Introduction to Nervous System.pptx for physiology

Introduction to Nervous System.pptx for physiology

1. Introduction to Nervous System DR POTNURU SRINIVASA SUDHAKAR

2. The nervous system is the most important organization which controls and integrates the different bodily functions and likewise maintains a stability or constancy of the internal environment despite extreme changes in the external environment.

3. This system is absolutely necessary for the reception , storage and release of different sensory and motor information for regulating or initiating a particular behaviour of the individual ranging from the cellular to the gross animal being.

4. The whole nervous system can be divided into two main systems: 1 . Central nervous system. 2 . Peripheral nervous system.

5. The central nervous system consists of brain and spinal cord , whereas the peripheral nervous system consists of : ( i ) Craniospinal nerves having 12 pairs of cranial nerves and 31 pairs of spinal nerves, ( ii) visceral nervous system comprising sympathetic nervous system and parasympathetic nervous system .

6. CENTRAL OR SOMATIC NERVOUS SYSTEM The central or somatic nervous system is symmetrically arranged into two lateral halves- one-half being the mirror image of the other. It consists broadly of: 1. Spinal cord-inside the vertebral column 2. Brain-inside the cranial cavity-skull. The foramen magnum is the limiting line.

7. SPINAL CORD 1 . Spinal cord being surrounded by its covering lies loosely within the vertebral column and is extended from the foramen magnum as far down as the interspace between the 12th thoracic segment and the lower border of the 1st lumbar vertebra .

8. 2.The spinal cord is mostly cylindrical in shape and is flattened anteroposteriorly . It has got two swelling , one in cervical-6 and other in lumbar-3 of the spinal cord

9. 3. Physiologically , the spinal cord is regarded as made up of a series of superimposed segments, from each of which a pair of nerve roots arise.

10. 4. Intrinsically the spinal cord is a continuous and unsegmented structure with 31 pairs of nerves emerging from it.

11. 5. Each segment of the spinal cord gives rise to dorsal and ventral root filaments.

12. 6. Dorsal and ventral roots together form a single pair of nerves. 31 segments of the spinal cord correspond to 8 pairs of cervical and 12 pairs of thoracic , 5 pairs of lumbar and 5 pairs of sacral and 1 pair of coccygeal nerves.

13. 7. As the cord ends at the level of lower border of the 1st lumbar vertebra, spinal segments evidently do not correspond numerically with the vertebrae overlying them.

14. 8. The spinal nerves also pass at laterally to their intervertebral foramina. But later as the vertebral column develops more rapidly than the spinal cord, the segments of the latter does not correspond the respective vertebra.

15. For this reason the interval between the spinal origin of the nerve and its vertebral exit is different from segment to segment . Hence , the lumbar and sacral nerves have long roots

16. For this reason the interval between the spinal origin of the nerve and its vertebral exit is different from segment to segment . Hence , the lumbar and sacral nerves have long roots.

17. Spinal cord from its upper limit to the tip of the conus medullaris is about 45 cm in the male and 43 cm in the female. The weight of the spinal cord is about 35 gm.

18. BRAIN Brain may be subdivided as follows : 1. Medulla 2 . Pons 3 . Cerebellum

19. 1. MEDULLA It is situated in the posterior cranial fossa . It is the upward continuation of the cervical spinal cord extending from the foramen magnum to the caudal border of the pons . It is the centre for the autonomic reflex control of the circulation, heart and lungs. It is also the integrated autonomic reflex centre for swallowing, coughing , sneezing, gagging and vomiting.202

20. 2. PONS It is situated in front and above the medulla, with various nuclei and tracts. It appears anteriorly as a bulging mass of transverse fibres and is separated from the cerebellum posteriorly by the IV ventricle . Furthermore , the external feature of the pons is the broadband of predominantly transverse fibres .

21. 2. PONS It is demarcated from the cerebral peduncles of the midbrain by the superior pontine sulcus and from anterior surface of the medulla by the inferior pontine sulcus . The pons takes part in regulation of respiration and also other important vital regulations.

22. 3. CEREBELLUM Above and behind the medulla and attached to the central nervous system by three peduncles : 1.Superior , 2.middle and 3.inferior . The cerebellum is concerned with the co-ordination and adjustment of smooth movement. It is thus related with posture. Degree and extent of movement (volitional ) is determined by cerebellar feedback control .