How Many Nerves In Human Body?


How Many Nerves In Human Body
From Wikipedia, the free encyclopedia

Afferent nerve fiber
Afferent nerve fibers transmit information from the peripheral to the central nervous system.
System Nervous system
Latin Neurofibrae afferentes
TA98 A14.2.00.017
TH H2.
FMA 76570
Anatomical terms of neuroanatomy

Afferent nerve fibers are axons (nerve fibers) of sensory neurons that carry sensory information from sensory receptors to the central nervous system, Many afferent projections arrive at a particular brain region. In the peripheral nervous system afferent nerve fibers are part of the sensory nervous system and arise from outside of the central nervous system.

How many nerves go to the brain?

How many cranial nerves are there? – You have 12 cranial nerve pairs. Each nerve pair splits to serve the two sides of your brain and body. For example, you have one pair of olfactory nerves. One olfactory nerve is on the left side of your brain and one is on the right side of your brain.

What are the 14 nerves?

Compression – Nerves may be compressed because of increased intracranial pressure, a mass effect of an intracerebral haemorrhage, or tumour that presses against the nerves and interferes with the transmission of impulses along the nerve. Loss of function of a cranial nerve may sometimes be the first symptom of an intracranial or skull base cancer.

  • An increase in intracranial pressure may lead to impairment of the optic nerves (II) due to compression of the surrounding veins and capillaries, causing swelling of the eyeball ( papilloedema ).
  • A cancer, such as an optic nerve glioma, may also impact the optic nerve (II).
  • A pituitary tumour may compress the optic tracts or the optic chiasm of the optic nerve (II), leading to visual field loss.

A pituitary tumour may also extend into the cavernous sinus, compressing the oculomotor nerve (III), trochlear nerve (IV) and abducens nerve (VI), leading to double-vision and strabismus, These nerves may also be affected by herniation of the temporal lobes of the brain through the falx cerebri,

How long would your nerves stretched out?

Where did the first nerves come from? | Ask Dr. Universe | Washington State University Dear Max, Clap your hands. Stomp your feet. Blink your eyes. Every time you move, the brain and body send messages to each other. Under your skin, your nerves stretch out like a network of wires across the body.

  • They help carry these messages from one part of the body to another.
  • My friend Samantha Gizerian, a neuroscientist at Washington State University, explained how nerves help our bodies work and told me a bit about the first ones.
  • She says our bodies are made up of lots of different kind of cells, which are kind of like building blocks.

Some of these are nerve cells. We would need a microscope to see them, but they are some of the oldest and longest cells in your body. In fact, if we lined up all the nerves a body has, they would stretch for almost 45 miles. While the human body has many parts made up of lots cells, some living things are actually just one little cell—an amoeba or a bacteria, for example.

“What I can tell you about the earliest nerves is that when the first groups of single-celled organisms started forming colonies, they weren’t terribly successful because the individual cells in each colony couldn’t talk to each other,” she said. They didn’t use words to talk to each other like you and me, but they created their own ways to send messages.

Gizerian says nerve cells are basically tiny bags of salt water. They have lots of tiny particles called ions floating around on their insides, which makes them like natural batteries, with electrical charges that flow from one place to another. “Eventually as these colonies developed from individual single cells into organisms made of many cells, some cells became specialized for communication by electricity,” she says.

These were the first nerve cells.” These days animals have nervous systems that are more complex. After all, you have a lot more nerve cells than an amoeba. Optical nerves in your eyes help you see. Olfactory nerves in your nose and face help you smell things. It takes a lot of nerves to help the brain and body communicate.

In fact, the human body has about 100 billion nerve cells. Only one other mammal on earth has more, a dolphin called the long-finned pilot whale. Whether you are a dolphin, a human, or a cat, the nervous system helps you move around and sense the world.

  1. Eep asking great questions, Max.
  2. Who knows, you might just grow up to be a scientist.
  3. One last thing.
  4. Gizerian and her students recently helped a few fifth graders visiting WSU learn about the brain and they built their own neuron.
  5. You can use play dough or make and shape it into your own neuron model and label its different,

Send us a photo of your project sometime at,

Do humans have 12 spinal nerves?

Neuroanatomy, Spinal Nerves The spinal nerves emanate from the spinal cord as pairs of nerves composed of both sensory and motor fibers that function as the intermediary between the central nervous system (CNS) and the periphery. These mixed nerves collectively transmit sensory, motor, and autonomic impulses between the spinal cord and the rest of the body.

  1. In total, there are 31 pairs of spinal nerves grouped regionally by spinal region.
  2. More specifically, there are eight cervical nerve pairs (C1-C8), twelve thoracic nerve pairs (T1-T12), five lumbar nerve pairs (L1-L5), 5 sacral (S1-S5), and a single coccygeal nerve pair.
  3. While the nerves branch directly from the spinal cord and the central nervous system, the spinal nerves classify as a part of the peripheral nervous system.

Spinal nerves are mixed nerves that interact directly with the spinal cord to modulate motor and sensory information from the body’s periphery. Each nerve forms from nerve fibers, known as fila radicularia, extending from the posterior (dorsal) and anterior (ventral) roots of the spinal cord.

  • The roots connect via interneurons.
  • Grossly, the root fibers join together within the intervertebral foramina to form a spinal nerve.
  • The dorsal root is composed of afferent sensory axons that transmit visceral and somatic sensory information from peripheral receptors back to the central nervous system.

Areas of cutaneous sensory innervation by specific spinal nerves are mappable in an organized fashion in regions across the body known as dermatomes. While the dorsal root is synapses at the dorsal horn of the spinal cord, the sensory cell bodies of these pseudounipolar neurons are in the dorsal root ganglion, an oval enlargement just outside the cord.

To communicate with the effector division of the spinal nerve, the dorsal root will synapse on an interneuron in the cord’s gray matter as part of the motor reflex arc. However, fibers of the dorsal root may instead ascend through multiple pathways in the spinal cord to provide sensory information to the thalamus.

Meanwhile, the ventral (anterior) root bundle is responsible for transmitting somatic motor output from the brain and spinal cord to the body’s skeletal muscles. Cell bodies of the efferent motor fibers get housed in the anterior horn of the spinal cord, specifically the anterior and lateral gray columns.

  1. All the muscles innervated by a particular spinal nerve are known as the nerve’s myotome.
  2. There are robust enlargements of the cord at the cranial and lumbosacral regions as these areas are responsible for a significant degree of skeletal muscle innervation of the upper and lower extremities, respectively.

The ventral root is composed of both alpha and gamma motor neuron axons, which supply extrafusal and intrafusal striated muscle, respectively. The spinal nerve exits the vertebral canal through the intervertebral foramina as a single fascicle of mixed nerve fibers.

The only exception to this rule is at the C1 spinal level, where the C1 spinal nerve exits the column between the occiput and the atlas (C1). Because the spinal cord does not track the entire length of the vertebral column, spinal nerves in the more cranial regions exit the spinal cord horizontally before directly passing into the periphery.

Meanwhile, spinal nerves caudal to the terminus of the spinal cord (typically at the L1 or L2 vertebral level) must travel inferiorly in the column before exiting. These rootlets are seen anatomically without the spinal cord and are called the cauda equina.

Tracking inferiorly from C1, all spinal nerves above C7 exit the vertebral column above their associated vertebrae. Spinal nerve C8 exits the intervertebral foramina between C7 and T1. All remaining spinal nerves depart the vertebra column caudally to their respective vertebrae. After exiting the vertebral column, the bundled spinal nerve divides into ventral and dorsal rami.

Both rami contain mixed fibers that provide both sensory and motor innervation. The dorsal ramus is typically smaller than its ventral counterpart and consists of a medial and a lateral branch; however, some literature may also refer to a third, intermediate branch.

  1. The branches of the dorsal rami are responsible for innervating paraspinous muscles (the nerve’s myotome) and regions of skin (the nerve’s dermatome) related to the ramus’ vertebral level.
  2. Responsibility of the lateral and medial branches of dorsal rami in thoracic spinal nerves varies based on vertebral level.

Superior to T6, the medial branch provides muscular and cutaneous innervation, and the lateral branch solely provides solely muscular innervation. The opposite is true for these branches caudally to T6. Meanwhile, ventral rami are much more robust in size and function in comparison to their dorsal counterpart.

The ventral rami provide the spinal contributions to all major neural plexuses. As such, they are responsible for the majority of the body’s sensorimotor innervation. Also of note, preganglionic cells within the autonomic nervous system (ANS) are closely associated with the sensorimotor outflow tracts of spinal nerves.

The goal of the ANS is to control visceral motor tone involuntarily. Autonomic central neuronal bodies originate in the regions of the cord’s lateral horn of the cord’s gray matter, specifically in the intermediolateral nucleus. In the thoracic and upper lumbar regions (T1 to L2), these neurons give rise to preganglionic sympathetic axons that exit with somatic motor axons through the spinal cord’s ventral (anterior) root.

The preganglionic fibers travel within white rami communicantes to paravertebral ganglia within the sympathetic trunk. From the ganglia, the sympathetic tone can undergo modulation in smooth and cardiac muscle, glands, and immune system cells via a series of gray rami communicantes and postganglionic fibers.

In the parasympathetic portion of the ANS, preganglionic cells originate in the craniosacral system. Included in this system are cranial nerves III, VII, IX, and X, as well as S2 to S4 of the sacral spinal cord. The preganglionic fibers of the parasympathetic system are much longer than their sympathetic counterparts.

Rather than terminating abruptly at paravertebral ganglion, parasympathetic preganglionic nerves carry impulses to peripherally located visceral ganglia that are anatomically associated with the nerve’s target tissue. Cervical Plexus Much of the upper half of the cervical nerves comprise the cervical plexus, specifically from the anterior rami of C1 to C5.

Its sensory fibers provide cutaneous innervation to the scalp, neck, chest, and axilla, as well as proprioceptive innervation of the same area via the lesser occipital nerve (C2 to C3), the great auricular nerve (C2, C3), transverse cervical nerve (C2, C3), and the supraclavicular nerve (C3, C4).

The motor branches of the cervical plexus promote movement of the neck and innervation of the diaphragm. The cervical plexus also provides motor innervation to the infrahyoid muscles and the sternocleidomastoid via the ansa cervicalis (C1 to C3). Additionally, the anterior rami of the C3 and C4 loop and combine with outputs from C5 to innervate the phrenic nerve to regulate respiration.

Brachial Plexus The brachial plexus is a highly complex network of nerves formed from the ventral roots C5-C8, with additional contribution from T1. The five nerve roots coalesce into trunks, divisions, cords, and branches that innervate about 50 muscles and skin in the upper extremities and pectoral region.

  • C5-C6 form the superior trunk, C7 extends as the middle trunk, and C8 and T1 join to create the inferior trunk.
  • Several significant mixed nerves extend from the brachial plexus, including the axillary (C5, C6), musculocutaneous (C5, C6) radial (C6-C8), median (C5-T1), and ulnar (C8, T1) nerves.
  • Meanwhile, there are a handful of other nerves in the plexus that are solely muscular or cutaneous sensory nerves.
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The nerve fibers of the brachial plexus are also accompanied by autonomic fibers, particularly from T1, that regulate vasomotor control of the upper extremity and trunk. Thoracic Nerves There are 12 pairs of spinal nerves in the thoracic spine, one for each corresponding spinal segment.

The thoracic nerves are responsible for cutaneous innervation of the skin, musculoskeletal system, and viscera. Peripheral and visceral motor fibers also innervate the musculature of the thorax and deep back, abdominal wall, and gut. Because much of the sympathetic trunk arises from the thoracic spine, pre- and postganglionic sympathetic fibers are also found coursing with spinal nerves in this region.

Lumbosacral Plexus The lumbar and sacral plexuses share nerve root overlap and are thus often referred to simply as the lumbosacral plexus. The combined plexus contains roughly 200000 axons and provides all sensory and motor innervation to the lower extremity, with some additional innervation of the abdominal wall.

The combined plexus gives rise to six sensory nerves and six more sensorimotor branches. Despite the connection via the lumbosacral trunk, the two plexuses exist as separate bundles anatomically. The lumbar plexus arises from primary branches of the anterior roots of spinal nerves L1-L4. It lies superior to the pelvic rim and passes through the psoas muscle.

Arising from the L1 and L2 roots of the plexus are the iliohypogastric, ilioinguinal, and genitofemoral nerves. The lateral femoral cutaneous nerve receives a contribution from L2 and L3, while the femoral and obturator nerves both branch from L3 and L4.

  • The nerves originating from L1 and L2 innervate the transverse abdominal and anterior internal oblique muscles and provide sensory innervation to that same region, in addition to the sex organs.
  • Meanwhile, the nerves of L3 and L4 are responsible for generating flexion and adduction of the thigh and leg extension.

These nerves also provide cutaneous sensory innervation to the thigh and medial leg. Preganglionic sympathetic fibers originating in the lateral horn of the spinal cord’s gray matter are also located at spinal levels L1 and L2. The main branches of the sacral plexus originate below the pelvic rim and are housed in the pelvic girdle.

  1. It includes the superior gluteal nerve (L4-S1), the inferior gluteal nerve (L4-S1), the posterior femoral cutaneous nerve (S1-S3), and the sciatic nerve (L4-S3).
  2. The sciatic nerve is unique in that can be discretely mapped into its tibial (L4-S2) and common peroneal (L4-S1) branches.
  3. The pudendal nerve may also branch from the common sciatic nerve.

The gluteal and common sciatic nerves are responsible for motor innervation of the gluteal region and posterior thigh to generate movement of the hip in all directions as well as flexion of the knee. The tibial and common peroneal nerves also dictate all motor innervation of the leg, ankle, foot, and toes.

  1. These two nerves also provide sensory innervation of the posterolateral half of the leg and the foot.
  2. The posterior femoral cutaneous nerve is solely responsible for gluteal and perineal sensory innervation.
  3. It is also important to specify that preganglionic parasympathetic fibers originating in the sacral region are between S2 and S4.

Brain and spinal cord formation arise during the embryonic process of neurulation. During the fourth week of development, the neural plate, which arises from neural ectoderm, thickens, and folds along the dorsal midline. After folding, the neural tube then undergoes sequential differentiation, organization, and then closure in an extremely complex and regulated process to complete the primary neural tube, much of which is regulated by the notochord.

The neural tube eventually develops into the primitive central nervous system, separating into its ventral and dorsal components. Meanwhile, neurons in the peripheral nervous system arise from neural crest cells after undergoing epithelial to mesenchymal transitioning. Motoneurons being among the first fibers of the peripheral system to develop.

The dermatomes and myotomes, which receive innervation from individual spinal nerves, develop segmentally from somites. Somites develop from the paraxial mesoderm. The spinal cord receives both longitudinal and segmental blood supply. The vasculature is highly complex and anastomotic, which ensures adequate delivery to the entire structure.

Longitudinally, the anterior spinal artery (ASA) and a pair of posterior spinal arteries (PSAs) are the predominant supply of the spinal cord. The three arteries branch from the distal vertebral arteries at the base of the skull. The three vessels connect circumferentially around the cord as the vaso-corona to supply the entire periphery of the cord.

Numerous radicular arteries are also arranged segmentally, which provide additional blood flow to the entire vertebral column. Many of these are branches of segmental intercostal and lumbar arteries. There is ample documentation regarding anatomic variations of peripheral and spinal nerves in the medical literature.

Most common variants involve motor neural plexuses, where roots from multiple spinal nerves coalesce into trunks with numerous branches and outflow tracts. Anomalies in the brachial and lumbosacral plexuses often present as bifurcations, early splits, or complete absences of minor branches. These differences become particularly important in cases that require the use of a local anesthetic.

Several clinical considerations apply to spinal nerve anatomy. As previously mentioned, nerves exiting the cervical spine course horizontally from the spinal cord, exiting the intervertebral foramen. On the other hand, since the spinal cord usually extends caudally to the level of the L1 or L2 vertebral levels, the more caudal nerve roots travel in a somewhat vertical fashion caudally until exiting at their respective intervertebral foramen.

For this reason, In the cervical spine, any type of disc herniation would result in symptoms and or neurologic deficits at the nerve root exiting at that specific level. For example, a C5-C6 right-sided disc herniation would cause symptoms and or neurologic deficits in the C6 distribution regardless of the disc herniation being far lateral or paracentral.

In contrast, in the lumbar spine, the involved nerve root would depend on the type of disc herniation. Far lateral disc herniations will present symptoms in the distribution of the exiting nerve root, whereas a paracentral disc herniation would present symptoms in the distribution of the traversing nerve root at that level.

  • For example, a far lateral disc herniation at the level of L4-L5 would present symptoms in an L4 distribution, whereas a paracentral disc herniation would present symptoms in an L5 distribution.
  • Spinal nerves own a vital role in medicine, operating as the relay axons between the central and peripheral nervous systems.

They play a role in a full degree of clinical practice. Cutaneous innervation of the periphery maps into dermatomes, which are areas of skin supplied by nerves arising from a single spinal root. Understanding the topographical distribution is central to the diagnosis of a wide range of pathology.

Herpes zoster, a reactivation of the varicella-zoster virus within the dorsal root ganglion of a spinal nerve, presents as a prominent and painful red rash within a specific dermatome. Meanwhile, peripheral radiculopathy is more readily diagnosed if the affected nerve, and its subsequent spinal contributions, can be identified.

Similarly, myotomes are the motor equivalent of dermatomes. The myotome refers to the group of skeletal muscles that a single spinal nerve innervates. While dermatomal distribution exhibits discreet separation by spinal nerves, there is a notable amount of overlap in motor innervation.

  • Most prominent peripheral nerves originate from multiple spinal roots, some of which may arise from an adjacent but separate spinal region.
  • Similarly, individual muscles often share multiple sources of spinal nerve innervation.
  • Thus, myotomes are instead grouped by musculature action rather than strictly by anatomical location.

Applying this concept in the clinical setting, motor deficits of a specific action in many muscles can help identify the presence of neurological motor deficit.

What has 12 pairs of nerves?

Test Your Cranial Nerves

Cranial Nerves


The cranial nerves are 12 pairs of nerves that can be seen on the ventral (bottom) surface of the brain. Some of these nerves bring information from the sense organs to the brain; other cranial nerves control muscles; other cranial nerves are connected to glands or internal organs such as the heart and lungs.


Cranial Nerves Number Name Function Location I Olfactory Nerve Smell II Optic Nerve Vision III Oculomotor Nerve Eye movement; pupil constriction IV Trochlear Nerve Eye movement V Trigeminal Nerve Somatosensory information (touch, pain) from the face and head; muscles for chewing. VI Abducens Nerve Eye movement VII Facial Nerve Taste (anterior 2/3 of tongue); somatosensory information from ear; controls muscles used in facial expression. VIII Vestibulocochlear Nerve Hearing; balance IX Glossopharyngeal Nerve Taste (posterior 1/3 of tongue); Somatosensory information from tongue, tonsil, pharynx; controls some muscles used in swallowing. X Nerve Sensory, motor and autonomic functions of viscera (glands, digestion, heart rate) XI Spinal Accessory Nerve Controls muscles used in head movement. XII Hypoglossal Nerve Controls muscles of tongue Note: the olfactory “nerve” is composed of the rootlets of olfactory hair cells in the nasal mucosa and is not visible on the ventral surface of the brain. The rootlets end in the olfactory bulb. The olfactory tract contains nerve fibers projecting out of the olfactory bulb to the brain. The images in this table have been adapted from those in the Slice of Life project.


Can’t remember the names of the cranial nerves? Here is a handy-dandy mnemonic for you:

  • O n O ld O lympus T owering T op A F amous V ocal G erman V iewed S ome H ops.
  • The bold letters stand for:
  • olfactory, optic, oculomotor, trochlear, trigeminal, abducens, facial, vestibulocochlear, glossopharyngeal, vagus, spinal accessory, hypoglossal.

Still can’t remember the cranial nerves? Perhaps you need some to help you study! After you print the bookmarks, cut them into three individual bookmarks and use them to mark your place when you study.


Now that you know the names and functions of the cranial nerves, let’s test them. These tests will help you understand how the cranial nerves work. These tests are not meant to be a “clinical examination” of the cranial nerves. You will need to get a partner to help.both of you can serve as the experimenter (tester) and the subject. Record your observations of what your partner does and says. Olfactory Nerve (I) Gather some items with distinctive smells (for example, cloves, lemon, chocolate or coffee). Have your partner smell the items one at a time with each nostril. Have your partner record what the item is and the strength of the odor. Now you be the one who smells the items.have your partner use different smells for you. Optic Nerve (II) Make an eye chart (a “Snellen Chart”) like the one on the right. It doesn’t have to be perfect. Have your partner try to read the lines at various distances away from the chart. Oculomotor Nerve (III), Trochlear Nerve (IV) and Abducens Nerve (VI) These three nerves control eye movement and pupil diameter. Hold up a finger in front of your partner. Tell your partner to hold his or her head still and to follow your finger, then move your finger up and down, right and left. Do your partner’s eyes follow your fingers? Check the pupillary response (oculomotor nerve): look at the diameter of your partner’s eyes in dim light and also in bright light. Check for differences in the sizes of the right and left pupils. Trigeminal Nerve (V) The trigeminal nerve has both sensory and motor functions. To test the motor part of the nerve, tell your partner to close his or her jaws as if he or she was biting down on a piece of gum. To test the sensory part of the trigeminal nerve, lightly touch various parts of your partner’s face with piece of cotton or a blunt object. Be careful not to touch your partner’s eyes. Although much of the mouth and teeth are innervated by the trigeminal nerve, don’t put anything into your subject’s mouth. Facial Nerve (VII) The motor part of the facial nerve can be tested by asking your partner to smile or frown or make funny faces. The sensory part of the facial nerve is responsible for taste on the front part of the tongue. You could try a few drops of sweet or salty water on this part of the tongue and see if your partner can taste it. Vestibulocochlear Nerve (VIII) Although the vestibulocochlear nerve is responsible for hearing and balance, we will only test the hearing portion of the nerve here. Have your partner close his or her eyes and determine the distance at which he or she can hear the ticking of a clock or stopwatch. Glossopharyngeal Nerve (IX) and Vagus Nerve (X) Have your partner drink some water and observe the swallowing reflex. Also the glossopharyngeal nerve is responsible for taste on the back part of the tongue. You could try a few drops of salty (or sugar) water on this part of the tongue and see if your partner can taste it. Spinal Accessory Nerve (XI) To test the strength of the muscles used in head movement, put your hands on the sides of your partner’s head. Tell your partner to move his or her head from side to side. Apply only light pressure when the head is moved. Hypoglossal Nerve (XII) Have your partner stick out his or her tongue and move it side to side.

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Test Your Cranial Nerves

What part of body has most nerves?

Home Neurology Question & Answers

Doctor Answer is medically reviewed by SecondMedic medical review team. Answered by Seconmedic Expert The part of the body that has the most nerve endings is probably the fingertips. Each fingertip contains approximately 3,000 nerve endings called Meissner’s corpuscles, which are designed to detect light touch and vibration.

  • This means that touching your fingertips to something allows you to feel a sensation much more intensely than other parts of your body.
  • Furthermore, these tactile receptors become active when you’re playing an instrument or typing on a keyboard as they help us sense changes in pressure and motion.
  • However, even though fingertips have the highest concentration of nerve endings per square inch, other areas like lips, tongue and genitals also contain unique types of nerves responsible for providing different sensory experiences- like taste in our mouths or sexual pleasure from our genitalia.

Additionally, new research suggests that even hair follicles can have small nerve networks connected to them due to their ability to respond quickly to physical signals such as wind speed or temperature changes before other receptors could register them.

So, even though fingertips are equipped with some of the highest concentrations of nerve endings on our bodies (upwards from 3000), there still exist plenty more complex networks around us providing valuable information about what’s going on both inside and outside our bodies at a given time! Looking for expert medical advice and care can be a daunting task, especially when you need it urgently.

But with Second Medic, you can connect with the best doctors in just a few minutes and have a private care conversation with them, all for free! Our platform is designed to make it easy for you to get the medical advice and care you need without any hassle.

Whether you have a minor health concern or a serious medical condition, our team of experienced doctors are here to help. At Second Medic, we understand the importance of timely and reliable medical advice. That’s why we’ve made it our mission to provide you with the best possible care, at the convenience of your own home.

Our platform is easy to use, and you can connect with a doctor in just a few simple steps. All you need to do is create an account, tell us about your health concern, and we’ll match you with a doctor who has the expertise to help you. You can then have a private care conversation with your doctor, where you can discuss your symptoms, medical history, and any other concerns you may have.

What’s the longest nerve in the body?

The sciatic nerve is the longest, largest nerve in your body. Your sciatic nerve roots start in your lower back and run down the back of each leg. Sciatica is the pain or discomfort if your sciatic nerve gets compressed or pinched. People who are pregnant, have a sedentary lifestyle or have diabetes have a higher risk of sciatica.

Overview Function Anatomy Conditions and Disorders Care

Sciatic Nerve

Overview Function Anatomy Conditions and Disorders Care Back To Top

What is the most important nerve in your body?

Spinal Nerves – The spinal cord is part of your central nervous system. It begins at the bottom of the brain stem and continues down to your lower back. There are 31 pairs of spinal nerves, and they control sensory, motor, and other functions of your body.

  • C1-C8: Cervical nerves
  • T1-T12: Thoracic nerves
  • L1-L5: Lumbar nerves
  • S1-S5: Sacral nerves
  • One pair of coccygeal nerves

Source: Functional Control Each group of spinal nerves is involved with movements in certain parts of your body, including your hands, fingers, arms, upper back, hips, and abdominal muscles. Some spinal nerves are even responsible for ensuring you can walk and run properly.

  • For more detail on spinal nerves’ functional ability, refer to the chart below.
  • Automatic Control
  • Some nerves in the spinal cord are responsible for controlling automatic body functions, such as your heart rate, breathing, and other things your body does automatically.
  • For example, spinal nerves T1-L5, which are your thoracic and lumbar nerves, are partially responsible for controlling the functions of your:
  • Heart
  • Lungs
  • Gastrointestinal system
  • Kidneys
  • Sweat glands

The upper part of your sacral nerves, from L5-S3, are responsible for controlling bladder and bowel movements. At Northeast Spine and Sports Medicine, we help our patients feel more comfortable in their everyday lives by addressing problems they might experience with nerves in their brain or spinal cord.

What nerve is number 7?

Introduction – The facial nerve is the seventh cranial nerve (CN VII). It arises from the brain stem and extends posteriorly to the abducens nerve and anteriorly to the vestibulocochlear nerve. It courses through the facial canal in the temporal bone and exits through the stylomastoid foramen after which it divides into terminal branches at the posterior edge of the parotid gland.

What are the 5 6 7 8 nerves?

12 cranial nerves list

Cranial nerve 1 Olfactory nerve (CN I) – sensory
Cranial nerve 5 Trigeminal nerve (CN V) – mixed
Cranial nerve 6 Abducens nerve (CN VI) – motor
Cranial nerve 7 Facial nerve (CN VII) – mixed
Cranial nerve 8 Vestibulocochlear nerve (CN VIII) – sensory

What nerves are rule of 4?

Gates’ rule of 4 of the brainstem: A simple method to demystify the brainstem According to Gates’ rule of 4, there are 4 structures in the midline of the brainstem beginning with M: motor pathway or cortical spinal tract, motor cranial nerves (3, 4, 6 and 12), medial lemniscus, and medial longitudinal fasciculus.

There are 4 lateral structures beginning with “S” including the spinocerebellar pathways, sympathetic pathway, spinothalamic pathways and sensory nucleus of trigeminal nerve. There are 4 cranial nerves above the pons (1-4), 4 in the pons (5-8), and 4 in the medulla. Knowledge of the rule of 4 makes the teaching and diagnosis of brainstem syndromes less challenging.

References 1. Gates P. The rule of 4 of the brainstem: a simplified method for understanding brainstem anatomy and brainstem vascular syndromes for the non-neurologist. Intern Med J.2005; 35: 263-266. Submitted by Tissa Wijeratne Dr. Wijeratne reports no disclosures.

Can nerves grow again?

Three types of peripheral nervous system injuries are: –

Neuropraxia This is the mildest and most common type of nerve injury. The nerve itself is intact and merely stunned. Any resulting numbness, weakness or loss of function is temporary, and most people make nearly a complete recovery with rest and time. Surgery is rarely needed. Axonotmesis This is a partial nerve injury. The outer nerve sheath is intact, but the neurons within are damaged. Nerve cells can regenerate and grow back at a rate of about an inch a month, but recovery is typically incomplete and slow. Neurotmesis This is a complete nerve injury, where the nerve sheath and underlying neurons are severed. If there is an open cut, a neurosurgeon can see the cut nerve ends at surgery and repair this. If the gap is less than 2 centimeters, the nerve ends may be sutured together, provided they come together easily. Larger gaps may need artificial conduits or nerve grafts to fill the defect. Surgery is almost always needed.

Stretch injuries are the most encountered pattern of nerve damage. These may result from a fall, a birth injury, a motor vehicle accident, a surgical procedure or workplace injury. All three types of nerve injuries detailed above also can occur or in combination with one another.

Most people improve within three to six months, but surgery may be needed based on the lack of clinical improvement and other tests, including an ultrasound and electromyography. The chance of nerve regeneration is greater within the peripheral nervous system. This is because these neurons have a different lining, or sheath, made up of Schwann cells.

The central nervous system does not have these cells. Schwann cells can help damaged nerves regenerate and restore function. On average, damaged nerves can grow back at a rate of about 1 inch per month or 1 millimeter per day. Surgery is needed if there is significant scar tissue or a gap between cut nerve ends.

  1. Neurolysis is a surgical procedure that removes scar tissue from around and sometimes from within the nerve to improve its function.
  2. Direct nerve repair or primary neurorrhaphy involves suturing cut nerve ends together with ultrafine sutures or glue.
  3. Nerve grafting repairs larger gaps that are bridged with nerves harvested typically from the patient’s leg, cadaver nerves or synthetic conduits that may be lined with biological factors to enhance nerve regeneration.

Neurotization or nerve transfers involve sacrificing a healthy nerve by severing it and using it as a source of neurons to hot-wire a more important damaged nerve close to its entry into the paralyzed muscle. This bypasses scarring at the level of injury and reduces the time taken to reenergize the muscle.

Can nerves fully recover?

Treatment – If a nerve is injured but not cut, the injury is more likely to heal. Injuries in which the nerve has been completely severed are very difficult to treat, and recovery may not be possible. Your doctor will determine your treatment based on the extent and cause of your injury and how well the nerve is healing.

If your nerve is healing properly, you may not need surgery. You may need to rest the affected area until it’s healed. Nerves recover slowly, and maximal recovery may take many months or several years. You’ll need regular checkups to make sure your recovery stays on track. If your injury is caused by a medical condition, your doctor will treat the underlying condition. Depending on the type and severity of your nerve injury, you may need medications such as aspirin or ibuprofen (Advil, Motrin IB, others) to relieve your pain. Medications used to treat depression, seizures or insomnia may be used to relieve nerve pain. In some cases, you may need corticosteroid injections for pain relief. Your doctor may recommend physical therapy to prevent stiffness and restore function.

Can you feel nerves grow back?

How do I know the nerve is recovering? – As your nerve recovers, the area the nerve supplies may feel quite unpleasant and tingly. This may be accompanied by an electric shock sensation at the level of the growing nerve fibres; the location of this sensation should move as the nerve heals and grows. Over time, these feelings subside and the area should begin to feel more normal.

Are there 31 or 33 spinal nerves?

The spinal cord is an extension of the central nervous system (CNS), which consists of the brain and spinal cord. The spinal cord begins at the bottom of the brain stem (at the area called the medulla oblongata) and ends in the lower back, as it tapers to form a cone called the conus medullaris,

Anatomically, the spinal cord runs from the top of the highest neck bone (the C1 vertebra) to approximately the level of the L1 vertebra, which is the highest bone of the lower back and is found just below the rib cage. The spinal cord is about 18 inches (45 centimeters) in length and is relatively cylindrical in shape.

The cervical (neck) and lumbar (lower back) segments house the spinal cord’s two areas of enlargement. A fibrous band called the filum terminale begins at the tip of the conus medullaris and extends to the pelvis. At the bottom of the spinal cord (conus medullaris) is the cauda equina, a collection of nerves that derives its name from the Latin translation of “horse’s tail” (early anatomists thought the collection of nerves resembled a horse’s tail).

Cerebrospinal fluid (CSF) surrounds the spinal cord, which is also shielded by three protective layers called the meninges (dura, arachnoid and pia mater). The spinal cord lies inside the spinal column, which is made up of 33 bones called vertebrae, Five vertebrae are fused together to form the sacrum (part of the pelvis), and four small vertebrae are fused together to form the coccyx (tailbone).

The spine itself is divided into four sections, not including the tailbone:

Cervical vertebrae (C1-C7): located in the neck Thoracic vertebrae (T1-T12): located in the upper back and attached to the ribcage Lumbar vertebrae (L1-L5): located in the lower back Sacral vertebrae (S1-S5): located in the pelvis

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Between the vertebral bodies (except cervical vertebrae 1 and 2) are discs serving as a supportive structure for the spine. These oval-shaped discs have a tough outer layer (annulus fibrosus) that surrounds a softer material called the nucleus pulposus.

These discs act as shock absorbers for the spinal bones. Ligaments attached to the vertebrae also serve as supportive structures. There are 31 pairs of spinal nerves and roots, Eight pairs of cervical nerves exit the cervical cord at each vertebral level. One member of the pair exits on the right side and the other exits on the left.

The first cervical root exits above the C1 vertebra. The second cervical root exits between the C1-C2 segment and the remaining roots exit just below the correspondingly numbered vertebra. The eighth nerve root exits between the C7 and T1 vertebra. There are 12 thoracic nerve pairs.

The first nerve root exits between the T1 and T2 vertebrae. There are five lumbar nerve pairs. The first of these nerve roots exits between L1 and L2. There are five sacral nerve pairs. The first nerve root exits between S1 and S2. One pair of coccygeal (Co1) nerves meets in the area of the tailbone. By way of the peripheral nervous system (PNS), nerve impulses travel to and from the brain through the spinal cord to a specific location in the body.

The PNS is a complex system of nerves that branch off from the spinal nerve roots. These nerves travel outside of the spinal canal to the upper extremities (arms, hands and fingers), to the muscles of the trunk, to the upper and lower extremities (arms, hands, fingers, legs, feet and toes) and to the organs of the body.

Any interruption of spinal cord function by disease or injury at a particular level may result in a loss of sensation and motor function below that level. Depending on the severity of the disease or injury, the loss of function may be permanent. Annulus fibrosus – The fibrous, ring-like outer portion of an intervertebral disc.

Anterior – Referring to the front of the body or given structure. Anterolateral – Situated or occurring in front of and to the side. Arachnoiditis – Inflammation of the arachnoid membrane (the middle of the three protective layers called the meninges); most commonly seen around the spinal cord and cauda equina.

  1. Arthritis – Inflammation of a joint, usually accompanied by swelling, pain and restriction of motion.
  2. Bone spur – Bony growth or rough edge of bone.
  3. Cauda equina – The collection of nerves at the end of the spinal cord that resembles a horse’s tail.
  4. Cervical spine – The neck region of the spine consisting of the first seven vertebrae.

Coccyx – More commonly known as the tailbone, this is a bony structure in the region of the spine below the sacrum. Conus medullaris – The cone-shaped bottom of the spinal cord, usually at the level of L1. Disc (Intervertebral) – A tough, elastic cushion located between the vertebrae in the spinal column; acts as a shock absorber for the vertebrae.

  1. Disc degeneration – The deterioration of a disc.
  2. A disc in the spine may wear out over time.
  3. A deteriorated disc may or may not cause pain.
  4. Distal – Located downstream.
  5. Facet – A joint formed when a posterior structure of a vertebra that joins with a facet of an adjacent vertebra; this joint allows for motion in the spinal column.

Each vertebra has a right and left superior (upper) facet and a right and left inferior (lower) facet. Foramen – An opening in the vertebrae of the spine through which the spinal nerve roots travel. Herniated disc – Condition in which the jelly-like core material of a disc bulges or ruptures out of its normal position; a herniated disc may exert pressure on the surrounding nerve root and/or the spinal cord.

Joint – The junction of two or more bones that permits varying degrees of motion between the bones. Lamina – The flattened or arched part of the vertebral arch that forms the roof or back part of the spinal canal. Lateral – Situated on the side or away from the midline of the body. Ligament – Fibrous connective tissue that links bones together at joints or that passes between bones of the spine.

Lumbar spine – The lower back region of the spine; consists of the five vertebrae between the ribs and the pelvis. Nerves – Neural tissue that conducts electrical impulses (messages) from the brain and spinal cord to all other parts of the body; also conveys sensory information from the body to the central nervous system.

  1. Nerve root – The initial portion of a spinal nerve as it originates from the spinal cord.
  2. Neural arch – The bony arch of the back part of a vertebra that surrounds the spinal cord; also referred to as the vertebral arch, it consists of the spinous process and lamina.
  3. Pedicle – The bony part of each side of the neural arch of a vertebra that connects the lamina (back part) with the vertebral body (front part).

Posterior – The back or rear side of the body or a given structure. Proximal – Located upstream. Rotation – Twisting movement of one vertebra on another as a patient turns from one side to the other. Sacrum – Part of the pelvis just above the coccyx (tailbone) and below the lumbar spine (lower back).

Sacrum – Part of the pelvis just above the coccyx (tailbone) and below the lumbar spine (lower back). Sciatica – A lay term indicating pain along the course of the sciatic nerve; typically noted in the back of the buttocks and running down the back of the leg and thigh to below the knee. Scoliosis – An abnormal sideways curvature of the spine.

Spinal canal – A bony channel located in the vertebral column that protects the spinal cord and nerve roots. Spinal cord – The longitudinal cord of nerve tissue enclosed in the spinal canal. It serves not only as a pathway for nerve impulses to and from the brain, but also as a center for operating and coordinating reflex actions independent of the brain.

  • Spinal stenosis – Abnormal narrowing of the vertebral column that may result in pressure on the spinal cord, spinal sac or nerve roots stemming from the spinal cord.
  • Spine – The flexible bone column extending from the base of the skull to the tailbone.
  • It is made of 33 bones known as vertebrae, and is referred to as the vertebral column, spinal column or backbone.

Spondylitis – Inflammation of vertebrae. Spondylolisthesis – The forward displacement or “slippage” of one vertebra onto another. Spondylosis – Degenerative bony changes in the spine, usually most marked at the vertebral joints and intervertebral discs.

  1. Superior – Situated above or directed upward toward the head of an individual.
  2. Thoracic spine – The region of the spine attached to the ribcage; located between the cervical and lumbar areas, it consists of 12 vertebrae.
  3. Vertebrae – The 33 bones that make up the spine, individually referred to as a vertebra.

They are divided into the cervical spine (neck), the thoracic spine (upper back or rib cage), the lumbar spine (lower back) and the sacral spine (pelvis or base of the spine). Disclaimer The AANS does not endorse any treatments, procedures, products or physicians referenced in these patient fact sheets.

Are there 62 spinal nerves?

There are 31 pairs of spinal nerves (62 total). The following discussion traces a spinal nerve as it emerges from the spinal column: A spinal nerve emerges at two points from the spinal cord, the ventral and dorsal roots.

The ventral and dorsal roots merge to form the whole spinal nerve. The spinal nerve emerges from the spinal column through an opening (intervertebral foramen) between adjacent vertebrae. This is true for all spinal nerves except for the first spinal nerve (pair), which emerges between the occipital bone and the atlas (the first vertebra). Outside the vertebral column, the nerve divides into the following branches:

The dorsal ramus contains nerves that serve the dorsal portions of the trunk. The ventral ramus contains nerves that serve the remaining ventral parts of the trunk and the upper and lower limbs. The meningeal branch reenters the vertebral column and serves the meninges and blood vessels within. The rami communicantes contain autonomic nerves that serve visceral functions.

Some ventral rami merge with adjacent ventral rami to form a plexus, a network of interconnecting nerves. Nerves emerging from a plexus contain fibers from various spinal nerves, which are then carried together to some target location.

An area of the skin that receives sensory stimuli that pass through a single spinal nerve is called a dermatome. Dermatomes are illustrated on a human figure with lines that mark the boundaries of the area where each spinal nerve receives stimuli.

How big is a human nerve?

The Hows – How big is the brain? How much does the brain weigh? The adult human brain weighs between 1300 g and 1400 g (approximately 3 lbs). A newborn human brain weighs between 350 and 400 g. For comparison: elephant brain = 6,000 g chimpanzee brain = 420 g rhesus monkey brain = 95 g beagle dog brain = 72 g cat brain = 30 g rat brain = 2 g More Brain Weights How many neurons (nerve cells) are in the brain? How big are they? There are approximately 86 billion (86,000,000,000) neurons in the human brain. To get an idea of how small a neuron is, let’s do some math: The dot on top of this “i” is approximately 0.5 mm (500 microns or 0.02 in) in diameter. How long is a neuron? Some neurons are very short.less than a millimeter in length. Some neurons are very long.a meter or more! The axon of a motor neuron in the spinal cord that innervates a muscle in the foot can be about 1 meter (3 feet) in length. Think about how long the axon of a motor neuron would be if you wanted to make a model of it. The cell body of a motor neuron is approximately 100 microns (0.1 millimeter) in diameter and as you now know, the axon is about 1 meter (1,000 millimeter) in length. How big is the brain compared to the rest of the body? If you assume the average person is 150 pounds and the average brain weighs 3 lbs., then the brain is 2% of the total body weight. How long is the spinal cord and how much does it weigh? The average spinal cord is 45 cm long in men and 43 cm long in women. The spinal cord weighs approximately 35 g. How fast does information travel in the nervous system? Information travels at different speeds within different types of neurons. Transmission can be as slow as 0.5 meters/sec or as fast as 120 meters/sec. Traveling at 120 meters/sec is the same as going 268 miles/hr!!! Check the math out yourself. More about the speed of signals in the nervous system,

What nerve controls eyesight?

Summary – The optic nerve is a bundle of more than 1 million nerve fibers that carry visual messages. You have one connecting the back of each eye (your retina ) to your brain. Damage to an optic nerve can cause vision loss, The type of vision loss and how severe it is depends on where the damage occurs.

Glaucoma is a group of diseases that are the leading cause of blindness in the United States. Glaucoma usually happens when the fluid pressure inside the eyes slowly rises and damages the optic nerve. Optic neuritis is an inflammation of the optic nerve. Causes include infections and immune-related illnesses such as multiple sclerosis, Sometimes the cause is unknown. Optic nerve atrophy is damage to the optic nerve. Causes include poor blood flow to the eye, disease, trauma, or exposure to toxic substances. Optic nerve head drusen are pockets of protein and calcium salts that build up in the optic nerve over time

Contact your health care provider if you are having vision problems. Tests for optic nerve disorders may include eye exams, ophthalmoscopy (an examination of the back of your eye), and imaging tests, Treatment depends on which disorder that you have. With some optic nerve disorders, you may get your vision back.

What is the 12th nerve called?

Introduction – The Hypoglossal Nerve is the 12th Cranial Nerve (Cranial Nerve XII). It is mainly an efferent nerve for the tongue musculature. The nerve originates from the medulla and travels caudally and dorsally to the tongue.

What is the name of 12 nerve?

Introduction – The Hypoglossal Nerve is the 12th Cranial Nerve (Cranial Nerve XII). It is mainly an efferent nerve for the tongue musculature. The nerve originates from the medulla and travels caudally and dorsally to the tongue.

What are the 12 31 nerves?

In humans 12 pairs, the cranial nerves, are attached to the brain, and, as a rule, 31 pairs, the spinal nerves, are attached to the spinal cord.