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THE NERVOUS SYSTEM:

THE NERVOUS SYSTEM Tasting, smelling, seeing, hearing, thinking, dreaming, breathing, heart beating, moving, running, sleeping, laughing, singing, remembering, feeling pain or pleasure... you couldn't do any of these things without your central nervous system! It is made up of your brain, your spinal cord, and an enormous network of nerves that thread throughout your body, it's the control center for your entire body. Your brain uses information it receives from your nerves to coordinate all of your actions and reactions. The nervous system is the part of an animal 's body that controls and coordinates the voluntary and involuntary actions of the animal and transmits signals between different parts of its body.

What are nerves and how do they pass messages?:

What are nerves and how do they pass messages? They're the thin threads of nerve cells, called neurons that run throughout your body. Bundled together, they carry messages back and forth just the way that telephone wires do. Sensory nerves send messages to the brain and generally connect to the brain through the spinal cord inside your backbone. Motor nerves carry messages back from the brain to all the muscles and glands in your body. When a neuron is stimulated by heat, cold, touch, sound vibrations or some other message it begins to actually generate a tiny electrical pulse. This electricity and chemical change travels the full length of the neuron. But when it gets to the end of finger-like points at the end of the neuron, it needs help getting across to the next extended finger. That's where chemicals come in. The electrical pulse in the cells triggers the release of chemicals that carry the pulse to the next cell. And so on .

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Nerve Cells

When movements occur without the action of the brain, they are called reflex actions. Reflex arc : A reflex arc contains two or more neurons over which nerve impulses are conducted from a receptor to the brain or spinal chord through a sensory neurons and then to effectors by ways of motor neurons. Basic components of Reflex arc: 1. Receptor : the molecules that response to a specific change in the internal or external environment by initiating the nerve impulse in the sensory neuron by ways of receptor potential. 2. Sensory neuron: passes the nerve impulse from the receptor to the axonal termination in the CNS. 3. Impulse : in the centre the pulse may be inhibited, transmitted or rerouted. 4.Motor neuron centre: a region in the CNS where on incoming sensory impulse generates an outgoing motor transmits the pulse generated by sensory neuron in the centre of the effector organ will respond. 5.Effector : the organ which responds the motor nerve impulse.:

When movements occur without the action of the brain, they are called reflex actions. Reflex arc : A reflex arc contains two or more neurons over which nerve impulses are conducted from a receptor to the brain or spinal chord through a sensory neurons and then to effectors by ways of motor neurons. Basic components of Reflex arc: 1. Receptor : the molecules that response to a specific change in the internal or external environment by initiating the nerve impulse in the sensory neuron by ways of receptor potential. 2. Sensory neuron: passes the nerve impulse from the receptor to the axonal termination in the CNS. 3. Impulse : in the centre the pulse may be inhibited, transmitted or rerouted. 4.Motor neuron centre: a region in the CNS where on incoming sensory impulse generates an outgoing motor transmits the pulse generated by sensory neuron in the centre of the effector organ will respond. 5.Effector : the organ which responds the motor nerve impulse. Reflex action

Human brain :

Human brain The brain is the center of the nervous system in all vertebrate and most invertebrate. The brain of a vertebrate is the most complex organ of its body. In a typical human the cerebral cortex is estimated to contain 15–33 billion neurons, each connected by synapses  to several thousand other neurons. These neurons communicate with one another by means of axon, which carry trains of signal pulses called action potentials  to distant parts of the brain or body targeting specific recipient cells. the function of the brain is to exert centralized control over the other organs of the body. The brain acts on the rest of the body both by generating patterns of muscle activity and by driving secretion of chemicals called hormones .This centralized control allows rapid and coordinated responses to changes in the environment. Some basic types of responsiveness such as reflexes can be mediated by the spinal cord.

Parts of brain :

Parts of brain 1. The Forebrain The forebrain is the largest and most complex part of the brain. It consists of the cerebrum. The cerebrum contains the information that essentially makes us who we are: our intelligence, memory, personality, emotion, speech, and ability to feel and move. Specific areas of the cerebrum are in charge of processing these different types of information. These are called lobes, and there are four of them: the frontal, parietal, temporal, and occipital. The outer layer of the cerebrum is called the cortex. Information collected by the five senses comes into the brain from the spinal cord to the cortex. This information is then directed to other parts of the nervous system for further processing. In the inner part of the forebrain sits the thalamus, hypothalamus, and pituitary gland. The thalamus carries messages from the sensory organs like the eyes, ears, nose, and fingers to the cortex. 2. The Midbrain The midbrain, located underneath the middle of the forebrain, acts as a master coordinator for all the messages going in and out of the brain to the spinal cord. 3. The Hindbrain The hindbrain sits underneath the back end of the cerebrum, and it consists of the cerebellum, pons, and medulla. The cerebellum is responsible for balance, movement, and coordination.

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Done by : Neha, Meenakshi N, Areeba

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