1. 1 NERVOUS SYSTEM DR :WAHEEB AGGAD

2. 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:.2-It is formed of highly specialized nerve cells (neurons) which can: receive stimuli (from receptors scattered all over the body) receive stimuli (from receptors scattered all over the body) and deal with them and deal with them and finally send the proper impulses to the effectors which could be muscles or glands.

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

4. 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 : Neuron is the term given to the nerve cell and all its processes. It is formed of : A) cell body has nucleus A) cell body has nucleus B) two types of processes, 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 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. 2)Dendrites are multiple,the short processes of the cell body, which carry impulses to wards the cell body.

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6. 6 Divisions of the Nervous System The nervous system is divided into The nervous system is divided into two main parts: 1) The central nervous system 1) The central nervous system 2) The peripheral nervous system 2) The peripheral nervous system

7. 7 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: 1-The central nervous system is the part of N.S which is protected by bones,it is consists of: a) The brain a) The brain b) spinal cord b) spinal cord

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9. 9 A) The brain It is formed of : It is formed of : a) cerebrum ( the 2 cerebral hemispheres+ the interbrain). a) cerebrum ( the 2 cerebral hemispheres+ the interbrain). b) Brain stem: which includes: b) Brain stem: which includes: Midbrain ( upper part) Midbrain ( upper part) Pons (middle part) Pons (middle part) medulla oblongata (lower part) medulla oblongata (lower part) c)cerebellum c)cerebellum

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11. 11 A) The brain it is covered by 3 meninges : 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). It contains cavities (Ventricles).

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14. 14 A) The brain In cross sections, it shows: In cross sections, it shows: a)Grey matter :dark areas which contains the cell bodies. 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 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. 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). b) White matter :light areas which contain nerve fibers (axons). The fibers run inside the C.N.S.as bundles or tracts. The fibers run inside the C.N.S.as bundles or tracts.

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16. 16 B) The spinal cord The spinal cord The spinal cord Covered by3 meninges like the brain. Covered by3 meninges like the brain. Contains cavity called the central canal. Contains cavity called the central canal.

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18. 18 B) The spinal cord In cross section,it shows: In cross section,it shows: a) Grey matter: it is arranged in the shape of butter fly or like letter H. 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). 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. 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. B) White matter : surrounds the grey matter and contains nerve fibers which run as tracts.

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21. 21 B) The spinal cord The cord is divided into segments (31): The cord is divided into segments (31): a-cervical segments:8. a-cervical segments:8. b-Thoracic segments :12. b-Thoracic segments :12. c-Lumber segments :5. c-Lumber segments :5. d- Sacral segments :5. d- Sacral segments :5. e- Single Coccygeal. e- Single Coccygeal. N:B.: The right and left parts of the C.N.S. are connected together by nerve fibers called commissures. N:B.: The right and left parts of the C.N.S. are connected together by nerve fibers called commissures.

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23. 23 2-The peripheral nervous system The peripheral nervous system, It is not protected by bones, The peripheral nervous system, It is not protected by bones, It is divided functionally into : It is divided functionally into : a-Somatic nervous system :carries sensations and controls skeletal muscles. a-Somatic nervous system :carries sensations and controls skeletal muscles. b-Autonomic nervous system :Controls smooth muscle,heart &glands. b-Autonomic nervous system :Controls smooth muscle,heart &glands.

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25. 25 A-The Somatic nervous System The Somatic nervous System : which formed of : The Somatic nervous System : which formed of : a) cranial nerves :12 pairs of nerves which arise from the brain. 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. b) spinal nerves: 31 pairs of nerves and their associated ganglia which arise from the spinal cord,a pair arises from each segment.

26. 26 A-The Somatic nervous System a)Cranial Nerves a)Cranial Nerves There are 12 pairs of cranial nerves that leave the brain and pass through foramina in the skull. 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. ). All the nerves are distributed in the head and neck except the Xth (vagus), which also supplies structures in the thorax and abdomen. ).

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28. 28 A-The Somatic nervous System B) Spinal Nerves 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: The spinal nerves are named according to the region of the vertebral column with which they are associated: 8 cervical, 8 cervical, 12 thoracic, 12 thoracic, 5 lumbar, 5 lumbar, 5 sacral, and 5 sacral, and 1 coccygeal. 1 coccygeal. ). ).

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30. 30 A-The Somatic nervous System N:B 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? 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 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

31. 31 B) Spinal Nerves Each spinal nerve is connected to the spinal cord by two roots: Each spinal nerve is connected to the spinal cord by two roots: A) the anterior root and A) the anterior root and B) the posterior root. B) the posterior root.

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33. 33 B) Spinal Nerves 1)The anterior root (Efferent fibers ) 1)The anterior root (Efferent fibers ) consists of: Motor fibers, arises from the anterior horn of gray matter of the spinal cord. 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 carrying motor impulses from the central nervous system to skeletal muscle and cause them to contract

34. 34 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. 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 The cell bodies of these nerve fibers are situated in a swelling on the posterior root called the posterior root ganglion

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37. 37 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. 3)posterior root ganglion :each posterior root carries posterior root ganglion which contains an aggregation of cell bodies situated in a swelling.

38. 38 B) Spinal Nerves At each intervertebral foramen, the anterior and posterior roots unite to 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. 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 : On emerging from the foramen, the spinal nerve divides into 2 rami :.

39. 39 B) Spinal Nerves 1)Anterior ramus : 1)Anterior ramus : it is a large mixed nerve. 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. 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. 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 The ventral rami are connected to the sympathetic chain by rami communicantes

40. 40 B) Spinal Nerves 2)posterior ramus : 2)posterior ramus : It is a smaller mixed nerve. 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 posterior ramus passes posteriorly around the vertebral column to supply the muscles and skin of the back. The dorsal rami do not form plexuses The dorsal rami do not form plexuses

41. 41 The Somatic nerve plexuses: 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. 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. 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. N.B.: the 12 thoracic ventral rami do not form plexus.

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43. 43 Functionally, the nervous system can be further divided into : the somatic nervous system, which controls voluntary activities. the somatic nervous system, which controls voluntary activities. the autonomic nervous system, which controls involuntary 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. The nervous system, together with the endocrine system, controls and integrates the activities of the different parts of the body.

44. 44 SUMARY TO N.S Central Nervous System Central Nervous System The central nervous system is brain( cerebral hemisphere+ 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, b) their processes, c) supported by specialized tissue called neuroglia. c) supported by specialized tissue called neuroglia. the peripheral nervous system can be further divided into : the peripheral nervous system can be further divided into : a-the somatic nervous system, which controls voluntary activities. a-the somatic nervous system, which controls voluntary activities. a) 12 pairs of cranial nerves and a) 12 pairs of cranial nerves and b)31 pairs of spinal nerves and their associated ganglia. b)31 pairs of spinal nerves and their associated ganglia. b- the autonomic nervous system, which controls involuntary activities. 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. The nervous system, together with the endocrine system, controls the activities of the different parts of body.

45. 45 2-Autonomic Nervous System

46. 46 2-Autonomic Nervous System 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. 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. It is distributed throughout the central and peripheral nervous system.

47. 47 2-Autonomic Nervous System The autonomic system The autonomic system divided into two parts 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, Both systems have antagonistic functions but they are complementary to each other. To control the muscles & glands,

48. 48 2-Autonomic Nervous System The autonomic nervous system need 2 sets of neurons : 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. 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. 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. A ganglia means a collection of neurons (cell bodies ) out side the CNS..In the ganglia the pre & Postganglionic neurons meet by making Synapse..In the ganglia the pre & Postganglionic neurons meet by making Synapse.

49. 49 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). 1. 1. accelerates the heart rate, causes constriction of the peripheral blood vessels, and raises the blood pressure. 2. 2. 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. 3. 3. Dilatatios of the pupil. 4. 4. Stimulation of sphincters of gut. 5. 5. Erection of hairs. 6. 6. sweating

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51. 51 Sympathetic System : It is formed of : : It is formed of : 1) pre ganglionic fibers: 1) pre ganglionic fibers: Arise from neurons of the lateral horn of the The gray matter of the spinal cord, in the following segment : Arise from neurons of the lateral horn of the The gray matter of the spinal cord, in the following segment : 1)all thoracic segment 1)all thoracic segment 2) the first and the second lumbar segment,SO,the name thoraco lumber outflow 2) the first and the second lumbar segment,SO,the name thoraco lumber outflow

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54. 54 the preganglionic fibers The axons of these cells leave the spinal cord in the The axons of these cells leave the spinal cord in the anterior roots, nerve trunk,ventral ramus of the corresponding spinal nerve. anterior roots, nerve trunk,ventral ramus of the corresponding spinal nerve. Finally,the preganglionic fibers leave the ventral ramus as the white rami communicantes to the ganglia of the sympathetic chain. Finally,the preganglionic fibers leave the ventral ramus as the white rami communicantes to the ganglia of the sympathetic chain.

55. 55 Once the preganglionic fibers reach the ganglia in the sympathetic chain, they may pass to the following destinations by dividing into: a- Ascending group: These are fibers W make synapses with the cell bodies of upper ganglia of the chain. a- Ascending group: These are fibers W make synapses with the cell bodies of upper ganglia of the chain. b- Transverse group: These are fibers W make synapses with the cell bodies of same level ganglia of the chain. b- Transverse group: These are fibers W make synapses with the cell bodies of same level ganglia of the chain. c- descending group: These are fibers W make synapses with the cell bodies of lower ganglia of the chain. c- descending group: These are fibers W make synapses with the cell bodies of lower ganglia of the chain. N.B.: SOME pre ganglionic fibers do not make synapse with sympathetic chain,Instead,they reach other distal sympathetic ganglia,e.g., Coeliac ganglion where they relay.

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57. 57 2-The postganglionic nerve fibers The postganglionic nerve fibers: they are the axons of the cell bodies of sympathetic ganglia. The postganglionic nerve fibers: they are the axons of the cell bodies of sympathetic ganglia. They pass from the sympathetic ganglia to reach different parts of the body by one of 3 methods : They pass from the sympathetic ganglia to reach different parts of the body by one of 3 methods : 1) by rejoining the ventral &dorsal rami to be distributed via them. 1) by rejoining the ventral &dorsal rami to be distributed via them. The connection between the ganglia &ventral rami are called gray rami communicantes. The connection between the ganglia &ventral rami are called gray rami communicantes. They are distributed in the branches of the spinal nerves to supply the smooth muscle in the walls of blood vessels, the sweat glands, and the erector pili muscles of the skin. They are distributed in the branches of the spinal nerves to supply the smooth muscle in the walls of blood vessels, the sweat glands, and the erector pili muscles of the skin. 2)By passing along the blood vessels. 2)By passing along the blood vessels. 3)By reaching the viscera directly. 3)By reaching the viscera directly. 

58. 58 3) Sympathetic chains 1.. Sympathetic trunks are two ganglionated nerve trunks that extend the whole length of the vertebral column 2..There are 3 ganglia in each trunk of the neck, 11 or 12 ganglia in the thorax, 4 or 5 ganglia in the lumbar region, and 4 or 5 ganglia in the pelvis. 3. The two trunks lie close to the vertebral column and end below by joining together to form a single ganglion, the ganglion impar.

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60. 60 2) Parasympathetic System

61. 61 2) The Functions of the Parasympathetic System parasympathetic part of the autonomic system conserving and restoring energy. i.e., parasympathetic part of the autonomic system conserving and restoring energy. i.e., rebuilding the body resources during rest : 1. They slow the heart rate 2. increase peristalsis of the intestine and glandular activity, and open the sphincters. 3. constriction of the pupil. NB.The hypothalamus of the brain controls the autonomic nervous system and integrates the activities of the autonomic and neuroendocrine systems, thus preserving homeostasis in the body

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63. 63 2) Parasympathetic System It is formed of: It is formed of: 1)The preganglionic fibers: 1)The preganglionic fibers: They arise from CNS in 2 sites : They arise from CNS in 2 sites : 1. with the cranial nerves number 10,9,7,3. 2. From the neurons of the lateral horn of sacral spinal segments number 2,3,4. SO the name cranio -sacral outflow. leave the spinal cord in the anterior roots of the corresponding spinal nerves. They then leave the sacral nerves and form the pelvic splanchnic nerves. SO the name cranio -sacral outflow. leave the spinal cord in the anterior roots of the corresponding spinal nerves. They then leave the sacral nerves and form the pelvic splanchnic nerves.

64. 64 2) Parasympathetic System 2 -peripheral ganglia: The preganglionic fibers synapse with cells in peripheral ganglia, which are usually situated close to the viscera they innervate. The preganglionic fibers synapse with cells in peripheral ganglia, which are usually situated close to the viscera they innervate. The cranial preganglionic fibers relay in (4 cranial Para sympathetic ganglia )the ciliary, pterygopalatine, submandibular, and otic ganglia. The cranial preganglionic fibers relay in (4 cranial Para sympathetic ganglia )the ciliary, pterygopalatine, submandibular, and otic ganglia. The preganglionic fibers in the pelvic splanchnic nerves relay in ganglia in the hypogastric plexuses or in the walls of the viscera. The preganglionic fibers in the pelvic splanchnic nerves relay in ganglia in the hypogastric plexuses or in the walls of the viscera.

65. 65 3)The postganglionic fibers : The post ganglionic Para sympathetic fibers (The axons of the cell bodies inside the ganglia ) leave the ganglia to reach their targets. The post ganglionic Para sympathetic fibers (The axons of the cell bodies inside the ganglia ) leave the ganglia to reach their targets.

66. 66 N.B. 1) peripheral nerves can regenerate if injured. 1) peripheral nerves can regenerate if injured. 2) peripheral nerves are either : 2) peripheral nerves are either : a-Motor ( Efferent):if they carry orders,e.g., to a gland or muscle. a-Motor ( Efferent):if they carry orders,e.g., to a gland or muscle. b-Sensory (Afferent) : if they carry sensations,e.g., pain or touch. b-Sensory (Afferent) : if they carry sensations,e.g., pain or touch. c- Mixed: if they contain both motor &sensory fibers. c- Mixed: if they contain both motor &sensory fibers.

67. 67 Clinical Notes Clinical Modification of the Activities of the Autonomic Nervous System Clinical Modification of the Activities of the Autonomic Nervous System Many drugs and surgical procedures that can modify the activity of the autonomic nervous system are available. Many drugs and surgical procedures that can modify the activity of the autonomic nervous system are available. For example, drugs can be administered to lower the blood pressure by blocking sympathetic nerve endings and causing vasodilatation of peripheral blood vessels. For example, drugs can be administered to lower the blood pressure by blocking sympathetic nerve endings and causing vasodilatation of peripheral blood vessels. In patients with severe arterial disease affecting the main arteries of the lower limb. In patients with severe arterial disease affecting the main arteries of the lower limb.