what carries nerve impulses to muscles or glands

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The peripheral nervous system refers to the parts of the nervous organization that are exterior the key nervous system, that is, those exterior the brain and spinal cord.

Thus, the peripheral nervous system includes

• The nerves that connect the spinal cord to the rest of the body, including the 31 pairs of spinal nerves

• More than 100 billion nervus cells that run throughout the body

Using the Encephalon to Move a Muscle

Moving a musculus usually involves communication betwixt the muscle and the brain through fretfulness. The impetus to movement a muscle may originate in the brain, as when a person consciously decides to move a musculus—for example, to pick up a volume. Or the impetus to motility a muscle may originate with the senses. For example, special nervus endings in the skin (sensory receptors) enable people to sense pain or a change in temperature. This sensory information is sent to the encephalon, and the encephalon may send a bulletin to the muscle nearly how to respond. This type of exchange involves two complex nerve pathways: The sensory nervus pathway to the brain The motor nerve pathway to the musculus
	If sensory receptors in the skin detect pain or a change in temperature, they transmit an impulse (signal), which ultimately reaches the brain. The impulse travels forth a sensory nerve to the spinal string. The impulse crosses a synapse (the junction between two nerve cells) between the sensory nerve and a nervus cell in the spinal string. The impulse crosses from the nerve cell in the spinal cord to the opposite side of the spinal string. The impulse is sent upwardly the spinal cord and through the brain stem to the thalamus, which is a processing eye for sensory data, located deep in the brain. The impulse crosses a synapse in the thalamus to nerve fibers that comport the impulse to the sensory cortex of the cerebrum (the area that receives and interprets data from sensory receptors). The sensory cortex perceives the impulse. A person may then decide to initiate motility, which triggers the motor cortex (the area that plans, controls, and executes voluntary movements) to generate an impulse. The nerve carrying the impulse crosses to the opposite side at the base of the brain. The impulse is sent down the spinal cord. The impulse crosses a synapse between the nerve fibers in the spinal cord and a motor nerve, which is located in the spinal string. The impulse travels out of the spinal string along the length of the motor nerve. At the neuromuscular junction (where nerves connect to muscles), the impulse crosses from the motor nerve to receptors on the motor terminate plate of the musculus, where the impulse stimulates the muscle to motility.
If the awareness occurs suddenly and is severe (as when stepping on a sharp stone or picking up a cup of very hot java), the impulse may travel to the spinal cord and directly back to the motor nerve, bypassing the brain. The effect is a quick response of a musculus—by immediately withdrawing from whatever is causing the pain. This response is called a spinal reflex.

Dysfunction of peripheral nerves may issue from damage to any function of the nervus:

• Axon (the function that sends messages)

• Body of the nervus prison cell

• Myelin sheath (the membranes that surround the axon and that office much similar insulation around electrical wires, enabling nerve impulses to travel speedily)

Typical Structure of a Nervus Jail cell

A nervus cell (neuron) consists of a large jail cell body and nerve fibers—one elongated extension (axon) for sending impulses and unremarkably many branches (dendrites) for receiving impulses. The impulses from the axon cross a synapse (the junction betwixt two nervus cells) to the dendrite of another jail cell.

Each large axon is surrounded by oligodendrocytes in the brain and spinal cord and by Schwann cells in the peripheral nervous system. The membranes of these cells consist of a fat (lipoprotein) chosen myelin. The membranes are wrapped tightly around the axon, forming a multilayered sheath. This myelin sheath resembles insulation, such as that around an electric wire. Nervus impulses travel much faster in nerves with a myelin sheath than in those without one.

Insulating a Nerve Fiber

Nigh nerve fibers within and exterior the encephalon are wrapped with many layers of tissue composed of a fat (lipoprotein) called myelin. These layers form the myelin sheath. Much like the insulation around an electric wire, the myelin sheath enables nerve signals (electrical impulses) to be conducted forth the nerve fiber with speed and accuracy. When the myelin sheath is damaged (called demyelination), nerves do not conduct electrical impulses ordinarily.

Peripheral nerve disorders tin can bear on

If motor nerves (which control musculus movement) are damaged, muscles may weaken or become paralyzed. If sensory fretfulness (which carry sensory information—about such things equally pain, temperature, and vibration) are damaged, abnormal sensations may be felt or awareness may exist lost.

Peripheral nerve disorders tin can be hereditary or acquired (caused by exposure to toxins, injury, infections, or metabolic or inflammatory disorders).

Certain disorders crusade progressive deterioration of the nerve cells in the spinal cord and encephalon that control muscle motility (motor neuron diseases Amyotrophic Lateral Sclerosis (ALS) and Other Motor Neuron Diseases (MNDs) Motor neuron diseases are characterized by progressive deterioration of the nerve cells that initiate musculus movement. Every bit a result, the muscles stimulated by these nerves deteriorate, become... read more than ). Motor neuron diseases can resemble peripheral nervus disorders, which touch nerve cells outside the brain and spinal string.. Motor neuron diseases may be caused by viruses (such as the polio Polio Polio is a highly contagious, sometimes fatal enterovirus infection that affects nerves and can cause permanent muscle weakness, paralysis, and other symptoms. Polio is caused by a virus and... read more virus), exist inherited, or accept no clear known crusade (such every bit amyotrophic lateral sclerosis Amyotrophic Lateral Sclerosis (ALS) and Other Motor Neuron Diseases (MNDs) Motor neuron diseases are characterized by progressive deterioration of the nerve cells that initiate muscle movement. As a result, the muscles stimulated by these nerves deteriorate, become... read more ).

Novichok was developed in Russia and has been used in assassination attempts. Curare has been used to help relax muscles during surgery and to paralyze and kill when placed on the tip of poison darts.

Disorders that bear on muscle rather than nerves (as peripheral nervus disorders do) also cause muscle weakness. Musculus disorders may be categorized as

• Hereditary, such as Duchenne muscular dystrophy, Becker muscular dystrophy Duchenne Muscular Dystrophy and Becker Muscular Dystrophy Muscular dystrophies are a group of inherited muscle disorders in which 1 or more genes needed for normal muscle construction and function are defective, leading to muscle weakness of varying... read more , familial periodic paralysis Familial Periodic Paralysis Familial periodic paralysis is a rare inherited disorder that causes sudden attacks of weakness and paralysis. There are four different forms, which involve abnormalities in how electrolytes... read more , limb-girdle muscular dystrophy Limb-Girdle Dystrophy Limb-girdle dystrophy encompasses a group of muscular dystrophies that can exist inherited in various ways. The muscles of the shoulder or pelvis are affected. Muscular dystrophies are a group... read more than , myotonia congenita Myotonia Congenita Myotonia congenita is an inherited disorder that causes musculus stiffness and muscle enlargement. It affects what almost people think of equally musculus, the type that can be contracted to move the diverse... read more (Thomsen disease), and myotonic dystrophy Myotonic Dystrophy Myotonic dystrophy is a rare muscular dystrophy. This disorder affects the ability to relax the muscles at will. Myotonia refers to delayed relaxation afterward muscle wrinkle, which can cause... read more (Steinert illness)

Doctors do tests to determine whether the crusade of weakness is a muscle, a neuromuscular junction, or a nerve disorder.

• A doctor's evaluation

• Possibly electromyography and nerve conduction studies, imaging tests, or a biopsy

• For a suspected hereditary neuropathy, genetic testing

To diagnose a peripheral nerve disorder, doctors enquire people to draw their symptoms, including

• When the symptoms started

• Which symptoms appeared first

• How the symptoms have changed over time

• Which body parts are afflicted

• What relieves and what worsens the symptoms

Doctors besides ask about possible causes, such every bit whether people accept had any infections or other disorders, whether they may accept been exposed to toxins, and whether any family members accept had similar symptoms. This information gives doctors clues most the cause of symptoms.

What doctors find during the examination may suggest possible causes and the tests that need to be done.

Tests may include the following:

• Imaging tests to check for abnormalities (such as tumors) affecting the cranial nerves or the spinal string and to rule out other causes of the symptoms

• A biopsy of muscle and nerve to identify the blazon of trouble (such equally whether nerves are demyelinated or inflamed)

• Treatment of the cause when possible

• Symptom relief

• Perchance physical, occupational, and speech and language therapy

If a disorder is causing symptoms, it is treated if possible. Otherwise, doctors focus on relieving symptoms.

Care provided by a squad of several types of health care practitioners (a multidisciplinary team) can assist people cope with progressive disability. The team may include

• Physical therapists to help people continue to use their muscles

• Occupational therapists to recommend assistive devices that can help people do their daily activities (such as devices to aid with walking)

• Speech and language therapists to help people communicate

• Specialists to help with specific issues, such as difficulty swallowing or breathing

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