2. NERVOUS SYSTEM NERVOUS SYSTEM The nervous system is composed of specialized cells called neuron, which exercise control by sending electrical signals called nerve impulses. Nerve cells are the structural and functional unit of nervous system. The nervous system is composed of specialized cells called neuron, which exercise control by sending electrical signals called nerve impulses. Nerve cells are the structural and functional unit of nervous system.

3. STRUCTURE OF NEURON A neuron consists of three prominent parts- 1.Cell body- The cell body of neuron is also called cyton or soma. It receives nerve impulses from dendrites and transmit them to axon. 2.Dendrites- dendrites are the parts of neuron where sensation acquired. The information then travels as an electric impulse towards the cell body.

4. Axon:-It is a single, cylindrical protoplasmic nerve fibre. At its terminal axon is highly branched. The axon conducts nerve impulses away from the cell body.

6. The neurons lie end to end in chains to transmit nerve impulses in the animal body. The neurons are not connected. There occurs a very minute gap between terminal portion of axon of one neuron and the dendron of other neuron. This minute gap is called synapse. The neurons lie end to end in chains to transmit nerve impulses in the animal body. The neurons are not connected. There occurs a very minute gap between terminal portion of axon of one neuron and the dendron of other neuron. This minute gap is called synapse. Axon terminal expand to form presynaptic knob and dendrite forms post synaptic depression. In between the two lies a fluid filled space called synaptic cleft. Axon terminal expand to form presynaptic knob and dendrite forms post synaptic depression. In between the two lies a fluid filled space called synaptic cleft. ARRANGEMENT OF NEURON

7. As the nerve impulses reaches the pre-synaptic knob, the synaptic vesicles get stimulated to release a chemical called neurotransmitter in the synaptic cleft. The neurotransmitter molecules diffuse across the gap to come in contact with the chemoreceptor site in the nerve impulses passes from one neuron to other. As the nerve impulses reaches the pre-synaptic knob, the synaptic vesicles get stimulated to release a chemical called neurotransmitter in the synaptic cleft. The neurotransmitter molecules diffuse across the gap to come in contact with the chemoreceptor site in the nerve impulses passes from one neuron to other.

8. REFLEX ACTIONS A Reflex actions may be defined as a spontaneous, automatic and mechanical response to a stimulus, acting on a specific receptor, without the will of an animal. In certain situation, sensation requires immediate response as time used for processing may cause harm to the body. In such situation reflex action occur. A Reflex actions may be defined as a spontaneous, automatic and mechanical response to a stimulus, acting on a specific receptor, without the will of an animal. In certain situation, sensation requires immediate response as time used for processing may cause harm to the body. In such situation reflex action occur. Example:-blinking of eyes,withdraw of hand suddenly pinched or touched by a hot object.

9. HUMAN NERVOUS SYSTEM Human nervous system is the most complex. It is divided into two main parts- Human nervous system is the most complex. It is divided into two main parts- i) Central nervous system ii) Peripheral nervous system

11. It is hollow and lies on the mid-dorsal part along the main axis of the body. It is covered by a part of axial skeleton. The CNS in turn consists of two parts- It is hollow and lies on the mid-dorsal part along the main axis of the body. It is covered by a part of axial skeleton. The CNS in turn consists of two parts- 1. Brain or Encephalon situated in the head. 2. Spinal cord or Myelon located in the neck and trunk. CENTRAL NERVOUS SYSTEM

12. BRAIN The brain is the widest and the uppermost part of the central nervous system. It is the highest coordinating centre in the body. Brain is situated in the cranial cavity of the skull. The brain is soft, whitish organ. It weighs 1.2 to 1.4 kg and forms about 98% of the weight of the whole nervous system. It has about 100 bilion neurons. Brain is surrounded by three membranes called meninges which provide protection to it. The space between the meninges is filled with the cerebro- spinal fluid. The brain is the widest and the uppermost part of the central nervous system. It is the highest coordinating centre in the body. Brain is situated in the cranial cavity of the skull. The brain is soft, whitish organ. It weighs 1.2 to 1.4 kg and forms about 98% of the weight of the whole nervous system. It has about 100 bilion neurons. Brain is surrounded by three membranes called meninges which provide protection to it. The space between the meninges is filled with the cerebro- spinal fluid.

13. Brain is divisible into three main region – 1. FOREBRAIN- It forms the greater part of the brain. It consists of three parts: olfactory lobes, cerebral hemisphere and diencephalon. i) Olfactory lobes- A pair of widely separated club- shaped small structure. Each olfactory lobe consist of an anterior olfactory bulb and a posterior narrow olfactory stalk. These lobes receive impulses from olfactoreceptors and relay sense of smell to the temporal region of the cerebrum. i) Olfactory lobes- A pair of widely separated club- shaped small structure. Each olfactory lobe consist of an anterior olfactory bulb and a posterior narrow olfactory stalk. These lobes receive impulses from olfactoreceptors and relay sense of smell to the temporal region of the cerebrum.

14. (ii) Cerebral hemisphere- It is the largest part of the brain. The two cerebral hemisphere lie side by side separated by deep cerebral fissure. The cerebral hemisphere divided into four lobes – (ii) Cerebral hemisphere- It is the largest part of the brain. The two cerebral hemisphere lie side by side separated by deep cerebral fissure. The cerebral hemisphere divided into four lobes – a. Frontal lobe is the region for speech,facial, muscular activities and mental activities. a. Frontal lobe is the region for speech,facial, muscular activities and mental activities. b. Temporal lobe is the region for auditory reception (hearing ). b. Temporal lobe is the region for auditory reception (hearing ). c. Occipital lobe is the region for visual reception (sight ) c. Occipital lobe is the region for visual reception (sight ) d. Parietal lobe is the region for touch,taste,smell, temperature and conscious association. d. Parietal lobe is the region for touch,taste,smell, temperature and conscious association.

16. (iii) Diencephalon:-It lies on the side of cerebrum It roof is called epithalamus, sides are called thalami and its floor is called hypothalamus. Diencephalon has a narrow cavity called third ventricle. 2. MID BRAIN:-It is significantly small region. It consists of two fibre tracts called crura cerebri and a pair of two swellings called superior and infeior colliculi on each side. the two superior colliculi have centres for sight reflexes and the two inferior colliculi have centre for sight reflexes. It controls the movement of head, neck, eye muscles ;changes in pupil size as well as shape of eye lens.

17. 3. HIND BRAIN:- The hind brain consists of three parts- cerebellum, pons varolii and medulla oblongata. The cerbellum is the second largest part of the brain, constituting nearly 12% of it. It has two large, lateral cerebellar hemispheres and a central vermis. Cerebellum maintains the posture, equilibrium and muscles tone. Pons varolii controls some aspects of respiration. Medulla oblongata is the posterior part of the brain. It controls rate of heartbeat, breathing movements etc.

18. SPINAL CORD Spinal cord is a cylindrical structure and is about 45cm long. It begins in continuation with the medulla oblongata of brain extend downward up to early part of the lumber region. It then extend to the end of vertebral column as fibrous connective called filum terminale. Internally the spinal cord possess a narrow, fluid filled cavity called central canal. Spinal cord is enclosed in the vertebral column or backbone which protect it. It conducts sensory and motor impulses to and from the brain. It act as center for the reflex action Spinal cord is a cylindrical structure and is about 45cm long. It begins in continuation with the medulla oblongata of brain extend downward up to early part of the lumber region. It then extend to the end of vertebral column as fibrous connective called filum terminale. Internally the spinal cord possess a narrow, fluid filled cavity called central canal. Spinal cord is enclosed in the vertebral column or backbone which protect it. It conducts sensory and motor impulses to and from the brain. It act as center for the reflex action

19. PERIPHERAL NERVOUS SYSTEM It connects CNS with different part of the body. It has two component, voluntary and Autonomic nervous system. These are- It connects CNS with different part of the body. It has two component, voluntary and Autonomic nervous system. These are- 1. Voluntary peripheral nervous system is under the control of will. It consist of nerves that arise directly from CNS connecting different body parts for voluntary control of the brain. 1. Voluntary peripheral nervous system is under the control of will. It consist of nerves that arise directly from CNS connecting different body parts for voluntary control of the brain.

20. 2. Autonomic nervous system (involuntary nervous system), on other hand, is not under the control of human will. It developed branches of some cranial and some spinal nerves called visceral nerves. It is subdivided into two parts: 2. Autonomic nervous system (involuntary nervous system), on other hand, is not under the control of human will. It developed branches of some cranial and some spinal nerves called visceral nerves. It is subdivided into two parts: (i) sympathetic nervous system (i) sympathetic nervous system (ii) parasympathetic nervous system (ii) parasympathetic nervous system

21. The Organization of the Sympathetic Division of the ANS

22. Sympathetic chain ganglia (paravertebral ganglia) – preganglionic fibers of the sympathetic NS that carry motor impulses to the body wall or thoracic cavity synapses in chain ganglia Sympathetic chain ganglia (paravertebral ganglia) – preganglionic fibers of the sympathetic NS that carry motor impulses to the body wall or thoracic cavity synapses in chain ganglia Collateral ganglia (prevertebral ganglia) – group of second order neurons that innervate organs in the abdominopelvic region Collateral ganglia (prevertebral ganglia) – group of second order neurons that innervate organs in the abdominopelvic region Sympathetic ganglia

23. Sympathetic Pathways

26. Animation: The sympathetic division (see tutorial) The Distribution of Sympathetic Innervation

28. Rejoin spinal nerves and reach their destination by way of the dorsal and ventral rami Rejoin spinal nerves and reach their destination by way of the dorsal and ventral rami Those targeting structures in the thoracic cavity form sympathetic nerves Those targeting structures in the thoracic cavity form sympathetic nerves Go directly to their destination Go directly to their destination Postganglionic fibers

29. Sympathetic innervation via preganglionic fibers that synapse within collateral ganglia Sympathetic innervation via preganglionic fibers that synapse within collateral ganglia Splanchic nerves – carry fibers that synapse in collatheral ganglia Splanchic nerves – carry fibers that synapse in collatheral ganglia Abdominopelvic viscera

30. Celiac ganglion Celiac ganglion Innervates stomach, liver, gall bladder, pancreas, spleen Innervates stomach, liver, gall bladder, pancreas, spleen Superior mesenteric ganglion Superior mesenteric ganglion Innervates small intestine and initial portion of large intestine Innervates small intestine and initial portion of large intestine Inferior mesenteric ganglion Inferior mesenteric ganglion Innervates kidney, urinary bladder, sex organs, and final portion of large intestine Innervates kidney, urinary bladder, sex organs, and final portion of large intestine Abdominopelvic viscera

31. Sympathetic activation is controlled by sypathetic centers in the hypothalamus. Sympathetic activation is controlled by sypathetic centers in the hypothalamus. In crises, the entire sympathetic division responds In crises, the entire sympathetic division responds Sympathetic activation Sympathetic activation Affects include increased alertness, energy and euphoria, increased cardiovascular and respiratory activities, elevation in muscle tone, mobilization of energy resources Affects include increased alertness, energy and euphoria, increased cardiovascular and respiratory activities, elevation in muscle tone, mobilization of energy resources Sympathetic activation

32. Stimulation of sympathetic division has two distinct results Stimulation of sympathetic division has two distinct results Release of ACh or NE at specific locations Release of ACh or NE at specific locations Secretion of E and NE into general circulation Secretion of E and NE into general circulation Most postganglionic fibers are adrenergic, a few are cholinergic or nitroxidergic Most postganglionic fibers are adrenergic, a few are cholinergic or nitroxidergic Neurotransmitters and sympathetic function

33. Sympathetic Variosities

34. Preganglionic neurons in the brainstem and sacral segments of spinal cord Preganglionic neurons in the brainstem and sacral segments of spinal cord Ganglionic neurons in peripheral ganglia located within or near target organs Ganglionic neurons in peripheral ganglia located within or near target organs Parasympathetic division

35. The Organization of the Parasympathetic Division of the ANS

36. Preganglionic fibers of parasympathetic neurons can be found in cranial nerves III, VI, IX, X Preganglionic fibers of parasympathetic neurons can be found in cranial nerves III, VI, IX, X Sacral neurons form the pelvic nerves Sacral neurons form the pelvic nerves Almost 75% of all parasympathetic outflow travels along the vagus nerve (cranial nerve X) Almost 75% of all parasympathetic outflow travels along the vagus nerve (cranial nerve X) Organization and anatomy of the parasympathetic division

37. The Distribution of Parasympathetic Innervation

38. Effects produced by the parasympathetic division Effects produced by the parasympathetic division relaxation relaxation food processing food processing energy absorption energy absorption Parasympathetic activation

39. All parasympathetic fibers release ACh All parasympathetic fibers release ACh Short-lived response as ACH is broken down by AChE and tissue cholinesterase Short-lived response as ACH is broken down by AChE and tissue cholinesterase Neurotransmitters and parasympathetic functions

40. Sympathetic Sympathetic Widespread influence on visceral and somatic structures Widespread influence on visceral and somatic structures Parasympathetic Parasympathetic Innervates only visceral structures serviced by cranial nerves or lying within the abdominopelvic cavity Innervates only visceral structures serviced by cranial nerves or lying within the abdominopelvic cavity Effects produced by the parasympathetic branch include increased secretion by digestive glands Effects produced by the parasympathetic branch include increased secretion by digestive glands Dual innervation = organs that receive input from both systems Dual innervation = organs that receive input from both systems Sympathetic and parasympathetic divisions

41. Sympathetic and parasympathetic systems intermingle to form autonomic plexuses Sympathetic and parasympathetic systems intermingle to form autonomic plexuses Cardiac plexus – sympathetic and parasympathetic fibers bound for the heart and kungs pass through the cardiac plexus Cardiac plexus – sympathetic and parasympathetic fibers bound for the heart and kungs pass through the cardiac plexus Pulmonary plexus Pulmonary plexus Esophageal plexus Esophageal plexus Celiac plexus Celiac plexus Inferior mesenteric plexus Inferior mesenteric plexus Hypogastric plexus Hypogastric plexus Anatomy of dual innervation

42. The Autonomic Plexuses

43. Important physiological and functional differences exist Important physiological and functional differences exist Comparison of the two divisions

44. Summary: The Anatomical Differences between the Sympathetic and Parasympathetic Divisions

46. A Comparison of Somatic and Autonomic Function

47. Activity in the ANS is controlled by centers in the brainstem that deal with visceral functioning Activity in the ANS is controlled by centers in the brainstem that deal with visceral functioning Higher levels of autonomic control

48. Levels of Autonomic Control Example of higher-level of autonomic function would be increased heart rate when you see a person that you dislike.

50. Are performed by the cerebral cortex and involve complex interactions Are performed by the cerebral cortex and involve complex interactions Involve conscious and unconscious information processing Involve conscious and unconscious information processing Are subject to modification and adjustment over time Are subject to modification and adjustment over time Higher order functions

51. Short term or long term Short term or long term Memory consolidation is moving from short term to long term Memory consolidation is moving from short term to long term Hippocampus is essential for memory consolidation Hippocampus is essential for memory consolidation Mechanisms involved in memory formation and storage are: Mechanisms involved in memory formation and storage are: Increased release of neurotransmitter Increased release of neurotransmitter Formation of additional synaptic connection Formation of additional synaptic connection Formation of memory engrams (single circuit that correspond to single memory) Formation of memory engrams (single circuit that correspond to single memory) Amnesia is the loss of memory due to disease or trauma Amnesia is the loss of memory due to disease or trauma Memory

52. Memory that can be voluntarily retrieved and verbally expressed are called declarative memories Memory that can be voluntarily retrieved and verbally expressed are called declarative memories Conversion of a short term memory to a long term memory is called memory consolidation Conversion of a short term memory to a long term memory is called memory consolidation Memory

53. Memory Storage

54. Deep sleep, the body relaxes and cerebral cortex activity is low Deep sleep, the body relaxes and cerebral cortex activity is low The reticular activating system (RAS) is important to arousal and maintenance of consciousness The reticular activating system (RAS) is important to arousal and maintenance of consciousness RAS is located in the mesencephalon RAS is located in the mesencephalon Consciousness

55. The Reticular Activating System

56. Reduction in brain size and weight Reduction in brain size and weight Reduction in the number of neurons Reduction in the number of neurons Decrease in blood flow to the brain Decrease in blood flow to the brain Changes in synaptic organization of the brain Changes in synaptic organization of the brain Intracellular and extracellular changes in CNS neurons Intracellular and extracellular changes in CNS neurons Age-related changes

57. You should now be familiar with: The organization of the autonomic nervous system. The organization of the autonomic nervous system. The structures and functions of the sympathetic and parasympathetic divisions of the ANS. The structures and functions of the sympathetic and parasympathetic divisions of the ANS. The mechanisms of neurotransmitter release in the sympathetic and parasympathetic divisions. The mechanisms of neurotransmitter release in the sympathetic and parasympathetic divisions. The effects of sympathetic and parasympathetic neurotransmitters on target organs and tissues. The effects of sympathetic and parasympathetic neurotransmitters on target organs and tissues. The hierarchy of interacting levels of control in the ANS. The hierarchy of interacting levels of control in the ANS. How memories are created, stored and recalled. How memories are created, stored and recalled. The effects of aging on the nervous system. The effects of aging on the nervous system.