The nervous system is composed of many cells called neurons that have 20 billion varying sizes for different tasks

The nervous system is composed of many cells called neurons that have 20 billion varying sizes for different tasks. Made up of the soma (cell body), dendrites (receptors) and axons (cell signal carriers); the cells can communicate through electrical signals. To connect with other cells, axons have synapses near their ends that release a transmitter substance when there is a pulse. When information is received by a group of muscle cells the electro-chemical reaction can make movement. Similarly, receptor cells accept and convert information like whether something is hot or cold.
Clusters of nerve cells are notated differently depending on their location (nuclei when in the central nervous system, inclosed by bone, and ganglion when in the peripheral nervous system, not enclosed by bone) but the somatic and autonomic have components of both to use sensory neurons to sense and convey info and monitoring neurons to return impulses. Additionally, autonomic is tasked with internal well-being and has two divisions: sympathetic, which prepares for fight-or-flight, and parasympathetic, which resorts back from flight-or-flight.
The cerebrum is the largest part of the brain and split into two hemispheres, each control the opposite side of the body and are further split into lobes. It also has a cerebral cortex as an outer layer that consists of gray matter, made of unmyelinated axons. The thicker layer, white matter, has myelinated axons that project from cortical areas or from thalamus to cortex. The frontal lobe initiates movement of the skeletal muscles, analyze sensory experiences and provides a variety of responses while the parietal lobe responds to stimuli from the skin and muscle receptors. The temporal lobe interprets sensory material, stores memory and has auditory centers which receive information from cochlea in the ear and the occipital lobe controls eye movement by directing and focusing, and correlates the visual with prior experiences.
Diencephalon, which connects the brain stem to cerebral hemispheres, has three parts: the thalamus, which controls sensory motor and expression of emotions; hypothalamus, in charge of the nervous system, temperature regulation and water-electrolyte balance sleep, food intake; and behavior responses and epithalamus which is thought to control neuro endocrine function. The midbrain has medulla oblongata that connect pons and work together to regulate respiratory, heart and blood pressure as well as swallowing or coughing while the cerebellum is involved with balance and the precision of movements. Also, the brainstem automatically controls important actions like breathing.