Functions of the Brain Stem, Schemes and Mind Maps of Mechanics

Download Functions of the Brain Stem and more Schemes and Mind Maps Mechanics in PDF only on Docsity! Functions of the Brain Stem Dr Syed Shahid Habib Professor & Consultant Clinical Neurophysiology Dept. of Physiology King Saud University Festgjal Medial ongtusinal Dertae nustus racleus fascicus Floceuionaclar/ sa Vestoulospnal act eetcuospina Ruotospinal tract Flgure 35-19, CGannestions of viet aularnerva hong the vardar nus he liane aval ute area) with chor aeans at fe cara! syle Inferior olieas Nucleus of the laters Tennis Pons = Superior Dorsal nae acoustic ‘i Intermediate Cochlear —_ nut Madu “Trapezoid bocy ‘Aukliloryre-vous alta, {Mche! sn Bk ea oy sem. 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ON nian Glessepharyngeal PetScal OS. soltany tract Gustatry snglan Prarynx Figure 58-2 Transmisslon cf taste slgnels into tne cera nervous system. Olfactory tract ‘Anterior perforated substance Mud ay _ — C7 Infundibulum (pituitary stalk) Optic chiasm p 3 ed Mamimillary bodies ~~ Optic tract — 7 Je ET | ——— Temporal lobe (cut surface) Oculomator nerve (II!) Anterior view Tuber cinereum Trochlear nerve (IV) Cerebral crus Si ‘ 3 Trigeminal nerve (V) Lateral geniculate body: ‘Abducent nerve (VI) FU 4 ; Facial nerve (Vil) and Posterior perforated substance“ / a intermediate nerve Vestibulocochlear nerve (VIII) Pons " Flocculus of cerebellum . A al " Middle cerebellar nedunde-™ ‘ i x 4 " " 3 >— Choroid plexus of 4th ventricle Olive Glossopharyngeal nerve (IX) Vagus nerve (X) Hypoglossal nerve (XI) ‘Accessory nerve (XI) FIGURE 8A: Brainstem 3 — Cranial Nerves Nuclei — Motor FIGURE 8B: Brainstem 4 — Cranial Nerves Nuclei — Sensory •Brain stem serves as a way station for “command signals” from higher neural centers. •The autonomic nervous system is activated mainly by centers located in the spinal cord, brain stem, and hypothalamus (Cardiovascular Gastrointestinal Autonomic Reflexes.) •Functions of Brain Stem Nuclei in Controlling Subconscious, Stereotyped Movements (anencephaly) •Motor branch of the fifth cranial nerve, and the chewing process is controlled by nuclei in the brain stem and also swallowing, salivary secretion, vomiting (chemoreceptor trigger zone) •The actual mechanics of feeding are controlled by centers in the brain stem. •Vasomotor center for CV control (Baroreceptors) in medulla •Brain stem Neurohormonal Systems in the human brain for activating four neurohormonal systems •Many of the behavioral functions elicited from the hypothalamus and other limbic structures are also mediated through the reticular nuclei in the brain stem and their associated nuclei. Brain Stem Motor Functions (cont.) • Although the micturition reflex is an autonomic spinal cord reflex, it can also be inhibited or facilitated by centers in the cerebral cortex or brain stem in pons • Accommodation Is Controlled by Parasympathetic Nerves by 3rd CN • Neural Pathways for Control of Eye Movements. also shows brain stem nuclei for the third, fourth, and sixth cranial nerves by medial longitudinal fasciculus • Auditory Nervous Pathways → superior olivary nucleus • Nucleus of tractus solitarious→ Taste pathway→Sup & Inf Salivatory Nuclei • Bulboreticular facilitatory area of brain stem for gamma efferent system (stabilizes joints) • Control of Cerebral Activity by Continuous Excitatory Signals from the Brain Stem (Reticular Excitatory Area of the Brain Stem→bulboreticular facilitory area→it is the same brain stem reticular area that transmits facilitorysignals downward to the spinal cord to maintain tone in the antigravity muscles and to control levels of activity of the spinal cord reflexes. Brain Stem Motor Functions (cont.) 1. Conduct functions (way station) All information related from the body to the cerebrum and cerebellum and vice versa, must traverse the brain stem. a) The ascending sensory pathways coming from the body to the brain includes:
The spinothalamin tract for pain and temperature sensation.
The dorsal column, fasciculus gracilis, and cuneatus for touch, proprioceptive and pressure sensation. b) Descending tracts
The corticospinal tract (UMN): runs through the crus cerebri, the basal part of the pons and the medullary pyramids; 70-90 % of fibers cross in the pyramidal decussation to form the lateral corticospinal tract, destined to synapse on lower motor neurons in the ventral horn of the spinal cord.
Upper motor neurons that originate in the brain stem's vestibular, red, and reticular nuclei, which also descend and synapse in the spinal cord. o Ventral layer of brainstem is motor in function. o Middle layer is sensory in function & contains medial lemniscus which conveys sensory information from dorsal column. Basic Structure of Brain Stem 1. Roof Plate 2. Tegmentum 3. Basal Portion • Nerve pathway to cerebral hemispheres. • Auditory and Visual reflex centers. • Cranial Nerves: • CN III - Oculomotor [motor]. (Related to eye movement). • CN IV - Trochlear [motor]. (Superior oblique muscle of the eye which rotates the eye down and out). Functions of Midbrain CN (Cranial Nerve) Deficits: Ipsilateral CN III, CN IV palsy and ptosis (drooping). Pupils: Size: Midposition to dilated. Reactivity: Sluggish to fixed. Movement: Abnormal extensor. Respiratory: Hyperventilating. Loss of consciousness (LOC): Varies Signs & Symptoms of midbrain lesion • Respiratory Center. • Cranial Nerves:
CN V - Trigeminal [motor and sensory]. (Skin of face, tongue, teeth; muscle of mastication).
CN VI - Abducens [motor]. (Lateral rectus muscle of eye which rotates eye outward).
CN VII - Facial [motor and sensory]. (Muscles of expression).
CN VIII - Acoustic [sensory]. (Hearing) Functions of pons • Pupils size: Pinpoint • LOC: Semi-coma • Movement: Abnormal extensor. • Respiratory: -Apneustic (Abnormal respiration marked by sustained inhalation). -Hyperventilation. • CN Deficits: CN V, CN VI, CN VII, CN VIII. Signs & Symptoms of pons lesion To test reticular formation Alertness, Consciousness & Sleep. Corticospinal tract Motor power, reflexes Pain response Facial grimacing on firm pressure over the supra orbital ridge. To test respiratory center look for the normal pattern of respiration To test cardiovascular functions Look for normal circulatory function To test brainstem reflexes: • Pupilary and corneal reflexes. • Vestibulo-ocular reflex: Injection of iced water into the ear will produce eyes movement. • Oculo-cephalic reflex: Eyes will be fixed when head is moved in one or another directions. • Gag reflex. • Cough reflex A Reticular Inhibitory Area Located in the Lower Brain Stem Excitation of the Excitatory Area by Peripheral Sensory Signals.