Unit 1 Nervous System.pptx by Nutan Kamble

The human nervous system is a complex of interconnected systems in which larger systems are comprised of smaller subsystems each of which have specific structures with specific functions.
The nervous system is very important in helping to maintain the homeostasis (balance) of the human body.
 A series of sensory receptors work with the nervous system to provide information about changes in both the internal and external environments. 
The Nervous system consist of vast number of cells called as Neurones.
Consist of special type of connective tissue, Neuroglia.
Neuron consist of cell body,axon,dendrites.
The neurons are actively conducting nerve impulses (action potentials).
Irritability and Conductivity- characteristics of neuron
membrane of the axon- axolemma
Large axons and those of peripheral nerves are surrounded by myelin sheath.(series of shwann cell arranged along length of axon)
Each one is wrapped around the axon so that it is covered by a number of concentric layers of Schwann cell plasma membrane.
Between layers of plasma membrane-small amt of fatty sub.-Myelin
Axons and dendrites are extensions of cell bodies & form the white matter of the nervous system.
Axons are found deep in brain and in groups,called tracts, at the periphery of the spinal cord.
Refferd as nerves or nerve fibers outside the brain and spinal cord.
he nervous system includes the brain, spinal cord, and a complex network of nerves. This system sends messages back and forth between the brain and the body. The brain is what controls all the body's functions. The spinal cord runs from the brain down through the back.The nervous system uses tiny cells called neurons (NEW-ronz) to send messages back and forth from the brain, through the spinal cord, to the nerves throughout the body.

Billions of neurons work together to create a communication network. Different neurons have different jobs. For example, sensory neurons send information from the eyes, ears, nose, tongue, and skin to the brain. Motor neurons carry messages away from the brain to the rest of the body to allow muscles to move. These connections make up the way we think, learn, move, and feel. They control how our bodies work — regulating breathing, digestion, and the beating of our hearts.In biology, the nervous system is the highly complex part of an animal that coordinates its actions and sensory information by transmitting signals to and from different parts of its body. The nervous system detects environmental changes that impact the body, then works in tandem with the endocrine system to respond to such events.[1] Nervous tissue first arose in wormlike organisms about 550 to 600 million years ago. In vertebrates, it consists of two main parts, the central nervous system (CNS) and the peripheral nervous system (PNS)The CNS consists of the brain and spinal cord. The PNS consists mainly of nerves, which are enclosed bundles of the long fibers, or axons, that connect the CNS to every other part of the body.

1. Nervous System Ms.N.S.Kamble

2. The human nervous system is a complex of interconnected systems in which larger systems are comprised of smaller subsystems each of which have specific structures with specific functions. The nervous system is very important in helping to maintain the homeostasis (balance) of the human body.  A series of sensory receptors work with the nervous system to provide information about changes in both the internal and external environments.  Four Primary Functions Of Nervous System Sensing the world -Vision, Hearing, Smell, Taste, Touch Transmitting information Processing information Producing a response The Nervous System

3. Organization of nervous system The Central Nervous System(CNS) The Peripheral Nervous System(PNS) Brain Spinal Cord Motor Neuron Sensory Neuron Somatic Nervous System Autonomic Nervous System Sympathomimetic Division Parasympathomimetic Division

4. The Nervous system consist of vast number of cells called as Neurones. Consist of special type of connective tissue, Neuroglia. Neuron consist of cell body,axon,dendrites. The neurons are actively conducting nerve impulses (action potentials). Irritability and Conductivity - characteristics of neuron Neuron

5. Cell bodies- Forms the gray matter of the nervous system and are found in a periphery of the brain and in centre of spinal cord. Groups of cell body are called as a nuclei in the CNS & ganglia in PNS. They are referred to as nerves or nerve fibers outside the brain and spinal cord. Parts of Neuron

6. Axons and dendrites are extensions of cell bodies & form the white matter of the nervous system. Axons are found deep in brain and in groups,called tracts, at the periphery of the spinal cord. Refferd as nerves or nerve fibers outside the brain and spinal cord. Axons and Dendrites

7. Each nerve cell has only one axon, carrying nerve impulses away from the cell body. They are usually longer than the dendrites, sometimes as long as 100 cm. Axons

8. Structure of an axon- membrane of the axon- axolemma Large axons and those of peripheral nerves are surrounded by myelin sheath. (series of shwann cell arranged along length of axon) Each one is wrapped around the axon so that it is covered by a number of concentric layers of Schwann cell plasma membrane. Between layers of plasma membrane-small amt of fatty sub. -Myelin

9. The outermost layer of Schwann cell plasma membrane- neurilemma . Tiny areas of exposed axolemma between adjacent Schwann cells, called nodes of Ranvier ,- assist the rapid transmission of nerve impulse in mylinated neurones .

10. Postganglionic fibres and some small fibres in the central nervous system are non- myelinated . In this type a number of axons are embedded in Schwann cell plasma membranes The adjacent Schwann cells are in close association and there is no exposed axolemma . The speed of transmission of nerve impulses is significantly slower in non- myelinated fibres .

11. The dendrites are the many short processes that receive and carry the incoming impulses towards cell bodies. They have the same structure as axons but are usually shorter and branching . In motor neurons they form part of synapses and in sensory neurons it form the sensory receptors that respond to specific stimuli Dendrites

12. On the basis of polarity/extension On the basis of function On the basis of myelin sheath classification of Neuron/Nerve Fiber

13. On the basis of polarity/extension 4 types Unipolar Neurons Bipolar Neurons Pseudo unipolar Neurons Multipolar Neurons

14. On the basis of function can be divided into three types Sensory (Afferent) neurons- organ – Brain Motor (Efferent) neurons - Brain – organ Interneurons.

15. On the basis of Myelin sheath

16. They are also known as Non-neuronal or glial cells. These are the supporting cells of neurons but do not generate or conduct nerve impulses. Unlike neurons, these cells have cell division property. Functions of neuroglia- They provide nutrition to neuron. They Protect neurons from Pathogens. They Provide structural & functional support to neurons. They form myelin sheath. They also maintains Homeostasis. Neuroglia

17. Types of Neuroglia Neuroglia peripheral Nervous System Oligodrocytes Ependymal cells Astrocytes Central Nervous System Schwann cells Microglia Satellite cells

18. Neuroglial cells in CNS- Astrocytes- These are the most abundant neuroglial cell. These are found in large number near blood vessels. These are having star shaped . They form and maintains Blood Brain Barrier.

19. Oligodendrocytes- They are smaller compare to Astrocytes. They form myelin sheath in the neurons of CNS. These are the supporting network of neurons. Ependymal cells- They form epithelial lining of brain & spinal cord & they are columnar epithelium. They secretes & absorbs CSF (cerebrospinal fluid).

20. Microglia cells These are the smallest neuroglial cells. These are derived from monocytes. They are phagocytic in nature & help in neuroglial repair.

21. Neuroglial cells in PNS- Shawann cells- These are the major glial cells in PNS. They form myelin sheath in the neurons of PNS. They are also known as neurilemma cells. Satellite cells- These are form extracellular space of nervous system They provide physical support to neurons.

22. Neurons / Nerve Fibres contains some special Properties as follows- Conductivity Excitability Refractory Period Unfatigability All or none law Accomodation Properties of Neurons/nerve fibers

23. Conductivity- It is the ability of nerve fiber to conduct nerve impulses (electrical impulses) along its length from one part to another Excitability -It is the ability of neurons / nerve fibers to respond to various stimuli & convert them into nerve impulse. Refractive Period -when the nerve fiber is once excited, it will not respond to any other stimulus for a selective time period and this time period is known as Refractive Period.

24. Unfatigability -It is the ability of nerve Fibers to get Fatigued even if they receives continuous stimuli. All or None law -It is one of the most important property of nerve Fibers, nerve fibers gets excited only at a particular threshold strength. Either they will give maximum response or they give no response. Accomodation -If the continuous stimuli is applied to the nerve Fibers then it will decrease the excitability of nerve fibers

25. Neuron is a type of cell found in our nervous System which is able to generate, carry & transmit nerve impulse. Electrophysiology Study of electrical properties of neuron In electrophysiology we basically study about How nerve impulse generated. How Stimulus changed membrane ion concentration. How stimulus converted into nerve impulse Electrophysiology of Neurons

26. An action potential is the Potential difference generate across membrane of neuron due to disbalance of Positive & negative change which ultimately give rise to generation of nerve impulse. Events during generation of Action Potential. Polarization Depolarization Repolarization Hyperpolarization. Action Potential

27. Polarization- known as Resting stage No stimulus comes so that no action potential generate At resting Stage - Inside Membrane- negative(-)& High k + Outside Membrane-Positive (+)& High Na + Resting membrane potential-(-70mv)

28. Depolarization When stimulus comes it deactivates Na + k + Pump. Now Na + ions Continuously ↑ inside cell membrane via leakage channels & ultimately inside of membrane becomes positively charged & this stage is called depolarization (voltage gate Na + also opens) Membrane potential rises to +30 mv.

29. Repolarization Now when wave of depolarization passed from one part of membrane to another, voltage gated Na + channel again gets closed and now voltage gated k + channels opens. Now k + ions continuously passing out from the cell & ultimately the inside of membrane again becomes negatively charged & this stage is called Repolarization. ATPase Pump again activates.

30. Hyperpolarization- Although membrane again becomes repolarized but StiII k + Channels (voltage gated) still remains opened. Now due to this k + ions continues passing outside of membrane & membrane potential becomes -90 mv which causes hyperpolarization. when potential reaches -90mv k + channels also get closes & finally membrane reaches to resting stage

31. Graphical Representation of Events during Action potential

32. A Synapse is a junction between two neurons where transmission of nerve impulses takes place. Synapse allow communication between two neurons & other cells through the use of neurotransmitters. Generally this junction is formed between axon terminal of one neuron and the dendrite of another neuron. Neurotransmitters transmits Signals from presynaptic neuron to postsynaptic neuron. Synapse and Neurotransmitters

33. Classification of Synapse Basically two types of synapse Chemical Synapse Electrical Synapse.

34. Chemical Synapse A chemical synapse is a junction between two neurons through which signals are transmitted by the release of chemical neurotransmitters In the chemical Synapse there is no continuity between two neurons because of presence of space, called Synaptic cleft. Neurotransmitters release from vesicles due to generation of action potential. Almost every synapse in human body is a type of chemical synapse.

35. Electrical Synapse Electrical synapse is a type of synapse in which there is a direct connection between presynaptic & Post synaptic neuron through gap junction. In electrical Synapse transmission occurs very rapidly. They are very Fewer in number compare to chemical synapse

36. Neurotransmitters Neurotransmitters are the chemical messenger that transmit Signals from one neuron to another across a synapse. Neurotransmitters are generally Packed in Synaptic vesicles. They are very important for rapid transfer of nerve impulse between two neurons.

37. Types Of Neurotransmitters On the basis of chemical nature On the basis of function.

38. On the basis of chemical nature Neurotransmitters Amino acids Amines Others Nitric oxide Acetylcholine Adrenaline Dopamine Histamine Nor-adrenaline GABA Glutamate Glycin Aspartate

39. Excitatory Neurotransmitters Inhibitory Neurotransmitters Both On the basis of function

40. Excitatory Neurotransmitters These neurotransmitters act by stimulating the target neurons They increase the influx of sodium ions inside the cell cause depolarization. Examples Ach, Adrenaline, Serotonin etc.. Inhibitory Neurotransmitters These neurotransmitters act by inhibiting the target neurons They increases the outflux of potassium ions outside the cell & cause repolarization e.g. GABA, Glycine, serotonin.

41. Both (Excitatory & Inhibitory ) Neurotransmitters which contains both excitatory & inhibitory properties are classified in this group eg. Ach, Dopamine

42. The CNS is mainly consist of Brain & Spinal cord. Both Brain & Spinal cord is protected by cranial cavity and vertebral column respectively. The CNS is major controlling, regulatory & communicating System in our body Central Nervous System

43. Meninges- Although Brain & spinal cord is protected by cranial bones and vertebral column but since they are very sensitive and important organ of our body, hence they are Called Further Protected by three layers of covering Meninges. Meninges provide both protection & nourishment to brain & spinal cord.

44. Layers of Meninges Durra Matter(outermost layer) Arachnoid Matter( Middle layer) Pia Matter (Innermost layer)

45. Dura Matter (outermost layer)- It is the toughest and outermost layer.-It is Further divided into two Sub layers: Endosteal layer: outer layer towards Skull Meningel layer: Inner layer towards Arachoid matter.

46. Arachnoid Matter- It is the middle Fibrous layer. It is separated from dura matter by subdural space. It is separated from pia matter by subarachnoid space. Arachnoid matter & pia matter are collectively known Leptomeninges.

47. Pia Matter Innermost layer highly vascular connective tissue layer. carries the blood vessels into brain. Play major role in Formation of choroid Plexus . Sub-dural space - space between dura matter & Arachnoid matter. Sub- arachnoid space - space between arachnoid matter & pia matter

48. Gray Matter It is the major component of CNS mainly consist of neuronal cell body & dendrites In brain it is present on the outer side while in spinal cord it is present in the inner side. Gray Matter And White Matter

49. White Matter - It is network of Fibers mainly consist of myelinated axons/ nerve fibres In brain it is Present in the inner side while in spinal cord it is present on the outer side

50. Brain is one of the largest organ in the body which coordinates most of the body activities. It is the control center of the body. The adult human brain weighs on average about 1.4-1.5 kg. In males the average weight is about 1370 g while in females it is about 1200 grams. It is made up of about 100 billion neurons. It is one of the most complex living structure in this universe. The Brain

51. Lateral Ventricles (Right & Left). There are 2 lateral ventricles in our body located in each hemisphere of brain. They are roughly C shaped They are lined by ependymal cells and filled with CSF. Both ventricles are separated with each other by Septum Lucidum . Third Ventricle It is located below lateral ventricles. It is narrow funnel shaped cavity of brain filled with CSF It is connected with 4th ventricle by cerebral aqueduct.

52. Fourth Ventricle It is diamond shaped cavity located below third ventricle. It is connected with 3rd ventricle by cerebral aqueduct.

53. CSF is a clear, colourless & transparent fluid found in the ventricles, sub arachnoid space and central canal of spinal cord. It is mainly formed by choroid plexus of lateral ventricles. Choroid Plexus :Choroid Plexus is a network of blood vessels lined by ependymal cells that produces CSF. The volume of CSF is approx 100-150 ml. It is secret at a rate of 0.5 ml/min or 500-700 ml/day Its pH is slightly alkaline 7.3 Composition of CSF It is composed of : 99%. Water 1%. Salid Substances Cerebrospinal Fluid (CSF)

54. Inorganic- Sodium,potassium,calcium,magnesium,bicarbonates,chloride Organic- Protein,sugar,uric acid,creatinine . Function of CSF- It support,protects & act as shock absorbant for CNS. It provide nutrients to brain & spinal cord.

55. Parts of Brain- It has 4 major parts. 1.Cerebrum 2.Cerebellum 3.Brain stem 4.diencephalon

56. It is the largest portion of brain. It is divided into two cerebral hemisphere i.e , Right Hemisphere & Left Hemisphere. It is located in the upper portion of brain responsible for learning & senses. The superficial layer of cerebrum is known as Cerebral Cortex . Both hemispheres connected by Corpus Callosum . Right Hemisphere: Control left side of body. Left Hemisphere: Control right side of body. CEREBRUM

57. LOBES OF CEREBRUM The cerebrum of brain is divided into 4 major lobes Frontal Lobe Parietal Lobe Temporal Lobe Occipital Lobe Frontal Lobe It is also known as Motor Cortex. It controls, motor functions like personality, movement, planning,decision making,creativity,concentration,thoughts .

58. Parietal lobe- It is also known as sensory cortex. It is responsible for controlling logical reasoning,direction,distance,recognition,storage of language. Temporal lobe- It is known as Auditory cortex. It controls hearing,smell,dreams . Occipital lobe- it is also known as Visual cortex. It receives input from eyes & controls vision.

59. It is the second largest portion of brain. It is located below the posterior part of cerebrum. It is also known as Little brain Structurally it resembles cerebrum, Like cerebrum it is also divided into two cerebellar Hemisphere. The cerebellum controls muscle contraction, movement, balance of body posture etc. It also plays major role in cognition (learning). CEREBELLUM

60. The brain stem is a stem like part of brain that is connected with the spinal cord. It is mainly composed of mid brain, pons and medulla oblongata. Mid Brain : It is one of the smallest portion of brain. It mainly controls the function of sensory organs eye, ears. Pons: Pons means bridge It connects cerebellum with brain. It controls sleep cycle and also manage breathing rate The signals reach the brain from body through the pons It maintains balance between body mind. BRAIN STEM

61. Medulla Oblongata: It is lowermost part of brain. It is directly connected with spinal cord. It mainly controls involuntary actions of body like respiration, Blood Circulation, Heart rate,vomiting .

62. Spinal Cord is a thin tube like structure starts from medulla Oblongata of brain & extends to 1st & 2nd Lumbar vertebra. It is a part of Central Nervous System. In Men the length of spinal cord is about 45 cm while in women it is about 43 cm. It's weight is about 35 gm. It controls and regulates most of reflex action. Spinal Cord

63. COVERING OF SPINAL CORD Spinal Cord is a very sensitive organ of central nervous system, hence it is protected and covered by three layer of tissue called Meninges and bones of Vertebral column. Meninges- Meninges Like brain, spinal cord is also protected and nourished by three layers of membranes called Meninges . Dura Matter Arachnoid Matter Pia matter

64. Vertebral Column It is also known as spinal column or backbone. The bones of vertebral column are called 'Vertebrae’. They provide protection to spinal cord. They are divided into 5 different parts. Cervical Vertebrae -7(C1 to C7) Thoracic Vertebrae-12(T1 to T12) Lumbar Vertebrae-5(L1 to L5) Sacrum-5 (fused) Coccyx-4 (fused)

65. Spinal Cord Segments Spinal cord is divided into 31 segments from which 31 pairs of spinal nerves arises. Cervical Segment / Cervical Nerves: 8 Thoracic Segment / Thoracic Nerves: 12 Lumbar Segment / Lumbar Nerves: 5 Sacral Segment / Sacral Nerves: 5 Coccygeal Segment / Coccygeal Nerve: 1 Spinal Cord Enlargements There are two major enlargements in the spinal cord : Cervical Enlargement Lumbar Enlargement

66. Cervical Enlargement -It is the superior enlargement extends from 4th cervical vertebrae to the 1st thoracic vertebrae [C3-T2]. Lumbar Enlargement -It is the inferior enlargement extends from 9th to 12th thoracic vertebrae [T9-T12]

67. Spinal cord is composed of an inner core of grey matter Surrounded by an outer covering of white matter. Grey matter consist of neuronal cell body white matter consist of axon part. Exactly in the centre of grey matter there is a canal called Central Canal . The posterior part of grey matter is known as Dorsal region in which there are two dorsal horns. The interior part of grey matter is known as Ventral region in which there are two ventral horns. INTERNAL ANATOMY OF SPINAL CORD

68. Reflex activity can be simply defined as an involuntary and immediate response of voluntary muscles to a specific stimulus. The pathway followed by nerve impulses that produces the reflex activity is known as Reflex Arc . If the reflex action is produced by brain then it is known as cranial reflex If the reflex action is produced by spinal cord then it is known as spinal reflex A Reflex Arc contain 5 major components Receptor Receptor Sensory Neurons Control Centre Motor Neurons Effector REFLEX ACTIVITY

69. Thank you!