Neuroanatomy Post-Midterm Notes PDF

Neuroanatomy Post-Midterm Notes I. Basal Nuclei - masses of gray matter found deep within the cerebral hemisphere; indirectly functions in postural control and control of voluntary motor movement Functions: Regulates the motor and premotor cortical areas for smooth voluntary...

Neuroanatomy Post-Midterm Notes I. Basal Nuclei - masses of gray matter found deep within the cerebral hemisphere; indirectly functions in postural control and control of voluntary motor movement Functions: Regulates the motor and premotor cortical areas for smooth voluntary movement Postural control Regulation of voluntary movement and motor learning Supports movement preparation by controlling the positioning of the axial skeleton Influences skilled motor activities Dysfunction causes ballismus Corpus striatum: 1. Caudate nucleus - c-shaped mass of gray matter oriented lateral to the thalamus; separated from the lentiform nucleus by the internal capsule; serves as the information processing highway a. Head of the Caudate: rounded, lateral wall of the anterior horn of the lateral ventricle; attached to the putamen  b. Body of the Caudate: long and narrow, floor of the body of the lateral ventricle c. Tail of the Caudate: long and thin; follows the contour of the lateral ventricle continues forward into the roof of the inferior horn of the lateral ventricle; continuous with the amygdaloid nucleus 1.1 Amygdaloid nucleus - situated in the temporal lobe of the brain; part of the limbic system; influences body;s response to environmental changes (BP, HR, RR, temp, skin color, fear response) 2. Lentiform Nucleus - wedged-shaped mass of graymatter; medial to the external capsule and lateral to the internal capsule a. Putamen: darker lateral portion; involved in learning and motor control, speech articulation, language function, reward, cognitive functioning, and addiction *putaminal dysfunctions are linked with Parkinson’s disease, Huntington disease , Alzheimer disease, depression, and autism among others b. Globus pallidus: lighter inner portion; processes information from the putamen and caudate and fine tunes them to produce smooth movement 3. Claustrum: sheet of gray matter lateral to the external capsule; function unknown Other Related Structures: 1. Substantia Nigra: found in the midbrain; rich in neuromelanin hence the darkened appearance; has many connections to the corpus striatum; dopaminergic (inhibitory) in nature; related to reward and movement *degeneration in the dopaminergic neurons are related to Parkinson’s disease 2. Subthalamic Nuclei - located inferior to the thalamus; has many connections to the globus pallidus; glutaminergic (excitatory) in nature; related to the basal nuclei control of motor movement Connections of the Basal Nuclei: Afferent Fibers: Corpus Striatum Globus Pallidus Corticostriatal Striatopallidal fibers Thalamostriate Nigrostriatal Brainstem striatal fibers Efferent Fibers: Corpus Striatum Globus Pallidus Striatopallidal fibers Pallidofugal fibers (from globus pallidus to Striatonigral fibers thalamus and midbrain) KEY POINTS: 1. The corpus striatum receives afferent information from most of the cerebral cortex, the thalamus, subthalamus, brainstem, and substantia nigra. This information is then channeled into the globus pallidus which then influences motor areas of the brainstem and cerebral cortex 2. The basal nuclei has NO direct influence on the descending pathways to the brainstem and spinal cord, all information has to pass through the globus pallidus II. Cranial Nerves Part of the peripheral nervous system 12 pairs Exits are the foramina of the skull Distributed in the head and neck except for CN X which innervates the thorax and abdomen Sensory: usually starts at the organ where input is received then ends at the cortex where input is processed Sensory-Afferent Pathway: Origin: cells outside the brain; sensory organs, or 1st order neurons  ➔ Cells outside of the brain synapse with processes in the sensory nuclei 2nd order neurons; cross the midline and terminate towards other sensory nuclei (ex: thalamus) where they synapse with 3rd order neurons Motor: stimulus starts at the cortex then moves toward target organ Motor-Efferent Pathway: Origin: cerebral motor cortex through corticonuclear or corticobulbar fibers (1st order neuron) ➔ Cross to the contralateral side at different levels of the brainstem (interneurons, 2nd order neurons) connect to nerve cells with its processes of the cranial nerve (LMN), then innervate striated muscles (3rd order neurons) Cranial Nerves Organization Innervations Origins Exits CN I Olfactory Sensory/Afferent Smell Cerebral hemisphere Cribriform Plate Bilateral Anosmia - affects olfactory mucous membrane caused by common cold or allergic rhinitis Unilateral Anosmia - affects one olfactory nerve, bulb, or tract. Caused by: Fx of anterior cranial fossa Fx of ethmoid bone Cerebral rumor or meningioma of anterior cranial fossa CN II Optic Sensory/Afferent Vision Cerebral hemisphere Optic Canal Responsible for afferent pupillary and accommodation reflex CN III Oculomotor Motor/Efferent; Parasympathetic Ciliary muscles, pupillary sphincter, Midbrain; medially at the Supraorbital fissure superior, medial, and inferior rectus, interpeduncular fossa inferior oblique, levator palpebrae superioris Responsible for efferent pupillary light and accommodation reflexes CN IV Trochlear Motor/Efferent Superior oblique Midbrain; below inferior colliculus Supraorbital Fissure Palsy can result in double vision CN V Trigeminal Mixed (Sensory and Motor) Sensory: skin of face, oral and nasal, Antero-lateral pons V₁: Supraorbital Fissure  and sinus mucosa, teeth V₂: Foramen Rotundum V₃: Foramen Ovale Motor: medial and lateral pterygoid, masseter, temporalis, ant belly of digastric, mylohyoid Trigeminal Neuralgia - severe stabbing pain over the face; occurs mostly on V₂ and V₃ sensory supply CN VI Abducens Motor/Efferent Lateral rectus Pons; pontomedullary junction Supraorbital Fissure CN VII Facial Mixed (Sensory and Motor) ; Sensory: taste to anterior ⅔ of Pons; pontomedullary junction Internal Acoustic Meatus Parasympathetic tongue Motor: muscles of expression, lacrimal, nasal, palatine, submandibular, and sublingual glands Affectation to this nerve may result in Bell’s Palsy CN VIII Vestibulocochlear Sensory/Afferent Balance and hearing Pons; cerebellopontine angle Internal Acoustic Meatus Vertigo is a result of affectation to this cranial nerve CN IX Glossopharyngeal Mixed (Sensory and Motor) ; Sensory: posterior ⅓ of tongue, Medulla oblongata; dorsolateral Jugular Foramen Parasympathetic general sensation to pharynx, sulcus tonsillar sinus, pharyngotympanic tube, middle ear cavity Motor: stylopharyngeus parotid gland Responsible for gag reflex; elevation of uvula upon stimulation of the pharyngeal wall CN X Vagus Mixed (Sensory and Motor) ; Sensory: pharynx, larynx, lungs, Medulla oblongata; dorsolateral Jugular Foramen Parasympathetic heart, GI tract to left colic flexure sulcus Motor: palate, pharynx, larynx, bronchial tree, heart, GI tract to left colic flexure *longest cranial nerve CN XI Spinal Accessory Motor/Efferent Sternocleidomastoid and trapezius Medulla oblongata; dorsolateral Jugular Foramen, Foramen Magnum sulcus Paralysis of trapezius results in lateral winging of the scapula CN XII Hypoglossal Motor/Efferent All intrinsic and extrinsic muscles of Medulla oblongata; anterolateral Hypoglossal Canal the tongue except palatoglossus sulcus III. Meninges - protective tissue surrounding the brain and brainstem Protect the brain and spinal cord; prevent direct contact with the skull and spinal column Support blood vessels, nerves, and cerebrospinal fluid Cerebrospinal Fluid – fluid medium in which brain is suspended, remove waste product associated with neuronal activity, protect brain from trauma, hormonal support Meninges of the Brain 1. Dura Mater – tough, fibrous sheet extending from the foramen magnum down to the 2nd sacral vertebra ○ Extradural / Epidural Space – separates dura from the vertebral column ○ Subdural Space – space between dura and arachnoid; extends around the optic nerve as far as the eyeball ○ Endosteal / Periosteal Layer – covers the inner surface of the skull bones; not continuous with the dura mater of the spinal cord; continuous with the periosteum of skull bones and with the sutures via sutural ligaments Falx Cerebri – sickle shaped; separates the 2 cerebral hemispheres by projecting anteriorly; attaches to the internal occipital crest and fixed margin contains the occipital sinus Tentorium Cerebelli – crescent shaped; covers cerebellum; tentorial notch: gap in the front for the midbrain 2. Arachnoid Mater - impermeable membrane between dura and pia mater; thin, transparent sheath ○ Subdural Space – space between dura and arachnoid ○ Subarachnoid Space – between arachnoid and pia mater; filled with CSF ○ Arachnoid Villi – projections into the venous sinuses; sites where CSF diffuse into the bloodstream ○ Arachnoid Granulations – aggregations of villi 3. Pia Mater – Vascular membrane covered by mesothelial cells  ○ Closely adhered to the brain (gyri, through the deepest sulci) ○ Extends to the cranial nerves and fuses with the epineurium Meninges of the Spinal Cord 1. Dura Mater – Thick, dense, encloses spinal cord and cauda equina ○ Continuous with the dura of the brain ○ Starts at foramen magnum extends into the coccyx ○ Not attached to the vertebrae; separated by the epidural space (contains fat and internal vertebral venous plexus) ○ Separated from the vertebral canal by the extradural space (contains loose areolar tissue and internal vertebral venous plexus) ○ Extends along each nerve root 2. Arachnoid Mater – delicate, impermeable membrane ○ Subarachnoid Space – wide separation from pia mater; filled with CSF ○ Continuous with arachnoid of the brain from the foramen magnum extending into the filum terminale ○ Continuous with spinal nerve roots forming small extensions of the subarachnoid space 3. Pia Mater – adheres closely to the spinal cord ○ Ligamentum Denticulatum – Thickened pia mater between the nerve roots suspending the spinal cord in the middle of the dural sheath ○ Continuous with each nerve root ○ Forms filum terminale ○ Extends outside of the dura called filum terminale externum (tip of coccyx to the dural sac of coccyx) IV. Ventricles and Cerebrospinal Fluid Cerebrospinal Fluid ➔ Clear, colorless liquid ➔ Volume: 130-150mL at a time; the brain can produce 500mL of CSF a day ➔ Found in: ◆ Ventricles ◆ Subarachnoid space ➔ Function:  ◆ Cushions and protects CNS ◆ Provides buoyancy and support ◆ Serves as a reservoir and assists regulation of contents in the brain (brain and CSF volume have an inverse relationship) ◆ Nourishes the CNS ◆ Removes metabolites from the CNS ◆ Serves as pathway for pineal secretions to reach the pituitary Flow of Cerebrospinal Fluid Carlyle Let's Meet Tomorrow Sa Foundation Lami Mukaon Shawarma, Asa (ka)? Castor Let Me Touch Sorra For Long Minutes Since April 1. Choroid Plexus - plexus of cells that function to produce CSF and maintain the composition and volume of fluid in the brain 2. Lateral Ventricles - two curve-shaped cavities located within the cerebrum; separated by septum pellucidum, do not communicate directly 3. Foramen of Monro / Interventricular Foramen - connect the pair of lateral ventricles with the 3rd ventricle at the brain’s midline 4. Third Ventricle - narrow cavity that resembles a slit located between the two thalami; communicates anteriorly with lateral ventricles via the interventricular foramen and posteriorly with the fourth ventricle via the cerebral aqueduct 5. Sylvian Aqueduct / Cerebral Aqueduct - connects third ventral with fourth ventricle; no choroid plexus; 1.8 cm in length 6. Fourth Ventricle - rhomboid, diamond, or tent shaped 7. Foramen of Luschka - lateral aperture of fourth ventricle to the subarachnoid space 8. Foramen of Magendie - medial aperture of fourth ventricle to the subarachnoid space 9. Subarachnoid - contains large blood vessels of the brain; filled with CSF 10. Arachnoid Blood Brain and Blood CSF Barriers ➔ In order for the CNS to maintain homeostasis, it should be isolated from the blood by blood brain and blood CSF barriers 1. Blood Brain Barrier (BBB) - inversely related to size of molecules, directly related to lipid solubility; gas and water directly pass through the barrier, glucose and electrolytes pass at a slower rate; barrier is impermeable to plasma proteins and other larger molecules a. BBB for newborns is more permeable to certain substances  b. Is a continuous lipid bilayer encircling the endothelial cells and isolating brain tissue from blood 2. Blood CSF Barrier - free passage of water, gases, and lipid soluble material from blood to CSf a. Macromolecules cannot enter CSF b. Protect brain and spinal cord from harmful substances while permitting gases and nutrients to enter nervous tissue c. Highly selective permeable membrane d. Prevents entry of neurotoxins Clinical Application: Hydrocephalus - derived from the Greek “hydro” meaning water and “cephalus” meaning head; excessive accumulation of fluid in the brain V. Arterial Blood Supply of the Brain Circle of Willis - anastomosis of the internal carotid and vertebral arteries; it is a ring-shaped network of arteries that supplies blood to the brain Situated at the interpeduncular fossa Allows collateral blood flow \  Comprised of: Acomm, Pcomm, ACA, PCA Arteries of the Head and Neck Common Carotid Artery ○ Internal Carotid Artery ○ External Carotid Artery Subclavian Artery ○ Vertebral Artery Major Arteries of the Brain Cerebrum Internal Carotid Artery Ascends vertically in the neck ICA Supplies the: ○ Anterior part of brain ○ Eye and appendages ○ Branches to forehead and nose (Inf - Post) ○ Cervical ○ Petrous ○ Cavernous ○ Cerebral ICA: Ophthalmic branch ○ Supplies eye ICA: Choroidal branch ○ Choroid Plexus ○ Crus Cerebri ○ Lateral Geniculate Body ○ Optic Tract ○ Internal Capsule Anterior Cerebral Artery Supplies the: ACA ○ Medial cerebral surface Occlusion affects: ○ Paracentral lobule Contralateral somatosensory loss in LE Contralateral weakness in LE with Babinski sign Urinary incontinence ○ Corpus Callosum Infarction dyspraxia and tactile agnosia of L limbs Medial Cerebral Artery Supplies the: MCA ○ Lateral cerebral surface ○ All motor areas except legs  Occlusion includes: ○ C/L Hemiparesis ○ C/L Hemisensory loss ○ C/L Homonymous hemianopia ○ Aphasia ○ Perceptual deficits ○ Conjugate palsy (opposite side) ○ Pure motor stroke ○ Phineas gage syndrome ○ Auditory deficit ○ Neglect ○ Apraxia ○ Gerstmann Syndrome Cerebellar Arteries External Carotid Artery Supplies the: ECA ○ Neck ○ Face ○ Scalp Vertebral Artery Ascends through foramina of transverse processes of C1-C6 VA Enters skull via foramen magnum Joins opposite vertebral artery to form basilar artery Meningeal arteries ○ Supplies the skull and dura mater of the posterior cranial fossa Posterior spinal arteries ○ Supplies the posterior ⅓ of the spinal cord Anterior spinal arteries  ○ Supplies the anterior ⅔ of the spinal cord Posterior inferior cerebellar ○ Largest branch ○ Supplies undersurface of cerebellum and central nuclei of cerebellum Medullary arteries ○ Supplies the medulla Radicular Artery ○ Branch of intercostal arteries ○ Supply T1-L1 ○ Great ventral radicular: largest branch found entering T8-L4 (AKA Artery of Adamkewics) Basilar Artery Union of 2 vertebral arteries Ascends in the posterior pons Pontine ○ Supplies the pons Labyrinthine / auditory ○ Supplies internal ear Anterior inferior cerebellar ○ Blood supply to anterior and inferior cerebellum ○ Pons ○ Medulla oblongata Superior cerebellar ○ Superior surface of cerebellum ○ Pons ○ Pineal gland Posterior cerebellar ○ Visual cortex ○ Inferolateral and medial temporal ○ Diencephalon and lentiform nucleus ○ Midbrain ○ Pineal gland ○ Choroid plexus ○ Inferior portion of parietal lobe CVA results in: ○ C/L homonymous hemianopsia - contralateral visual ignorance ○ Cortical blindness ○ Visual agnosia ○ Prosopagnosia ○ Dyslexia ○ Memory defect ○ Thalamic pain ○ Movement disorders; athetosis, chorea, tremor ○ C/L hemiplegia Athetosis - slow, involuntary, and continuous writhing movement of the limbs, trunk, face, neck and tongue Chorea - neurological disorder that causes involuntary and  unpredictable rapid movements that resemble dancing SUMMARY OF POSTERIOR CIRCULATION Basal Ganglia Striate Arteries Thalamus Pcomm, PCA, basilar Midbrain PCA, SCA, basilar Pons SCA, AICA, basilar Medulla oblongata Vertebral, AICA, SCA Cerebellum SCA, AICA, PICA