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Nervous system
- 1. NERVOUS SYSTEM Miss Diptee Gupta D.Pharm,B.Pharm Assistant Professor SRLT Group of institute, Ekdil, Etawah
- 2. Nervous systemis one of the smallest and the most complex system of body. It constitute 2kg or 3% body mass of total human body mass. It consist of nerve cells that carry message to and from the brain and spinal cord to various parts of body. NOTE- NEUROLOGY is the branch of medical science that deals with normal functioning and disorders of nervous system. NEUROLOGIST is the physician who diagnose the disorder disorder of neuromuscular system.
- 3. FUNCTION OFNERVOUS SYSTEM- Maintain homeostasis in body Send and receive message within body. Respond to stimuli. Controls and coordinate the function throughout the body
- 4. CNS PNS BRAIN SPINALCORD SENSORY DIVISION MOTOR DIVISIO N ANS(INVOLUNTAR Y SNS(VOLUNTAR Y SYMPATHETI C (FIGHT or FLIGHT) PARA SYMPATHETIC(R EST or DIGEST)
- 5. CELLS OFNERVOUS SYSTEM- It consist of 2 type of cells- a) NEURONS (NERVE CELLS) b) NEUROGLIA. A) NEURONES- These are basic element of nervous system. It consist of following 3 parts- CELL BODY DENDRITES AXON.
- 6. 1) CELL BODY-It form the grey matter of nervous system. It is the main processing centre of nerve cell. 2) DENDRITES – These are extensions of cell body and form white matter of nervous system. It get information from other cells and carry towards the cell body. 3) AXON/NERVE FIBRE-It is a long slender projection of nerve cell. Each nerve cell has only one axon. It carry impulse away from cell body. It is surrounded by a segmented wrapping of a material known as MYELIN SHEATH. The sheath broken at regular intervals known as NODE OF RANVIER.
- 7. NOTE- In PNSSCHWANN CELL responsible for formation of myelin sheath while in CNS OLIGODENDROGLIA CELLS responsible for formation of myelin sheath. TYPES OF NERVE FIBRE- A) MYELINATED NERVE FIBRE- It have large axons which are covered by myelin sheath. B) NON MYELINATED NERVE FIBRE- Post ganglionic fibre and small nerve fibre in the CNS are not covered by myelin sheath.
- 8. PROPERTIES OF NERVEFIBRE- 1) EXCITABILITY- Nerve fibres are highly excitable. When stimulus is applied , it show a change in its electrical activity from its resting stage. 2) CONDUCTIVITY- It is ability of nerve fibre to transmit impulses along its entire length to axon terminal. 3) REFRACTORY PERIOD- During action potential the excitability of nerve become reduced i.e. new impulse cannot be generated during a action potential.
- 9. 4)ALL OR NONELAW- A neurone either conduct an impulse of full strength or does not conduct an impulse, known as all or none response.
- 10. NEUROGLIA The neurones ofCNS are supported by 4 type of non excitable glial cells which does not specialized in transmission of nerve impulse. It support, protect, connect & remove debris from nervous system.
- 11. In CNS neurogliacells are as- Astrocytes, olingodendrocytes, Microglia & ependymal cells. In PNS it include- Schwann cells & Satellite cells.
- 12. NERVE IMPULSE Itis an electrical signal that travels along an axon. There is an electrical difference between the inside of axon and its surroundings. When the nerve is activated, there is a sudden change in the voltage across the wall of axon, caused by movements of ions in and out of neurone. This triggers a wave of electrical activity that passes from the cell body along the length of axon to the synapse.
- 13. ELECTROPHYSIOLOGY It isthe branch of physiology that studies the electrical properties of biological cells and tissues. It involve measurement of voltage changes or electrical heart on a wide variety of scales from single ion channel proteins to whole organs like heart.
- 14. SYNAPSE - More thanone neurone involve in the transmission of a nerve impulse from its origin to its destination. The point at which the nerve impulse passes from one to another is synapse. Structurally they are 2 type of synapse- a)Electrical synapse( across the gap junction) b)Chemical synapse( across the synaptic cleft)
- 15. NEUROTRANSMITTERS These are chemicalagents which are released by neurones in the synaptic cleft to rapidly stimulate or inhibit the post synaptic neurones. Classification- They are as follows-
- 16. NEUROTRANSMITTERS Acetylcholine Biogenic amines Nitric oxide Amino acids neurotransmitters Peptide Miscellaneous neurotransmitter Dopamine Noradrenaline 5Hydroxytryptamine Excitatory-Glutamate, Aspartate Inhibitory- GABA, Glycine
- 17. Central nervous system It consistof Brain and spinal cord. its main function to get the information from body and send instructions.
- 18. Meninges It lie betweenthe skull and the brain & the vertebral foramina and spinal cord. The brain and spinal cord are completely surrounded by 3 membranous covering- a) Dura mater (the outer ) b) Arachnoid (the middle) c) Pia mater ( the inner)
- 19. A) Dura mater(the outer )- It is tough outer layer lying just inside the skull and vertebrae. In the brain it possess Dural sinuses which contain venous blood returning from the brain. In the spinal cord space between Dura mater and vertebrae known as epidural space which act as a protective cushion for it.
- 20. B) Arachnoid (themiddle)- It is a layer of fibrous tissue. it is separated from duramater by SUBDURAL SPACE and from piamater by SUBARACHNOID SPACE. The SUBARACHNOID SPACE contain blood vessel and circulate CSF. c) Pia mater ( the inner)- It tightly cover the brain and spinal cord. It carries blood vessels that provide nourishment to these nervous tissue.
- 21. VENTRICLES OF BRAIN- The braincontain 4 irregular shaped cavities called ventricles. They are filled with CSF. They are- a) right and left lateral ventricle b) third ventricle c) fourth ventricle
- 22. A) RIGHT ANDLEFT LATERAL VENTRICLE – These occupies a cerebral hemisphere and present one on each side.It connect with third ventricle by INTERVENTRICULAR FORAMINA. B) THIRD VENTRICLE- It lie in middle tubular space of diencephalon.it connect with fourth ventricle by a canal called CEREBRAL AQUEDUCT. C) FOURTH VENTRICLE- It lie between the cerebellum and pons. It continues below with the central canal of spinal cord. By these opening CSF enters the SUBARACHNOID SPACE.
- 23. CEREBROSPINAL FLUID(CSF) In theeach ventricle of brain, a network of capillaries CHOROID PLEXUS secrete CSF. These capillaries are surrounded by ependymal cells. Blood plasma entering these cells from capillaries is filtered and passes to ventricles forming CSF. CIRCULATION- It circulate from the lateral ventricles to the third and then fourth ventricles from there most of the CSF passes into SUBARACHNOID SPACE and some passes in to central canal of spinal cord.it is reabsorbed into blood by arachnoid villi located in Dural sinuses of meninges.
- 24. It is secretedcontinuously at a rate of about 0.5ml/minute i.e. 720ml/day. CSF is reabsorbed as rapidly as it forms so the pressure of CSF normally is constant. COMPOSITION- it is a clear, colourless, slightly alkaline fluid. It contains- water, mineral salts, glucose, creatine and urea (in small amount), and electrolytes. FUNCTIONS- it acts as a cushion or shock absorber for brain and spinalcord.it act as a medium for the exchange of nutrients & waste products between CSF and nerve cells. It support and protect the brain & spinal cord by maintaining a uniform pressure.
- 25.
- 26. BRAIN- It isthe portion of CNS that lies within the cranial cavity. It constitute about 2% of total body weight. The human brain weigh approx. 1300g in adults.
- 27. DEVELOPMENT OF BRAIN Duringthe early embryonic development, the neural tube of embryo expand and form 3 primary brain vesicles- a) forebrain b) Midbrain c) Hindbrain During the development of these structure, adult brain form and many structure develop.
- 28. FLOW CHART SHOWINGBRAIN DEVELOPMENT
- 29. MAJOR PARTS OFBRAIN The human brain is a very complex system. It comprise of following parts- A)Cerebrum B) diencephalon C) Brain stem D) Cerebellum
- 30. CEREBRUM It isknown as SENSE OF INTELLIGENCE. It provide us the ability to read, write & speak, to make calculations, compose music & to remember past, plan for future and imagine things. It is the largest and most visible part of brain. It occupies the anterior and middle cranial fossa. It show many folded ridges called grooves. The deepest grooves between the folds are called FISSURES and the shallower grooves called SULCI. It consist of 2 cerebral hemisphere(right & left) connected by a bundle of nerve called CORPUS CALLOSUM.
- 31. LOBES OF CEREBRUM Eachlobe of cerebral hemispheres has 4 lobes which are on the names of cranial bones- o Frontal, o Temporal o Occipital o Parietal The boundaries of lobes are marked by deep sulci which are central, lateral, & parieto-occipital. .
- 32. CEREBRAL TRACT- thesurface of cerebral cortex is composed of grey matter(nerve cell bodies).with in the cerebrum lobes makeup the white matter of brain. BASAL GANGALIA- In each cerebral hemispheres there are several group of nuclei. They act as relay station with connection to many parts of brain. Their functions include initiation & termination of movements and learned coordinated activities such as posture or walking
- 33. Limbic system- Aring of structure on the inner border of cerebrum & floor of diencephalon constitute the limbic system. Its function are as- it controls emotional behaviour expressed in the form of joy , sorrow, fear, friendship, fight etc. it control food habits necessary for survival of an individual.
- 34. FUNCTION OF CEREBRUM-It involve in mainly 3 type of activities- 1) Mental activities involved in memory, intelligence, sense of responsibility, thinking, reasoning, moral sense & learning. 2)Sensory perception including perception of pain, temperature, touch, sight, hearing, taste & smell 3)Initiation and control of skeletal muscle contraction & voluntary movement.
- 35. BRAIN STEM It islocated b/w the cerebrum & spinal cord.it provide a pathway for tracts running between higher & lower neural centres. It consist of- a) Midbrain b) Pons c) Medulla oblongata .
- 36. MID BRAIN It isarea of brain lying around the cerebral aqueduct b/w the cerebrum above & pons below. It consist of nuclei and nerve fibres which connect to cerebrum with lower parts of brain with spinal cord. The nuclei act as relay station for the ascending & descending nerve fibres.
- 37. PONS It is about2.5cm long superior to medulla & anterior to cerebellum. It consist of both nuclei and nerve fibres ( tracts). Nerve fibres form a bridge b/w the 2 hemispheres of cerebellum. Nuclei within pons act as a relay station & associated with following cranial nerve- trigeminal(V), abducens, facial, & vestibulocochlear nerve. Others nuclei in the pons are pneumotaxic & apneustic centre which regulate the breathing
- 38. MEDULLA OBLONGATA- It extends fromthe pons above & is continuous below with the spinal cord. It lies just within cranium above the foramen magnum. Its anterior and posterior surface is marked by central fissures.
- 39. The outer surfaceis composed of grey matter and in central white matter. It also contain various vital centre which associate with autonomic reflex activity. These are the- Cardiovascular centre Respiratory centre Reflex centre of vomiting, coughing, sneezing & swallowing. Note- In the medulla motor nerves descending from the motor area in the cerebrum to spinal cord in the tracts crosses from one side to another. It means that left hemisphere of body control the right half of body and so on.
- 40. RETICULAR FORMATION A largepart of brain stem consist of small areas of grey and white matter called reticular formation. It help to maintain consciousness, cause awakening from sleep and help to regulate muscle tone.
- 41. CEREBELLUM It is lyingbehind the pons and immediately below the posterior portion of cerebrum. It occupies a posterior cranial fossa. It is ovoid in shape and has 2 hemispheres which are separated by a narrow median strip called vermis. Grey matter forms the surface of cerebellum and the white matter lies deeply.
- 42. Functions- It control andcoordinate the movements of various groups of muscles. It coordinate the activities like the maintenance of posture, balance & equilibrium. It also have a role in learning and language processing.
- 43. DIENCEPHALON- It extend fromthe brain stem to the cerebrum and surround the third ventricle. It include thalamus and hypothalamus. The pineal gland and optic chiasma are situated here. THALAMUS- It makes up 80 % of diencephalon. It consist of 2 masses of grey and white matter. Sensory receptor in the skin send information about touch, pain, temperature input from sensory organs travel to the thalamus. It transfer it to other parts of brain. It relays and redistribute impulses from most parts of brain to cerebral cortex.
- 44. HYPOTHALAMUS- It is asmall but a very imp structure. It weigh around 7g. It consist of a no. of nuclei. Its function include control of- output of hormones from both lobes of pituitary gland The ANS, appetite and satiety Thirst and water balance Body temp. emotional reactions , sexual behaviour & child rearing Sleeping and walking cycles.