* The nervous system is an organ system containing a network of specialized cells called neurons that coordinate the actions of an animal and transmit signals between different parts of its body
* The nervous system has 2 subsystems: The central and peripheral nervous system.
* The central nervous system of vertebrates contains the brain, spinal cord, and retina.
* The peripheral nervous system consists of sensory neurons, clusters of neurons called ganglia, and nerves connecting them to each other and to the central nervous system.
* Neurons send signals to other cells as electrochemical waves travelling along thin fibers called axons, which cause chemicals called neurotransmitters to be released at junctions called synapses.
* Sensory neurons are activated by physical stimuli impinging on them, and send signals that inform the central nervous system of the state of the body and the external environment.
* Motor neurons, situated either in the central nervous system or in peripheral ganglia, connect the nervous system to muscles or other effector organs.
* Central neurons, which in vertebrates greatly outnumber the other types, make all of their input and output connections with other neurons.
* Along with neurons, the nervous system contains other specialized cells called glial cells (or simply glia), which provide structural and metabolic support.
* The brain is made of three main parts: the forebrain, midbrain, and hindbrain.
* The forebrain consists of the cerebrum, thalamus, and hypothalamus (part of the limbic system).
* The midbrain consists of the tectum and tegmentum.
* The hindbrain is made of the cerebellum, pons and medulla. Often the midbrain, pons, and medulla are referred to together as the brainstem.
* The cerebrum or cortex is the largest part of the human brain, associated with higher brain function such as thought and action.
* The cerebral cortex is divided into four...
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