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NERVOUS SYSTEM

NERVOUS SYSTEM. DR :WAHEEB AGGAD. Nervous system. 1-It is a system which monitor the changes in the external and internal environment and start dealing with them .2-It is formed of highly specialized nerve cells (neurons) which can:

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NERVOUS SYSTEM

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  1. NERVOUS SYSTEM DR :WAHEEB AGGAD

  2. Nervous system 1-It is a system which monitor the changes in the external and internal environment and start dealing with them .2-It is formed of highly specialized nerve cells (neurons) which can: receive stimuli (from receptors scattered all over the body) and deal with them and finally send the proper impulses to the effectors which could be muscles or glands.

  3. N.B • 3)The C.N.S can't regenerate if injured.

  4. 4) .The functional unit of the Nervous System is the neuron. • Neuron is the term given to the nerve cell and all its processes. It is formed of : • A) cell body has nucleus • B) two types of processes, called an axon and dendrites. • 1) the axon is, single, the longest process of the cell body ,carries nervous impulses away from the cell body. out side the CNS, the axons(nerve fibers) runs in groups forming the different nerves of the body • 2)Dendrites are multiple ,the short processes of the cell body, which carry impulses to wards the cell body.

  5. Divisions of the Nervous System • The nervous system is divided into two main parts: • 1) The central nervous system • 2) The peripheral nervous system

  6. 1-The central nervous system, • 1-The central nervous system is the part of N.S which is protected by bones ,it is consists of: • a) The brain • b) spinal cord

  7. A) The brain • It is formed of : • a) cerebrum ( the 2 cerebral hemispheres+ the interbrain). • b) Brain stem: which includes: • Midbrain ( upper part) • Pons (middle part) • medulla oblongata (lower part) • c)cerebellum

  8. A) The brain • it is covered by 3 meninges : 1-Dura (the outer layer ) 2-arachnoid (the middle) 3-the pia (the inner) matters. • It contains cavities (Ventricles).

  9. A) The brain • In cross sections, it shows: • a)Grey matter :dark areas which contains the cell bodies . • The grey matter on the surface of the cerebrum is called the cerebral cortex . • The term nucleus is used to describe any collection of cell bodies which perform the same function. • b) White matter :light areas which contain nerve fibers (axons) . • The fibers run inside the C.N.S .as bundles or tracts.

  10. B) The spinal cord • The spinal cord • Covered by3 meninges like the brain. • Contains cavity called the central canal .

  11. B) The spinal cord • In cross section ,it shows: • a) Grey matter: it is arranged in the shape of butter fly or like letter H. • It projects as 2 dorsal horns (contain sensory neurons ) &2 ventral horns (contain motor neurons) . • A third lateral horn is found only in the segments which give autonomic outflow. • B) White matter : surrounds the grey matter and contains nerve fibers which run as tracts.

  12. B) The spinal cord • The cord is divided into segments (31): • a-cervical segments:8. • b-Thoracic segments :12. • c-Lumber segments :5. • d- Sacral segments :5. • e- Single Coccygeal . • N:B.: The right and left parts of the C.N.S. are connected together by nerve fibers called commissures.

  13. 2-The peripheral nervous system • The peripheral nervous system, It is not protected by bones , • It is divided functionally into : • a-Somatic nervous system :carries sensations and controls skeletal muscles . • b-Autonomic nervous system :Controls smooth muscle ,heart &glands .

  14. A-The Somatic nervous System • The Somatic nervous System : which formed of : • a) cranial nerves :12 pairs of nerves which arise from the brain. • b) spinal nerves: 31 pairs of nerves and their associated ganglia which arise from the spinal cord ,a pair arises from each segment.

  15. A-The Somatic nervous System • a)Cranial Nerves • There are 12 pairs of cranial nerves that leave the brain and pass through foramina in the skull. • All the nerves are distributed in the head and neck except the Xth (vagus), which also supplies structures in the thorax and abdomen. ) .

  16. A-The Somatic nervous System • B) Spinal Nerves A total of 31 pairs of spinal nerves leave the spinal cord and pass through intervertebral foramina in the vertebral column . • The spinal nerves are named according to the region of the vertebral column with which they are associated: • 8 cervical, • 12 thoracic, • 5 lumbar, • 5 sacral, and • 1 coccygeal. • ).

  17. A-The Somatic nervous System • N:B • Q )There are eight cervical nerves and only seven cervical vertebrae and that there is one coccygeal nerve and four coccygeal vertebrae. WHY? • A) During development, the spinal cord grows slowly than the vertebral column. In the adult, when growth STOPED, the lower end of the spinal cord reaches inferiorly only as far as the lower border of the first lumbar vertebra( L1

  18. B) Spinal Nerves • Each spinal nerve is connected to the spinal cord by two roots: • A) the anterior root and • B) the posterior root.

  19. B) Spinal Nerves • 1)The anterior root (Efferent fibers ) • consists of: Motor fibers, arises from the anterior horn of gray matter of the spinal cord. • carrying motor impulses from the central nervous system to skeletal muscle and cause them to contract

  20. B) Spinal Nerves • 2) The posterior root (Afferent fibers) consists of sensory fibers that are concerned with conveying information about sensations of( touch, pain, temperature, and vibrations ) to the central nervous system, so they are called sensory fibers ,and ends in the dorsal horn of the gray matter of the spinal cord . • The cell bodies of these nerve fibers are situated in a swelling on the posterior root called the posterior root ganglion

  21. B) Spinal Nerves • 3)posterior root ganglion :each posterior root carries posterior root ganglion which contains an aggregation of cell bodies situated in a swelling.

  22. B) Spinal Nerves • At each intervertebral foramen, the anterior and posterior roots unite to • form a Trunk of spinal nerve Here, the motor and sensory fibers become mixed together, so that a spinal nerve is made up of a mixture of motor and sensory fibers . • On emerging from the foramen, the spinal nerve divides into 2 rami : • .

  23. B) Spinal Nerves • 1)Anterior ramus : • it is a large mixed nerve . • The anterior ramus continues anteriorly to supply the muscles and skin over the anterolateral body wall and all the muscles and skin of the limbs. • It supplies those either directly or after plexuses formation with neighbouring ventral rami . • The ventral rami are connected to the sympathetic chain by rami communicantes

  24. B) Spinal Nerves • 2)posterior ramus: • It is a smaller mixed nerve . • The posterior ramus passes posteriorly around the vertebral column to supply the muscles and skin of the back. • The dorsal rami do not form plexuses

  25. The Somatic nerve plexuses: • The Somatic nerve plexuses: • Most of the ventral rami of the spinal nerves have great tendency to form nervous networks in which the nerve fibers exchanged between the neighbouring ventral rami . • At the root of the limbs, the anterior rami join one another to form complicated nerve plexuses. 1- cervical 2-brachial plexuses: supply the skin &muscles of the upper limbs. 3- lumbar 4-sacral plexuses supply the skin &muscles of the lower limbs. • N.B.: the 12 thoracic ventral rami do not form plexus .

  26. Functionally, the nervous system can be further divided into : • the somatic nervous system, which controls voluntary activities. • the autonomic nervous system, which controls involuntary activities. • The nervous system, together with the endocrine system, controls and integrates the activities of the different parts of the body.

  27. SUMARY TO N.S • Central Nervous System • The central nervous system is brain( cerebral hemisphere+ Brain stem cerebellum )+spinal cord composed of large numbers of: a) nerve cells and • b) their processes, • c) supported by specialized tissue called neuroglia. • the peripheral nervous system can be further divided into : • a-the somatic nervous system, which controls voluntary activities. • a) 12 pairs of cranial nerves and • b)31 pairs of spinal nerves and their associated ganglia. • b- the autonomic nervous system, which controls involuntary activities. • The nervous system, together with the endocrine system, controls the activities of the different parts of body.

  28. 2-Autonomic Nervous System

  29. 2-Autonomic Nervous System • 2-Autonomic Nervous System • The autonomic nervous system is the part of the nervous system concerned with the innervation of involuntary structures such as: the heart, smooth muscle , and glands throughout the body . • It is distributed throughout the central and peripheral nervous system.

  30. 2-Autonomic Nervous System • The autonomic system • divided into two parts 1)the sympathetic system . 2) the parasympathetic system. • Both systems have antagonistic functions but they are complementary to each other . To control the muscles & glands,

  31. 2-Autonomic Nervous System • The autonomic nervous system need 2 sets of neurons : • 1 - preganglionic neurons : they carry the impulses from the CNS to ganglia out side the CNS . • 2 - Postganglionic neurons : they carry impulses from the ganglia to the smooth muscles and glands. • A ganglia means a collection of neurons (cell bodies ) out side the CNS . • .In the ganglia the pre & Postganglionic neurons meet by making Synapse.

  32. 1)the sympathetic system • The Functions of the sympathetic part of the autonomic system: • prepare the body for an emergency,stress 3 f (fight ,freight,flight). • accelerates the heart rate, causes constriction of the peripheral blood vessels, and raises the blood pressure. • Redistribution of the blood so that it leaves the areas of the skin and intestine and becomes available to the brain, heart, and skeletal muscle. • Dilatatios of the pupil. • Stimulation of sphincters of gut . • Erection of hairs . • sweating

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