NERVE CELLS

NERVE CELLSMiss Melinda T. RafaelAdviserGrade VI Julian FelipeThe body system that controls other parts of the body is the nervous system.the nervous system receives signals or stimuli from inside and outside your body. A stimulus is an agent or factor that provokes interest, enthusiasm or excitement. Once your nervous system receives a stimulus, it reacts. A response is an action of an organism ar any part of its body to stimulus.The nervous system receives stimuli and after processing them, gives direction to various parts of the body to coordinate the responses.The NEURONS, considered as the working unit of the nervous system, carries out all these functions.The NEURON or nerve cell is the functional unit of the nervous system.A neuron is a cell in the body that is specialized to carry messages.

The process by which a neuron carries messages from one part of the brain to another is through what is called an electrochemical process.

The electro part happens in the neuron itself. The chemical part happens at a junction between two neurons called the synapse.There are about 100 billion neurons in the human brain

. These neurons have many shapes and come in many sizes.

Their job is to allow you to think and behave.For example, solving a math problem in your head and raising your hand in class to answer the teachers question are both activities that are controlled and coordinated by your brain through the behavior of neurons.Neurons are like other body cellsthey have a cell membranea nucleus that contains DNAdeoxyribonucleic acid, a self-replicating material present in nearly all living organisms as the main constituent of chromosomes. It is the carrier of genetic information.the fundamental and distinctive characteristics or qualities of someone or something, especially when regarded as unchangeable.

some working parts of the cell known as organelles, they carry on protein synthesis and energy production.Neurons are different from other body cells:they have an irregular shapethey have specialized extensions called dendrites and axonsthey communicate with each other through the electrochemical processthey have some other specialized structures (such as the synapse) They use chemicals for communication called neurotransmitters.

STRUCTURE OF A NEURON

MAJOR PARTSDENDRITES-Carry nerve impulse towards nerve cellIt has a rough surface, with little bumps called dendritic spines that increase the surface area of the dendrite so it can receive more information from the neighboring neuron.

2.AXON- Carry nerve impulses away from cellThey have smooth surfaces and no spines like dendrites have.3. CELL BODY- also called soma or cyton is responsible for the nutrition and maintenance of the entire cell OTHER PARTS OF THE NEURONa. SCHWANNS CELL-also called neurilemmacell, any of thecellsin the peripheral nervous system that produce the myelin sheath around neuronal axons.Schwann cellsare named after German physiologist TheodorSchwann, who discovered them in the 19th century.b. MYELIN SHEATH-Myelin is a fatty substance that covers some axons. If an axon has myelin, the information it sends can travel faster than if the axon does not have myelin. Myelin is produced by support cells in the nervous system called glia.

c. NODES OF RANVIER- allow passage of the electrical signal through ion channels which helps the transmission very fast.

Synapse- space between the axon of one neuron and the dendrite of another cell (they do not touch)

* Nafly Hussain * Types of Neurons: 1.Sensory neurons 2.Inter neurons 3.Motor NeuronsSensory (or afferent) neurons: send information from sensory receptors (e.g., in skin, eyes, nose, tongue, ears) TOWARD the central nervous system.

Motor (or efferent) neurons: send information AWAY from the central nervous system to muscles or glands.

Inter neurons: send information BETWEEN sensory neurons and motor neurons. Most inter neurons are located in the central nervous system.

* Nafly Hussain *