Nervous System Anatomy & Physiology – MBLEx Review

The nervous system is one of the major systems of the body. With over 100 billion nerve cells creating over 100 trillion synapses, the human nervous system is one of the most complex structures in the universe. There is still a lot about the brain and nervous system that remains unknown. The nervous system interacts with every other system of the body. It has the primary function to receive, process and transmit information within the body in order to coordinate all activities of the body and maintain homeostasis.

Massage therapists and students preparing for the massage exam (MBLEx) need to have a solid understanding of the anatomy and physiology of the nervous system, as well as how massage effects the nervous system. Not only because this is on the massage exam, but because the nervous system is involved with many of the reasons why our clients come to see us.

For example, clients often seek out massage therapy for relief from conditions that involve the nervous system. This includes: relief from pain, to balance muscle tone related to abnormal posture or movement, to reduce symptoms associated with chronic conditions, and to provide relief from stress-related disorders.

What is the nervous system? The nervous system is a communication network within the body composed of neurons (nerve cells) and glia (support cells). These neurons form “highways” throughout the body that conduct electrochemical signals to other structures in the body such as the brain. The basic anatomy (structure) of the nervous system consists of two parts: the central nervous system (brain and spinal cord), and the peripheral nervous system.

The goal of this post is to present the most important concepts of the nervous system in a concise and organized study guide format that is relevant for massage students preparing for the MBLEx.

Structure and function of the nervous system

The nervous system is composed of the brain, spinal cord, accessory cells, sensory organs, and all of the peripheral nerves throughout the body. The anatomy and physiology content outline for the MBLEx lists the “special senses” as a separate system, however there is a lot of overlap between these two systems of the body.

The nervous system is divided into two main parts: the central nervous system (CNS) and the peripheral nervous system (PNS). The central nervous system includes the brain and spinal cord. The peripheral nervous system includes all of the nerves and support cells outside of the CNS. More on this in the sections below.

This is the structural classification of the nervous system:

The nervous system could also be divided based on functional classification, i.e. sensory and motor. The sensory division receives information from external stimuli as well as stimuli within the body. The motor division processes and sends impulses to the muscles, glands and other tissues of the body to create a response, such as movement or to alter the rate of an organ’s function.

The primary function of the nervous system is to enable communication within the body so that all the systems of the body can function in a coordinated manner, and maintain homeostasis. The nervous system does this by creating and transmitting electrochemical signals between the brain and the rest of the body. This includes all of the body’s systems such as the muscular, cardiovascular, respiratory, integumentary, endocrine, etc. The brain processes and interprets all of this information and decides what actions to take. Most of this is done automatically without our conscious awareness of it.

*Nervous tissue is one of the 4 main types of tissues in the body:

• Nervous tissue
• Epithelial tissue
• Muscle tissue
• Connective tissue

Check out our article on concept mapping to find out how to create visual study tools like this.

Central nervous system overview

The central nervous system (CNS) consists of the brain and spinal cord. The brain is the information processing center of the body. It receives information in the form of electrochemical impulses from the peripheral nervous system via the spinal cord, and then interprets this information to form a response.

Three meninges, or membranes, cover the brain and spinal cord. Their function is to form a protective barrier that protects the CNS from bacteria, microorganisms, chemicals and other pathogens.

• Dura mater. This is the thickest, toughest and most superficial of the three meninges. The name means “tough mother”.
• Arachnoid mater. The middle meninge. Cerebrospinal fluid flows under the arachnoid mater, in the subarachnoid space.
• Pia mater. This is the thinnest and innermost layer. The name means “tender mother”.

Cerebrospinal fluid (CSF) is the clear, watery fluid that surrounds and circulates around the brain and spinal cord. It is produced in the ventricles of the brain, by a structure called the choroid plexus. CSF has five main functions. Each of these functions basically come down to providing protection and support for the brain and spinal cord. Here are the main functions of cerebrospinal fluid (CSF):

1. Cushion the brain and spinal cord from shock, trauma and vibration
2. Maintain a consistent pressure within the cranium
3. Provide lubrication between the soft nervous tissues of the brain and spinal cord, and the hard bones that surround/protect them (skull and vertebral column)
4. Provide nutrients for the brain and spinal cord
5. Transport waste products and harmful substances like chemicals and pathogens away from the brain

Now let’s take a closer look at the main structures of the central nervous system.

Brain anatomy and function

The human brain is the control center of the body. It weights about three pounds and is divided into three main areas: the cerebrum, cerebellum, and brainstem. This small organ is what enables us to have creativity, emotion, intelligence, memory and movement so that we can interact with our world.

The brain contains about 100 billion neurons, or nerve cells. Since each of these nerves has the potential to connect with up to 10,000 other neurons, this means that there are potentially 100 – 1,000 trillion synaptic connections. The brain uses these connections to process all of the information it receives through our five senses: sight, smell, touch, hearing and taste. It also integrates information it receives from other sensory receptors within the body such as sensory input about proprioception, organ function, and other body processes.

Cerebrum

The cerebrum is the largest part of the brain. Much of the information processing that occurs in the brain does so in the cerebral cortex, which is the outermost layer of the cerebrum. The cerebral cortex appears as grey matter because it is composed of the nerve cell bodies. It has a convoluted appearance due to the numerous ridges or folds called gyri (singular = gyrus), and grooves or depressions called sulci (singular = sulcus). These structures function to increase the surface area of the brain, much like the villi and microvilli increase the surface area of the intestines.

Grey matter = nerve cell bodies. The superficial layer of the brain and the deep area of the spinal cord are grey matter.
White matter = myelinated axons. The deep area of the brain and the superficial area of the spinal cord are white matter.

The cerebrum is divided into two hemispheres, left and right. These two hemispheres are divided by a deep groove called the longitudinal fissure. The two hemispheres are connected by the corpus callosum, which transmits messages between the hemispheres. Each hemisphere controls the actions and receives sensory input from the opposite side of the body. This is why a stroke on the left side of the brain affects the right side of the body, and vice versa. The cerebrum receives its blood supply from the three cerebral arteries (anterior, middle and posterior).

Each cerebral hemisphere is divided into four lobes. The names of these lobes correspond with the names of the skull bones that cover them.

• Frontal lobe. This area is associated with intelligence and higher cognitive functions, reasoning and judgement, concentration, self-awareness, problem solving, personality and behavior, expressive language (Broca’s area), and movement of the body. The motor cortex is located in the frontal lobe. It is involved with the planning, control and execution of voluntary movement.
• Temporal lobe. This area of the cerebrum is associated with hearing, processing and interpreting sounds and language (Wernicke’s area), the retention of memory, and emotions. The auditory cortex is located in the temporal lobe.
• Parietal lobe. This area is associated with interpreting physical sensations (pain, touch, temperature, etc.), recognizing and interpreting sounds, words and language, and processing sensory information from the special senses. The somatosensory cortex is located in the parietal lobe.
• Occipital lobe. This area of the cerebrum has the function of receiving and interpreting information received from the retinas of the eyes. It interprets light, color, and movement. The visual cortex is located in the occipital lobe.

Cerebellum

The cerebellum is sometimes referred to as the “Little Brain”. It composes about 10% of the mass of the brain, but accounts for more than half of the total number of neurons of the brain. The cerebellum is located posterior to the brainstem, just below the occipital lobe of the cerebrum.

The primary functions of the cerebellum include assisting with movement and motor control, coordination, and controlling balance and posture. It functions in learning repetitive and automated movements that require accuracy and coordinating a lot of different muscles for fluid motion. Examples include walking, riding a bike, typing, tying your shoes, and playing an instrument. The cerebellum also plays a role in some cognitive processing and sensory discrimination. Alcohol is particularly damaging to the cerebellum.

Brainstem

The brainstem (or brain stem) is the oldest part of the brain (in terms of evolution), and connects the cerebrum to the spinal cord. It is a small but important part of the brain that controls many autonomic functions of life such as heart rate, breathing and blood pressure. The brainstem is composed of the midbrain, pons, and the medulla oblongata. *10 of the 12 cranial nerves originate at the brainstem (CNIII – CNXII).

Other important parts of the brain

The thalamus is located above the brainstem, and functions as a relay station for nervous signals entering the brain and signals moving to different parts of the brain. It also contributes to levels of alertness, attention and the sensation of pain.

The hypothalamus is located just below the thalamus, and above the pituitary gland. It has many important functions and is part of the brain, but also considered the master gland because of its control over the autonomic nervous system and the endocrine system. The hypothalamus regulates functions such as body temperature, emotions, hunger and thirst, circadian rhythms, and influencing the endocrine system. The hypothalamus controls the actions of the pituitary gland, and has an important role in maintaining homeostasis. It makes sense that such a critical part of the brain is located in the center of the brain, where it is most protected.

The limbic system of the brain is composed of the amygdala, hippocampus, limbic cortex and septal area. It primarily functions in emotional responses, as well as learning and memory.

Spinal cord anatomy and function

Axons carry information up the spinal cord to the brain in the ascending tracts (sensory). Axons also carry information from the brain down the spinal cord in the descending tracts (motor). These tracts are located in the white matter of the spinal cord.

Reflex arc

Reflexes are an important function of the nervous system. Reflexes can affect the organs of the body (autonomic reflex arc), or they can affect the muscles (somatic reflex arc). This reflex function uses the nerves of both the central and peripheral nervous systems.

Below is an example of how the somatic reflex works in response to a painful stimulus. It is unlikely that there will be any questions on the MBLEx that go into more depth than this. It is also unlikely that you will see questions about different nerve fiber types (A, B, or C group, etc.). I just present it here as a reference, and you could see it on an anatomy and physiology test in your massage school.

Here are the basic steps of the reflex arc:

1. Initial painful stimulus triggers the receptors in the skin
2. A nerve impulse speeds along the afferent nerve fibers to the dorsal horn of the spinal cord
3. Interneurons are stimulated, and send messages to two places:
   1. Directly to the muscles to withdraw the arm and pull the finger away from the noxious stimulus (see #4).
   2. Up the ascending tracts of the spinal cord to the brain for processing, to see if any other action needs to be taken, and to interpret the sensation.
4. The signal leaves the spinal cord through the anterior (ventral) horn and nerve root. It travels along efferent fibers to muscles that can withdraw the arm.

Peripheral nervous system

The peripheral nervous system contains of all the nervous system structures outside of the brain and spinal cord. This includes the nerves throughout the body, the cranial nerves, the nerve roots that exit the spinal cord, ganglia and sensory receptors.

*The peripheral nervous system is divided into the somatic nervous system and the autonomic nervous system.

Somatic nervous system

The somatic nervous system is also known as the voluntary nervous system because it innervates muscles that are under our voluntary control. For example, skeletal muscles which produce movement of the body, are innervated by the somatic nervous system. This division of the peripheral nervous system includes both sensory and motor nerves. The somatic nervous system consists of two main groups of nerves:

1. Spinal nerves
2. Cranial nerves

Spinal nerves

• 8 Cervical spinal nerves innervate muscles of the head and neck, shoulders, arms, hands, and diaphragm.
• 12 Thoracic spinal nerves innervate muscles of the chest, back and parts of the abdomen.
• 5 Lumbar spinal nerves innervate the lower abdomen and back, and some of the pelvic region, glutes and lower extremities.
• 5 Sacral spinal nerves innervate the some of the legs and pelvic region.
• 1 Coccygeal spinal nerve innervates the skin over the coccyx.

*Note: there are 8 cervical spinal cord segments but there are only 7 cervical vertebrae. This is because the C1 spinal nerve exits the spinal cord above C1, and the C8 spinal nerve exits that spinal cord below C7.

As a spinal nerve exits the spinal cord, it merges and divides with the spinal nerves from the surrounding spinal levels in something called a plexus. It is beyond the scope of the massage licensing exam (MBLEx) to know the details of how the plexuses merge and divide (e.g.: the roots, trunks, divisions and cords of the brachial plexus). Just know that the end result is that most of the large nerves in the body carry nerve fibers from multiple spinal levels.

For example, the median nerve originates in the brachial plexus and innervates multiple muscles in the upper extremity. It carries nerve fibers from the C5 – T1 spinal nerves. There are 5 spinal nerve plexuses:

• Cervical plexus
• Brachial plexus
• Lumbar plexus
• Sacral plexus
• Coccygeal plexus

Cranial nerves

Cranial nerves are also considered part of the peripheral nervous system. There are 12 pairs of cranial nerves. They originate from the brain, with CNIII – CNXII originating from the brainstem. You will most commonly see them labeled with Roman numerals. Like many other parts of the body, cranial nerves are named according to their structure or function. Some of the cranial nerves are sensory (afferent) only, some are motor (efferent) only, and some are mixed nerves (carry both sensory and motor nerves).

1. Olfactory nerve (CNI). Sensory nerve. Carries information about smells from the olfactory bulb to the frontal lobe of the cerebral cortex.
2. Optic nerve (CNII). Sensory nerve. Carries information vision from the retina of the eyes to the primary visual cortex in the occipital lobe of the cerebrum.
3. Oculomotor nerve (CNIII). Motor nerve. Innervates 4 of the 6 muscles that move the eye, and controls the size of the pupil. The nerve originates on the brainstem.
4. Trochlear nerve (CNIV). Motor nerve. Innervates 1 of the 6 muscles that move the eye. Originates on the brainstem.
5. Trigeminal nerve (CNV). Sensory and motor nerve. This is the largest of the cranial nerves. Has three divisions (ophthalmic, maxillary and mandibular). It carries sensory information from the face. Only the mandibular division has a motor function (innervates several muscles of the jaw). Originates on the brainstem.
6. Abducens nerve (CNVI). Motor nerve. Innervates 1 of the 6 muscles that move the eye. Originates on the brainstem.
7. Facial nerve (CNVII). Sensory and motor nerve. Innervates the muscles of facial expressions and some jaw muscles. It also supplies innervation to the glands of the head and neck (salivary glands and lacrimal glands). Carries sensory information from most of the tongue and the outer ear.
8. Vestibulocochlear nerve (CNVIII). Sensory nerve that carries sensory information about sound and vestibular (balance) function.
9. Glossopharyngeal nerve (CNIX). Sensory and motor nerve. Carries nerve impulses to and from the sinuses, tongue and back of the throat.
10. Vagus nerve (CNX). Sensory and motor nerve. The vagus nerve is the longest of the cranial nerves and has the main function of innervating the thoracic and abdominal viscera. Is also called the pneumogastric nerve.
11. Accessory nerve (CNXI). Motor nerve that controls the muscles of the neck (sternocleidomastoid and trapezius).
12. Hypoglossal nerve (CNXII). Motor nerve. Controls most of the tongue movement.

It is good for a massage therapist to have at least a basic understanding of the cranial nerves. I doubt you will see any questions about a specific cranial nerve’s function on the MBLEx. But it is possible. I’ve bolded the cranial nerves that many of my previous instructors have seemed to like to ask questions about.

This information is much more relevant for paramedics, athletic trainers and neurology specialists. However, you may be tested on this in your anatomy and physiology class in your massage school, so I am including it here for a reference.

There are many mnemonics that people have developed to help remember the 12 cranial nerves. One is, “Ooh. Ooh. Ooh. To Touch And Feel Very Good Velvet. AH!”

*Even though the cranial nerves are structurally classified as part of the somatic nervous system, they do perform some functions of the autonomic nervous system too.

Autonomic nervous system structure and function

The autonomic nervous system (ANS) is the other major division of the peripheral nervous system. The function of the autonomic nervous system is to regulate the involuntary (unconscious) activities of the body. The ANS is divided into the sympathetic nervous system and parasympathetic nervous system. These two divisions of the autonomic nervous system have antagonistic or complementary functions. This means that they produce opposite effects on the systems and organs of the body.

Most of the organs of the body have dual innervation, meaning that they are innervated by both the sympathetic and parasympathetic divisions of the nervous system. One system will cause and increase in activity (excitation), and the other will cause a decrease in activity (inhibition). For example, the sympathetic neurons speed up the heartbeat and the parasympathetic neurons slow it down. This opposition enables the ANS to maintain homeostasis even as the body faces changing situations or environmental factors.

Sympathetic nervous system

The sympathetic nervous system. It is also referred to as the thoracolumbar division of the ANS because the outflow of sympathetic nerve impulses originate in the thoracic and lumbar regions of the spinal cord.

The sympathetic nervous system is more active during times of high physical or emotional stress. Its function supports intense physical activity and mobilization of energy reserves. This is useful for a person to survive a real or perceived threat, and is commonly referred to as the “fight-or-flight” response. Sometimes it is called the “fight, fright or flight” response. During periods of heightened sympathetic nervous system activity, the body speeds up and becomes more alert. Functions that are not critical to survival in the moment are shut down.

Chronically high sympathetic nervous system activity can cause fatigue, breakdown and even disease in the body. Sometimes this is referred to as adrenal fatigue. To help remember when the sympathetic nervous system is most active, just remember the 4 E’s: exercise, excitement, embarrassment, emergency.

Parasympathetic nervous system

The parasympathetic nervous system (PSNS) is another division of the ANS. It is also sometimes called the craniosacral division because the nerves of the PSNS arise from the cranial and the sacral regions. The parasympathetic nervous system is commonly referred to as the “rest and digest” or the “breed and feed” system because these activities are primarily regulated by the PSNS. This division of the ANS provides a complementary function that counterbalances the sympathetic nervous system.

Effects of sympathetic and parasympathetic activity:

Sympathetic Functions & Effects	Parasympathetic Functions & Effects
Fight or flight	Rest and digest
Increase heart rate and force of contractions	Decrease heart rate and force of contractions
Increase blood pressure	Decrease blood pressure
Dilate the bronchial tubes to increase airflow	Constrict the bronchial tubes
Trigger processes that break down stored fuel reserves to increase blood glucose level and produce energy	Stimulate the body to increase stored energy reserves
Constrict circulation to organs not needed to respond to a threat (kidneys, GI tract, etc.)	Increase circulation to the digestive system. Increased salivation.
Increased tone in skeletal muscles	Decreased tone in skeletal muscles
Pupils dilate	Pupils constrict
Decreased urinary output. Increased sweating.	Increased urinary output

Enteric nervous system

The enteric nervous system (ENS), also called the intrinsic nervous system, is a division of the autonomic nervous system that is located in the wall of the gut. It is responsible for regulating the function of the digestive organs. The enteric nervous system can coordinate the digestive function with the CNS, but it can also work independently. The number of neurons in the ENS is similar to the number found in the spinal cord. This system is often referred to as the “brain of the gut”, the “second brain”.

Nerves

The basic unit of the nervous system is the nerve cell, also called a neuron. These cells communicate information within the body by transmitting electrochemical signals. Neurons come in different sizes and shapes including unipolar, bipolar and multi-polar nerves (you are unlikely to see detailed questions about types of neurons on the MBLEx).

Just like muscle fibers and fascicles are bundled and have different layers of connective tissue to protect and bind them (epimysium, perimysium and endomycium), nerves of the peripheral nervous system have protective layers.

A large peripheral nerve is covered by the epineurium, which is the outermost layer. The nerve fascicles within are covered by the perineurium. And at the deepest layer, the individual axon and myelin sheath is covered by the endoneurium.

Structure and function of nerves

*There are 3 main parts of any nerve: the cell body, axon, and dendrites.

Cell body. The nerve cell body (or soma) contains the nucleus of the nerve cell.

Axon. This is a long, slender projection that carries nerve impulses away from the cell body. Some axons are myelinated. Axons can be quite long. For example, the cell body of the motor nerves that innervate the toes is located in the spinal cord, and the axon extends all the way to the toes. The axon terminal is the bulb-shaped end of the axon that contains neurotransmitters.

Dendrite. Finger-like extensions that carry the nerve impulse toward the nerve cell body.

Three types of nerves:

• Afferent or sensory nerves. These nerves send information received from the internal organs or sensory organs to the central nervous system. They transmit electrochemical impulses in only one direction.
• Efferent or motor nerves. These nerves carry carry signals only in one direction, from the central nervous system to effectors (recipients) such as muscles, organs or glands.
• Interneurons. These are relay nerves located in the central nervous system that connect nerve cells. It is these interneurons that connect the sensory to the motor nerves, and play an important role in spinal reflexes.

Mixed nerves are a bundle of sensory and motor nerves, so they carry the nerve impulses in two directions. Most large nerves of the peripheral nervous system are mixed nerves.

Major peripheral nerves of the body

The large nerves of the body are made of a bundle of axons. Major nerves are usually mixed nerves, meaning they carry sensory (afferent) and motor (efferent) nerve impulses. Remember that cranial nerves (discussed earlier) are also considered peripheral nerves.

*Major peripheral nerves that massage therapists should be familiar with for the MBLEx are listed in the columns below. Be familiar with the location and path of these nerves, and what structures are nearby. It is important to know this information not just for the massage exam, but to avoid damaging any of these nerves when working with clients. Some of these nerves have vulnerable sections, which are called endangerment sites.

Nerve support cells

The nervous system also includes support cells or “helper cells”, called glia cells, or neuroglia. These cells do not carry electrical impulses, but they do perform the important function of supporting and protecting the neurons. There are different types of glial cells including: astrocytes, ependymal cells, microglia, Schwann cells, and satellite cells. There are more neuroglia in the body than there are actual nerve cells.

You may need to know the specific glial cells for your massage school classes, but it is unlikely that you will see detailed questions about these on the MBLEx. An exception however is that you may see Schwann cells on the massage exam. Schwann cells are also called neurolemmocytes, and they form the myelin sheath around the axons of motor and sensory nerves in the peripheral nervous system. Similarly, the oligodendrocytes are neuroglia that myelinate nerves in the central nervous system.

*The myelin formed by the Schwann cells and the oligodendrocytes has two main functions:

1. Speed up nerve conduction
2. Protect the axon by supporting nerve regeneration if damaged

Neurotransmitters

The neurotransmitters are chemical messengers that nerves use to transmit a signal across the synapse. A synapse is a “space” between two nerves, or between a nerve and its target cell. Neurotransmitters are how a nerve communicates with other nerves or target tissues such as muscle cells or glands.

There are many different types of neurotransmitters. They can be excitatory, inhibitory, or perform other functions. Some of these organic chemicals, for example serotonin and dopamine, can function as both a neurotransmitter and a hormone (endocrine system). Here is a list of just a few commonly discussed neurotransmitters.

These neurotransmitters are held in the synaptic terminals at the end of the axon, and are released across the synaptic cleft to create a response in the next neuron or the target tissue.

Common nervous system disorders massage therapists should know

There are four primary classifications of the causes of nervous system disorders:

• Degenerative: examples include Alzheimer’s disease and other types of dementia, Parkinson’s disease, multiple sclerosis (MS), and amyotrophic lateral sclerosis (ALS).
• Structural: This is the cause of conditions such as carpal tunnel syndrome, thoracic outlet syndrome, sciatica, Bell’s palsy, brain tumor, peripheral neuropathy, stenosis. Trauma can lead to structural disorders.
• Vascular: examples include stroke (CVA), transient ischemic attack (TIA or “mini-stroke”), brain hemorrhage or hematoma.
• Infections: This is the cause for diseases such as meningitis, encephalitis, and polio.

Central nervous system disorders

The following disorders, pathologies and diseases primarily and directly affect the central nervous system. However, they also cause secondary effects on the peripheral nervous system.

Stroke	Also called a cerebrovascular accident (CVA) if the stroke affects the cerebrum (the stroke could affect other areas of the brain instead, such as the brainstem). An ischemic stroke can be caused by a blood clot that forms in the brain (thrombus), or one that travels to the brain and gets stuck there (embolism) and cuts off blood supply. Most strokes are ischemic strokes (87%). The other type is a hemorrhagic stroke, when there is bleeding in the brain, as with an aneurysm. A transient ischemic attack (TIA) is known as a “mini-stroke” in which symptoms resolve in <24 hours.
Dementia	Dementia is a progressive degenerative disease of the brain that commonly affects the geriatric population. Alzheimer’s disease is one form of dementia. The severity and rate of progression can vary. Dementia can affect the memory, cognition, language, and judgement, and cause increased difficulty performing routine activities.
Parkinson’s Disease	A degenerative and progressive disease of the CNS that is characterized by movement abnormalities including: tremors, difficulty with walking and balance, limb stiffness, and falls due to inability to self-correct loss of balance. There are commonly cognitive declines as well, which include: dementia, impaired language and speech, and emotional imbalance.
Epilepsy	This is a neurological disorder characterized by recurrent episodes of seizures.
Multiple sclerosis	MS is a progressive demyelinating disease of the brain and spinal cord. The immune system attacks and deteriorates the fatty sheath (myelin) around these nerves. Symptoms vary, but often include: impaired mobility, numbness, weakness, decreased coordination, impaired cognition, tremors, vision problems, fatigue, tingling, and dizziness.
Amyotrophic Lateral Sclerosis	Also known as ALS or Lou Gehrig’s disease, it is a disease of the motor neurons, primarily in the central nervous system. This causes the nerves that innervate muscles to die, and results in a loss of voluntary movement. ALS can also involve the lower motor neurons.

Peripheral nervous system disorders

Peripheral neuropathy	This is a broad group of nervous system disorders. Peripheral neuropathy is characterized by damage to nerves of the PNS due to traumatic injury, infections, metabolic conditions, genetic predisposition, alcoholism, or exposure to toxic substances. Specific examples include diabetic neuropathy, Bell’s palsy, and nerve compression disorders (see below).
Nerve compression disorders	These are any condition in which a nerve is squeezed or entrapped. This could include stenosis, sciatica, thoracic outlet syndrome, carpal tunnel syndrome, cubital tunnel syndrome (ulnar nerve entrapment at the elbow), and others. The causes can vary, but could include trauma, degenerative changes, or pathological process.

How the nervous system interacts with other body systems

All of the systems of the body are interconnected in order to perform their functions and maintain homeostasis. The nervous system and the endocrine system have important roles which are largely focused on communication within the body. These two systems help other systems of the body function in a coordinated manner. The following sections describe the main ways that the nervous system interacts with the other major systems of the body.

Muscular system

The brain plans and coordinates movement, especially the motor cortex of the cerebrum and the cerebellum. Stimulation from the brain can also cause the muscles to activate and generate heat in order to maintain body temperature if needed. The somatic nervous system stimulates skeletal muscle contraction which permits movement of the body. Nerves within the autonomic nervous system (ANS) stimulate smooth muscle contraction which enables movement through the digestive tract. The ANS nerves also stimulates glandular function. Receptors within the muscles and tendons provide the brain information about the position and movement of different areas of the body.

Endocrine system

The nervous system can perceive dangerous or stressful situations and stimulate the endocrine system to release hormones such as adrenaline and cortisol into the blood. This can help the body to respond to emergencies by mobilizing energy reserves. It can also stimulate the production of antibodies and lymphocytes to strengthen the immune system. The hormones of the endocrine system provide feedback for the brain about the state of various processes, tissues and organs of the body. The hypothalamus of the brain influences the endocrine glands including the adrenal glands, pituitary gland, and thyroid gland.

Circulation system

The nervous system effects the circulation system by stimulating the heart to contract. It also controls the rate and strength of contractions as needed by the body. Electrical signals within the heart muscle itself (the SA node) help to maintain a steady heart rate. A thin layer of endothelial cells form a selectively-permeable blood-brain barrier that allows certain nutrients to pass through the the brain. This blood-brain barrier restricts pathogens and other harmful substances from passing through. The brain regulates the heart rate and blood pressure of the circulatory system. Baroreceptors monitor blood pressure and intracranial pressure. Cerebrospinal fluid is continuously being produced and replaced at a rate of about 600 – 700 ml/day. The excess is absorbed across the arachnoid into the venous circulation.

Respiratory system

The brain regulates the rate of respiration, the respiratory volume and the levels of various gasses in the blood. The autonomic nervous system can dilate or constrict the bronchial tubes depending on the needs of the body.

Digestive system

The autonomic nervous system provides the stimulation for the smooth muscle around the digestive tract. This enables swallowing, churning of the stomach, and peristalsis needed to propel and break down food, as well as eliminate waste products. The nervous system controls the sensations of hunger and thirst. The digestive system provides the nutrients that the nervous system uses as building blocks.

Integumentary system

The integumentary system contains the nervous system’s receptors. Touch, pressure, temperature, pain, and vibration receptors are located in the dermis of the skin. These receptors send information to the brain via the spinal cord. The autonomic nervous system assists in regulating the amount of sweating and capillary dilation within the vessels of the skin. The two systems work together to regulate body temperature.

Lymphatic system

The nervous system helps to regulate the lymphatic system function and immune response. The lymphatic system helps in the removal of toxins throughout the body which are harmful to the brain, spinal cord and rest of the nervous system. This is particularly important in preventing systemic infection.

Reproduction system

The nervous system has a significant effect on the reproductive system. The sympathetic and parasympathetic divisions of the autonomic nervous system, and parts of the brain influence everything from sexual behavior, arousal, physical sensation, mate selection to physical development from gestation to puberty.

Skeletal system

The bones provide calcium, which is needed for the nervous system to function. Receptors in and around the joints provide the brain with information regarding the body’s position and movement. The skull and vertebrae protect the brain and spinal cord from injury. The brain indirectly controls the position of the bones by stimulating and coordinating the actions of skeletal muscles.

Urinary system

Kidney function is regulated by the central nervous system as well as the endocrine system. The urinary bladder receives innervation from both the sympathetic and parasympathetic nervous system. Dysfunction of the nerves that control urination can lead to incontinence. Urination is controlled by the brainstem.

Effects of massage on the nervous system

Massage therapy can have significant therapeutic effects on the nervous system. One of the most commonly discussed benefits of massage is a reduction in sympathetic nervous system activity and increased parasympathetic nervous system activity. This results in beneficial physiological changes such as reducing blood pressure and balancing hormone levels.

The beneficial effects of therapeutic massage on the nervous system can be reflexive effects or mechanical effects.

*Mechanical effects of massage are direct effects that result from using therapeutic massage techniques to correct or reduce the structural problems due to musculoskeletal dysfunction.

For example, using massage techniques to reduce tight muscles and connective tissue associated with carpal tunnel syndrome, piriformis syndrome, lumbar stenosis, thoracic outlet syndrome, scoliosis, or other structural dysfunction which can compress nerves.

*Reflexive effects of massage are indirect responses to soft tissue techniques in which the tissues and physiology throughout the body are affected due to stimulation of the nervous system.

For example, a relaxing massage that stimulates the parasympathetic nervous system will relax the blood vessels in the extremities and increase peripheral circulation.

Many of the benefits for the nervous system from massage therapy are indirect and reflexive:

• Massage can help with pain reduction. This is often explained through the gate control theory of pain.
• Massage stimulates increased parasympathetic nervous activity and can produce a calming effect (relaxation response). This can benefit people with anxiety disorders, dementia, PTSD, terminal illness, ADHD, and others with symptoms of anxiety.
• Massage stimulates the sensory receptors (part of the nervous system) of the skin, and this pleasurable sensation affects the body’s hormone balance. The changes in the levels of certain hormones such as dopamine then go on to influence the function of the nervous system.

The primary effect that massage therapy has on the nervous system as a whole, is that it stimulates the parasympathetic nervous system. This is especially true with a “relaxation massage”.

Summary of key nervous system terminology and concepts

Here is a quick review that may help you in your massage therapy classes or MBLEx test prep. Most of these terms have slightly different definitions depending on the source. But the interpretations presented here are commonly accepted within massage therapy education programs and on the massage exam. Be sure to see our glossary of massage terms.

Neuron: nerve cell. Includes 3 main parts: cell body, dendrite (transmits electrical signals towards the cell body), and axon (transmits signals away from the cell body).

Action potential: a rapid wave of electrical depolarization of the membrane of axon of a nerve cell. Kind of like a row of dominos falling. Nerves conduct this impulse at 100 – 300 feet per second!

Synapse: the junction between the axon terminal and the target cell (e.g. muscle cell, gland, or other neuron).

Neurotransmitter: chemical messengers that transmit signals across a chemical synapse, such as from one neuron to the next, or across a neuromuscular junction. Some of these chemicals can be both a neurotransmitter and a hormone (endocrine system).

Ganglia: cluster of peripheral nerve cell bodies. An example is the dorsal root ganglia which is a cluster of cell bodies of sensory (afferent) nerves at each spinal level.

Nerve plexus: an interwoven network of nerves. The main nerve plexuses in the body are the cervical plexus, brachial plexus, lumbar plexus, sacral plexus and coccygeal plexus.

Efferent: means “away”. An efferent nerve transmits the electrical impulse away from the spinal cord. These are also called motor nerves or motor neurons.

Afferent: means “towards”. An afferent nerve transmits the electrical impulse toward the spinal cord. These are also called sensory nerves.

Central nervous system (CNS): composed of the brain and spinal cord.

Peripheral nervous system (PNS): all the nerves outside of the brain and spinal cord. The PNS is divided into the somatic nervous system and the autonomic nervous system.

Somatic nervous system: a division of the PNS. It is also called the voluntary nervous system. It transmits efferent signals via motor nerves from the CNS to the skeletal (voluntary) muscles. The somatic nervous system also transmits afferent signals from sensory receptors in the skin, eyes, nose, ears, etc., to the CNS.

Autonomic nervous system (ANS): A division of the PNS that innervates involuntary muscle and glands (e.g. heart, intestines, stomach, adrenals, etc.). The autonomic nervous system is divided into the sympathetic nervous system and the parasympathetic nervous system.

Sympathetic nervous system: This division of the ANS that stimulates the “fight, flight, or fright” response.

Parasympathetic nervous system: This division of the ANS is the antagonist to the the sympathetic nervous system. It is also called the “rest and digest” or the “feed and breed” part of the nervous system. Massage therapy produces many beneficial effects by stimulating the parasympathetic nervous system.

Neuralgia: means “nerve pain”. Clients usually describe nerve pain as burning, tingling, prickling, pins and needles, shooting, stabbing, sharp, or electric. Nervous system disorders can also result in symptoms of numbness.

Neuropathy: is defined as a disease or abnormality of the nervous system.

Neurology: branch of biology and medicine that studies the nervous system and treats nervous system disorders.