CLASS-X EPISTODE-6 STATE SYLLABUS NERVOUS SYSTEM

Transcription

1 CLASS-X EPISTODE-6 STATE SYLLABUS NERVOUS SYSTEM In the last episode we have seen the structures and function of the components of central nervous system. In this episode we shall examine the peripheral and autonomous nervous systems. What is Peripheral nervous system? The nerves that carry impulses to and from the central nervous system constitutes the peripheral nervous system. It means that the nerves originating from brain and spinal cord are peripheral nerves. Nerves Cranial The cranial Nerves:- The nerves arising from the brain are cranical nerves. How many cranial nerves are present in man? Man has 12 pairs of cranial nerves. They are Name of the nerve Nature Controls

2 1. Olfactory Sensory smell 2.Optic Sensory Sight 3.Oculomoter Movement of eye Motor muscles & pupil 4.Trochlear Movement of one muscle Motor of the eye 5.Trigeminal Muscle for chewing sensation for gums, cheek etc. 6.Abducens Movement of one muscle of eye. 7.Facial Sense of taste, movement of facial muscle. 8.Auditory Sensory Hearing and balancing 9.Blossopharyngeal Taste, Swallowing & secretion of saliva 10.Vages Visceral secretion 11.Spinal accessory Nech & Shoulder, Moto-2 visceral reflexes. 12.Hypoglossal Moto-2 Tongue muscles How many nerves arise from the spinal cord? There are 31 pairs of spinal nerves. Each spinal nerve has two separate connection with the spinal cord. The connections are a Dorsal root which is a sensory root and a ventral root which is the motor root. The sensory fibres continue into dorsal root while the motor nerves from spinal cord continue into the ventral root. Both the roots enter the grey mater of the spinal cord and end in the respective dorsal and ventral horns of the H shaped grey mater.

3 . The 31 pairs of spinal nerves are classified into five groups. They are 1).Cervical 8 pairs Region of neck 2).Thoracic 12pairs - Region of Thorax 3).Lumbar - 5 pairs - Anterior region of abdomen 4).Sacral - 5 pairs - Posterior region of abdomen 5).Coccygeal 1pair - Region of pelvis.

4 The third part of nervous system is Autonomous nervous system. Autonomous nervous system:- The nerves of the autonomous nervous system are not in direct contact with the central nervous system. They communicate the CNS through peripheral nerves. This nervous system controls involuntary actions of some muscles and certain glands. The autonomous nervous system is unique in having pairs of chains of nerves and ganglia. What is a ganglion? A ganglion is the aggregate of the nerve cells from which the nerve fibres may arise or enter into the ganglion. Ganglion is present for each spinal nerve on either side of the back bone. They are also present in or close to the organ they control. The image that follows gives us a clear idea of the autonomous nervous system? Autonomous nervous system is divided into two systems. 1) Sympathetic 2) Parasympathetic sympathetic system:- The sympathetic nerves originate from thoraco-lumbar segment or region of spinal cord. They are involved in A).Dilation of iris b).decreasing the salivary juice secretion c).accelerating heart beat. d).increasing the respiratory rate.

5 e).relaxing the muscles of stomach, intestine and urinary bladder f).decreasing the secretions from gonads. Parasympathetic system:- The parasympathetic nerve originate from cranial and sacral segments of spinal cord. Their function is opposite that of sympathetic system They are involved in a) Constriction iris. b) Increase salivary secretion. c) Decreasing heart beat. d) Decreases respiration. e) Excitation of stomach muscles, constriction of urinary bladder f) Increases the secretion of gonads. The opposing functions of these two systems thus control and coordinate the functioning of organs and regulate the involuntary activities of an organism.