntary muscle contraction. It causes repetitive and twisting motions. Spasticity refers to stiff muscles. A deficiency in GABA signaling can cause these two diseases.

• Hepatic encephalopathy.

It refers to impaired brain function due to advanced liver disease. Elevated ammonia levels can bind to a GABA complex and cause this disease.

• Huntington’s disease.

It is an inherited disease the causes the progressive degeneration of brain neurons. A lack of GABA exhibits this disease.

• Pyridoxine deficiency.

It is when your body does not have Vitamin B6 to produce GABA. Frequent seizures during infancy are common.

REFERENCES

Bergland, C. (2012). The Neurochemicals of Happiness. Psychology Today. https://www.psychologytoday.com/us/blog/the-athletes-way/201211/the-neurochemicals- happiness

Hank. (2014). The Chemical Mind: Crash Course Psychology #3 [YouTube Video]. In YouTube. https://www.youtube.com/watch?v=W4N-7AlzK7s

Jensen, M. B. (2014). Neurotransmitter release | Nervous system physiology | NCLEX-RN | Khan Academy [YouTube Video]. In YouTube. https://www.youtube.com/watch?v=Ac- Npt3vgCE

Pastore, R. (2020, May 7). What are the Main Neurotransmitters? PowerOnPowerOff. https://poweronpoweroff.com/blogs/guide/what-are-the-main-neurotransmitters

We hope and pray that everyone is okay in this time of great challenge. Just as the sun will continue to rise every day, humanity will always have the strength to continue even in times of great difficulty. Storms will come and go, but our faith will remain. Discovering God has always been a struggle, especially as a Ph.D. candidate trained to be skeptical about everything. Still, I have come to the conclusion that life is meaningless without God, and everything I must do in this world is to continue to know Him for it is the most worthwhile thing I can do in this world.

Written by Jean Mari A. Rojas

Edited and Reviewed by Dr. Reuben J C. Los Baños, Ph.D.

The term muscles came from the Latin word mus, which means “little mouse.” The naming of the term is because of how flexing muscles look like scurrying mice beneath the skin.

There are three types of muscles:

1. Skeletal muscles.
2. Smooth muscles.
3. Cardiac muscles.

Some muscles line the heart (cardiac muscles) and other hollow organs (smooth muscles). Both of these muscles have involuntary movement. 

Muscles make up most of our body mass, with 600 forces making up the entire muscular system. The muscular system combines with other body systems to achieve many functions.

The primary functions of the muscular system are contractibility and movement.

The muscular system’s primary function is contractibility. With this unique function, muscles are now responsible for almost all body movement. An exception to this is cilia, flagellum on sperm cells, and activity of some white cells.  

A combination of skeletal muscles, joints, and bones produces visible motions. These actions include walking and running.

• It helps in creating a quick response to our environment.

• Skeletal muscles also generate more subtle movements. These movements include facial expressions, eye movements, eating, and breathing.

Smooth and cardiac muscles work together to ease movement in the blood vessels and heart.   

• They work together to maintain blood pressure and circulate blood to the parts of the body.

Other functions of the muscular system include:

1. Maintain posture and body position. It helps keep the body upright, erect, and in the correct position when standing or sitting.

2. Skeletal muscles also help in stabilizing joints. Muscle tendons stretch over joints and contribute to their stability.

3. Muscle activity generates heat as a byproduct. This byproduct is essential in maintaining average body temperature. Almost 85% of the heat generated is from muscle contraction. When it is cold, our muscular system will increase movement to increase heat production. This movement is shivering. Blood vessels, lined with smooth muscles, also contract to maintain body heat.

Other functions: Organ protection, vision, urination, digestion, and respiration.

How are muscles made in the body?

Myogenesis is the production of muscle tissue from stem cells. It gets produced in the mesoderm during embryonic development. Myoblasts fuse into multinucleated fibers termed myotubes to create muscle fibers. Suppose adequate fibroblast growth factor (FGF) is available during early embryonic development. The myoblasts multiply.

Muscle formation comes with three stages:

1. Myoblasts fuse into multinucleated fibers termed myotubes to create muscle fibers.

In early embryonic development, these myoblasts proliferate. But only if enough fibroblast growth factor (FGF) is present. When the FGF runs out, the myoblasts stop division.

It also secretes fibronectin onto its extracellular matrix.

2. Myoblasts align into the myotubes.

3. Cell fusion itself.

Calcium ions are critical for development. Myocyte Enhance Factors (MEFs) that promote myogenesis. Serum Response Factor (SRF) plays a central role during myogenesis. It requires the SRF to express striated alpha-actin genes. The expression gets regulated by the androgen receptor.

It means its steroids can control myogenesis.

Muscular hypertrophy refers to the expansion and development of muscle cells. It refers to a muscle size expansion that occurs as a result of training. Toning or improving muscular definition by lifting weights during exercises increases hypertrophy.

There are three Mechanisms for developing muscular hypertrophy:

1. MECHANICAL TENSION

It uses heavy load and performs exercises through a full range of motion. It considers the time the muscle spends under tension provided by the external load (barbell, dumbbell, etc.). The more time spent with the haul, the more mechanical tension gets produced.

But, tension alone won’t result in maximal muscle growth. It has to go into a full range of motion.

2. MUSCULAR DAMAGE

DOMs (Delayed Onset of Muscle Soreness) result from micro-tearing of the muscle due to damage. It gets sustained during resistance training, coming from eccentric and concentric contractions.

The initiation of muscular injury stimulates mTOR pathways, which then trigger protein synthesis. It is here that the rebuilding of the damaged muscle begins.

3. METABOLIC STRESS

‘the burn’ or ‘the pump’ repetitions. It is getting into higher repetitions and taking short breaks intervals. It creates a continuous contracting and relaxing of the muscles. It results in a blood pooling effect that makes muscular (cell) swelling. It causes a restriction in blood supply to the muscle and a shortage of oxygenated blood. It results in less oxygen to feed the body during contractions.

It causes a massive build-up of metabolites such as lactate and hydrogen ions. The anabolic impact of the metabolic stress put on the muscles leads to molecular signaling. It also increases the body’s hormonal response.

Why is protein essential for muscle?

The human body consists of about 5 to 6 kilograms of muscle protein. Protein is the building block of our muscular system.

Your body requires protein to stay healthy. Its general function is to:

• Proteins are components of blood and it carries energy and oxygen throughout your body
• Help create antibodies that fight off infections and illnesses
• Help keep cells healthy and make new ones.

Strength training activity stimulates the process of muscle protein synthesis (MPS). But, it gets enabled when you eat protein. Eating the right amounts of protein will help maintain muscle mass and muscle growth.

The amino acid leucine is abundant in “fast-digesting” proteins. It aids in the stimulation of MPS. Slow digesting proteins, such as those found in eggs and milk may help in slowing down the MPS process.

Eating reasonable amounts of protein help increase muscular strength and mass. So in trying to gain muscles and be active, make sure always to have enough protein. Also, keeping the protein intake high will prevent muscle loss during the weight loss attempts.

Best sources of protein:

High-quality sources of protein include:

•  Fish, Poultry, Beef, or pork
• Tofu
• Eggs
• Dairy products

Plant-based sources include:

• Nuts
• Seeds
• Legumes, like beans, peas, or lentils
• Grains, like wheat, rice, or corn

What is the largest muscle of the body?

The gluteus maximus is the largest and heaviest muscle in the human body.  It is the gluteal muscles’ most superficial muscle. It makes it the enormous muscle at the hip, representing 16% of the total cross-sectional area. 

Gluteal muscles:

• Gluteus Maximus
• Gluteus Medius
• Gluteus Minimus

The origins of the gluteus maximus are:

• Posterior gluteal line of the ilium;
• The posterior surface of the lower part of the sacrum;
• Side of the coccyx;
• Aponeurosis of erector spinae;
• Sacrotuberous ligament;
• Gluteal aponeurosis;
• Attaches to thoracolumbar and its associated raphe

The insertions of the gluteus maximus are:

• The enormous proximal part inserts into the Iliotibial tract. It forms the majority of the fibers.
• The other fibers insert into the linea aspera of the femur.

• The aponeurosis joins to the femur’s gluteal tuberosity.

Because of its large size, Gluteus Maximus can exert a lot of force. As one of the muscles stretching the hip joint, it also helps maintain an erect posture. The Gluteus Maximus’ primary function is to extend and rotate the hip joint to the side. Upper fibers can abduct the hip while the lower fibers can adduct it.    

The Gluteus maximus and the hamstrings work in conjunction to produce different movements:

• Extending the trunk from a flexed position by pulling the pelvis backward;
• Bending forward;
• Superior fibers of the gluteus maximus extend the knee

Gluteus maximus has stability roles:

• Maintaining upright posture;
• Supporting of the lateral knee;
• Abducting of the medial longitudinal arch of the foot

Other functions include:

• self bracing mechanisms;
• supporting body weight while sitting;
• The quadriceps femoris can get weak or paralyzed. The gluteus maximus can get trained to produce functional knee extension.

A bruise to the gluteal region is the gluteal contusion. Some get anticoagulated or on blood thinners. Large amounts of bleeding can occur within and around the muscle. It can cause severe pain and swelling. Trauma causes the most gluteal injuries, either by fall or a direct hit to the area.

While a gluteal muscle strain occurs when a muscle or tendon gets stretched or in part torn. Overuse injuries are the leading cause of gluteal muscular strain. It can result in inflammation and damage to the muscular system.

The most common injuries experienced by athletes are gluteal tendinopathies. It stems from overtraining in squats and weightlifting. Inflammation of the hip and gluteus is a common running injury.

What is the smallest muscle in the body?

The stapedius muscle is the smallest in the human body, approximately 6 mm in length. Its location is in the middle ear’s tympanic cavity. It controls the vibration of the body’s smallest bone or known as the stirrup bone.

The origin of the stapedius: Pyramidal eminence of the tympanic cavity.

The insertion of the stapedius: Neck of stapes.

Although it is the tiniest skeletal muscle, the stapedius has a vital role in sound transmission and hearing. It’s the acoustic middle ear reflex’s effector component.

The sound threshold of a healthy person with normal hearing is around 85 dB. Vocalization-induced stapedius reflex reduces sound intensities. It reaches the inner ear by about 20 decibels.

The primary function of the stapedius is to protect the inner ear from loud noises. The facial nerve’s stapedial branch innervates the stapedius muscle. These autonomic fibers allow the muscle to take part in the auditory middle ear reflex. It protects the auditory system. 

Hyperacusis is a condition that causes normal sounds to get perceived as loud noises. This condition results from the paralysis of the stapedius. It allows wider oscillation of the stapes. It heightens the reaction of the auditory ossicles to sound vibrations, causing hyperacusis. 

Paralysis of the stapedius. It results when the nerve to the stapedius, a branch of the facial nerve, or its entirety, gets damaged. Example cases are Bell’s palsy, a unilateral paralysis of the facial nerve. Where the stapedius gets paralyzed, and hyperacusis may result.

Do muscles need oxygen?

Much like every other cell and organ of the body, the muscular system needs oxygen to function.

Oxygen gets carried via red blood cells, where it binds to a protein called hemoglobin. The heart pumps the red blood cells to the parts of the body. Afterward, the release of oxygen into the cells occurs. Oxygen then gets used for breaking down molecules.

Adenosine triphosphate (ATP) is fuel for the muscles. It is a molecule that is the primary energy source to keep our body functioning. Carbon Dioxide (CO2) and water (H2O) gets produced as a result.

Whether exercising or not, oxygen gets used to breaking down glucose. And glucose creates ATP. This process of breaking down glucose is aerobic metabolism, which requires oxygen.

Muscles need the energy to produce contractions. It gets derived from the ATP that is present.

When you exercise, your muscles consume more oxygen:

• Your heart rate and breathing rate rise, drawing more oxygen into the circulation. It results in the increased production of ATP;

• Increased heart rate and breathing to remove the amount of carbon dioxide generated 

Energy can also get produced by anaerobic metabolism, a process that does not need oxygen. When your body lacks oxygen or your other systems can’t get enough oxygen to your muscles, your body will go into anaerobic metabolism. The muscles will convert the glucose you have to into lactic acid. During an intense workout, this is when your performance begins to deteriorate. Deterioration and fatigue will make you feel weary.

Researchers from Sweden’s Karolinska Institute discovered about oxygen-sensitive enzyme FIH (Factor Inhibiting HIF). FIH’s role is crucial in transitioning from aerobic to anaerobic metabolism. According to the investigators, FIH will ensure that the muscles maintain aerobic metabolism for as long as possible. It will continue to be efficient in using oxygen before transitioning to anaerobic metabolism.

After exercising, your body will be in oxygen debt. It is necessary to refill debts and replenish the oxygen in your bloodstream. Cool-down exercises are essential for replenishing oxygen levels. Afterward, consume a protein-filled snack to replace your body’s glycogen storage.

Your body’s ATP levels get restored by combining oxygen and glycogen. It also aids the liver, kidneys, and muscles in the breakdown of lactic acid.

There are three types of muscles that you can find in the human body. They are the skeletal muscles, cardiac muscles, and smooth muscles. Skeletal muscles are voluntary muscles found in the bones. Smooth muscles, also called non-striated muscles, involve slow and involuntary movement. While cardiac muscles are involuntary striated muscles found in the heart.

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Written by Shanaiah Regine M. Tonelete

Reviewed by Dr. Reuben J C. Los Baños, Ph.D.

Cardiac rhythm is the heart’s rhythm or the electrical activity of the heart. People assume that this only pertains to the heart’s contraction and relaxation. Yet, every heartbeat you have is far more complex than that.

If you can recall, the heart has four chambers. The upper chambers are the atria (sing. atrium), while the lower ones are the ventricles. These chambers, together with specific bundles of cells, generate your cardiac rhythm.

Whenever your heart beats, a bundle of specialized cells works to regulate it. The sinoatrial (SA) node (sinus node) sends electrical impulses to begin your heartbeat. The SA node is your heart’s natural pacemaker; thus, it sets your heart’s rate and rhythm.

The sinus node, found at the right atrium’s epicardium, sends impulses to your atria. These impulses spread to the walls of each atrium which prompts their contraction. When the atria contract, it allows blood to flow towards your ventricles.

Before reaching the ventricles, the blood needs to pass a specific cluster of cells. The atrioventricular (AV) node acts as a gateway for your blood. It slows down the signal sent by the SA node to allow your atria to contract before the ventricles.

Meanwhile, the His-Purkinje Network spreads the impulse to the lower chambers’ walls. It causes your ventricles to contract and pump blood to the lungs and body.

These nodes and fibers allow your heart to have a controlled beating. When the ventricles release blood, the SA node sends another electrical impulse. It will trigger another heartbeat, and the cycle continues.

What is an abnormal cardiac rhythm called?

When your heart rhythm is too slow or fast, it can suggest many things. This abnormality in your cardiac rhythm refers to arrhythmia (dysrhythmia). Arrhythmia originated from the Greek words a– and rhythmos which means loss of rhythm.

To know whether you have an irregular heartbeat, you need to measure your pulse. The regular heart rate ranges from 50 to 100 beats per minute (bpm). You can count it by touching your wrist and neck or using an electrocardiogram (EKG).

The usual classifications for abnormal cardiac rhythms are bradycardia and tachycardia. A rate lower than 60 bpm is bradycardia. A rate greater than 100 bpm is tachycardia.

Another way to know if you have arrhythmia is when you experience palpitations. You can also suffer from shortness of breath and fatigue. Although these symptoms are subjective and some people may not have them.

There are also various reasons why you can have this condition. It can be due to hypertension, valve disorders, and other medical conditions. Your excessive consumption of alcohol/coffee and exercising can also cause it.

Cardiologists often use some tests to diagnose arrhythmia. The tests to confirm the presence of abnormal heartbeats include:

• Cardiac Catheterization
• Echocardiogram
• Electrocardiogram
• Electrophysiology Study (EPS)
• Stress Test
• Tilt Table Test

What are the 5 lethal cardiac rhythms?

The word lethal is often associated with death. It means that something is destructive or harmful for you. Thus, lethal cardiac rhythms can infer that these rhythms might cause your death. Here are five arrhythmias considered lethal.

Premature Ventricular Contraction (PVC)

PVC is an ectopic (abnormal) beat in your ventricles but is not an actual rhythm. It causes the ventricles to depolarize before the next sinus beat. Thus, it earned the label of premature.

Since PVCs arise in ventricles, there are changes in the ventricular depolarization sequence. The extra beats due to PVCs disrupt your heart’s rhythm. Although PVCs are often benign, some are life- threatening due to other heart problems.

Ventricular Tachycardia (VT)

Three or more consecutive PVCs or heartbeats can suggest ventricular tachycardia. VT is an abnormal heart rate that starts in the lower chambers of your heart. Its usual rate is 100-250 bpm.

Some of the possible causes of VT include cardiomyopathy and coronary artery disease. VT can be life-threatening if it continues for more than a few seconds.

Ventricular Fibrillation (VF)

When there is disorganization in the ventricles’ electrical activity, they will quiver. This condition is what you call ventricular fibrillation. Scientists describe the ventricular myocardium as a “can of worms” during VF.

VF is dangerous since there is no cardiac output when your ventricles quiver. Thus, there is no palpable pulse, no blood pressure, and you will become cyanotic. Within 3-5 minutes, this rhythm can become lethal.

Some of the possible causes of VF are cardiomyopathy and untreated ventricular tachycardia. Acid- base imbalance and electrolyte imbalances can also result in VF.

Asystole

Asystole is the absence of movement or electrical activity in your heart. You can see it as a flat line on the EKG screen. When you have asystole, it means that you have no heart rate and rhythm.

Although VF and asystole seem similar, you can differentiate them through telemetry reading. Asystole becomes lethal when it persists for more than fifteen minutes. It can cause death since there is not enough oxygen to supply your body, especially the brain.

Other Arrhythmias

Pulseless Electrical Activity (PEA)

When your heart has an electrical activity but no pulse, you have a condition called PEA. Since you have no cardiac output, you will be pulseless and unconscious. Often, hypovolemia causes PEA.

Various rhythms belong to this category. It includes electromechanical dissociation (EMD), bradyasystole rhythm, and pseudo-EMD.

Agonal Rhythm

It is a condition characterized by having an irregular rhythm with a rate of ≤20 bpm. It is the rhythm seen during the last stages of unsuccessful resuscitation. The agonal rhythm later ends at asystole.

How long can you live with irregular heart beat?

Having arrhythmia is a challenge. Being able to live a comfortable life despite having it depends on the type of arrhythmia you have. Your life expectancy also depends on it.

If you have a harmless or benign arrhythmia, you can live a healthy and longer life. There is no definite life span for those with benign arrhythmias. Research only reveals that people with harmless arrhythmias do not need treatment. But treatment is not necessary only if there are no other complications involved.

Meanwhile, those considered life-threatening can give you a few minutes if not treated. Lethal arrhythmias such as ventricular fibrillation and asystole can grant you 3-15 minutes. If not immediately treated within that time, it can cause your death.

What is the best medication for irregular heartbeat?

Antiarrhythmic drugs are the medications used by people with irregular heartbeats. These drugs treat the abnormality in your heart rhythm or slow its rate.

It is necessary to consult your doctor first before taking any medications. You can choose between two approaches to taking the drugs. These are the “pill in the pocket” method and regular intake.

The “pill in the pocket” method is helpful when your episodes appear less frequent. You can put the pill in your wallet and take it when you experience an arrhythmia episode. Meanwhile, the second method is taking the drugs every day.

Some medications prescribed by doctors are beta-blockers and calcium channel blockers.

Beta-Blockers

These drugs decrease your cardiac output. They help slow down your heart’s rhythm, but they may also stop your arrhythmia. They work by blocking the effects of adrenaline which lowers your blood pressure.

Some of the examples of beta-blockers are sotalol and nadolol. Bisoprolol and metoprolol (beta- blockers) can also treat atrial fibrillation (AF).

Calcium Channel Blockers

These refer to the drugs that interrupt calcium movement in the heart. Thus, they are calcium antagonists. If there is less calcium, then there is a reduction in the heart’s electrical activity.

Verapamil and diltiazem are examples of calcium antagonists. Those who have AF can also take digoxin.

Can irregular heartbeat go back to normal?

Irregular heartbeat is often reversible. It goes back to normal on its own, but there are also things you can do to regulate your heart rate.

When you exercise, it is normal to have an increased rate after. Overexercising can result in the irregular beating of your heart muscle. Too much caffeine, alcohol, or nicotine can also trigger it.

To avoid this, you can do the following:

• Avoid too much consumption of caffeine
• Avoid alcohol
• Avoid stimulant drugs
• Do not smoke
• Get enough sleep
• Relax and manage your stress

Meanwhile, some arrhythmias are possible to regulate but hard to restore. Taking medications can repair them for a while, but without them, they will return. These are the arrhythmias associated with other heart problems. Scientists claim that irregular heartbeats are incurable. Unless treatment for other complications is available, then they will remain.

Some of the causes of this type of arrhythmia are high blood pressure and damaged heart tissue and. Congenital heart problems and inflammatory disorders can also cause it.

Can stress cause an irregular heart beat?

The heart and brain have a complex interaction with each other. When you experience physical or emotional stress, your brain sends a signal to the rest of your body. The heart receives this signal, then increases its heartbeat and elevates blood pressure.

Thus, stress-induced cardiac arrhythmias are possible. Negative emotions prompt the release of catecholamines or stress hormones. These hormones are responsible for your fight-or-flight response.

The heart’s cardiac output increases when the adrenal glands release catecholamines. This hormone increases the contractility and excitability of the cardiac muscle. It also increases the AV nodal conduction velocity and the SA nodal discharge rate of the heart. Thus, increasing the cardiac output.

To avoid having stress-induced arrhythmias, you can try doing:

• Eating nutritious food

• Have a positive attitude

• Meditation

• Regular exercise

If irregular heartbeats continue to persist, you can try contacting your doctor. There might be other reasons why you have the condition. It is necessary to seek professional advice before taking any medications.

REFERENCES

American Heart Association. (2016, September 30). Medications for Arrhythmia. American Heart Association. Retrieved October 27, 2021, from https://www.heart.org/en/health- topics/arrhythmia/prevention–treatment-of-arrhythmia/medications-for-arrhythmia

Arrhythmia. (2018, June 12). Cleveland Clinic. Retrieved October 27, 2021, from https://my.clevelandclinic.org/health/diseases/16749-arrhythmia

Beckerman, J. (2020, August 24). What to Do If Your Heart Races, Slows Down, or Skips a Beat.

WebMD. https://www.webmd.com/heart-disease/atrial-fibrillation/what-to-do-heart-races

British Heart Foundation. (n.d.). Drug cabinet: Anti-arrhythmics. British Heart Foundation. Retrieved October 27, 2021, from https://www.bhf.org.uk/informationsupport/heart-matters- magazine/medical/drug-cabinet/anti-arrhythmics

Heart Beat. (2019, May 1). Cleveland Clinic. Retrieved October 27, 2021, from https://my.clevelandclinic.org/health/articles/17064-heart-beat

Living With an Arrhythmia. (n.d.). Aging Care. Retrieved October 27, 2021, from https://www.agingcare.com/articles/how-to-manage-arrhythmia-114028.htm

Mayo Clinic. (2021, March 18). Atrial fibrillation and managing stress. Mayo Clinic. https://www.mayoclinic.org/diseases-conditions/atrial-fibrillation/in-depth/atrial- fibrillation-managing-stress/art-20118647

RN.com. (2003). Lethal Arrhythmias: Advanced Rhythm Interpretation. AMN Healthcare, Inc. https://lms.rn.com/getpdf.php/633.pdf

Secretion and physiological effects of catecholamines. (2016, September 28). WikiLectures. Retrieved October 27, 2021, from https://www.wikilectures.eu/w/Secretion_and_physiological_effects_of_catecholamines

University of Birmingham. (2018, May 10). Patients who have had an irregular heart beat can’t ever be considered ‘cured’. Science Daily. https://www.sciencedaily.com/releases/2018/05/180510145948.htm

Written by Biana Isabel Agner

Reviewed by Dr. Reuben J C. Los Baños, Ph.D.

The central framework of your body is the skeletal system. The musculoskeletal system is another name for it. Bones and connective tissue make up the structure.

The skeletal system serves a variety of purposes. It not only gives us our human shape and features but it allows us the following:

• Movement – The skeleton helps you stand and move by supporting body weight. The collaboration of joints, connective tissues, and muscles make your body parts mobile.

• Produces blood cells – The bone marrow is a type of marrow that produces blood cells. The bone marrow makes red and white blood cells.

• Protects and supports organs – The skull protects the brain; the ribs protect your heart and lungs. The backbone protects the spine.

• Mineral storage – Bones store minerals such as calcium and vitamin D for your body.

Some of the skeletal system’s functions are more visible than others. You can feel how your bones can support you, help movement, and protect your organs when you move.

The bones and cartilages of the skeletal system serve as a frame for support. Bones help you move by acting as attachment points for your muscles. It also covers or surround internal organs to protect.

Bone tissue also serves many important metabolic functions. It serves as a reservoir for a variety of minerals important to body function. Examples of these minerals are calcium and phosphorus. Releasing these minerals back into the bloodstream maintain the right level to support.

What type of skeleton do humans have?

In an adult, the human skeleton is an endoskeleton made up of 206 bones. The endoskeleton serves five primary purposes. It supports the body, stores minerals and lipids, and produce blood cells. It also protects internal organs and allow movement.

Endoskeletons come in variety of shapes and sizes. It also comes in complexity, shape, and function depending on the animal’s needs. The endoskeleton of most vertebrates has mineralized tissue. These tissues are in the form of bone and cartilage.

The axial skeleton includes the skull, vertebral column, and rib cage. The appendicular skeleton consists of the shoulders, limb bones, pectoral, and pelvic girdle. The axial and appendicular are the major divisions of the skeleton.

The skull, vertebral column, and thoracic cage make up the axial skeleton. The axial skeleton is the central axis of the human body. It supports and protects the brain, spinal cord, and organs in the ventral body cavity.

It serves as a surface for the attachment of muscles that move the head, neck, and trunk. It also moves those that perform respiratory movements. Adults have 80 bones in their axial skeleton.

The skull’s bones support and protect the face’s structures as well as the brain. The skull consists of 22 bones with two groups: cranial and facial bones. The cranial bones are eight bones that make up the cranial activity. It houses the brain and serves as a resting place for the head and neck muscles.

There are eight cranial bones. These are the frontal bone, two parietal bones, two temporal bones, and occipital bone. The sphenoid bone and ethmoid bone are also cranial bones.

The face has fourteen facial bones. It provides cavities for the sense organs – eyes, mouth, and nose. It also protects the digestive and respiratory tract entrances. The facial bones serve as attachments points for muscles. The 14 facial bones contain the following:

• nasal bones,
• maxillary bones
• zygomatic bones
• palatine, vomer
• lacrimal bones
• inferior nasal conchae
• mandible

What’s the weakest bone in your body?

The clavicle or collarbone is the softest and weakest bone in the body. It is a thin bone that runs in a horizontal manner between your breastbone and shoulder blade. Because of its location, it is easy for the clavicle to break.

This bone is an important part of the skeletal system. It is important because it connects the axial skeleton to the pectoral girdle. It allows everyday functional movement.

 The clavicle can function as a shoulder brace. It allows weight to transfer from the upper extremities to the axial skeleton. Injuries in the clavicle make it difficult to carry out daily tasks.

Between the ribcage and the shoulder blade is the clavicle. It is the bone that joins the arm to the rest of the body. The clavicle is above several vital nerves and blood vessels. It is a long bone that palpates along its entire length. It is visible beneath the skin in thin people.

The clavicle serves three purposes:

• Connects the upper limb to the trunk as a part of the shoulder girdle.
  
  
• Protects underlying neurovascular structures that supplies the upper limb.
  
  
• It conveys force from the upper limb to the axial skeleton.

Do females have more ribs than males?

Females do not have more ribs than males. Regardless of gender, most people have the same number of ribs. The belief that men have fewer ribs than women is common, but it is incorrect. This belief may stem from the biblical story of Adam and Eve.

The ribs protect organs and assists in breathing. The bony framework of the thoracic cavity contains the ribs. The ribs are the main structural component of the thoracic cage. It protects the thoracic organs.

The majority of people are born with 24 ribs, 12 on each side of their bodies. The costovertebral joint connects each rib to two thoracic vertebrae in the back. The first rib articulates with the first thoracic vertebra.

The three classified groups of the ribs are:

• True ribs – The true ribs are ribs 1-7. This have coastal cartilages that are direct and articulate with the sternum. The sternocostal joints connect them to the sternum.

 The first rib is an exception to this rule because it is a synarthrosis. The costoclavicular joint allows the rib to articulate with the clavicle in a unique way.

• False ribs – The false ribs (8,9,10) articulate with the sternum through the costochondral joint. It connects their costal cartilages to the seventh costal cartilage.
• Floating ribs – The sternum does not articulate with the floating ribs (11,12).

The anatomical components of the ribs are as follows:

• Two articular facets on the head
• Tubercle
• Neck
• Shaft
• Costal groove

Most of the ribs are standard ribs. Standard ribs have all these characteristics. While atypical ribs are those that lack these characteristics:

• The first rib is wide and short. It has two costal grooves and one articular facet.

• The second rib is thin and long. It has a tuberosity on its superior surface to attach the serratus anterior muscle.

• The tenth rib only has one articular facet.
  
  
• The eleventh and twelfth rib has only one articular facet with no neck.

What bone takes the longest to heal?

It takes a long time for the femur to heal after it breaks. The femur, also known as the thigh bone, is the largest and most powerful bone in your body. Because the femur is one of the main bones used to walk, breaking it can make everyday tasks much more difficult.

The femur is a large, strong, and difficult bone to break. A severe accident is the most common cause of a broken femur. Vehicle accidents are the most common reason for a broken femur.

The adult’s bones are weaker, and a fall can result in a femur fraction. It depends on how close the break is to the hip. The break is a hip fracture rather than a femur fracture.

The femur is the body’s longest bone and the only bone in the thigh. It has three parts: proximal, shaft, and distal. It serves as the origin and attachment point of muscles and ligaments.

• Proximal – The hip joint contains the proximal aspect of the femur with the acetabulum of the pelvis. The greater and lesser trochanters are two bony processes that make up the head and neck.
• Shaft – The femur shaft descends in a medical direction. This increases stability by bringing knees closer to the body’s center of gravity. The shaft’s cross section is circular in the middle but flattened at the proximal and distal ends.
• Distal – The medial and lateral condyles, articulate with the tibia and patella to form the knee joint. It is at the distal end of the femur.
  
  

A femur fracture is an injury to the thigh bone that causes it to crack, break, or crush. Smaller, less complicated femur fractures usually do not need surgery. Others need immediate surgery if the bone is completely broken, crushed, or displaced.

It takes a lot of force to break the femur because it is so strong.

A high-energy collision, such as a car or motorcycle accident, is usually the source of the problem. In people who have weak bones, even a low-force event like a fall can result in a broken femur.

It can take anywhere from 12 weeks to 12 months to recover. But, with the help of a physical therapist, many patients can begin walking much earlier. Recovery times for surgery can differ depending on a variety of factors.

Are women’s bones weaker than men?

The size and sturdiness of skeleton bones differs between men and women. Differences in bone structures are present as early as childhood. Puberty is the period of physical maturation. It is the transformation of a child’s body into an adult body that is capable of reproduction.

Bones of males are larger and stronger, both in size and density. Male bone mass peaks at around 50% higher than female bone mass, and women lose bone faster as they age. Black people’s bones are stronger than white people. In fact, black women’s peak bone mass is comparable to white men.

A factor to consider when it comes to bone growth in boys is testosterone. Testosterone is the have sex hormone that aids on bone growth. While estrogen is the main sex hormone in females that inhibits bone growth as well.           

The fact that boys develop larger bones than girls is because of the differences of the hormones. And because of this difference, adult women have higher risk of fractures due to the hormones. This makes the women’s bones weaker than men.

When women reach menopause, their level of estrogen drops, which can lead to bone loss. When women approach menopause, their risk of developing osteoporosis rises. For women of various ages and backgrounds, osteoporosis and bone health issues differ.

In comparison to men, women have wider pelvises and torsos.Researchers can even tell if a skeleton is male or female by measuring the hip bones. Women have stronger pelvises because of their unique ability to carry a child and give birth.

The shape and size of the pelvis is a factor in childbirth for support. It is wider and longer and is together with ligaments that loosen during pregnancy. Women’s torsos are also wider than men’s for the body to accommodate organs in pregnancy.

How many floating ribs do humans have?

People have two floating ribs (ribs 11 and 12) at the bottom of the ribcage. People often have extra or missing ribs and vertebrae, which is surprising. The sternum is not attached to the last two pairs of ribs at the bottom of the rib cage.

These are “floating ribs” because their only attachment is at the back of the rib cage. These ribs anchor to the spine’s vertebrae, which makes them prone to injury due to lack of attachment. This injury is a painful condition known as “slipping rib syndrome”.

In the chest, the rib cage is a bony structure (thoracic cavity). There are 12 pairs of ribs in total. The sternum, a bony process at the front of the rib cage that serves as an anchor point, is where each pair has a number. The cartilage at the end of each rib (costal cartilage) attaches to the sternum.

The purpose of the human rib cage (thoracic cage) is to protect the heart and lungs. The ribs, which are flat bones, are part of the axial skeleton. The primary function of flat bones is to protect the structures beneath them. The pelvis and skull are two other flat bones in the human body.

References

Anatomy and Physiology. (n.d.). https://open.oregonstate.education/aandp/chapter/6-1-the-

functions-of-the-skeletal-system/

Biga, L. M., Dawson, S., Harwell, A., Hopkins, R., Kaufmann, J., LeMaster, M., Matern, P.,

Morrison-Graham, K., Quick, D., & Runyeon, J. (n.d.). Anatomy & Physiology.

Endoskeleton. (2017, April 28). biology dictionary. Retrieved October 27, 2021, from

How many ribs does the human body have? Differences between men and women. (n.d.).

Medical News Today. Retrieved October 29, 2021, from https://www.medicalnewstoday.com/articles/enthesitis#causes

Morrison, W. (2018, July 31). Broken Femur: healthline. Retrieved October 30, 2021, from

https://www.healthline.com/health/broken-femur#diagnosis

Ribs. (n.d.). Physiopedia. Retrieved October 30, 2021, from https://www.physio-pedia.com/Ribs 

Skeletal system. (2019, November 11). Cleveland Clinic. Retrieved October 25, 2021, from

https://my.clevelandclinic.org/health/body/21048-skeletal-system

What is the strongest and weakest bone in the human body? (n.d.). Vedantu online learning.

Retrieved October 27, 2021, from https://www.vedantu.com/question-answer/which-is-the-strongest-and-weakest-bone-in-the-class-11-biology-cbse-60d4937b80258b738178e5b0