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Bio
Nervous system
| Term | Definition |
|---|---|
| Central Nervous System | The central nervous system consists of the brain and spinal cord. It's sometimes called the "co-ordinator" because it makes sense of the messages it receives from the sense organs and co-ordinates responses by the muscles and glands. |
| Peripheral nervous system | The peripheral nervous system consists of the bundles of nerves that relay messages between the sense organs, the central nervous system and the muscles and glands. This system is spread out through the entire body, as shown on the right. |
| Stimulus | A stimulus is anything that triggers a response or change in the activity of the living thing (organism). Anything that causes a response is a stimulus. |
| Response | an excitation of a nerve impulse caused by a change or event; a physical reaction to a specific stimulus or situation. Reaction to an event is called a response |
| Receptor | an organ or cell able to respond to light, heat, or other external stimulus and transmit a signal to a sensory nerve. |
| Effector | an organ or cell that acts in response to a stimulus. |
| Types of receptors | chemoreceptors, mechanoreceptors, pain receptors, thermoreceptors and photoreceptors |
| Neurons | Neurons are specialised cells that transmit messages, in the form of electrical signals, to and from, and within, the central nervous system. They act something like the wires of an electric circuit. |
| Sensory neurons | transmit messages from receptors in our sense organs to the central nervous system. |
| Interneurons | transmit messages from sensory neurons to motor neurons. |
| Motor neurons | transmit messages from the central nervous system to "effectors" such as muscles and glands to initiate a response. |
| Chemoreceptors | are sensitive to chemicals, such as odour molecules in the air, and are located in the nose and tongue. |
| Mechanoreceptors | are sensitive to touch, pressure, sound and motion and are located in the skin, the inner ear and muscles. |
| Pain receptors | are sensitive to chemical changes in damaged cells and are located throughout the body, but most are located in the skin. |
| Thermoreceptors | are sensitive to temperature changes and are located in the skin. |
| Photoreceptors | are sensitive to light and are located in the eyes. |
| dendrites | (branches that receive messages), he branching structure of a neuron that receives messages (attached to the cell body) |
| cell body | (where the nucleus is found),the cell body of the neuron; it contains the nucleus (also called the soma) |
| axons | that transmit a message away from the cell body) the long extension of a neuron that carries nerve impulses away from the body of the cell. |
| myelin sheaths | a fatty layer that insulates the axon and sometimes a dendrite the fatty substance that surrounds and protects some nerve fibers and speeds up the action potential. |
| node of Ranvier | one of the many gaps in the myelin sheath - this is where the action potential occurs during saltatory conduction along the axon |
| nucleus | the organelle in the cell body of the neuron that contains the genetic material of the cell |
| Schwann's cells | cells that produce myelin - they are located within the myelin sheath. |
| How do neurons communicate? 1 | A dendrite of a neuron (post-synaptic neuron) receives information from an axon terminal of a prior neuron (pre-synaptic neuron) via a neurotransmitter (a chemical message) across the gap between them (synaptic gap). |
| 2 | This chemical message is then interpreted by that neuron's cell body who decides whether to pass on the message or not. |
| 3 | Neurotransmitters are either excitatory (cause the cell to fire, send on the message) or are inhibitory (prevent transmission of a message). |
| 4 | If the message is passed on it travels as an electrical impulse down the axon towards it's axon terminal causing the release of neurotransmitters from it's storage sacs (vesicles) into the synaptic gap. |
| 5 | The neurotransmitter then makes its way towards the receptor sites of the next neuron's dendrites and so the process continues. Communication occurs in one direction only from dendrite to axon |
| How do neurons communicate | Neurons communicate with each other via electrical events called 'action potentials' and chemical neurotransmitters. |
Created by:
Dnalawattage
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