Nervous System Anatomy

The nervous system is made up of the central nervous system and the peripheral nervous system. The central nervous system (CNS) is made up of the brain and spinal cord. The brain controls most body functions, including awareness, movements, sensations, thoughts, speech and memory.

1. Topic- The Nervous System, Anatomy & Neuronal Communication Online Classes Course Biomedical Instrumentation Presented by Mr. Gaurav Pandey

2. Definition and Basic Structure of Nervous System The nervous system is believed to have ten thousand million of such cells, called neurons and glia , the glia being present in greater numbers than neurons . From a functional standpoint , the nervous system can be divided into two major compartments- The somatic nervous system conveys sensory information (touch, temperature, pain and limb position-even when the eyes are closed) from the body segments and carries the neural pathways that innervate and control the movement of skeletal muscles, such as those of the arms, fingers, legs and toes .

3. ( b) The visceral nervous system controls internal organs that are not normally under the influence of blood vessels, the dilation and constriction of the pupils of the eyes and so on . From an anatomical viewpoint , four main components need to be identified : T he C entral nervous system The Peripheral nervous system including cranial nerves, the autonomic system and the neuroendocrine system.

4. The Neuron

5. The dendrites are finely branched processes arising near the cell body of a neuron. The dendrites receive excitatory or inhibitory effects via chemical messengers called neurotransmitters . The cytoplasm is the material of the cell body in which the organelles-including the cell nucleus-and other inclusions are found . The nucleus contains the cell's chromatin, or genetic material . The nucleus is rich in ribonucleic acid (RNA), which is necessary for the synthesis of protein. 

6. Functions of Neuron The normal functions of the neuron include- protein synthesis axonal transport generation and conduction of the action potential synaptic transmission formation and maintenance of the myelin . Myelin  is an insulating layer that forms around nerves, including those in the brain and spinal cord. It is made up of protein and fatty substances. This  myelin  sheath allows electrical impulses to transmit quickly and efficiently along the nerve cells

7. Neurotransmitter A neurotransmitter is a chemical substance which, when released from axon terminals by the action potential, produces the momentary change in electrical potential when another nerve fibre is stimulated. Neurotransmitters stimulate or inhibit adjacent neurons or effector organs such as muscle and glands. Some neurological and psychiatric disorders-myasthenia gravis, Parkinson's disease, depression , severe distortion of thought processes such as in schizophrenia, and Alzheimer's disease . Acetylcholine, Norepinepharine , Serotonin, Gama Amino Butyric acid are the common neurotransmitters.

8. Reflex Arc

9. Components of a Reflex Arc Receptor - reacts to a stimulus B . Afferent pathway (sensory neuron) - conducts impulses to the CNS C . Interneuron - consists of one or more synapses in the CNS (most are in the spine) D . Efferent pathway (motor neuron) conducts impulses from CNS to effector . E . Effector - muscle fibers (as in the Hamstring muscle) or glands responds by contracting or secreting a product. Spinal reflexes - initiated and completed at the spinal cord level. Occur without the involvement of higher brain centers .

10. Neuronal Communication Within a single neuron, information is relayed through electric signals. Ions of either positive or negative charge cross the cell membrane, creating a  potential  across the cell membrane. When a neuron is resting, the charge created across the membrane is called the   resting potential , and is usually about -70 mV. This means that the inside of the neuron is negative compared to the outside. Signals from other neurons will cause a shift in ions, or a movement of charge. Thus, the neuron will veer away from its resting potential to become  depolarized —  less negative— or  hyperpolarized —  more negative. When a neuron depolarizes sufficiently, it sends signals onto the next neuron. This is the nervous system’s check – a neuron will not propagate information until it is sufficiently depolarized.

11. 5. Communication between neurons is achieved primarily through neurotransmitters, or small molecules that are released into the  synapse.