Structure of neuron and propagation mechanism of nerve impulse

Neuron and nerve impulse action explained briefly.

1. STRUCTURE OF NEURON AND PROPAGATION MECHANISM OF NERVE IMPULSE. PRESENTED BY: K.Kavya Priya Reg. No: 121822201003 M.Sc. Biochemistry Semester II Dept. Of Biochemistry and Bioinformatics. GITAM Institute of Science GITAM University.

2. Let’s start with the Nervous system.... NERVOUS SYSTEM : The nervous system 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. It consists of two main parts: The central nervous system (CNS) 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. Nerves that transmit signals from the brain are called  motor or efferent nerves , while those nerves that transmit information from the body to the CNS are called  sensory or afferent.

3. CELLS OF NERVOUS SYSTEM: The nervous system contains two main categories of cells:  Neurons: Functional unit of Nervous system. Communicate with other cells via  synapses , that allows rapid transmission of signals, either electrical or chemical. Glial cells: The most important functions of glial cells are: To support neurons and hold them in place. To supply nutrients to neurons. To insulate neurons electrically To destroy pathogens and remove dead neurons. To direct the axons of neurons to their targets. GLIAL CELL NEURON

4. NEURON: There are about 86 billion neurons in the human brain, which comprises roughly 10% of all brain cells. The neurons are supported by glial cells and astrocytes. Neurons are connected to one another and to other tissues through tiny gaps called synapses. These gaps can be chemical synapses or electrical synapses and pass the signal from one neuron to the next. SYNAPSE

5. STRUCTURE OF NEURON: Every neuron is made of : Cell body. Dendrites. Axon. Myelin sheath. Nodes of Ranvier. Axon terminal. Basic structure of neuron.

6. Cell body: The cell body, also called the  soma , is the part of the neuron that contains the nucleus and various cell organelles.  It usually lies between axon and dendrites. The  axon hillock  is a specialized part of the cell body (or soma) that connects to the axon.   Dendrite: Dendrite is a highly branched, generally tapering extension of a neuron (nerve cell) that usually receives signals from other neurons . Axon: Axon is the extension of cell body. It is also called as the nerve fiber that transmit nerve impulses away from cell body towards the axon terminal. Axons are usually long. Microscopic image of a neuron.

7. Myelin sheath: The Myelin Sheath of a neuron consists of fat-containing cells  that insulate the axon for electrical activity, it increase the speed at which information travels from one nerve cell body to another. Myelin sheath consists of 80% lipid and 20% protein. The myelin is produced by Oligodendrocytes in CNS and by Schwann cells in PNS. The process of generating myelin is called  myelination or myelinogenesis. Myelin sheath.

8. Nodes of Ranvier: They are first discovered in 1878 by French histologist and pathologist  Louis-Antoine Ranvier. They are uninsulated and highly enriched in ion channels, allowing them to participate in the exchange of ions required to regenerate the action potential. Axon terminal: An Axon Terminal is the very end of a branch of a nerve's axon,conducts electrical signals to a nerve synapse. Node of Ranvier. Axon Terminal.

9. TYPES OF NEURONS : Structural classification:

10. Functional classification: 1.Sensory neurons. 2.Interneurons. 3.Motor neurons.

11. MECHANISM OF NERVE IMPULSE PROPAGATION:

12. The major events that occur during nerve impulse propagation are: 1.Initiation of action potential. 2.Depolarization. 3.Repolarization. Initiation of action potential.

13. Depolarization and repolarization.

14. Action potential movement through the axon:

15. PLOT SHOWING DIFFERENT PHASES OF ACTION POTENTIAL TRANSMISSION.

16. SYNAPSE: Synapse is a structure that permits a neuron (or nerve cell) to pass an electrical or chemical signal to another neuron or to the target effector cell. It consist of : Pre-synaptic neuron(which transmits the nerve impulse) Post synaptic neuron(which receives the transmitted nerve impulse). Structure of a synapse

17. TYPES OF SYNAPSE: 1.Based on function: Electrical synapse. Chemical synapse .

18. Anatomical types of synapse: Axodendritic. Axosomatic. Axoaxonic. Dendrodendritic. Dendrosomatic.

19. ELECTRICAL SYNAPSE:

20. CHEMICAL SYNAPSE: Mediated by NEUROTRANSMITTERS.

21. Acetylcholine mediated chemical synapse: