Introduction_to_Brain.pptx .cerebralsystem

Brain
Cerebral system
Sulcus

1. Neuro -Anatomy

2. GENERAL CONSIDERATION Nervous system provides a complex mechanism by which we can react to ever changing external & internal environment

3. GENERAL CONSIDERATION Disturbance in environment acts as a stimulus Response may be voluntary, involuntary or reflex activities

4. GENERAL CONSIDERATION Stimulus-response loops up the memory stores In highly evolved species memory stores are flexible & continuously modified by learning

5. SUBDIVISIONS OF THE NERVOUS SYSTEM Anatomically - 2 parts Central nervous system Peripheral nervous system Functionally - 2 parts Somatic nervous system Autonomic nervous system

6. CENTRAL NERVOUS SYSTEM It includes the brain & spinal cord Concerned with perception & integration of sensory information, and initiation & coordination of motor activities

7. PERIPHERAL NERVOUS SYSTEM It includes 12 pairs of cranial nerves & 31 pairs of spinal nerves Cranial nerves are attached to brain Spinal nerves are attached to spinal cord

8. PERIPHERAL NERVOUS SYSTEM Input to CNS- from sense organs & sensory receptors of body Output from CNS- to muscles & glands of body

9. SOMATIC NERVOUS SYSTEM Deals with any changes in external environment ( E xteroceptive or Proprioceptive ) Response expressed by movements of skeletal muscles

10. SOMATIC NERVOUS SYSTEM for voluntary movements 2 sets of neurons involved Upper motor neurons - cell bodies are located in motor area of cerebral cortex, nuclei of basal ganglia & brain stem , synaptic contact with lower motor neurons Lower motor neurons - cell bodies lie in grey matter of brain stem & spinal cord , axons supply striated muscles.

11. AUTONOMIC NERVOUS SYSTEM Deals with changes in internal environment- Regulation of body temperature, Blood pressure, Cardio-respiratory rate, GI motility & Glandular secretion

12. AUTONOMIC NERVOUS SYSTEM Motor component of ANS has 2 sets of neurons - preganglionic & postganglionic Effector of postganglionic neurons are 3 types - cardiac muscles, smooth muscles & glandular cells. ANS has 2 subdivisions - sympathetic ( thoraco -lumbar) & parasympathetic ( cranio -sacral)

13. INTRODUCTION TO BRAIN & ITS SUBDIVISIONS

14. BRAIN Lies in cranial cavity Caudally it continue with spinal cord through the foramen magnum It consists of- Cerebrum, cerebellum & Brain stem Brain stem includes – mid brain, pons & medulla oblongata

15. BRAIN Grey matter consists of – neuronal cell bodies, neuroglia & blood vessels White matter includes- nerve fibres, neuroglia & blood vessels

16. BRAIN In cerebrum & cerebellum , grey matter appears at surface & white matter lies in the interior In brain stem & spinal cord however grey matter lies within & white matter outside

17. BRAIN Weight in air - 1400gms (2% of total body weight) Weight in CSF - 50gms Cerebral blood flow- 750ml per minute (1/6 th of cardiac output) Oxygen consumption is 1/5 th of total body requirement Occlusion of blood vessels produce unconsciousness within 10 seconds

18. BRAIN Total neurons in cerebral cortex is 10-15 bilions , glia cells 50 bilion 1/3 rd of surface area is exposed at the Gyri 2/3 rd lies at the depth of the Sulci

19. BRAIN Monro -Kellie doctrine – cranial box is rigid & constant in volume and contains brain, blood & CSF If any one increase, other 2 must decrease

20. SUBDIVISIONS OF BRAIN Embryologically into 3 parts- fore brain ( prosencephalon ), Mid brain ( mesencephalon ) & Hind brain ( rhombencephalon )

21. SUBDIVISIONS OF BRAIN Fore brain consists of- T elencephalon & Diencephalon Telencephalon includes- pair of cerebral hemisphere with lateral ventricle & rostral part of 3 rd ventricle infront of interventricular foramen

22. Cerebral Hemispheres: Each hemisphere divided into 5 lobes Frontal Parietal Occipital Temporal Insula Created by deep sulci Functional areas: motor, sensory Associative areas: integrate pg 349

23. SUBDIVISIONS OF BRAIN Diencephalon includes- neuronal masses around cavity of 3 rd ventricle Consists of Thalamus, Metathalamus , Subthalamus & Hypothalamus

24. Diencephalon Thalamus Communicates sensory info of cerebral cortex Hypothalamus Regulates many body activities Emotion, sleep, memory, etc. Pituitary Gland-hormones Epithalamus Pineal Gland-hormone pg 366

25. SUBDIVISIONS OF BRAIN Limbic lobe- in inferomedial wall of cerebral hemisphere around peripheral margin of diencephalon Olfactory & optic nerves are attached to ventral surface of forebrain

26. WHITE MATTER OF CEREBRAL HEMISPHERE There are 3 types : 1- Association fibers: Interconnect cortical sites lying within one hemisphere. They are short or long fibers . 2- Commissural fibers: Connecting functionally related gyri on both hemisphere. 3- Projection fibers: Connecting the cortex with the lower centers in thalamus brain stem, or spinal cord. They are ascending or descending.

27. SUBDIVISIONS OF BRAIN Mid brain 2cm long, Traversed by aqueduct of Sylvius - which communicate 3 rd & 4 th ventricles 3 rd & 4 th cranial nerves attached to mid brain Visual and Auditory reflex centers

28. SUBDIVISIONS OF BRAIN Hind brain Consists of pons & medulla oblongata ventrally and cerebellum dorsally Ventral & dorsal components are separated by cavity of 4 th ventricle 5 th nerve attached to pons 6 th , 7 th & 8 th nerves attached to ponto-medullary junction

29. SUBDIVISIONS OF BRAIN 9 th , 10 th , 11 th & 12 th nerves are attached to medulla oblongata Cerebellum is connected to brain stem by three pairs of peduncles - superior peduncle with mid brain, middle peduncle with pons & inferior peduncle with medulla oblongata

30. Brainstem: Medulla Oblongata Regulates several basic physiological functions Heartbeat (rate and force) Blood pressure (vasoconstriction/dilation of arteries) Breathing (rate and depth) Others: speech, coughing, sneezing, salivation, swallowing, gagging, vomiting, sweating

31. Smooths + coordinates body movements directed by other parts of brain Information on equilibrium Movement of neck, trunk, limbs Information from Cerebral cortex Cerebellum pg 372

32. Reticular Formation Medulla, Pons, Midbrain Maintains cerebral cortex alertness Filters out repetitive stimuli Regulates skeletal + voluntary muscle activity

33. COVERINGS OF THE BRAIN Brain is soft, greyish , gelatinous organ Brain & spinal cord are covered by 3 membranes from outside inwards- Dura, Arachnoid & Pia matter

34. Meninges: 3 membranes around brain and spinal cord Made of Connective tissue Functions Cover, Protect CNS Enclose, protect blood vessels supplying CNS Contain CSF pg 375

35. Dura mater Strongest , 2 Layers, Fibrous Connective Tissue Endosteal layer : External/superficial layer Meningeal layer: Internal/deep layer Layers fused except around dural sinuses Partitions: limit movement of brain Falx Cerebri –vertical, between cerebral hemispheres Falx Cerebelli -vertical, between cerebellar hemispheres Tentorium Cerebelli –horizontal, between cerebrum and cerebellum

36. Arachnoid Mater Middle layer Subarachnoid Space -between arachnoid mater and pia mater (contains most of CSF, blood vessels) Arachnoid Villi - projections of arachnoid mater through dura into superior sagittal sinus, act as valves to help CSF pass into dural sinuses

37. Pia Mater Innermost layer Delicate, highly vascular Clings directly to brain tissue, dips into convolutions pg 375

38. Ventricles Expansions of brain’s central cavity Lined with Ependymal Cells Filled with CSF (cerebrospinal fluid) Ventricles continuous w/each other + central canal of spinal cord

39. Ventricles (continued) Lateral Ventricles (#1+2) Cerebral Hemisphere Separated by Septum Pellucidum Third Ventricle Diencephalon Interventricular Foramen : connects to lateral ventricle pg 376 3 4 lateral

40. Ventricles (continued) Fourth Ventricle Hindbrain Cerebral Aqueduct: connects 3 rd and 4 th ventricles Connects to central canal of spinal cord & medulla 3 openings connect 4 th to subarachnoid space 2 lateral apertures 1 median aperture pg 376 3 4 lateral

41. Cerebrospinal Fluid Liquid cushion for brain and spinal cord Nourishes brain Removes waste Conducts chemical signals between parts of CNS (e.g. hormones) Forms as a filtrate of blood in choroid plexuses

42. Choroid Plexuses Choroid Plexuses : groups of capillaries surrounded by ependymal cells Made of sodium, chloride ions, proteins, glucose, O 2

43. Flow of CSF Formed in Choroid plexuses Through Ventricles Into Subarachnoid space & central canal from 4 th ventricle Through Arachnoid Villi into Superior Sagittal Sinus Into Internal Jugular Vein

44. CISTERNAE Enlarged subarachnoid space at the base of brain 1) cisterna magna-b/w caudal surface of cerebellum & dorsal surface of medulla 2) Cisterna pontis - b/w ventral surface of pons & base of skull

45. CISTERNAE 3) cisterna interpeduncularis 4) cisterna ambiens - b/w splenium of corpus callosum & tectum of mid brain 5) cisterna of lateral sulcus .

46. SPINAL CORD

47. SPINAL CORD Enlarged & cylindrical part of CNS Lie in upper 2/3 rd of vertebral canal It retains primitive form of CNS Concerned with reception of different modalities of sensory input, integrates & associates the information & produces reflux response of basic character

48. Blood Brain Barrier Protects brain from blood-borne toxins (e.g. urea, food toxins, bacteria) Endothelium of brain capillaries are loaded with tight junction to decrease permeability Not complete protection, some things still have to get through (e.g. fat-soluble molecules can pass through)

49. Cranial Nerves: I - XII 12 Pairs Numbered Anterior to Posterior Attach to Ventral surface of brain Exit brain through foramina in skull I + II attach to Forebrain (cerebrum + diencephalon) III-XII attach to Brainstem (midbrain, pons , medulla) Only X goes beyond the head-neck

50. I Olfactory-------- Sensory --smell II Optic------------- Sensory --vision III Oculomotor ---- Motor ----extrinsic eye muscles IV Trochlear ------- Motor ----extrinsic eye muscles V Tri geminal V 1 Opthalmic ----- Sensory -cornea, nasal mucosa, face skin V 2 Maxillary------ Sensory -skin of face, oral cavity, teeth V 3 Mandibular --- Motor -muscles of mastication --- Sensory -face skin, teeth, tongue (general) Cranial Nerve Function

51. VI Abducens -------------- Motor -----eye abduction muscles VII Facial------------------- Sensory ---part of tongue (taste) ------------------- Motor ------muscles of facial expression VIII Vestibulocochlear --- Sensory ----hearing, equilibrium IX Glossopharyngeal ---- Motor ------ stylopharyngeus muscle ---- Sensory ----tongue (gen & taste), pharynx X Vagus ------------------ Motor -------pharynx, larynx ------------------- Sensory ----pharynx, larynx, abd . organs XI Accessory------------- Motor ------ trapezius , sternocleidomastoid XII Hypoglossal---------- Motor -------tongue muscles Cranial Nerves (continued)

52. Summary of Functional Groups Purely Sensory = I, II, VIII Primarily Motor = III, IV, VI, XI, XII Mixed = V, VII, IX, X Parasympathetic Fibers = III, VII, IX, X (Division of Autonomic NS = Visceral Motor)

53. Parasympathetic Fibers CN III = Oculomotor Contracts Iris (controls pupil) Contracts Ciliary Muscle (controls lens) CN VII = Facial Innervates Salivary glands ( mandibular & sublingual) Innervates Lacrimal gland CN IX = Glossopharyngeal Innervates Parotid Salivary gland CN X = Vagus Innervates thoracic & abdominal viscera

54. Thank you