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CHAPTER 13 PERIPHERAL NERVOUS SYSTEM Functional division of nervous system • sensory = afferent info to the CNS ascending spinal cord • motor = efferent info from CNS descending spinal cord somatic skin , muscles visceral organs • • Peripheral nervous system • • • nerves outside the CNS cranial nerves CNS = brain • sensory in to brain • motor out from brain spinal nerves CNS = spinal cord • sensory in to spinal cord • motor out from spinal cord PNS basic structure • # neurons between periphery and CNS: – – – – sensory receptor to spinal cord - 1 neuron motor spinal cord to muscle - 1 neuron ANS CNS to organ 2 neurons special senses varies • ganglia group of cell bodies outside CNS usually sensory • nuclei group of cell bodies within CNS motor location of receptors exteroceptors info from environment interoceptors info from organs, vessels proprioceptors info from joints , muscles • • • type of stimulus • mechanoreceptors mechanical force • chemoreceptors chemical or chemical change • thermoreceptors heat • photoreceptors light , color • nociceptors pain (chemical ?) structure of receptors • • free nerve endings – – pain, temperature, itch Merkel – specialized free ending for touch encapsulated nerve endings – – Meissner, Pacinian, Ruffini touch and pressure Proprioceptors kinesthetic sense • muscle spindles • Golgi tendon organ • joint position motor endings • • • • neuromuscular junction – – – axon terminal synapse motor end plate motor unit somatic skeletal muscle visceral smooth , cardiac muscle Cranial nerves • • • peripheral nerves to head and neck (CN X - to thorax and abdomen) motor cell bodies nuclei in brain sensory cell bodies cranial sensory ganglia special sense organs • axons pass through skull foramen • numbered I - XII Cranial nerves • • • • • • • • • • • • I Olfactory smell II Optic vision III Oculomotor eye movement IV Trochlear eye movement V Trigeminal face sensation VI Abducens eye movement VII Facial face movement VIII Vestibulocochlear hearing; equilibrium IX Glossopharyngeal taste,swallow, BP reflex X Vagus parasympathetic effects XI Accessory trapezius, SCM XII Hypoglossal tongue movement Cranial nerve I • • • • • CN I Olfactory nerve smell receptors in olfactory epithelium foramen ??? synapse in olfactory bulb olfactory tract Cranial nerve II • • • • • CN II optic nerve vision receptors = retina of the eye optic nerve through optic canal crossover at optic chiasma optic tract to occipital lobe Cranial nerves - eye movement • • • • • III Oculomotor 4 extrinsic eye muscles IV Trochlear superior oblique muscle VI Abducens lateral rectus muscle III Oculomotor pupil constriction (ANS) from midbrain (III and IV) or Pons (VI) through superior orbital fissure Cranial nerves - face • CN V Trigeminal sensory to face motor to masseter, temporalis, pterygoids • CN VII Facial motor to face sensory - taste salivary glands (ANS) lacrimal glands (ANS) CN V - face sensation • 3 divisions • face to Pons – – – ophthalmic maxillary mandibular V1 V2 V3 V1 supraorbital foramen ; superior orbital fissure V2 infraorbital foramen ; foramen rotundum V3 mental foramen ; foramen ovale CN VII - face movement • • CN VII Facial motor facial muscles 5 branches • sensory taste - anterior 2/3 of tongue chorda tympani • ANS parasympathetic to lacrimal glands and salivary glands (not parotid) • foramen internal acoustic meatus stylomastoid foramen cranial nerves - ear • CN VIII Vestibulocochlear • Cochlear nerve • • – – hearing receptors Cochlea to Medulla ; to auditory cortex ?? auditory reflex ?? Vestibular nerve – – balance , equilibrium receptors Vestibule to Medulla ; to cerebellum equilibrium reflex - Midbrain internal acoustic meatus Cranial nerve IX • • • • • • CN IX Glossopharyngeal = tongue and pharynx taste , swallow, saliva , BP sensory – – taste BP carotid sinus motor – stylopharyngeus ANS Parotid gland jugular foramen cranial nerve X • CN X • medulla through jugular foramen • • Vagus nerve Parasympathetic ANS – parasympathetic to most organs thorax and abdomen some motor for speech and swallowing • pharyngeal and laryngeal muscles cranial nerve – lower muscles • CN XI – – • Accessory motor to Trapezius muscle SCM jugular foramen CN XII – – Hypoglossal motor to muscles of tongue – _______glossus and suprahyoid group hypoglossal canal spinal nerves • joined spinal roots • spinal nerve • 31 spinal levels , bilateral – = joined spinal roots C1-8; T1-12; L1-5; S1-5; Coc1 spinal nerve - branches • rami : – – dorsal ramus to posterior trunk ventral to ventral trunk and limbs ramus • peripheral nerves • back branches of dorsal rami C1 – S5 • thorax branches of ventral rami T1 – T12 • named branches of rami peripheral nerves – trunk – intercostal nerves abdomen – branches of ventral rami T6 – T12 intercostal nerves nerve plexuses • a group of spinal nerves • each peripheral nerve has fibers from a few spinal nerves • • • • - ventral rami Cervical C1 - C4 to neck Brachial C5 – T1 to upper extremity Lumbar L1 – L4 to L/S and LE Sacral L4 – S4 to LE and perineum cervical plexus • • • • • • • C1 – C4 ventral rami sensory to skin of neck and occiput motor to anterior neck muscles lesser occipital n. greater auricular n. transverse cervical n. phrenic nerve C3 ,4, 5 diaphragm brachial plexus • C5 – T1 spinal nerves • branch into peripheral nerves to UE – – – – – musculocutaneous n. median n. ulnar n. axillary n. radial n. brachial plexus – peripheral nerves • musculocutaneous n. motor sensory • median n. motor sensory • ulnar n. motor sensory • radial n. motor sensory • axillary n. motor sensory lumbar plexus • • • L1 - L4 spinal nerves to : anterior thigh abdominal wall psoas muscle peripheral nerves : – – – femoral n. – saphenous n. obturator n. motor sensory ant. thigh muscles anter/medial thigh sensory medial leg motor sensory adductor muscles medial thigh lateral femoral cutaneous n. sensory lateral thigh sacral plexus • • • L4 - S4 spinal nerves to: = lumbosacral plexus posterior thigh lower leg perineum peripheral nerves : – – sciatic n. posterior thigh entire leg and foot • tibial n. posterior leg, plantar area • common fibular n. lateral leg, dorsum area – superficial fibular n. – deep fibular n. gluteal nerves motor to gluteal muscles dermatomes • • • • area of skin innervated by a spinal nerve (sensory) C1 is motor only all dermatomes overlap show embryological development limb buds from lower neck and L/S areas. joints • Hilton’s law : joints innervated by same nerves that innervate the muscles moving that joint