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NERVOUS SYSTEM ANATOMY
The nervous system consists of the brain, spinal cord, sensory organs, and all of the nerves that
connect these organs with the rest of the body. Together, these organs are responsible for the
control of the body and communication among its parts. The brain and spinal cord form the
control center known as the central nervous system (CNS), where information is evaluated and
decisions made. The sensory nerves and sense organs of the peripheral nervous system (PNS)
monitor conditions inside and outside of the body and send this information to the CNS. Efferent
nerves in the PNS carry signals from the control center to the muscles, glands, and organs to
regulate their functions.
Nervous Tissue
The majority of the nervous system is tissue made up of two classes of cells: neurons and
neuroglia.
Neurons
Neurons, also known as nerve cells, communicate within the body by transmitting
electrochemical signals. Neurons look quite different from other cells in the body due to the
many long cellular processes that extend from their central cell body. The cell body is the
roughly round part of a neuron that contains the nucleus, mitochondria, and most of the cellular
organelles. Small tree-like structures called dendrites extend from the cell body to pick up
stimuli from the environment, other neurons, or sensory receptor cells. Long transmitting
processes called axons extend from the cell body to send signals onward to other neurons or
effector cells in the body.
There are 3 basic classes of neurons: afferent neurons, efferent neurons, and interneurons.
Afferent neurons. Also known as sensory neurons, afferent neurons transmit sensory
signals to the central nervous system from receptors in the body.
Efferent neurons. Also known as motor neurons, efferent neurons transmit signals from
the central nervous system to effectors in the body such as muscles and glands.
Interneurons. Interneurons form complex networks within the central nervous system to
integrate the information received from afferent neurons and to direct the function of the
body through efferent neurons.
Neuroglia
Neuroglia, also known as glial cells, act as the “helper” cells of the nervous system. Each
neuron in the body is surrounded by anywhere from 6 to 60 neuroglia that protect, feed, and
insulate the neuron. Because neurons are extremely specialized cells that are essential to body
function and almost never reproduce, neuroglia are vital to maintaining a functional nervous
system.
NERVOUS SYSTEM ANATOMY
The nervous system consists of the brain, spinal cord, sensory organs, and all of the nerves that
connect these organs with the rest of the body. Together, these organs are responsible for the
control of the body and communication among its parts. The brain and spinal cord form the
control center known as the central nervous system (CNS), where information is evaluated and
decisions made. The sensory nerves and sense organs of the peripheral nervous system (PNS)
monitor conditions inside and outside of the body and send this information to the CNS. Efferent
nerves in the PNS carry signals from the control center to the muscles, glands, and organs to
regulate their functions.
Nervous Tissue
The majority of the nervous system is tissue made up of two classes of cells: neurons and
neuroglia.
Neurons
Neurons, also known as nerve cells, communicate within the body by transmitting
electrochemical signals. Neurons look quite different from other cells in the body due to the
many long cellular processes that extend from their central cell body. The cell body is the
roughly round part of a neuron that contains the nucleus, mitochondria, and most of the cellular
organelles. Small tree-like structures called dendrites extend from the cell body to pick up
stimuli from the environment, other neurons, or sensory receptor cells. Long transmitting
processes called axons extend from the cell body to send signals onward to other neurons or
effector cells in the body.
There are 3 basic classes of neurons: afferent neurons, efferent neurons, and interneurons.
Afferent neurons. Also known as sensory neurons, afferent neurons transmit sensory
signals to the central nervous system from receptors in the body.
Efferent neurons. Also known as motor neurons, efferent neurons transmit signals from
the central nervous system to effectors in the body such as muscles and glands.
Interneurons. Interneurons form complex networks within the central nervous system to
integrate the information received from afferent neurons and to direct the function of the
body through efferent neurons.
Neuroglia
Neuroglia, also known as glial cells, act as the “helper” cells of the nervous system. Each
neuron in the body is surrounded by anywhere from 6 to 60 neuroglia that protect, feed, and
insulate the neuron. Because neurons are extremely specialized cells that are essential to body
function and almost never reproduce, neuroglia are vital to maintaining a functional nervous
system.
