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Peripheral Nervous System
- 1. ARMIN PERPUSE, MD Internal Medicine (Adult Disease Specialist)
- 2. PERIPHERAL NERVOUS SYSTEM Nerves and ganglia outside the brain and spinal cord Collects & Relays information: o Ignored o Triggers a reflex o Reevaluate Motor Neurons: o Regulating activity in those structures
- 4. PERIPHERAL NERVOUS SYSTEM The nerves of the PNS can be divided into two groups: 12 pairs of CN 31 pairs of Spinal nerves
- 5. MIXED NERVES SENSORY + MOTOR Carry impulses TOWARDS THE CNS SENSORY or AFFERENT NERVES Carry ONLY MOTOR FIBERS MOTOR or EFFERENT NERVES
- 6. 12 pairs Designated by Roman numerals from I to XII
- 7. CRANIAL NERVE FUNCTION SENSORY MOTOR SPECIAL SENSES (vision) GENERAL SENSES (touch and pain in the face) SOMATIC MOTOR Innervates skeletal muscles in the neck and head PARASYMPATHETIC CN Innervates glands, smooth muscle throughout the body and cardiac muscle of heart
- 8. CN I (olfactory) CN II (optic) CN VIII (vestibulocochlear) SENSORY NERVES
- 9. INNERVATES THE EYE MUSCLES CN III (oculomotor) CN IV (trochlear) CN VI (abducens) INNERVATES THE TONGUE CN XI (accessory) CN XII (hypoglossal) MOTOR NERVES
- 10. CN V (trigeminal) CN VII (facial) CN IX (glossopharyngeal) CN X (vagus) MIXED NERVES
- 14. DIVISIONS OF THE NERVOUS SYSTEM
- 26. 1. SYMPATHETIC OR THORACOLUMBAR DIVISIONS OF THE AUTONOMIC NERVOUS SYSTEM arises from all the thoracic and the first three lumbar segments of the spinal cord. 2. PARASYMPATHETIC OR CRANIOSACRAL DIVISIONS OF THE AUTONOMIC NERVOUS SYSTEM arises from the third, seventh, ninth, and tenth cranial nerves and from the second, third, and fourth sacral segments of the spinal cord.
Editor's Notes
- PERIPHERAL NERVOUS SYSTEM Consists of all the nerves and ganglia outside the brain and spinal cord Collects information from numerous sources both inside and on the surface of the body and relays it by way of sensory neurons to CNS, where one of three results is possible: The information is ignored Triggers a reflex, or Is evaluated more extensively. Motor Neurons in the PNS relay information from the CNS to muscles and glands in various parts of the body, regulating activity in those structures. The nerves of the PNS can be divided into two groups: 12 pairs of CN 31 pairs of Spinal nerves
- NERVE is a bundle of neuron fibers found outside the CNS Each fibers is surrounded by a delicate connective tissue sheath an ENDONEURIUM. Group of fibers are bound by a courser connective tissue wrapping, the PERINEURIUM to form fiber bundles or FASCICLES. THEN FINALLY all fascicles are bound together by a tough fibrous sheath, the EPINEURIUM to form the cordlike NERVE
- The nerves of the PNS can be divided into two groups: 12 pairs of CN 31 pairs of Spinal nerves Like neurons, nerves are classified according to the direction in which they transmit impulses. Nerves carrying both sensory and motor are called MIXED Nerves - ALL SPINAL NERVES are MIXED NERVES Nerves that carry impulses towards the CNS only are called SENSORY or AFFERENT NREVES Whereas those that carry only motor fibers are MOTOR or EFFERENT nerves
- Like neurons, nerves are classified according to the direction in which they transmit impulses. Nerves carrying both sensory and motor are called MIXED Nerves - ALL SPINAL NERVES are MIXED NERVES Nerves that carry impulses towards the CNS only are called SENSORY or AFFERENT NREVES Whereas those that carry only motor fibers are MOTOR or EFFERENT nerves
- There are two general categories of CN function: SENSORY Functions – can be divided into the special senses, such as vision and the more general senses, such as touch and pain in the face. MOTOR Functions are subdivided into SOMATIC MOTOR & PARASYMPATHETIC SOMATIC MOTOR CN – innervate skeletal muscles in the head and neck PARASYMPATHETIC CN – innervates glands, smooth muscle throughout the body and cardiac muscle of the heart
- SENSORY carry impulses towards brain. Also called afferent fibers CN I (olfactory), carries impulses for the sense of smell (subject is asked to sniff and identify aromatic substances, such as oil of cloves or vanilla. CN II (optic), carries impulses for vision (vision and visual field are tested with an eye chart and by testing point at which the subject first sees an object (finger) moving into the visual field; eye interior is viewd with an ophthalmoscope. CN VIII (vestibulocochlear), transmits impulses for the sense of balance, cochlear branch transmits impulses for the sense of hearing (hearing I checked by air and bone conduction, using tuning fork)
- Carry impulses away from the brain. Also called efferent fibers. WHICH SUPPLY THE EYE MUSCLES. 1. CN III (oculomotor), supplies motor fibers to four of the six muscles (superior, inferior, and medial rectus, and inferior oblique)that direct the eyeball, to the eyelid; and to the internal eye muscles controlling lens shape and pupil size. TESTED: PUPILS are examined for size, shape, and size equality. PUPILLARY REFLEX is tested with a penlight (pupils should constrict when illuminated). EYE CONVERGENCE is tested, as in the ability to follow moving objects. 2. CN IV (trochlear), supplies motor fibers for one external eye muscle (superior oblique), TESTED IN COMMON with CN III for the ability to follow objects. 3. CN VI (abducens), supplies motor fibers to the lateral rectus muscle, which rolls the eye laterally. TESTED IN COMMON with CN III for the ability to move each eye laterally. WHICH INNERVATES THE TONGUE CN XI (accessory), mostly motor fibers that activates the SCM and Trapezius mascules TEST: SCM/Trapz muscles are checked for strenght rotate head. Shrug shoulders against resistance. CN XII (hypoglossal), motor fibers control tongue movements. TEST: stick out tongue
- carry both sensory and motor nerve fibers CN V (trigeminal), conducts SENSORY impulses from the skin of the face and mucosa of the nose and mouth, MOTOR fibers that activates the chewing muscles. TEST: SENSORY using pins, hot and cold objects. MOTOR open mouth against resistance and move jaw from side to side. CN VII (facial), MOTOR activates muscles of facial expression and lacrimal/salivary glands. SENSORY taste buds of anterior tongue. TEST: SENSORY: anterior 3rd of the tongue is tested for ability to taste sweet, salty, sour and bitter substances. MOTOR close eyes, smile, whistle, tearing test with ammonia fumes. CN IX (glossopharyngeal), MOTOR fibers to phargynx (throat) that promote swallowing and saliva production. SENSORY impulses from taste buds of the posterior tongue and from pressure receptors of the carotid artery. TEST: Gag and swollowing reflexes, speak and cough. SENSORY taste in posterior tongue CN X (vagus), the only pair of CN that extends to the thoracic and abdominal cavities. SENSORY impulses from and Motor impulses to the pharynx, larynx and the abdominal and thoracic viscera. MOST MOTOR fiber are PARASYMPATHETIC, that promote digestive activity and help regulate heart activity. TEST in common with CN IX, because serves both muscles of the throat.
- SPINAL NERVES Arise along the spinal cord from the union of dorsal roots and ventral roots MIXED Nerves. Most of the spinal nerves exit the vertebral column between adjacent vertebrae.
- SPINAL NERVES MIXED Nerves. Most of the spinal nerves exit the vertebral column between adjacent vertebrae.
- SPINAL NERVES 31 PAIRS Arise along the spinal cord from the union of dorsal roots and ventral roots MIXED Nerves. Most of the spinal nerves exit the vertebral column between adjacent vertebrae.
- SPINAL NERVES are categorized by the region of the vertebral column from which they merge. The nerves arising from each region of the spinal cord and column supply specific regions of the body. DERMATOME is the area of skin supplied with sensory innervation by a pair of spinal nerves. Each of the spinal nerves except C1 has a specific cutaneous sensory distribution.
- Most of the spinal nerves are organized into three major PLEXUSES, where neurons of several spinal nerves come together and intermingle. Major nerves of the neck and limbs are branches if these plexuses. SPINAL NERVES T2 through T11 do not join a plexus, instead these nerves extend around the thorax between the ribs, giving off branches to muscles and skin. So what are these plexuses?
- ORIGINATES from spinal nerves C1 to C4. Branches from this plexus innervates several of the muscles attached to the hyoid bone, as well as the skin of the neck and posterior portion of the head. One of the MOST IMPORTANT branches is PHRENIC nerve, which innervates the diaphragm. Contraction of the diaphragm is largely responsible for our ability to breathe.
- BRACHIAL PLEXUS originates from spinal nerves C5 to T1. Five major nerves emerge from the brachial plexus to supply the upper limb and shoulder. AXILLARY NERVES innervates two shoulder muscle and the skin over part of the shoulder. RADIAL NERVES innervates all the muscles of the posterior arm and forearm as well as the skin over the posterior surface of the arm, forarm and hand. MUSCULOCUTANEOUS innervtes the anterior muscles of the arm and the skin over the radial surface of the forearm. ULNAR NERVE innervates two anterior forearm muscles and most of the intrinsic hand muscles MEDIAN NERVE innervates most of the anterior forearm muscles and some of the intrinsic hand muscles.
- BRACHIAL PLEXUS originates from spinal nerves C5 to T1. Five major nerves emerge from the brachial plexus to supply the upper limb and shoulder. AXILLARY NERVES innervates two shoulder muscle and the skin over part of the shoulder. RADIAL NERVES innervates all the muscles of the posterior arm and forearm as well as the skin over the posterior surface of the arm, forarm and hand. MUSCULOCUTANEOUS innervtes the anterior muscles of the arm and the skin over the radial surface of the forearm. ULNAR NERVE innervates two anterior forearm muscles and most of the intrinsic hand muscles MEDIAN NERVE innervates most of the anterior forearm muscles and some of the intrinsic hand muscles.
- LUMBOSACRAL PLEXUS Originates from L1 to S4 FOUR MAJOR NERVES exit the plexus to supply the lower limb. OBTURATOR innervates the muscles of the medial thigh and the skin FEMORAL innervates the anterior thigh muscles and skin over the ant thigh and medial side of the leg. TIBIAL NERVE innervates the posterior thigh muscles, the ant and post leg muscles and most of the intrinsic foot muscles. COMMON FIBULAR innervates the musclesof the lateral thigh and leg and some intrinsic foot muscles.
- The autonomic nervous system may be divided, both functionally and structurally into sympathetic and parasympathetic nervous divisions. 1. Sympathetic or Thoracolumbar Divisions of the autonomic nervous system arises from all the thoracic and the first three lumbar segments of the spinal cord. 2.Parasympathetic or Craniosacral Divisions of the autonomic nervous system arises from the third, seventh, ninth, and tenth cranial nerves and from the second, third, and fourth sacral segments of the spinal cord.