Development of Nervous System/Cranial Nerve PDF

Development of Nervous System/ Cranial Nerve Ch 5 Ekman, Ch 7 Bear Dr. Meeyoung Kim Neuroscience when what event is happening!!...

Development of Nervous System/ Cranial Nerve Ch 5 Ekman, Ch 7 Bear Dr. Meeyoung Kim Neuroscience when what event is happening!! Physiotherapy Dept. University of Sharjah  forms both brain and spinal cord know which week Formation of the neural tube and neural crest embryo circular shaped ectoderm - part of it would become neural plate mesoderm endoderm In the third week of human embryonic development the neuroectoderm appears and forms the neural plate along the dorsal side of the embryo. A groove forms along the long axis of the neural plate and, by week four of development, the neural plate wraps in on itself to give rise to the neural tube, which is filled with cerebrospinal fluid (CSF). neural tube week 4 neural plate week 3  3 neural tube The three germ layers are formed at gastrulation at 3rd week of gestation 3 layers are formed Ectoderm: outside, surrounds other layers later in development, generates skin and nervous tissue. Mesoderm: middle layer, generates most of the muscle, blood and connective tissues of the body and placenta. Endoderm: eventually most interior of embryo, generates the epithelial lining and associated glands of the gut, lung, and urogenital tracts.  forming neural tube from central part and then it zip up and zip down Neurulation: folding and closure of the neural plate between ectoderm and mesoderm 1. As neural folds close, neural crest delaminates and migrates away there are two neural folds, ant. and post. 2. Closure happens should be fully closed, first in middle of otherwise there will be abnormality the tube and then zips rostrally and caudally. making a hinge of neural plate makes full circle and then divided from ectoderm  Neurulation: folding and closure of the neural plate Folding and closure of the neural tube occurs first in the cervical region. close around day 25 The neural tube then “zips” up toward the head and toward the tail, leaving two openings which are the anterior and posterior neuropores. The anterior neuropore closes around day 25. The posterior neuropore closes around day 28. close around day 28 https://www.youtube.com/watch?v=lGLexQR9xGs Failure of neuropores to close can caus e neural tube defects anterior neuropore: anencephaly baby born without parts of skull and brain posterior neuropore: spina bifida spine and spinal cord not formed properly  “Regression” of the spinal cord until 3rd month, spinal cord and spinal column length is same and then spinal column gets longer so there is regression of spinal cord The spinal cord and the vertebral column are until 3 months have same length the same length up until the 3rd month. As each vertebral body grows thicker, the over all length of the vertebral column begins to exc know the levels eed that of the spinal cord such that , in the adult the spinal cord terminates at L2 or 3 and the dural sac ends at about S2. during regression, there is a pattern between meninges, spinal cord and The tail end of the dural sac covering the spinal ligament they make cord and nerve roots remains attached at the c obstruction of CSF flow -> there is occyx and becomes a long, thin strand called hydrocephalus the filum terminale. (water in brain) Sometimes, the spinal cord can become baby with “tethered” or attached to the dural sac or twisted hydrocephalus - big head because skull not filum terminale; this pulls on the cord and can fully secured obstruct flow of CSF thus causing swelling of the ventricles of the brain (hydrocephalus),  when neural tube forms, brain also tries to divide Primary brain vesicles The process by which structures become more complex and functionally specialized during development is called differentiation. The first step in the differentiation of the brain is the development, at the rostral end of the neural tube, of three swellings called the primary brain vesicles. forebrain (prosencephalon) midbrain (mesencephalon) hindbrain (rhombencephalon)  Secondary brain vesicles further divide into the five secondary brain vesicles – telencephalon (future cerebral cortex and basal ganglia) diencephalon (future thalamus and hypothalamus), mesencephalon (future midbrain, colliculi), metencephalon (future pons and cerebellum) myelencephalon (future medulla) primary secondary  telencephalon (future cerebral cortex and basal Differentiation of the ganglia) telencephalon Differentiation of the midbrain mesencephalon (future midbrain, colliculi) Differentiation of the rostral hindbrain metencephalon (future pons and cerebellum) Differentiation of the caudal hindbrain myelencephalon (future medulla) Differentiation of the spinal cord Cranial Nerve IMPORTANT! The cranial nerves are a group of 12 paired nerves in the peripheral nervous system (PNS) integral to the reception of sensory information and transmission of muscle commands. http://vanat.cvm.umn.edu/neurLab4 /Lab4NucNerveAttach.html CN - Names and functions?  3 4 6 - movt of eye oculomotor has parasympathetic fibers Where is origin of each CN? 5 and 7 biggest cranial nerves in face know the locations 1 2 8 - purely sensory 3 4 6 11 12 - purely motor 5 7 9 10 - mixed Some Say Marry Money But My Brother Says Big Brain Matters Most 3 7 9 10 has parasympathetic fibers 1. Which is Olfactory bulb Lateral geniculate nucleus motor only, sensory only? And their innervating structures? 2. Which is parasympathe tic? And what is related ganglion? And what is the function? 3. Difference between V and VII, and between 2 tongue N  Some cranial nerves contain only sensory fibres, some contain only motor fibres, and some contain both. CN and functions Some cranial nerves convey parasympathetic fibres. 1. OLFACTORY NERVE olfactory nerve The olfactory nerve (CN I) originates in the nasal cavity and passes through each side of the nose, terminating in masses of gray matter called the olfactory bulbs. SENSORY Transmits signals for smell 2. OPTIC NERVE The optic nerve (CN II) originates in the retina of each eye and terminates in the thalamus. From there, signals are transmitted to the visual cortex. SENSORY Receives signals for vision from each retina left side of cortex will go into right side right side will go to left side 3. OCULOMOTOR NERVE Trochlear The Oculomotor nerve (CN III) extends from the midbrain and divides into the superior and inferior branches to control the no sensory fibers muscles of the eye. Interpeduncular fossa MOTOR Innervates the extrinsic and intrinsic eyeball muscles, in addition to the upper eyelid eye movt. muscle PARASYMPATHETIC Constricts control size of pupil the pupil to reduce the amount of light that enters, and contracts the ciliary muscles to adapt for short range vision  know which CN will move eye CN and their matching muscle for eye movement Trochlear nerve for superior oblique muscle of the eye Abducens nerve for the lateral rectus muscle Oculomotor rest of muscle 4. TROCHLEAR NERVE thinnest but longest among all cranial nerve The trochlear nerve (CN IV) originates in the midbrain and travels via the superior orbital fissure of the sphenoid to enter each orbit. MOTOR Innervates the superior oblique muscle that controls the up and down movement of the eye FUN FACT! Though it is the smallest cranial nerve (by number of axons), CN IV has the longest intracranial course  biggest 3rd branch has motor fibres only rest 2 sensory only senses from facial skin through trigeminal n 5. TRIGEMINAL NERVE Each trigeminal nerve (CN V) divides into three major branches for SENSORY: ophthalmic, maxillary, and mandibular. MOTOR Innervates the muscles of mastication and the pharyngeal arch SENSORY Receives impulses from the skin, mucous membranes, and sinuses  Largest The ophthalmic and maxillary nerves are purely sensory, whereas the mandibular nerve (V3) supplies motor as well as sensory  The abducens nerve (CN VI) fibers originate in the 6. ABDUCENS abducens nucleus in the pons and pass through the superior orbital fissure of the sphenoid. NERVE MOTOR Innervates the lateral rectus muscle that causes the abduction (lateral rotation) of eyeballs  second biggest cranial nerve 7. FACIAL NERVE movements of face by facial nerve The motor part of the facial nerve (CN VII) begins in the pons and ends in five branches: temporal, zygomatic, buccal, mandibular, and cervical. The sensory fibers end in the pons and gustatory cortex. MOTOR Innervates muscles in the face, scalp, and neck as well as the stapedius in the ear SENSORY Receives signals from taste buds in the anterior 2/3 portion of the tongue and some posterior 1/3rd by glossopharyngeal proprioceptors in the face and scalp PARASYMPATHETIC Supplies the lacrimal, salivary, and mucous glands. REMEMBER! Sensation on the face is innervated by the trigeminal nerves (V) as are the muscles of mastication, but the muscles of facial expression are innervated mainly by the facial nerve (VII) as is the sensation of taste. upper part of face innervated by two sides of facial nerve upper motor neuron lesion (damage in the brain or upper part of nerve pathway) - upper half of the face is innervated by lower part innervated by same side facial nerve both sides of hemis. so if there is damage to the upper motor neuron, pt can still wrinkle forehead becs unaffected hemis will provide input to forehead m. However, the lower half of the face on opp side will be affected and it will be drooping. Remember upper half of lower motor neuron lesion (damage to facial n. after it exited the brain) - this causes a complete loss of movt on the same side of the face, affecting both upper and lower parts. pt wont be able to wrinkle or smile on that side of the face. face innervated by both IMPORTANT! cerebral hemispheres so if upper motor neuron lesion this is imp for diagnosing where the nerve damage is located, based on the symptoms provided can still wrinkle forehead in stroke patients, MCA effected facial nerve palsy  8. VESTIBULOCOCHLEAR NERVE The vestibulocochlear nerve (CN VIII) has two branches: cochlear and hearing balance vestibular. Both enter the brainstem and synapse with cells in the cochlear nucleus of the medulla oblongata. Sensory - The cochlear nerves transmit signals for hearing; the vestibular nerves transmit signals for equilibrium.  tongue 9. GLOSSOSPHARYNGEAL NERVE The glossopharyngeal nerve (CN IX) originates in the medulla oblongata and exits the skull via the jugular foramen. MOTOR Innervates the stylopharyngeus muscle to elevate the pharynx and larynx. SENSORY Receives signals from proprioceptors in swallowing muscles, baroreceptors in the carotid sinus, and chemoreceptors in the carotid body. Provides sensory function to the oropharynx. PARASYMPATHETIC Innervates the parotid gland to secrete saliva. 10. VAGUS NERVE The vagus nerve (CN X) originates in the medulla oblongata and exits the skull via the jugular foramen, dividing into numerous branches that supply many parts of body. MOTOR Innervates muscles of the pharynx, larynx, and soft palate for vocalization and swallowing. SENSORY Receives signals from the external ear, some taste buds in the epiglottis and pharynx, and proprioceptors in the throat and neck. PARASYMPATHETIC Controls heart rate, breathing, sweating, movements of the gut, and other subconscious activities. Also vasodilates blood vessels, which is the cause of fainting from stress.  Facial nerve: anterior two-thirds of the Three tongue nerves Glossopharyngeal nerve: the posterior third of the tongue associated Vagus nerve: root of tongue and the with taste epiglottis region. sensation Taste fibers categorize as special visceral afferent (SVA).  The accessory nerve (CN XI) arises from the first five 11. ACCESSORY segments of the cervical portion on the spinal cord. NERVE MOTOR Innervates the sternocleidomastoid and the trapezius to control head movements. 12. HYPOGLOSSAL NERVE The hypoglossal nerve (CN XII) is responsible for movement of the tongue. Of the eight muscles, only the palatoglossus is not controlled by hypoglossal nerve; instead, it is innervated by the vagus nerve. MOTOR Any questions?