![It is Divided into two parts -
i] Ventral Part, called Cerebral Peduncle , chiefly of
white matter, uniting the Pons with the thalamic region
of the cerebrum.
It comprises the – tegmentum, Substantia nigra & basis
peduncle.
ii] Dorsal part, called tectum which constitutes two
elevations, superior and inferior colliculi.](https://image.slidesharecdn.com/nervoussystempart-1-250128105934-0ac3a6b5/85/NERVOUS-SYSTEM-OVERVIEW-CLASSIFICATION-DIVISION-25-320.jpg)
NERVOUS SYSTEM - OVERVIEW, CLASSIFICATION, DIVISION
- 1. OVERVIEW OF NERVOUS SYSTEM Presented By- Amrit Kour Kriya Sharir Dept. R.G.G.P.G Ayurvedic College & Hospital ,Paprola
- 2. INDEX Important Terminolgy Overview of Brain & its Parts Spinal cord & it’s cross – section Peripheral Nervous System & it’s further division. Meninges Clinical importance of meninges.
- 3. Introduction Nervous system is one of the control systems of the body that control various activities of the body, the other one being the endocrine system . Nervous system is quicker than the endocrine system.
- 4. The basic structural & functional unit of nervous system is the individual nerve cell, the Neuron. Billions & Trillions of such neurons constitute the Nervous System.
- 5. Nervous System controls the activities of the body By generating and sending electrical signals in the form of impulses to various organs and regions of the body . It coordinates these activities by receiving input signals from different types of receptors present throughout the body.
- 6. DIVISIONS OF NERVOUS SYSTEM Primarily, nervous system is divided into two parts: 1. Central nervous system 2. Peripheral nervous system.
- 7. CENTRAL NERVOUS SYSTEM The part of the nervous system which occupies the central axis of the body is called CNS. CNS includes brain and spinal cord.
- 8. Main Functions of CNS Receive the Sensory information from P.N.S Process that Information & make the decision Send processed information output through motor nerves.
- 10. CNS - Formed by neurons and supporting cells called neuroglia. Structures of brain and spinal cord are arranged in two layers, namely Gray matter & White matter.
- 11. Grey Matter Group of cell bodies of neurons within CNS. 1.Cortex – Grey matter on the surface of CNS. 2. Nuclei – Grey matter embedded in CNS surrounded by white matter . 3.Ganglia – Grey matter outside the CNS.
- 12. White Matter Collection of Bundles of Axons within C.N.S. The fatty ‘myelin’ in myelinated nerve fibers gives a white appearance to the white matter. 1.Tracts – Bundles of Axons which carry information Up & Down (Ascending & Descending Tracts )
- 13. 2.Commissural Fibers – Bundles of Axons which carry information from Right cerebral hemisphere to left cerebral hemisphere and vise – versa. There are many commissural fibers in the brain Largest Commissural Fiber – Corpus Callosum .
- 15. 3.Association Fibers - These fibers carry information from frontal lobe to the occipital lobe (anterior to posterior lobe & vice-versa)
- 16. Nerve - Collection of axons outside the C.N.S i.e.in the Pheriphery .
- 17. Difference - In brain, white matter is placed in the inner part and gray matter is placed in the outer part. In spinal cord, white matter is in the outer part and gray matter is in the inner part.
- 18. THE BRAIN - It’s weight is about 1.5kg in adults. It comprises all the structures which are intracranial . i.e. located within a hard bony skull. PARTS OF BRAIN – 1. Forebrain 2. Mid-brain 3.Hind-Brain
- 19. The brain also contains 4 interconnected cavities , the cerebral ventricles , that contain cerebrospinal fluid (CSF).
- 20. 1. Forebrain (Prosencephalon) Further divided into Telencephalon & Diencephalon .
- 21. A. TELENCEPHALON – consists of two cerebral hemispheres and their interconnections. i.The hemispheres, although separated by a longitudinal divison , are connected to each other by bundles of nerve fibers known as Commissures. ii.Cortex of each Hemisphere is divided into 4 lobes – Frontal,Parietal ,Occipital & Temporal .
- 22. iii.The cerebral cortex , an area of grey matter, about 3mm thick , is highly folded. This increases the area available for cortical neurons without increasing appreciably the volume of the brain . iv. The subcortical nuclei form other areas of the grey matter that lie deep within the cerebral hemispheres. Predominant among them are the Basal
- 23. ii.Diencephalon- Upper 2/3rd comprises of – Thalamus. Lower 1/3rd comprises of – Hypothalamus Connects with the pituitary complex.
- 24. 2. Mid Brain (Mesencephalon) - It is divided into two parts by Aqueduct of Sylvius ( Duct which connects the IIIrd Ventricle in the midbrain , with the IVth Ventricle in the pons & Medulla ) into :-
- 25. It is Divided into two parts - i] Ventral Part, called Cerebral Peduncle , chiefly of white matter, uniting the Pons with the thalamic region of the cerebrum. It comprises the – tegmentum, Substantia nigra & basis peduncle. ii] Dorsal part, called tectum which constitutes two elevations, superior and inferior colliculi.
- 26. 3.HindBrain (Rhombencephalon) It comprises Pons Metencephalon Cerebellum Medulla Oblongata – Myelencephalon
- 27. BrainStem - Midbrain, Pons & Medulla Oblongata together constitute brainstem . All cranial nerves are situated in the brainstem. i). In the Midbrain – III & IV nerves. ii). In the Pons – V, VI, VII & VIII nerves, iii)). In the Medulla – IX , X , XI & XII nerves.
- 29. The cerebellum is connected by three large bundles of nerve fibres, the cerebellar peduncles with the dorsal side of the brain stem : i). Via Superior Cerebellar Peduncle with the midbrain, ii) via Middle cerebellar Peduncle with the pons ,& iii) Via Inferior cerebellar Peduncle with
- 31. Running through the core of the brain stem and consisting largerly of neuron cell bodies (i.e.grey matter), is the reticular formation .
- 32. The Spinal Cord Spinal cord is a long (approx. 45- 50cm in length) , narrow (about 2cm in diameter) cylindrical structure. It lies outside the skull Beginning in the base at the foramen magnum Terminate at the lower border of 1st lumbar vertebra.
- 33. Below the 1st lumbar vertebra the spinal cord contains the lumbar & Sacral roots in bands, known as Cauda Equina (or horse tail).
- 34. Cross – section of Spinal Cord Anteriorly – fissure Posteriorly – Sulcus In the centre – central canal Inner side – grey matter (Butterfly shaped or H shaped). Outer side – White matter.
- 35. Inner side – grey matter (Butterfly shaped or H shaped). Horns are present –a. Anterior/ventral horn. b. Posterior/Dorsal horn. c. lateral horn. Around the central canal , grey commissure of spinal cord.
- 36. The Dorsal or posterior horn – receives the fibers of the posterior roots which are purely sensory in function . Their cell bodies are found in the dorsal root ganglion . The Ventral or Anterior horn – receive motor neurons from ventral/anterior nerve root. These nerve fibers are purely motor in function.
- 37. Major columns of Spinal Cord 1. Dorsal / Posterior Column 2. Anterolateral / ventrolateral column
- 38. 1.Dorsal / Posterior Column It consists of Ascending Tracts or Sensory nerve fibers. Most advanced system. Highly myelinated . Highly insulated – only limited sensations are sensed. Carry sensations very fast. High – velocity system . Well developed advanced sensations are present in this column.
- 39. Examples of Dorsal column sensations- Very fine touch sensation, Sense of positioning, Pressure Sense of Proprioreception – from locomotor system. Sense of two point Discrimination.
- 40. 2. Anterolateral / ventrolateral column It contain both Ascending & Descending tracts. It is a Primitive – Tract System. It is poorly / Moderately Myelinated. It is a slow Velocity System. All the primitive Sensations are present. Variety of sensations are Present.
- 41. Example ventrolateral column- Crude touch , Sensation of Itching, Sexual sensation Tickling sensation Pain Temp .
- 42. Peripheral Nervous System The part of the Nervous System which lies outside the CNS. It consists of the nerves extending from the brain & Spinal Cord out to all parts of the body.
- 43. Peripheral Nervous System Sensory P.N.S. a.General Senses b.Special Senses i.Somatic Sensation ii.Visceral Sensations Motor P.N.S a.Voluntary NS (Somatic NS) b.Involunatry NS (Autonomic NS)
- 44. General Sensations –can be sensed through multiple parts of body. E.g Touch A.Somatic Sensations Sensations from superficial areas of body such as Skin, subcutaneous tissues. Senses such as Pain,Temp. & Proprioreception – all the sensations which are coming from locomotor system, especially sense of positioning . B.Visceral Sensations Senses from deeper part of body i.e.from viscera to C.N.S. Examples – Dull pain Abdominal distension Spleenomegaly Hepatomegaly Blood pressure.
- 46. Motor P.N.S. a.Voluntary NS (Somatic NS) controlled by Skeletal muscles. Running . Hand shaking. b. Involunatry NS (Autonomic NS) Smooth muscles & Cardiac muscles. Glandular activities Sense of smell. Salivation etc.
- 47. a. Voluntary / Somatic NS – made up of all the nerve fibers going from CNS to the skeletal muscle cells. It comprises spinal & cranial nerves. 31 pairs of Spinal nerves 12 pairs of Cranial nerves.
- 48. Involunatry / Autonomic NS The innervation of all tissues other than skeletal muscle is by way of the ANS. Also called Vegetative nervous system. It has two divisons – 1. Sympathetic Division – consists of thoracic & lumbar ganglia , also called Thoraco – Lumbar division. 2. Parasympathetic Division – consists of cranial & sacral ganglia , also called craniosacral division.
- 49. (Involuntary Motor Response) Autonomic Nervous System Sympathetic Nervous System Stress Heart rate increases. Parasympathetic Nervous System Relax Heart rate decreases.
- 51. Meninges
- 52. Meninges -These are the membranous coverings of C.N.S. These are fibrous connective tissues.
- 53. Brain and spinal cord are surrounded by three layers of meninges. Outer - Dura mater, Middle - Arachnoid mater & Inner - Pia mater.
- 54. The space between arachnoid mater and pia mater is known as subarachnoid space. This space is filled with a fluid called cerebrospinal fluid. Brain and spinal cord are actually suspended in the cerebrospinal fluid.
- 55. Pia Mater - Pia = Soft. Mater = Mother. Inner most connective tissue layer. Highly vascular. Very thin & delicate. Closely covering all the surfaces of brain & Spinal Cord.
- 56. Arachnoid Mater - Arachnoid = Spider like. Present outside the Pia Mater. Connected to pia mater through Trabecula. Relatively Non – Vascular.
- 57. Dura Mater - Dura = Tough Mater = Mother. It is very tough & Strong . Avascular .
- 58. In Relation to Skull – Dura Mater has two layers – A. Periosteal Layer – stick to skull bone . Outer layer. B. Meningeal Layer – inner Layer. Periosteal layer as a part of Skull bone.
- 60. Physiologically these two layers are close to each other. Dural Venous Sinus – these two layers are separated from each other at some places. V – shaped space is formed. Lined by endothelial cells. Venous blood is running.
- 61. Meningeal vessels/ Arteries & veins are present between Skull bone/Periosteal Layer & Meningeal layer of dura mater in temporal region. Supply blood to meninges .
- 62. Dural Folds Falx Cerebri – A double fold of dura mater passes through interhemispheric fissure. - Separating two cerebral hemisphere. Tentorium Cerebelli – Continuation of falx cerebri above the roof of cerebellum . It separates occipital & temporal lobes of cerebrum from cerebellum & Brainstem. Falx Cerebelli – in between cerebellum hemisphere.
- 64. 1. Epidural Hemorrhage - Epidural Hematoma/bleeding. Collection of blood between skull/periosteal layer & meningeal layer of dura mater. Dura mater is tightly connected to suture. Lens shaped/Biconvex shaped hemorrhage is
- 65. Cause of Epidural Hemorrhage - occur due to trauma to the skull ,mostly on temporal side. There is rupture of meningeal arties & veins.
- 66. 2. Subdural Hemorrhage - Collection of blood below the dura mater/outer layer of dura mater & Arachnoid membrane. Cause- injury to cerebral vein. Cresent/sickle shaped hemorrhage with H/O fall after intoxication or injury due to neck movement (with increasing age = grey mater shrinks) Cerebral vein passes through – pia mater- arachnoid matter – dura mater- dural veinous sinus.
- 68. 3. Sub- Arachnoid Hemorrhage - Below Arachnoid membrane or between Pia Mater & Arachnoid membrane. Occur due to rupture of cerebral Aneurysm.
- 69. Lumbar Puncture at the level of L3-L4 & L4-L5 – Confirmation of Sub- Arachnoidal Hemorrhage. (blood & C.S.F)