Introduction of nervous system physiology

Neuroscience, nervous system

1. Physiology of Nervous System P H S - 70 5

2. LECTURE-1

3. Nervous System The master controlling and communicating system of the body and is a complex network of nerves and cells that carry messages to and from the brain and spinal cord to various parts of the body Or The nervous system is the part of body that coordinates its voluntary and involuntary actions and transmits signals between different parts of its body

4. Nervous System

5. Functions of Nervous System Sensory input – Monitoring stimuli occurring inside and outside the body Integration – Interpretation of sensory input Motor output – Response to stimuli by activating effector organs Learning – Acquiring new, or modifying and reinforcing, existing knowledge, behaviors, skills, values, or preferences and may involve synthesizing different types of information Memory – The process in which information is encoded, stored, and retrieved Language – The ability to acquire and use complex systems of communication

6. Organization of the Nervous System Central nervous system (CNS) Peripheral nervous system (PNS)

7. Central nervous system (CNS) Brain and Spinal cord Integration and command center Organization of the Nervous System

8. Peripheral nervous system (PNS) Paired spinal and cranial nerves Carries messages to and from the spinal cord and brain Organization of the Nervous System

9. Peripheral Nervous System (PNS): Two Functional Divisions Sensory (afferent) division Somatic afferent fibers – carry impulses from skin, skeletal muscles, and joints to the brain Visceral afferent fibers – transmit impulses from visceral organs to the brain Motor (efferent) division Transmits impulses from the CNS to effector organs

10. Somatic nervous system (Voluntary) Conscious control of skeletal muscles Autonomic nervous system (ANS) (Involuntary) Regulates smooth muscle, cardiac muscle, and glands Divisions – Sympathetic, Parasympathetic and Enteric Nervous System (Second Brain of body) Motor Division: Two Main Parts

11. Autonomic Nervous System ( ANS )

12. Fight-or-flight response

13. "Rest-and-digest" or "Feed and breed"

14. a c o m p l e x , i n d e p e n d e n t n e r v o u s s y s t e m lines the gastrointestinal tract “ s e c o n d b r a i n ” “ t h e b r a i n o f t h e g u t ” motility controls essential functions ► secretion blood flow Enteric Nervous System ( ENS ) or Intrinsic Nervous System

15. Enteric Nervous System ( ENS ) or Intrinsic Nervous System

16. LECTURE-2

17. Composition of Nervous System The Nervous System is composed mainly of Nervous Tissue Connective tissues Blood vessels are also present. Nervous tissue is composed of 2 types of cells: Neurons Supporting Cells Neurons = nerve cells are excitable and conducting cells Supporting cells (Glia, Glial cells, Neuroglia) are non-conducting cells

18. Neuron (Nerve Cell)

19. Structural unit of the nervous system Composed of a cell body, axon, and dendrites Long-lived, amitotic, and has a high metabolic rate The plasma membrane functions in: Electrical signaling Cell-to-cell signaling during development Neuron (Nerve Cell)

20. Contains the nucleus and a nucleolus Is the major biosynthetic center Is the focal point for the outgrowth of neuronal processes Has no centrioles (hence its amitotic nature) Has well-developed Nissl bodies (rough ER) Contains an axon hillock – cone-shaped area from which axons arise Nerve Cell Body (Perikaryon or Soma)

21. Arm like extensions from the soma There are two types: Axons Dendrites Collection of Axons Tracts in the CNS Nerves in the PNS P r o c e ss e s

22. Short, tapering, and diffusely branched processes They are the receptive, or input, regions of the neuron Electrical signals are conveyed as graded potentials (not action potentials) Dendrites

23. Slender processes of uniform diameter arising from the hillock Long axons are called nerve fibers Usually there is only one unbranched axon per neuron Rare branches, if present, are called axon collaterals Axonal terminal – branched terminus of an axon Axons: Structure

24. Generate and transmit action potentials Secrete neurotransmitters from the axonal terminals Movement along axons occurs in two ways Anterograde: toward axonal terminal Retrograde: away from axonal terminal Axons: Function

25. Classification of Neurons Classification based on the function Classification based on the structure Classification based on the neurotransmitters

26. Classification of Neurons Classification based on the function: Motor or Efferent neuron: Transmits impulses AWAY from the CNS to effector organs = glands, organs Sensory or Afferent neuron: Transmits impulses from sensory receptors TOWARD the CNS Association neurons or interneuron: Located in the CNS between the sensory neurons and the motor neurons Most of the neurons (99%) in the body are associated neurons

27. Classification based on the function:

28. Classification of Neurons Classification based on the structure: Polarity (Number of processes) Multipolar: There are at least 3 processes – one axon and at least 2 dendrites; most abundant neurons in the human body Bipolar: There are only 2 processes – one axon and one dendrite Unipolar/Pseudo-unipolar: Such neurons have one short process from the cell body that bifurcates into a central process and a peripheral process

29. Classification based on the structure:

30. Classification based on the structure:

31. Classification of Neurons identified a c c o r d i n g t o t h e ir l o c a t i o n in t h e n e r v o u s s y s t e m a n d d i s t i n c t shape. Some examples are: Basket cells: Interneurons that form a dense plexus of terminals around the soma of target cells, found in the cortex and cerebellum. Betz cells: Large motor neurons. Lugaro cells: Interneurons of the cerebellum. Classification based on the structure: Other unique types F u r t h e r m o r e , s o me un i q u e n e u r o n al t y p e s c an b e

32. Classification of Neurons Classification based on the structure: Other unique types Medium spiny neurons: Most neurons in the corpus striatum. Purkinje cells: Huge neurons in the cerebellum, a type of Golgi I multipolar neuron. Pyramidal cells: Neurons with triangular soma, a type of Golgi I. Renshaw cells: Neurons with both ends linked to alpha motor neurons.

33. Classification of Neurons Classification based on the structure: Other unique types Unipolar brush cells: Interneurons with unique dendrite ending in a brush-like tuft. Granule cells: A type of Golgi II neuron. Anterior horn cells: Motorneurons located in the spinal cord. Spindle cells: Interneurons that connect widely separated areas of the brain

34. Classification of Neurons Classification based on the structure:

35. Comparison of Structural Classes of Neurons

36. Comparison of Structural Classes of Neurons

37. Comparison of Structural Classes of Neurons

38. Classification of Neurons Classification based on the Neurotransmitters:

39. Classification of Neurons Classification based on the Neurotransmitters:

40. LECTURE-3

41. Neuroglia/Supporting cells Supporting cells/Neuroglia (Nerve Glue)/Glia

42. Supporting cells = Neuroglia (Nerve Glue) 4 Supporting cells are located in the CNS Astrocytes Microglia Ependymal Oligodendrocytes 2 Supporting cells are located in the PNS Schwann cells Satellite cells Neuroglia/Supporting cells

43. Astrocytes Most abundant Numerous extensions that wrap around neurons Involved in forming the BLOOD-BRAIN BARRIER, a selective barrier that regulate the chemicals environment of the brain Regulate brain function Supporting Cells in the CNS

44. 2. Microglia Since the specific immune system does not have access to the CNS; the microglia act as macrophages to engulf/destroy pathogens and cell debris. Supporting Cells in the CNS

45. Ependymal cells Ciliated columnar cells that line the ventricles – cavities in the brain that contain cerebrospinal fluid (CSF) Currents created by beating of cilia circulate the CSF Supporting Cells in the CNS

46. 4. Oligodendrocytes Their extensions myelinate axons of neurons in the CNS Supporting Cells in the CNS

47. 4. Oligodendrocytes Their extensions myelinate axons of neurons in the CNS Supporting Cells in the CNS

48. 1. Schwann cells = Neurolemmocytes Myelinate axons of neurons in the PNS Supporting Cells in the PNS

49. 2. Satellite cells Surround cell bodies of neurons and control their chemical environment Supporting Cells in the PNS

50. Whitish, fatty (protein-lipoid), segmented sheath around most long axons It functions to: Protect the axon Electrically insulate fibers from one another Increase the speed of nerve impulse transmission Myelin Sheath

51. Formed by Schwann cells in the PNS A Schwann cell: Envelopes an axon in a trough Encloses the axon with its plasma membrane Has concentric layers of membrane that make up the myelin sheath Neurilemma – remaining nucleus and cytoplasm of a Schwann cell Myelin Sheath and Neurilemma

52. Myelin Sheath and Neurilemma

53. Gaps in the myelin sheath between adjacent Schwann cells They are the sites where axon collaterals can emerge Nodes of Ranvier (Neurofibril Nodes)