Which division of the nervous system consists of the brain, spinal cord, and optic nerves?

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Typical Structure of a Nerve Cell
Which division of the autonomic nervous system prepares the body for action in an emergency?
What is the division of the central nervous system?
Which part of the nervous system is outside the brain and spinal cord nervous system which part of the nervous system includes the brain and spinal cord nervous system?

The peripheral nervous system consists of more than 100 billion nerve cells (neurons) that run throughout the body like strings, making connections with the brain, other parts of the body, and often with each other.

Peripheral nerves consist of bundles of nerve fibers. These fibers are wrapped with many layers of tissue composed of a fatty substance called myelin. These layers form the myelin sheath, which speeds the conduction of nerve impulses along the nerve fiber. Nerves conduct impulses at different speeds depending on their diameter and on the amount of myelin around them.

The somatic nervous system
The autonomic nervous system

The autonomic nervous system has two divisions:

Sympathetic division: Its main function is to prepare the body for stressful or emergency situations—for fight or flight.
Parasympathetic division: Its main function is to maintain normal body functions during ordinary situations.

These divisions work together, usually with one activating and the other inhibiting the actions of internal organs. For example, the sympathetic division increases pulse, blood pressure, and breathing rates, and the parasympathetic system decreases each of them.

Typical Structure of a Nerve Cell

A nerve cell (neuron) consists of a large cell body and nerve fibers—one elongated extension (axon) for sending impulses and usually many branches (dendrites) for receiving impulses. The impulses from the axon cross a synapse (the junction between two nerve cells) to the dendrite of another cell.

Each large axon is surrounded by oligodendrocytes in the brain and spinal cord and by Schwann cells in the peripheral nervous system. The membranes of these cells consist of a fat (lipoprotein) called myelin. The membranes are wrapped tightly around the axon, forming a multilayered sheath. This myelin sheath resembles insulation, such as that around an electrical wire. Nerve impulses travel much faster in nerves with a myelin sheath than in those without one.

Nerves that directly connect the brain and the brain stem with the eyes, ears, nose, and throat and with various parts of the head, neck, and trunk are called cranial nerves. There are 12 pairs of them (see Overview of the Cranial Nerves Overview of the Cranial Nerves Twelve pairs of nerves—the cranial nerves—lead directly from the brain to various parts of the head, neck, and trunk. Some of the cranial nerves are involved in the special senses (such as seeing... read more ). Cranial nerves transmit sensory information, including touch, vision, taste, smell, and hearing.

Spinal nerves emerge from the spinal cord through spaces between the vertebrae. Each nerve emerges as two short branches (called spinal nerve roots): one at the front of the spinal cord and one at the back.

Motor nerve root (anterior nerve root): The motor root emerges from the front of the spinal cord. Motor nerve fibers carry commands from the brain and spinal cord to other parts of the body, particularly to skeletal muscles.
Sensory nerve root (posterior nerve root): The sensory root enters the back of the spinal cord. Sensory nerve fibers carry sensory information (about body position, light, touch, temperature, and pain) to the brain from other parts of the body. The sensory nerve fibers in each sensory nerve root carry information from a specific area of the body, called a dermatome (see figure Dermatomes Dermatomes
).

After leaving the spinal cord, the corresponding motor and sensory nerve roots join to form a single spinal nerve.

Some of the spinal nerves form networks of interwoven nerves, called nerve plexuses. In a plexus, nerve fibers from different spinal nerves are sorted and recombined so that all fibers going to or coming from one area of a specific body part are put together into one nerve (see figure Nerve Junction Boxes: The Plexuses Nerve Junction Boxes: The Plexuses

There are two major nerve plexuses:

Brachial plexus: Sorts and recombines nerve fibers traveling to the arms and hands
Lumbosacral plexus: Sorts and recombines nerve fibers going to the legs and feet

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Which division of the autonomic nervous system prepares the body for action in an emergency?

Generally, the sympathetic division does the following: Prepares the body for stressful or emergency situations—fight or flight.

What is the division of the central nervous system?

The central nervous system (defined as the brain and spinal cord) is usually considered to have seven basic parts: the spinal cord, the medulla, the pons, the cerebellum, the midbrain, the diencephalon, and the cerebral hemispheres (Figure 1.10; see also Figure 1.8).

Which part of the nervous system is outside the brain and spinal cord nervous system which part of the nervous system includes the brain and spinal cord nervous system?

The nervous system is made up of the central nervous system and the peripheral nervous system: The central nervous system includes the brain and spinal cord. The peripheral nervous system includes the nerves that run throughout the whole body.