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Structure of neuron and functions of neuron
- 1. Ms. Saira Javed M.PhilPsychology Quaid-i-Azam University Islamabad
- 2. 1) The Neuronand Neurotransmitters - relaying messages; small scale 2) The Brain - interpreting and processing messages 3) The Nervous System - relaying messages; large scale
- 3. The neuronis the basic building block of the nervous system, which is the body’s primary communication network. The nervous system gathers and processes information from the environment and allows you to act on the environment. The neuron’s basic task is to communicate with in and with other neurons.
- 4. Neurons varygreatly in size and shape, depending on their specialized function: -Human brain 100 billion neurons -brain tissue rice grain -10,000 neurons Neurons are simple “cheap” structures, but highly specialized.
- 6. The neuronis comprised of three basic components: 1. Dendrites 2. Cell body or soma 3. Nucleus 4. Axon 5. Myelin Sheath 6. Terminal branches 7. Terminal buttons
- 7. Dentrites receiveinformation from other neurons In Greek, dendrites mean branches, hence, they are like extensive tree branches. The more branches, the more information a neuron can receive.
- 8. The soma,or more commonly referred to as the cell body, sums and subtracts the information it receives from the dendrites. It also contains the nucleus, which provides energy for neurons to carry out their function.
- 9. Contains GeneticMaterial (chromosomes) including information for cell development and synthesis of proteins, necessary for cell maintenance and survival.
- 10. The Axonsends messages to other neurons and parts of body (ie. glands, muscles). Unlike the dendrites, there is only one axon, which varies in length (few thousandths of inch to base of spine to big toe).
- 11. To helptransmit the message or action potential down the axon, “myelin sheath” insulates the axon. Myelinated axons speed neuronal transmission by about 15 times. Most neurons are myelinated, however, not all. Myelinated axons are responsible for making our bodily movements smooth. If myelinated axons start to degenerate, then degenerative diseases, such as multiple sclerosis or Parkinson’s disease occurs, where movement is much more jagged
- 12. Form Junctionswith other cells 7. 7. Terminal Buttons Terminal Buttons Are located at the end of terminal branches. Responsible for sending the signals to other neurons. At the end of the terminal button is a gap called synapses synapses
- 13. • Ifone neuron is signaling another neuron, the first is called the presynaptic neuron, and the second is called the postsynaptic neuron. A presynaptic neuron can signal the dendrite, cell body, or axon of a second neuron. Synapses can be: Chemical or Electrical
- 14. Chemical synapsesare more common. Chemical synapses involve the release of a chemical called a neurotransmitter from the axon’s terminal boutons. The synaptic cleft is very small, and the presynaptic and postsynaptic cells are held close together by cell adhesion proteins.
- 15. Electrical synapsesoccur in: – smooth muscle and cardiac muscle, – between some neurons of the brain, and – between glial cells (nerve glue-keeps the whole CNS together, act as house keeper and remove dead cells) Cells are joined by gap junctions.
- 17. In orderfor a neuron to fire it’s message, it must reach “stimulus threshold.” Stimulus threshold is the minimum amount of information needed for the neuron to fire. For example, your friend is talking in a low voice, so low that you don’t even hear it. Stimulus threshold is the lowest your friend can talk to you so that you actually pick up the sound, which is why the definition states that it is the minimum amount of information.
- 18. The firingof the message down the axon is called “action potential.” It occurs in an “all-or-none” process, which means either the message is sent or not sent.
- 20. Let’s goback to the example of your friend whispering. The louder your friend talks to you, the faster the action potential (or message) will be sent to the appropriate brain region so that it can process this auditory information.
- 21. Functional classification:– Sensory neurons: conduct impulses from sensory receptors to the CNS – Motor neurons: conduct impulses from the CNS to target organs (muscles or glands) Association/interneurons: located completely within the CNS and integrate functions of the nervous system
- 22.